# gcc

## NAME



           gcc - GNU project C and C++ compiler
    


## SYNOPSIS



           gcc [**-c** |**-S** |**-E**] [**-std=**_standard_]
               [**-g**] [**-pg**] [**-O** _level_]
               [**-W** _warn_...] [**-Wpedantic**]
               [**-I** _dir_...] [**-L** _dir_...]
               [**-D** _macro_[=_defn_]...] [**-U** _macro_]
               [**-f** _option_...] [**-m** _machine-option_...]
               [**-o** _outfile_] [@_file_] _infile_...
    
           Only the most useful options are listed here; see below for the
           remainder.  **g++** accepts mostly the same options as **gcc**.
    


## DESCRIPTION



           When you invoke GCC, it normally does preprocessing, compilation,
           assembly and linking.  The "overall options" allow you to stop
           this process at an intermediate stage.  For example, the **-c** option
           says not to run the linker.  Then the output consists of object
           files output by the assembler.
    
           Other options are passed on to one or more stages of processing.
           Some options control the preprocessor and others the compiler
           itself.  Yet other options control the assembler and linker; most
           of these are not documented here, since you rarely need to use any
           of them.
    
           Most of the command-line options that you can use with GCC are
           useful for C programs; when an option is only useful with another
           language (usually C++), the explanation says so explicitly.  If
           the description for a particular option does not mention a source
           language, you can use that option with all supported languages.
    
           The usual way to run GCC is to run the executable called **gcc** , or
           _machine_**-gcc** when cross-compiling, or _machine_**-gcc-**_version_ to run a
           specific version of GCC.  When you compile C++ programs, you
           should invoke GCC as **g++** instead.
    
           The **gcc** program accepts options and file names as operands.  Many
           options have multi-letter names; therefore multiple single-letter
           options may _not_ be grouped: **-dv** is very different from **-d -v**.
    
           You can mix options and other arguments.  For the most part, the
           order you use doesn't matter.  Order does matter when you use
           several options of the same kind; for example, if you specify **-L**
           more than once, the directories are searched in the order
           specified.  Also, the placement of the **-l** option is significant.
    
           Many options have long names starting with **-f** or with **-W** ---for
           example, **-fmove-loop-invariants** , **-Wformat** and so on.  Most of
           these have both positive and negative forms; the negative form of
           **-ffoo** is **-fno-foo**.  This manual documents only one of these two
           forms, whichever one is not the default.
    
           Some options take one or more arguments typically separated either
           by a space or by the equals sign (**=**) from the option name.  Unless
           documented otherwise, an argument can be either numeric or a
           string.  Numeric arguments must typically be small unsigned
           decimal or hexadecimal integers.  Hexadecimal arguments must begin
           with the **0x** prefix.  Arguments to options that specify a size
           threshold of some sort may be arbitrarily large decimal or
           hexadecimal integers followed by a byte size suffix designating a
           multiple of bytes such as "kB" and "KiB" for kilobyte and
           kibibyte, respectively, "MB" and "MiB" for megabyte and mebibyte,
           "GB" and "GiB" for gigabyte and gigibyte, and so on.  Such
           arguments are designated by _byte-size_ in the following text.
           Refer to the NIST, IEC, and other relevant national and
           international standards for the full listing and explanation of
           the binary and decimal byte size prefixes.
    


## OPTIONS



       **Option Summary**
           Here is a summary of all the options, grouped by type.
           Explanations are in the following sections.
    
           _Overall Options_
               **-c  -S  -E  -o** _file_  **-x** _language_ **-v  -###**
               **--help**[**=**_class_[**,...**]]  **--target-help  --version**
               **-pass-exit-codes  -pipe  -specs=**_file_  **-wrapper @**_file_
               **-ffile-prefix-map=**_old_**=**_new_ **-fplugin=**_file_  **-fplugin-arg-**_name_**=**_arg_
               **-fdump-ada-spec**[**-slim**]  **-fada-spec-parent=**_unit_
               **-fdump-go-spec=**_file_
    
           _C Language Options_
               **-ansi  -std=**_standard_  **-fgnu89-inline**
               **-fpermitted-flt-eval-methods=**_standard_ **-aux-info** _filename_
               **-fallow-parameterless-variadic-functions -fno-asm**
               **-fno-builtin  -fno-builtin-**_function_  **-fgimple -fhosted**
               **-ffreestanding -fopenacc  -fopenacc-dim=**_geom_ **-fopenmp**
               **-fopenmp-simd -fms-extensions  -fplan9-extensions**
               **-fsso-struct=**_endianness_ **-fallow-single-precision**
               **-fcond-mismatch  -flax-vector-conversions -fsigned-bitfields**
               **-fsigned-char -funsigned-bitfields  -funsigned-char**
    
           _C++ Language Options_
               **-fabi-version=**_n_  **-fno-access-control -faligned-new=**_n_
               **-fargs-in-order=**_n_  **-fchar8_t  -fcheck-new -fconstexpr-depth=**_n_
               **-fconstexpr-loop-limit=**_n_ **-fconstexpr-ops-limit=**_n_
               **-fno-elide-constructors -fno-enforce-eh-specs**
               **-fno-gnu-keywords -fno-implicit-templates**
               **-fno-implicit-inline-templates -fno-implement-inlines**
               **-fms-extensions -fnew-inheriting-ctors -fnew-ttp-matching**
               **-fno-nonansi-builtins  -fnothrow-opt  -fno-operator-names**
               **-fno-optional-diags  -fpermissive -fno-pretty-templates -frepo**
               **-fno-rtti  -fsized-deallocation -ftemplate-backtrace-limit=**_n_
               **-ftemplate-depth=**_n_ **-fno-threadsafe-statics  -fuse-cxa-atexit**
               **-fno-weak  -nostdinc++ -fvisibility-inlines-hidden**
               **-fvisibility-ms-compat -fext-numeric-literals -Wabi=**_n_
               **-Wabi-tag  -Wconversion-null  -Wctor-dtor-privacy**
               **-Wdelete-non-virtual-dtor  -Wdeprecated-copy**
               **-Wdeprecated-copy-dtor -Wliteral-suffix -Wmultiple-inheritance**
               **-Wno-init-list-lifetime -Wnamespaces  -Wnarrowing**
               **-Wpessimizing-move  -Wredundant-move -Wnoexcept**
               **-Wnoexcept-type  -Wclass-memaccess -Wnon-virtual-dtor**
               **-Wreorder  -Wregister -Weffc++  -Wstrict-null-sentinel**
               **-Wtemplates -Wno-non-template-friend  -Wold-style-cast**
               **-Woverloaded-virtual  -Wno-pmf-conversions**
               **-Wno-class-conversion  -Wno-terminate -Wsign-promo**
               **-Wvirtual-inheritance**
    
           _Objective-C and Objective-C++ Language Options_
               **-fconstant-string-class=**_class-name_ **-fgnu-runtime**
               **-fnext-runtime -fno-nil-receivers -fobjc-abi-version=**_n_
               **-fobjc-call-cxx-cdtors -fobjc-direct-dispatch**
               **-fobjc-exceptions -fobjc-gc -fobjc-nilcheck -fobjc-std=objc1**
               **-fno-local-ivars**
               **-fivar-visibility=**[**public** |**protected** |**private** |**package**]
               **-freplace-objc-classes -fzero-link -gen-decls**
               **-Wassign-intercept -Wno-protocol  -Wselector**
               **-Wstrict-selector-match -Wundeclared-selector**
    
           _Diagnostic Message Formatting Options_
               **-fmessage-length=**_n_ **-fdiagnostics-show-location=**[**once** |**every-**
               **line**] **-fdiagnostics-color=**[**auto** |**never** |**always**]
               **-fdiagnostics-format=**[**text** |**json**] **-fno-diagnostics-show-option**
               **-fno-diagnostics-show-caret -fno-diagnostics-show-labels**
               **-fno-diagnostics-show-line-numbers**
               **-fdiagnostics-minimum-margin-width=**_width_
               **-fdiagnostics-parseable-fixits  -fdiagnostics-generate-patch**
               **-fdiagnostics-show-template-tree  -fno-elide-type**
               **-fno-show-column**
    
           _Warning Options_
               **-fsyntax-only  -fmax-errors=**_n_  **-Wpedantic -pedantic-errors -w**
               **-Wextra  -Wall  -Waddress  -Waddress-of-packed-member**
               **-Waggregate-return  -Waligned-new -Walloc-zero**
               **-Walloc-size-larger-than=**_byte-size_ **-Walloca**
               **-Walloca-larger-than=**_byte-size_
               **-Wno-aggressive-loop-optimizations  -Warray-bounds**
               **-Warray-bounds=**_n_ **-Wno-attributes  -Wattribute-alias=**_n_
               **-Wbool-compare  -Wbool-operation**
               **-Wno-builtin-declaration-mismatch -Wno-builtin-macro-redefined**
               **-Wc90-c99-compat  -Wc99-c11-compat -Wc11-c2x-compat**
               **-Wc++-compat  -Wc++11-compat  -Wc++14-compat  -Wc++17-compat**
               **-Wcast-align  -Wcast-align=strict  -Wcast-function-type**
               **-Wcast-qual -Wchar-subscripts  -Wcatch-value  -Wcatch-value=**_n_
               **-Wclobbered  -Wcomment  -Wconditionally-supported -Wconversion**
               **-Wcoverage-mismatch  -Wno-cpp  -Wdangling-else  -Wdate-time**
               **-Wdelete-incomplete -Wno-attribute-warning -Wno-deprecated**
               **-Wno-deprecated-declarations  -Wno-designated-init**
               **-Wdisabled-optimization -Wno-discarded-qualifiers**
               **-Wno-discarded-array-qualifiers -Wno-div-by-zero**
               **-Wdouble-promotion -Wduplicated-branches  -Wduplicated-cond**
               **-Wempty-body  -Wenum-compare  -Wno-endif-labels**
               **-Wexpansion-to-defined -Werror  -Werror=*  -Wextra-semi**
               **-Wfatal-errors -Wfloat-equal  -Wformat  -Wformat=2**
               **-Wno-format-contains-nul  -Wno-format-extra-args**
               **-Wformat-nonliteral  -Wformat-overflow=**_n_ **-Wformat-security**
               **-Wformat-signedness  -Wformat-truncation=**_n_ **-Wformat-y2k**
               **-Wframe-address -Wframe-larger-than=**_byte-size_
               **-Wno-free-nonheap-object -Wjump-misses-init -Whsa**
               **-Wif-not-aligned -Wignored-qualifiers  -Wignored-attributes**
               **-Wincompatible-pointer-types -Wimplicit**
               **-Wimplicit-fallthrough  -Wimplicit-fallthrough=**_n_
               **-Wimplicit-function-declaration  -Wimplicit-int -Winit-self**
               **-Winline  -Wno-int-conversion  -Wint-in-bool-context**
               **-Wno-int-to-pointer-cast  -Winvalid-memory-model**
               **-Wno-invalid-offsetof -Winvalid-pch  -Wlarger-than=**_byte-size_
               **-Wlogical-op  -Wlogical-not-parentheses  -Wlong-long -Wmain**
               **-Wmaybe-uninitialized  -Wmemset-elt-size**
               **-Wmemset-transposed-args -Wmisleading-indentation**
               **-Wmissing-attributes  -Wmissing-braces**
               **-Wmissing-field-initializers  -Wmissing-format-attribute**
               **-Wmissing-include-dirs  -Wmissing-noreturn  -Wmissing-profile**
               **-Wno-multichar  -Wmultistatement-macros  -Wnonnull**
               **-Wnonnull-compare -Wnormalized=**[**none** |**id** |**nfc** |**nfkc**]
               **-Wnull-dereference  -Wodr  -Wno-overflow  -Wopenmp-simd**
               **-Woverride-init-side-effects  -Woverlength-strings -Wpacked**
               **-Wpacked-bitfield-compat -Wpacked-not-aligned  -Wpadded**
               **-Wparentheses  -Wno-pedantic-ms-format -Wplacement-new**
               **-Wplacement-new=**_n_ **-Wpointer-arith  -Wpointer-compare**
               **-Wno-pointer-to-int-cast -Wno-pragmas  -Wno-prio-ctor-dtor**
               **-Wredundant-decls -Wrestrict  -Wno-return-local-addr**
               **-Wreturn-type  -Wsequence-point  -Wshadow  -Wno-shadow-ivar**
               **-Wshadow=global,  -Wshadow=local,  -Wshadow=compatible-local**
               **-Wshift-overflow  -Wshift-overflow=**_n_ **-Wshift-count-negative**
               **-Wshift-count-overflow  -Wshift-negative-value -Wsign-compare**
               **-Wsign-conversion  -Wfloat-conversion**
               **-Wno-scalar-storage-order  -Wsizeof-pointer-div**
               **-Wsizeof-pointer-memaccess  -Wsizeof-array-argument**
               **-Wstack-protector  -Wstack-usage=**_byte-size_  **-Wstrict-aliasing**
               **-Wstrict-aliasing=n  -Wstrict-overflow  -Wstrict-overflow=**_n_
               **-Wstringop-overflow=**_n_  **-Wstringop-truncation**
               **-Wsubobject-linkage**
               **-Wsuggest-attribute=**[**pure** |**const** |**noreturn** |**format** |**malloc**]
               **-Wsuggest-final-types   -Wsuggest-final-methods**
               **-Wsuggest-override -Wswitch  -Wswitch-bool  -Wswitch-default**
               **-Wswitch-enum -Wswitch-unreachable  -Wsync-nand**
               **-Wsystem-headers  -Wtautological-compare  -Wtrampolines**
               **-Wtrigraphs -Wtype-limits  -Wundef -Wuninitialized**
               **-Wunknown-pragmas -Wunsuffixed-float-constants  -Wunused**
               **-Wunused-function -Wunused-label  -Wunused-local-typedefs**
               **-Wunused-macros -Wunused-parameter  -Wno-unused-result**
               **-Wunused-value  -Wunused-variable -Wunused-const-variable**
               **-Wunused-const-variable=**_n_ **-Wunused-but-set-parameter**
               **-Wunused-but-set-variable -Wuseless-cast  -Wvariadic-macros**
               **-Wvector-operation-performance -Wvla  -Wvla-larger-than=**_byte-_
               _size_  **-Wvolatile-register-var -Wwrite-strings**
               **-Wzero-as-null-pointer-constant**
    
           _C and Objective-C-only Warning Options_
               **-Wbad-function-cast  -Wmissing-declarations**
               **-Wmissing-parameter-type  -Wmissing-prototypes**
               **-Wnested-externs -Wold-style-declaration**
               **-Wold-style-definition -Wstrict-prototypes  -Wtraditional**
               **-Wtraditional-conversion -Wdeclaration-after-statement**
               **-Wpointer-sign**
    
           _Debugging Options_
               **-g  -g** _level_  **-gdwarf  -gdwarf-**_version_ **-ggdb**
               **-grecord-gcc-switches  -gno-record-gcc-switches -gstabs**
               **-gstabs+  -gstrict-dwarf  -gno-strict-dwarf -gas-loc-support**
               **-gno-as-loc-support -gas-locview-support**
               **-gno-as-locview-support -gcolumn-info  -gno-column-info**
               **-gstatement-frontiers  -gno-statement-frontiers**
               **-gvariable-location-views  -gno-variable-location-views**
               **-ginternal-reset-location-views**
               **-gno-internal-reset-location-views -ginline-points**
               **-gno-inline-points -gvms  -gxcoff  -gxcoff+  -gz**[**=**_type_]
               **-gsplit-dwarf  -gdescribe-dies  -gno-describe-dies**
               **-fdebug-prefix-map=**_old_**=**_new_  **-fdebug-types-section**
               **-fno-eliminate-unused-debug-types -femit-struct-debug-baseonly**
               **-femit-struct-debug-reduced**
               **-femit-struct-debug-detailed**[**=**_spec-list_]
               **-feliminate-unused-debug-symbols  -femit-class-debug-always**
               **-fno-merge-debug-strings  -fno-dwarf2-cfi-asm -fvar-tracking**
               **-fvar-tracking-assignments**
    
           _Optimization Options_
               **-faggressive-loop-optimizations**
               **-falign-functions[=**_n_**[:**_m_**:[**_n2_**[:**_m2_**]]]]**
               **-falign-jumps[=**_n_**[:**_m_**:[**_n2_**[:**_m2_**]]]]**
               **-falign-labels[=**_n_**[:**_m_**:[**_n2_**[:**_m2_**]]]]**
               **-falign-loops[=**_n_**[:**_m_**:[**_n2_**[:**_m2_**]]]] -fassociative-math**
               **-fauto-profile  -fauto-profile[=**_path_**] -fauto-inc-dec**
               **-fbranch-probabilities -fbranch-target-load-optimize**
               **-fbranch-target-load-optimize2 -fbtr-bb-exclusive**
               **-fcaller-saves -fcombine-stack-adjustments  -fconserve-stack**
               **-fcompare-elim  -fcprop-registers  -fcrossjumping**
               **-fcse-follow-jumps  -fcse-skip-blocks  -fcx-fortran-rules**
               **-fcx-limited-range -fdata-sections  -fdce  -fdelayed-branch**
               **-fdelete-null-pointer-checks  -fdevirtualize**
               **-fdevirtualize-speculatively -fdevirtualize-at-ltrans  -fdse**
               **-fearly-inlining  -fipa-sra  -fexpensive-optimizations**
               **-ffat-lto-objects -ffast-math  -ffinite-math-only**
               **-ffloat-store  -fexcess-precision=**_style_ **-fforward-propagate**
               **-ffp-contract=**_style_  **-ffunction-sections -fgcse**
               **-fgcse-after-reload  -fgcse-las  -fgcse-lm**
               **-fgraphite-identity -fgcse-sm  -fhoist-adjacent-loads**
               **-fif-conversion -fif-conversion2  -findirect-inlining**
               **-finline-functions  -finline-functions-called-once**
               **-finline-limit=**_n_ **-finline-small-functions  -fipa-cp**
               **-fipa-cp-clone -fipa-bit-cp  -fipa-vrp  -fipa-pta**
               **-fipa-profile  -fipa-pure-const -fipa-reference**
               **-fipa-reference-addressable -fipa-stack-alignment  -fipa-icf**
               **-fira-algorithm=**_algorithm_ **-flive-patching=**_level_
               **-fira-region=**_region_  **-fira-hoist-pressure -fira-loop-pressure**
               **-fno-ira-share-save-slots -fno-ira-share-spill-slots**
               **-fisolate-erroneous-paths-dereference**
               **-fisolate-erroneous-paths-attribute -fivopts**
               **-fkeep-inline-functions  -fkeep-static-functions**
               **-fkeep-static-consts  -flimit-function-alignment**
               **-flive-range-shrinkage -floop-block  -floop-interchange**
               **-floop-strip-mine -floop-unroll-and-jam  -floop-nest-optimize**
               **-floop-parallelize-all  -flra-remat  -flto**
               **-flto-compression-level -flto-partition=**_alg_
               **-fmerge-all-constants -fmerge-constants  -fmodulo-sched**
               **-fmodulo-sched-allow-regmoves -fmove-loop-invariants**
               **-fno-branch-count-reg -fno-defer-pop**
               **-fno-fp-int-builtin-inexact  -fno-function-cse**
               **-fno-guess-branch-probability  -fno-inline  -fno-math-errno**
               **-fno-peephole -fno-peephole2  -fno-printf-return-value**
               **-fno-sched-interblock -fno-sched-spec  -fno-signed-zeros**
               **-fno-toplevel-reorder  -fno-trapping-math**
               **-fno-zero-initialized-in-bss -fomit-frame-pointer**
               **-foptimize-sibling-calls -fpartial-inlining  -fpeel-loops**
               **-fpredictive-commoning -fprefetch-loop-arrays**
               **-fprofile-correction -fprofile-use  -fprofile-use=**_path_
               **-fprofile-values -fprofile-reorder-functions -freciprocal-math**
               **-free  -frename-registers  -freorder-blocks**
               **-freorder-blocks-algorithm=**_algorithm_
               **-freorder-blocks-and-partition  -freorder-functions**
               **-frerun-cse-after-loop  -freschedule-modulo-scheduled-loops**
               **-frounding-math  -fsave-optimization-record**
               **-fsched2-use-superblocks  -fsched-pressure -fsched-spec-load**
               **-fsched-spec-load-dangerous -fsched-stalled-insns-dep[=**_n_**]**
               **-fsched-stalled-insns[=**_n_**] -fsched-group-heuristic**
               **-fsched-critical-path-heuristic -fsched-spec-insn-heuristic**
               **-fsched-rank-heuristic -fsched-last-insn-heuristic**
               **-fsched-dep-count-heuristic -fschedule-fusion -fschedule-insns**
               **-fschedule-insns2  -fsection-anchors -fselective-scheduling**
               **-fselective-scheduling2 -fsel-sched-pipelining**
               **-fsel-sched-pipelining-outer-loops -fsemantic-interposition**
               **-fshrink-wrap  -fshrink-wrap-separate -fsignaling-nans**
               **-fsingle-precision-constant  -fsplit-ivs-in-unroller**
               **-fsplit-loops -fsplit-paths -fsplit-wide-types  -fssa-backprop**
               **-fssa-phiopt -fstdarg-opt  -fstore-merging  -fstrict-aliasing**
               **-fthread-jumps  -ftracer  -ftree-bit-ccp**
               **-ftree-builtin-call-dce  -ftree-ccp  -ftree-ch**
               **-ftree-coalesce-vars  -ftree-copy-prop  -ftree-dce**
               **-ftree-dominator-opts -ftree-dse  -ftree-forwprop  -ftree-fre**
               **-fcode-hoisting -ftree-loop-if-convert  -ftree-loop-im**
               **-ftree-phiprop  -ftree-loop-distribution**
               **-ftree-loop-distribute-patterns -ftree-loop-ivcanon**
               **-ftree-loop-linear  -ftree-loop-optimize -ftree-loop-vectorize**
               **-ftree-parallelize-loops=**_n_  **-ftree-pre  -ftree-partial-pre**
               **-ftree-pta -ftree-reassoc  -ftree-scev-cprop  -ftree-sink**
               **-ftree-slsr  -ftree-sra -ftree-switch-conversion**
               **-ftree-tail-merge -ftree-ter  -ftree-vectorize  -ftree-vrp**
               **-funconstrained-commons -funit-at-a-time  -funroll-all-loops**
               **-funroll-loops -funsafe-math-optimizations  -funswitch-loops**
               **-fipa-ra  -fvariable-expansion-in-unroller  -fvect-cost-model**
               **-fvpt -fweb  -fwhole-program  -fwpa  -fuse-linker-plugin**
               **--param** _name_**=**_value_ **-O  -O0  -O1  -O2  -O3  -Os  -Ofast  -Og**
    
           _Program Instrumentation Options_
               **-p  -pg  -fprofile-arcs  --coverage  -ftest-coverage**
               **-fprofile-abs-path -fprofile-dir=**_path_  **-fprofile-generate**
               **-fprofile-generate=**_path_ **-fprofile-update=**_method_
               **-fprofile-filter-files=**_regex_ **-fprofile-exclude-files=**_regex_
               **-fsanitize=**_style_  **-fsanitize-recover  -fsanitize-recover=**_style_
               **-fasan-shadow-offset=**_number_  **-fsanitize-sections=**_s1_**,**_s2_**,...**
               **-fsanitize-undefined-trap-on-error  -fbounds-check**
               **-fcf-protection=**[**full** |**branch** |**return** |**none**] **-fstack-protector**
               **-fstack-protector-all  -fstack-protector-strong**
               **-fstack-protector-explicit  -fstack-check**
               **-fstack-limit-register=**_reg_  **-fstack-limit-symbol=**_sym_
               **-fno-stack-limit  -fsplit-stack**
               **-fvtable-verify=**[**std** |**preinit** |**none**] **-fvtv-counts  -fvtv-debug**
               **-finstrument-functions**
               **-finstrument-functions-exclude-function-list=**_sym_**,**_sym_**,...**
               **-finstrument-functions-exclude-file-list=**_file_**,**_file_**,...**
    
           _Preprocessor Options_
               **-A** _question_**=**_answer_ **-A-**_question_[**=**_answer_] **-C  -CC  -D** _macro_[**=**_defn_]
               **-dD  -dI  -dM  -dN  -dU -fdebug-cpp  -fdirectives-only**
               **-fdollars-in-identifiers -fexec-charset=**_charset_
               **-fextended-identifiers -finput-charset=**_charset_
               **-fmacro-prefix-map=**_old_**=**_new_ **-fno-canonical-system-headers**
               **-fpch-deps  -fpch-preprocess -fpreprocessed  -ftabstop=**_width_
               **-ftrack-macro-expansion -fwide-exec-charset=**_charset_
               **-fworking-directory -H  -imacros** _file_  **-include** _file_ **-M  -MD**
               **-MF  -MG  -MM  -MMD  -MP  -MQ  -MT -no-integrated-cpp  -P**
               **-pthread  -remap -traditional  -traditional-cpp  -trigraphs**
               **-U** _macro_  **-undef -Wp,**_option_  **-Xpreprocessor** _option_
    
           _Assembler Options_
               **-Wa,**_option_  **-Xassembler** _option_
    
           _Linker Options_
               _object-file-name_  **-fuse-ld=**_linker_  **-l** _library_ **-nostartfiles**
               **-nodefaultlibs  -nolibc  -nostdlib -e** _entry_  **--entry=**_entry_
               **-pie  -pthread  -r  -rdynamic -s  -static  -static-pie**
               **-static-libgcc  -static-libstdc++ -static-libasan**
               **-static-libtsan  -static-liblsan  -static-libubsan -shared**
               **-shared-libgcc  -symbolic -T** _script_  **-Wl,**_option_  **-Xlinker**
               _option_ **-u** _symbol_  **-z** _keyword_
    
           _Directory Options_
               **-B** _prefix_  **-I** _dir_  **-I- -idirafter** _dir_ **-imacros** _file_  **-imultilib**
               _dir_ **-iplugindir=**_dir_  **-iprefix** _file_ **-iquote** _dir_  **-isysroot** _dir_
               **-isystem** _dir_ **-iwithprefix** _dir_  **-iwithprefixbefore** _dir_ **-L** _dir_
               **-no-canonical-prefixes  --no-sysroot-suffix -nostdinc**
               **-nostdinc++  --sysroot=**_dir_
    
           _Code Generation Options_
               **-fcall-saved-**_reg_  **-fcall-used-**_reg_ **-ffixed-**_reg_  **-fexceptions**
               **-fnon-call-exceptions  -fdelete-dead-exceptions**
               **-funwind-tables -fasynchronous-unwind-tables -fno-gnu-unique**
               **-finhibit-size-directive  -fno-common  -fno-ident**
               **-fpcc-struct-return  -fpic  -fPIC  -fpie  -fPIE  -fno-plt**
               **-fno-jump-tables -frecord-gcc-switches -freg-struct-return**
               **-fshort-enums  -fshort-wchar -fverbose-asm  -fpack-struct[=**_n_**]**
               **-fleading-underscore  -ftls-model=**_model_
               **-fstack-reuse=**_reuse_level_ **-ftrampolines  -ftrapv  -fwrapv**
               **-fvisibility=**[**default** |**internal** |**hidden** |**protected**]
               **-fstrict-volatile-bitfields  -fsync-libcalls**
    
           _Developer Options_
               **-d** _letters_  **-dumpspecs  -dumpmachine  -dumpversion**
               **-dumpfullversion  -fchecking  -fchecking=**_n_  **-fdbg-cnt-list**
               **-fdbg-cnt=**_counter-value-list_ **-fdisable-ipa-**_pass_name_
               **-fdisable-rtl-**_pass_name_ **-fdisable-rtl-**_pass-name_**=**_range-list_
               **-fdisable-tree-**_pass_name_ **-fdisable-tree-**_pass-name_**=**_range-list_
               **-fdump-debug  -fdump-earlydebug -fdump-noaddr**
               **-fdump-unnumbered  -fdump-unnumbered-links**
               **-fdump-final-insns**[**=**_file_] **-fdump-ipa-all  -fdump-ipa-cgraph**
               **-fdump-ipa-inline -fdump-lang-all -fdump-lang-**_switch_
               **-fdump-lang-**_switch_**-**_options_ **-fdump-lang-**_switch_**-**_options_**=**_filename_
               **-fdump-passes -fdump-rtl-**_pass_  **-fdump-rtl-**_pass_**=**_filename_
               **-fdump-statistics -fdump-tree-all -fdump-tree-**_switch_
               **-fdump-tree-**_switch_**-**_options_ **-fdump-tree-**_switch_**-**_options_**=**_filename_
               **-fcompare-debug**[**=**_opts_]  **-fcompare-debug-second**
               **-fenable-**_kind_**-**_pass_ **-fenable-**_kind_**-**_pass_**=**_range-list_
               **-fira-verbose=**_n_ **-flto-report  -flto-report-wpa**
               **-fmem-report-wpa -fmem-report  -fpre-ipa-mem-report**
               **-fpost-ipa-mem-report -fopt-info  -fopt-info-**_options_[**=**_file_]
               **-fprofile-report -frandom-seed=**_string_  **-fsched-verbose=**_n_
               **-fsel-sched-verbose  -fsel-sched-dump-cfg**
               **-fsel-sched-pipelining-verbose -fstats  -fstack-usage**
               **-ftime-report  -ftime-report-details**
               **-fvar-tracking-assignments-toggle  -gtoggle**
               **-print-file-name=**_library_  **-print-libgcc-file-name**
               **-print-multi-directory  -print-multi-lib**
               **-print-multi-os-directory -print-prog-name=**_program_
               **-print-search-dirs  -Q -print-sysroot**
               **-print-sysroot-headers-suffix -save-temps  -save-temps=cwd**
               **-save-temps=obj  -time**[**=**_file_]
    
           _Machine-Dependent Options_
               _AArch64 Options_ **-mabi=**_name_  **-mbig-endian  -mlittle-endian**
               **-mgeneral-regs-only -mcmodel=tiny  -mcmodel=small**
               **-mcmodel=large -mstrict-align  -mno-strict-align**
               **-momit-leaf-frame-pointer -mtls-dialect=desc**
               **-mtls-dialect=traditional -mtls-size=**_size_
               **-mfix-cortex-a53-835769  -mfix-cortex-a53-843419**
               **-mlow-precision-recip-sqrt  -mlow-precision-sqrt**
               **-mlow-precision-div -mpc-relative-literal-loads**
               **-msign-return-address=**_scope_
               **-mbranch-protection=**_none_**|**_standard_**|**_pac-ret_**[+**_leaf_**]|**_bti_
               **-mharden-sls=**_opts_ **-march=**_name_  **-mcpu=**_name_  **-mtune=**_name_
               **-moverride=**_string_  **-mverbose-cost-dump**
               **-mstack-protector-guard=**_guard_
               **-mstack-protector-guard-reg=**_sysreg_
               **-mstack-protector-guard-offset=**_offset_ **-mtrack-speculation**
               **-moutline-atomics**
    
               _Adapteva Epiphany Options_ **-mhalf-reg-file**
               **-mprefer-short-insn-regs -mbranch-cost=**_num_  **-mcmove**
               **-mnops=**_num_  **-msoft-cmpsf -msplit-lohi  -mpost-inc**
               **-mpost-modify  -mstack-offset=**_num_ **-mround-nearest**
               **-mlong-calls  -mshort-calls  -msmall16 -mfp-mode=**_mode_
               **-mvect-double  -max-vect-align=**_num_ **-msplit-vecmove-early**
               **-m1reg-**_reg_
    
               _AMD GCN Options_ **-march=**_gpu_ **-mtune=**_gpu_ **-mstack-size=**_bytes_
    
               _ARC Options_ **-mbarrel-shifter  -mjli-always -mcpu=**_cpu_  **-mA6**
               **-mARC600  -mA7  -mARC700 -mdpfp  -mdpfp-compact  -mdpfp-fast**
               **-mno-dpfp-lrsr -mea  -mno-mpy  -mmul32x16  -mmul64  -matomic**
               **-mnorm  -mspfp  -mspfp-compact  -mspfp-fast  -msimd**
               **-msoft-float  -mswap -mcrc  -mdsp-packa  -mdvbf  -mlock**
               **-mmac-d16  -mmac-24  -mrtsc  -mswape -mtelephony  -mxy**
               **-misize  -mannotate-align  -marclinux  -marclinux_prof**
               **-mlong-calls  -mmedium-calls  -msdata  -mirq-ctrl-saved**
               **-mrgf-banked-regs  -mlpc-width=**_width_  **-G** _num_ **-mvolatile-cache**
               **-mtp-regno=**_regno_ **-malign-call  -mauto-modify-reg**
               **-mbbit-peephole  -mno-brcc -mcase-vector-pcrel**
               **-mcompact-casesi  -mno-cond-exec  -mearly-cbranchsi**
               **-mexpand-adddi  -mindexed-loads  -mlra  -mlra-priority-none**
               **-mlra-priority-compact mlra-priority-noncompact  -mmillicode**
               **-mmixed-code  -mq-class  -mRcq  -mRcw  -msize-level=**_level_
               **-mtune=**_cpu_  **-mmultcost=**_num_  **-mcode-density-frame**
               **-munalign-prob-threshold=**_probability_  **-mmpy-option=**_multo_
               **-mdiv-rem  -mcode-density  -mll64  -mfpu=**_fpu_  **-mrf16**
               **-mbranch-index**
    
               _ARM Options_ **-mapcs-frame  -mno-apcs-frame -mabi=**_name_
               **-mapcs-stack-check  -mno-apcs-stack-check -mapcs-reentrant**
               **-mno-apcs-reentrant -mgeneral-regs-only -msched-prolog**
               **-mno-sched-prolog -mlittle-endian  -mbig-endian -mbe8  -mbe32**
               **-mfloat-abi=**_name_ **-mfp16-format=**_name_ **-mthumb-interwork**
               **-mno-thumb-interwork -mcpu=**_name_  **-march=**_name_  **-mfpu=**_name_
               **-mtune=**_name_  **-mprint-tune-info -mstructure-size-boundary=**_n_
               **-mabort-on-noreturn -mlong-calls  -mno-long-calls**
               **-msingle-pic-base  -mno-single-pic-base -mpic-register=**_reg_
               **-mnop-fun-dllimport -mpoke-function-name -mthumb  -marm**
               **-mflip-thumb -mtpcs-frame  -mtpcs-leaf-frame**
               **-mcaller-super-interworking  -mcallee-super-interworking**
               **-mtp=**_name_  **-mtls-dialect=**_dialect_ **-mword-relocations**
               **-mfix-cortex-m3-ldrd -munaligned-access -mneon-for-64bits**
               **-mslow-flash-data -masm-syntax-unified -mrestrict-it**
               **-mverbose-cost-dump -mpure-code -mcmse**
    
               _AVR Options_ **-mmcu=**_mcu_  **-mabsdata  -maccumulate-args**
               **-mbranch-cost=**_cost_ **-mcall-prologues  -mgas-isr-prologues**
               **-mint8 -mn_flash=**_size_  **-mno-interrupts -mmain-is-OS_task**
               **-mrelax  -mrmw  -mstrict-X  -mtiny-stack**
               **-mfract-convert-truncate -mshort-calls -nodevicelib**
               **-nodevicespecs -Waddr-space-convert  -Wmisspelled-isr**
    
               _Blackfin Options_ **-mcpu=**_cpu_[**-**_sirevision_] **-msim**
               **-momit-leaf-frame-pointer  -mno-omit-leaf-frame-pointer**
               **-mspecld-anomaly  -mno-specld-anomaly  -mcsync-anomaly**
               **-mno-csync-anomaly -mlow-64k  -mno-low64k  -mstack-check-l1**
               **-mid-shared-library -mno-id-shared-library**
               **-mshared-library-id=**_n_ **-mleaf-id-shared-library**
               **-mno-leaf-id-shared-library -msep-data  -mno-sep-data**
               **-mlong-calls  -mno-long-calls -mfast-fp  -minline-plt**
               **-mmulticore  -mcorea  -mcoreb  -msdram -micplb**
    
               _C6X Options_ **-mbig-endian  -mlittle-endian  -march=**_cpu_ **-msim**
               **-msdata=**_sdata-type_
    
               _CRIS Options_ **-mcpu=**_cpu_  **-march=**_cpu_  **-mtune=**_cpu_
               **-mmax-stack-frame=**_n_  **-melinux-stacksize=**_n_ **-metrax4  -metrax100**
               **-mpdebug  -mcc-init  -mno-side-effects -mstack-align**
               **-mdata-align  -mconst-align -m32-bit  -m16-bit  -m8-bit**
               **-mno-prologue-epilogue  -mno-gotplt -melf  -maout  -melinux**
               **-mlinux  -sim  -sim2 -mmul-bug-workaround**
               **-mno-mul-bug-workaround**
    
               _CR16 Options_ **-mmac -mcr16cplus  -mcr16c -msim  -mint32**
               **-mbit-ops -mdata-model=**_model_
    
               _C-SKY Options_ **-march=**_arch_  **-mcpu=**_cpu_ **-mbig-endian  -EB**
               **-mlittle-endian  -EL -mhard-float  -msoft-float  -mfpu=**_fpu_
               **-mdouble-float  -mfdivdu -melrw  -mistack  -mmp  -mcp  -mcache**
               **-msecurity  -mtrust -mdsp  -medsp  -mvdsp -mdiv  -msmart**
               **-mhigh-registers  -manchor -mpushpop  -mmultiple-stld**
               **-mconstpool  -mstack-size  -mccrt -mbranch-cost=**_n_  **-mcse-cc**
               **-msched-prolog**
    
               _Darwin Options_ **-all_load  -allowable_client  -arch**
               **-arch_errors_fatal -arch_only  -bind_at_load  -bundle**
               **-bundle_loader -client_name  -compatibility_version**
               **-current_version -dead_strip -dependency-file  -dylib_file**
               **-dylinker_install_name -dynamic  -dynamiclib**
               **-exported_symbols_list -filelist  -flat_namespace**
               **-force_cpusubtype_ALL -force_flat_namespace**
               **-headerpad_max_install_names -iframework -image_base  -init**
               **-install_name  -keep_private_externs -multi_module**
               **-multiply_defined  -multiply_defined_unused -noall_load**
               **-no_dead_strip_inits_and_terms -nofixprebinding  -nomultidefs**
               **-noprebind  -noseglinkedit -pagezero_size  -prebind**
               **-prebind_all_twolevel_modules -private_bundle**
               **-read_only_relocs  -sectalign -sectobjectsymbols  -whyload**
               **-seg1addr -sectcreate  -sectobjectsymbols  -sectorder -segaddr**
               **-segs_read_only_addr  -segs_read_write_addr -seg_addr_table**
               **-seg_addr_table_filename  -seglinkedit -segprot**
               **-segs_read_only_addr  -segs_read_write_addr -single_module**
               **-static  -sub_library  -sub_umbrella -twolevel_namespace**
               **-umbrella  -undefined -unexported_symbols_list**
               **-weak_reference_mismatches -whatsloaded  -F  -gused  -gfull**
               **-mmacosx-version-min=**_version_ **-mkernel  -mone-byte-bool**
    
               _DEC Alpha Options_ **-mno-fp-regs  -msoft-float -mieee**
               **-mieee-with-inexact  -mieee-conformant -mfp-trap-mode=**_mode_
               **-mfp-rounding-mode=**_mode_ **-mtrap-precision=**_mode_
               **-mbuild-constants -mcpu=**_cpu-type_  **-mtune=**_cpu-type_ **-mbwx  -mmax**
               **-mfix  -mcix -mfloat-vax  -mfloat-ieee -mexplicit-relocs**
               **-msmall-data  -mlarge-data -msmall-text  -mlarge-text**
               **-mmemory-latency=**_time_
    
               _FR30 Options_ **-msmall-model  -mno-lsim**
    
               _FT32 Options_ **-msim  -mlra  -mnodiv  -mft32b  -mcompress**
               **-mnopm**
    
               _FRV Options_ **-mgpr-32  -mgpr-64  -mfpr-32  -mfpr-64**
               **-mhard-float  -msoft-float -malloc-cc  -mfixed-cc  -mdword**
               **-mno-dword -mdouble  -mno-double -mmedia  -mno-media  -mmuladd**
               **-mno-muladd -mfdpic  -minline-plt  -mgprel-ro**
               **-multilib-library-pic -mlinked-fp  -mlong-calls**
               **-malign-labels -mlibrary-pic  -macc-4  -macc-8 -mpack**
               **-mno-pack  -mno-eflags  -mcond-move  -mno-cond-move**
               **-moptimize-membar  -mno-optimize-membar -mscc  -mno-scc**
               **-mcond-exec  -mno-cond-exec -mvliw-branch  -mno-vliw-branch**
               **-mmulti-cond-exec  -mno-multi-cond-exec  -mnested-cond-exec**
               **-mno-nested-cond-exec  -mtomcat-stats -mTLS  -mtls -mcpu=**_cpu_
    
               _GNU/Linux Options_ **-mglibc  -muclibc  -mmusl  -mbionic**
               **-mandroid -tno-android-cc  -tno-android-ld**
    
               _H8/300 Options_ **-mrelax  -mh  -ms  -mn  -mexr  -mno-exr**
               **-mint32  -malign-300**
    
               _HPPA Options_ **-march=**_architecture-type_ **-mcaller-copies**
               **-mdisable-fpregs  -mdisable-indexing -mfast-indirect-calls**
               **-mgas  -mgnu-ld   -mhp-ld -mfixed-range=**_register-range_
               **-mjump-in-delay  -mlinker-opt  -mlong-calls -mlong-load-store**
               **-mno-disable-fpregs -mno-disable-indexing**
               **-mno-fast-indirect-calls  -mno-gas -mno-jump-in-delay**
               **-mno-long-load-store -mno-portable-runtime  -mno-soft-float**
               **-mno-space-regs  -msoft-float  -mpa-risc-1-0 -mpa-risc-1-1**
               **-mpa-risc-2-0  -mportable-runtime -mschedule=**_cpu-type_
               **-mspace-regs  -msio  -mwsio -munix=**_unix-std_  **-nolibdld**
               **-static  -threads**
    
               _IA-64 Options_ **-mbig-endian  -mlittle-endian  -mgnu-as**
               **-mgnu-ld  -mno-pic -mvolatile-asm-stop  -mregister-names**
               **-msdata  -mno-sdata -mconstant-gp  -mauto-pic  -mfused-madd**
               **-minline-float-divide-min-latency**
               **-minline-float-divide-max-throughput -mno-inline-float-divide**
               **-minline-int-divide-min-latency**
               **-minline-int-divide-max-throughput -mno-inline-int-divide**
               **-minline-sqrt-min-latency  -minline-sqrt-max-throughput**
               **-mno-inline-sqrt -mdwarf2-asm  -mearly-stop-bits**
               **-mfixed-range=**_register-range_  **-mtls-size=**_tls-size_ **-mtune=**_cpu-_
               _type_  **-milp32  -mlp64 -msched-br-data-spec**
               **-msched-ar-data-spec  -msched-control-spec**
               **-msched-br-in-data-spec  -msched-ar-in-data-spec**
               **-msched-in-control-spec -msched-spec-ldc**
               **-msched-spec-control-ldc -msched-prefer-non-data-spec-insns**
               **-msched-prefer-non-control-spec-insns**
               **-msched-stop-bits-after-every-cycle**
               **-msched-count-spec-in-critical-path**
               **-msel-sched-dont-check-control-spec**
               **-msched-fp-mem-deps-zero-cost**
               **-msched-max-memory-insns-hard-limit**
               **-msched-max-memory-insns=**_max-insns_
    
               _LM32 Options_ **-mbarrel-shift-enabled  -mdivide-enabled**
               **-mmultiply-enabled -msign-extend-enabled  -muser-enabled**
    
               _M32R/D Options_ **-m32r2  -m32rx  -m32r -mdebug -malign-loops**
               **-mno-align-loops -missue-rate=**_number_ **-mbranch-cost=**_number_
               **-mmodel=**_code-size-model-type_ **-msdata=**_sdata-type_
               **-mno-flush-func  -mflush-func=**_name_ **-mno-flush-trap**
               **-mflush-trap=**_number_ **-G** _num_
    
               _M32C Options_ **-mcpu=**_cpu_  **-msim  -memregs=**_number_
    
               _M680x0 Options_ **-march=**_arch_  **-mcpu=**_cpu_  **-mtune=**_tune_ **-m68000**
               **-m68020  -m68020-40  -m68020-60  -m68030  -m68040 -m68060**
               **-mcpu32  -m5200  -m5206e  -m528x  -m5307  -m5407 -mcfv4e**
               **-mbitfield  -mno-bitfield  -mc68000  -mc68020 -mnobitfield**
               **-mrtd  -mno-rtd  -mdiv  -mno-div  -mshort -mno-short**
               **-mhard-float  -m68881  -msoft-float  -mpcrel -malign-int**
               **-mstrict-align  -msep-data  -mno-sep-data**
               **-mshared-library-id=n  -mid-shared-library**
               **-mno-id-shared-library -mxgot  -mno-xgot**
               **-mlong-jump-table-offsets**
    
               _MCore Options_ **-mhardlit  -mno-hardlit  -mdiv  -mno-div**
               **-mrelax-immediates -mno-relax-immediates  -mwide-bitfields**
               **-mno-wide-bitfields -m4byte-functions  -mno-4byte-functions**
               **-mcallgraph-data -mno-callgraph-data  -mslow-bytes**
               **-mno-slow-bytes  -mno-lsim -mlittle-endian  -mbig-endian**
               **-m210  -m340  -mstack-increment**
    
               _MeP Options_ **-mabsdiff  -mall-opts  -maverage  -mbased=**_n_
               **-mbitops -mc=**_n_  **-mclip  -mconfig=**_name_  **-mcop  -mcop32  -mcop64**
               **-mivc2 -mdc  -mdiv  -meb  -mel  -mio-volatile  -ml  -mleadz**
               **-mm  -mminmax -mmult  -mno-opts  -mrepeat  -ms  -msatur**
               **-msdram  -msim  -msimnovec  -mtf -mtiny=**_n_
    
               _MicroBlaze Options_ **-msoft-float  -mhard-float  -msmall-divides**
               **-mcpu=**_cpu_ **-mmemcpy  -mxl-soft-mul  -mxl-soft-div**
               **-mxl-barrel-shift -mxl-pattern-compare  -mxl-stack-check**
               **-mxl-gp-opt  -mno-clearbss -mxl-multiply-high**
               **-mxl-float-convert  -mxl-float-sqrt -mbig-endian**
               **-mlittle-endian  -mxl-reorder  -mxl-mode-**_app-model_
               **-mpic-data-is-text-relative**
    
               _MIPS Options_ **-EL  -EB  -march=**_arch_  **-mtune=**_arch_ **-mips1  -mips2**
               **-mips3  -mips4  -mips32  -mips32r2  -mips32r3  -mips32r5**
               **-mips32r6  -mips64  -mips64r2  -mips64r3  -mips64r5  -mips64r6**
               **-mips16  -mno-mips16  -mflip-mips16 -minterlink-compressed**
               **-mno-interlink-compressed -minterlink-mips16**
               **-mno-interlink-mips16 -mabi=**_abi_  **-mabicalls  -mno-abicalls**
               **-mshared  -mno-shared  -mplt  -mno-plt  -mxgot  -mno-xgot**
               **-mgp32  -mgp64  -mfp32  -mfpxx  -mfp64  -mhard-float**
               **-msoft-float -mno-float  -msingle-float  -mdouble-float**
               **-modd-spreg  -mno-odd-spreg -mabs=**_mode_  **-mnan=**_encoding_ **-mdsp**
               **-mno-dsp  -mdspr2  -mno-dspr2 -mmcu  -mmno-mcu -meva  -mno-eva**
               **-mvirt  -mno-virt -mxpa  -mno-xpa -mcrc  -mno-crc -mginv**
               **-mno-ginv -mmicromips  -mno-micromips -mmsa  -mno-msa**
               **-mloongson-mmi  -mno-loongson-mmi -mloongson-ext**
               **-mno-loongson-ext -mloongson-ext2  -mno-loongson-ext2**
               **-mfpu=**_fpu-type_ **-msmartmips  -mno-smartmips -mpaired-single**
               **-mno-paired-single  -mdmx  -mno-mdmx -mips3d  -mno-mips3d**
               **-mmt  -mno-mt  -mllsc  -mno-llsc -mlong64  -mlong32  -msym32**
               **-mno-sym32 -G** _num_  **-mlocal-sdata  -mno-local-sdata**
               **-mextern-sdata  -mno-extern-sdata  -mgpopt  -mno-gopt**
               **-membedded-data  -mno-embedded-data -muninit-const-in-rodata**
               **-mno-uninit-const-in-rodata -mcode-readable=**_setting_
               **-msplit-addresses  -mno-split-addresses -mexplicit-relocs**
               **-mno-explicit-relocs -mcheck-zero-division**
               **-mno-check-zero-division -mdivide-traps  -mdivide-breaks**
               **-mload-store-pairs  -mno-load-store-pairs -mmemcpy**
               **-mno-memcpy  -mlong-calls  -mno-long-calls -mmad  -mno-mad**
               **-mimadd  -mno-imadd  -mfused-madd  -mno-fused-madd  -nocpp**
               **-mfix-24k  -mno-fix-24k -mfix-r4000  -mno-fix-r4000**
               **-mfix-r4400  -mno-fix-r4400 -mfix-r5900  -mno-fix-r5900**
               **-mfix-r10000  -mno-fix-r10000  -mfix-rm7000  -mno-fix-rm7000**
               **-mfix-vr4120  -mno-fix-vr4120 -mfix-vr4130  -mno-fix-vr4130**
               **-mfix-sb1  -mno-fix-sb1 -mflush-func=**_func_  **-mno-flush-func**
               **-mbranch-cost=**_num_  **-mbranch-likely  -mno-branch-likely**
               **-mcompact-branches=**_policy_ **-mfp-exceptions  -mno-fp-exceptions**
               **-mvr4130-align  -mno-vr4130-align  -msynci  -mno-synci**
               **-mlxc1-sxc1  -mno-lxc1-sxc1  -mmadd4  -mno-madd4**
               **-mrelax-pic-calls  -mno-relax-pic-calls  -mmcount-ra-address**
               **-mframe-header-opt  -mno-frame-header-opt**
    
               _MMIX Options_ **-mlibfuncs  -mno-libfuncs  -mepsilon**
               **-mno-epsilon  -mabi=gnu -mabi=mmixware  -mzero-extend**
               **-mknuthdiv  -mtoplevel-symbols -melf  -mbranch-predict**
               **-mno-branch-predict  -mbase-addresses -mno-base-addresses**
               **-msingle-exit  -mno-single-exit**
    
               _MN10300 Options_ **-mmult-bug  -mno-mult-bug -mno-am33  -mam33**
               **-mam33-2  -mam34 -mtune=**_cpu-type_ **-mreturn-pointer-on-d0**
               **-mno-crt0  -mrelax  -mliw  -msetlb**
    
               _Moxie Options_ **-meb  -mel  -mmul.x  -mno-crt0**
    
               _MSP430 Options_ **-msim  -masm-hex  -mmcu=  -mcpu=  -mlarge**
               **-msmall  -mrelax -mwarn-mcu -mcode-region=  -mdata-region=**
               **-msilicon-errata=  -msilicon-errata-warn= -mhwmult=  -minrt**
    
               _NDS32 Options_ **-mbig-endian  -mlittle-endian -mreduced-regs**
               **-mfull-regs -mcmov  -mno-cmov -mext-perf  -mno-ext-perf**
               **-mext-perf2  -mno-ext-perf2 -mext-string  -mno-ext-string**
               **-mv3push  -mno-v3push -m16bit  -mno-16bit**
               **-misr-vector-size=**_num_ **-mcache-block-size=**_num_ **-march=**_arch_
               **-mcmodel=**_code-model_ **-mctor-dtor  -mrelax**
    
               _Nios II Options_ **-G** _num_  **-mgpopt=**_option_  **-mgpopt  -mno-gpopt**
               **-mgprel-sec=**_regexp_  **-mr0rel-sec=**_regexp_ **-mel  -meb**
               **-mno-bypass-cache  -mbypass-cache -mno-cache-volatile**
               **-mcache-volatile -mno-fast-sw-div  -mfast-sw-div -mhw-mul**
               **-mno-hw-mul  -mhw-mulx  -mno-hw-mulx  -mno-hw-div  -mhw-div**
               **-mcustom-**_insn_**=**_N_  **-mno-custom-**_insn_ **-mcustom-fpu-cfg=**_name_ **-mhal**
               **-msmallc  -msys-crt0=**_name_  **-msys-lib=**_name_ **-march=**_arch_  **-mbmx**
               **-mno-bmx  -mcdx  -mno-cdx**
    
               _Nvidia PTX Options_ **-m32  -m64  -mmainkernel  -moptimize**
    
               _OpenRISC Options_ **-mboard=**_name_  **-mnewlib  -mhard-mul**
               **-mhard-div -msoft-mul  -msoft-div -mcmov  -mror  -msext**
               **-msfimm  -mshftimm**
    
               _PDP-11 Options_ **-mfpu  -msoft-float  -mac0  -mno-ac0  -m40**
               **-m45  -m10 -mint32  -mno-int16  -mint16  -mno-int32 -msplit**
               **-munix-asm  -mdec-asm  -mgnu-asm  -mlra**
    
               _picoChip Options_ **-mae=**_ae_type_  **-mvliw-lookahead=**_N_
               **-msymbol-as-address  -mno-inefficient-warnings**
    
               _PowerPC Options_ See RS/6000 and PowerPC Options.
    
               _RISC-V Options_ **-mbranch-cost=**_N-instruction_ **-mplt  -mno-plt**
               **-mabi=**_ABI-string_ **-mfdiv  -mno-fdiv -mdiv  -mno-div -march=**_ISA-_
               _string_ **-mtune=**_processor-string_ **-mpreferred-stack-boundary=**_num_
               **-msmall-data-limit=**_N-bytes_ **-msave-restore  -mno-save-restore**
               **-mstrict-align  -mno-strict-align -mcmodel=medlow**
               **-mcmodel=medany -mexplicit-relocs  -mno-explicit-relocs**
               **-mrelax  -mno-relax -mriscv-attribute  -mmo-riscv-attribute**
    
               _RL78 Options_ **-msim  -mmul=none  -mmul=g13  -mmul=g14**
               **-mallregs -mcpu=g10  -mcpu=g13  -mcpu=g14  -mg10  -mg13  -mg14**
               **-m64bit-doubles  -m32bit-doubles  -msave-mduc-in-interrupts**
    
               _RS/6000 and PowerPC Options_ **-mcpu=**_cpu-type_ **-mtune=**_cpu-type_
               **-mcmodel=**_code-model_ **-mpowerpc64 -maltivec  -mno-altivec**
               **-mpowerpc-gpopt  -mno-powerpc-gpopt -mpowerpc-gfxopt**
               **-mno-powerpc-gfxopt -mmfcrf  -mno-mfcrf  -mpopcntb**
               **-mno-popcntb  -mpopcntd  -mno-popcntd -mfprnd  -mno-fprnd**
               **-mcmpb  -mno-cmpb  -mmfpgpr  -mno-mfpgpr  -mhard-dfp**
               **-mno-hard-dfp -mfull-toc   -mminimal-toc  -mno-fp-in-toc**
               **-mno-sum-in-toc -m64  -m32  -mxl-compat  -mno-xl-compat  -mpe**
               **-malign-power  -malign-natural -msoft-float  -mhard-float**
               **-mmultiple  -mno-multiple -mupdate  -mno-update**
               **-mavoid-indexed-addresses  -mno-avoid-indexed-addresses**
               **-mfused-madd  -mno-fused-madd  -mbit-align  -mno-bit-align**
               **-mstrict-align  -mno-strict-align  -mrelocatable**
               **-mno-relocatable  -mrelocatable-lib  -mno-relocatable-lib**
               **-mtoc  -mno-toc  -mlittle  -mlittle-endian  -mbig**
               **-mbig-endian -mdynamic-no-pic  -mswdiv  -msingle-pic-base**
               **-mprioritize-restricted-insns=**_priority_
               **-msched-costly-dep=**_dependence_type_ **-minsert-sched-nops=**_scheme_
               **-mcall-aixdesc  -mcall-eabi  -mcall-freebsd -mcall-linux**
               **-mcall-netbsd  -mcall-openbsd -mcall-sysv  -mcall-sysv-eabi**
               **-mcall-sysv-noeabi -mtraceback=**_traceback_type_
               **-maix-struct-return  -msvr4-struct-return -mabi=**_abi-type_
               **-msecure-plt  -mbss-plt -mlongcall  -mno-longcall  -mpltseq**
               **-mno-pltseq -mblock-move-inline-limit=**_num_
               **-mblock-compare-inline-limit=**_num_
               **-mblock-compare-inline-loop-limit=**_num_
               **-mstring-compare-inline-limit=**_num_ **-misel  -mno-isel -mvrsave**
               **-mno-vrsave -mmulhw  -mno-mulhw -mdlmzb  -mno-dlmzb**
               **-mprototype  -mno-prototype -msim  -mmvme  -mads**
               **-myellowknife  -memb  -msdata -msdata=**_opt_  **-mreadonly-in-sdata**
               **-mvxworks  -G** _num_ **-mrecip  -mrecip=**_opt_  **-mno-recip**
               **-mrecip-precision -mno-recip-precision -mveclibabi=**_type_
               **-mfriz  -mno-friz -mpointers-to-nested-functions**
               **-mno-pointers-to-nested-functions -msave-toc-indirect**
               **-mno-save-toc-indirect -mpower8-fusion  -mno-mpower8-fusion**
               **-mpower8-vector  -mno-power8-vector -mcrypto  -mno-crypto**
               **-mhtm  -mno-htm -mquad-memory  -mno-quad-memory**
               **-mquad-memory-atomic  -mno-quad-memory-atomic**
               **-mcompat-align-parm  -mno-compat-align-parm -mfloat128**
               **-mno-float128  -mfloat128-hardware  -mno-float128-hardware**
               **-mgnu-attribute  -mno-gnu-attribute**
               **-mstack-protector-guard=**_guard_ **-mstack-protector-guard-reg=**_reg_
               **-mstack-protector-guard-offset=**_offset_
    
               _RX Options_ **-m64bit-doubles  -m32bit-doubles  -fpu  -nofpu**
               **-mcpu= -mbig-endian-data  -mlittle-endian-data -msmall-data**
               **-msim  -mno-sim -mas100-syntax  -mno-as100-syntax -mrelax**
               **-mmax-constant-size= -mint-register= -mpid**
               **-mallow-string-insns  -mno-allow-string-insns -mjsr**
               **-mno-warn-multiple-fast-interrupts -msave-acc-in-interrupts**
    
               _S/390 and zSeries Options_ **-mtune=**_cpu-type_  **-march=**_cpu-type_
               **-mhard-float  -msoft-float  -mhard-dfp  -mno-hard-dfp**
               **-mlong-double-64  -mlong-double-128 -mbackchain**
               **-mno-backchain  -mpacked-stack  -mno-packed-stack -msmall-exec**
               **-mno-small-exec  -mmvcle  -mno-mvcle -m64  -m31  -mdebug**
               **-mno-debug  -mesa  -mzarch -mhtm  -mvx  -mzvector -mtpf-trace**
               **-mno-tpf-trace  -mfused-madd  -mno-fused-madd -mwarn-framesize**
               **-mwarn-dynamicstack  -mstack-size  -mstack-guard**
               **-mhotpatch=**_halfwords_**,**_halfwords_
    
               _Score Options_ **-meb  -mel -mnhwloop -muls -mmac -mscore5**
               **-mscore5u  -mscore7  -mscore7d**
    
               _SH Options_ **-m1  -m2  -m2e -m2a-nofpu  -m2a-single-only**
               **-m2a-single  -m2a -m3  -m3e -m4-nofpu  -m4-single-only**
               **-m4-single  -m4 -m4a-nofpu  -m4a-single-only  -m4a-single**
               **-m4a  -m4al -mb  -ml  -mdalign  -mrelax -mbigtable  -mfmovd**
               **-mrenesas  -mno-renesas  -mnomacsave -mieee  -mno-ieee**
               **-mbitops  -misize  -minline-ic_invalidate  -mpadstruct**
               **-mprefergot  -musermode  -multcost=**_number_  **-mdiv=**_strategy_
               **-mdivsi3_libfunc=**_name_  **-mfixed-range=**_register-range_
               **-maccumulate-outgoing-args -matomic-model=**_atomic-model_
               **-mbranch-cost=**_num_  **-mzdcbranch  -mno-zdcbranch**
               **-mcbranch-force-delay-slot -mfused-madd  -mno-fused-madd**
               **-mfsca  -mno-fsca  -mfsrra  -mno-fsrra -mpretend-cmove  -mtas**
    
               _Solaris 2 Options_ **-mclear-hwcap  -mno-clear-hwcap**
               **-mimpure-text  -mno-impure-text -pthreads**
    
               _SPARC Options_ **-mcpu=**_cpu-type_ **-mtune=**_cpu-type_ **-mcmodel=**_code-_
               _model_ **-mmemory-model=**_mem-model_ **-m32  -m64  -mapp-regs**
               **-mno-app-regs -mfaster-structs  -mno-faster-structs  -mflat**
               **-mno-flat -mfpu  -mno-fpu  -mhard-float  -msoft-float**
               **-mhard-quad-float  -msoft-quad-float -mstack-bias**
               **-mno-stack-bias -mstd-struct-return  -mno-std-struct-return**
               **-munaligned-doubles  -mno-unaligned-doubles -muser-mode**
               **-mno-user-mode -mv8plus  -mno-v8plus  -mvis  -mno-vis -mvis2**
               **-mno-vis2  -mvis3  -mno-vis3 -mvis4  -mno-vis4  -mvis4b**
               **-mno-vis4b -mcbcond  -mno-cbcond  -mfmaf  -mno-fmaf  -mfsmuld**
               **-mno-fsmuld -mpopc  -mno-popc  -msubxc  -mno-subxc**
               **-mfix-at697f  -mfix-ut699  -mfix-ut700  -mfix-gr712rc -mlra**
               **-mno-lra**
    
               _SPU Options_ **-mwarn-reloc  -merror-reloc -msafe-dma**
               **-munsafe-dma -mbranch-hints -msmall-mem  -mlarge-mem**
               **-mstdmain -mfixed-range=**_register-range_ **-mea32  -mea64**
               **-maddress-space-conversion  -mno-address-space-conversion**
               **-mcache-size=**_cache-size_ **-matomic-updates  -mno-atomic-updates**
    
               _System V Options_ **-Qy  -Qn  -YP,**_paths_  **-Ym,**_dir_
    
               _TILE-Gx Options_ **-mcpu=CPU  -m32  -m64  -mbig-endian**
               **-mlittle-endian -mcmodel=**_code-model_
    
               _TILEPro Options_ **-mcpu=**_cpu_  **-m32**
    
               _V850 Options_ **-mlong-calls  -mno-long-calls  -mep  -mno-ep**
               **-mprolog-function  -mno-prolog-function  -mspace -mtda=**_n_
               **-msda=**_n_  **-mzda=**_n_ **-mapp-regs  -mno-app-regs -mdisable-callt**
               **-mno-disable-callt -mv850e2v3  -mv850e2  -mv850e1  -mv850es**
               **-mv850e  -mv850  -mv850e3v5 -mloop -mrelax -mlong-jumps**
               **-msoft-float -mhard-float -mgcc-abi -mrh850-abi -mbig-switch**
    
               _VAX Options_ **-mg  -mgnu  -munix**
    
               _Visium Options_ **-mdebug  -msim  -mfpu  -mno-fpu  -mhard-float**
               **-msoft-float -mcpu=**_cpu-type_  **-mtune=**_cpu-type_  **-msv-mode**
               **-muser-mode**
    
               _VMS Options_ **-mvms-return-codes  -mdebug-main=**_prefix_
               **-mmalloc64 -mpointer-size=**_size_
    
               _VxWorks Options_ **-mrtp  -non-static  -Bstatic  -Bdynamic**
               **-Xbind-lazy  -Xbind-now**
    
               _x86 Options_ **-mtune=**_cpu-type_  **-march=**_cpu-type_
               **-mtune-ctrl=**_feature-list_  **-mdump-tune-features  -mno-default**
               **-mfpmath=**_unit_ **-masm=**_dialect_  **-mno-fancy-math-387**
               **-mno-fp-ret-in-387  -m80387  -mhard-float  -msoft-float**
               **-mno-wide-multiply  -mrtd  -malign-double**
               **-mpreferred-stack-boundary=**_num_ **-mincoming-stack-boundary=**_num_
               **-mcld  -mcx16  -msahf  -mmovbe  -mcrc32 -mrecip  -mrecip=**_opt_
               **-mvzeroupper  -mprefer-avx128  -mprefer-vector-width=**_opt_ **-mmmx**
               **-msse  -msse2  -msse3  -mssse3  -msse4.1  -msse4.2  -msse4**
               **-mavx -mavx2  -mavx512f  -mavx512pf  -mavx512er  -mavx512cd**
               **-mavx512vl -mavx512bw  -mavx512dq  -mavx512ifma  -mavx512vbmi**
               **-msha  -maes -mpclmul  -mfsgsbase  -mrdrnd  -mf16c  -mfma**
               **-mpconfig  -mwbnoinvd -mptwrite  -mprefetchwt1  -mclflushopt**
               **-mclwb  -mxsavec  -mxsaves -msse4a  -m3dnow  -m3dnowa**
               **-mpopcnt  -mabm  -mbmi  -mtbm  -mfma4  -mxop -madx  -mlzcnt**
               **-mbmi2  -mfxsr  -mxsave  -mxsaveopt  -mrtm  -mhle  -mlwp**
               **-mmwaitx  -mclzero  -mpku  -mthreads  -mgfni  -mvaes**
               **-mwaitpkg -mshstk -mmanual-endbr -mforce-indirect-call**
               **-mavx512vbmi2 -mvpclmulqdq  -mavx512bitalg  -mmovdiri**
               **-mmovdir64b  -mavx512vpopcntdq -mavx5124fmaps  -mavx512vnni**
               **-mavx5124vnniw  -mprfchw  -mrdpid -mrdseed  -msgx -mcldemote**
               **-mms-bitfields  -mno-align-stringops  -minline-all-stringops**
               **-minline-stringops-dynamically  -mstringop-strategy=**_alg_
               **-mmemcpy-strategy=**_strategy_  **-mmemset-strategy=**_strategy_
               **-mpush-args  -maccumulate-outgoing-args  -m128bit-long-double**
               **-m96bit-long-double  -mlong-double-64  -mlong-double-80**
               **-mlong-double-128 -mregparm=**_num_  **-msseregparm -mveclibabi=**_type_
               **-mvect8-ret-in-mem -mpc32  -mpc64  -mpc80  -mstackrealign**
               **-momit-leaf-frame-pointer  -mno-red-zone**
               **-mno-tls-direct-seg-refs -mcmodel=**_code-model_  **-mabi=**_name_
               **-maddress-mode=**_mode_ **-m32  -m64  -mx32  -m16  -miamcu**
               **-mlarge-data-threshold=**_num_ **-msse2avx  -mfentry**
               **-mrecord-mcount  -mnop-mcount  -m8bit-idiv**
               **-minstrument-return=**_type_ **-mfentry-name=**_name_
               **-mfentry-section=**_name_ **-mavx256-split-unaligned-load**
               **-mavx256-split-unaligned-store -malign-data=**_type_
               **-mstack-protector-guard=**_guard_ **-mstack-protector-guard-reg=**_reg_
               **-mstack-protector-guard-offset=**_offset_
               **-mstack-protector-guard-symbol=**_symbol_ **-mgeneral-regs-only**
               **-mcall-ms2sysv-xlogues -mindirect-branch=**_choice_
               **-mfunction-return=**_choice_ **-mindirect-branch-register**
    
               _x86 Windows Options_ **-mconsole  -mcygwin  -mno-cygwin  -mdll**
               **-mnop-fun-dllimport  -mthread -municode  -mwin32  -mwindows**
               **-fno-set-stack-executable**
    
               _Xstormy16 Options_ **-msim**
    
               _Xtensa Options_ **-mconst16  -mno-const16 -mfused-madd**
               **-mno-fused-madd -mforce-no-pic -mserialize-volatile**
               **-mno-serialize-volatile -mtext-section-literals**
               **-mno-text-section-literals -mauto-litpools  -mno-auto-litpools**
               **-mtarget-align  -mno-target-align -mlongcalls  -mno-longcalls**
    
               _zSeries Options_ See S/390 and zSeries Options.
    
       **Options Controlling the Kind of Output**
           Compilation can involve up to four stages: preprocessing,
           compilation proper, assembly and linking, always in that order.
           GCC is capable of preprocessing and compiling several files either
           into several assembler input files, or into one assembler input
           file; then each assembler input file produces an object file, and
           linking combines all the object files (those newly compiled, and
           those specified as input) into an executable file.
    
           For any given input file, the file name suffix determines what
           kind of compilation is done:
    
           _file_**.c**
               C source code that must be preprocessed.
    
           _file_**.i**
               C source code that should not be preprocessed.
    
           _file_**.ii**
               C++ source code that should not be preprocessed.
    
           _file_**.m**
               Objective-C source code.  Note that you must link with the
               _libobjc_ library to make an Objective-C program work.
    
           _file_**.mi**
               Objective-C source code that should not be preprocessed.
    
           _file_**.mm**
           _file_**.M**
               Objective-C++ source code.  Note that you must link with the
               _libobjc_ library to make an Objective-C++ program work.  Note
               that **.M** refers to a literal capital M.
    
           _file_**.mii**
               Objective-C++ source code that should not be preprocessed.
    
           _file_**.h**
               C, C++, Objective-C or Objective-C++ header file to be turned
               into a precompiled header (default), or C, C++ header file to
               be turned into an Ada spec (via the **-fdump-ada-spec** switch).
    
           _file_**.cc**
           _file_**.cp**
           _file_**.cxx**
           _file_**.cpp**
           _file_**.CPP**
           _file_**.c++**
           _file_**.C**
               C++ source code that must be preprocessed.  Note that in **.cxx** ,
               the last two letters must both be literally **x**.  Likewise, **.C**
               refers to a literal capital C.
    
           _file_**.mm**
           _file_**.M**
               Objective-C++ source code that must be preprocessed.
    
           _file_**.mii**
               Objective-C++ source code that should not be preprocessed.
    
           _file_**.hh**
           _file_**.H**
           _file_**.hp**
           _file_**.hxx**
           _file_**.hpp**
           _file_**.HPP**
           _file_**.h++**
           _file_**.tcc**
               C++ header file to be turned into a precompiled header or Ada
               spec.
    
           _file_**.f**
           _file_**.for**
           _file_**.ftn**
               Fixed form Fortran source code that should not be
               preprocessed.
    
           _file_**.F**
           _file_**.FOR**
           _file_**.fpp**
           _file_**.FPP**
           _file_**.FTN**
               Fixed form Fortran source code that must be preprocessed (with
               the traditional preprocessor).
    
           _file_**.f90**
           _file_**.f95**
           _file_**.f03**
           _file_**.f08**
               Free form Fortran source code that should not be preprocessed.
    
           _file_**.F90**
           _file_**.F95**
           _file_**.F03**
           _file_**.F08**
               Free form Fortran source code that must be preprocessed (with
               the traditional preprocessor).
    
           _file_**.go**
               Go source code.
    
           _file_**.brig**
               BRIG files (binary representation of HSAIL).
    
           _file_**.d**
               D source code.
    
           _file_**.di**
               D interface file.
    
           _file_**.dd**
               D documentation code (Ddoc).
    
           _file_**.ads**
               Ada source code file that contains a library unit declaration
               (a declaration of a package, subprogram, or generic, or a
               generic instantiation), or a library unit renaming declaration
               (a package, generic, or subprogram renaming declaration).
               Such files are also called _specs_.
    
           _file_**.adb**
               Ada source code file containing a library unit body (a
               subprogram or package body).  Such files are also called
               _bodies_.
    
           _file_**.s**
               Assembler code.
    
           _file_**.S**
           _file_**.sx**
               Assembler code that must be preprocessed.
    
           _other_
               An object file to be fed straight into linking.  Any file name
               with no recognized suffix is treated this way.
    
           You can specify the input language explicitly with the **-x** option:
    
           **-x** _language_
               Specify explicitly the _language_ for the following input files
               (rather than letting the compiler choose a default based on
               the file name suffix).  This option applies to all following
               input files until the next **-x** option.  Possible values for
               _language_ are:
    
                       c  c-header  cpp-output
                       c++  c++-header  c++-cpp-output
                       objective-c  objective-c-header  objective-c-cpp-output
                       objective-c++ objective-c++-header objective-c++-cpp-output
                       assembler  assembler-with-cpp
                       ada
                       d
                       f77  f77-cpp-input f95  f95-cpp-input
                       go
                       brig
    
           **-x none**
               Turn off any specification of a language, so that subsequent
               files are handled according to their file name suffixes (as
               they are if **-x** has not been used at all).
    
           If you only want some of the stages of compilation, you can use **-x**
           (or filename suffixes) to tell **gcc** where to start, and one of the
           options **-c** , **-S** , or **-E** to say where **gcc** is to stop.  Note that some
           combinations (for example, **-x cpp-output -E**) instruct **gcc** to do
           nothing at all.
    
           **-c** Compile or assemble the source files, but do not link.  The
               linking stage simply is not done.  The ultimate output is in
               the form of an object file for each source file.
    
               By default, the object file name for a source file is made by
               replacing the suffix **.c** , **.i** , **.s** , etc., with **.o**.
    
               Unrecognized input files, not requiring compilation or
               assembly, are ignored.
    
           **-S** Stop after the stage of compilation proper; do not assemble.
               The output is in the form of an assembler code file for each
               non-assembler input file specified.
    
               By default, the assembler file name for a source file is made
               by replacing the suffix **.c** , **.i** , etc., with **.s**.
    
               Input files that don't require compilation are ignored.
    
           **-E** Stop after the preprocessing stage; do not run the compiler
               proper.  The output is in the form of preprocessed source
               code, which is sent to the standard output.
    
               Input files that don't require preprocessing are ignored.
    
           **-o** _file_
               Place output in file _file_.  This applies to whatever sort of
               output is being produced, whether it be an executable file, an
               object file, an assembler file or preprocessed C code.
    
               If **-o** is not specified, the default is to put an executable
               file in _a.out_ , the object file for _source.suffix_ in _source.o_ ,
               its assembler file in _source.s_ , a precompiled header file in
               _source.suffix.gch_ , and all preprocessed C source on standard
               output.
    
           **-v** Print (on standard error output) the commands executed to run
               the stages of compilation.  Also print the version number of
               the compiler driver program and of the preprocessor and the
               compiler proper.
    
           **-###**
               Like **-v** except the commands are not executed and arguments are
               quoted unless they contain only alphanumeric characters or
               "./-_".  This is useful for shell scripts to capture the
               driver-generated command lines.
    
           **--help**
               Print (on the standard output) a description of the command-
               line options understood by **gcc**.  If the **-v** option is also
               specified then **--help** is also passed on to the various
               processes invoked by **gcc** , so that they can display the
               command-line options they accept.  If the **-Wextra** option has
               also been specified (prior to the **--help** option), then
               command-line options that have no documentation associated
               with them are also displayed.
    
           **--target-help**
               Print (on the standard output) a description of target-
               specific command-line options for each tool.  For some targets
               extra target-specific information may also be printed.
    
           **--help={**_class_ |[**^**]_qualifier_**}**[**,...**]
               Print (on the standard output) a description of the command-
               line options understood by the compiler that fit into all
               specified classes and qualifiers.  These are the supported
               classes:
    
               **optimizers**
                   Display all of the optimization options supported by the
                   compiler.
    
               **warnings**
                   Display all of the options controlling warning messages
                   produced by the compiler.
    
               **target**
                   Display target-specific options.  Unlike the **--target-help**
                   option however, target-specific options of the linker and
                   assembler are not displayed.  This is because those tools
                   do not currently support the extended **--help=** syntax.
    
               **params**
                   Display the values recognized by the **--param** option.
    
               _language_
                   Display the options supported for _language_ , where _language_
                   is the name of one of the languages supported in this
                   version of GCC.
    
               **common**
                   Display the options that are common to all languages.
    
               These are the supported qualifiers:
    
               **undocumented**
                   Display only those options that are undocumented.
    
               **joined**
                   Display options taking an argument that appears after an
                   equal sign in the same continuous piece of text, such as:
                   **--help=target**.
    
               **separate**
                   Display options taking an argument that appears as a
                   separate word following the original option, such as: **-o**
                   **output-file**.
    
               Thus for example to display all the undocumented target-
               specific switches supported by the compiler, use:
    
                       --help=target,undocumented
    
               The sense of a qualifier can be inverted by prefixing it with
               the **^** character, so for example to display all binary warning
               options (i.e., ones that are either on or off and that do not
               take an argument) that have a description, use:
    
                       --help=warnings,^joined,^undocumented
    
               The argument to **--help=** should not consist solely of inverted
               qualifiers.
    
               Combining several classes is possible, although this usually
               restricts the output so much that there is nothing to display.
               One case where it does work, however, is when one of the
               classes is _target_.  For example, to display all the target-
               specific optimization options, use:
    
                       --help=target,optimizers
    
               The **--help=** option can be repeated on the command line.  Each
               successive use displays its requested class of options,
               skipping those that have already been displayed.  If **--help** is
               also specified anywhere on the command line then this takes
               precedence over any **--help=** option.
    
               If the **-Q** option appears on the command line before the
               **--help=** option, then the descriptive text displayed by **--help=**
               is changed.  Instead of describing the displayed options, an
               indication is given as to whether the option is enabled,
               disabled or set to a specific value (assuming that the
               compiler knows this at the point where the **--help=** option is
               used).
    
               Here is a truncated example from the ARM port of **gcc** :
    
                         % gcc -Q -mabi=2 --help=target -c
                         The following options are target specific:
                         -mabi=                                2
                         -mabort-on-noreturn                   [disabled]
                         -mapcs                                [disabled]
    
               The output is sensitive to the effects of previous command-
               line options, so for example it is possible to find out which
               optimizations are enabled at **-O2** by using:
    
                       -Q -O2 --help=optimizers
    
               Alternatively you can discover which binary optimizations are
               enabled by **-O3** by using:
    
                       gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts
                       gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts
                       diff /tmp/O2-opts /tmp/O3-opts | grep enabled
    
           **--version**
               Display the version number and copyrights of the invoked GCC.
    
           **-pass-exit-codes**
               Normally the **gcc** program exits with the code of 1 if any phase
               of the compiler returns a non-success return code.  If you
               specify **-pass-exit-codes** , the **gcc** program instead returns with
               the numerically highest error produced by any phase returning
               an error indication.  The C, C++, and Fortran front ends
               return 4 if an internal compiler error is encountered.
    
           **-pipe**
               Use pipes rather than temporary files for communication
               between the various stages of compilation.  This fails to work
               on some systems where the assembler is unable to read from a
               pipe; but the GNU assembler has no trouble.
    
           **-specs=**_file_
               Process _file_ after the compiler reads in the standard _specs_
               file, in order to override the defaults which the **gcc** driver
               program uses when determining what switches to pass to **cc1** ,
               **cc1plus** , **as** , **ld** , etc.  More than one **-specs=**_file_ can be
               specified on the command line, and they are processed in
               order, from left to right.
    
           **-wrapper**
               Invoke all subcommands under a wrapper program.  The name of
               the wrapper program and its parameters are passed as a comma
               separated list.
    
                       gcc -c t.c -wrapper gdb,--args
    
               This invokes all subprograms of **gcc** under **gdb --args** , thus the
               invocation of **cc1** is **gdb --args cc1 ...**.
    
           **-ffile-prefix-map=**_old_**=**_new_
               When compiling files residing in directory _old_ , record any
               references to them in the result of the compilation as if the
               files resided in directory _new_ instead.  Specifying this
               option is equivalent to specifying all the individual
               **-f*-prefix-map** options.  This can be used to make reproducible
               builds that are location independent.  See also
               **-fmacro-prefix-map** and **-fdebug-prefix-map**.
    
           **-fplugin=**_name_**.so**
               Load the plugin code in file _name_.so, assumed to be a shared
               object to be dlopen'd by the compiler.  The base name of the
               shared object file is used to identify the plugin for the
               purposes of argument parsing (See **-fplugin-arg-**_name_**-**_key_**=**_value_
               below).  Each plugin should define the callback functions
               specified in the Plugins API.
    
           **-fplugin-arg-**_name_**-**_key_**=**_value_
               Define an argument called _key_ with a value of _value_ for the
               plugin called _name_.
    
           **-fdump-ada-spec**[**-slim**]
               For C and C++ source and include files, generate corresponding
               Ada specs.
    
           **-fada-spec-parent=**_unit_
               In conjunction with **-fdump-ada-spec**[**-slim**] above, generate Ada
               specs as child units of parent _unit_.
    
           **-fdump-go-spec=**_file_
               For input files in any language, generate corresponding Go
               declarations in _file_.  This generates Go "const", "type",
               "var", and "func" declarations which may be a useful way to
               start writing a Go interface to code written in some other
               language.
    
           **@**_file_
               Read command-line options from _file_.  The options read are
               inserted in place of the original @_file_ option.  If _file_ does
               not exist, or cannot be read, then the option will be treated
               literally, and not removed.
    
               Options in _file_ are separated by whitespace.  A whitespace
               character may be included in an option by surrounding the
               entire option in either single or double quotes.  Any
               character (including a backslash) may be included by prefixing
               the character to be included with a backslash.  The _file_ may
               itself contain additional @_file_ options; any such options will
               be processed recursively.
    
       **Compiling C++ Programs**
           C++ source files conventionally use one of the suffixes **.C** , **.cc** ,
           **.cpp** , **.CPP** , **.c++** , **.cp** , or **.cxx** ; C++ header files often use **.hh** ,
           **.hpp** , **.H** , or (for shared template code) **.tcc** ; and preprocessed C++
           files use the suffix **.ii**.  GCC recognizes files with these names
           and compiles them as C++ programs even if you call the compiler
           the same way as for compiling C programs (usually with the name
           **gcc**).
    
           However, the use of **gcc** does not add the C++ library.  **g++** is a
           program that calls GCC and automatically specifies linking against
           the C++ library.  It treats **.c** , **.h** and **.i** files as C++ source
           files instead of C source files unless **-x** is used.  This program
           is also useful when precompiling a C header file with a **.h**
           extension for use in C++ compilations.  On many systems, **g++** is
           also installed with the name **c++**.
    
           When you compile C++ programs, you may specify many of the same
           command-line options that you use for compiling programs in any
           language; or command-line options meaningful for C and related
           languages; or options that are meaningful only for C++ programs.
    
       **Options Controlling C Dialect**
           The following options control the dialect of C (or languages
           derived from C, such as C++, Objective-C and Objective-C++) that
           the compiler accepts:
    
           **-ansi**
               In C mode, this is equivalent to **-std=c90**. In C++ mode, it is
               equivalent to **-std=c++98**.
    
               This turns off certain features of GCC that are incompatible
               with ISO C90 (when compiling C code), or of standard C++ (when
               compiling C++ code), such as the "asm" and "typeof" keywords,
               and predefined macros such as "unix" and "vax" that identify
               the type of system you are using.  It also enables the
               undesirable and rarely used ISO trigraph feature.  For the C
               compiler, it disables recognition of C++ style **//** comments as
               well as the "inline" keyword.
    
               The alternate keywords "__asm__", "__extension__",
               "__inline__" and "__typeof__" continue to work despite **-ansi**.
               You would not want to use them in an ISO C program, of course,
               but it is useful to put them in header files that might be
               included in compilations done with **-ansi**.  Alternate
               predefined macros such as "__unix__" and "__vax__" are also
               available, with or without **-ansi**.
    
               The **-ansi** option does not cause non-ISO programs to be
               rejected gratuitously.  For that, **-Wpedantic** is required in
               addition to **-ansi**.
    
               The macro "__STRICT_ANSI__" is predefined when the **-ansi**
               option is used.  Some header files may notice this macro and
               refrain from declaring certain functions or defining certain
               macros that the ISO standard doesn't call for; this is to
               avoid interfering with any programs that might use these names
               for other things.
    
               Functions that are normally built in but do not have semantics
               defined by ISO C (such as "alloca" and "ffs") are not built-in
               functions when **-ansi** is used.
    
           **-std=**
               Determine the language standard.   This option is currently
               only supported when compiling C or C++.
    
               The compiler can accept several base standards, such as **c90** or
               **c++98** , and GNU dialects of those standards, such as **gnu90** or
               **gnu++98**.  When a base standard is specified, the compiler
               accepts all programs following that standard plus those using
               GNU extensions that do not contradict it.  For example,
               **-std=c90** turns off certain features of GCC that are
               incompatible with ISO C90, such as the "asm" and "typeof"
               keywords, but not other GNU extensions that do not have a
               meaning in ISO C90, such as omitting the middle term of a "?:"
               expression. On the other hand, when a GNU dialect of a
               standard is specified, all features supported by the compiler
               are enabled, even when those features change the meaning of
               the base standard.  As a result, some strict-conforming
               programs may be rejected.  The particular standard is used by
               **-Wpedantic** to identify which features are GNU extensions given
               that version of the standard. For example **-std=gnu90**
               **-Wpedantic** warns about C++ style **//** comments, while **-std=gnu99**
               **-Wpedantic** does not.
    
               A value for this option must be provided; possible values are
    
               **c90**
               **c89**
               **iso9899:1990**
                   Support all ISO C90 programs (certain GNU extensions that
                   conflict with ISO C90 are disabled). Same as **-ansi** for C
                   code.
    
               **iso9899:199409**
                   ISO C90 as modified in amendment 1.
    
               **c99**
               **c9x**
               **iso9899:1999**
               **iso9899:199x**
                   ISO C99.  This standard is substantially completely
                   supported, modulo bugs and floating-point issues (mainly
                   but not entirely relating to optional C99 features from
                   Annexes F and G).  See <**http://gcc.gnu.org/c99status.html **>
                   for more information.  The names **c9x** and **iso9899:199x** are
                   deprecated.
    
               **c11**
               **c1x**
               **iso9899:2011**
                   ISO C11, the 2011 revision of the ISO C standard.  This
                   standard is substantially completely supported, modulo
                   bugs, floating-point issues (mainly but not entirely
                   relating to optional C11 features from Annexes F and G)
                   and the optional Annexes K (Bounds-checking interfaces)
                   and L (Analyzability).  The name **c1x** is deprecated.
    
               **c17**
               **c18**
               **iso9899:2017**
               **iso9899:2018**
                   ISO C17, the 2017 revision of the ISO C standard
                   (published in 2018).  This standard is same as C11 except
                   for corrections of defects (all of which are also applied
                   with **-std=c11**) and a new value of "__STDC_VERSION__", and
                   so is supported to the same extent as C11.
    
               **c2x** The next version of the ISO C standard, still under
                   development.  The support for this version is experimental
                   and incomplete.
    
               **gnu90**
               **gnu89**
                   GNU dialect of ISO C90 (including some C99 features).
    
               **gnu99**
               **gnu9x**
                   GNU dialect of ISO C99.  The name **gnu9x** is deprecated.
    
               **gnu11**
               **gnu1x**
                   GNU dialect of ISO C11.  The name **gnu1x** is deprecated.
    
               **gnu17**
               **gnu18**
                   GNU dialect of ISO C17.  This is the default for C code.
    
               **gnu2x**
                   The next version of the ISO C standard, still under
                   development, plus GNU extensions.  The support for this
                   version is experimental and incomplete.
    
               **c++98**
               **c++03**
                   The 1998 ISO C++ standard plus the 2003 technical
                   corrigendum and some additional defect reports. Same as
                   **-ansi** for C++ code.
    
               **gnu++98**
               **gnu++03**
                   GNU dialect of **-std=c++98**.
    
               **c++11**
               **c++0x**
                   The 2011 ISO C++ standard plus amendments.  The name **c++0x**
                   is deprecated.
    
               **gnu++11**
               **gnu++0x**
                   GNU dialect of **-std=c++11**.  The name **gnu++0x** is
                   deprecated.
    
               **c++14**
               **c++1y**
                   The 2014 ISO C++ standard plus amendments.  The name **c++1y**
                   is deprecated.
    
               **gnu++14**
               **gnu++1y**
                   GNU dialect of **-std=c++14**.  This is the default for C++
                   code.  The name **gnu++1y** is deprecated.
    
               **c++17**
               **c++1z**
                   The 2017 ISO C++ standard plus amendments.  The name **c++1z**
                   is deprecated.
    
               **gnu++17**
               **gnu++1z**
                   GNU dialect of **-std=c++17**.  The name **gnu++1z** is
                   deprecated.
    
               **c++2a**
                   The next revision of the ISO C++ standard, tentatively
                   planned for 2020.  Support is highly experimental, and
                   will almost certainly change in incompatible ways in
                   future releases.
    
               **gnu++2a**
                   GNU dialect of **-std=c++2a**.  Support is highly
                   experimental, and will almost certainly change in
                   incompatible ways in future releases.
    
           **-fgnu89-inline**
               The option **-fgnu89-inline** tells GCC to use the traditional GNU
               semantics for "inline" functions when in C99 mode.
    
               Using this option is roughly equivalent to adding the
               "gnu_inline" function attribute to all inline functions.
    
               The option **-fno-gnu89-inline** explicitly tells GCC to use the
               C99 semantics for "inline" when in C99 or gnu99 mode (i.e., it
               specifies the default behavior).  This option is not supported
               in **-std=c90** or **-std=gnu90** mode.
    
               The preprocessor macros "__GNUC_GNU_INLINE__" and
               "__GNUC_STDC_INLINE__" may be used to check which semantics
               are in effect for "inline" functions.
    
           **-fpermitted-flt-eval-methods=**_style_
               ISO/IEC TS 18661-3 defines new permissible values for
               "FLT_EVAL_METHOD" that indicate that operations and constants
               with a semantic type that is an interchange or extended format
               should be evaluated to the precision and range of that type.
               These new values are a superset of those permitted under
               C99/C11, which does not specify the meaning of other positive
               values of "FLT_EVAL_METHOD".  As such, code conforming to C11
               may not have been written expecting the possibility of the new
               values.
    
               **-fpermitted-flt-eval-methods** specifies whether the compiler
               should allow only the values of "FLT_EVAL_METHOD" specified in
               C99/C11, or the extended set of values specified in ISO/IEC TS
               18661-3.
    
               _style_ is either "c11" or "ts-18661-3" as appropriate.
    
               The default when in a standards compliant mode (**-std=c11** or
               similar) is **-fpermitted-flt-eval-methods=c11**.  The default
               when in a GNU dialect (**-std=gnu11** or similar) is
               **-fpermitted-flt-eval-methods=ts-18661-3**.
    
           **-aux-info** _filename_
               Output to the given filename prototyped declarations for all
               functions declared and/or defined in a translation unit,
               including those in header files.  This option is silently
               ignored in any language other than C.
    
               Besides declarations, the file indicates, in comments, the
               origin of each declaration (source file and line), whether the
               declaration was implicit, prototyped or unprototyped (**I** , **N** for
               new or **O** for old, respectively, in the first character after
               the line number and the colon), and whether it came from a
               declaration or a definition (**C** or **F** , respectively, in the
               following character).  In the case of function definitions, a
               K&R-style list of arguments followed by their declarations is
               also provided, inside comments, after the declaration.
    
           **-fallow-parameterless-variadic-functions**
               Accept variadic functions without named parameters.
    
               Although it is possible to define such a function, this is not
               very useful as it is not possible to read the arguments.  This
               is only supported for C as this construct is allowed by C++.
    
           **-fno-asm**
               Do not recognize "asm", "inline" or "typeof" as a keyword, so
               that code can use these words as identifiers.  You can use the
               keywords "__asm__", "__inline__" and "__typeof__" instead.
               **-ansi** implies **-fno-asm**.
    
               In C++, this switch only affects the "typeof" keyword, since
               "asm" and "inline" are standard keywords.  You may want to use
               the **-fno-gnu-keywords** flag instead, which has the same effect.
               In C99 mode (**-std=c99** or **-std=gnu99**), this switch only affects
               the "asm" and "typeof" keywords, since "inline" is a standard
               keyword in ISO C99.
    
           **-fno-builtin**
           **-fno-builtin-**_function_
               Don't recognize built-in functions that do not begin with
               **__builtin_** as prefix.
    
               GCC normally generates special code to handle certain built-in
               functions more efficiently; for instance, calls to "alloca"
               may become single instructions which adjust the stack
               directly, and calls to "memcpy" may become inline copy loops.
               The resulting code is often both smaller and faster, but since
               the function calls no longer appear as such, you cannot set a
               breakpoint on those calls, nor can you change the behavior of
               the functions by linking with a different library.  In
               addition, when a function is recognized as a built-in
               function, GCC may use information about that function to warn
               about problems with calls to that function, or to generate
               more efficient code, even if the resulting code still contains
               calls to that function.  For example, warnings are given with
               **-Wformat** for bad calls to "printf" when "printf" is built in
               and "strlen" is known not to modify global memory.
    
               With the **-fno-builtin-**_function_ option only the built-in
               function _function_ is disabled.  _function_ must not begin with
               **__builtin_**.  If a function is named that is not built-in in
               this version of GCC, this option is ignored.  There is no
               corresponding **-fbuiltin-**_function_ option; if you wish to enable
               built-in functions selectively when using **-fno-builtin** or
               **-ffreestanding** , you may define macros such as:
    
                       #define abs(n)          __builtin_abs ((n))
                       #define strcpy(d, s)    __builtin_strcpy ((d), (s))
    
           **-fgimple**
               Enable parsing of function definitions marked with "__GIMPLE".
               This is an experimental feature that allows unit testing of
               GIMPLE passes.
    
           **-fhosted**
               Assert that compilation targets a hosted environment.  This
               implies **-fbuiltin**.  A hosted environment is one in which the
               entire standard library is available, and in which "main" has
               a return type of "int".  Examples are nearly everything except
               a kernel.  This is equivalent to **-fno-freestanding**.
    
           **-ffreestanding**
               Assert that compilation targets a freestanding environment.
               This implies **-fno-builtin**.  A freestanding environment is one
               in which the standard library may not exist, and program
               startup may not necessarily be at "main".  The most obvious
               example is an OS kernel.  This is equivalent to **-fno-hosted**.
    
           **-fopenacc**
               Enable handling of OpenACC directives "#pragma acc" in C/C++
               and "!$acc" in Fortran.  When **-fopenacc** is specified, the
               compiler generates accelerated code according to the OpenACC
               Application Programming Interface v2.0
               <**https://www.openacc.org **>.  This option implies **-pthread** , and
               thus is only supported on targets that have support for
               **-pthread**.
    
           **-fopenacc-dim=**_geom_
               Specify default compute dimensions for parallel offload
               regions that do not explicitly specify.  The _geom_ value is a
               triple of ':'-separated sizes, in order 'gang', 'worker' and,
               'vector'.  A size can be omitted, to use a target-specific
               default value.
    
           **-fopenmp**
               Enable handling of OpenMP directives "#pragma omp" in C/C++
               and "!$omp" in Fortran.  When **-fopenmp** is specified, the
               compiler generates parallel code according to the OpenMP
               Application Program Interface v4.5 <**https://www.openmp.org **>.
               This option implies **-pthread** , and thus is only supported on
               targets that have support for **-pthread**. **-fopenmp** implies
               **-fopenmp-simd**.
    
           **-fopenmp-simd**
               Enable handling of OpenMP's SIMD directives with "#pragma omp"
               in C/C++ and "!$omp" in Fortran. Other OpenMP directives are
               ignored.
    
           **-fgnu-tm**
               When the option **-fgnu-tm** is specified, the compiler generates
               code for the Linux variant of Intel's current Transactional
               Memory ABI specification document (Revision 1.1, May 6 2009).
               This is an experimental feature whose interface may change in
               future versions of GCC, as the official specification changes.
               Please note that not all architectures are supported for this
               feature.
    
               For more information on GCC's support for transactional
               memory,
    
               Note that the transactional memory feature is not supported
               with non-call exceptions (**-fnon-call-exceptions**).
    
           **-fms-extensions**
               Accept some non-standard constructs used in Microsoft header
               files.
    
               In C++ code, this allows member names in structures to be
               similar to previous types declarations.
    
                       typedef int UOW;
                       struct ABC {
                         UOW UOW;
                       };
    
               Some cases of unnamed fields in structures and unions are only
               accepted with this option.
    
               Note that this option is off for all targets but x86 targets
               using ms-abi.
    
           **-fplan9-extensions**
               Accept some non-standard constructs used in Plan 9 code.
    
               This enables **-fms-extensions** , permits passing pointers to
               structures with anonymous fields to functions that expect
               pointers to elements of the type of the field, and permits
               referring to anonymous fields declared using a typedef.
               This is only supported for C, not C++.
    
           **-fcond-mismatch**
               Allow conditional expressions with mismatched types in the
               second and third arguments.  The value of such an expression
               is void.  This option is not supported for C++.
    
           **-flax-vector-conversions**
               Allow implicit conversions between vectors with differing
               numbers of elements and/or incompatible element types.  This
               option should not be used for new code.
    
           **-funsigned-char**
               Let the type "char" be unsigned, like "unsigned char".
    
               Each kind of machine has a default for what "char" should be.
               It is either like "unsigned char" by default or like "signed
               char" by default.
    
               Ideally, a portable program should always use "signed char" or
               "unsigned char" when it depends on the signedness of an
               object.  But many programs have been written to use plain
               "char" and expect it to be signed, or expect it to be
               unsigned, depending on the machines they were written for.
               This option, and its inverse, let you make such a program work
               with the opposite default.
    
               The type "char" is always a distinct type from each of "signed
               char" or "unsigned char", even though its behavior is always
               just like one of those two.
    
           **-fsigned-char**
               Let the type "char" be signed, like "signed char".
    
               Note that this is equivalent to **-fno-unsigned-char** , which is
               the negative form of **-funsigned-char**.  Likewise, the option
               **-fno-signed-char** is equivalent to **-funsigned-char**.
    
           **-fsigned-bitfields**
           **-funsigned-bitfields**
           **-fno-signed-bitfields**
           **-fno-unsigned-bitfields**
               These options control whether a bit-field is signed or
               unsigned, when the declaration does not use either "signed" or
               "unsigned".  By default, such a bit-field is signed, because
               this is consistent: the basic integer types such as "int" are
               signed types.
    
           **-fsso-struct=**_endianness_
               Set the default scalar storage order of structures and unions
               to the specified endianness.  The accepted values are **big-**
               **endian** , **little-endian** and **native** for the native endianness of
               the target (the default).  This option is not supported for
               C++.
    
               **Warning:** the **-fsso-struct** switch causes GCC to generate code
               that is not binary compatible with code generated without it
               if the specified endianness is not the native endianness of
               the target.
    
       **Options Controlling C++ Dialect**
           This section describes the command-line options that are only
           meaningful for C++ programs.  You can also use most of the GNU
           compiler options regardless of what language your program is in.
           For example, you might compile a file _firstClass.C_ like this:
    
                   g++ -g -fstrict-enums -O -c firstClass.C
    
           In this example, only **-fstrict-enums** is an option meant only for
           C++ programs; you can use the other options with any language
           supported by GCC.
    
           Some options for compiling C programs, such as **-std** , are also
           relevant for C++ programs.
    
           Here is a list of options that are _only_ for compiling C++
           programs:
    
           **-fabi-version=**_n_
               Use version _n_ of the C++ ABI.  The default is version 0.
    
               Version 0 refers to the version conforming most closely to the
               C++ ABI specification.  Therefore, the ABI obtained using
               version 0 will change in different versions of G++ as ABI bugs
               are fixed.
    
               Version 1 is the version of the C++ ABI that first appeared in
               G++ 3.2.
    
               Version 2 is the version of the C++ ABI that first appeared in
               G++ 3.4, and was the default through G++ 4.9.
    
               Version 3 corrects an error in mangling a constant address as
               a template argument.
    
               Version 4, which first appeared in G++ 4.5, implements a
               standard mangling for vector types.
    
               Version 5, which first appeared in G++ 4.6, corrects the
               mangling of attribute const/volatile on function pointer
               types, decltype of a plain decl, and use of a function
               parameter in the declaration of another parameter.
    
               Version 6, which first appeared in G++ 4.7, corrects the
               promotion behavior of C++11 scoped enums and the mangling of
               template argument packs, const/static_cast, prefix ++ and --,
               and a class scope function used as a template argument.
    
               Version 7, which first appeared in G++ 4.8, that treats
               nullptr_t as a builtin type and corrects the mangling of
               lambdas in default argument scope.
    
               Version 8, which first appeared in G++ 4.9, corrects the
               substitution behavior of function types with function-cv-
               qualifiers.
    
               Version 9, which first appeared in G++ 5.2, corrects the
               alignment of "nullptr_t".
    
               Version 10, which first appeared in G++ 6.1, adds mangling of
               attributes that affect type identity, such as ia32 calling
               convention attributes (e.g. **stdcall**).
    
               Version 11, which first appeared in G++ 7, corrects the
               mangling of sizeof... expressions and operator names.  For
               multiple entities with the same name within a function, that
               are declared in different scopes, the mangling now changes
               starting with the twelfth occurrence.  It also implies
               **-fnew-inheriting-ctors**.
    
               Version 12, which first appeared in G++ 8, corrects the
               calling conventions for empty classes on the x86_64 target and
               for classes with only deleted copy/move constructors.  It
               accidentally changes the calling convention for classes with a
               deleted copy constructor and a trivial move constructor.
    
               Version 13, which first appeared in G++ 8.2, fixes the
               accidental change in version 12.
    
               See also **-Wabi**.
    
           **-fabi-compat-version=**_n_
               On targets that support strong aliases, G++ works around
               mangling changes by creating an alias with the correct mangled
               name when defining a symbol with an incorrect mangled name.
               This switch specifies which ABI version to use for the alias.
    
               With **-fabi-version=0**(the default), this defaults to 11 (GCC 7
               compatibility).  If another ABI version is explicitly
               selected, this defaults to 0.  For compatibility with GCC
               versions 3.2 through 4.9, use **-fabi-compat-version=2**.
    
               If this option is not provided but **-Wabi=**_n_ is, that version is
               used for compatibility aliases.  If this option is provided
               along with **-Wabi**(without the version), the version from this
               option is used for the warning.
    
           **-fno-access-control**
               Turn off all access checking.  This switch is mainly useful
               for working around bugs in the access control code.
    
           **-faligned-new**
               Enable support for C++17 "new" of types that require more
               alignment than "void* ::operator new(std::size_t)" provides.
               A numeric argument such as "-faligned-new=32" can be used to
               specify how much alignment (in bytes) is provided by that
               function, but few users will need to override the default of
               "alignof(std::max_align_t)".
    
               This flag is enabled by default for **-std=c++17**.
    
           **-fchar8_t**
           **-fno-char8_t**
               Enable support for "char8_t" as adopted for C++2a.  This
               includes the addition of a new "char8_t" fundamental type,
               changes to the types of UTF-8 string and character literals,
               new signatures for user-defined literals, associated standard
               library updates, and new "__cpp_char8_t" and
               "__cpp_lib_char8_t" feature test macros.
    
               This option enables functions to be overloaded for ordinary
               and UTF-8 strings:
    
                       int f(const char *);    // #1
                       int f(const char8_t *); // #2
                       int v1 = f("text");     // Calls #1
                       int v2 = f(u8"text");   // Calls #2
    
               and introduces new signatures for user-defined literals:
    
                       int operator""_udl1(char8_t);
                       int v3 = u8'x'_udl1;
                       int operator""_udl2(const char8_t*, std::size_t);
                       int v4 = u8"text"_udl2;
                       template<typename T, T...> int operator""_udl3();
                       int v5 = u8"text"_udl3;
    
               The change to the types of UTF-8 string and character literals
               introduces incompatibilities with ISO C++11 and later
               standards.  For example, the following code is well-formed
               under ISO C++11, but is ill-formed when **-fchar8_t** is
               specified.
    
                       char ca[] = u8"xx";     // error: char-array initialized from wide
                                               //        string
                       const char *cp = u8"xx";// error: invalid conversion from
                                               //        `const char8_t*' to `const char*'
                       int f(const char*);
                       auto v = f(u8"xx");     // error: invalid conversion from
                                               //        `const char8_t*' to `const char*'
                       std::string s{u8"xx"};  // error: no matching function for call to
                                               //        `std::basic_string<char>::basic_string()'
                       using namespace std::literals;
                       s = u8"xx"s;            // error: conversion from
                                               //        `basic_string<char8_t>' to non-scalar
                                               //        type `basic_string<char>' requested
    
           **-fcheck-new**
               Check that the pointer returned by "operator new" is non-null
               before attempting to modify the storage allocated.  This check
               is normally unnecessary because the C++ standard specifies
               that "operator new" only returns 0 if it is declared
               "throw()", in which case the compiler always checks the return
               value even without this option.  In all other cases, when
               "operator new" has a non-empty exception specification, memory
               exhaustion is signalled by throwing "std::bad_alloc".  See
               also **new (nothrow)**.
    
           **-fconcepts**
               Enable support for the C++ Extensions for Concepts Technical
               Specification, ISO 19217 (2015), which allows code like
    
                       template <class T> concept bool Addable = requires (T t) { t + t; };
                       template <Addable T> T add (T a, T b) { return a + b; }
    
           **-fconstexpr-depth=**_n_
               Set the maximum nested evaluation depth for C++11 constexpr
               functions to _n_.  A limit is needed to detect endless recursion
               during constant expression evaluation.  The minimum specified
               by the standard is 512.
    
           **-fconstexpr-loop-limit=**_n_
               Set the maximum number of iterations for a loop in C++14
               constexpr functions to _n_.  A limit is needed to detect
               infinite loops during constant expression evaluation.  The
               default is 262144 (1<<18).
    
           **-fconstexpr-ops-limit=**_n_
               Set the maximum number of operations during a single constexpr
               evaluation.  Even when number of iterations of a single loop
               is limited with the above limit, if there are several nested
               loops and each of them has many iterations but still smaller
               than the above limit, or if in a body of some loop or even
               outside of a loop too many expressions need to be evaluated,
               the resulting constexpr evaluation might take too long.  The
               default is 33554432 (1<<25).
    
           **-fdeduce-init-list**
               Enable deduction of a template type parameter as
               "std::initializer_list" from a brace-enclosed initializer
               list, i.e.
    
                       template <class T> auto forward(T t) -> decltype (realfn (t))
                       {
                         return realfn (t);
                       }
    
                       void f()
                       {
                         forward({1,2}); // call forward<std::initializer_list<int>>
                       }
    
               This deduction was implemented as a possible extension to the
               originally proposed semantics for the C++11 standard, but was
               not part of the final standard, so it is disabled by default.
               This option is deprecated, and may be removed in a future
               version of G++.
    
           **-fno-elide-constructors**
               The C++ standard allows an implementation to omit creating a
               temporary that is only used to initialize another object of
               the same type.  Specifying this option disables that
               optimization, and forces G++ to call the copy constructor in
               all cases.  This option also causes G++ to call trivial member
               functions which otherwise would be expanded inline.
    
               In C++17, the compiler is required to omit these temporaries,
               but this option still affects trivial member functions.
    
           **-fno-enforce-eh-specs**
               Don't generate code to check for violation of exception
               specifications at run time.  This option violates the C++
               standard, but may be useful for reducing code size in
               production builds, much like defining "NDEBUG".  This does not
               give user code permission to throw exceptions in violation of
               the exception specifications; the compiler still optimizes
               based on the specifications, so throwing an unexpected
               exception results in undefined behavior at run time.
    
           **-fextern-tls-init**
           **-fno-extern-tls-init**
               The C++11 and OpenMP standards allow "thread_local" and
               "threadprivate" variables to have dynamic (runtime)
               initialization.  To support this, any use of such a variable
               goes through a wrapper function that performs any necessary
               initialization.  When the use and definition of the variable
               are in the same translation unit, this overhead can be
               optimized away, but when the use is in a different translation
               unit there is significant overhead even if the variable
               doesn't actually need dynamic initialization.  If the
               programmer can be sure that no use of the variable in a non-
               defining TU needs to trigger dynamic initialization (either
               because the variable is statically initialized, or a use of
               the variable in the defining TU will be executed before any
               uses in another TU), they can avoid this overhead with the
               **-fno-extern-tls-init** option.
    
               On targets that support symbol aliases, the default is
               **-fextern-tls-init**.  On targets that do not support symbol
               aliases, the default is **-fno-extern-tls-init**.
    
           **-fno-gnu-keywords**
               Do not recognize "typeof" as a keyword, so that code can use
               this word as an identifier.  You can use the keyword
               "__typeof__" instead.  This option is implied by the strict
               ISO C++ dialects: **-ansi** , **-std=c++98** , **-std=c++11** , etc.
    
           **-fno-implicit-templates**
               Never emit code for non-inline templates that are instantiated
               implicitly (i.e. by use); only emit code for explicit
               instantiations.  If you use this option, you must take care to
               structure your code to include all the necessary explicit
               instantiations to avoid getting undefined symbols at link
               time.
    
           **-fno-implicit-inline-templates**
               Don't emit code for implicit instantiations of inline
               templates, either.  The default is to handle inlines
               differently so that compiles with and without optimization
               need the same set of explicit instantiations.
    
           **-fno-implement-inlines**
               To save space, do not emit out-of-line copies of inline
               functions controlled by "#pragma implementation".  This causes
               linker errors if these functions are not inlined everywhere
               they are called.
    
           **-fms-extensions**
               Disable Wpedantic warnings about constructs used in MFC, such
               as implicit int and getting a pointer to member function via
               non-standard syntax.
    
           **-fnew-inheriting-ctors**
               Enable the P0136 adjustment to the semantics of C++11
               constructor inheritance.  This is part of C++17 but also
               considered to be a Defect Report against C++11 and C++14.
               This flag is enabled by default unless **-fabi-version=10** or
               lower is specified.
    
           **-fnew-ttp-matching**
               Enable the P0522 resolution to Core issue 150, template
               template parameters and default arguments: this allows a
               template with default template arguments as an argument for a
               template template parameter with fewer template parameters.
               This flag is enabled by default for **-std=c++17**.
    
           **-fno-nonansi-builtins**
               Disable built-in declarations of functions that are not
               mandated by ANSI/ISO C.  These include "ffs", "alloca",
               "_exit", "index", "bzero", "conjf", and other related
               functions.
    
           **-fnothrow-opt**
               Treat a "throw()" exception specification as if it were a
               "noexcept" specification to reduce or eliminate the text size
               overhead relative to a function with no exception
               specification.  If the function has local variables of types
               with non-trivial destructors, the exception specification
               actually makes the function smaller because the EH cleanups
               for those variables can be optimized away.  The semantic
               effect is that an exception thrown out of a function with such
               an exception specification results in a call to "terminate"
               rather than "unexpected".
    
           **-fno-operator-names**
               Do not treat the operator name keywords "and", "bitand",
               "bitor", "compl", "not", "or" and "xor" as synonyms as
               keywords.
    
           **-fno-optional-diags**
               Disable diagnostics that the standard says a compiler does not
               need to issue.  Currently, the only such diagnostic issued by
               G++ is the one for a name having multiple meanings within a
               class.
    
           **-fpermissive**
               Downgrade some diagnostics about nonconformant code from
               errors to warnings.  Thus, using **-fpermissive** allows some
               nonconforming code to compile.
    
           **-fno-pretty-templates**
               When an error message refers to a specialization of a function
               template, the compiler normally prints the signature of the
               template followed by the template arguments and any typedefs
               or typenames in the signature (e.g. "void f(T) [with T = int]"
               rather than "void f(int)") so that it's clear which template
               is involved.  When an error message refers to a specialization
               of a class template, the compiler omits any template arguments
               that match the default template arguments for that template.
               If either of these behaviors make it harder to understand the
               error message rather than easier, you can use
               **-fno-pretty-templates** to disable them.
    
           **-frepo**
               Enable automatic template instantiation at link time.  This
               option also implies **-fno-implicit-templates**.
    
           **-fno-rtti**
               Disable generation of information about every class with
               virtual functions for use by the C++ run-time type
               identification features ("dynamic_cast" and "typeid").  If you
               don't use those parts of the language, you can save some space
               by using this flag.  Note that exception handling uses the
               same information, but G++ generates it as needed. The
               "dynamic_cast" operator can still be used for casts that do
               not require run-time type information, i.e. casts to "void *"
               or to unambiguous base classes.
    
               Mixing code compiled with **-frtti** with that compiled with
               **-fno-rtti** may not work.  For example, programs may fail to
               link if a class compiled with **-fno-rtti** is used as a base for
               a class compiled with **-frtti**.
    
           **-fsized-deallocation**
               Enable the built-in global declarations
    
                       void operator delete (void *, std::size_t) noexcept;
                       void operator delete[] (void *, std::size_t) noexcept;
    
               as introduced in C++14.  This is useful for user-defined
               replacement deallocation functions that, for example, use the
               size of the object to make deallocation faster.  Enabled by
               default under **-std=c++14** and above.  The flag
               **-Wsized-deallocation** warns about places that might want to add
               a definition.
    
           **-fstrict-enums**
               Allow the compiler to optimize using the assumption that a
               value of enumerated type can only be one of the values of the
               enumeration (as defined in the C++ standard; basically, a
               value that can be represented in the minimum number of bits
               needed to represent all the enumerators).  This assumption may
               not be valid if the program uses a cast to convert an
               arbitrary integer value to the enumerated type.
    
           **-fstrong-eval-order**
               Evaluate member access, array subscripting, and shift
               expressions in left-to-right order, and evaluate assignment in
               right-to-left order, as adopted for C++17.  Enabled by default
               with **-std=c++17**.  **-fstrong-eval-order=some** enables just the
               ordering of member access and shift expressions, and is the
               default without **-std=c++17**.
    
           **-ftemplate-backtrace-limit=**_n_
               Set the maximum number of template instantiation notes for a
               single warning or error to _n_.  The default value is 10.
    
           **-ftemplate-depth=**_n_
               Set the maximum instantiation depth for template classes to _n_.
               A limit on the template instantiation depth is needed to
               detect endless recursions during template class instantiation.
               ANSI/ISO C++ conforming programs must not rely on a maximum
               depth greater than 17 (changed to 1024 in C++11).  The default
               value is 900, as the compiler can run out of stack space
               before hitting 1024 in some situations.
    
           **-fno-threadsafe-statics**
               Do not emit the extra code to use the routines specified in
               the C++ ABI for thread-safe initialization of local statics.
               You can use this option to reduce code size slightly in code
               that doesn't need to be thread-safe.
    
           **-fuse-cxa-atexit**
               Register destructors for objects with static storage duration
               with the "__cxa_atexit" function rather than the "atexit"
               function.  This option is required for fully standards-
               compliant handling of static destructors, but only works if
               your C library supports "__cxa_atexit".
    
           **-fno-use-cxa-get-exception-ptr**
               Don't use the "__cxa_get_exception_ptr" runtime routine.  This
               causes "std::uncaught_exception" to be incorrect, but is
               necessary if the runtime routine is not available.
    
           **-fvisibility-inlines-hidden**
               This switch declares that the user does not attempt to compare
               pointers to inline functions or methods where the addresses of
               the two functions are taken in different shared objects.
    
               The effect of this is that GCC may, effectively, mark inline
               methods with "__attribute__ ((visibility ("hidden")))" so that
               they do not appear in the export table of a DSO and do not
               require a PLT indirection when used within the DSO.  Enabling
               this option can have a dramatic effect on load and link times
               of a DSO as it massively reduces the size of the dynamic
               export table when the library makes heavy use of templates.
    
               The behavior of this switch is not quite the same as marking
               the methods as hidden directly, because it does not affect
               static variables local to the function or cause the compiler
               to deduce that the function is defined in only one shared
               object.
    
               You may mark a method as having a visibility explicitly to
               negate the effect of the switch for that method.  For example,
               if you do want to compare pointers to a particular inline
               method, you might mark it as having default visibility.
               Marking the enclosing class with explicit visibility has no
               effect.
    
               Explicitly instantiated inline methods are unaffected by this
               option as their linkage might otherwise cross a shared library
               boundary.
    
           **-fvisibility-ms-compat**
               This flag attempts to use visibility settings to make GCC's
               C++ linkage model compatible with that of Microsoft Visual
               Studio.
    
               The flag makes these changes to GCC's linkage model:
    
               1.  It sets the default visibility to "hidden", like
                   **-fvisibility=hidden**.
    
               2.  Types, but not their members, are not hidden by default.
    
               3.  The One Definition Rule is relaxed for types without
                   explicit visibility specifications that are defined in
                   more than one shared object: those declarations are
                   permitted if they are permitted when this option is not
                   used.
    
               In new code it is better to use **-fvisibility=hidden** and export
               those classes that are intended to be externally visible.
               Unfortunately it is possible for code to rely, perhaps
               accidentally, on the Visual Studio behavior.
    
               Among the consequences of these changes are that static data
               members of the same type with the same name but defined in
               different shared objects are different, so changing one does
               not change the other; and that pointers to function members
               defined in different shared objects may not compare equal.
               When this flag is given, it is a violation of the ODR to
               define types with the same name differently.
    
           **-fno-weak**
               Do not use weak symbol support, even if it is provided by the
               linker.  By default, G++ uses weak symbols if they are
               available.  This option exists only for testing, and should
               not be used by end-users; it results in inferior code and has
               no benefits.  This option may be removed in a future release
               of G++.
    
           **-nostdinc++**
               Do not search for header files in the standard directories
               specific to C++, but do still search the other standard
               directories.  (This option is used when building the C++
               library.)
    
           In addition, these optimization, warning, and code generation
           options have meanings only for C++ programs:
    
           **-Wabi**(C, Objective-C, C++ and Objective-C++ only)
               Warn when G++ it generates code that is probably not
               compatible with the vendor-neutral C++ ABI.  Since G++ now
               defaults to updating the ABI with each major release, normally
               **-Wabi** will warn only if there is a check added later in a
               release series for an ABI issue discovered since the initial
               release.  **-Wabi** will warn about more things if an older ABI
               version is selected (with **-fabi-version=**_n_).
    
               **-Wabi** can also be used with an explicit version number to warn
               about compatibility with a particular **-fabi-version** level,
               e.g. **-Wabi=2** to warn about changes relative to
               **-fabi-version=2**.
    
               If an explicit version number is provided and
               **-fabi-compat-version** is not specified, the version number from
               this option is used for compatibility aliases.  If no explicit
               version number is provided with this option, but
               **-fabi-compat-version** is specified, that version number is used
               for ABI warnings.
    
               Although an effort has been made to warn about all such cases,
               there are probably some cases that are not warned about, even
               though G++ is generating incompatible code.  There may also be
               cases where warnings are emitted even though the code that is
               generated is compatible.
    
               You should rewrite your code to avoid these warnings if you
               are concerned about the fact that code generated by G++ may
               not be binary compatible with code generated by other
               compilers.
    
               Known incompatibilities in **-fabi-version=2**(which was the
               default from GCC 3.4 to 4.9) include:
    
               *   A template with a non-type template parameter of reference
                   type was mangled incorrectly:
    
                           extern int N;
                           template <int &> struct S {};
                           void n (S<N>) {2}
    
                   This was fixed in **-fabi-version=3**.
    
               *   SIMD vector types declared using "__attribute
                   ((vector_size))" were mangled in a non-standard way that
                   does not allow for overloading of functions taking vectors
                   of different sizes.
    
                   The mangling was changed in **-fabi-version=4**.
    
               *   "__attribute ((const))" and "noreturn" were mangled as
                   type qualifiers, and "decltype" of a plain declaration was
                   folded away.
    
                   These mangling issues were fixed in **-fabi-version=5**.
    
               *   Scoped enumerators passed as arguments to a variadic
                   function are promoted like unscoped enumerators, causing
                   "va_arg" to complain.  On most targets this does not
                   actually affect the parameter passing ABI, as there is no
                   way to pass an argument smaller than "int".
    
                   Also, the ABI changed the mangling of template argument
                   packs, "const_cast", "static_cast", prefix
                   increment/decrement, and a class scope function used as a
                   template argument.
    
                   These issues were corrected in **-fabi-version=6**.
    
               *   Lambdas in default argument scope were mangled
                   incorrectly, and the ABI changed the mangling of
                   "nullptr_t".
    
                   These issues were corrected in **-fabi-version=7**.
    
               *   When mangling a function type with function-cv-qualifiers,
                   the un-qualified function type was incorrectly treated as
                   a substitution candidate.
    
                   This was fixed in **-fabi-version=8** , the default for GCC
                   5.1.
    
               *   "decltype(nullptr)" incorrectly had an alignment of 1,
                   leading to unaligned accesses.  Note that this did not
                   affect the ABI of a function with a "nullptr_t" parameter,
                   as parameters have a minimum alignment.
    
                   This was fixed in **-fabi-version=9** , the default for GCC
                   5.2.
    
               *   Target-specific attributes that affect the identity of a
                   type, such as ia32 calling conventions on a function type
                   (stdcall, regparm, etc.), did not affect the mangled name,
                   leading to name collisions when function pointers were
                   used as template arguments.
    
                   This was fixed in **-fabi-version=10** , the default for GCC
                   6.1.
    
               It also warns about psABI-related changes.  The known psABI
               changes at this point include:
    
               *   For SysV/x86-64, unions with "long double" members are
                   passed in memory as specified in psABI.  For example:
    
                           union U {
                             long double ld;
                             int i;
                           };
    
                   "union U" is always passed in memory.
    
           **-Wabi-tag**(C++ and Objective-C++ only)
               Warn when a type with an ABI tag is used in a context that
               does not have that ABI tag.  See **C++ Attributes** for more
               information about ABI tags.
    
           **-Wctor-dtor-privacy**(C++ and Objective-C++ only)
               Warn when a class seems unusable because all the constructors
               or destructors in that class are private, and it has neither
               friends nor public static member functions.  Also warn if
               there are no non-private methods, and there's at least one
               private member function that isn't a constructor or
               destructor.
    
           **-Wdelete-non-virtual-dtor**(C++ and Objective-C++ only)
               Warn when "delete" is used to destroy an instance of a class
               that has virtual functions and non-virtual destructor. It is
               unsafe to delete an instance of a derived class through a
               pointer to a base class if the base class does not have a
               virtual destructor.  This warning is enabled by **-Wall**.
    
           **-Wdeprecated-copy**(C++ and Objective-C++ only)
               Warn that the implicit declaration of a copy constructor or
               copy assignment operator is deprecated if the class has a
               user-provided copy constructor or copy assignment operator, in
               C++11 and up.  This warning is enabled by **-Wextra**.  With
               **-Wdeprecated-copy-dtor** , also deprecate if the class has a
               user-provided destructor.
    
           **-Wno-init-list-lifetime**(C++ and Objective-C++ only)
               Do not warn about uses of "std::initializer_list" that are
               likely to result in dangling pointers.  Since the underlying
               array for an "initializer_list" is handled like a normal C++
               temporary object, it is easy to inadvertently keep a pointer
               to the array past the end of the array's lifetime.  For
               example:
    
               *   If a function returns a temporary "initializer_list", or a
                   local "initializer_list" variable, the array's lifetime
                   ends at the end of the return statement, so the value
                   returned has a dangling pointer.
    
               *   If a new-expression creates an "initializer_list", the
                   array only lives until the end of the enclosing full-
                   expression, so the "initializer_list" in the heap has a
                   dangling pointer.
    
               *   When an "initializer_list" variable is assigned from a
                   brace-enclosed initializer list, the temporary array
                   created for the right side of the assignment only lives
                   until the end of the full-expression, so at the next
                   statement the "initializer_list" variable has a dangling
                   pointer.
    
                           // li's initial underlying array lives as long as li
                           std::initializer_list<int> li = { 1,2,3 };
                           // assignment changes li to point to a temporary array
                           li = { 4, 5 };
                           // now the temporary is gone and li has a dangling pointer
                           int i = li.begin()[0] // undefined behavior
    
               *   When a list constructor stores the "begin" pointer from
                   the "initializer_list" argument, this doesn't extend the
                   lifetime of the array, so if a class variable is
                   constructed from a temporary "initializer_list", the
                   pointer is left dangling by the end of the variable
                   declaration statement.
    
           **-Wliteral-suffix**(C++ and Objective-C++ only)
               Warn when a string or character literal is followed by a ud-
               suffix which does not begin with an underscore.  As a
               conforming extension, GCC treats such suffixes as separate
               preprocessing tokens in order to maintain backwards
               compatibility with code that uses formatting macros from
               "<inttypes.h>".  For example:
    
                       #define __STDC_FORMAT_MACROS
                       #include <inttypes.h>
                       #include <stdio.h>
    
                       int main() {
                         int64_t i64 = 123;
                         printf("My int64: %" PRId64"\n", i64);
                       }
    
               In this case, "PRId64" is treated as a separate preprocessing
               token.
    
               Additionally, warn when a user-defined literal operator is
               declared with a literal suffix identifier that doesn't begin
               with an underscore. Literal suffix identifiers that don't
               begin with an underscore are reserved for future
               standardization.
    
               This warning is enabled by default.
    
           **-Wlto-type-mismatch**
               During the link-time optimization warn about type mismatches
               in global declarations from different compilation units.
               Requires **-flto** to be enabled.  Enabled by default.
    
           **-Wno-narrowing**(C++ and Objective-C++ only)
               For C++11 and later standards, narrowing conversions are
               diagnosed by default, as required by the standard.  A
               narrowing conversion from a constant produces an error, and a
               narrowing conversion from a non-constant produces a warning,
               but **-Wno-narrowing** suppresses the diagnostic.  Note that this
               does not affect the meaning of well-formed code; narrowing
               conversions are still considered ill-formed in SFINAE
               contexts.
    
               With **-Wnarrowing** in C++98, warn when a narrowing conversion
               prohibited by C++11 occurs within **{ }** , e.g.
    
                       int i = { 2.2 }; // error: narrowing from double to int
    
               This flag is included in **-Wall** and **-Wc++11-compat**.
    
           **-Wnoexcept**(C++ and Objective-C++ only)
               Warn when a noexcept-expression evaluates to false because of
               a call to a function that does not have a non-throwing
               exception specification (i.e. "throw()" or "noexcept") but is
               known by the compiler to never throw an exception.
    
           **-Wnoexcept-type**(C++ and Objective-C++ only)
               Warn if the C++17 feature making "noexcept" part of a function
               type changes the mangled name of a symbol relative to C++14.
               Enabled by **-Wabi** and **-Wc++17-compat**.
    
               As an example:
    
                       template <class T> void f(T t) { t(); };
                       void g() noexcept;
                       void h() { f(g); }
    
               In C++14, "f" calls "f<void(*)()>", but in C++17 it calls
               "f<void(*)()noexcept>".
    
           **-Wclass-memaccess**(C++ and Objective-C++ only)
               Warn when the destination of a call to a raw memory function
               such as "memset" or "memcpy" is an object of class type, and
               when writing into such an object might bypass the class non-
               trivial or deleted constructor or copy assignment, violate
               const-correctness or encapsulation, or corrupt virtual table
               pointers.  Modifying the representation of such objects may
               violate invariants maintained by member functions of the
               class.  For example, the call to "memset" below is undefined
               because it modifies a non-trivial class object and is,
               therefore, diagnosed.  The safe way to either initialize or
               clear the storage of objects of such types is by using the
               appropriate constructor or assignment operator, if one is
               available.
    
                       std::string str = "abc";
                       memset (&str, 0, sizeof str);
    
               The **-Wclass-memaccess** option is enabled by **-Wall**.  Explicitly
               casting the pointer to the class object to "void *" or to a
               type that can be safely accessed by the raw memory function
               suppresses the warning.
    
           **-Wnon-virtual-dtor**(C++ and Objective-C++ only)
               Warn when a class has virtual functions and an accessible non-
               virtual destructor itself or in an accessible polymorphic base
               class, in which case it is possible but unsafe to delete an
               instance of a derived class through a pointer to the class
               itself or base class.  This warning is automatically enabled
               if **-Weffc++** is specified.
    
           **-Wregister**(C++ and Objective-C++ only)
               Warn on uses of the "register" storage class specifier, except
               when it is part of the GNU **Explicit Register Variables**
               extension.  The use of the "register" keyword as storage class
               specifier has been deprecated in C++11 and removed in C++17.
               Enabled by default with **-std=c++17**.
    
           **-Wreorder**(C++ and Objective-C++ only)
               Warn when the order of member initializers given in the code
               does not match the order in which they must be executed.  For
               instance:
    
                       struct A {
                         int i;
                         int j;
                         A(): j (0), i (1) { }
                       };
    
               The compiler rearranges the member initializers for "i" and
               "j" to match the declaration order of the members, emitting a
               warning to that effect.  This warning is enabled by **-Wall**.
    
           **-Wno-pessimizing-move**(C++ and Objective-C++ only)
               This warning warns when a call to "std::move" prevents copy
               elision.  A typical scenario when copy elision can occur is
               when returning in a function with a class return type, when
               the expression being returned is the name of a non-volatile
               automatic object, and is not a function parameter, and has the
               same type as the function return type.
    
                       struct T {
                       ...
                       };
                       T fn()
                       {
                         T t;
                         ...
                         return std::move (t);
                       }
    
               But in this example, the "std::move" call prevents copy
               elision.
    
               This warning is enabled by **-Wall**.
    
           **-Wno-redundant-move**(C++ and Objective-C++ only)
               This warning warns about redundant calls to "std::move"; that
               is, when a move operation would have been performed even
               without the "std::move" call.  This happens because the
               compiler is forced to treat the object as if it were an rvalue
               in certain situations such as returning a local variable,
               where copy elision isn't applicable.  Consider:
    
                       struct T {
                       ...
                       };
                       T fn(T t)
                       {
                         ...
                         return std::move (t);
                       }
    
               Here, the "std::move" call is redundant.  Because G++
               implements Core Issue 1579, another example is:
    
                       struct T { // convertible to U
                       ...
                       };
                       struct U {
                       ...
                       };
                       U fn()
                       {
                         T t;
                         ...
                         return std::move (t);
                       }
    
               In this example, copy elision isn't applicable because the
               type of the expression being returned and the function return
               type differ, yet G++ treats the return value as if it were
               designated by an rvalue.
    
               This warning is enabled by **-Wextra**.
    
           **-fext-numeric-literals**(C++ and Objective-C++ only)
               Accept imaginary, fixed-point, or machine-defined literal
               number suffixes as GNU extensions.  When this option is turned
               off these suffixes are treated as C++11 user-defined literal
               numeric suffixes.  This is on by default for all pre-C++11
               dialects and all GNU dialects: **-std=c++98** , **-std=gnu++98** ,
               **-std=gnu++11** , **-std=gnu++14**.  This option is off by default for
               ISO C++11 onwards (**-std=c++11** , ...).
    
           The following **-W...** options are not affected by **-Wall**.
    
           **-Weffc++**(C++ and Objective-C++ only)
               Warn about violations of the following style guidelines from
               Scott Meyers' _Effective C++_ series of books:
    
               *   Define a copy constructor and an assignment operator for
                   classes with dynamically-allocated memory.
    
               *   Prefer initialization to assignment in constructors.
    
               *   Have "operator=" return a reference to *this.
    
               *   Don't try to return a reference when you must return an
                   object.
    
               *   Distinguish between prefix and postfix forms of increment
                   and decrement operators.
    
               *   Never overload "&&", "||", or ",".
    
               This option also enables **-Wnon-virtual-dtor** , which is also one
               of the effective C++ recommendations.  However, the check is
               extended to warn about the lack of virtual destructor in
               accessible non-polymorphic bases classes too.
    
               When selecting this option, be aware that the standard library
               headers do not obey all of these guidelines; use **grep -v** to
               filter out those warnings.
    
           **-Wstrict-null-sentinel**(C++ and Objective-C++ only)
               Warn about the use of an uncasted "NULL" as sentinel.  When
               compiling only with GCC this is a valid sentinel, as "NULL" is
               defined to "__null".  Although it is a null pointer constant
               rather than a null pointer, it is guaranteed to be of the same
               size as a pointer.  But this use is not portable across
               different compilers.
    
           **-Wno-non-template-friend**(C++ and Objective-C++ only)
               Disable warnings when non-template friend functions are
               declared within a template.  In very old versions of GCC that
               predate implementation of the ISO standard, declarations such
               as **friend int foo(int)** , where the name of the friend is an
               unqualified-id, could be interpreted as a particular
               specialization of a template function; the warning exists to
               diagnose compatibility problems, and is enabled by default.
    
           **-Wold-style-cast**(C++ and Objective-C++ only)
               Warn if an old-style (C-style) cast to a non-void type is used
               within a C++ program.  The new-style casts ("dynamic_cast",
               "static_cast", "reinterpret_cast", and "const_cast") are less
               vulnerable to unintended effects and much easier to search
               for.
    
           **-Woverloaded-virtual**(C++ and Objective-C++ only)
               Warn when a function declaration hides virtual functions from
               a base class.  For example, in:
    
                       struct A {
                         virtual void f();
                       };
    
                       struct B: public A {
                         void f(int);
                       };
    
               the "A" class version of "f" is hidden in "B", and code like:
    
                       B* b;
                       b->f();
    
               fails to compile.
    
           **-Wno-pmf-conversions**(C++ and Objective-C++ only)
               Disable the diagnostic for converting a bound pointer to
               member function to a plain pointer.
    
           **-Wsign-promo**(C++ and Objective-C++ only)
               Warn when overload resolution chooses a promotion from
               unsigned or enumerated type to a signed type, over a
               conversion to an unsigned type of the same size.  Previous
               versions of G++ tried to preserve unsignedness, but the
               standard mandates the current behavior.
    
           **-Wtemplates**(C++ and Objective-C++ only)
               Warn when a primary template declaration is encountered.  Some
               coding rules disallow templates, and this may be used to
               enforce that rule.  The warning is inactive inside a system
               header file, such as the STL, so one can still use the STL.
               One may also instantiate or specialize templates.
    
           **-Wmultiple-inheritance**(C++ and Objective-C++ only)
               Warn when a class is defined with multiple direct base
               classes.  Some coding rules disallow multiple inheritance, and
               this may be used to enforce that rule.  The warning is
               inactive inside a system header file, such as the STL, so one
               can still use the STL.  One may also define classes that
               indirectly use multiple inheritance.
    
           **-Wvirtual-inheritance**
               Warn when a class is defined with a virtual direct base class.
               Some coding rules disallow multiple inheritance, and this may
               be used to enforce that rule.  The warning is inactive inside
               a system header file, such as the STL, so one can still use
               the STL.  One may also define classes that indirectly use
               virtual inheritance.
    
           **-Wnamespaces**
               Warn when a namespace definition is opened.  Some coding rules
               disallow namespaces, and this may be used to enforce that
               rule.  The warning is inactive inside a system header file,
               such as the STL, so one can still use the STL.  One may also
               use using directives and qualified names.
    
           **-Wno-terminate**(C++ and Objective-C++ only)
               Disable the warning about a throw-expression that will
               immediately result in a call to "terminate".
    
           **-Wno-class-conversion**(C++ and Objective-C++ only)
               Disable the warning about the case when a conversion function
               converts an object to the same type, to a base class of that
               type, or to void; such a conversion function will never be
               called.
    
       **Options Controlling Objective-C and Objective-C++ Dialects**
           (NOTE: This manual does not describe the Objective-C and
           Objective-C++ languages themselves.
    
           This section describes the command-line options that are only
           meaningful for Objective-C and Objective-C++ programs.  You can
           also use most of the language-independent GNU compiler options.
           For example, you might compile a file _some_class.m_ like this:
    
                   gcc -g -fgnu-runtime -O -c some_class.m
    
           In this example, **-fgnu-runtime** is an option meant only for
           Objective-C and Objective-C++ programs; you can use the other
           options with any language supported by GCC.
    
           Note that since Objective-C is an extension of the C language,
           Objective-C compilations may also use options specific to the C
           front-end (e.g., **-Wtraditional**).  Similarly, Objective-C++
           compilations may use C++-specific options (e.g., **-Wabi**).
    
           Here is a list of options that are _only_ for compiling Objective-C
           and Objective-C++ programs:
    
           **-fconstant-string-class=**_class-name_
               Use _class-name_ as the name of the class to instantiate for
               each literal string specified with the syntax "@"..."".  The
               default class name is "NXConstantString" if the GNU runtime is
               being used, and "NSConstantString" if the NeXT runtime is
               being used (see below).  The **-fconstant-cfstrings** option, if
               also present, overrides the **-fconstant-string-class** setting
               and cause "@"..."" literals to be laid out as constant
               CoreFoundation strings.
    
           **-fgnu-runtime**
               Generate object code compatible with the standard GNU
               Objective-C runtime.  This is the default for most types of
               systems.
    
           **-fnext-runtime**
               Generate output compatible with the NeXT runtime.  This is the
               default for NeXT-based systems, including Darwin and Mac OS X.
               The macro "__NEXT_RUNTIME__" is predefined if (and only if)
               this option is used.
    
           **-fno-nil-receivers**
               Assume that all Objective-C message dispatches ("[receiver
               message:arg]") in this translation unit ensure that the
               receiver is not "nil".  This allows for more efficient entry
               points in the runtime to be used.  This option is only
               available in conjunction with the NeXT runtime and ABI version
               0 or 1.
    
           **-fobjc-abi-version=**_n_
               Use version _n_ of the Objective-C ABI for the selected runtime.
               This option is currently supported only for the NeXT runtime.
               In that case, Version 0 is the traditional (32-bit) ABI
               without support for properties and other Objective-C 2.0
               additions.  Version 1 is the traditional (32-bit) ABI with
               support for properties and other Objective-C 2.0 additions.
               Version 2 is the modern (64-bit) ABI.  If nothing is
               specified, the default is Version 0 on 32-bit target machines,
               and Version 2 on 64-bit target machines.
    
           **-fobjc-call-cxx-cdtors**
               For each Objective-C class, check if any of its instance
               variables is a C++ object with a non-trivial default
               constructor.  If so, synthesize a special "- (id)
               .cxx_construct" instance method which runs non-trivial default
               constructors on any such instance variables, in order, and
               then return "self".  Similarly, check if any instance variable
               is a C++ object with a non-trivial destructor, and if so,
               synthesize a special "- (void) .cxx_destruct" method which
               runs all such default destructors, in reverse order.
    
               The "- (id) .cxx_construct" and "- (void) .cxx_destruct"
               methods thusly generated only operate on instance variables
               declared in the current Objective-C class, and not those
               inherited from superclasses.  It is the responsibility of the
               Objective-C runtime to invoke all such methods in an object's
               inheritance hierarchy.  The "- (id) .cxx_construct" methods
               are invoked by the runtime immediately after a new object
               instance is allocated; the "- (void) .cxx_destruct" methods
               are invoked immediately before the runtime deallocates an
               object instance.
    
               As of this writing, only the NeXT runtime on Mac OS X 10.4 and
               later has support for invoking the "- (id) .cxx_construct" and
               "- (void) .cxx_destruct" methods.
    
           **-fobjc-direct-dispatch**
               Allow fast jumps to the message dispatcher.  On Darwin this is
               accomplished via the comm page.
    
           **-fobjc-exceptions**
               Enable syntactic support for structured exception handling in
               Objective-C, similar to what is offered by C++.  This option
               is required to use the Objective-C keywords @try, @throw,
               @catch, @finally and @synchronized.  This option is available
               with both the GNU runtime and the NeXT runtime (but not
               available in conjunction with the NeXT runtime on Mac OS X
               10.2 and earlier).
    
           **-fobjc-gc**
               Enable garbage collection (GC) in Objective-C and
               Objective-C++ programs.  This option is only available with
               the NeXT runtime; the GNU runtime has a different garbage
               collection implementation that does not require special
               compiler flags.
    
           **-fobjc-nilcheck**
               For the NeXT runtime with version 2 of the ABI, check for a
               nil receiver in method invocations before doing the actual
               method call.  This is the default and can be disabled using
               **-fno-objc-nilcheck**.  Class methods and super calls are never
               checked for nil in this way no matter what this flag is set
               to.  Currently this flag does nothing when the GNU runtime, or
               an older version of the NeXT runtime ABI, is used.
    
           **-fobjc-std=objc1**
               Conform to the language syntax of Objective-C 1.0, the
               language recognized by GCC 4.0.  This only affects the
               Objective-C additions to the C/C++ language; it does not
               affect conformance to C/C++ standards, which is controlled by
               the separate C/C++ dialect option flags.  When this option is
               used with the Objective-C or Objective-C++ compiler, any
               Objective-C syntax that is not recognized by GCC 4.0 is
               rejected.  This is useful if you need to make sure that your
               Objective-C code can be compiled with older versions of GCC.
    
           **-freplace-objc-classes**
               Emit a special marker instructing _**ld**(1) _not to statically link
               in the resulting object file, and allow _**dyld**(1) _to load it in
               at run time instead.  This is used in conjunction with the
               Fix-and-Continue debugging mode, where the object file in
               question may be recompiled and dynamically reloaded in the
               course of program execution, without the need to restart the
               program itself.  Currently, Fix-and-Continue functionality is
               only available in conjunction with the NeXT runtime on Mac OS
               X 10.3 and later.
    
           **-fzero-link**
               When compiling for the NeXT runtime, the compiler ordinarily
               replaces calls to "objc_getClass("...")" (when the name of the
               class is known at compile time) with static class references
               that get initialized at load time, which improves run-time
               performance.  Specifying the **-fzero-link** flag suppresses this
               behavior and causes calls to "objc_getClass("...")"  to be
               retained.  This is useful in Zero-Link debugging mode, since
               it allows for individual class implementations to be modified
               during program execution.  The GNU runtime currently always
               retains calls to "objc_get_class("...")"  regardless of
               command-line options.
    
           **-fno-local-ivars**
               By default instance variables in Objective-C can be accessed
               as if they were local variables from within the methods of the
               class they're declared in.  This can lead to shadowing between
               instance variables and other variables declared either locally
               inside a class method or globally with the same name.
               Specifying the **-fno-local-ivars** flag disables this behavior
               thus avoiding variable shadowing issues.
    
           **-fivar-visibility=**[**public** |**protected** |**private** |**package**]
               Set the default instance variable visibility to the specified
               option so that instance variables declared outside the scope
               of any access modifier directives default to the specified
               visibility.
    
           **-gen-decls**
               Dump interface declarations for all classes seen in the source
               file to a file named _sourcename.decl_.
    
           **-Wassign-intercept**(Objective-C and Objective-C++ only)
               Warn whenever an Objective-C assignment is being intercepted
               by the garbage collector.
    
           **-Wno-protocol**(Objective-C and Objective-C++ only)
               If a class is declared to implement a protocol, a warning is
               issued for every method in the protocol that is not
               implemented by the class.  The default behavior is to issue a
               warning for every method not explicitly implemented in the
               class, even if a method implementation is inherited from the
               superclass.  If you use the **-Wno-protocol** option, then methods
               inherited from the superclass are considered to be
               implemented, and no warning is issued for them.
    
           **-Wselector**(Objective-C and Objective-C++ only)
               Warn if multiple methods of different types for the same
               selector are found during compilation.  The check is performed
               on the list of methods in the final stage of compilation.
               Additionally, a check is performed for each selector appearing
               in a "@selector(...)"  expression, and a corresponding method
               for that selector has been found during compilation.  Because
               these checks scan the method table only at the end of
               compilation, these warnings are not produced if the final
               stage of compilation is not reached, for example because an
               error is found during compilation, or because the
               **-fsyntax-only** option is being used.
    
           **-Wstrict-selector-match**(Objective-C and Objective-C++ only)
               Warn if multiple methods with differing argument and/or return
               types are found for a given selector when attempting to send a
               message using this selector to a receiver of type "id" or
               "Class".  When this flag is off (which is the default
               behavior), the compiler omits such warnings if any differences
               found are confined to types that share the same size and
               alignment.
    
           **-Wundeclared-selector**(Objective-C and Objective-C++ only)
               Warn if a "@selector(...)" expression referring to an
               undeclared selector is found.  A selector is considered
               undeclared if no method with that name has been declared
               before the "@selector(...)" expression, either explicitly in
               an @interface or @protocol declaration, or implicitly in an
               @implementation section.  This option always performs its
               checks as soon as a "@selector(...)" expression is found,
               while **-Wselector** only performs its checks in the final stage
               of compilation.  This also enforces the coding style
               convention that methods and selectors must be declared before
               being used.
    
           **-print-objc-runtime-info**
               Generate C header describing the largest structure that is
               passed by value, if any.
    
       **Options to Control Diagnostic Messages Formatting**
           Traditionally, diagnostic messages have been formatted
           irrespective of the output device's aspect (e.g. its width, ...).
           You can use the options described below to control the formatting
           algorithm for diagnostic messages, e.g. how many characters per
           line, how often source location information should be reported.
           Note that some language front ends may not honor these options.
    
           **-fmessage-length=**_n_
               Try to format error messages so that they fit on lines of
               about _n_ characters.  If _n_ is zero, then no line-wrapping is
               done; each error message appears on a single line.  This is
               the default for all front ends.
    
               Note - this option also affects the display of the **#error** and
               **#warning** pre-processor directives, and the **deprecated**
               function/type/variable attribute.  It does not however affect
               the **pragma GCC warning** and **pragma GCC error** pragmas.
    
           **-fdiagnostics-show-location=once**
               Only meaningful in line-wrapping mode.  Instructs the
               diagnostic messages reporter to emit source location
               information _once_ ; that is, in case the message is too long to
               fit on a single physical line and has to be wrapped, the
               source location won't be emitted (as prefix) again, over and
               over, in subsequent continuation lines.  This is the default
               behavior.
    
           **-fdiagnostics-show-location=every-line**
               Only meaningful in line-wrapping mode.  Instructs the
               diagnostic messages reporter to emit the same source location
               information (as prefix) for physical lines that result from
               the process of breaking a message which is too long to fit on
               a single line.
    
           **-fdiagnostics-color[=**_WHEN_**]**
           **-fno-diagnostics-color**
               Use color in diagnostics.  _WHEN_ is **never** , **always** , or **auto**.
               The default depends on how the compiler has been configured,
               it can be any of the above _WHEN_ options or also **never** if
               **GCC_COLORS** environment variable isn't present in the
               environment, and **auto** otherwise.  **auto** means to use color only
               when the standard error is a terminal.  The forms
               **-fdiagnostics-color** and **-fno-diagnostics-color** are aliases for
               **-fdiagnostics-color=always** and **-fdiagnostics-color=never** ,
               respectively.
    
               The colors are defined by the environment variable **GCC_COLORS**.
               Its value is a colon-separated list of capabilities and Select
               Graphic Rendition (SGR) substrings. SGR commands are
               interpreted by the terminal or terminal emulator.  (See the
               section in the documentation of your text terminal for
               permitted values and their meanings as character attributes.)
               These substring values are integers in decimal representation
               and can be concatenated with semicolons.  Common values to
               concatenate include **1** for bold, **4** for underline, **5** for blink,
               **7** for inverse, **39** for default foreground color, **30** to **37** for
               foreground colors, **90** to **97** for 16-color mode foreground
               colors, **38;5;0** to **38;5;255** for 88-color and 256-color modes
               foreground colors, **49** for default background color, **40** to **47**
               for background colors, **100** to **107** for 16-color mode background
               colors, and **48;5;0** to **48;5;255** for 88-color and 256-color
               modes background colors.
    
               The default **GCC_COLORS** is
    
                       error=01;31:warning=01;35:note=01;36:range1=32:range2=34:locus=01:\
                       quote=01:fixit-insert=32:fixit-delete=31:\
                       diff-filename=01:diff-hunk=32:diff-delete=31:diff-insert=32:\
                       type-diff=01;32
    
               where **01;31** is bold red, **01;35** is bold magenta, **01;36** is bold
               cyan, **32** is green, **34** is blue, **01** is bold, and **31** is red.
               Setting **GCC_COLORS** to the empty string disables colors.
               Supported capabilities are as follows.
    
               "error="
                   SGR substring for error: markers.
    
               "warning="
                   SGR substring for warning: markers.
    
               "note="
                   SGR substring for note: markers.
    
               "range1="
                   SGR substring for first additional range.
    
               "range2="
                   SGR substring for second additional range.
    
               "locus="
                   SGR substring for location information, **file:line** or
                   **file:line:column** etc.
    
               "quote="
                   SGR substring for information printed within quotes.
    
               "fixit-insert="
                   SGR substring for fix-it hints suggesting text to be
                   inserted or replaced.
    
               "fixit-delete="
                   SGR substring for fix-it hints suggesting text to be
                   deleted.
    
               "diff-filename="
                   SGR substring for filename headers within generated
                   patches.
    
               "diff-hunk="
                   SGR substring for the starts of hunks within generated
                   patches.
    
               "diff-delete="
                   SGR substring for deleted lines within generated patches.
    
               "diff-insert="
                   SGR substring for inserted lines within generated patches.
    
               "type-diff="
                   SGR substring for highlighting mismatching types within
                   template arguments in the C++ frontend.
    
           **-fno-diagnostics-show-option**
               By default, each diagnostic emitted includes text indicating
               the command-line option that directly controls the diagnostic
               (if such an option is known to the diagnostic machinery).
               Specifying the **-fno-diagnostics-show-option** flag suppresses
               that behavior.
    
           **-fno-diagnostics-show-caret**
               By default, each diagnostic emitted includes the original
               source line and a caret **^** indicating the column.  This option
               suppresses this information.  The source line is truncated to
               _n_ characters, if the **-fmessage-length=n** option is given.  When
               the output is done to the terminal, the width is limited to
               the width given by the **COLUMNS** environment variable or, if not
               set, to the terminal width.
    
           **-fno-diagnostics-show-labels**
               By default, when printing source code (via
               **-fdiagnostics-show-caret**), diagnostics can label ranges of
               source code with pertinent information, such as the types of
               expressions:
    
                           printf ("foo %s bar", long_i + long_j);
                                        ~^       ~~~~~~~~~~~~~~~
                                         |              |
                                         char *         long int
    
               This option suppresses the printing of these labels (in the
               example above, the vertical bars and the "char *" and "long
               int" text).
    
           **-fno-diagnostics-show-line-numbers**
               By default, when printing source code (via
               **-fdiagnostics-show-caret**), a left margin is printed, showing
               line numbers.  This option suppresses this left margin.
    
           **-fdiagnostics-minimum-margin-width=**_width_
               This option controls the minimum width of the left margin
               printed by **-fdiagnostics-show-line-numbers**.  It defaults to 6.
    
           **-fdiagnostics-parseable-fixits**
               Emit fix-it hints in a machine-parseable format, suitable for
               consumption by IDEs.  For each fix-it, a line will be printed
               after the relevant diagnostic, starting with the string "fix-
               it:".  For example:
    
                       fix-it:"test.c":{45:3-45:21}:"gtk_widget_show_all"
    
               The location is expressed as a half-open range, expressed as a
               count of bytes, starting at byte 1 for the initial column.  In
               the above example, bytes 3 through 20 of line 45 of "test.c"
               are to be replaced with the given string:
    
                       00000000011111111112222222222
                       12345678901234567890123456789
                         gtk_widget_showall (dlg);
                         ^^^^^^^^^^^^^^^^^^
                         gtk_widget_show_all
    
               The filename and replacement string escape backslash as "\\",
               tab as "\t", newline as "\n", double quotes as "\"", non-
               printable characters as octal (e.g. vertical tab as "\013").
    
               An empty replacement string indicates that the given range is
               to be removed.  An empty range (e.g. "45:3-45:3") indicates
               that the string is to be inserted at the given position.
    
           **-fdiagnostics-generate-patch**
               Print fix-it hints to stderr in unified diff format, after any
               diagnostics are printed.  For example:
    
                       --- test.c
                       +++ test.c
                       @ -42,5 +42,5 @
    
                        void show_cb(GtkDialog *dlg)
                        {
                       -  gtk_widget_showall(dlg);
                       +  gtk_widget_show_all(dlg);
                        }
    
               The diff may or may not be colorized, following the same rules
               as for diagnostics (see **-fdiagnostics-color**).
    
           **-fdiagnostics-show-template-tree**
               In the C++ frontend, when printing diagnostics showing
               mismatching template types, such as:
    
                         could not convert 'std::map<int, std::vector<double> >()'
                           from 'map<[...],vector<double>>' to 'map<[...],vector<float>>
    
               the **-fdiagnostics-show-template-tree** flag enables printing a
               tree-like structure showing the common and differing parts of
               the types, such as:
    
                         map<
                           [...],
                           vector<
                             [double != float]>>
    
               The parts that differ are highlighted with color ("double" and
               "float" in this case).
    
           **-fno-elide-type**
               By default when the C++ frontend prints diagnostics showing
               mismatching template types, common parts of the types are
               printed as "[...]" to simplify the error message.  For
               example:
    
                         could not convert 'std::map<int, std::vector<double> >()'
                           from 'map<[...],vector<double>>' to 'map<[...],vector<float>>
    
               Specifying the **-fno-elide-type** flag suppresses that behavior.
               This flag also affects the output of the
               **-fdiagnostics-show-template-tree** flag.
    
           **-fno-show-column**
               Do not print column numbers in diagnostics.  This may be
               necessary if diagnostics are being scanned by a program that
               does not understand the column numbers, such as **dejagnu**.
    
           **-fdiagnostics-format=**_FORMAT_
               Select a different format for printing diagnostics.  _FORMAT_ is
               **text** or **json**.  The default is **text**.
    
               The **json** format consists of a top-level JSON array containing
               JSON objects representing the diagnostics.
    
               The JSON is emitted as one line, without formatting; the
               examples below have been formatted for clarity.
    
               Diagnostics can have child diagnostics.  For example, this
               error and note:
    
                       misleading-indentation.c:15:3: warning: this 'if' clause does not
                         guard... [-Wmisleading-indentation]
                          15 |   if (flag)
                             |   ^~
                       misleading-indentation.c:17:5: note: ...this statement, but the latter
                         is misleadingly indented as if it were guarded by the 'if'
                          17 |     y = 2;
                             |     ^
    
               might be printed in JSON form (after formatting) like this:
    
                       [
                           {
                               "kind": "warning",
                               "locations": [
                                   {
                                       "caret": {
                                           "column": 3,
                                           "file": "misleading-indentation.c",
                                           "line": 15
                                       },
                                       "finish": {
                                           "column": 4,
                                           "file": "misleading-indentation.c",
                                           "line": 15
                                       }
                                   }
                               ],
                               "message": "this \u2018if\u2019 clause does not guard...",
                               "option": "-Wmisleading-indentation",
                               "children": [
                                   {
                                       "kind": "note",
                                       "locations": [
                                           {
                                               "caret": {
                                                   "column": 5,
                                                   "file": "misleading-indentation.c",
                                                   "line": 17
                                               }
                                           }
                                       ],
                                       "message": "...this statement, but the latter is ..."
                                   }
                               ]
                           },
                           ...
                       ]
    
               where the "note" is a child of the "warning".
    
               A diagnostic has a "kind".  If this is "warning", then there
               is an "option" key describing the command-line option
               controlling the warning.
    
               A diagnostic can contain zero or more locations.  Each
               location has up to three positions within it: a "caret"
               position and optional "start" and "finish" positions.  A
               location can also have an optional "label" string.  For
               example, this error:
    
                       bad-binary-ops.c:64:23: error: invalid operands to binary + (have 'S' {aka
                          'struct s'} and 'T' {aka 'struct t'})
                          64 |   return callee_4a () + callee_4b ();
                             |          ~~~~~~~~~~~~ ^ ~~~~~~~~~~~~
                             |          |              |
                             |          |              T {aka struct t}
                             |          S {aka struct s}
    
               has three locations.  Its primary location is at the "+" token
               at column 23.  It has two secondary locations, describing the
               left and right-hand sides of the expression, which have
               labels.  It might be printed in JSON form as:
    
                           {
                               "children": [],
                               "kind": "error",
                               "locations": [
                                   {
                                       "caret": {
                                           "column": 23, "file": "bad-binary-ops.c", "line": 64
                                       }
                                   },
                                   {
                                       "caret": {
                                           "column": 10, "file": "bad-binary-ops.c", "line": 64
                                       },
                                       "finish": {
                                           "column": 21, "file": "bad-binary-ops.c", "line": 64
                                       },
                                       "label": "S {aka struct s}"
                                   },
                                   {
                                       "caret": {
                                           "column": 25, "file": "bad-binary-ops.c", "line": 64
                                       },
                                       "finish": {
                                           "column": 36, "file": "bad-binary-ops.c", "line": 64
                                       },
                                       "label": "T {aka struct t}"
                                   }
                               ],
                               "message": "invalid operands to binary + ..."
                           }
    
               If a diagnostic contains fix-it hints, it has a "fixits"
               array, consisting of half-open intervals, similar to the
               output of **-fdiagnostics-parseable-fixits**.  For example, this
               diagnostic with a replacement fix-it hint:
    
                       demo.c:8:15: error: 'struct s' has no member named 'colour'; did you
                         mean 'color'?
                           8 |   return ptr->colour;
                             |               ^~~~~~
                             |               color
    
               might be printed in JSON form as:
    
                           {
                               "children": [],
                               "fixits": [
                                   {
                                       "next": {
                                           "column": 21,
                                           "file": "demo.c",
                                           "line": 8
                                       },
                                       "start": {
                                           "column": 15,
                                           "file": "demo.c",
                                           "line": 8
                                       },
                                       "string": "color"
                                   }
                               ],
                               "kind": "error",
                               "locations": [
                                   {
                                       "caret": {
                                           "column": 15,
                                           "file": "demo.c",
                                           "line": 8
                                       },
                                       "finish": {
                                           "column": 20,
                                           "file": "demo.c",
                                           "line": 8
                                       }
                                   }
                               ],
                               "message": "\u2018struct s\u2019 has no member named ..."
                           }
    
               where the fix-it hint suggests replacing the text from "start"
               up to but not including "next" with "string"'s value.
               Deletions are expressed via an empty value for "string",
               insertions by having "start" equal "next".
    
       **Options to Request or Suppress Warnings**
           Warnings are diagnostic messages that report constructions that
           are not inherently erroneous but that are risky or suggest there
           may have been an error.
    
           The following language-independent options do not enable specific
           warnings but control the kinds of diagnostics produced by GCC.
    
           **-fsyntax-only**
               Check the code for syntax errors, but don't do anything beyond
               that.
    
           **-fmax-errors=**_n_
               Limits the maximum number of error messages to _n_ , at which
               point GCC bails out rather than attempting to continue
               processing the source code.  If _n_ is 0 (the default), there is
               no limit on the number of error messages produced.  If
               **-Wfatal-errors** is also specified, then **-Wfatal-errors** takes
               precedence over this option.
    
           **-w** Inhibit all warning messages.
    
           **-Werror**
               Make all warnings into errors.
    
           **-Werror=**
               Make the specified warning into an error.  The specifier for a
               warning is appended; for example **-Werror=switch** turns the
               warnings controlled by **-Wswitch** into errors.  This switch
               takes a negative form, to be used to negate **-Werror** for
               specific warnings; for example **-Wno-error=switch** makes
               **-Wswitch** warnings not be errors, even when **-Werror** is in
               effect.
    
               The warning message for each controllable warning includes the
               option that controls the warning.  That option can then be
               used with **-Werror=** and **-Wno-error=** as described above.
               (Printing of the option in the warning message can be disabled
               using the **-fno-diagnostics-show-option** flag.)
    
               Note that specifying **-Werror=**_foo_ automatically implies **-W** _foo_.
               However, **-Wno-error=**_foo_ does not imply anything.
    
           **-Wfatal-errors**
               This option causes the compiler to abort compilation on the
               first error occurred rather than trying to keep going and
               printing further error messages.
    
           You can request many specific warnings with options beginning with
           **-W** , for example **-Wimplicit** to request warnings on implicit
           declarations.  Each of these specific warning options also has a
           negative form beginning **-Wno-** to turn off warnings; for example,
           **-Wno-implicit**.  This manual lists only one of the two forms,
           whichever is not the default.  For further language-specific
           options also refer to **C++ Dialect Options** and **Objective-C and**
           **Objective-C++ Dialect Options**.
    
           Some options, such as **-Wall** and **-Wextra** , turn on other options,
           such as **-Wunused** , which may turn on further options, such as
           **-Wunused-value**. The combined effect of positive and negative forms
           is that more specific options have priority over less specific
           ones, independently of their position in the command-line. For
           options of the same specificity, the last one takes effect.
           Options enabled or disabled via pragmas take effect as if they
           appeared at the end of the command-line.
    
           When an unrecognized warning option is requested (e.g.,
           **-Wunknown-warning**), GCC emits a diagnostic stating that the option
           is not recognized.  However, if the **-Wno-** form is used, the
           behavior is slightly different: no diagnostic is produced for
           **-Wno-unknown-warning** unless other diagnostics are being produced.
           This allows the use of new **-Wno-** options with old compilers, but
           if something goes wrong, the compiler warns that an unrecognized
           option is present.
    
           The effectiveness of some warnings depends on optimizations also
           being enabled. For example **-Wsuggest-final-types** is more effective
           with link-time optimization and **-Wmaybe-uninitialized** will not
           warn at all unless optimization is enabled.
    
           **-Wpedantic**
           **-pedantic**
               Issue all the warnings demanded by strict ISO C and ISO C++;
               reject all programs that use forbidden extensions, and some
               other programs that do not follow ISO C and ISO C++.  For ISO
               C, follows the version of the ISO C standard specified by any
               **-std** option used.
    
               Valid ISO C and ISO C++ programs should compile properly with
               or without this option (though a rare few require **-ansi** or a
               **-std** option specifying the required version of ISO C).
               However, without this option, certain GNU extensions and
               traditional C and C++ features are supported as well.  With
               this option, they are rejected.
    
               **-Wpedantic** does not cause warning messages for use of the
               alternate keywords whose names begin and end with **__**.
               Pedantic warnings are also disabled in the expression that
               follows "__extension__".  However, only system header files
               should use these escape routes; application programs should
               avoid them.
    
               Some users try to use **-Wpedantic** to check programs for strict
               ISO C conformance.  They soon find that it does not do quite
               what they want: it finds some non-ISO practices, but not
               all---only those for which ISO C _requires_ a diagnostic, and
               some others for which diagnostics have been added.
    
               A feature to report any failure to conform to ISO C might be
               useful in some instances, but would require considerable
               additional work and would be quite different from **-Wpedantic**.
               We don't have plans to support such a feature in the near
               future.
    
               Where the standard specified with **-std** represents a GNU
               extended dialect of C, such as **gnu90** or **gnu99** , there is a
               corresponding _base standard_ , the version of ISO C on which the
               GNU extended dialect is based.  Warnings from **-Wpedantic** are
               given where they are required by the base standard.  (It does
               not make sense for such warnings to be given only for features
               not in the specified GNU C dialect, since by definition the
               GNU dialects of C include all features the compiler supports
               with the given option, and there would be nothing to warn
               about.)
    
           **-pedantic-errors**
               Give an error whenever the _base standard_ (see **-Wpedantic**)
               requires a diagnostic, in some cases where there is undefined
               behavior at compile-time and in some other cases that do not
               prevent compilation of programs that are valid according to
               the standard. This is not equivalent to **-Werror=pedantic** ,
               since there are errors enabled by this option and not enabled
               by the latter and vice versa.
    
           **-Wall**
               This enables all the warnings about constructions that some
               users consider questionable, and that are easy to avoid (or
               modify to prevent the warning), even in conjunction with
               macros.  This also enables some language-specific warnings
               described in **C++ Dialect Options** and **Objective-C and**
               **Objective-C++ Dialect Options**.
    
               **-Wall** turns on the following warning flags:
    
               **-Waddress -Warray-bounds=1**(only with **-O2**) **-Wbool-compare**
               **-Wbool-operation -Wc++11-compat  -Wc++14-compat -Wcatch-value**
               (C++ and Objective-C++ only) **-Wchar-subscripts -Wcomment**
               **-Wduplicate-decl-specifier**(C and Objective-C only)
               **-Wenum-compare**(in C/ObjC; this is on by default in C++)
               **-Wformat -Wint-in-bool-context -Wimplicit**(C and Objective-C
               only) **-Wimplicit-int**(C and Objective-C only)
               **-Wimplicit-function-declaration**(C and Objective-C only)
               **-Winit-self**(only for C++) **-Wlogical-not-parentheses -Wmain**
               (only for C/ObjC and unless **-ffreestanding**)
               **-Wmaybe-uninitialized -Wmemset-elt-size**
               **-Wmemset-transposed-args -Wmisleading-indentation**(only for
               C/C++) **-Wmissing-attributes -Wmissing-braces**(only for C/ObjC)
               **-Wmultistatement-macros -Wnarrowing**(only for C++) **-Wnonnull**
               **-Wnonnull-compare -Wopenmp-simd -Wparentheses**
               **-Wpessimizing-move**(only for C++) **-Wpointer-sign -Wreorder**
               **-Wrestrict -Wreturn-type -Wsequence-point -Wsign-compare**(only
               in C++) **-Wsizeof-pointer-div -Wsizeof-pointer-memaccess**
               **-Wstrict-aliasing -Wstrict-overflow=1 -Wswitch**
               **-Wtautological-compare -Wtrigraphs -Wuninitialized**
               **-Wunknown-pragmas -Wunused-function -Wunused-label**
               **-Wunused-value -Wunused-variable -Wvolatile-register-var**
    
               Note that some warning flags are not implied by **-Wall**.  Some
               of them warn about constructions that users generally do not
               consider questionable, but which occasionally you might wish
               to check for; others warn about constructions that are
               necessary or hard to avoid in some cases, and there is no
               simple way to modify the code to suppress the warning. Some of
               them are enabled by **-Wextra** but many of them must be enabled
               individually.
    
           **-Wextra**
               This enables some extra warning flags that are not enabled by
               **-Wall**. (This option used to be called **-W**.  The older name is
               still supported, but the newer name is more descriptive.)
    
               **-Wclobbered -Wcast-function-type -Wdeprecated-copy**(C++ only)
               **-Wempty-body -Wignored-qualifiers -Wimplicit-fallthrough=3**
               **-Wmissing-field-initializers -Wmissing-parameter-type**(C only)
               **-Wold-style-declaration**(C only) **-Woverride-init**
               **-Wsign-compare**(C only) **-Wredundant-move**(only for C++)
               **-Wtype-limits -Wuninitialized -Wshift-negative-value**(in C++11
               to C++17 and in C99 and newer) **-Wunused-parameter**(only with
               **-Wunused** or **-Wall**) **-Wunused-but-set-parameter**(only with
               **-Wunused** or **-Wall**)
    
               The option **-Wextra** also prints warning messages for the
               following cases:
    
               *   A pointer is compared against integer zero with "<", "<=",
                   ">", or ">=".
    
               *   (C++ only) An enumerator and a non-enumerator both appear
                   in a conditional expression.
    
               *   (C++ only) Ambiguous virtual bases.
    
               *   (C++ only) Subscripting an array that has been declared
                   "register".
    
               *   (C++ only) Taking the address of a variable that has been
                   declared "register".
    
               *   (C++ only) A base class is not initialized in the copy
                   constructor of a derived class.
    
           **-Wchar-subscripts**
               Warn if an array subscript has type "char".  This is a common
               cause of error, as programmers often forget that this type is
               signed on some machines.  This warning is enabled by **-Wall**.
    
           **-Wno-coverage-mismatch**
               Warn if feedback profiles do not match when using the
               **-fprofile-use** option.  If a source file is changed between
               compiling with **-fprofile-generate** and with **-fprofile-use** , the
               files with the profile feedback can fail to match the source
               file and GCC cannot use the profile feedback information.  By
               default, this warning is enabled and is treated as an error.
               **-Wno-coverage-mismatch** can be used to disable the warning or
               **-Wno-error=coverage-mismatch** can be used to disable the error.
               Disabling the error for this warning can result in poorly
               optimized code and is useful only in the case of very minor
               changes such as bug fixes to an existing code-base.
               Completely disabling the warning is not recommended.
    
           **-Wno-cpp**
               (C, Objective-C, C++, Objective-C++ and Fortran only)
    
               Suppress warning messages emitted by "#warning" directives.
    
           **-Wdouble-promotion**(C, C++, Objective-C and Objective-C++ only)
               Give a warning when a value of type "float" is implicitly
               promoted to "double".  CPUs with a 32-bit "single-precision"
               floating-point unit implement "float" in hardware, but emulate
               "double" in software.  On such a machine, doing computations
               using "double" values is much more expensive because of the
               overhead required for software emulation.
    
               It is easy to accidentally do computations with "double"
               because floating-point literals are implicitly of type
               "double".  For example, in:
    
                       float area(float radius)
                       {
                          return 3.14159 * radius * radius;
                       }
    
               the compiler performs the entire computation with "double"
               because the floating-point literal is a "double".
    
           **-Wduplicate-decl-specifier**(C and Objective-C only)
               Warn if a declaration has duplicate "const", "volatile",
               "restrict" or "_Atomic" specifier.  This warning is enabled by
               **-Wall**.
    
           **-Wformat**
           **-Wformat=**_n_
               Check calls to "printf" and "scanf", etc., to make sure that
               the arguments supplied have types appropriate to the format
               string specified, and that the conversions specified in the
               format string make sense.  This includes standard functions,
               and others specified by format attributes, in the "printf",
               "scanf", "strftime" and "strfmon" (an X/Open extension, not in
               the C standard) families (or other target-specific families).
               Which functions are checked without format attributes having
               been specified depends on the standard version selected, and
               such checks of functions without the attribute specified are
               disabled by **-ffreestanding** or **-fno-builtin**.
    
               The formats are checked against the format features supported
               by GNU libc version 2.2.  These include all ISO C90 and C99
               features, as well as features from the Single Unix
               Specification and some BSD and GNU extensions.  Other library
               implementations may not support all these features; GCC does
               not support warning about features that go beyond a particular
               library's limitations.  However, if **-Wpedantic** is used with
               **-Wformat** , warnings are given about format features not in the
               selected standard version (but not for "strfmon" formats,
               since those are not in any version of the C standard).
    
               **-Wformat=1**
               **-Wformat**
                   Option **-Wformat** is equivalent to **-Wformat=1** , and
                   **-Wno-format** is equivalent to **-Wformat=0**.  Since **-Wformat**
                   also checks for null format arguments for several
                   functions, **-Wformat** also implies **-Wnonnull**.  Some aspects
                   of this level of format checking can be disabled by the
                   options: **-Wno-format-contains-nul** , **-Wno-format-extra-args** ,
                   and **-Wno-format-zero-length**.  **-Wformat** is enabled by
                   **-Wall**.
    
               **-Wno-format-contains-nul**
                   If **-Wformat** is specified, do not warn about format strings
                   that contain NUL bytes.
    
               **-Wno-format-extra-args**
                   If **-Wformat** is specified, do not warn about excess
                   arguments to a "printf" or "scanf" format function.  The C
                   standard specifies that such arguments are ignored.
    
                   Where the unused arguments lie between used arguments that
                   are specified with **$** operand number specifications,
                   normally warnings are still given, since the
                   implementation could not know what type to pass to
                   "va_arg" to skip the unused arguments.  However, in the
                   case of "scanf" formats, this option suppresses the
                   warning if the unused arguments are all pointers, since
                   the Single Unix Specification says that such unused
                   arguments are allowed.
    
               **-Wformat-overflow**
               **-Wformat-overflow=**_level_
                   Warn about calls to formatted input/output functions such
                   as "sprintf" and "vsprintf" that might overflow the
                   destination buffer.  When the exact number of bytes
                   written by a format directive cannot be determined at
                   compile-time it is estimated based on heuristics that
                   depend on the _level_ argument and on optimization.  While
                   enabling optimization will in most cases improve the
                   accuracy of the warning, it may also result in false
                   positives.
    
                   **-Wformat-overflow**
                   **-Wformat-overflow=1**
                       Level _1_ of **-Wformat-overflow** enabled by **-Wformat**
                       employs a conservative approach that warns only about
                       calls that most likely overflow the buffer.  At this
                       level, numeric arguments to format directives with
                       unknown values are assumed to have the value of one,
                       and strings of unknown length to be empty.  Numeric
                       arguments that are known to be bounded to a subrange
                       of their type, or string arguments whose output is
                       bounded either by their directive's precision or by a
                       finite set of string literals, are assumed to take on
                       the value within the range that results in the most
                       bytes on output.  For example, the call to "sprintf"
                       below is diagnosed because even with both _a_ and _b_
                       equal to zero, the terminating NUL character ('\0')
                       appended by the function to the destination buffer
                       will be written past its end.  Increasing the size of
                       the buffer by a single byte is sufficient to avoid the
                       warning, though it may not be sufficient to avoid the
                       overflow.
    
                               void f (int a, int b)
                               {
                                 char buf [13];
                                 sprintf (buf, "a = %i, b = %i\n", a, b);
                               }
    
                   **-Wformat-overflow=2**
                       Level _2_ warns also about calls that might overflow the
                       destination buffer given an argument of sufficient
                       length or magnitude.  At level _2_ , unknown numeric
                       arguments are assumed to have the minimum
                       representable value for signed types with a precision
                       greater than 1, and the maximum representable value
                       otherwise.  Unknown string arguments whose length
                       cannot be assumed to be bounded either by the
                       directive's precision, or by a finite set of string
                       literals they may evaluate to, or the character array
                       they may point to, are assumed to be 1 character long.
    
                       At level _2_ , the call in the example above is again
                       diagnosed, but this time because with _a_ equal to a
                       32-bit "INT_MIN" the first %i directive will write
                       some of its digits beyond the end of the destination
                       buffer.  To make the call safe regardless of the
                       values of the two variables, the size of the
                       destination buffer must be increased to at least 34
                       bytes.  GCC includes the minimum size of the buffer in
                       an informational note following the warning.
    
                       An alternative to increasing the size of the
                       destination buffer is to constrain the range of
                       formatted values.  The maximum length of string
                       arguments can be bounded by specifying the precision
                       in the format directive.  When numeric arguments of
                       format directives can be assumed to be bounded by less
                       than the precision of their type, choosing an
                       appropriate length modifier to the format specifier
                       will reduce the required buffer size.  For example, if
                       _a_ and _b_ in the example above can be assumed to be
                       within the precision of the "short int" type then
                       using either the %hi format directive or casting the
                       argument to "short" reduces the maximum required size
                       of the buffer to 24 bytes.
    
                               void f (int a, int b)
                               {
                                 char buf [23];
                                 sprintf (buf, "a = %hi, b = %i\n", a, (short)b);
                               }
    
               **-Wno-format-zero-length**
                   If **-Wformat** is specified, do not warn about zero-length
                   formats.  The C standard specifies that zero-length
                   formats are allowed.
    
               **-Wformat=2**
                   Enable **-Wformat** plus additional format checks.  Currently
                   equivalent to **-Wformat -Wformat-nonliteral**
                   **-Wformat-security -Wformat-y2k**.
    
               **-Wformat-nonliteral**
                   If **-Wformat** is specified, also warn if the format string
                   is not a string literal and so cannot be checked, unless
                   the format function takes its format arguments as a
                   "va_list".
    
               **-Wformat-security**
                   If **-Wformat** is specified, also warn about uses of format
                   functions that represent possible security problems.  At
                   present, this warns about calls to "printf" and "scanf"
                   functions where the format string is not a string literal
                   and there are no format arguments, as in "printf (foo);".
                   This may be a security hole if the format string came from
                   untrusted input and contains **%n**.  (This is currently a
                   subset of what **-Wformat-nonliteral** warns about, but in
                   future warnings may be added to **-Wformat-security** that are
                   not included in **-Wformat-nonliteral**.)
    
               **-Wformat-signedness**
                   If **-Wformat** is specified, also warn if the format string
                   requires an unsigned argument and the argument is signed
                   and vice versa.
    
               **-Wformat-truncation**
               **-Wformat-truncation=**_level_
                   Warn about calls to formatted input/output functions such
                   as "snprintf" and "vsnprintf" that might result in output
                   truncation.  When the exact number of bytes written by a
                   format directive cannot be determined at compile-time it
                   is estimated based on heuristics that depend on the _level_
                   argument and on optimization.  While enabling optimization
                   will in most cases improve the accuracy of the warning, it
                   may also result in false positives.  Except as noted
                   otherwise, the option uses the same logic
                   **-Wformat-overflow**.
    
                   **-Wformat-truncation**
                   **-Wformat-truncation=1**
                       Level _1_ of **-Wformat-truncation** enabled by **-Wformat**
                       employs a conservative approach that warns only about
                       calls to bounded functions whose return value is
                       unused and that will most likely result in output
                       truncation.
    
                   **-Wformat-truncation=2**
                       Level _2_ warns also about calls to bounded functions
                       whose return value is used and that might result in
                       truncation given an argument of sufficient length or
                       magnitude.
    
               **-Wformat-y2k**
                   If **-Wformat** is specified, also warn about "strftime"
                   formats that may yield only a two-digit year.
    
           **-Wnonnull**
               Warn about passing a null pointer for arguments marked as
               requiring a non-null value by the "nonnull" function
               attribute.
    
               **-Wnonnull** is included in **-Wall** and **-Wformat**.  It can be
               disabled with the **-Wno-nonnull** option.
    
           **-Wnonnull-compare**
               Warn when comparing an argument marked with the "nonnull"
               function attribute against null inside the function.
    
               **-Wnonnull-compare** is included in **-Wall**.  It can be disabled
               with the **-Wno-nonnull-compare** option.
    
           **-Wnull-dereference**
               Warn if the compiler detects paths that trigger erroneous or
               undefined behavior due to dereferencing a null pointer.  This
               option is only active when **-fdelete-null-pointer-checks** is
               active, which is enabled by optimizations in most targets.
               The precision of the warnings depends on the optimization
               options used.
    
           **-Winit-self**(C, C++, Objective-C and Objective-C++ only)
               Warn about uninitialized variables that are initialized with
               themselves.  Note this option can only be used with the
               **-Wuninitialized** option.
    
               For example, GCC warns about "i" being uninitialized in the
               following snippet only when **-Winit-self** has been specified:
    
                       int f()
                       {
                         int i = i;
                         return i;
                       }
    
               This warning is enabled by **-Wall** in C++.
    
           **-Wimplicit-int**(C and Objective-C only)
               Warn when a declaration does not specify a type.  This warning
               is enabled by **-Wall**.
    
           **-Wimplicit-function-declaration**(C and Objective-C only)
               Give a warning whenever a function is used before being
               declared. In C99 mode (**-std=c99** or **-std=gnu99**), this warning
               is enabled by default and it is made into an error by
               **-pedantic-errors**. This warning is also enabled by **-Wall**.
    
           **-Wimplicit**(C and Objective-C only)
               Same as **-Wimplicit-int** and **-Wimplicit-function-declaration**.
               This warning is enabled by **-Wall**.
    
           **-Wimplicit-fallthrough**
               **-Wimplicit-fallthrough** is the same as **-Wimplicit-fallthrough=3**
               and **-Wno-implicit-fallthrough** is the same as
               **-Wimplicit-fallthrough=0**.
    
           **-Wimplicit-fallthrough=**_n_
               Warn when a switch case falls through.  For example:
    
                       switch (cond)
                         {
                         case 1:
                           a = 1;
                           break;
                         case 2:
                           a = 2;
                         case 3:
                           a = 3;
                           break;
                         }
    
               This warning does not warn when the last statement of a case
               cannot fall through, e.g. when there is a return statement or
               a call to function declared with the noreturn attribute.
               **-Wimplicit-fallthrough=** also takes into account control flow
               statements, such as ifs, and only warns when appropriate.
               E.g.
    
                       switch (cond)
                         {
                         case 1:
                           if (i > 3) {
                             bar (5);
                             break;
                           } else if (i < 1) {
                             bar (0);
                           } else
                             return;
                         default:
                           ...
                         }
    
               Since there are occasions where a switch case fall through is
               desirable, GCC provides an attribute, "__attribute__
               ((fallthrough))", that is to be used along with a null
               statement to suppress this warning that would normally occur:
    
                       switch (cond)
                         {
                         case 1:
                           bar (0);
                           __attribute__ ((fallthrough));
                         default:
                           ...
                         }
    
               C++17 provides a standard way to suppress the
               **-Wimplicit-fallthrough** warning using "[[fallthrough]];"
               instead of the GNU attribute.  In C++11 or C++14 users can use
               "[[gnu::fallthrough]];", which is a GNU extension.  Instead of
               these attributes, it is also possible to add a fallthrough
               comment to silence the warning.  The whole body of the C or
               C++ style comment should match the given regular expressions
               listed below.  The option argument _n_ specifies what kind of
               comments are accepted:
    
               *<**-Wimplicit-fallthrough=0** disables the warning altogether.>
               *<**-Wimplicit-fallthrough=1** matches ".*" regular>
                   expression, any comment is used as fallthrough comment.
    
               *<**-Wimplicit-fallthrough=2** case insensitively matches>
                   ".*falls?[ \t-]*thr(ough|u).*" regular expression.
    
               *<**-Wimplicit-fallthrough=3** case sensitively matches one of
               the>
                   following regular expressions:
    
                   *<"-fallthrough">
                   *<"@fallthrough@">
                   *<"lint -fallthrough[ \t]*">
                   *<"[ \t.!]*(ELSE,? |INTENTIONAL(LY)? )?FALL(S |
                   |-)?THR(OUGH|U)[ \t.!]*(-[^\n\r]*)?">
                   *<"[ \t.!]*(Else,? |Intentional(ly)? )?Fall((s |
                   |-)[Tt]|t)hr(ough|u)[ \t.!]*(-[^\n\r]*)?">
                   *<"[ \t.!]*([Ee]lse,? |[Ii]ntentional(ly)? )?fall(s |
                   |-)?thr(ough|u)[ \t.!]*(-[^\n\r]*)?">
               *<**-Wimplicit-fallthrough=4** case sensitively matches one of
               the>
                   following regular expressions:
    
                   *<"-fallthrough">
                   *<"@fallthrough@">
                   *<"lint -fallthrough[ \t]*">
                   *<"[ \t]*FALLTHR(OUGH|U)[ \t]*">
               *<**-Wimplicit-fallthrough=5** doesn't recognize any comments as>
                   fallthrough comments, only attributes disable the warning.
    
               The comment needs to be followed after optional whitespace and
               other comments by "case" or "default" keywords or by a user
               label that precedes some "case" or "default" label.
    
                       switch (cond)
                         {
                         case 1:
                           bar (0);
                           /* FALLTHRU */
                         default:
                           ...
                         }
    
               The **-Wimplicit-fallthrough=3** warning is enabled by **-Wextra**.
    
           **-Wif-not-aligned**(C, C++, Objective-C and Objective-C++ only)
               Control if warning triggered by the "warn_if_not_aligned"
               attribute should be issued.  This is enabled by default.  Use
               **-Wno-if-not-aligned** to disable it.
    
           **-Wignored-qualifiers**(C and C++ only)
               Warn if the return type of a function has a type qualifier
               such as "const".  For ISO C such a type qualifier has no
               effect, since the value returned by a function is not an
               lvalue.  For C++, the warning is only emitted for scalar types
               or "void".  ISO C prohibits qualified "void" return types on
               function definitions, so such return types always receive a
               warning even without this option.
    
               This warning is also enabled by **-Wextra**.
    
           **-Wignored-attributes**(C and C++ only)
               Warn when an attribute is ignored.  This is different from the
               **-Wattributes** option in that it warns whenever the compiler
               decides to drop an attribute, not that the attribute is either
               unknown, used in a wrong place, etc.  This warning is enabled
               by default.
    
           **-Wmain**
               Warn if the type of "main" is suspicious.  "main" should be a
               function with external linkage, returning int, taking either
               zero arguments, two, or three arguments of appropriate types.
               This warning is enabled by default in C++ and is enabled by
               either **-Wall** or **-Wpedantic**.
    
           **-Wmisleading-indentation**(C and C++ only)
               Warn when the indentation of the code does not reflect the
               block structure.  Specifically, a warning is issued for "if",
               "else", "while", and "for" clauses with a guarded statement
               that does not use braces, followed by an unguarded statement
               with the same indentation.
    
               In the following example, the call to "bar" is misleadingly
               indented as if it were guarded by the "if" conditional.
    
                         if (some_condition ())
                           foo ();
                           bar ();  /* Gotcha: this is not guarded by the "if".  */
    
               In the case of mixed tabs and spaces, the warning uses the
               **-ftabstop=** option to determine if the statements line up
               (defaulting to 8).
    
               The warning is not issued for code involving multiline
               preprocessor logic such as the following example.
    
                         if (flagA)
                           foo (0);
                       #if SOME_CONDITION_THAT_DOES_NOT_HOLD
                         if (flagB)
                       #endif
                           foo (1);
    
               The warning is not issued after a "#line" directive, since
               this typically indicates autogenerated code, and no
               assumptions can be made about the layout of the file that the
               directive references.
    
               This warning is enabled by **-Wall** in C and C++.
    
           **-Wmissing-attributes**
               Warn when a declaration of a function is missing one or more
               attributes that a related function is declared with and whose
               absence may adversely affect the correctness or efficiency of
               generated code.  For example, the warning is issued for
               declarations of aliases that use attributes to specify less
               restrictive requirements than those of their targets.  This
               typically represents a potential optimization opportunity.  By
               contrast, the **-Wattribute-alias=2** option controls warnings
               issued when the alias is more restrictive than the target,
               which could lead to incorrect code generation.  Attributes
               considered include "alloc_align", "alloc_size", "cold",
               "const", "hot", "leaf", "malloc", "nonnull", "noreturn",
               "nothrow", "pure", "returns_nonnull", and "returns_twice".
    
               In C++, the warning is issued when an explicit specialization
               of a primary template declared with attribute "alloc_align",
               "alloc_size", "assume_aligned", "format", "format_arg",
               "malloc", or "nonnull" is declared without it.  Attributes
               "deprecated", "error", and "warning" suppress the warning..
    
               You can use the "copy" attribute to apply the same set of
               attributes to a declaration as that on another declaration
               without explicitly enumerating the attributes. This attribute
               can be applied to declarations of functions, variables, or
               types.
    
               **-Wmissing-attributes** is enabled by **-Wall**.
    
               For example, since the declaration of the primary function
               template below makes use of both attribute "malloc" and
               "alloc_size" the declaration of the explicit specialization of
               the template is diagnosed because it is missing one of the
               attributes.
    
                       template <class T>
                       T* __attribute__ ((malloc, alloc_size (1)))
                       allocate (size_t);
    
                       template <>
                       void* __attribute__ ((malloc))   // missing alloc_size
                       allocate<void> (size_t);
    
           **-Wmissing-braces**
               Warn if an aggregate or union initializer is not fully
               bracketed.  In the following example, the initializer for "a"
               is not fully bracketed, but that for "b" is fully bracketed.
               This warning is enabled by **-Wall** in C.
    
                       int a[2][2] = { 0, 1, 2, 3 };
                       int b[2][2] = { { 0, 1 }, { 2, 3 } };
    
               This warning is enabled by **-Wall**.
    
           **-Wmissing-include-dirs**(C, C++, Objective-C and Objective-C++
           only)
               Warn if a user-supplied include directory does not exist.
    
           **-Wmissing-profile**
               Warn if feedback profiles are missing when using the
               **-fprofile-use** option.  This option diagnoses those cases where
               a new function or a new file is added to the user code between
               compiling with **-fprofile-generate** and with **-fprofile-use** ,
               without regenerating the profiles.  In these cases, the
               profile feedback data files do not contain any profile
               feedback information for the newly added function or file
               respectively.  Also, in the case when profile count data
               (.gcda) files are removed, GCC cannot use any profile feedback
               information.  In all these cases, warnings are issued to
               inform the user that a profile generation step is due.
               **-Wno-missing-profile** can be used to disable the warning.
               Ignoring the warning can result in poorly optimized code.
               Completely disabling the warning is not recommended and should
               be done only when non-existent profile data is justified.
    
           **-Wmultistatement-macros**
               Warn about unsafe multiple statement macros that appear to be
               guarded by a clause such as "if", "else", "for", "switch", or
               "while", in which only the first statement is actually guarded
               after the macro is expanded.
    
               For example:
    
                       #define DOIT x++; y++
                       if (c)
                         DOIT;
    
               will increment "y" unconditionally, not just when "c" holds.
               The can usually be fixed by wrapping the macro in a do-while
               loop:
    
                       #define DOIT do { x++; y++; } while (0)
                       if (c)
                         DOIT;
    
               This warning is enabled by **-Wall** in C and C++.
    
           **-Wparentheses**
               Warn if parentheses are omitted in certain contexts, such as
               when there is an assignment in a context where a truth value
               is expected, or when operators are nested whose precedence
               people often get confused about.
    
               Also warn if a comparison like "x<=y<=z" appears; this is
               equivalent to "(x<=y ? 1 : 0) <= z", which is a different
               interpretation from that of ordinary mathematical notation.
    
               Also warn for dangerous uses of the GNU extension to "?:" with
               omitted middle operand. When the condition in the "?":
               operator is a boolean expression, the omitted value is always
               1.  Often programmers expect it to be a value computed inside
               the conditional expression instead.
    
               For C++ this also warns for some cases of unnecessary
               parentheses in declarations, which can indicate an attempt at
               a function call instead of a declaration:
    
                       {
                         // Declares a local variable called mymutex.
                         std::unique_lock<std::mutex> (mymutex);
                         // User meant std::unique_lock<std::mutex> lock (mymutex);
                       }
    
               This warning is enabled by **-Wall**.
    
           **-Wsequence-point**
               Warn about code that may have undefined semantics because of
               violations of sequence point rules in the C and C++ standards.
    
               The C and C++ standards define the order in which expressions
               in a C/C++ program are evaluated in terms of _sequence points_ ,
               which represent a partial ordering between the execution of
               parts of the program: those executed before the sequence
               point, and those executed after it.  These occur after the
               evaluation of a full expression (one which is not part of a
               larger expression), after the evaluation of the first operand
               of a "&&", "||", "? :" or "," (comma) operator, before a
               function is called (but after the evaluation of its arguments
               and the expression denoting the called function), and in
               certain other places.  Other than as expressed by the sequence
               point rules, the order of evaluation of subexpressions of an
               expression is not specified.  All these rules describe only a
               partial order rather than a total order, since, for example,
               if two functions are called within one expression with no
               sequence point between them, the order in which the functions
               are called is not specified.  However, the standards committee
               have ruled that function calls do not overlap.
    
               It is not specified when between sequence points modifications
               to the values of objects take effect.  Programs whose behavior
               depends on this have undefined behavior; the C and C++
               standards specify that "Between the previous and next sequence
               point an object shall have its stored value modified at most
               once by the evaluation of an expression.  Furthermore, the
               prior value shall be read only to determine the value to be
               stored.".  If a program breaks these rules, the results on any
               particular implementation are entirely unpredictable.
    
               Examples of code with undefined behavior are "a = a++;", "a[n]
               = b[n++]" and "a[i++] = i;".  Some more complicated cases are
               not diagnosed by this option, and it may give an occasional
               false positive result, but in general it has been found fairly
               effective at detecting this sort of problem in programs.
    
               The C++17 standard will define the order of evaluation of
               operands in more cases: in particular it requires that the
               right-hand side of an assignment be evaluated before the left-
               hand side, so the above examples are no longer undefined.  But
               this warning will still warn about them, to help people avoid
               writing code that is undefined in C and earlier revisions of
               C++.
    
               The standard is worded confusingly, therefore there is some
               debate over the precise meaning of the sequence point rules in
               subtle cases.  Links to discussions of the problem, including
               proposed formal definitions, may be found on the GCC readings
               page, at <**http://gcc.gnu.org/readings.html **>.
    
               This warning is enabled by **-Wall** for C and C++.
    
           **-Wno-return-local-addr**
               Do not warn about returning a pointer (or in C++, a reference)
               to a variable that goes out of scope after the function
               returns.
    
           **-Wreturn-type**
               Warn whenever a function is defined with a return type that
               defaults to "int".  Also warn about any "return" statement
               with no return value in a function whose return type is not
               "void" (falling off the end of the function body is considered
               returning without a value).
    
               For C only, warn about a "return" statement with an expression
               in a function whose return type is "void", unless the
               expression type is also "void".  As a GNU extension, the
               latter case is accepted without a warning unless **-Wpedantic** is
               used.  Attempting to use the return value of a non-"void"
               function other than "main" that flows off the end by reaching
               the closing curly brace that terminates the function is
               undefined.
    
               Unlike in C, in C++, flowing off the end of a non-"void"
               function other than "main" results in undefined behavior even
               when the value of the function is not used.
    
               This warning is enabled by default in C++ and by **-Wall**
               otherwise.
    
           **-Wshift-count-negative**
               Warn if shift count is negative. This warning is enabled by
               default.
    
           **-Wshift-count-overflow**
               Warn if shift count >= width of type. This warning is enabled
               by default.
    
           **-Wshift-negative-value**
               Warn if left shifting a negative value.  This warning is
               enabled by **-Wextra** in C99 (and newer) and C++11 to C++17
               modes.
    
           **-Wshift-overflow**
           **-Wshift-overflow=**_n_
               Warn about left shift overflows.  This warning is enabled by
               default in C99 and C++11 modes (and newer).
    
               **-Wshift-overflow=1**
                   This is the warning level of **-Wshift-overflow** and is
                   enabled by default in C99 and C++11 modes (and newer).
                   This warning level does not warn about left-shifting 1
                   into the sign bit.  (However, in C, such an overflow is
                   still rejected in contexts where an integer constant
                   expression is required.)  No warning is emitted in C++2A
                   mode (and newer), as signed left shifts always wrap.
    
               **-Wshift-overflow=2**
                   This warning level also warns about left-shifting 1 into
                   the sign bit, unless C++14 mode (or newer) is active.
    
           **-Wswitch**
               Warn whenever a "switch" statement has an index of enumerated
               type and lacks a "case" for one or more of the named codes of
               that enumeration.  (The presence of a "default" label prevents
               this warning.)  "case" labels outside the enumeration range
               also provoke warnings when this option is used (even if there
               is a "default" label).  This warning is enabled by **-Wall**.
    
           **-Wswitch-default**
               Warn whenever a "switch" statement does not have a "default"
               case.
    
           **-Wswitch-enum**
               Warn whenever a "switch" statement has an index of enumerated
               type and lacks a "case" for one or more of the named codes of
               that enumeration.  "case" labels outside the enumeration range
               also provoke warnings when this option is used.  The only
               difference between **-Wswitch** and this option is that this
               option gives a warning about an omitted enumeration code even
               if there is a "default" label.
    
           **-Wswitch-bool**
               Warn whenever a "switch" statement has an index of boolean
               type and the case values are outside the range of a boolean
               type.  It is possible to suppress this warning by casting the
               controlling expression to a type other than "bool".  For
               example:
    
                       switch ((int) (a == 4))
                         {
                         ...
                         }
    
               This warning is enabled by default for C and C++ programs.
    
           **-Wswitch-unreachable**
               Warn whenever a "switch" statement contains statements between
               the controlling expression and the first case label, which
               will never be executed.  For example:
    
                       switch (cond)
                         {
                          i = 15;
                         ...
                          case 5:
                         ...
                         }
    
               **-Wswitch-unreachable** does not warn if the statement between
               the controlling expression and the first case label is just a
               declaration:
    
                       switch (cond)
                         {
                          int i;
                         ...
                          case 5:
                          i = 5;
                         ...
                         }
    
               This warning is enabled by default for C and C++ programs.
    
           **-Wsync-nand**(C and C++ only)
               Warn when "__sync_fetch_and_nand" and "__sync_nand_and_fetch"
               built-in functions are used.  These functions changed
               semantics in GCC 4.4.
    
           **-Wunused-but-set-parameter**
               Warn whenever a function parameter is assigned to, but
               otherwise unused (aside from its declaration).
    
               To suppress this warning use the "unused" attribute.
    
               This warning is also enabled by **-Wunused** together with
               **-Wextra**.
    
           **-Wunused-but-set-variable**
               Warn whenever a local variable is assigned to, but otherwise
               unused (aside from its declaration).  This warning is enabled
               by **-Wall**.
    
               To suppress this warning use the "unused" attribute.
    
               This warning is also enabled by **-Wunused** , which is enabled by
               **-Wall**.
    
           **-Wunused-function**
               Warn whenever a static function is declared but not defined or
               a non-inline static function is unused.  This warning is
               enabled by **-Wall**.
    
           **-Wunused-label**
               Warn whenever a label is declared but not used.  This warning
               is enabled by **-Wall**.
    
               To suppress this warning use the "unused" attribute.
    
           **-Wunused-local-typedefs**(C, Objective-C, C++ and Objective-C++
           only)
               Warn when a typedef locally defined in a function is not used.
               This warning is enabled by **-Wall**.
    
           **-Wunused-parameter**
               Warn whenever a function parameter is unused aside from its
               declaration.
    
               To suppress this warning use the "unused" attribute.
    
           **-Wno-unused-result**
               Do not warn if a caller of a function marked with attribute
               "warn_unused_result" does not use its return value. The
               default is **-Wunused-result**.
    
           **-Wunused-variable**
               Warn whenever a local or static variable is unused aside from
               its declaration. This option implies **-Wunused-const-variable=1**
               for C, but not for C++. This warning is enabled by **-Wall**.
    
               To suppress this warning use the "unused" attribute.
    
           **-Wunused-const-variable**
           **-Wunused-const-variable=**_n_
               Warn whenever a constant static variable is unused aside from
               its declaration.  **-Wunused-const-variable=1** is enabled by
               **-Wunused-variable** for C, but not for C++. In C this declares
               variable storage, but in C++ this is not an error since const
               variables take the place of "#define"s.
    
               To suppress this warning use the "unused" attribute.
    
               **-Wunused-const-variable=1**
                   This is the warning level that is enabled by
                   **-Wunused-variable** for C.  It warns only about unused
                   static const variables defined in the main compilation
                   unit, but not about static const variables declared in any
                   header included.
    
               **-Wunused-const-variable=2**
                   This warning level also warns for unused constant static
                   variables in headers (excluding system headers).  This is
                   the warning level of **-Wunused-const-variable** and must be
                   explicitly requested since in C++ this isn't an error and
                   in C it might be harder to clean up all headers included.
    
           **-Wunused-value**
               Warn whenever a statement computes a result that is explicitly
               not used. To suppress this warning cast the unused expression
               to "void". This includes an expression-statement or the left-
               hand side of a comma expression that contains no side effects.
               For example, an expression such as "x[i,j]" causes a warning,
               while "x[(void)i,j]" does not.
    
               This warning is enabled by **-Wall**.
    
           **-Wunused**
               All the above **-Wunused** options combined.
    
               In order to get a warning about an unused function parameter,
               you must either specify **-Wextra -Wunused**(note that **-Wall**
               implies **-Wunused**), or separately specify **-Wunused-parameter**.
    
           **-Wuninitialized**
               Warn if an automatic variable is used without first being
               initialized or if a variable may be clobbered by a "setjmp"
               call. In C++, warn if a non-static reference or non-static
               "const" member appears in a class without constructors.
    
               If you want to warn about code that uses the uninitialized
               value of the variable in its own initializer, use the
               **-Winit-self** option.
    
               These warnings occur for individual uninitialized or clobbered
               elements of structure, union or array variables as well as for
               variables that are uninitialized or clobbered as a whole.
               They do not occur for variables or elements declared
               "volatile".  Because these warnings depend on optimization,
               the exact variables or elements for which there are warnings
               depends on the precise optimization options and version of GCC
               used.
    
               Note that there may be no warning about a variable that is
               used only to compute a value that itself is never used,
               because such computations may be deleted by data flow analysis
               before the warnings are printed.
    
           **-Winvalid-memory-model**
               Warn for invocations of **__atomic Builtins** , **__sync Builtins** ,
               and the C11 atomic generic functions with a memory consistency
               argument that is either invalid for the operation or outside
               the range of values of the "memory_order" enumeration.  For
               example, since the "__atomic_store" and "__atomic_store_n"
               built-ins are only defined for the relaxed, release, and
               sequentially consistent memory orders the following code is
               diagnosed:
    
                       void store (int *i)
                       {
                         __atomic_store_n (i, 0, memory_order_consume);
                       }
    
               **-Winvalid-memory-model** is enabled by default.
    
           **-Wmaybe-uninitialized**
               For an automatic (i.e. local) variable, if there exists a path
               from the function entry to a use of the variable that is
               initialized, but there exist some other paths for which the
               variable is not initialized, the compiler emits a warning if
               it cannot prove the uninitialized paths are not executed at
               run time.
    
               These warnings are only possible in optimizing compilation,
               because otherwise GCC does not keep track of the state of
               variables.
    
               These warnings are made optional because GCC may not be able
               to determine when the code is correct in spite of appearing to
               have an error.  Here is one example of how this can happen:
    
                       {
                         int x;
                         switch (y)
                           {
                           case 1: x = 1;
                             break;
                           case 2: x = 4;
                             break;
                           case 3: x = 5;
                           }
                         foo (x);
                       }
    
               If the value of "y" is always 1, 2 or 3, then "x" is always
               initialized, but GCC doesn't know this. To suppress the
               warning, you need to provide a default case with _assert_(0) or
               similar code.
    
               This option also warns when a non-volatile automatic variable
               might be changed by a call to "longjmp".  The compiler sees
               only the calls to "setjmp".  It cannot know where "longjmp"
               will be called; in fact, a signal handler could call it at any
               point in the code.  As a result, you may get a warning even
               when there is in fact no problem because "longjmp" cannot in
               fact be called at the place that would cause a problem.
    
               Some spurious warnings can be avoided if you declare all the
               functions you use that never return as "noreturn".
    
               This warning is enabled by **-Wall** or **-Wextra**.
    
           **-Wunknown-pragmas**
               Warn when a "#pragma" directive is encountered that is not
               understood by GCC.  If this command-line option is used,
               warnings are even issued for unknown pragmas in system header
               files.  This is not the case if the warnings are only enabled
               by the **-Wall** command-line option.
    
           **-Wno-pragmas**
               Do not warn about misuses of pragmas, such as incorrect
               parameters, invalid syntax, or conflicts between pragmas.  See
               also **-Wunknown-pragmas**.
    
           **-Wno-prio-ctor-dtor**
               Do not warn if a priority from 0 to 100 is used for
               constructor or destructor.  The use of constructor and
               destructor attributes allow you to assign a priority to the
               constructor/destructor to control its order of execution
               before "main" is called or after it returns.  The priority
               values must be greater than 100 as the compiler reserves
               priority values between 0--100 for the implementation.
    
           **-Wstrict-aliasing**
               This option is only active when **-fstrict-aliasing** is active.
               It warns about code that might break the strict aliasing rules
               that the compiler is using for optimization.  The warning does
               not catch all cases, but does attempt to catch the more common
               pitfalls.  It is included in **-Wall**.  It is equivalent to
               **-Wstrict-aliasing=3**
    
           **-Wstrict-aliasing=n**
               This option is only active when **-fstrict-aliasing** is active.
               It warns about code that might break the strict aliasing rules
               that the compiler is using for optimization.  Higher levels
               correspond to higher accuracy (fewer false positives).  Higher
               levels also correspond to more effort, similar to the way **-O**
               works.  **-Wstrict-aliasing** is equivalent to
               **-Wstrict-aliasing=3**.
    
               Level 1: Most aggressive, quick, least accurate.  Possibly
               useful when higher levels do not warn but **-fstrict-aliasing**
               still breaks the code, as it has very few false negatives.
               However, it has many false positives.  Warns for all pointer
               conversions between possibly incompatible types, even if never
               dereferenced.  Runs in the front end only.
    
               Level 2: Aggressive, quick, not too precise.  May still have
               many false positives (not as many as level 1 though), and few
               false negatives (but possibly more than level 1).  Unlike
               level 1, it only warns when an address is taken.  Warns about
               incomplete types.  Runs in the front end only.
    
               Level 3 (default for **-Wstrict-aliasing**): Should have very few
               false positives and few false negatives.  Slightly slower than
               levels 1 or 2 when optimization is enabled.  Takes care of the
               common pun+dereference pattern in the front end:
               "*(int*)&some_float".  If optimization is enabled, it also
               runs in the back end, where it deals with multiple statement
               cases using flow-sensitive points-to information.  Only warns
               when the converted pointer is dereferenced.  Does not warn
               about incomplete types.
    
           **-Wstrict-overflow**
           **-Wstrict-overflow=**_n_
               This option is only active when signed overflow is undefined.
               It warns about cases where the compiler optimizes based on the
               assumption that signed overflow does not occur.  Note that it
               does not warn about all cases where the code might overflow:
               it only warns about cases where the compiler implements some
               optimization.  Thus this warning depends on the optimization
               level.
    
               An optimization that assumes that signed overflow does not
               occur is perfectly safe if the values of the variables
               involved are such that overflow never does, in fact, occur.
               Therefore this warning can easily give a false positive: a
               warning about code that is not actually a problem.  To help
               focus on important issues, several warning levels are defined.
               No warnings are issued for the use of undefined signed
               overflow when estimating how many iterations a loop requires,
               in particular when determining whether a loop will be executed
               at all.
    
               **-Wstrict-overflow=1**
                   Warn about cases that are both questionable and easy to
                   avoid.  For example the compiler simplifies "x + 1 > x" to
                   1.  This level of **-Wstrict-overflow** is enabled by **-Wall** ;
                   higher levels are not, and must be explicitly requested.
    
               **-Wstrict-overflow=2**
                   Also warn about other cases where a comparison is
                   simplified to a constant.  For example: "abs (x) >= 0".
                   This can only be simplified when signed integer overflow
                   is undefined, because "abs (INT_MIN)" overflows to
                   "INT_MIN", which is less than zero.  **-Wstrict-overflow**
                   (with no level) is the same as **-Wstrict-overflow=2**.
    
               **-Wstrict-overflow=3**
                   Also warn about other cases where a comparison is
                   simplified.  For example: "x + 1 > 1" is simplified to "x
                   > 0".
    
               **-Wstrict-overflow=4**
                   Also warn about other simplifications not covered by the
                   above cases.  For example: "(x * 10) / 5" is simplified to
                   "x * 2".
    
               **-Wstrict-overflow=5**
                   Also warn about cases where the compiler reduces the
                   magnitude of a constant involved in a comparison.  For
                   example: "x + 2 > y" is simplified to "x + 1 >= y".  This
                   is reported only at the highest warning level because this
                   simplification applies to many comparisons, so this
                   warning level gives a very large number of false
                   positives.
    
           **-Wstringop-overflow**
           **-Wstringop-overflow=**_type_
               Warn for calls to string manipulation functions such as
               "memcpy" and "strcpy" that are determined to overflow the
               destination buffer.  The optional argument is one greater than
               the type of Object Size Checking to perform to determine the
               size of the destination.  The argument is meaningful only for
               functions that operate on character arrays but not for raw
               memory functions like "memcpy" which always make use of Object
               Size type-0.  The option also warns for calls that specify a
               size in excess of the largest possible object or at most
               "SIZE_MAX / 2" bytes.  The option produces the best results
               with optimization enabled but can detect a small subset of
               simple buffer overflows even without optimization in calls to
               the GCC built-in functions like "__builtin_memcpy" that
               correspond to the standard functions.  In any case, the option
               warns about just a subset of buffer overflows detected by the
               corresponding overflow checking built-ins.  For example, the
               option will issue a warning for the "strcpy" call below
               because it copies at least 5 characters (the string "blue"
               including the terminating NUL) into the buffer of size 4.
    
                       enum Color { blue, purple, yellow };
                       const char* f (enum Color clr)
                       {
                         static char buf [4];
                         const char *str;
                         switch (clr)
                           {
                             case blue: str = "blue"; break;
                             case purple: str = "purple"; break;
                             case yellow: str = "yellow"; break;
                           }
    
                         return strcpy (buf, str);   // warning here
                       }
    
               Option **-Wstringop-overflow=2** is enabled by default.
    
               **-Wstringop-overflow**
               **-Wstringop-overflow=1**
                   The **-Wstringop-overflow=1** option uses type-zero Object
                   Size Checking to determine the sizes of destination
                   objects.  This is the default setting of the option.  At
                   this setting the option will not warn for writes past the
                   end of subobjects of larger objects accessed by pointers
                   unless the size of the largest surrounding object is
                   known.  When the destination may be one of several objects
                   it is assumed to be the largest one of them.  On Linux
                   systems, when optimization is enabled at this setting the
                   option warns for the same code as when the
                   "_FORTIFY_SOURCE" macro is defined to a non-zero value.
    
               **-Wstringop-overflow=2**
                   The **-Wstringop-overflow=2** option uses type-one Object Size
                   Checking to determine the sizes of destination objects.
                   At this setting the option will warn about overflows when
                   writing to members of the largest complete objects whose
                   exact size is known.  It will, however, not warn for
                   excessive writes to the same members of unknown objects
                   referenced by pointers since they may point to arrays
                   containing unknown numbers of elements.
    
               **-Wstringop-overflow=3**
                   The **-Wstringop-overflow=3** option uses type-two Object Size
                   Checking to determine the sizes of destination objects.
                   At this setting the option warns about overflowing the
                   smallest object or data member.  This is the most
                   restrictive setting of the option that may result in
                   warnings for safe code.
    
               **-Wstringop-overflow=4**
                   The **-Wstringop-overflow=4** option uses type-three Object
                   Size Checking to determine the sizes of destination
                   objects.  At this setting the option will warn about
                   overflowing any data members, and when the destination is
                   one of several objects it uses the size of the largest of
                   them to decide whether to issue a warning.  Similarly to
                   **-Wstringop-overflow=3** this setting of the option may
                   result in warnings for benign code.
    
           **-Wstringop-truncation**
               Warn for calls to bounded string manipulation functions such
               as "strncat", "strncpy", and "stpncpy" that may either
               truncate the copied string or leave the destination unchanged.
    
               In the following example, the call to "strncat" specifies a
               bound that is less than the length of the source string.  As a
               result, the copy of the source will be truncated and so the
               call is diagnosed.  To avoid the warning use "bufsize - strlen
               (buf) - 1)" as the bound.
    
                       void append (char *buf, size_t bufsize)
                       {
                         strncat (buf, ".txt", 3);
                       }
    
               As another example, the following call to "strncpy" results in
               copying to "d" just the characters preceding the terminating
               NUL, without appending the NUL to the end.  Assuming the
               result of "strncpy" is necessarily a NUL-terminated string is
               a common mistake, and so the call is diagnosed.  To avoid the
               warning when the result is not expected to be NUL-terminated,
               call "memcpy" instead.
    
                       void copy (char *d, const char *s)
                       {
                         strncpy (d, s, strlen (s));
                       }
    
               In the following example, the call to "strncpy" specifies the
               size of the destination buffer as the bound.  If the length of
               the source string is equal to or greater than this size the
               result of the copy will not be NUL-terminated.  Therefore, the
               call is also diagnosed.  To avoid the warning, specify "sizeof
               buf - 1" as the bound and set the last element of the buffer
               to "NUL".
    
                       void copy (const char *s)
                       {
                         char buf[80];
                         strncpy (buf, s, sizeof buf);
                         ...
                       }
    
               In situations where a character array is intended to store a
               sequence of bytes with no terminating "NUL" such an array may
               be annotated with attribute "nonstring" to avoid this warning.
               Such arrays, however, are not suitable arguments to functions
               that expect "NUL"-terminated strings.  To help detect
               accidental misuses of such arrays GCC issues warnings unless
               it can prove that the use is safe.
    
           **-Wsuggest-attribute=**[**pure** |**const** |**noreturn** |**format** |**cold** |**malloc**]
               Warn for cases where adding an attribute may be beneficial.
               The attributes currently supported are listed below.
    
               **-Wsuggest-attribute=pure**
               **-Wsuggest-attribute=const**
               **-Wsuggest-attribute=noreturn**
               **-Wmissing-noreturn**
               **-Wsuggest-attribute=malloc**
                   Warn about functions that might be candidates for
                   attributes "pure", "const" or "noreturn" or "malloc". The
                   compiler only warns for functions visible in other
                   compilation units or (in the case of "pure" and "const")
                   if it cannot prove that the function returns normally. A
                   function returns normally if it doesn't contain an
                   infinite loop or return abnormally by throwing, calling
                   "abort" or trapping.  This analysis requires option
                   **-fipa-pure-const** , which is enabled by default at **-O** and
                   higher.  Higher optimization levels improve the accuracy
                   of the analysis.
    
               **-Wsuggest-attribute=format**
               **-Wmissing-format-attribute**
                   Warn about function pointers that might be candidates for
                   "format" attributes.  Note these are only possible
                   candidates, not absolute ones.  GCC guesses that function
                   pointers with "format" attributes that are used in
                   assignment, initialization, parameter passing or return
                   statements should have a corresponding "format" attribute
                   in the resulting type.  I.e. the left-hand side of the
                   assignment or initialization, the type of the parameter
                   variable, or the return type of the containing function
                   respectively should also have a "format" attribute to
                   avoid the warning.
    
                   GCC also warns about function definitions that might be
                   candidates for "format" attributes.  Again, these are only
                   possible candidates.  GCC guesses that "format" attributes
                   might be appropriate for any function that calls a
                   function like "vprintf" or "vscanf", but this might not
                   always be the case, and some functions for which "format"
                   attributes are appropriate may not be detected.
    
               **-Wsuggest-attribute=cold**
                   Warn about functions that might be candidates for "cold"
                   attribute.  This is based on static detection and
                   generally will only warn about functions which always
                   leads to a call to another "cold" function such as
                   wrappers of C++ "throw" or fatal error reporting functions
                   leading to "abort".
    
           **-Wsuggest-final-types**
               Warn about types with virtual methods where code quality would
               be improved if the type were declared with the C++11 "final"
               specifier, or, if possible, declared in an anonymous
               namespace. This allows GCC to more aggressively devirtualize
               the polymorphic calls. This warning is more effective with
               link time optimization, where the information about the class
               hierarchy graph is more complete.
    
           **-Wsuggest-final-methods**
               Warn about virtual methods where code quality would be
               improved if the method were declared with the C++11 "final"
               specifier, or, if possible, its type were declared in an
               anonymous namespace or with the "final" specifier.  This
               warning is more effective with link-time optimization, where
               the information about the class hierarchy graph is more
               complete. It is recommended to first consider suggestions of
               **-Wsuggest-final-types** and then rebuild with new annotations.
    
           **-Wsuggest-override**
               Warn about overriding virtual functions that are not marked
               with the override keyword.
    
           **-Walloc-zero**
               Warn about calls to allocation functions decorated with
               attribute "alloc_size" that specify zero bytes, including
               those to the built-in forms of the functions "aligned_alloc",
               "alloca", "calloc", "malloc", and "realloc".  Because the
               behavior of these functions when called with a zero size
               differs among implementations (and in the case of "realloc"
               has been deprecated) relying on it may result in subtle
               portability bugs and should be avoided.
    
           **-Walloc-size-larger-than=**_byte-size_
               Warn about calls to functions decorated with attribute
               "alloc_size" that attempt to allocate objects larger than the
               specified number of bytes, or where the result of the size
               computation in an integer type with infinite precision would
               exceed the value of **PTRDIFF_MAX** on the target.
               **-Walloc-size-larger-than=PTRDIFF_MAX** is enabled by default.
               Warnings controlled by the option can be disabled either by
               specifying _byte-size_ of **SIZE_MAX** or more or by
               **-Wno-alloc-size-larger-than**.
    
           **-Wno-alloc-size-larger-than**
               Disable **-Walloc-size-larger-than=** warnings.  The option is
               equivalent to **-Walloc-size-larger-than=SIZE_MAX** or larger.
    
           **-Walloca**
               This option warns on all uses of "alloca" in the source.
    
           **-Walloca-larger-than=**_byte-size_
               This option warns on calls to "alloca" with an integer
               argument whose value is either zero, or that is not bounded by
               a controlling predicate that limits its value to at most _byte-_
               _size_.  It also warns for calls to "alloca" where the bound
               value is unknown.  Arguments of non-integer types are
               considered unbounded even if they appear to be constrained to
               the expected range.
    
               For example, a bounded case of "alloca" could be:
    
                       void func (size_t n)
                       {
                         void *p;
                         if (n <= 1000)
                           p = alloca (n);
                         else
                           p = malloc (n);
                         f (p);
                       }
    
               In the above example, passing "-Walloca-larger-than=1000"
               would not issue a warning because the call to "alloca" is
               known to be at most 1000 bytes.  However, if
               "-Walloca-larger-than=500" were passed, the compiler would
               emit a warning.
    
               Unbounded uses, on the other hand, are uses of "alloca" with
               no controlling predicate constraining its integer argument.
               For example:
    
                       void func ()
                       {
                         void *p = alloca (n);
                         f (p);
                       }
    
               If "-Walloca-larger-than=500" were passed, the above would
               trigger a warning, but this time because of the lack of bounds
               checking.
    
               Note, that even seemingly correct code involving signed
               integers could cause a warning:
    
                       void func (signed int n)
                       {
                         if (n < 500)
                           {
                             p = alloca (n);
                             f (p);
                           }
                       }
    
               In the above example, _n_ could be negative, causing a larger
               than expected argument to be implicitly cast into the "alloca"
               call.
    
               This option also warns when "alloca" is used in a loop.
    
               **-Walloca-larger-than=PTRDIFF_MAX** is enabled by default but is
               usually only effective  when **-ftree-vrp** is active (default for
               **-O2** and above).
    
               See also **-Wvla-larger-than=byte-size**.
    
           **-Wno-alloca-larger-than**
               Disable **-Walloca-larger-than=** warnings.  The option is
               equivalent to **-Walloca-larger-than=SIZE_MAX** or larger.
    
           **-Warray-bounds**
           **-Warray-bounds=**_n_
               This option is only active when **-ftree-vrp** is active (default
               for **-O2** and above). It warns about subscripts to arrays that
               are always out of bounds. This warning is enabled by **-Wall**.
    
               **-Warray-bounds=1**
                   This is the warning level of **-Warray-bounds** and is enabled
                   by **-Wall** ; higher levels are not, and must be explicitly
                   requested.
    
               **-Warray-bounds=2**
                   This warning level also warns about out of bounds access
                   for arrays at the end of a struct and for arrays accessed
                   through pointers. This warning level may give a larger
                   number of false positives and is deactivated by default.
    
           **-Wattribute-alias=**_n_
           **-Wno-attribute-alias**
               Warn about declarations using the "alias" and similar
               attributes whose target is incompatible with the type of the
               alias.
    
               **-Wattribute-alias=1**
                   The default warning level of the **-Wattribute-alias** option
                   diagnoses incompatibilities between the type of the alias
                   declaration and that of its target.  Such
                   incompatibilities are typically indicative of bugs.
    
               **-Wattribute-alias=2**
                   At this level **-Wattribute-alias** also diagnoses cases where
                   the attributes of the alias declaration are more
                   restrictive than the attributes applied to its target.
                   These mismatches can potentially result in incorrect code
                   generation.  In other cases they may be benign and could
                   be resolved simply by adding the missing attribute to the
                   target.  For comparison, see the **-Wmissing-attributes**
                   option, which controls diagnostics when the alias
                   declaration is less restrictive than the target, rather
                   than more restrictive.
    
                   Attributes considered include "alloc_align", "alloc_size",
                   "cold", "const", "hot", "leaf", "malloc", "nonnull",
                   "noreturn", "nothrow", "pure", "returns_nonnull", and
                   "returns_twice".
    
               **-Wattribute-alias** is equivalent to **-Wattribute-alias=1**.  This
               is the default.  You can disable these warnings with either
               **-Wno-attribute-alias** or **-Wattribute-alias=0**.
    
           **-Wbool-compare**
               Warn about boolean expression compared with an integer value
               different from "true"/"false".  For instance, the following
               comparison is always false:
    
                       int n = 5;
                       ...
                       if ((n > 1) == 2) { ... }
    
               This warning is enabled by **-Wall**.
    
           **-Wbool-operation**
               Warn about suspicious operations on expressions of a boolean
               type.  For instance, bitwise negation of a boolean is very
               likely a bug in the program.  For C, this warning also warns
               about incrementing or decrementing a boolean, which rarely
               makes sense.  (In C++, decrementing a boolean is always
               invalid.  Incrementing a boolean is invalid in C++17, and
               deprecated otherwise.)
    
               This warning is enabled by **-Wall**.
    
           **-Wduplicated-branches**
               Warn when an if-else has identical branches.  This warning
               detects cases like
    
                       if (p != NULL)
                         return 0;
                       else
                         return 0;
    
               It doesn't warn when both branches contain just a null
               statement.  This warning also warn for conditional operators:
    
                         int i = x ? *p : *p;
    
           **-Wduplicated-cond**
               Warn about duplicated conditions in an if-else-if chain.  For
               instance, warn for the following code:
    
                       if (p->q != NULL) { ... }
                       else if (p->q != NULL) { ... }
    
           **-Wframe-address**
               Warn when the **__builtin_frame_address** or
               **__builtin_return_address** is called with an argument greater
               than 0.  Such calls may return indeterminate values or crash
               the program.  The warning is included in **-Wall**.
    
           **-Wno-discarded-qualifiers**(C and Objective-C only)
               Do not warn if type qualifiers on pointers are being
               discarded.  Typically, the compiler warns if a "const char *"
               variable is passed to a function that takes a "char *"
               parameter.  This option can be used to suppress such a
               warning.
    
           **-Wno-discarded-array-qualifiers**(C and Objective-C only)
               Do not warn if type qualifiers on arrays which are pointer
               targets are being discarded. Typically, the compiler warns if
               a "const int (*)[]" variable is passed to a function that
               takes a "int (*)[]" parameter.  This option can be used to
               suppress such a warning.
    
           **-Wno-incompatible-pointer-types**(C and Objective-C only)
               Do not warn when there is a conversion between pointers that
               have incompatible types.  This warning is for cases not
               covered by **-Wno-pointer-sign** , which warns for pointer argument
               passing or assignment with different signedness.
    
           **-Wno-int-conversion**(C and Objective-C only)
               Do not warn about incompatible integer to pointer and pointer
               to integer conversions.  This warning is about implicit
               conversions; for explicit conversions the warnings
               **-Wno-int-to-pointer-cast** and **-Wno-pointer-to-int-cast** may be
               used.
    
           **-Wno-div-by-zero**
               Do not warn about compile-time integer division by zero.
               Floating-point division by zero is not warned about, as it can
               be a legitimate way of obtaining infinities and NaNs.
    
           **-Wsystem-headers**
               Print warning messages for constructs found in system header
               files.  Warnings from system headers are normally suppressed,
               on the assumption that they usually do not indicate real
               problems and would only make the compiler output harder to
               read.  Using this command-line option tells GCC to emit
               warnings from system headers as if they occurred in user code.
               However, note that using **-Wall** in conjunction with this option
               does _not_ warn about unknown pragmas in system headers---for
               that, **-Wunknown-pragmas** must also be used.
    
           **-Wtautological-compare**
               Warn if a self-comparison always evaluates to true or false.
               This warning detects various mistakes such as:
    
                       int i = 1;
                       ...
                       if (i > i) { ... }
    
               This warning also warns about bitwise comparisons that always
               evaluate to true or false, for instance:
    
                       if ((a & 16) == 10) { ... }
    
               will always be false.
    
               This warning is enabled by **-Wall**.
    
           **-Wtrampolines**
               Warn about trampolines generated for pointers to nested
               functions.  A trampoline is a small piece of data or code that
               is created at run time on the stack when the address of a
               nested function is taken, and is used to call the nested
               function indirectly.  For some targets, it is made up of data
               only and thus requires no special treatment.  But, for most
               targets, it is made up of code and thus requires the stack to
               be made executable in order for the program to work properly.
    
           **-Wfloat-equal**
               Warn if floating-point values are used in equality
               comparisons.
    
               The idea behind this is that sometimes it is convenient (for
               the programmer) to consider floating-point values as
               approximations to infinitely precise real numbers.  If you are
               doing this, then you need to compute (by analyzing the code,
               or in some other way) the maximum or likely maximum error that
               the computation introduces, and allow for it when performing
               comparisons (and when producing output, but that's a different
               problem).  In particular, instead of testing for equality, you
               should check to see whether the two values have ranges that
               overlap; and this is done with the relational operators, so
               equality comparisons are probably mistaken.
    
           **-Wtraditional**(C and Objective-C only)
               Warn about certain constructs that behave differently in
               traditional and ISO C.  Also warn about ISO C constructs that
               have no traditional C equivalent, and/or problematic
               constructs that should be avoided.
    
               *   Macro parameters that appear within string literals in the
                   macro body.  In traditional C macro replacement takes
                   place within string literals, but in ISO C it does not.
    
               *   In traditional C, some preprocessor directives did not
                   exist.  Traditional preprocessors only considered a line
                   to be a directive if the **#** appeared in column 1 on the
                   line.  Therefore **-Wtraditional** warns about directives that
                   traditional C understands but ignores because the **#** does
                   not appear as the first character on the line.  It also
                   suggests you hide directives like "#pragma" not understood
                   by traditional C by indenting them.  Some traditional
                   implementations do not recognize "#elif", so this option
                   suggests avoiding it altogether.
    
               *   A function-like macro that appears without arguments.
    
               *   The unary plus operator.
    
               *   The **U** integer constant suffix, or the **F** or **L** floating-
                   point constant suffixes.  (Traditional C does support the
                   **L** suffix on integer constants.)  Note, these suffixes
                   appear in macros defined in the system headers of most
                   modern systems, e.g. the **_MIN** /**_MAX** macros in "<limits.h>".
                   Use of these macros in user code might normally lead to
                   spurious warnings, however GCC's integrated preprocessor
                   has enough context to avoid warning in these cases.
    
               *   A function declared external in one block and then used
                   after the end of the block.
    
               *   A "switch" statement has an operand of type "long".
    
               *   A non-"static" function declaration follows a "static"
                   one.  This construct is not accepted by some traditional C
                   compilers.
    
               *   The ISO type of an integer constant has a different width
                   or signedness from its traditional type.  This warning is
                   only issued if the base of the constant is ten.  I.e.
                   hexadecimal or octal values, which typically represent bit
                   patterns, are not warned about.
    
               *   Usage of ISO string concatenation is detected.
    
               *   Initialization of automatic aggregates.
    
               *   Identifier conflicts with labels.  Traditional C lacks a
                   separate namespace for labels.
    
               *   Initialization of unions.  If the initializer is zero, the
                   warning is omitted.  This is done under the assumption
                   that the zero initializer in user code appears conditioned
                   on e.g. "__STDC__" to avoid missing initializer warnings
                   and relies on default initialization to zero in the
                   traditional C case.
    
               *   Conversions by prototypes between fixed/floating-point
                   values and vice versa.  The absence of these prototypes
                   when compiling with traditional C causes serious problems.
                   This is a subset of the possible conversion warnings; for
                   the full set use **-Wtraditional-conversion**.
    
               *   Use of ISO C style function definitions.  This warning
                   intentionally is _not_ issued for prototype declarations or
                   variadic functions because these ISO C features appear in
                   your code when using libiberty's traditional C
                   compatibility macros, "PARAMS" and "VPARAMS".  This
                   warning is also bypassed for nested functions because that
                   feature is already a GCC extension and thus not relevant
                   to traditional C compatibility.
    
           **-Wtraditional-conversion**(C and Objective-C only)
               Warn if a prototype causes a type conversion that is different
               from what would happen to the same argument in the absence of
               a prototype.  This includes conversions of fixed point to
               floating and vice versa, and conversions changing the width or
               signedness of a fixed-point argument except when the same as
               the default promotion.
    
           **-Wdeclaration-after-statement**(C and Objective-C only)
               Warn when a declaration is found after a statement in a block.
               This construct, known from C++, was introduced with ISO C99
               and is by default allowed in GCC.  It is not supported by ISO
               C90.
    
           **-Wshadow**
               Warn whenever a local variable or type declaration shadows
               another variable, parameter, type, class member (in C++), or
               instance variable (in Objective-C) or whenever a built-in
               function is shadowed. Note that in C++, the compiler warns if
               a local variable shadows an explicit typedef, but not if it
               shadows a struct/class/enum.  Same as **-Wshadow=global**.
    
           **-Wno-shadow-ivar**(Objective-C only)
               Do not warn whenever a local variable shadows an instance
               variable in an Objective-C method.
    
           **-Wshadow=global**
               The default for **-Wshadow**. Warns for any (global) shadowing.
    
           **-Wshadow=local**
               Warn when a local variable shadows another local variable or
               parameter.  This warning is enabled by **-Wshadow=global**.
    
           **-Wshadow=compatible-local**
               Warn when a local variable shadows another local variable or
               parameter whose type is compatible with that of the shadowing
               variable. In C++, type compatibility here means the type of
               the shadowing variable can be converted to that of the
               shadowed variable. The creation of this flag (in addition to
               **-Wshadow=local**) is based on the idea that when a local
               variable shadows another one of incompatible type, it is most
               likely intentional, not a bug or typo, as shown in the
               following example:
    
                       for (SomeIterator i = SomeObj.begin(); i != SomeObj.end(); ++i)
                       {
                         for (int i = 0; i < N; ++i)
                         {
                           ...
                         }
                         ...
                       }
    
               Since the two variable "i" in the example above have
               incompatible types, enabling only **-Wshadow=compatible-local**
               will not emit a warning.  Because their types are
               incompatible, if a programmer accidentally uses one in place
               of the other, type checking will catch that and emit an error
               or warning. So not warning (about shadowing) in this case will
               not lead to undetected bugs. Use of this flag instead of
               **-Wshadow=local** can possibly reduce the number of warnings
               triggered by intentional shadowing.
    
               This warning is enabled by **-Wshadow=local**.
    
           **-Wlarger-than=**_byte-size_
               Warn whenever an object is defined whose size exceeds _byte-_
               _size_.  **-Wlarger-than=PTRDIFF_MAX** is enabled by default.
               Warnings controlled by the option can be disabled either by
               specifying _byte-size_ of **SIZE_MAX** or more or by
               **-Wno-larger-than**.
    
           **-Wno-larger-than**
               Disable **-Wlarger-than=** warnings.  The option is equivalent to
               **-Wlarger-than=SIZE_MAX** or larger.
    
           **-Wframe-larger-than=**_byte-size_
               Warn if the size of a function frame exceeds _byte-size_.  The
               computation done to determine the stack frame size is
               approximate and not conservative.  The actual requirements may
               be somewhat greater than _byte-size_ even if you do not get a
               warning.  In addition, any space allocated via "alloca",
               variable-length arrays, or related constructs is not included
               by the compiler when determining whether or not to issue a
               warning.  **-Wframe-larger-than=PTRDIFF_MAX** is enabled by
               default.  Warnings controlled by the option can be disabled
               either by specifying _byte-size_ of **SIZE_MAX** or more or by
               **-Wno-frame-larger-than**.
    
           **-Wno-frame-larger-than**
               Disable **-Wframe-larger-than=** warnings.  The option is
               equivalent to **-Wframe-larger-than=SIZE_MAX** or larger.
    
           **-Wno-free-nonheap-object**
               Do not warn when attempting to free an object that was not
               allocated on the heap.
    
           **-Wstack-usage=**_byte-size_
               Warn if the stack usage of a function might exceed _byte-size_.
               The computation done to determine the stack usage is
               conservative.  Any space allocated via "alloca", variable-
               length arrays, or related constructs is included by the
               compiler when determining whether or not to issue a warning.
    
               The message is in keeping with the output of **-fstack-usage**.
    
               *   If the stack usage is fully static but exceeds the
                   specified amount, it's:
    
                             warning: stack usage is 1120 bytes
    
               *   If the stack usage is (partly) dynamic but bounded, it's:
    
                             warning: stack usage might be 1648 bytes
    
               *   If the stack usage is (partly) dynamic and not bounded,
                   it's:
    
                             warning: stack usage might be unbounded
    
               **-Wstack-usage=PTRDIFF_MAX** is enabled by default.  Warnings
               controlled by the option can be disabled either by specifying
               _byte-size_ of **SIZE_MAX** or more or by **-Wno-stack-usage**.
    
           **-Wno-stack-usage**
               Disable **-Wstack-usage=** warnings.  The option is equivalent to
               **-Wstack-usage=SIZE_MAX** or larger.
    
           **-Wunsafe-loop-optimizations**
               Warn if the loop cannot be optimized because the compiler
               cannot assume anything on the bounds of the loop indices.
               With **-funsafe-loop-optimizations** warn if the compiler makes
               such assumptions.
    
           **-Wno-pedantic-ms-format**(MinGW targets only)
               When used in combination with **-Wformat** and **-pedantic** without
               GNU extensions, this option disables the warnings about non-
               ISO "printf" / "scanf" format width specifiers "I32", "I64",
               and "I" used on Windows targets, which depend on the MS
               runtime.
    
           **-Waligned-new**
               Warn about a new-expression of a type that requires greater
               alignment than the "alignof(std::max_align_t)" but uses an
               allocation function without an explicit alignment parameter.
               This option is enabled by **-Wall**.
    
               Normally this only warns about global allocation functions,
               but **-Waligned-new=all** also warns about class member allocation
               functions.
    
           **-Wplacement-new**
           **-Wplacement-new=**_n_
               Warn about placement new expressions with undefined behavior,
               such as constructing an object in a buffer that is smaller
               than the type of the object.  For example, the placement new
               expression below is diagnosed because it attempts to construct
               an array of 64 integers in a buffer only 64 bytes large.
    
                       char buf [64];
                       new (buf) int[64];
    
               This warning is enabled by default.
    
               **-Wplacement-new=1**
                   This is the default warning level of **-Wplacement-new**.  At
                   this level the warning is not issued for some strictly
                   undefined constructs that GCC allows as extensions for
                   compatibility with legacy code.  For example, the
                   following "new" expression is not diagnosed at this level
                   even though it has undefined behavior according to the C++
                   standard because it writes past the end of the one-element
                   array.
    
                           struct S { int n, a[1]; };
                           S *s = (S *)malloc (sizeof *s + 31 * sizeof s->a[0]);
                           new (s->a)int [32]();
    
               **-Wplacement-new=2**
                   At this level, in addition to diagnosing all the same
                   constructs as at level 1, a diagnostic is also issued for
                   placement new expressions that construct an object in the
                   last member of structure whose type is an array of a
                   single element and whose size is less than the size of the
                   object being constructed.  While the previous example
                   would be diagnosed, the following construct makes use of
                   the flexible member array extension to avoid the warning
                   at level 2.
    
                           struct S { int n, a[]; };
                           S *s = (S *)malloc (sizeof *s + 32 * sizeof s->a[0]);
                           new (s->a)int [32]();
    
           **-Wpointer-arith**
               Warn about anything that depends on the "size of" a function
               type or of "void".  GNU C assigns these types a size of 1, for
               convenience in calculations with "void *" pointers and
               pointers to functions.  In C++, warn also when an arithmetic
               operation involves "NULL".  This warning is also enabled by
               **-Wpedantic**.
    
           **-Wpointer-compare**
               Warn if a pointer is compared with a zero character constant.
               This usually means that the pointer was meant to be
               dereferenced.  For example:
    
                       const char *p = foo ();
                       if (p == '\0')
                         return 42;
    
               Note that the code above is invalid in C++11.
    
               This warning is enabled by default.
    
           **-Wtype-limits**
               Warn if a comparison is always true or always false due to the
               limited range of the data type, but do not warn for constant
               expressions.  For example, warn if an unsigned variable is
               compared against zero with "<" or ">=".  This warning is also
               enabled by **-Wextra**.
    
           **-Wabsolute-value**(C and Objective-C only)
               Warn for calls to standard functions that compute the absolute
               value of an argument when a more appropriate standard function
               is available.  For example, calling "abs(3.14)" triggers the
               warning because the appropriate function to call to compute
               the absolute value of a double argument is "fabs".  The option
               also triggers warnings when the argument in a call to such a
               function has an unsigned type.  This warning can be suppressed
               with an explicit type cast and it is also enabled by **-Wextra**.
    
           **-Wcomment**
           **-Wcomments**
               Warn whenever a comment-start sequence **/*** appears in a **/***
               comment, or whenever a backslash-newline appears in a **//**
               comment.  This warning is enabled by **-Wall**.
    
           **-Wtrigraphs**
               Warn if any trigraphs are encountered that might change the
               meaning of the program.  Trigraphs within comments are not
               warned about, except those that would form escaped newlines.
    
               This option is implied by **-Wall**.  If **-Wall** is not given, this
               option is still enabled unless trigraphs are enabled.  To get
               trigraph conversion without warnings, but get the other **-Wall**
               warnings, use **-trigraphs -Wall -Wno-trigraphs**.
    
           **-Wundef**
               Warn if an undefined identifier is evaluated in an "#if"
               directive.  Such identifiers are replaced with zero.
    
           **-Wexpansion-to-defined**
               Warn whenever **defined** is encountered in the expansion of a
               macro (including the case where the macro is expanded by an
               **#if** directive).  Such usage is not portable.  This warning is
               also enabled by **-Wpedantic** and **-Wextra**.
    
           **-Wunused-macros**
               Warn about macros defined in the main file that are unused.  A
               macro is _used_ if it is expanded or tested for existence at
               least once.  The preprocessor also warns if the macro has not
               been used at the time it is redefined or undefined.
    
               Built-in macros, macros defined on the command line, and
               macros defined in include files are not warned about.
    
               _Note:_ If a macro is actually used, but only used in skipped
               conditional blocks, then the preprocessor reports it as
               unused.  To avoid the warning in such a case, you might
               improve the scope of the macro's definition by, for example,
               moving it into the first skipped block.  Alternatively, you
               could provide a dummy use with something like:
    
                       #if defined the_macro_causing_the_warning
                       #endif
    
           **-Wno-endif-labels**
               Do not warn whenever an "#else" or an "#endif" are followed by
               text.  This sometimes happens in older programs with code of
               the form
    
                       #if FOO
                       ...
                       #else FOO
                       ...
                       #endif FOO
    
               The second and third "FOO" should be in comments.  This
               warning is on by default.
    
           **-Wbad-function-cast**(C and Objective-C only)
               Warn when a function call is cast to a non-matching type.  For
               example, warn if a call to a function returning an integer
               type is cast to a pointer type.
    
           **-Wc90-c99-compat**(C and Objective-C only)
               Warn about features not present in ISO C90, but present in ISO
               C99.  For instance, warn about use of variable length arrays,
               "long long" type, "bool" type, compound literals, designated
               initializers, and so on.  This option is independent of the
               standards mode.  Warnings are disabled in the expression that
               follows "__extension__".
    
           **-Wc99-c11-compat**(C and Objective-C only)
               Warn about features not present in ISO C99, but present in ISO
               C11.  For instance, warn about use of anonymous structures and
               unions, "_Atomic" type qualifier, "_Thread_local" storage-
               class specifier, "_Alignas" specifier, "Alignof" operator,
               "_Generic" keyword, and so on.  This option is independent of
               the standards mode.  Warnings are disabled in the expression
               that follows "__extension__".
    
           **-Wc11-c2x-compat**(C and Objective-C only)
               Warn about features not present in ISO C11, but present in ISO
               C2X.  For instance, warn about omitting the string in
               "_Static_assert".  This option is independent of the standards
               mode.  Warnings are disabled in the expression that follows
               "__extension__".
    
           **-Wc++-compat**(C and Objective-C only)
               Warn about ISO C constructs that are outside of the common
               subset of ISO C and ISO C++, e.g. request for implicit
               conversion from "void *" to a pointer to non-"void" type.
    
           **-Wc++11-compat**(C++ and Objective-C++ only)
               Warn about C++ constructs whose meaning differs between ISO
               C++ 1998 and ISO C++ 2011, e.g., identifiers in ISO C++ 1998
               that are keywords in ISO C++ 2011.  This warning turns on
               **-Wnarrowing** and is enabled by **-Wall**.
    
           **-Wc++14-compat**(C++ and Objective-C++ only)
               Warn about C++ constructs whose meaning differs between ISO
               C++ 2011 and ISO C++ 2014.  This warning is enabled by **-Wall**.
    
           **-Wc++17-compat**(C++ and Objective-C++ only)
               Warn about C++ constructs whose meaning differs between ISO
               C++ 2014 and ISO C++ 2017.  This warning is enabled by **-Wall**.
    
           **-Wcast-qual**
               Warn whenever a pointer is cast so as to remove a type
               qualifier from the target type.  For example, warn if a "const
               char *" is cast to an ordinary "char *".
    
               Also warn when making a cast that introduces a type qualifier
               in an unsafe way.  For example, casting "char **" to "const
               char **" is unsafe, as in this example:
    
                         /* p is char ** value.  */
                         const char **q = (const char **) p;
                         /* Assignment of readonly string to const char * is OK.  */
                         *q = "string";
                         /* Now char** pointer points to read-only memory.  */
                         **p = 'b';
    
           **-Wcast-align**
               Warn whenever a pointer is cast such that the required
               alignment of the target is increased.  For example, warn if a
               "char *" is cast to an "int *" on machines where integers can
               only be accessed at two- or four-byte boundaries.
    
           **-Wcast-align=strict**
               Warn whenever a pointer is cast such that the required
               alignment of the target is increased.  For example, warn if a
               "char *" is cast to an "int *" regardless of the target
               machine.
    
           **-Wcast-function-type**
               Warn when a function pointer is cast to an incompatible
               function pointer.  In a cast involving function types with a
               variable argument list only the types of initial arguments
               that are provided are considered.  Any parameter of pointer-
               type matches any other pointer-type.  Any benign differences
               in integral types are ignored, like "int" vs. "long" on ILP32
               targets.  Likewise type qualifiers are ignored.  The function
               type "void (*) (void)" is special and matches everything,
               which can be used to suppress this warning.  In a cast
               involving pointer to member types this warning warns whenever
               the type cast is changing the pointer to member type.  This
               warning is enabled by **-Wextra**.
    
           **-Wwrite-strings**
               When compiling C, give string constants the type "const
               char[_length]"_ so that copying the address of one into a
               non-"const" "char *" pointer produces a warning.  These
               warnings help you find at compile time code that can try to
               write into a string constant, but only if you have been very
               careful about using "const" in declarations and prototypes.
               Otherwise, it is just a nuisance. This is why we did not make
               **-Wall** request these warnings.
    
               When compiling C++, warn about the deprecated conversion from
               string literals to "char *".  This warning is enabled by
               default for C++ programs.
    
           **-Wcatch-value**
           **-Wcatch-value=**_n_ (C++ and Objective-C++ only)
               Warn about catch handlers that do not catch via reference.
               With **-Wcatch-value=1**(or **-Wcatch-value** for short) warn about
               polymorphic class types that are caught by value.  With
               **-Wcatch-value=2** warn about all class types that are caught by
               value. With **-Wcatch-value=3** warn about all types that are not
               caught by reference. **-Wcatch-value** is enabled by **-Wall**.
    
           **-Wclobbered**
               Warn for variables that might be changed by "longjmp" or
               "vfork".  This warning is also enabled by **-Wextra**.
    
           **-Wconditionally-supported**(C++ and Objective-C++ only)
               Warn for conditionally-supported (C++11 [intro.defs])
               constructs.
    
           **-Wconversion**
               Warn for implicit conversions that may alter a value. This
               includes conversions between real and integer, like "abs (x)"
               when "x" is "double"; conversions between signed and unsigned,
               like "unsigned ui = -1"; and conversions to smaller types,
               like "sqrtf (M_PI)". Do not warn for explicit casts like "abs
               ((int) x)" and "ui = (unsigned) -1", or if the value is not
               changed by the conversion like in "abs (2.0)".  Warnings about
               conversions between signed and unsigned integers can be
               disabled by using **-Wno-sign-conversion**.
    
               For C++, also warn for confusing overload resolution for user-
               defined conversions; and conversions that never use a type
               conversion operator: conversions to "void", the same type, a
               base class or a reference to them. Warnings about conversions
               between signed and unsigned integers are disabled by default
               in C++ unless **-Wsign-conversion** is explicitly enabled.
    
           **-Wno-conversion-null**(C++ and Objective-C++ only)
               Do not warn for conversions between "NULL" and non-pointer
               types. **-Wconversion-null** is enabled by default.
    
           **-Wzero-as-null-pointer-constant**(C++ and Objective-C++ only)
               Warn when a literal **0** is used as null pointer constant.  This
               can be useful to facilitate the conversion to "nullptr" in
               C++11.
    
           **-Wsubobject-linkage**(C++ and Objective-C++ only)
               Warn if a class type has a base or a field whose type uses the
               anonymous namespace or depends on a type with no linkage.  If
               a type A depends on a type B with no or internal linkage,
               defining it in multiple translation units would be an ODR
               violation because the meaning of B is different in each
               translation unit.  If A only appears in a single translation
               unit, the best way to silence the warning is to give it
               internal linkage by putting it in an anonymous namespace as
               well.  The compiler doesn't give this warning for types
               defined in the main .C file, as those are unlikely to have
               multiple definitions.  **-Wsubobject-linkage** is enabled by
               default.
    
           **-Wdangling-else**
               Warn about constructions where there may be confusion to which
               "if" statement an "else" branch belongs.  Here is an example
               of such a case:
    
                       {
                         if (a)
                           if (b)
                             foo ();
                         else
                           bar ();
                       }
    
               In C/C++, every "else" branch belongs to the innermost
               possible "if" statement, which in this example is "if (b)".
               This is often not what the programmer expected, as illustrated
               in the above example by indentation the programmer chose.
               When there is the potential for this confusion, GCC issues a
               warning when this flag is specified.  To eliminate the
               warning, add explicit braces around the innermost "if"
               statement so there is no way the "else" can belong to the
               enclosing "if".  The resulting code looks like this:
    
                       {
                         if (a)
                           {
                             if (b)
                               foo ();
                             else
                               bar ();
                           }
                       }
    
               This warning is enabled by **-Wparentheses**.
    
           **-Wdate-time**
               Warn when macros "__TIME__", "__DATE__" or "__TIMESTAMP__" are
               encountered as they might prevent bit-wise-identical
               reproducible compilations.
    
           **-Wdelete-incomplete**(C++ and Objective-C++ only)
               Warn when deleting a pointer to incomplete type, which may
               cause undefined behavior at runtime.  This warning is enabled
               by default.
    
           **-Wuseless-cast**(C++ and Objective-C++ only)
               Warn when an expression is casted to its own type.
    
           **-Wempty-body**
               Warn if an empty body occurs in an "if", "else" or "do while"
               statement.  This warning is also enabled by **-Wextra**.
    
           **-Wenum-compare**
               Warn about a comparison between values of different enumerated
               types.  In C++ enumerated type mismatches in conditional
               expressions are also diagnosed and the warning is enabled by
               default.  In C this warning is enabled by **-Wall**.
    
           **-Wextra-semi**(C++, Objective-C++ only)
               Warn about redundant semicolon after in-class function
               definition.
    
           **-Wjump-misses-init**(C, Objective-C only)
               Warn if a "goto" statement or a "switch" statement jumps
               forward across the initialization of a variable, or jumps
               backward to a label after the variable has been initialized.
               This only warns about variables that are initialized when they
               are declared.  This warning is only supported for C and
               Objective-C; in C++ this sort of branch is an error in any
               case.
    
               **-Wjump-misses-init** is included in **-Wc++-compat**.  It can be
               disabled with the **-Wno-jump-misses-init** option.
    
           **-Wsign-compare**
               Warn when a comparison between signed and unsigned values
               could produce an incorrect result when the signed value is
               converted to unsigned.  In C++, this warning is also enabled
               by **-Wall**.  In C, it is also enabled by **-Wextra**.
    
           **-Wsign-conversion**
               Warn for implicit conversions that may change the sign of an
               integer value, like assigning a signed integer expression to
               an unsigned integer variable. An explicit cast silences the
               warning. In C, this option is enabled also by **-Wconversion**.
    
           **-Wfloat-conversion**
               Warn for implicit conversions that reduce the precision of a
               real value.  This includes conversions from real to integer,
               and from higher precision real to lower precision real values.
               This option is also enabled by **-Wconversion**.
    
           **-Wno-scalar-storage-order**
               Do not warn on suspicious constructs involving reverse scalar
               storage order.
    
           **-Wsized-deallocation**(C++ and Objective-C++ only)
               Warn about a definition of an unsized deallocation function
    
                       void operator delete (void *) noexcept;
                       void operator delete[] (void *) noexcept;
    
               without a definition of the corresponding sized deallocation
               function
    
                       void operator delete (void *, std::size_t) noexcept;
                       void operator delete[] (void *, std::size_t) noexcept;
    
               or vice versa.  Enabled by **-Wextra** along with
               **-fsized-deallocation**.
    
           **-Wsizeof-pointer-div**
               Warn for suspicious divisions of two sizeof expressions that
               divide the pointer size by the element size, which is the
               usual way to compute the array size but won't work out
               correctly with pointers.  This warning warns e.g. about
               "sizeof (ptr) / sizeof (ptr[0])" if "ptr" is not an array, but
               a pointer.  This warning is enabled by **-Wall**.
    
           **-Wsizeof-pointer-memaccess**
               Warn for suspicious length parameters to certain string and
               memory built-in functions if the argument uses "sizeof".  This
               warning triggers for example for "memset (ptr, 0, sizeof
               (ptr));" if "ptr" is not an array, but a pointer, and suggests
               a possible fix, or about "memcpy (&foo, ptr, sizeof (&foo));".
               **-Wsizeof-pointer-memaccess** also warns about calls to bounded
               string copy functions like "strncat" or "strncpy" that specify
               as the bound a "sizeof" expression of the source array.  For
               example, in the following function the call to "strncat"
               specifies the size of the source string as the bound.  That is
               almost certainly a mistake and so the call is diagnosed.
    
                       void make_file (const char *name)
                       {
                         char path[PATH_MAX];
                         strncpy (path, name, sizeof path - 1);
                         strncat (path, ".text", sizeof ".text");
                         ...
                       }
    
               The **-Wsizeof-pointer-memaccess** option is enabled by **-Wall**.
    
           **-Wsizeof-array-argument**
               Warn when the "sizeof" operator is applied to a parameter that
               is declared as an array in a function definition.  This
               warning is enabled by default for C and C++ programs.
    
           **-Wmemset-elt-size**
               Warn for suspicious calls to the "memset" built-in function,
               if the first argument references an array, and the third
               argument is a number equal to the number of elements, but not
               equal to the size of the array in memory.  This indicates that
               the user has omitted a multiplication by the element size.
               This warning is enabled by **-Wall**.
    
           **-Wmemset-transposed-args**
               Warn for suspicious calls to the "memset" built-in function
               where the second argument is not zero and the third argument
               is zero.  For example, the call "memset (buf, sizeof buf, 0)"
               is diagnosed because "memset (buf, 0, sizeof buf)" was meant
               instead.  The diagnostic is only emitted if the third argument
               is a literal zero.  Otherwise, if it is an expression that is
               folded to zero, or a cast of zero to some type, it is far less
               likely that the arguments have been mistakenly transposed and
               no warning is emitted.  This warning is enabled by **-Wall**.
    
           **-Waddress**
               Warn about suspicious uses of memory addresses. These include
               using the address of a function in a conditional expression,
               such as "void func(void); if (func)", and comparisons against
               the memory address of a string literal, such as "if (x ==
               "abc")".  Such uses typically indicate a programmer error: the
               address of a function always evaluates to true, so their use
               in a conditional usually indicate that the programmer forgot
               the parentheses in a function call; and comparisons against
               string literals result in unspecified behavior and are not
               portable in C, so they usually indicate that the programmer
               intended to use "strcmp".  This warning is enabled by **-Wall**.
    
           **-Waddress-of-packed-member**
               Warn when the address of packed member of struct or union is
               taken, which usually results in an unaligned pointer value.
               This is enabled by default.
    
           **-Wlogical-op**
               Warn about suspicious uses of logical operators in
               expressions.  This includes using logical operators in
               contexts where a bit-wise operator is likely to be expected.
               Also warns when the operands of a logical operator are the
               same:
    
                       extern int a;
                       if (a < 0 && a < 0) { ... }
    
           **-Wlogical-not-parentheses**
               Warn about logical not used on the left hand side operand of a
               comparison.  This option does not warn if the right operand is
               considered to be a boolean expression.  Its purpose is to
               detect suspicious code like the following:
    
                       int a;
                       ...
                       if (!a > 1) { ... }
    
               It is possible to suppress the warning by wrapping the LHS
               into parentheses:
    
                       if ((!a) > 1) { ... }
    
               This warning is enabled by **-Wall**.
    
           **-Waggregate-return**
               Warn if any functions that return structures or unions are
               defined or called.  (In languages where you can return an
               array, this also elicits a warning.)
    
           **-Wno-aggressive-loop-optimizations**
               Warn if in a loop with constant number of iterations the
               compiler detects undefined behavior in some statement during
               one or more of the iterations.
    
           **-Wno-attributes**
               Do not warn if an unexpected "__attribute__" is used, such as
               unrecognized attributes, function attributes applied to
               variables, etc.  This does not stop errors for incorrect use
               of supported attributes.
    
           **-Wno-builtin-declaration-mismatch**
               Warn if a built-in function is declared with an incompatible
               signature or as a non-function, or when a built-in function
               declared with a type that does not include a prototype is
               called with arguments whose promoted types do not match those
               expected by the function.  When **-Wextra** is specified, also
               warn when a built-in function that takes arguments is declared
               without a prototype.  The **-Wno-builtin-declaration-mismatch**
               warning is enabled by default.  To avoid the warning include
               the appropriate header to bring the prototypes of built-in
               functions into scope.
    
               For example, the call to "memset" below is diagnosed by the
               warning because the function expects a value of type "size_t"
               as its argument but the type of 32 is "int".  With **-Wextra** ,
               the declaration of the function is diagnosed as well.
    
                       extern void* memset ();
                       void f (void *d)
                       {
                         memset (d, '\0', 32);
                       }
    
           **-Wno-builtin-macro-redefined**
               Do not warn if certain built-in macros are redefined.  This
               suppresses warnings for redefinition of "__TIMESTAMP__",
               "__TIME__", "__DATE__", "__FILE__", and "__BASE_FILE__".
    
           **-Wstrict-prototypes**(C and Objective-C only)
               Warn if a function is declared or defined without specifying
               the argument types.  (An old-style function definition is
               permitted without a warning if preceded by a declaration that
               specifies the argument types.)
    
           **-Wold-style-declaration**(C and Objective-C only)
               Warn for obsolescent usages, according to the C Standard, in a
               declaration. For example, warn if storage-class specifiers
               like "static" are not the first things in a declaration.  This
               warning is also enabled by **-Wextra**.
    
           **-Wold-style-definition**(C and Objective-C only)
               Warn if an old-style function definition is used.  A warning
               is given even if there is a previous prototype.
    
           **-Wmissing-parameter-type**(C and Objective-C only)
               A function parameter is declared without a type specifier in
               K&R-style functions:
    
                       void foo(bar) { }
    
               This warning is also enabled by **-Wextra**.
    
           **-Wmissing-prototypes**(C and Objective-C only)
               Warn if a global function is defined without a previous
               prototype declaration.  This warning is issued even if the
               definition itself provides a prototype.  Use this option to
               detect global functions that do not have a matching prototype
               declaration in a header file.  This option is not valid for
               C++ because all function declarations provide prototypes and a
               non-matching declaration declares an overload rather than
               conflict with an earlier declaration.  Use
               **-Wmissing-declarations** to detect missing declarations in C++.
    
           **-Wmissing-declarations**
               Warn if a global function is defined without a previous
               declaration.  Do so even if the definition itself provides a
               prototype.  Use this option to detect global functions that
               are not declared in header files.  In C, no warnings are
               issued for functions with previous non-prototype declarations;
               use **-Wmissing-prototypes** to detect missing prototypes.  In
               C++, no warnings are issued for function templates, or for
               inline functions, or for functions in anonymous namespaces.
    
           **-Wmissing-field-initializers**
               Warn if a structure's initializer has some fields missing.
               For example, the following code causes such a warning, because
               "x.h" is implicitly zero:
    
                       struct s { int f, g, h; };
                       struct s x = { 3, 4 };
    
               This option does not warn about designated initializers, so
               the following modification does not trigger a warning:
    
                       struct s { int f, g, h; };
                       struct s x = { .f = 3, .g = 4 };
    
               In C this option does not warn about the universal zero
               initializer **{ 0 }** :
    
                       struct s { int f, g, h; };
                       struct s x = { 0 };
    
               Likewise, in C++ this option does not warn about the empty { }
               initializer, for example:
    
                       struct s { int f, g, h; };
                       s x = { };
    
               This warning is included in **-Wextra**.  To get other **-Wextra**
               warnings without this one, use **-Wextra**
               **-Wno-missing-field-initializers**.
    
           **-Wno-multichar**
               Do not warn if a multicharacter constant (**'FOOF'**) is used.
               Usually they indicate a typo in the user's code, as they have
               implementation-defined values, and should not be used in
               portable code.
    
           **-Wnormalized=**[**none** |**id** |**nfc** |**nfkc**]
               In ISO C and ISO C++, two identifiers are different if they
               are different sequences of characters.  However, sometimes
               when characters outside the basic ASCII character set are
               used, you can have two different character sequences that look
               the same.  To avoid confusion, the ISO 10646 standard sets out
               some _normalization rules_ which when applied ensure that two
               sequences that look the same are turned into the same
               sequence.  GCC can warn you if you are using identifiers that
               have not been normalized; this option controls that warning.
    
               There are four levels of warning supported by GCC.  The
               default is **-Wnormalized=nfc** , which warns about any identifier
               that is not in the ISO 10646 "C" normalized form, _NFC_.  NFC is
               the recommended form for most uses.  It is equivalent to
               **-Wnormalized**.
    
               Unfortunately, there are some characters allowed in
               identifiers by ISO C and ISO C++ that, when turned into NFC,
               are not allowed in identifiers.  That is, there's no way to
               use these symbols in portable ISO C or C++ and have all your
               identifiers in NFC.  **-Wnormalized=id** suppresses the warning
               for these characters.  It is hoped that future versions of the
               standards involved will correct this, which is why this option
               is not the default.
    
               You can switch the warning off for all characters by writing
               **-Wnormalized=none** or **-Wno-normalized**.  You should only do this
               if you are using some other normalization scheme (like "D"),
               because otherwise you can easily create bugs that are
               literally impossible to see.
    
               Some characters in ISO 10646 have distinct meanings but look
               identical in some fonts or display methodologies, especially
               once formatting has been applied.  For instance "\u207F",
               "SUPERSCRIPT LATIN SMALL LETTER N", displays just like a
               regular "n" that has been placed in a superscript.  ISO 10646
               defines the _NFKC_ normalization scheme to convert all these
               into a standard form as well, and GCC warns if your code is
               not in NFKC if you use **-Wnormalized=nfkc**.  This warning is
               comparable to warning about every identifier that contains the
               letter O because it might be confused with the digit 0, and so
               is not the default, but may be useful as a local coding
               convention if the programming environment cannot be fixed to
               display these characters distinctly.
    
           **-Wno-attribute-warning**
               Do not warn about usage of functions declared with "warning"
               attribute.  By default, this warning is enabled.
               **-Wno-attribute-warning** can be used to disable the warning or
               **-Wno-error=attribute-warning** can be used to disable the error
               when compiled with **-Werror** flag.
    
           **-Wno-deprecated**
               Do not warn about usage of deprecated features.
    
           **-Wno-deprecated-declarations**
               Do not warn about uses of functions, variables, and types
               marked as deprecated by using the "deprecated" attribute.
    
           **-Wno-overflow**
               Do not warn about compile-time overflow in constant
               expressions.
    
           **-Wno-odr**
               Warn about One Definition Rule violations during link-time
               optimization.  Requires **-flto-odr-type-merging** to be enabled.
               Enabled by default.
    
           **-Wopenmp-simd**
               Warn if the vectorizer cost model overrides the OpenMP simd
               directive set by user.  The **-fsimd-cost-model=unlimited** option
               can be used to relax the cost model.
    
           **-Woverride-init**(C and Objective-C only)
               Warn if an initialized field without side effects is
               overridden when using designated initializers.
    
               This warning is included in **-Wextra**.  To get other **-Wextra**
               warnings without this one, use **-Wextra -Wno-override-init**.
    
           **-Woverride-init-side-effects**(C and Objective-C only)
               Warn if an initialized field with side effects is overridden
               when using designated initializers.  This warning is enabled
               by default.
    
           **-Wpacked**
               Warn if a structure is given the packed attribute, but the
               packed attribute has no effect on the layout or size of the
               structure.  Such structures may be mis-aligned for little
               benefit.  For instance, in this code, the variable "f.x" in
               "struct bar" is misaligned even though "struct bar" does not
               itself have the packed attribute:
    
                       struct foo {
                         int x;
                         char a, b, c, d;
                       } __attribute__((packed));
                       struct bar {
                         char z;
                         struct foo f;
                       };
    
           **-Wpacked-bitfield-compat**
               The 4.1, 4.2 and 4.3 series of GCC ignore the "packed"
               attribute on bit-fields of type "char".  This has been fixed
               in GCC 4.4 but the change can lead to differences in the
               structure layout.  GCC informs you when the offset of such a
               field has changed in GCC 4.4.  For example there is no longer
               a 4-bit padding between field "a" and "b" in this structure:
    
                       struct foo
                       {
                         char a:4;
                         char b:8;
                       } __attribute__ ((packed));
    
               This warning is enabled by default.  Use
               **-Wno-packed-bitfield-compat** to disable this warning.
    
           **-Wpacked-not-aligned**(C, C++, Objective-C and Objective-C++ only)
               Warn if a structure field with explicitly specified alignment
               in a packed struct or union is misaligned.  For example, a
               warning will be issued on "struct S", like, "warning:
               alignment 1 of 'struct S' is less than 8", in this code:
    
                       struct __attribute__ ((aligned (8))) S8 { char a[8]; };
                       struct __attribute__ ((packed)) S {
                         struct S8 s8;
                       };
    
               This warning is enabled by **-Wall**.
    
           **-Wpadded**
               Warn if padding is included in a structure, either to align an
               element of the structure or to align the whole structure.
               Sometimes when this happens it is possible to rearrange the
               fields of the structure to reduce the padding and so make the
               structure smaller.
    
           **-Wredundant-decls**
               Warn if anything is declared more than once in the same scope,
               even in cases where multiple declaration is valid and changes
               nothing.
    
           **-Wno-restrict**
               Warn when an object referenced by a "restrict"-qualified
               parameter (or, in C++, a "__restrict"-qualified parameter) is
               aliased by another argument, or when copies between such
               objects overlap.  For example, the call to the "strcpy"
               function below attempts to truncate the string by replacing
               its initial characters with the last four.  However, because
               the call writes the terminating NUL into "a[4]", the copies
               overlap and the call is diagnosed.
    
                       void foo (void)
                       {
                         char a[] = "abcd1234";
                         strcpy (a, a + 4);
                         ...
                       }
    
               The **-Wrestrict** option detects some instances of simple overlap
               even without optimization but works best at **-O2** and above.  It
               is included in **-Wall**.
    
           **-Wnested-externs**(C and Objective-C only)
               Warn if an "extern" declaration is encountered within a
               function.
    
           **-Wno-inherited-variadic-ctor**
               Suppress warnings about use of C++11 inheriting constructors
               when the base class inherited from has a C variadic
               constructor; the warning is on by default because the ellipsis
               is not inherited.
    
           **-Winline**
               Warn if a function that is declared as inline cannot be
               inlined.  Even with this option, the compiler does not warn
               about failures to inline functions declared in system headers.
    
               The compiler uses a variety of heuristics to determine whether
               or not to inline a function.  For example, the compiler takes
               into account the size of the function being inlined and the
               amount of inlining that has already been done in the current
               function.  Therefore, seemingly insignificant changes in the
               source program can cause the warnings produced by **-Winline** to
               appear or disappear.
    
           **-Wno-invalid-offsetof**(C++ and Objective-C++ only)
               Suppress warnings from applying the "offsetof" macro to a non-
               POD type.  According to the 2014 ISO C++ standard, applying
               "offsetof" to a non-standard-layout type is undefined.  In
               existing C++ implementations, however, "offsetof" typically
               gives meaningful results.  This flag is for users who are
               aware that they are writing nonportable code and who have
               deliberately chosen to ignore the warning about it.
    
               The restrictions on "offsetof" may be relaxed in a future
               version of the C++ standard.
    
           **-Wint-in-bool-context**
               Warn for suspicious use of integer values where boolean values
               are expected, such as conditional expressions (?:) using non-
               boolean integer constants in boolean context, like "if (a <= b
               ? 2 : 3)".  Or left shifting of signed integers in boolean
               context, like "for (a = 0; 1 << a; a++);".  Likewise for all
               kinds of multiplications regardless of the data type.  This
               warning is enabled by **-Wall**.
    
           **-Wno-int-to-pointer-cast**
               Suppress warnings from casts to pointer type of an integer of
               a different size. In C++, casting to a pointer type of smaller
               size is an error. **Wint-to-pointer-cast** is enabled by default.
    
           **-Wno-pointer-to-int-cast**(C and Objective-C only)
               Suppress warnings from casts from a pointer to an integer type
               of a different size.
    
           **-Winvalid-pch**
               Warn if a precompiled header is found in the search path but
               cannot be used.
    
           **-Wlong-long**
               Warn if "long long" type is used.  This is enabled by either
               **-Wpedantic** or **-Wtraditional** in ISO C90 and C++98 modes.  To
               inhibit the warning messages, use **-Wno-long-long**.
    
           **-Wvariadic-macros**
               Warn if variadic macros are used in ISO C90 mode, or if the
               GNU alternate syntax is used in ISO C99 mode.  This is enabled
               by either **-Wpedantic** or **-Wtraditional**.  To inhibit the warning
               messages, use **-Wno-variadic-macros**.
    
           **-Wvarargs**
               Warn upon questionable usage of the macros used to handle
               variable arguments like "va_start".  This is default.  To
               inhibit the warning messages, use **-Wno-varargs**.
    
           **-Wvector-operation-performance**
               Warn if vector operation is not implemented via SIMD
               capabilities of the architecture.  Mainly useful for the
               performance tuning.  Vector operation can be implemented
               "piecewise", which means that the scalar operation is
               performed on every vector element; "in parallel", which means
               that the vector operation is implemented using scalars of
               wider type, which normally is more performance efficient; and
               "as a single scalar", which means that vector fits into a
               scalar type.
    
           **-Wno-virtual-move-assign**
               Suppress warnings about inheriting from a virtual base with a
               non-trivial C++11 move assignment operator.  This is dangerous
               because if the virtual base is reachable along more than one
               path, it is moved multiple times, which can mean both objects
               end up in the moved-from state.  If the move assignment
               operator is written to avoid moving from a moved-from object,
               this warning can be disabled.
    
           **-Wvla**
               Warn if a variable-length array is used in the code.  **-Wno-vla**
               prevents the **-Wpedantic** warning of the variable-length array.
    
           **-Wvla-larger-than=**_byte-size_
               If this option is used, the compiler will warn for
               declarations of variable-length arrays whose size is either
               unbounded, or bounded by an argument that allows the array
               size to exceed _byte-size_ bytes.  This is similar to how
               **-Walloca-larger-than=**_byte-size_ works, but with variable-length
               arrays.
    
               Note that GCC may optimize small variable-length arrays of a
               known value into plain arrays, so this warning may not get
               triggered for such arrays.
    
               **-Wvla-larger-than=PTRDIFF_MAX** is enabled by default but is
               typically only effective when **-ftree-vrp** is active (default
               for **-O2** and above).
    
               See also **-Walloca-larger-than=**_byte-size_.
    
           **-Wno-vla-larger-than**
               Disable **-Wvla-larger-than=** warnings.  The option is equivalent
               to **-Wvla-larger-than=SIZE_MAX** or larger.
    
           **-Wvolatile-register-var**
               Warn if a register variable is declared volatile.  The
               volatile modifier does not inhibit all optimizations that may
               eliminate reads and/or writes to register variables.  This
               warning is enabled by **-Wall**.
    
           **-Wdisabled-optimization**
               Warn if a requested optimization pass is disabled.  This
               warning does not generally indicate that there is anything
               wrong with your code; it merely indicates that GCC's
               optimizers are unable to handle the code effectively.  Often,
               the problem is that your code is too big or too complex; GCC
               refuses to optimize programs when the optimization itself is
               likely to take inordinate amounts of time.
    
           **-Wpointer-sign**(C and Objective-C only)
               Warn for pointer argument passing or assignment with different
               signedness.  This option is only supported for C and
               Objective-C.  It is implied by **-Wall** and by **-Wpedantic** , which
               can be disabled with **-Wno-pointer-sign**.
    
           **-Wstack-protector**
               This option is only active when **-fstack-protector** is active.
               It warns about functions that are not protected against stack
               smashing.
    
           **-Woverlength-strings**
               Warn about string constants that are longer than the "minimum
               maximum" length specified in the C standard.  Modern compilers
               generally allow string constants that are much longer than the
               standard's minimum limit, but very portable programs should
               avoid using longer strings.
    
               The limit applies _after_ string constant concatenation, and
               does not count the trailing NUL.  In C90, the limit was 509
               characters; in C99, it was raised to 4095.  C++98 does not
               specify a normative minimum maximum, so we do not diagnose
               overlength strings in C++.
    
               This option is implied by **-Wpedantic** , and can be disabled with
               **-Wno-overlength-strings**.
    
           **-Wunsuffixed-float-constants**(C and Objective-C only)
               Issue a warning for any floating constant that does not have a
               suffix.  When used together with **-Wsystem-headers** it warns
               about such constants in system header files.  This can be
               useful when preparing code to use with the
               "FLOAT_CONST_DECIMAL64" pragma from the decimal floating-point
               extension to C99.
    
           **-Wno-designated-init**(C and Objective-C only)
               Suppress warnings when a positional initializer is used to
               initialize a structure that has been marked with the
               "designated_init" attribute.
    
           **-Whsa**
               Issue a warning when HSAIL cannot be emitted for the compiled
               function or OpenMP construct.
    
       **Options for Debugging Your Program**
           To tell GCC to emit extra information for use by a debugger, in
           almost all cases you need only to add **-g** to your other options.
    
           GCC allows you to use **-g** with **-O**.  The shortcuts taken by
           optimized code may occasionally be surprising: some variables you
           declared may not exist at all; flow of control may briefly move
           where you did not expect it; some statements may not be executed
           because they compute constant results or their values are already
           at hand; some statements may execute in different places because
           they have been moved out of loops.  Nevertheless it is possible to
           debug optimized output.  This makes it reasonable to use the
           optimizer for programs that might have bugs.
    
           If you are not using some other optimization option, consider
           using **-Og** with **-g**.  With no **-O** option at all, some compiler passes
           that collect information useful for debugging do not run at all,
           so that **-Og** may result in a better debugging experience.
    
           **-g** Produce debugging information in the operating system's native
               format (stabs, COFF, XCOFF, or DWARF).  GDB can work with this
               debugging information.
    
               On most systems that use stabs format, **-g** enables use of extra
               debugging information that only GDB can use; this extra
               information makes debugging work better in GDB but probably
               makes other debuggers crash or refuse to read the program.  If
               you want to control for certain whether to generate the extra
               information, use **-gstabs+** , **-gstabs** , **-gxcoff+** , **-gxcoff** , or
               **-gvms**(see below).
    
           **-ggdb**
               Produce debugging information for use by GDB.  This means to
               use the most expressive format available (DWARF, stabs, or the
               native format if neither of those are supported), including
               GDB extensions if at all possible.
    
           **-gdwarf**
           **-gdwarf-**_version_
               Produce debugging information in DWARF format (if that is
               supported).  The value of _version_ may be either 2, 3, 4 or 5;
               the default version for most targets is 4.  DWARF Version 5 is
               only experimental.
    
               Note that with DWARF Version 2, some ports require and always
               use some non-conflicting DWARF 3 extensions in the unwind
               tables.
    
               Version 4 may require GDB 7.0 and **-fvar-tracking-assignments**
               for maximum benefit.
    
               GCC no longer supports DWARF Version 1, which is substantially
               different than Version 2 and later.  For historical reasons,
               some other DWARF-related options such as **-fno-dwarf2-cfi-asm**)
               retain a reference to DWARF Version 2 in their names, but
               apply to all currently-supported versions of DWARF.
    
           **-gstabs**
               Produce debugging information in stabs format (if that is
               supported), without GDB extensions.  This is the format used
               by DBX on most BSD systems.  On MIPS, Alpha and System V
               Release 4 systems this option produces stabs debugging output
               that is not understood by DBX.  On System V Release 4 systems
               this option requires the GNU assembler.
    
           **-gstabs+**
               Produce debugging information in stabs format (if that is
               supported), using GNU extensions understood only by the GNU
               debugger (GDB).  The use of these extensions is likely to make
               other debuggers crash or refuse to read the program.
    
           **-gxcoff**
               Produce debugging information in XCOFF format (if that is
               supported).  This is the format used by the DBX debugger on
               IBM RS/6000 systems.
    
           **-gxcoff+**
               Produce debugging information in XCOFF format (if that is
               supported), using GNU extensions understood only by the GNU
               debugger (GDB).  The use of these extensions is likely to make
               other debuggers crash or refuse to read the program, and may
               cause assemblers other than the GNU assembler (GAS) to fail
               with an error.
    
           **-gvms**
               Produce debugging information in Alpha/VMS debug format (if
               that is supported).  This is the format used by DEBUG on
               Alpha/VMS systems.
    
           **-g** _level_
           **-ggdb** _level_
           **-gstabs** _level_
           **-gxcoff** _level_
           **-gvms** _level_
               Request debugging information and also use _level_ to specify
               how much information.  The default level is 2.
    
               Level 0 produces no debug information at all.  Thus, **-g0**
               negates **-g**.
    
               Level 1 produces minimal information, enough for making
               backtraces in parts of the program that you don't plan to
               debug.  This includes descriptions of functions and external
               variables, and line number tables, but no information about
               local variables.
    
               Level 3 includes extra information, such as all the macro
               definitions present in the program.  Some debuggers support
               macro expansion when you use **-g3**.
    
               If you use multiple **-g** options, with or without level numbers,
               the last such option is the one that is effective.
    
               **-gdwarf** does not accept a concatenated debug level, to avoid
               confusion with **-gdwarf-**_level_.  Instead use an additional
               **-g** _level_ option to change the debug level for DWARF.
    
           **-feliminate-unused-debug-symbols**
               Produce debugging information in stabs format (if that is
               supported), for only symbols that are actually used.
    
           **-femit-class-debug-always**
               Instead of emitting debugging information for a C++ class in
               only one object file, emit it in all object files using the
               class.  This option should be used only with debuggers that
               are unable to handle the way GCC normally emits debugging
               information for classes because using this option increases
               the size of debugging information by as much as a factor of
               two.
    
           **-fno-merge-debug-strings**
               Direct the linker to not merge together strings in the
               debugging information that are identical in different object
               files.  Merging is not supported by all assemblers or linkers.
               Merging decreases the size of the debug information in the
               output file at the cost of increasing link processing time.
               Merging is enabled by default.
    
           **-fdebug-prefix-map=**_old_**=**_new_
               When compiling files residing in directory _old_ , record
               debugging information describing them as if the files resided
               in directory _new_ instead.  This can be used to replace a
               build-time path with an install-time path in the debug info.
               It can also be used to change an absolute path to a relative
               path by using _._ for _new_.  This can give more reproducible
               builds, which are location independent, but may require an
               extra command to tell GDB where to find the source files. See
               also **-ffile-prefix-map**.
    
           **-fvar-tracking**
               Run variable tracking pass.  It computes where variables are
               stored at each position in code.  Better debugging information
               is then generated (if the debugging information format
               supports this information).
    
               It is enabled by default when compiling with optimization
               (**-Os** , **-O** , **-O2** , ...), debugging information (**-g**) and the debug
               info format supports it.
    
           **-fvar-tracking-assignments**
               Annotate assignments to user variables early in the
               compilation and attempt to carry the annotations over
               throughout the compilation all the way to the end, in an
               attempt to improve debug information while optimizing.  Use of
               **-gdwarf-4** is recommended along with it.
    
               It can be enabled even if var-tracking is disabled, in which
               case annotations are created and maintained, but discarded at
               the end.  By default, this flag is enabled together with
               **-fvar-tracking** , except when selective scheduling is enabled.
    
           **-gsplit-dwarf**
               Separate as much DWARF debugging information as possible into
               a separate output file with the extension _.dwo_.  This option
               allows the build system to avoid linking files with debug
               information.  To be useful, this option requires a debugger
               capable of reading _.dwo_ files.
    
           **-gdescribe-dies**
               Add description attributes to some DWARF DIEs that have no
               name attribute, such as artificial variables, external
               references and call site parameter DIEs.
    
           **-gpubnames**
               Generate DWARF ".debug_pubnames" and ".debug_pubtypes"
               sections.
    
           **-ggnu-pubnames**
               Generate ".debug_pubnames" and ".debug_pubtypes" sections in a
               format suitable for conversion into a GDB index.  This option
               is only useful with a linker that can produce GDB index
               version 7.
    
           **-fdebug-types-section**
               When using DWARF Version 4 or higher, type DIEs can be put
               into their own ".debug_types" section instead of making them
               part of the ".debug_info" section.  It is more efficient to
               put them in a separate comdat section since the linker can
               then remove duplicates.  But not all DWARF consumers support
               ".debug_types" sections yet and on some objects ".debug_types"
               produces larger instead of smaller debugging information.
    
           **-grecord-gcc-switches**
           **-gno-record-gcc-switches**
               This switch causes the command-line options used to invoke the
               compiler that may affect code generation to be appended to the
               DW_AT_producer attribute in DWARF debugging information.  The
               options are concatenated with spaces separating them from each
               other and from the compiler version.  It is enabled by
               default.  See also **-frecord-gcc-switches** for another way of
               storing compiler options into the object file.
    
           **-gstrict-dwarf**
               Disallow using extensions of later DWARF standard version than
               selected with **-gdwarf-**_version_.  On most targets using non-
               conflicting DWARF extensions from later standard versions is
               allowed.
    
           **-gno-strict-dwarf**
               Allow using extensions of later DWARF standard version than
               selected with **-gdwarf-**_version_.
    
           **-gas-loc-support**
               Inform the compiler that the assembler supports ".loc"
               directives.  It may then use them for the assembler to
               generate DWARF2+ line number tables.
    
               This is generally desirable, because assembler-generated line-
               number tables are a lot more compact than those the compiler
               can generate itself.
    
               This option will be enabled by default if, at GCC configure
               time, the assembler was found to support such directives.
    
           **-gno-as-loc-support**
               Force GCC to generate DWARF2+ line number tables internally,
               if DWARF2+ line number tables are to be generated.
    
           **gas-locview-support**
               Inform the compiler that the assembler supports "view"
               assignment and reset assertion checking in ".loc" directives.
    
               This option will be enabled by default if, at GCC configure
               time, the assembler was found to support them.
    
           **gno-as-locview-support**
               Force GCC to assign view numbers internally, if
               **-gvariable-location-views** are explicitly requested.
    
           **-gcolumn-info**
           **-gno-column-info**
               Emit location column information into DWARF debugging
               information, rather than just file and line.  This option is
               enabled by default.
    
           **-gstatement-frontiers**
           **-gno-statement-frontiers**
               This option causes GCC to create markers in the internal
               representation at the beginning of statements, and to keep
               them roughly in place throughout compilation, using them to
               guide the output of "is_stmt" markers in the line number
               table.  This is enabled by default when compiling with
               optimization (**-Os** , **-O** , **-O2** , ...), and outputting DWARF 2 debug
               information at the normal level.
    
           **-gvariable-location-views**
           **-gvariable-location-views=incompat5**
           **-gno-variable-location-views**
               Augment variable location lists with progressive view numbers
               implied from the line number table.  This enables debug
               information consumers to inspect state at certain points of
               the program, even if no instructions associated with the
               corresponding source locations are present at that point.  If
               the assembler lacks support for view numbers in line number
               tables, this will cause the compiler to emit the line number
               table, which generally makes them somewhat less compact.  The
               augmented line number tables and location lists are fully
               backward-compatible, so they can be consumed by debug
               information consumers that are not aware of these
               augmentations, but they won't derive any benefit from them
               either.
    
               This is enabled by default when outputting DWARF 2 debug
               information at the normal level, as long as there is assembler
               support, **-fvar-tracking-assignments** is enabled and
               **-gstrict-dwarf** is not.  When assembler support is not
               available, this may still be enabled, but it will force GCC to
               output internal line number tables, and if
               **-ginternal-reset-location-views** is not enabled, that will most
               certainly lead to silently mismatching location views.
    
               There is a proposed representation for view numbers that is
               not backward compatible with the location list format
               introduced in DWARF 5, that can be enabled with
               **-gvariable-location-views=incompat5**.  This option may be
               removed in the future, is only provided as a reference
               implementation of the proposed representation.  Debug
               information consumers are not expected to support this
               extended format, and they would be rendered unable to decode
               location lists using it.
    
           **-ginternal-reset-location-views**
           **-gno-internal-reset-location-views**
               Attempt to determine location views that can be omitted from
               location view lists.  This requires the compiler to have very
               accurate insn length estimates, which isn't always the case,
               and it may cause incorrect view lists to be generated silently
               when using an assembler that does not support location view
               lists.  The GNU assembler will flag any such error as a "view
               number mismatch".  This is only enabled on ports that define a
               reliable estimation function.
    
           **-ginline-points**
           **-gno-inline-points**
               Generate extended debug information for inlined functions.
               Location view tracking markers are inserted at inlined entry
               points, so that address and view numbers can be computed and
               output in debug information.  This can be enabled
               independently of location views, in which case the view
               numbers won't be output, but it can only be enabled along with
               statement frontiers, and it is only enabled by default if
               location views are enabled.
    
           **-gz**[**=**_type_]
               Produce compressed debug sections in DWARF format, if that is
               supported.  If _type_ is not given, the default type depends on
               the capabilities of the assembler and linker used.  _type_ may
               be one of **none**(don't compress debug sections), **zlib**(use zlib
               compression in ELF gABI format), or **zlib-gnu**(use zlib
               compression in traditional GNU format).  If the linker doesn't
               support writing compressed debug sections, the option is
               rejected.  Otherwise, if the assembler does not support them,
               **-gz** is silently ignored when producing object files.
    
           **-femit-struct-debug-baseonly**
               Emit debug information for struct-like types only when the
               base name of the compilation source file matches the base name
               of file in which the struct is defined.
    
               This option substantially reduces the size of debugging
               information, but at significant potential loss in type
               information to the debugger.  See **-femit-struct-debug-reduced**
               for a less aggressive option.  See
               **-femit-struct-debug-detailed** for more detailed control.
    
               This option works only with DWARF debug output.
    
           **-femit-struct-debug-reduced**
               Emit debug information for struct-like types only when the
               base name of the compilation source file matches the base name
               of file in which the type is defined, unless the struct is a
               template or defined in a system header.
    
               This option significantly reduces the size of debugging
               information, with some potential loss in type information to
               the debugger.  See **-femit-struct-debug-baseonly** for a more
               aggressive option.  See **-femit-struct-debug-detailed** for more
               detailed control.
    
               This option works only with DWARF debug output.
    
           **-femit-struct-debug-detailed**[**=**_spec-list_]
               Specify the struct-like types for which the compiler generates
               debug information.  The intent is to reduce duplicate struct
               debug information between different object files within the
               same program.
    
               This option is a detailed version of
               **-femit-struct-debug-reduced** and **-femit-struct-debug-baseonly** ,
               which serves for most needs.
    
               A specification has the
               syntax[**dir:** |**ind:**][**ord:** |**gen:**](**any** |**sys** |**base** |**none**)
    
               The optional first word limits the specification to structs
               that are used directly (**dir:**) or used indirectly (**ind:**).  A
               struct type is used directly when it is the type of a
               variable, member.  Indirect uses arise through pointers to
               structs.  That is, when use of an incomplete struct is valid,
               the use is indirect.  An example is **struct one direct; struct**
               **two * indirect;**.
    
               The optional second word limits the specification to ordinary
               structs (**ord:**) or generic structs (**gen:**).  Generic structs are
               a bit complicated to explain.  For C++, these are non-explicit
               specializations of template classes, or non-template classes
               within the above.  Other programming languages have generics,
               but **-femit-struct-debug-detailed** does not yet implement them.
    
               The third word specifies the source files for those structs
               for which the compiler should emit debug information.  The
               values **none** and **any** have the normal meaning.  The value **base**
               means that the base of name of the file in which the type
               declaration appears must match the base of the name of the
               main compilation file.  In practice, this means that when
               compiling _foo.c_ , debug information is generated for types
               declared in that file and _foo.h_ , but not other header files.
               The value **sys** means those types satisfying **base** or declared in
               system or compiler headers.
    
               You may need to experiment to determine the best settings for
               your application.
    
               The default is **-femit-struct-debug-detailed=all**.
    
               This option works only with DWARF debug output.
    
           **-fno-dwarf2-cfi-asm**
               Emit DWARF unwind info as compiler generated ".eh_frame"
               section instead of using GAS ".cfi_*" directives.
    
           **-fno-eliminate-unused-debug-types**
               Normally, when producing DWARF output, GCC avoids producing
               debug symbol output for types that are nowhere used in the
               source file being compiled.  Sometimes it is useful to have
               GCC emit debugging information for all types declared in a
               compilation unit, regardless of whether or not they are
               actually used in that compilation unit, for example if, in the
               debugger, you want to cast a value to a type that is not
               actually used in your program (but is declared).  More often,
               however, this results in a significant amount of wasted space.
    
       **Options That Control Optimization**
           These options control various sorts of optimizations.
    
           Without any optimization option, the compiler's goal is to reduce
           the cost of compilation and to make debugging produce the expected
           results.  Statements are independent: if you stop the program with
           a breakpoint between statements, you can then assign a new value
           to any variable or change the program counter to any other
           statement in the function and get exactly the results you expect
           from the source code.
    
           Turning on optimization flags makes the compiler attempt to
           improve the performance and/or code size at the expense of
           compilation time and possibly the ability to debug the program.
    
           The compiler performs optimization based on the knowledge it has
           of the program.  Compiling multiple files at once to a single
           output file mode allows the compiler to use information gained
           from all of the files when compiling each of them.
    
           Not all optimizations are controlled directly by a flag.  Only
           optimizations that have a flag are listed in this section.
    
           Most optimizations are completely disabled at **-O0** or if an **-O**
           level is not set on the command line, even if individual
           optimization flags are specified.  Similarly, **-Og** suppresses many
           optimization passes.
    
           Depending on the target and how GCC was configured, a slightly
           different set of optimizations may be enabled at each **-O** level
           than those listed here.  You can invoke GCC with **-Q**
           **--help=optimizers** to find out the exact set of optimizations that
           are enabled at each level.
    
           **-O**
           **-O1** Optimize.  Optimizing compilation takes somewhat more time,
               and a lot more memory for a large function.
    
               With **-O** , the compiler tries to reduce code size and execution
               time, without performing any optimizations that take a great
               deal of compilation time.
    
               **-O** turns on the following optimization flags:
    
               **-fauto-inc-dec -fbranch-count-reg -fcombine-stack-adjustments**
               **-fcompare-elim -fcprop-registers -fdce -fdefer-pop**
               **-fdelayed-branch -fdse -fforward-propagate**
               **-fguess-branch-probability -fif-conversion -fif-conversion2**
               **-finline-functions-called-once -fipa-profile -fipa-pure-const**
               **-fipa-reference -fipa-reference-addressable -fmerge-constants**
               **-fmove-loop-invariants -fomit-frame-pointer -freorder-blocks**
               **-fshrink-wrap -fshrink-wrap-separate -fsplit-wide-types**
               **-fssa-backprop -fssa-phiopt -ftree-bit-ccp -ftree-ccp**
               **-ftree-ch -ftree-coalesce-vars -ftree-copy-prop -ftree-dce**
               **-ftree-dominator-opts -ftree-dse -ftree-forwprop -ftree-fre**
               **-ftree-phiprop -ftree-pta -ftree-scev-cprop -ftree-sink**
               **-ftree-slsr -ftree-sra -ftree-ter -funit-at-a-time**
    
           **-O2** Optimize even more.  GCC performs nearly all supported
               optimizations that do not involve a space-speed tradeoff.  As
               compared to **-O** , this option increases both compilation time
               and the performance of the generated code.
    
               **-O2** turns on all optimization flags specified by **-O**.  It also
               turns on the following optimization flags:
    
               **-falign-functions  -falign-jumps -falign-labels  -falign-loops**
               **-fcaller-saves -fcode-hoisting -fcrossjumping**
               **-fcse-follow-jumps  -fcse-skip-blocks**
               **-fdelete-null-pointer-checks -fdevirtualize**
               **-fdevirtualize-speculatively -fexpensive-optimizations -fgcse**
               **-fgcse-lm -fhoist-adjacent-loads -finline-small-functions**
               **-findirect-inlining -fipa-bit-cp  -fipa-cp  -fipa-icf -fipa-ra**
               **-fipa-sra  -fipa-vrp -fisolate-erroneous-paths-dereference**
               **-flra-remat -foptimize-sibling-calls -foptimize-strlen**
               **-fpartial-inlining -fpeephole2 -freorder-blocks-algorithm=stc**
               **-freorder-blocks-and-partition  -freorder-functions**
               **-frerun-cse-after-loop -fschedule-insns  -fschedule-insns2**
               **-fsched-interblock  -fsched-spec -fstore-merging**
               **-fstrict-aliasing -fthread-jumps -ftree-builtin-call-dce**
               **-ftree-pre -ftree-switch-conversion  -ftree-tail-merge**
               **-ftree-vrp**
    
               Please note the warning under **-fgcse** about invoking **-O2** on
               programs that use computed gotos.
    
           **-O3** Optimize yet more.  **-O3** turns on all optimizations specified
               by **-O2** and also turns on the following optimization flags:
    
               **-fgcse-after-reload -finline-functions -fipa-cp-clone**
               **-floop-interchange -floop-unroll-and-jam -fpeel-loops**
               **-fpredictive-commoning -fsplit-paths**
               **-ftree-loop-distribute-patterns -ftree-loop-distribution**
               **-ftree-loop-vectorize -ftree-partial-pre -ftree-slp-vectorize**
               **-funswitch-loops -fvect-cost-model -fversion-loops-for-strides**
    
           **-O0** Reduce compilation time and make debugging produce the
               expected results.  This is the default.
    
           **-Os** Optimize for size.  **-Os** enables all **-O2** optimizations except
               those that often increase code size:
    
               **-falign-functions  -falign-jumps -falign-labels  -falign-loops**
               **-fprefetch-loop-arrays  -freorder-blocks-algorithm=stc**
    
               It also enables **-finline-functions** , causes the compiler to
               tune for code size rather than execution speed, and performs
               further optimizations designed to reduce code size.
    
           **-Ofast**
               Disregard strict standards compliance.  **-Ofast** enables all **-O3**
               optimizations.  It also enables optimizations that are not
               valid for all standard-compliant programs.  It turns on
               **-ffast-math** and the Fortran-specific **-fstack-arrays** , unless
               **-fmax-stack-var-size** is specified, and **-fno-protect-parens**.
    
           **-Og** Optimize debugging experience.  **-Og** should be the optimization
               level of choice for the standard edit-compile-debug cycle,
               offering a reasonable level of optimization while maintaining
               fast compilation and a good debugging experience.  It is a
               better choice than **-O0** for producing debuggable code because
               some compiler passes that collect debug information are
               disabled at **-O0**.
    
               Like **-O0** , **-Og** completely disables a number of optimization
               passes so that individual options controlling them have no
               effect.  Otherwise **-Og** enables all **-O1** optimization flags
               except for those that may interfere with debugging:
    
               **-fbranch-count-reg  -fdelayed-branch -fif-conversion**
               **-fif-conversion2 -finline-functions-called-once**
               **-fmove-loop-invariants  -fssa-phiopt -ftree-bit-ccp**
               **-ftree-pta  -ftree-sra**
    
           If you use multiple **-O** options, with or without level numbers, the
           last such option is the one that is effective.
    
           Options of the form **-f** _flag_ specify machine-independent flags.
           Most flags have both positive and negative forms; the negative
           form of **-ffoo** is **-fno-foo**.  In the table below, only one of the
           forms is listed---the one you typically use.  You can figure out
           the other form by either removing **no-** or adding it.
    
           The following options control specific optimizations.  They are
           either activated by **-O** options or are related to ones that are.
           You can use the following flags in the rare cases when "fine-
           tuning" of optimizations to be performed is desired.
    
           **-fno-defer-pop**
               For machines that must pop arguments after a function call,
               always pop the arguments as soon as each function returns.  At
               levels **-O1** and higher, **-fdefer-pop** is the default; this allows
               the compiler to let arguments accumulate on the stack for
               several function calls and pop them all at once.
    
           **-fforward-propagate**
               Perform a forward propagation pass on RTL.  The pass tries to
               combine two instructions and checks if the result can be
               simplified.  If loop unrolling is active, two passes are
               performed and the second is scheduled after loop unrolling.
    
               This option is enabled by default at optimization levels **-O** ,
               **-O2** , **-O3** , **-Os**.
    
           **-ffp-contract=**_style_
               **-ffp-contract=off** disables floating-point expression
               contraction.  **-ffp-contract=fast** enables floating-point
               expression contraction such as forming of fused multiply-add
               operations if the target has native support for them.
               **-ffp-contract=on** enables floating-point expression contraction
               if allowed by the language standard.  This is currently not
               implemented and treated equal to **-ffp-contract=off**.
    
               The default is **-ffp-contract=fast**.
    
           **-fomit-frame-pointer**
               Omit the frame pointer in functions that don't need one.  This
               avoids the instructions to save, set up and restore the frame
               pointer; on many targets it also makes an extra register
               available.
    
               On some targets this flag has no effect because the standard
               calling sequence always uses a frame pointer, so it cannot be
               omitted.
    
               Note that **-fno-omit-frame-pointer** doesn't guarantee the frame
               pointer is used in all functions.  Several targets always omit
               the frame pointer in leaf functions.
    
               Enabled by default at **-O** and higher.
    
           **-foptimize-sibling-calls**
               Optimize sibling and tail recursive calls.
    
               Enabled at levels **-O2** , **-O3** , **-Os**.
    
           **-foptimize-strlen**
               Optimize various standard C string functions (e.g. "strlen",
               "strchr" or "strcpy") and their "_FORTIFY_SOURCE" counterparts
               into faster alternatives.
    
               Enabled at levels **-O2** , **-O3**.
    
           **-fno-inline**
               Do not expand any functions inline apart from those marked
               with the "always_inline" attribute.  This is the default when
               not optimizing.
    
               Single functions can be exempted from inlining by marking them
               with the "noinline" attribute.
    
           **-finline-small-functions**
               Integrate functions into their callers when their body is
               smaller than expected function call code (so overall size of
               program gets smaller).  The compiler heuristically decides
               which functions are simple enough to be worth integrating in
               this way.  This inlining applies to all functions, even those
               not declared inline.
    
               Enabled at levels **-O2** , **-O3** , **-Os**.
    
           **-findirect-inlining**
               Inline also indirect calls that are discovered to be known at
               compile time thanks to previous inlining.  This option has any
               effect only when inlining itself is turned on by the
               **-finline-functions** or **-finline-small-functions** options.
    
               Enabled at levels **-O2** , **-O3** , **-Os**.
    
           **-finline-functions**
               Consider all functions for inlining, even if they are not
               declared inline.  The compiler heuristically decides which
               functions are worth integrating in this way.
    
               If all calls to a given function are integrated, and the
               function is declared "static", then the function is normally
               not output as assembler code in its own right.
    
               Enabled at levels **-O3** , **-Os**.  Also enabled by **-fprofile-use** and
               **-fauto-profile**.
    
           **-finline-functions-called-once**
               Consider all "static" functions called once for inlining into
               their caller even if they are not marked "inline".  If a call
               to a given function is integrated, then the function is not
               output as assembler code in its own right.
    
               Enabled at levels **-O1** , **-O2** , **-O3** and **-Os** , but not **-Og**.
    
           **-fearly-inlining**
               Inline functions marked by "always_inline" and functions whose
               body seems smaller than the function call overhead early
               before doing **-fprofile-generate** instrumentation and real
               inlining pass.  Doing so makes profiling significantly cheaper
               and usually inlining faster on programs having large chains of
               nested wrapper functions.
    
               Enabled by default.
    
           **-fipa-sra**
               Perform interprocedural scalar replacement of aggregates,
               removal of unused parameters and replacement of parameters
               passed by reference by parameters passed by value.
    
               Enabled at levels **-O2** , **-O3** and **-Os**.
    
           **-finline-limit=**_n_
               By default, GCC limits the size of functions that can be
               inlined.  This flag allows coarse control of this limit.  _n_ is
               the size of functions that can be inlined in number of pseudo
               instructions.
    
               Inlining is actually controlled by a number of parameters,
               which may be specified individually by using **--param**
               _name_**=**_value_.  The **-finline-limit=**_n_ option sets some of these
               parameters as follows:
    
               **max-inline-insns-single**
                   is set to _n_ /2.
    
               **max-inline-insns-auto**
                   is set to _n_ /2.
    
               See below for a documentation of the individual parameters
               controlling inlining and for the defaults of these parameters.
    
               _Note:_ there may be no value to **-finline-limit** that results in
               default behavior.
    
               _Note:_ pseudo instruction represents, in this particular
               context, an abstract measurement of function's size.  In no
               way does it represent a count of assembly instructions and as
               such its exact meaning might change from one release to an
               another.
    
           **-fno-keep-inline-dllexport**
               This is a more fine-grained version of
               **-fkeep-inline-functions** , which applies only to functions that
               are declared using the "dllexport" attribute or declspec.
    
           **-fkeep-inline-functions**
               In C, emit "static" functions that are declared "inline" into
               the object file, even if the function has been inlined into
               all of its callers.  This switch does not affect functions
               using the "extern inline" extension in GNU C90.  In C++, emit
               any and all inline functions into the object file.
    
           **-fkeep-static-functions**
               Emit "static" functions into the object file, even if the
               function is never used.
    
           **-fkeep-static-consts**
               Emit variables declared "static const" when optimization isn't
               turned on, even if the variables aren't referenced.
    
               GCC enables this option by default.  If you want to force the
               compiler to check if a variable is referenced, regardless of
               whether or not optimization is turned on, use the
               **-fno-keep-static-consts** option.
    
           **-fmerge-constants**
               Attempt to merge identical constants (string constants and
               floating-point constants) across compilation units.
    
               This option is the default for optimized compilation if the
               assembler and linker support it.  Use **-fno-merge-constants** to
               inhibit this behavior.
    
               Enabled at levels **-O** , **-O2** , **-O3** , **-Os**.
    
           **-fmerge-all-constants**
               Attempt to merge identical constants and identical variables.
    
               This option implies **-fmerge-constants**.  In addition to
               **-fmerge-constants** this considers e.g. even constant
               initialized arrays or initialized constant variables with
               integral or floating-point types.  Languages like C or C++
               require each variable, including multiple instances of the
               same variable in recursive calls, to have distinct locations,
               so using this option results in non-conforming behavior.
    
           **-fmodulo-sched**
               Perform swing modulo scheduling immediately before the first
               scheduling pass.  This pass looks at innermost loops and
               reorders their instructions by overlapping different
               iterations.
    
           **-fmodulo-sched-allow-regmoves**
               Perform more aggressive SMS-based modulo scheduling with
               register moves allowed.  By setting this flag certain anti-
               dependences edges are deleted, which triggers the generation
               of reg-moves based on the life-range analysis.  This option is
               effective only with **-fmodulo-sched** enabled.
    
           **-fno-branch-count-reg**
               Disable the optimization pass that scans for opportunities to
               use "decrement and branch" instructions on a count register
               instead of instruction sequences that decrement a register,
               compare it against zero, and then branch based upon the
               result.  This option is only meaningful on architectures that
               support such instructions, which include x86, PowerPC, IA-64
               and S/390.  Note that the **-fno-branch-count-reg** option doesn't
               remove the decrement and branch instructions from the
               generated instruction stream introduced by other optimization
               passes.
    
               The default is **-fbranch-count-reg** at **-O1** and higher, except
               for **-Og**.
    
           **-fno-function-cse**
               Do not put function addresses in registers; make each
               instruction that calls a constant function contain the
               function's address explicitly.
    
               This option results in less efficient code, but some strange
               hacks that alter the assembler output may be confused by the
               optimizations performed when this option is not used.
    
               The default is **-ffunction-cse**
    
           **-fno-zero-initialized-in-bss**
               If the target supports a BSS section, GCC by default puts
               variables that are initialized to zero into BSS.  This can
               save space in the resulting code.
    
               This option turns off this behavior because some programs
               explicitly rely on variables going to the data section---e.g.,
               so that the resulting executable can find the beginning of
               that section and/or make assumptions based on that.
    
               The default is **-fzero-initialized-in-bss**.
    
           **-fthread-jumps**
               Perform optimizations that check to see if a jump branches to
               a location where another comparison subsumed by the first is
               found.  If so, the first branch is redirected to either the
               destination of the second branch or a point immediately
               following it, depending on whether the condition is known to
               be true or false.
    
               Enabled at levels **-O2** , **-O3** , **-Os**.
    
           **-fsplit-wide-types**
               When using a type that occupies multiple registers, such as
               "long long" on a 32-bit system, split the registers apart and
               allocate them independently.  This normally generates better
               code for those types, but may make debugging more difficult.
    
               Enabled at levels **-O** , **-O2** , **-O3** , **-Os**.
    
           **-fcse-follow-jumps**
               In common subexpression elimination (CSE), scan through jump
               instructions when the target of the jump is not reached by any
               other path.  For example, when CSE encounters an "if"
               statement with an "else" clause, CSE follows the jump when the
               condition tested is false.
    
               Enabled at levels **-O2** , **-O3** , **-Os**.
    
           **-fcse-skip-blocks**
               This is similar to **-fcse-follow-jumps** , but causes CSE to
               follow jumps that conditionally skip over blocks.  When CSE
               encounters a simple "if" statement with no else clause,
               **-fcse-skip-blocks** causes CSE to follow the jump around the
               body of the "if".
    
               Enabled at levels **-O2** , **-O3** , **-Os**.
    
           **-frerun-cse-after-loop**
               Re-run common subexpression elimination after loop
               optimizations are performed.
    
               Enabled at levels **-O2** , **-O3** , **-Os**.
    
           **-fgcse**
               Perform a global common subexpression elimination pass.  This
               pass also performs global constant and copy propagation.
    
               _Note:_ When compiling a program using computed gotos, a GCC
               extension, you may get better run-time performance if you
               disable the global common subexpression elimination pass by
               adding **-fno-gcse** to the command line.
    
               Enabled at levels **-O2** , **-O3** , **-Os**.
    
           **-fgcse-lm**
               When **-fgcse-lm** is enabled, global common subexpression
               elimination attempts to move loads that are only killed by
               stores into themselves.  This allows a loop containing a
               load/store sequence to be changed to a load outside the loop,
               and a copy/store within the loop.
    
               Enabled by default when **-fgcse** is enabled.
    
           **-fgcse-sm**
               When **-fgcse-sm** is enabled, a store motion pass is run after
               global common subexpression elimination.  This pass attempts
               to move stores out of loops.  When used in conjunction with
               **-fgcse-lm** , loops containing a load/store sequence can be
               changed to a load before the loop and a store after the loop.
    
               Not enabled at any optimization level.
    
           **-fgcse-las**
               When **-fgcse-las** is enabled, the global common subexpression
               elimination pass eliminates redundant loads that come after
               stores to the same memory location (both partial and full
               redundancies).
    
               Not enabled at any optimization level.
    
           **-fgcse-after-reload**
               When **-fgcse-after-reload** is enabled, a redundant load
               elimination pass is performed after reload.  The purpose of
               this pass is to clean up redundant spilling.
    
               Enabled by **-fprofile-use** and **-fauto-profile**.
    
           **-faggressive-loop-optimizations**
               This option tells the loop optimizer to use language
               constraints to derive bounds for the number of iterations of a
               loop.  This assumes that loop code does not invoke undefined
               behavior by for example causing signed integer overflows or
               out-of-bound array accesses.  The bounds for the number of
               iterations of a loop are used to guide loop unrolling and
               peeling and loop exit test optimizations.  This option is
               enabled by default.
    
           **-funconstrained-commons**
               This option tells the compiler that variables declared in
               common blocks (e.g. Fortran) may later be overridden with
               longer trailing arrays. This prevents certain optimizations
               that depend on knowing the array bounds.
    
           **-fcrossjumping**
               Perform cross-jumping transformation.  This transformation
               unifies equivalent code and saves code size.  The resulting
               code may or may not perform better than without cross-jumping.
    
               Enabled at levels **-O2** , **-O3** , **-Os**.
    
           **-fauto-inc-dec**
               Combine increments or decrements of addresses with memory
               accesses.  This pass is always skipped on architectures that
               do not have instructions to support this.  Enabled by default
               at **-O** and higher on architectures that support this.
    
           **-fdce**
               Perform dead code elimination (DCE) on RTL.  Enabled by
               default at **-O** and higher.
    
           **-fdse**
               Perform dead store elimination (DSE) on RTL.  Enabled by
               default at **-O** and higher.
    
           **-fif-conversion**
               Attempt to transform conditional jumps into branch-less
               equivalents.  This includes use of conditional moves, min,
               max, set flags and abs instructions, and some tricks doable by
               standard arithmetics.  The use of conditional execution on
               chips where it is available is controlled by **-fif-conversion2**.
    
               Enabled at levels **-O** , **-O2** , **-O3** , **-Os** , but not with **-Og**.
    
           **-fif-conversion2**
               Use conditional execution (where available) to transform
               conditional jumps into branch-less equivalents.
    
               Enabled at levels **-O** , **-O2** , **-O3** , **-Os** , but not with **-Og**.
    
           **-fdeclone-ctor-dtor**
               The C++ ABI requires multiple entry points for constructors
               and destructors: one for a base subobject, one for a complete
               object, and one for a virtual destructor that calls operator
               delete afterwards.  For a hierarchy with virtual bases, the
               base and complete variants are clones, which means two copies
               of the function.  With this option, the base and complete
               variants are changed to be thunks that call a common
               implementation.
    
               Enabled by **-Os**.
    
           **-fdelete-null-pointer-checks**
               Assume that programs cannot safely dereference null pointers,
               and that no code or data element resides at address zero.
               This option enables simple constant folding optimizations at
               all optimization levels.  In addition, other optimization
               passes in GCC use this flag to control global dataflow
               analyses that eliminate useless checks for null pointers;
               these assume that a memory access to address zero always
               results in a trap, so that if a pointer is checked after it
               has already been dereferenced, it cannot be null.
    
               Note however that in some environments this assumption is not
               true.  Use **-fno-delete-null-pointer-checks** to disable this
               optimization for programs that depend on that behavior.
    
               This option is enabled by default on most targets.  On Nios II
               ELF, it defaults to off.  On AVR, CR16, and MSP430, this
               option is completely disabled.
    
               Passes that use the dataflow information are enabled
               independently at different optimization levels.
    
           **-fdevirtualize**
               Attempt to convert calls to virtual functions to direct calls.
               This is done both within a procedure and interprocedurally as
               part of indirect inlining (**-findirect-inlining**) and
               interprocedural constant propagation (**-fipa-cp**).  Enabled at
               levels **-O2** , **-O3** , **-Os**.
    
           **-fdevirtualize-speculatively**
               Attempt to convert calls to virtual functions to speculative
               direct calls.  Based on the analysis of the type inheritance
               graph, determine for a given call the set of likely targets.
               If the set is small, preferably of size 1, change the call
               into a conditional deciding between direct and indirect calls.
               The speculative calls enable more optimizations, such as
               inlining.  When they seem useless after further optimization,
               they are converted back into original form.
    
           **-fdevirtualize-at-ltrans**
               Stream extra information needed for aggressive
               devirtualization when running the link-time optimizer in local
               transformation mode.  This option enables more
               devirtualization but significantly increases the size of
               streamed data. For this reason it is disabled by default.
    
           **-fexpensive-optimizations**
               Perform a number of minor optimizations that are relatively
               expensive.
    
               Enabled at levels **-O2** , **-O3** , **-Os**.
    
           **-free**
               Attempt to remove redundant extension instructions.  This is
               especially helpful for the x86-64 architecture, which
               implicitly zero-extends in 64-bit registers after writing to
               their lower 32-bit half.
    
               Enabled for Alpha, AArch64 and x86 at levels **-O2** , **-O3** , **-Os**.
    
           **-fno-lifetime-dse**
               In C++ the value of an object is only affected by changes
               within its lifetime: when the constructor begins, the object
               has an indeterminate value, and any changes during the
               lifetime of the object are dead when the object is destroyed.
               Normally dead store elimination will take advantage of this;
               if your code relies on the value of the object storage
               persisting beyond the lifetime of the object, you can use this
               flag to disable this optimization.  To preserve stores before
               the constructor starts (e.g. because your operator new clears
               the object storage) but still treat the object as dead after
               the destructor you, can use **-flifetime-dse=1**.  The default
               behavior can be explicitly selected with **-flifetime-dse=2**.
               **-flifetime-dse=0** is equivalent to **-fno-lifetime-dse**.
    
           **-flive-range-shrinkage**
               Attempt to decrease register pressure through register live
               range shrinkage.  This is helpful for fast processors with
               small or moderate size register sets.
    
           **-fira-algorithm=**_algorithm_
               Use the specified coloring algorithm for the integrated
               register allocator.  The _algorithm_ argument can be **priority** ,
               which specifies Chow's priority coloring, or **CB** , which
               specifies Chaitin-Briggs coloring.  Chaitin-Briggs coloring is
               not implemented for all architectures, but for those targets
               that do support it, it is the default because it generates
               better code.
    
           **-fira-region=**_region_
               Use specified regions for the integrated register allocator.
               The _region_ argument should be one of the following:
    
               **all** Use all loops as register allocation regions.  This can
                   give the best results for machines with a small and/or
                   irregular register set.
    
               **mixed**
                   Use all loops except for loops with small register
                   pressure as the regions.  This value usually gives the
                   best results in most cases and for most architectures, and
                   is enabled by default when compiling with optimization for
                   speed (**-O** , **-O2** , ...).
    
               **one** Use all functions as a single region.  This typically
                   results in the smallest code size, and is enabled by
                   default for **-Os** or **-O0**.
    
           **-fira-hoist-pressure**
               Use IRA to evaluate register pressure in the code hoisting
               pass for decisions to hoist expressions.  This option usually
               results in smaller code, but it can slow the compiler down.
    
               This option is enabled at level **-Os** for all targets.
    
           **-fira-loop-pressure**
               Use IRA to evaluate register pressure in loops for decisions
               to move loop invariants.  This option usually results in
               generation of faster and smaller code on machines with large
               register files (>= 32 registers), but it can slow the compiler
               down.
    
               This option is enabled at level **-O3** for some targets.
    
           **-fno-ira-share-save-slots**
               Disable sharing of stack slots used for saving call-used hard
               registers living through a call.  Each hard register gets a
               separate stack slot, and as a result function stack frames are
               larger.
    
           **-fno-ira-share-spill-slots**
               Disable sharing of stack slots allocated for pseudo-registers.
               Each pseudo-register that does not get a hard register gets a
               separate stack slot, and as a result function stack frames are
               larger.
    
           **-flra-remat**
               Enable CFG-sensitive rematerialization in LRA.  Instead of
               loading values of spilled pseudos, LRA tries to rematerialize
               (recalculate) values if it is profitable.
    
               Enabled at levels **-O2** , **-O3** , **-Os**.
    
           **-fdelayed-branch**
               If supported for the target machine, attempt to reorder
               instructions to exploit instruction slots available after
               delayed branch instructions.
    
               Enabled at levels **-O** , **-O2** , **-O3** , **-Os** , but not at **-Og**.
    
           **-fschedule-insns**
               If supported for the target machine, attempt to reorder
               instructions to eliminate execution stalls due to required
               data being unavailable.  This helps machines that have slow
               floating point or memory load instructions by allowing other
               instructions to be issued until the result of the load or
               floating-point instruction is required.
    
               Enabled at levels **-O2** , **-O3**.
    
           **-fschedule-insns2**
               Similar to **-fschedule-insns** , but requests an additional pass
               of instruction scheduling after register allocation has been
               done.  This is especially useful on machines with a relatively
               small number of registers and where memory load instructions
               take more than one cycle.
    
               Enabled at levels **-O2** , **-O3** , **-Os**.
    
           **-fno-sched-interblock**
               Disable instruction scheduling across basic blocks, which is
               normally enabled when scheduling before register allocation,
               i.e.  with **-fschedule-insns** or at **-O2** or higher.
    
           **-fno-sched-spec**
               Disable speculative motion of non-load instructions, which is
               normally enabled when scheduling before register allocation,
               i.e.  with **-fschedule-insns** or at **-O2** or higher.
    
           **-fsched-pressure**
               Enable register pressure sensitive insn scheduling before
               register allocation.  This only makes sense when scheduling
               before register allocation is enabled, i.e. with
               **-fschedule-insns** or at **-O2** or higher.  Usage of this option
               can improve the generated code and decrease its size by
               preventing register pressure increase above the number of
               available hard registers and subsequent spills in register
               allocation.
    
           **-fsched-spec-load**
               Allow speculative motion of some load instructions.  This only
               makes sense when scheduling before register allocation, i.e.
               with **-fschedule-insns** or at **-O2** or higher.
    
           **-fsched-spec-load-dangerous**
               Allow speculative motion of more load instructions.  This only
               makes sense when scheduling before register allocation, i.e.
               with **-fschedule-insns** or at **-O2** or higher.
    
           **-fsched-stalled-insns**
           **-fsched-stalled-insns=**_n_
               Define how many insns (if any) can be moved prematurely from
               the queue of stalled insns into the ready list during the
               second scheduling pass.  **-fno-sched-stalled-insns** means that
               no insns are moved prematurely, **-fsched-stalled-insns=0** means
               there is no limit on how many queued insns can be moved
               prematurely.  **-fsched-stalled-insns** without a value is
               equivalent to **-fsched-stalled-insns=1**.
    
           **-fsched-stalled-insns-dep**
           **-fsched-stalled-insns-dep=**_n_
               Define how many insn groups (cycles) are examined for a
               dependency on a stalled insn that is a candidate for premature
               removal from the queue of stalled insns.  This has an effect
               only during the second scheduling pass, and only if
               **-fsched-stalled-insns** is used.  **-fno-sched-stalled-insns-dep**
               is equivalent to **-fsched-stalled-insns-dep=0**.
               **-fsched-stalled-insns-dep** without a value is equivalent to
               **-fsched-stalled-insns-dep=1**.
    
           **-fsched2-use-superblocks**
               When scheduling after register allocation, use superblock
               scheduling.  This allows motion across basic block boundaries,
               resulting in faster schedules.  This option is experimental,
               as not all machine descriptions used by GCC model the CPU
               closely enough to avoid unreliable results from the algorithm.
    
               This only makes sense when scheduling after register
               allocation, i.e. with **-fschedule-insns2** or at **-O2** or higher.
    
           **-fsched-group-heuristic**
               Enable the group heuristic in the scheduler.  This heuristic
               favors the instruction that belongs to a schedule group.  This
               is enabled by default when scheduling is enabled, i.e. with
               **-fschedule-insns** or **-fschedule-insns2** or at **-O2** or higher.
    
           **-fsched-critical-path-heuristic**
               Enable the critical-path heuristic in the scheduler.  This
               heuristic favors instructions on the critical path.  This is
               enabled by default when scheduling is enabled, i.e. with
               **-fschedule-insns** or **-fschedule-insns2** or at **-O2** or higher.
    
           **-fsched-spec-insn-heuristic**
               Enable the speculative instruction heuristic in the scheduler.
               This heuristic favors speculative instructions with greater
               dependency weakness.  This is enabled by default when
               scheduling is enabled, i.e.  with **-fschedule-insns** or
               **-fschedule-insns2** or at **-O2** or higher.
    
           **-fsched-rank-heuristic**
               Enable the rank heuristic in the scheduler.  This heuristic
               favors the instruction belonging to a basic block with greater
               size or frequency.  This is enabled by default when scheduling
               is enabled, i.e.  with **-fschedule-insns** or **-fschedule-insns2**
               or at **-O2** or higher.
    
           **-fsched-last-insn-heuristic**
               Enable the last-instruction heuristic in the scheduler.  This
               heuristic favors the instruction that is less dependent on the
               last instruction scheduled.  This is enabled by default when
               scheduling is enabled, i.e. with **-fschedule-insns** or
               **-fschedule-insns2** or at **-O2** or higher.
    
           **-fsched-dep-count-heuristic**
               Enable the dependent-count heuristic in the scheduler.  This
               heuristic favors the instruction that has more instructions
               depending on it.  This is enabled by default when scheduling
               is enabled, i.e.  with **-fschedule-insns** or **-fschedule-insns2**
               or at **-O2** or higher.
    
           **-freschedule-modulo-scheduled-loops**
               Modulo scheduling is performed before traditional scheduling.
               If a loop is modulo scheduled, later scheduling passes may
               change its schedule.  Use this option to control that
               behavior.
    
           **-fselective-scheduling**
               Schedule instructions using selective scheduling algorithm.
               Selective scheduling runs instead of the first scheduler pass.
    
           **-fselective-scheduling2**
               Schedule instructions using selective scheduling algorithm.
               Selective scheduling runs instead of the second scheduler
               pass.
    
           **-fsel-sched-pipelining**
               Enable software pipelining of innermost loops during selective
               scheduling.  This option has no effect unless one of
               **-fselective-scheduling** or **-fselective-scheduling2** is turned
               on.
    
           **-fsel-sched-pipelining-outer-loops**
               When pipelining loops during selective scheduling, also
               pipeline outer loops.  This option has no effect unless
               **-fsel-sched-pipelining** is turned on.
    
           **-fsemantic-interposition**
               Some object formats, like ELF, allow interposing of symbols by
               the dynamic linker.  This means that for symbols exported from
               the DSO, the compiler cannot perform interprocedural
               propagation, inlining and other optimizations in anticipation
               that the function or variable in question may change. While
               this feature is useful, for example, to rewrite memory
               allocation functions by a debugging implementation, it is
               expensive in the terms of code quality.  With
               **-fno-semantic-interposition** the compiler assumes that if
               interposition happens for functions the overwriting function
               will have precisely the same semantics (and side effects).
               Similarly if interposition happens for variables, the
               constructor of the variable will be the same. The flag has no
               effect for functions explicitly declared inline (where it is
               never allowed for interposition to change semantics) and for
               symbols explicitly declared weak.
    
           **-fshrink-wrap**
               Emit function prologues only before parts of the function that
               need it, rather than at the top of the function.  This flag is
               enabled by default at **-O** and higher.
    
           **-fshrink-wrap-separate**
               Shrink-wrap separate parts of the prologue and epilogue
               separately, so that those parts are only executed when needed.
               This option is on by default, but has no effect unless
               **-fshrink-wrap** is also turned on and the target supports this.
    
           **-fcaller-saves**
               Enable allocation of values to registers that are clobbered by
               function calls, by emitting extra instructions to save and
               restore the registers around such calls.  Such allocation is
               done only when it seems to result in better code.
    
               This option is always enabled by default on certain machines,
               usually those which have no call-preserved registers to use
               instead.
    
               Enabled at levels **-O2** , **-O3** , **-Os**.
    
           **-fcombine-stack-adjustments**
               Tracks stack adjustments (pushes and pops) and stack memory
               references and then tries to find ways to combine them.
    
               Enabled by default at **-O1** and higher.
    
           **-fipa-ra**
               Use caller save registers for allocation if those registers
               are not used by any called function.  In that case it is not
               necessary to save and restore them around calls.  This is only
               possible if called functions are part of same compilation unit
               as current function and they are compiled before it.
    
               Enabled at levels **-O2** , **-O3** , **-Os** , however the option is
               disabled if generated code will be instrumented for profiling
               (**-p** , or **-pg**) or if callee's register usage cannot be known
               exactly (this happens on targets that do not expose prologues
               and epilogues in RTL).
    
           **-fconserve-stack**
               Attempt to minimize stack usage.  The compiler attempts to use
               less stack space, even if that makes the program slower.  This
               option implies setting the **large-stack-frame** parameter to 100
               and the **large-stack-frame-growth** parameter to 400.
    
           **-ftree-reassoc**
               Perform reassociation on trees.  This flag is enabled by
               default at **-O** and higher.
    
           **-fcode-hoisting**
               Perform code hoisting.  Code hoisting tries to move the
               evaluation of expressions executed on all paths to the
               function exit as early as possible.  This is especially useful
               as a code size optimization, but it often helps for code speed
               as well.  This flag is enabled by default at **-O2** and higher.
    
           **-ftree-pre**
               Perform partial redundancy elimination (PRE) on trees.  This
               flag is enabled by default at **-O2** and **-O3**.
    
           **-ftree-partial-pre**
               Make partial redundancy elimination (PRE) more aggressive.
               This flag is enabled by default at **-O3**.
    
           **-ftree-forwprop**
               Perform forward propagation on trees.  This flag is enabled by
               default at **-O** and higher.
    
           **-ftree-fre**
               Perform full redundancy elimination (FRE) on trees.  The
               difference between FRE and PRE is that FRE only considers
               expressions that are computed on all paths leading to the
               redundant computation.  This analysis is faster than PRE,
               though it exposes fewer redundancies.  This flag is enabled by
               default at **-O** and higher.
    
           **-ftree-phiprop**
               Perform hoisting of loads from conditional pointers on trees.
               This pass is enabled by default at **-O** and higher.
    
           **-fhoist-adjacent-loads**
               Speculatively hoist loads from both branches of an if-then-
               else if the loads are from adjacent locations in the same
               structure and the target architecture has a conditional move
               instruction.  This flag is enabled by default at **-O2** and
               higher.
    
           **-ftree-copy-prop**
               Perform copy propagation on trees.  This pass eliminates
               unnecessary copy operations.  This flag is enabled by default
               at **-O** and higher.
    
           **-fipa-pure-const**
               Discover which functions are pure or constant.  Enabled by
               default at **-O** and higher.
    
           **-fipa-reference**
               Discover which static variables do not escape the compilation
               unit.  Enabled by default at **-O** and higher.
    
           **-fipa-reference-addressable**
               Discover read-only, write-only and non-addressable static
               variables.  Enabled by default at **-O** and higher.
    
           **-fipa-stack-alignment**
               Reduce stack alignment on call sites if possible.  Enabled by
               default.
    
           **-fipa-pta**
               Perform interprocedural pointer analysis and interprocedural
               modification and reference analysis.  This option can cause
               excessive memory and compile-time usage on large compilation
               units.  It is not enabled by default at any optimization
               level.
    
           **-fipa-profile**
               Perform interprocedural profile propagation.  The functions
               called only from cold functions are marked as cold. Also
               functions executed once (such as "cold", "noreturn", static
               constructors or destructors) are identified. Cold functions
               and loop less parts of functions executed once are then
               optimized for size.  Enabled by default at **-O** and higher.
    
           **-fipa-cp**
               Perform interprocedural constant propagation.  This
               optimization analyzes the program to determine when values
               passed to functions are constants and then optimizes
               accordingly.  This optimization can substantially increase
               performance if the application has constants passed to
               functions.  This flag is enabled by default at **-O2** , **-Os** and
               **-O3**.  It is also enabled by **-fprofile-use** and **-fauto-profile**.
    
           **-fipa-cp-clone**
               Perform function cloning to make interprocedural constant
               propagation stronger.  When enabled, interprocedural constant
               propagation performs function cloning when externally visible
               function can be called with constant arguments.  Because this
               optimization can create multiple copies of functions, it may
               significantly increase code size (see **--param**
               **ipcp-unit-growth=**_value_).  This flag is enabled by default at
               **-O3**.  It is also enabled by **-fprofile-use** and **-fauto-profile**.
    
           **-fipa-bit-cp**
               When enabled, perform interprocedural bitwise constant
               propagation. This flag is enabled by default at **-O2** and by
               **-fprofile-use** and **-fauto-profile**.  It requires that **-fipa-cp**
               is enabled.
    
           **-fipa-vrp**
               When enabled, perform interprocedural propagation of value
               ranges. This flag is enabled by default at **-O2**. It requires
               that **-fipa-cp** is enabled.
    
           **-fipa-icf**
               Perform Identical Code Folding for functions and read-only
               variables.  The optimization reduces code size and may disturb
               unwind stacks by replacing a function by equivalent one with a
               different name. The optimization works more effectively with
               link-time optimization enabled.
    
               Although the behavior is similar to the Gold Linker's ICF
               optimization, GCC ICF works on different levels and thus the
               optimizations are not same - there are equivalences that are
               found only by GCC and equivalences found only by Gold.
    
               This flag is enabled by default at **-O2** and **-Os**.
    
           **-flive-patching=**_level_
               Control GCC's optimizations to produce output suitable for
               live-patching.
    
               If the compiler's optimization uses a function's body or
               information extracted from its body to optimize/change another
               function, the latter is called an impacted function of the
               former.  If a function is patched, its impacted functions
               should be patched too.
    
               The impacted functions are determined by the compiler's
               interprocedural optimizations.  For example, a caller is
               impacted when inlining a function into its caller, cloning a
               function and changing its caller to call this new clone, or
               extracting a function's pureness/constness information to
               optimize its direct or indirect callers, etc.
    
               Usually, the more IPA optimizations enabled, the larger the
               number of impacted functions for each function.  In order to
               control the number of impacted functions and more easily
               compute the list of impacted function, IPA optimizations can
               be partially enabled at two different levels.
    
               The _level_ argument should be one of the following:
    
               **inline-clone**
                   Only enable inlining and cloning optimizations, which
                   includes inlining, cloning, interprocedural scalar
                   replacement of aggregates and partial inlining.  As a
                   result, when patching a function, all its callers and its
                   clones' callers are impacted, therefore need to be patched
                   as well.
    
                   **-flive-patching=inline-clone** disables the following
                   optimization flags: **-fwhole-program  -fipa-pta**
                   **-fipa-reference  -fipa-ra -fipa-icf  -fipa-icf-functions**
                   **-fipa-icf-variables -fipa-bit-cp  -fipa-vrp**
                   **-fipa-pure-const  -fipa-reference-addressable**
                   **-fipa-stack-alignment**
    
               **inline-only-static**
                   Only enable inlining of static functions.  As a result,
                   when patching a static function, all its callers are
                   impacted and so need to be patched as well.
    
                   In addition to all the flags that
                   **-flive-patching=inline-clone** disables,
                   **-flive-patching=inline-only-static** disables the following
                   additional optimization flags: **-fipa-cp-clone  -fipa-sra**
                   **-fpartial-inlining  -fipa-cp**
    
               When **-flive-patching** is specified without any value, the
               default value is _inline-clone_.
    
               This flag is disabled by default.
    
               Note that **-flive-patching** is not supported with link-time
               optimization (**-flto**).
    
           **-fisolate-erroneous-paths-dereference**
               Detect paths that trigger erroneous or undefined behavior due
               to dereferencing a null pointer.  Isolate those paths from the
               main control flow and turn the statement with erroneous or
               undefined behavior into a trap.  This flag is enabled by
               default at **-O2** and higher and depends on
               **-fdelete-null-pointer-checks** also being enabled.
    
           **-fisolate-erroneous-paths-attribute**
               Detect paths that trigger erroneous or undefined behavior due
               to a null value being used in a way forbidden by a
               "returns_nonnull" or "nonnull" attribute.  Isolate those paths
               from the main control flow and turn the statement with
               erroneous or undefined behavior into a trap.  This is not
               currently enabled, but may be enabled by **-O2** in the future.
    
           **-ftree-sink**
               Perform forward store motion on trees.  This flag is enabled
               by default at **-O** and higher.
    
           **-ftree-bit-ccp**
               Perform sparse conditional bit constant propagation on trees
               and propagate pointer alignment information.  This pass only
               operates on local scalar variables and is enabled by default
               at **-O1** and higher, except for **-Og**.  It requires that
               **-ftree-ccp** is enabled.
    
           **-ftree-ccp**
               Perform sparse conditional constant propagation (CCP) on
               trees.  This pass only operates on local scalar variables and
               is enabled by default at **-O** and higher.
    
           **-fssa-backprop**
               Propagate information about uses of a value up the definition
               chain in order to simplify the definitions.  For example, this
               pass strips sign operations if the sign of a value never
               matters.  The flag is enabled by default at **-O** and higher.
    
           **-fssa-phiopt**
               Perform pattern matching on SSA PHI nodes to optimize
               conditional code.  This pass is enabled by default at **-O1** and
               higher, except for **-Og**.
    
           **-ftree-switch-conversion**
               Perform conversion of simple initializations in a switch to
               initializations from a scalar array.  This flag is enabled by
               default at **-O2** and higher.
    
           **-ftree-tail-merge**
               Look for identical code sequences.  When found, replace one
               with a jump to the other.  This optimization is known as tail
               merging or cross jumping.  This flag is enabled by default at
               **-O2** and higher.  The compilation time in this pass can be
               limited using **max-tail-merge-comparisons** parameter and **max-**
               **tail-merge-iterations** parameter.
    
           **-ftree-dce**
               Perform dead code elimination (DCE) on trees.  This flag is
               enabled by default at **-O** and higher.
    
           **-ftree-builtin-call-dce**
               Perform conditional dead code elimination (DCE) for calls to
               built-in functions that may set "errno" but are otherwise free
               of side effects.  This flag is enabled by default at **-O2** and
               higher if **-Os** is not also specified.
    
           **-ftree-dominator-opts**
               Perform a variety of simple scalar cleanups (constant/copy
               propagation, redundancy elimination, range propagation and
               expression simplification) based on a dominator tree
               traversal.  This also performs jump threading (to reduce jumps
               to jumps). This flag is enabled by default at **-O** and higher.
    
           **-ftree-dse**
               Perform dead store elimination (DSE) on trees.  A dead store
               is a store into a memory location that is later overwritten by
               another store without any intervening loads.  In this case the
               earlier store can be deleted.  This flag is enabled by default
               at **-O** and higher.
    
           **-ftree-ch**
               Perform loop header copying on trees.  This is beneficial
               since it increases effectiveness of code motion optimizations.
               It also saves one jump.  This flag is enabled by default at **-O**
               and higher.  It is not enabled for **-Os** , since it usually
               increases code size.
    
           **-ftree-loop-optimize**
               Perform loop optimizations on trees.  This flag is enabled by
               default at **-O** and higher.
    
           **-ftree-loop-linear**
           **-floop-strip-mine**
           **-floop-block**
               Perform loop nest optimizations.  Same as
               **-floop-nest-optimize**.  To use this code transformation, GCC
               has to be configured with **--with-isl** to enable the Graphite
               loop transformation infrastructure.
    
           **-fgraphite-identity**
               Enable the identity transformation for graphite.  For every
               SCoP we generate the polyhedral representation and transform
               it back to gimple.  Using **-fgraphite-identity** we can check the
               costs or benefits of the GIMPLE -> GRAPHITE -> GIMPLE
               transformation.  Some minimal optimizations are also performed
               by the code generator isl, like index splitting and dead code
               elimination in loops.
    
           **-floop-nest-optimize**
               Enable the isl based loop nest optimizer.  This is a generic
               loop nest optimizer based on the Pluto optimization
               algorithms.  It calculates a loop structure optimized for
               data-locality and parallelism.  This option is experimental.
    
           **-floop-parallelize-all**
               Use the Graphite data dependence analysis to identify loops
               that can be parallelized.  Parallelize all the loops that can
               be analyzed to not contain loop carried dependences without
               checking that it is profitable to parallelize the loops.
    
           **-ftree-coalesce-vars**
               While transforming the program out of the SSA representation,
               attempt to reduce copying by coalescing versions of different
               user-defined variables, instead of just compiler temporaries.
               This may severely limit the ability to debug an optimized
               program compiled with **-fno-var-tracking-assignments**.  In the
               negated form, this flag prevents SSA coalescing of user
               variables.  This option is enabled by default if optimization
               is enabled, and it does very little otherwise.
    
           **-ftree-loop-if-convert**
               Attempt to transform conditional jumps in the innermost loops
               to branch-less equivalents.  The intent is to remove control-
               flow from the innermost loops in order to improve the ability
               of the vectorization pass to handle these loops.  This is
               enabled by default if vectorization is enabled.
    
           **-ftree-loop-distribution**
               Perform loop distribution.  This flag can improve cache
               performance on big loop bodies and allow further loop
               optimizations, like parallelization or vectorization, to take
               place.  For example, the loop
    
                       DO I = 1, N
                         A(I) = B(I) + C
                         D(I) = E(I) * F
                       ENDDO
    
               is transformed to
    
                       DO I = 1, N
                          A(I) = B(I) + C
                       ENDDO
                       DO I = 1, N
                          D(I) = E(I) * F
                       ENDDO
    
               This flag is enabled by default at **-O3**.  It is also enabled by
               **-fprofile-use** and **-fauto-profile**.
    
           **-ftree-loop-distribute-patterns**
               Perform loop distribution of patterns that can be code
               generated with calls to a library.  This flag is enabled by
               default at **-O3** , and by **-fprofile-use** and **-fauto-profile**.
    
               This pass distributes the initialization loops and generates a
               call to memset zero.  For example, the loop
    
                       DO I = 1, N
                         A(I) = 0
                         B(I) = A(I) + I
                       ENDDO
    
               is transformed to
    
                       DO I = 1, N
                          A(I) = 0
                       ENDDO
                       DO I = 1, N
                          B(I) = A(I) + I
                       ENDDO
    
               and the initialization loop is transformed into a call to
               memset zero.  This flag is enabled by default at **-O3**.  It is
               also enabled by **-fprofile-use** and **-fauto-profile**.
    
           **-floop-interchange**
               Perform loop interchange outside of graphite.  This flag can
               improve cache performance on loop nest and allow further loop
               optimizations, like vectorization, to take place.  For
               example, the loop
    
                       for (int i = 0; i < N; i++)
                         for (int j = 0; j < N; j++)
                           for (int k = 0; k < N; k++)
                             c[i][j] = c[i][j] + a[i][k]*b[k][j];
    
               is transformed to
    
                       for (int i = 0; i < N; i++)
                         for (int k = 0; k < N; k++)
                           for (int j = 0; j < N; j++)
                             c[i][j] = c[i][j] + a[i][k]*b[k][j];
    
               This flag is enabled by default at **-O3**.  It is also enabled by
               **-fprofile-use** and **-fauto-profile**.
    
           **-floop-unroll-and-jam**
               Apply unroll and jam transformations on feasible loops.  In a
               loop nest this unrolls the outer loop by some factor and fuses
               the resulting multiple inner loops.  This flag is enabled by
               default at **-O3**.  It is also enabled by **-fprofile-use** and
               **-fauto-profile**.
    
           **-ftree-loop-im**
               Perform loop invariant motion on trees.  This pass moves only
               invariants that are hard to handle at RTL level (function
               calls, operations that expand to nontrivial sequences of
               insns).  With **-funswitch-loops** it also moves operands of
               conditions that are invariant out of the loop, so that we can
               use just trivial invariantness analysis in loop unswitching.
               The pass also includes store motion.
    
           **-ftree-loop-ivcanon**
               Create a canonical counter for number of iterations in loops
               for which determining number of iterations requires
               complicated analysis.  Later optimizations then may determine
               the number easily.  Useful especially in connection with
               unrolling.
    
           **-ftree-scev-cprop**
               Perform final value replacement.  If a variable is modified in
               a loop in such a way that its value when exiting the loop can
               be determined using only its initial value and the number of
               loop iterations, replace uses of the final value by such a
               computation, provided it is sufficiently cheap.  This reduces
               data dependencies and may allow further simplifications.
               Enabled by default at **-O** and higher.
    
           **-fivopts**
               Perform induction variable optimizations (strength reduction,
               induction variable merging and induction variable elimination)
               on trees.
    
           **-ftree-parallelize-loops=n**
               Parallelize loops, i.e., split their iteration space to run in
               n threads.  This is only possible for loops whose iterations
               are independent and can be arbitrarily reordered.  The
               optimization is only profitable on multiprocessor machines,
               for loops that are CPU-intensive, rather than constrained e.g.
               by memory bandwidth.  This option implies **-pthread** , and thus
               is only supported on targets that have support for **-pthread**.
    
           **-ftree-pta**
               Perform function-local points-to analysis on trees.  This flag
               is enabled by default at **-O1** and higher, except for **-Og**.
    
           **-ftree-sra**
               Perform scalar replacement of aggregates.  This pass replaces
               structure references with scalars to prevent committing
               structures to memory too early.  This flag is enabled by
               default at **-O1** and higher, except for **-Og**.
    
           **-fstore-merging**
               Perform merging of narrow stores to consecutive memory
               addresses.  This pass merges contiguous stores of immediate
               values narrower than a word into fewer wider stores to reduce
               the number of instructions.  This is enabled by default at **-O2**
               and higher as well as **-Os**.
    
           **-ftree-ter**
               Perform temporary expression replacement during the
               SSA->normal phase.  Single use/single def temporaries are
               replaced at their use location with their defining expression.
               This results in non-GIMPLE code, but gives the expanders much
               more complex trees to work on resulting in better RTL
               generation.  This is enabled by default at **-O** and higher.
    
           **-ftree-slsr**
               Perform straight-line strength reduction on trees.  This
               recognizes related expressions involving multiplications and
               replaces them by less expensive calculations when possible.
               This is enabled by default at **-O** and higher.
    
           **-ftree-vectorize**
               Perform vectorization on trees. This flag enables
               **-ftree-loop-vectorize** and **-ftree-slp-vectorize** if not
               explicitly specified.
    
           **-ftree-loop-vectorize**
               Perform loop vectorization on trees. This flag is enabled by
               default at **-O3** and by **-ftree-vectorize** , **-fprofile-use** , and
               **-fauto-profile**.
    
           **-ftree-slp-vectorize**
               Perform basic block vectorization on trees. This flag is
               enabled by default at **-O3** and by **-ftree-vectorize** ,
               **-fprofile-use** , and **-fauto-profile**.
    
           **-fvect-cost-model=**_model_
               Alter the cost model used for vectorization.  The _model_
               argument should be one of **unlimited** , **dynamic** or **cheap**.  With
               the **unlimited** model the vectorized code-path is assumed to be
               profitable while with the **dynamic** model a runtime check guards
               the vectorized code-path to enable it only for iteration
               counts that will likely execute faster than when executing the
               original scalar loop.  The **cheap** model disables vectorization
               of loops where doing so would be cost prohibitive for example
               due to required runtime checks for data dependence or
               alignment but otherwise is equal to the **dynamic** model.  The
               default cost model depends on other optimization flags and is
               either **dynamic** or **cheap**.
    
           **-fsimd-cost-model=**_model_
               Alter the cost model used for vectorization of loops marked
               with the OpenMP simd directive.  The _model_ argument should be
               one of **unlimited** , **dynamic** , **cheap**.  All values of _model_ have
               the same meaning as described in **-fvect-cost-model** and by
               default a cost model defined with **-fvect-cost-model** is used.
    
           **-ftree-vrp**
               Perform Value Range Propagation on trees.  This is similar to
               the constant propagation pass, but instead of values, ranges
               of values are propagated.  This allows the optimizers to
               remove unnecessary range checks like array bound checks and
               null pointer checks.  This is enabled by default at **-O2** and
               higher.  Null pointer check elimination is only done if
               **-fdelete-null-pointer-checks** is enabled.
    
           **-fsplit-paths**
               Split paths leading to loop backedges.  This can improve dead
               code elimination and common subexpression elimination.  This
               is enabled by default at **-O3** and above.
    
           **-fsplit-ivs-in-unroller**
               Enables expression of values of induction variables in later
               iterations of the unrolled loop using the value in the first
               iteration.  This breaks long dependency chains, thus improving
               efficiency of the scheduling passes.
    
               A combination of **-fweb** and CSE is often sufficient to obtain
               the same effect.  However, that is not reliable in cases where
               the loop body is more complicated than a single basic block.
               It also does not work at all on some architectures due to
               restrictions in the CSE pass.
    
               This optimization is enabled by default.
    
           **-fvariable-expansion-in-unroller**
               With this option, the compiler creates multiple copies of some
               local variables when unrolling a loop, which can result in
               superior code.
    
           **-fpartial-inlining**
               Inline parts of functions.  This option has any effect only
               when inlining itself is turned on by the **-finline-functions** or
               **-finline-small-functions** options.
    
               Enabled at levels **-O2** , **-O3** , **-Os**.
    
           **-fpredictive-commoning**
               Perform predictive commoning optimization, i.e., reusing
               computations (especially memory loads and stores) performed in
               previous iterations of loops.
    
               This option is enabled at level **-O3**.  It is also enabled by
               **-fprofile-use** and **-fauto-profile**.
    
           **-fprefetch-loop-arrays**
               If supported by the target machine, generate instructions to
               prefetch memory to improve the performance of loops that
               access large arrays.
    
               This option may generate better or worse code; results are
               highly dependent on the structure of loops within the source
               code.
    
               Disabled at level **-Os**.
    
           **-fno-printf-return-value**
               Do not substitute constants for known return value of
               formatted output functions such as "sprintf", "snprintf",
               "vsprintf", and "vsnprintf" (but not "printf" of "fprintf").
               This transformation allows GCC to optimize or even eliminate
               branches based on the known return value of these functions
               called with arguments that are either constant, or whose
               values are known to be in a range that makes determining the
               exact return value possible.  For example, when
               **-fprintf-return-value** is in effect, both the branch and the
               body of the "if" statement (but not the call to "snprint") can
               be optimized away when "i" is a 32-bit or smaller integer
               because the return value is guaranteed to be at most 8.
    
                       char buf[9];
                       if (snprintf (buf, "%08x", i) >= sizeof buf)
                         ...
    
               The **-fprintf-return-value** option relies on other optimizations
               and yields best results with **-O2** and above.  It works in
               tandem with the **-Wformat-overflow** and **-Wformat-truncation**
               options.  The **-fprintf-return-value** option is enabled by
               default.
    
           **-fno-peephole**
           **-fno-peephole2**
               Disable any machine-specific peephole optimizations.  The
               difference between **-fno-peephole** and **-fno-peephole2** is in how
               they are implemented in the compiler; some targets use one,
               some use the other, a few use both.
    
               **-fpeephole** is enabled by default.  **-fpeephole2** enabled at
               levels **-O2** , **-O3** , **-Os**.
    
           **-fno-guess-branch-probability**
               Do not guess branch probabilities using heuristics.
    
               GCC uses heuristics to guess branch probabilities if they are
               not provided by profiling feedback (**-fprofile-arcs**).  These
               heuristics are based on the control flow graph.  If some
               branch probabilities are specified by "__builtin_expect", then
               the heuristics are used to guess branch probabilities for the
               rest of the control flow graph, taking the "__builtin_expect"
               info into account.  The interactions between the heuristics
               and "__builtin_expect" can be complex, and in some cases, it
               may be useful to disable the heuristics so that the effects of
               "__builtin_expect" are easier to understand.
    
               It is also possible to specify expected probability of the
               expression with "__builtin_expect_with_probability" built-in
               function.
    
               The default is **-fguess-branch-probability** at levels **-O** , **-O2** ,
               **-O3** , **-Os**.
    
           **-freorder-blocks**
               Reorder basic blocks in the compiled function in order to
               reduce number of taken branches and improve code locality.
    
               Enabled at levels **-O** , **-O2** , **-O3** , **-Os**.
    
           **-freorder-blocks-algorithm=**_algorithm_
               Use the specified algorithm for basic block reordering.  The
               _algorithm_ argument can be **simple** , which does not increase code
               size (except sometimes due to secondary effects like
               alignment), or **stc** , the "software trace cache" algorithm,
               which tries to put all often executed code together,
               minimizing the number of branches executed by making extra
               copies of code.
    
               The default is **simple** at levels **-O** , **-Os** , and **stc** at levels
               **-O2** , **-O3**.
    
           **-freorder-blocks-and-partition**
               In addition to reordering basic blocks in the compiled
               function, in order to reduce number of taken branches,
               partitions hot and cold basic blocks into separate sections of
               the assembly and _.o_ files, to improve paging and cache
               locality performance.
    
               This optimization is automatically turned off in the presence
               of exception handling or unwind tables (on targets using
               setjump/longjump or target specific scheme), for linkonce
               sections, for functions with a user-defined section attribute
               and on any architecture that does not support named sections.
               When **-fsplit-stack** is used this option is not enabled by
               default (to avoid linker errors), but may be enabled
               explicitly (if using a working linker).
    
               Enabled for x86 at levels **-O2** , **-O3** , **-Os**.
    
           **-freorder-functions**
               Reorder functions in the object file in order to improve code
               locality.  This is implemented by using special subsections
               ".text.hot" for most frequently executed functions and
               ".text.unlikely" for unlikely executed functions.  Reordering
               is done by the linker so object file format must support named
               sections and linker must place them in a reasonable way.
    
               This option isn't effective unless you either provide profile
               feedback (see **-fprofile-arcs** for details) or manually annotate
               functions with "hot" or "cold" attributes.
    
               Enabled at levels **-O2** , **-O3** , **-Os**.
    
           **-fstrict-aliasing**
               Allow the compiler to assume the strictest aliasing rules
               applicable to the language being compiled.  For C (and C++),
               this activates optimizations based on the type of expressions.
               In particular, an object of one type is assumed never to
               reside at the same address as an object of a different type,
               unless the types are almost the same.  For example, an
               "unsigned int" can alias an "int", but not a "void*" or a
               "double".  A character type may alias any other type.
    
               Pay special attention to code like this:
    
                       union a_union {
                         int i;
                         double d;
                       };
    
                       int f() {
                         union a_union t;
                         t.d = 3.0;
                         return t.i;
                       }
    
               The practice of reading from a different union member than the
               one most recently written to (called "type-punning") is
               common.  Even with **-fstrict-aliasing** , type-punning is allowed,
               provided the memory is accessed through the union type.  So,
               the code above works as expected.    However, this code might
               not:
    
                       int f() {
                         union a_union t;
                         int* ip;
                         t.d = 3.0;
                         ip = &t.i;
                         return *ip;
                       }
    
               Similarly, access by taking the address, casting the resulting
               pointer and dereferencing the result has undefined behavior,
               even if the cast uses a union type, e.g.:
    
                       int f() {
                         double d = 3.0;
                         return ((union a_union *) &d)->i;
                       }
    
               The **-fstrict-aliasing** option is enabled at levels **-O2** , **-O3** ,
               **-Os**.
    
           **-falign-functions**
           **-falign-functions=**_n_
           **-falign-functions=**_n_**:**_m_
           **-falign-functions=**_n_**:**_m_**:**_n2_
           **-falign-functions=**_n_**:**_m_**:**_n2_**:**_m2_
               Align the start of functions to the next power-of-two greater
               than _n_ , skipping up to _m_ -1 bytes.  This ensures that at least
               the first _m_ bytes of the function can be fetched by the CPU
               without crossing an _n_ -byte alignment boundary.
    
               If _m_ is not specified, it defaults to _n_.
    
               Examples: **-falign-functions=32** aligns functions to the next
               32-byte boundary, **-falign-functions=24** aligns to the next
               32-byte boundary only if this can be done by skipping 23 bytes
               or less, **-falign-functions=32:7** aligns to the next 32-byte
               boundary only if this can be done by skipping 6 bytes or less.
    
               The second pair of _n2_ :_m2_ values allows you to specify a
               secondary alignment: **-falign-functions=64:7:32:3** aligns to the
               next 64-byte boundary if this can be done by skipping 6 bytes
               or less, otherwise aligns to the next 32-byte boundary if this
               can be done by skipping 2 bytes or less.  If _m2_ is not
               specified, it defaults to _n2_.
    
               Some assemblers only support this flag when _n_ is a power of
               two; in that case, it is rounded up.
    
               **-fno-align-functions** and **-falign-functions=1** are equivalent
               and mean that functions are not aligned.
    
               If _n_ is not specified or is zero, use a machine-dependent
               default.  The maximum allowed _n_ option value is 65536.
    
               Enabled at levels **-O2** , **-O3**.
    
           **-flimit-function-alignment**
               If this option is enabled, the compiler tries to avoid
               unnecessarily overaligning functions. It attempts to instruct
               the assembler to align by the amount specified by
               **-falign-functions** , but not to skip more bytes than the size of
               the function.
    
           **-falign-labels**
           **-falign-labels=**_n_
           **-falign-labels=**_n_**:**_m_
           **-falign-labels=**_n_**:**_m_**:**_n2_
           **-falign-labels=**_n_**:**_m_**:**_n2_**:**_m2_
               Align all branch targets to a power-of-two boundary.
    
               Parameters of this option are analogous to the
               **-falign-functions** option.  **-fno-align-labels** and
               **-falign-labels=1** are equivalent and mean that labels are not
               aligned.
    
               If **-falign-loops** or **-falign-jumps** are applicable and are
               greater than this value, then their values are used instead.
    
               If _n_ is not specified or is zero, use a machine-dependent
               default which is very likely to be **1** , meaning no alignment.
               The maximum allowed _n_ option value is 65536.
    
               Enabled at levels **-O2** , **-O3**.
    
           **-falign-loops**
           **-falign-loops=**_n_
           **-falign-loops=**_n_**:**_m_
           **-falign-loops=**_n_**:**_m_**:**_n2_
           **-falign-loops=**_n_**:**_m_**:**_n2_**:**_m2_
               Align loops to a power-of-two boundary.  If the loops are
               executed many times, this makes up for any execution of the
               dummy padding instructions.
    
               Parameters of this option are analogous to the
               **-falign-functions** option.  **-fno-align-loops** and
               **-falign-loops=1** are equivalent and mean that loops are not
               aligned.  The maximum allowed _n_ option value is 65536.
    
               If _n_ is not specified or is zero, use a machine-dependent
               default.
    
               Enabled at levels **-O2** , **-O3**.
    
           **-falign-jumps**
           **-falign-jumps=**_n_
           **-falign-jumps=**_n_**:**_m_
           **-falign-jumps=**_n_**:**_m_**:**_n2_
           **-falign-jumps=**_n_**:**_m_**:**_n2_**:**_m2_
               Align branch targets to a power-of-two boundary, for branch
               targets where the targets can only be reached by jumping.  In
               this case, no dummy operations need be executed.
    
               Parameters of this option are analogous to the
               **-falign-functions** option.  **-fno-align-jumps** and
               **-falign-jumps=1** are equivalent and mean that loops are not
               aligned.
    
               If _n_ is not specified or is zero, use a machine-dependent
               default.  The maximum allowed _n_ option value is 65536.
    
               Enabled at levels **-O2** , **-O3**.
    
           **-funit-at-a-time**
               This option is left for compatibility reasons.
               **-funit-at-a-time** has no effect, while **-fno-unit-at-a-time**
               implies **-fno-toplevel-reorder** and **-fno-section-anchors**.
    
               Enabled by default.
    
           **-fno-toplevel-reorder**
               Do not reorder top-level functions, variables, and "asm"
               statements.  Output them in the same order that they appear in
               the input file.  When this option is used, unreferenced static
               variables are not removed.  This option is intended to support
               existing code that relies on a particular ordering.  For new
               code, it is better to use attributes when possible.
    
               **-ftoplevel-reorder** is the default at **-O1** and higher, and also
               at **-O0** if **-fsection-anchors** is explicitly requested.
               Additionally **-fno-toplevel-reorder** implies
               **-fno-section-anchors**.
    
           **-fweb**
               Constructs webs as commonly used for register allocation
               purposes and assign each web individual pseudo register.  This
               allows the register allocation pass to operate on pseudos
               directly, but also strengthens several other optimization
               passes, such as CSE, loop optimizer and trivial dead code
               remover.  It can, however, make debugging impossible, since
               variables no longer stay in a "home register".
    
               Enabled by default with **-funroll-loops**.
    
           **-fwhole-program**
               Assume that the current compilation unit represents the whole
               program being compiled.  All public functions and variables
               with the exception of "main" and those merged by attribute
               "externally_visible" become static functions and in effect are
               optimized more aggressively by interprocedural optimizers.
    
               This option should not be used in combination with **-flto**.
               Instead relying on a linker plugin should provide safer and
               more precise information.
    
           **-flto[=**_n_**]**
               This option runs the standard link-time optimizer.  When
               invoked with source code, it generates GIMPLE (one of GCC's
               internal representations) and writes it to special ELF
               sections in the object file.  When the object files are linked
               together, all the function bodies are read from these ELF
               sections and instantiated as if they had been part of the same
               translation unit.
    
               To use the link-time optimizer, **-flto** and optimization options
               should be specified at compile time and during the final link.
               It is recommended that you compile all the files participating
               in the same link with the same options and also specify those
               options at link time.  For example:
    
                       gcc -c -O2 -flto foo.c
                       gcc -c -O2 -flto bar.c
                       gcc -o myprog -flto -O2 foo.o bar.o
    
               The first two invocations to GCC save a bytecode
               representation of GIMPLE into special ELF sections inside
               _foo.o_ and _bar.o_.  The final invocation reads the GIMPLE
               bytecode from _foo.o_ and _bar.o_ , merges the two files into a
               single internal image, and compiles the result as usual.
               Since both _foo.o_ and _bar.o_ are merged into a single image,
               this causes all the interprocedural analyses and optimizations
               in GCC to work across the two files as if they were a single
               one.  This means, for example, that the inliner is able to
               inline functions in _bar.o_ into functions in _foo.o_ and vice-
               versa.
    
               Another (simpler) way to enable link-time optimization is:
    
                       gcc -o myprog -flto -O2 foo.c bar.c
    
               The above generates bytecode for _foo.c_ and _bar.c_ , merges them
               together into a single GIMPLE representation and optimizes
               them as usual to produce _myprog_.
    
               The important thing to keep in mind is that to enable link-
               time optimizations you need to use the GCC driver to perform
               the link step.  GCC automatically performs link-time
               optimization if any of the objects involved were compiled with
               the **-flto** command-line option.  You can always override the
               automatic decision to do link-time optimization by passing
               **-fno-lto** to the link command.
    
               To make whole program optimization effective, it is necessary
               to make certain whole program assumptions.  The compiler needs
               to know what functions and variables can be accessed by
               libraries and runtime outside of the link-time optimized unit.
               When supported by the linker, the linker plugin (see
               **-fuse-linker-plugin**) passes information to the compiler about
               used and externally visible symbols.  When the linker plugin
               is not available, **-fwhole-program** should be used to allow the
               compiler to make these assumptions, which leads to more
               aggressive optimization decisions.
    
               When a file is compiled with **-flto** without
               **-fuse-linker-plugin** , the generated object file is larger than
               a regular object file because it contains GIMPLE bytecodes and
               the usual final code (see **-ffat-lto-objects**.  This means that
               object files with LTO information can be linked as normal
               object files; if **-fno-lto** is passed to the linker, no
               interprocedural optimizations are applied.  Note that when
               **-fno-fat-lto-objects** is enabled the compile stage is faster
               but you cannot perform a regular, non-LTO link on them.
    
               When producing the final binary, GCC only applies link-time
               optimizations to those files that contain bytecode.
               Therefore, you can mix and match object files and libraries
               with GIMPLE bytecodes and final object code.  GCC
               automatically selects which files to optimize in LTO mode and
               which files to link without further processing.
    
               Generally, options specified at link time override those
               specified at compile time, although in some cases GCC attempts
               to infer link-time options from the settings used to compile
               the input files.
    
               If you do not specify an optimization level option **-O** at link
               time, then GCC uses the highest optimization level used when
               compiling the object files.  Note that it is generally
               ineffective to specify an optimization level option only at
               link time and not at compile time, for two reasons.  First,
               compiling without optimization suppresses compiler passes that
               gather information needed for effective optimization at link
               time.  Second, some early optimization passes can be performed
               only at compile time and not at link time.
    
               There are some code generation flags preserved by GCC when
               generating bytecodes, as they need to be used during the final
               link.  Currently, the following options and their settings are
               taken from the first object file that explicitly specifies
               them: **-fPIC** , **-fpic** , **-fpie** , **-fcommon** , **-fexceptions** ,
               **-fnon-call-exceptions** , **-fgnu-tm** and all the **-m** target flags.
    
               Certain ABI-changing flags are required to match in all
               compilation units, and trying to override this at link time
               with a conflicting value is ignored.  This includes options
               such as **-freg-struct-return** and **-fpcc-struct-return**.
    
               Other options such as **-ffp-contract** , **-fno-strict-overflow** ,
               **-fwrapv** , **-fno-trapv** or **-fno-strict-aliasing** are passed through
               to the link stage and merged conservatively for conflicting
               translation units.  Specifically **-fno-strict-overflow** , **-fwrapv**
               and **-fno-trapv** take precedence; and for example
               **-ffp-contract=off** takes precedence over **-ffp-contract=fast**.
               You can override them at link time.
    
               When you need to pass options to the assembler via **-Wa** or
               **-Xassembler** make sure to either compile such translation units
               with **-fno-lto** or consistently use the same assembler options
               on all translation units.  You can alternatively also specify
               assembler options at LTO link time.
    
               If LTO encounters objects with C linkage declared with
               incompatible types in separate translation units to be linked
               together (undefined behavior according to ISO C99 6.2.7), a
               non-fatal diagnostic may be issued.  The behavior is still
               undefined at run time.  Similar diagnostics may be raised for
               other languages.
    
               Another feature of LTO is that it is possible to apply
               interprocedural optimizations on files written in different
               languages:
    
                       gcc -c -flto foo.c
                       g++ -c -flto bar.cc
                       gfortran -c -flto baz.f90
                       g++ -o myprog -flto -O3 foo.o bar.o baz.o -lgfortran
    
               Notice that the final link is done with **g++** to get the C++
               runtime libraries and **-lgfortran** is added to get the Fortran
               runtime libraries.  In general, when mixing languages in LTO
               mode, you should use the same link command options as when
               mixing languages in a regular (non-LTO) compilation.
    
               If object files containing GIMPLE bytecode are stored in a
               library archive, say _libfoo.a_ , it is possible to extract and
               use them in an LTO link if you are using a linker with plugin
               support.  To create static libraries suitable for LTO, use
               **gcc-ar** and **gcc-ranlib** instead of **ar** and **ranlib** ; to show the
               symbols of object files with GIMPLE bytecode, use **gcc-nm**.
               Those commands require that **ar** , **ranlib** and **nm** have been
               compiled with plugin support.  At link time, use the flag
               **-fuse-linker-plugin** to ensure that the library participates in
               the LTO optimization process:
    
                       gcc -o myprog -O2 -flto -fuse-linker-plugin a.o b.o -lfoo
    
               With the linker plugin enabled, the linker extracts the needed
               GIMPLE files from _libfoo.a_ and passes them on to the running
               GCC to make them part of the aggregated GIMPLE image to be
               optimized.
    
               If you are not using a linker with plugin support and/or do
               not enable the linker plugin, then the objects inside _libfoo.a_
               are extracted and linked as usual, but they do not participate
               in the LTO optimization process.  In order to make a static
               library suitable for both LTO optimization and usual linkage,
               compile its object files with **-flto -ffat-lto-objects**.
    
               Link-time optimizations do not require the presence of the
               whole program to operate.  If the program does not require any
               symbols to be exported, it is possible to combine **-flto** and
               **-fwhole-program** to allow the interprocedural optimizers to use
               more aggressive assumptions which may lead to improved
               optimization opportunities.  Use of **-fwhole-program** is not
               needed when linker plugin is active (see **-fuse-linker-plugin**).
    
               The current implementation of LTO makes no attempt to generate
               bytecode that is portable between different types of hosts.
               The bytecode files are versioned and there is a strict version
               check, so bytecode files generated in one version of GCC do
               not work with an older or newer version of GCC.
    
               Link-time optimization does not work well with generation of
               debugging information on systems other than those using a
               combination of ELF and DWARF.
    
               If you specify the optional _n_ , the optimization and code
               generation done at link time is executed in parallel using _n_
               parallel jobs by utilizing an installed **make** program.  The
               environment variable **MAKE** may be used to override the program
               used.  The default value for _n_ is 1.
    
               You can also specify **-flto=jobserver** to use GNU make's job
               server mode to determine the number of parallel jobs. This is
               useful when the Makefile calling GCC is already executing in
               parallel.  You must prepend a **+** to the command recipe in the
               parent Makefile for this to work.  This option likely only
               works if **MAKE** is GNU make.
    
           **-flto-partition=**_alg_
               Specify the partitioning algorithm used by the link-time
               optimizer.  The value is either **1to1** to specify a partitioning
               mirroring the original source files or **balanced** to specify
               partitioning into equally sized chunks (whenever possible) or
               **max** to create new partition for every symbol where possible.
               Specifying **none** as an algorithm disables partitioning and
               streaming completely.  The default value is **balanced**. While
               **1to1** can be used as an workaround for various code ordering
               issues, the **max** partitioning is intended for internal testing
               only.  The value **one** specifies that exactly one partition
               should be used while the value **none** bypasses partitioning and
               executes the link-time optimization step directly from the WPA
               phase.
    
           **-flto-odr-type-merging**
               Enable streaming of mangled types names of C++ types and their
               unification at link time.  This increases size of LTO object
               files, but enables diagnostics about One Definition Rule
               violations.
    
           **-flto-compression-level=**_n_
               This option specifies the level of compression used for
               intermediate language written to LTO object files, and is only
               meaningful in conjunction with LTO mode (**-flto**).  Valid values
               are 0 (no compression) to 9 (maximum compression).  Values
               outside this range are clamped to either 0 or 9.  If the
               option is not given, a default balanced compression setting is
               used.
    
           **-fuse-linker-plugin**
               Enables the use of a linker plugin during link-time
               optimization.  This option relies on plugin support in the
               linker, which is available in gold or in GNU ld 2.21 or newer.
    
               This option enables the extraction of object files with GIMPLE
               bytecode out of library archives. This improves the quality of
               optimization by exposing more code to the link-time optimizer.
               This information specifies what symbols can be accessed
               externally (by non-LTO object or during dynamic linking).
               Resulting code quality improvements on binaries (and shared
               libraries that use hidden visibility) are similar to
               **-fwhole-program**.  See **-flto** for a description of the effect of
               this flag and how to use it.
    
               This option is enabled by default when LTO support in GCC is
               enabled and GCC was configured for use with a linker
               supporting plugins (GNU ld 2.21 or newer or gold).
    
           **-ffat-lto-objects**
               Fat LTO objects are object files that contain both the
               intermediate language and the object code. This makes them
               usable for both LTO linking and normal linking. This option is
               effective only when compiling with **-flto** and is ignored at
               link time.
    
               **-fno-fat-lto-objects** improves compilation time over plain LTO,
               but requires the complete toolchain to be aware of LTO. It
               requires a linker with linker plugin support for basic
               functionality.  Additionally, **nm** , **ar** and **ranlib** need to
               support linker plugins to allow a full-featured build
               environment (capable of building static libraries etc).  GCC
               provides the **gcc-ar** , **gcc-nm** , **gcc-ranlib** wrappers to pass the
               right options to these tools. With non fat LTO makefiles need
               to be modified to use them.
    
               Note that modern binutils provide plugin auto-load mechanism.
               Installing the linker plugin into _$libdir/bfd-plugins_ has the
               same effect as usage of the command wrappers (**gcc-ar** , **gcc-nm**
               and **gcc-ranlib**).
    
               The default is **-fno-fat-lto-objects** on targets with linker
               plugin support.
    
           **-fcompare-elim**
               After register allocation and post-register allocation
               instruction splitting, identify arithmetic instructions that
               compute processor flags similar to a comparison operation
               based on that arithmetic.  If possible, eliminate the explicit
               comparison operation.
    
               This pass only applies to certain targets that cannot
               explicitly represent the comparison operation before register
               allocation is complete.
    
               Enabled at levels **-O** , **-O2** , **-O3** , **-Os**.
    
           **-fcprop-registers**
               After register allocation and post-register allocation
               instruction splitting, perform a copy-propagation pass to try
               to reduce scheduling dependencies and occasionally eliminate
               the copy.
    
               Enabled at levels **-O** , **-O2** , **-O3** , **-Os**.
    
           **-fprofile-correction**
               Profiles collected using an instrumented binary for multi-
               threaded programs may be inconsistent due to missed counter
               updates. When this option is specified, GCC uses heuristics to
               correct or smooth out such inconsistencies. By default, GCC
               emits an error message when an inconsistent profile is
               detected.
    
               This option is enabled by **-fauto-profile**.
    
           **-fprofile-use**
           **-fprofile-use=**_path_
               Enable profile feedback-directed optimizations, and the
               following optimizations, many of which are generally
               profitable only with profile feedback available:
    
               **-fbranch-probabilities  -fprofile-values -funroll-loops**
               **-fpeel-loops  -ftracer  -fvpt -finline-functions  -fipa-cp**
               **-fipa-cp-clone  -fipa-bit-cp -fpredictive-commoning**
               **-fsplit-loops  -funswitch-loops -fgcse-after-reload**
               **-ftree-loop-vectorize  -ftree-slp-vectorize**
               **-fvect-cost-model=dynamic  -ftree-loop-distribute-patterns**
               **-fprofile-reorder-functions**
    
               Before you can use this option, you must first generate
               profiling information.
    
               By default, GCC emits an error message if the feedback
               profiles do not match the source code.  This error can be
               turned into a warning by using **-Wno-error=coverage-mismatch**.
               Note this may result in poorly optimized code.  Additionally,
               by default, GCC also emits a warning message if the feedback
               profiles do not exist (see **-Wmissing-profile**).
    
               If _path_ is specified, GCC looks at the _path_ to find the
               profile feedback data files. See **-fprofile-dir**.
    
           **-fauto-profile**
           **-fauto-profile=**_path_
               Enable sampling-based feedback-directed optimizations, and the
               following optimizations, many of which are generally
               profitable only with profile feedback available:
    
               **-fbranch-probabilities  -fprofile-values -funroll-loops**
               **-fpeel-loops  -ftracer  -fvpt -finline-functions  -fipa-cp**
               **-fipa-cp-clone  -fipa-bit-cp -fpredictive-commoning**
               **-fsplit-loops  -funswitch-loops -fgcse-after-reload**
               **-ftree-loop-vectorize  -ftree-slp-vectorize**
               **-fvect-cost-model=dynamic  -ftree-loop-distribute-patterns**
               **-fprofile-correction**
    
               _path_ is the name of a file containing AutoFDO profile
               information.  If omitted, it defaults to _fbdata.afdo_ in the
               current directory.
    
               Producing an AutoFDO profile data file requires running your
               program with the **perf** utility on a supported GNU/Linux target
               system.  For more information, see
               <**https://perf.wiki.kernel.org/ **>.
    
               E.g.
    
                       perf record -e br_inst_retired:near_taken -b -o perf.data \
                           -- your_program
    
               Then use the **create_gcov** tool to convert the raw profile data
               to a format that can be used by GCC.  You must also supply the
               unstripped binary for your program to this tool.  See
               <**https://github.com/google/autofdo **>.
    
               E.g.
    
                       create_gcov --binary=your_program.unstripped --profile=perf.data \
                           --gcov=profile.afdo
    
           The following options control compiler behavior regarding
           floating-point arithmetic.  These options trade off between speed
           and correctness.  All must be specifically enabled.
    
           **-ffloat-store**
               Do not store floating-point variables in registers, and
               inhibit other options that might change whether a floating-
               point value is taken from a register or memory.
    
               This option prevents undesirable excess precision on machines
               such as the 68000 where the floating registers (of the 68881)
               keep more precision than a "double" is supposed to have.
               Similarly for the x86 architecture.  For most programs, the
               excess precision does only good, but a few programs rely on
               the precise definition of IEEE floating point.  Use
               **-ffloat-store** for such programs, after modifying them to store
               all pertinent intermediate computations into variables.
    
           **-fexcess-precision=**_style_
               This option allows further control over excess precision on
               machines where floating-point operations occur in a format
               with more precision or range than the IEEE standard and
               interchange floating-point types.  By default,
               **-fexcess-precision=fast** is in effect; this means that
               operations may be carried out in a wider precision than the
               types specified in the source if that would result in faster
               code, and it is unpredictable when rounding to the types
               specified in the source code takes place.  When compiling C,
               if **-fexcess-precision=standard** is specified then excess
               precision follows the rules specified in ISO C99; in
               particular, both casts and assignments cause values to be
               rounded to their semantic types (whereas **-ffloat-store** only
               affects assignments).  This option is enabled by default for C
               if a strict conformance option such as **-std=c99** is used.
               **-ffast-math** enables **-fexcess-precision=fast** by default
               regardless of whether a strict conformance option is used.
    
               **-fexcess-precision=standard** is not implemented for languages
               other than C.  On the x86, it has no effect if **-mfpmath=sse** or
               **-mfpmath=sse+387** is specified; in the former case, IEEE
               semantics apply without excess precision, and in the latter,
               rounding is unpredictable.
    
           **-ffast-math**
               Sets the options **-fno-math-errno** , **-funsafe-math-optimizations** ,
               **-ffinite-math-only** , **-fno-rounding-math** , **-fno-signaling-nans** ,
               **-fcx-limited-range** and **-fexcess-precision=fast**.
    
               This option causes the preprocessor macro "__FAST_MATH__" to
               be defined.
    
               This option is not turned on by any **-O** option besides **-Ofast**
               since it can result in incorrect output for programs that
               depend on an exact implementation of IEEE or ISO
               rules/specifications for math functions. It may, however,
               yield faster code for programs that do not require the
               guarantees of these specifications.
    
           **-fno-math-errno**
               Do not set "errno" after calling math functions that are
               executed with a single instruction, e.g., "sqrt".  A program
               that relies on IEEE exceptions for math error handling may
               want to use this flag for speed while maintaining IEEE
               arithmetic compatibility.
    
               This option is not turned on by any **-O** option since it can
               result in incorrect output for programs that depend on an
               exact implementation of IEEE or ISO rules/specifications for
               math functions. It may, however, yield faster code for
               programs that do not require the guarantees of these
               specifications.
    
               The default is **-fmath-errno**.
    
               On Darwin systems, the math library never sets "errno".  There
               is therefore no reason for the compiler to consider the
               possibility that it might, and **-fno-math-errno** is the default.
    
           **-funsafe-math-optimizations**
               Allow optimizations for floating-point arithmetic that (a)
               assume that arguments and results are valid and (b) may
               violate IEEE or ANSI standards.  When used at link time, it
               may include libraries or startup files that change the default
               FPU control word or other similar optimizations.
    
               This option is not turned on by any **-O** option since it can
               result in incorrect output for programs that depend on an
               exact implementation of IEEE or ISO rules/specifications for
               math functions. It may, however, yield faster code for
               programs that do not require the guarantees of these
               specifications.  Enables **-fno-signed-zeros** ,
               **-fno-trapping-math** , **-fassociative-math** and **-freciprocal-math**.
    
               The default is **-fno-unsafe-math-optimizations**.
    
           **-fassociative-math**
               Allow re-association of operands in series of floating-point
               operations.  This violates the ISO C and C++ language standard
               by possibly changing computation result.  NOTE: re-ordering
               may change the sign of zero as well as ignore NaNs and inhibit
               or create underflow or overflow (and thus cannot be used on
               code that relies on rounding behavior like "(x + 2**52) -
               2**52".  May also reorder floating-point comparisons and thus
               may not be used when ordered comparisons are required.  This
               option requires that both **-fno-signed-zeros** and
               **-fno-trapping-math** be in effect.  Moreover, it doesn't make
               much sense with **-frounding-math**. For Fortran the option is
               automatically enabled when both **-fno-signed-zeros** and
               **-fno-trapping-math** are in effect.
    
               The default is **-fno-associative-math**.
    
           **-freciprocal-math**
               Allow the reciprocal of a value to be used instead of dividing
               by the value if this enables optimizations.  For example "x /
               y" can be replaced with "x * (1/y)", which is useful if
               "(1/y)" is subject to common subexpression elimination.  Note
               that this loses precision and increases the number of flops
               operating on the value.
    
               The default is **-fno-reciprocal-math**.
    
           **-ffinite-math-only**
               Allow optimizations for floating-point arithmetic that assume
               that arguments and results are not NaNs or +-Infs.
    
               This option is not turned on by any **-O** option since it can
               result in incorrect output for programs that depend on an
               exact implementation of IEEE or ISO rules/specifications for
               math functions. It may, however, yield faster code for
               programs that do not require the guarantees of these
               specifications.
    
               The default is **-fno-finite-math-only**.
    
           **-fno-signed-zeros**
               Allow optimizations for floating-point arithmetic that ignore
               the signedness of zero.  IEEE arithmetic specifies the
               behavior of distinct +0.0 and -0.0 values, which then
               prohibits simplification of expressions such as x+0.0 or 0.0*x
               (even with **-ffinite-math-only**).  This option implies that the
               sign of a zero result isn't significant.
    
               The default is **-fsigned-zeros**.
    
           **-fno-trapping-math**
               Compile code assuming that floating-point operations cannot
               generate user-visible traps.  These traps include division by
               zero, overflow, underflow, inexact result and invalid
               operation.  This option requires that **-fno-signaling-nans** be
               in effect.  Setting this option may allow faster code if one
               relies on "non-stop" IEEE arithmetic, for example.
    
               This option should never be turned on by any **-O** option since
               it can result in incorrect output for programs that depend on
               an exact implementation of IEEE or ISO rules/specifications
               for math functions.
    
               The default is **-ftrapping-math**.
    
           **-frounding-math**
               Disable transformations and optimizations that assume default
               floating-point rounding behavior.  This is round-to-zero for
               all floating point to integer conversions, and round-to-
               nearest for all other arithmetic truncations.  This option
               should be specified for programs that change the FP rounding
               mode dynamically, or that may be executed with a non-default
               rounding mode.  This option disables constant folding of
               floating-point expressions at compile time (which may be
               affected by rounding mode) and arithmetic transformations that
               are unsafe in the presence of sign-dependent rounding modes.
    
               The default is **-fno-rounding-math**.
    
               This option is experimental and does not currently guarantee
               to disable all GCC optimizations that are affected by rounding
               mode.  Future versions of GCC may provide finer control of
               this setting using C99's "FENV_ACCESS" pragma.  This command-
               line option will be used to specify the default state for
               "FENV_ACCESS".
    
           **-fsignaling-nans**
               Compile code assuming that IEEE signaling NaNs may generate
               user-visible traps during floating-point operations.  Setting
               this option disables optimizations that may change the number
               of exceptions visible with signaling NaNs.  This option
               implies **-ftrapping-math**.
    
               This option causes the preprocessor macro "__SUPPORT_SNAN__"
               to be defined.
    
               The default is **-fno-signaling-nans**.
    
               This option is experimental and does not currently guarantee
               to disable all GCC optimizations that affect signaling NaN
               behavior.
    
           **-fno-fp-int-builtin-inexact**
               Do not allow the built-in functions "ceil", "floor", "round"
               and "trunc", and their "float" and "long double" variants, to
               generate code that raises the "inexact" floating-point
               exception for noninteger arguments.  ISO C99 and C11 allow
               these functions to raise the "inexact" exception, but ISO/IEC
               TS 18661-1:2014, the C bindings to IEEE 754-2008, does not
               allow these functions to do so.
    
               The default is **-ffp-int-builtin-inexact** , allowing the
               exception to be raised.  This option does nothing unless
               **-ftrapping-math** is in effect.
    
               Even if **-fno-fp-int-builtin-inexact** is used, if the functions
               generate a call to a library function then the "inexact"
               exception may be raised if the library implementation does not
               follow TS 18661.
    
           **-fsingle-precision-constant**
               Treat floating-point constants as single precision instead of
               implicitly converting them to double-precision constants.
    
           **-fcx-limited-range**
               When enabled, this option states that a range reduction step
               is not needed when performing complex division.  Also, there
               is no checking whether the result of a complex multiplication
               or division is "NaN + I*NaN", with an attempt to rescue the
               situation in that case.  The default is **-fno-cx-limited-range** ,
               but is enabled by **-ffast-math**.
    
               This option controls the default setting of the ISO C99
               "CX_LIMITED_RANGE" pragma.  Nevertheless, the option applies
               to all languages.
    
           **-fcx-fortran-rules**
               Complex multiplication and division follow Fortran rules.
               Range reduction is done as part of complex division, but there
               is no checking whether the result of a complex multiplication
               or division is "NaN + I*NaN", with an attempt to rescue the
               situation in that case.
    
               The default is **-fno-cx-fortran-rules**.
    
           The following options control optimizations that may improve
           performance, but are not enabled by any **-O** options.  This section
           includes experimental options that may produce broken code.
    
           **-fbranch-probabilities**
               After running a program compiled with **-fprofile-arcs** , you can
               compile it a second time using **-fbranch-probabilities** , to
               improve optimizations based on the number of times each branch
               was taken.  When a program compiled with **-fprofile-arcs** exits,
               it saves arc execution counts to a file called _sourcename.gcda_
               for each source file.  The information in this data file is
               very dependent on the structure of the generated code, so you
               must use the same source code and the same optimization
               options for both compilations.
    
               With **-fbranch-probabilities** , GCC puts a **REG_BR_PROB** note on
               each **JUMP_INSN** and **CALL_INSN**.  These can be used to improve
               optimization.  Currently, they are only used in one place: in
               _reorg.c_ , instead of guessing which path a branch is most
               likely to take, the **REG_BR_PROB** values are used to exactly
               determine which path is taken more often.
    
               Enabled by **-fprofile-use** and **-fauto-profile**.
    
           **-fprofile-values**
               If combined with **-fprofile-arcs** , it adds code so that some
               data about values of expressions in the program is gathered.
    
               With **-fbranch-probabilities** , it reads back the data gathered
               from profiling values of expressions for usage in
               optimizations.
    
               Enabled by **-fprofile-generate** , **-fprofile-use** , and
               **-fauto-profile**.
    
           **-fprofile-reorder-functions**
               Function reordering based on profile instrumentation collects
               first time of execution of a function and orders these
               functions in ascending order.
    
               Enabled with **-fprofile-use**.
    
           **-fvpt**
               If combined with **-fprofile-arcs** , this option instructs the
               compiler to add code to gather information about values of
               expressions.
    
               With **-fbranch-probabilities** , it reads back the data gathered
               and actually performs the optimizations based on them.
               Currently the optimizations include specialization of division
               operations using the knowledge about the value of the
               denominator.
    
               Enabled with **-fprofile-use** and **-fauto-profile**.
    
           **-frename-registers**
               Attempt to avoid false dependencies in scheduled code by
               making use of registers left over after register allocation.
               This optimization most benefits processors with lots of
               registers.  Depending on the debug information format adopted
               by the target, however, it can make debugging impossible,
               since variables no longer stay in a "home register".
    
               Enabled by default with **-funroll-loops**.
    
           **-fschedule-fusion**
               Performs a target dependent pass over the instruction stream
               to schedule instructions of same type together because target
               machine can execute them more efficiently if they are adjacent
               to each other in the instruction flow.
    
               Enabled at levels **-O2** , **-O3** , **-Os**.
    
           **-ftracer**
               Perform tail duplication to enlarge superblock size.  This
               transformation simplifies the control flow of the function
               allowing other optimizations to do a better job.
    
               Enabled by **-fprofile-use** and **-fauto-profile**.
    
           **-funroll-loops**
               Unroll loops whose number of iterations can be determined at
               compile time or upon entry to the loop.  **-funroll-loops**
               implies **-frerun-cse-after-loop** , **-fweb** and **-frename-registers**.
               It also turns on complete loop peeling (i.e. complete removal
               of loops with a small constant number of iterations).  This
               option makes code larger, and may or may not make it run
               faster.
    
               Enabled by **-fprofile-use** and **-fauto-profile**.
    
           **-funroll-all-loops**
               Unroll all loops, even if their number of iterations is
               uncertain when the loop is entered.  This usually makes
               programs run more slowly.  **-funroll-all-loops** implies the same
               options as **-funroll-loops**.
    
           **-fpeel-loops**
               Peels loops for which there is enough information that they do
               not roll much (from profile feedback or static analysis).  It
               also turns on complete loop peeling (i.e. complete removal of
               loops with small constant number of iterations).
    
               Enabled by **-O3** , **-fprofile-use** , and **-fauto-profile**.
    
           **-fmove-loop-invariants**
               Enables the loop invariant motion pass in the RTL loop
               optimizer.  Enabled at level **-O1** and higher, except for **-Og**.
    
           **-fsplit-loops**
               Split a loop into two if it contains a condition that's always
               true for one side of the iteration space and false for the
               other.
    
               Enabled by **-fprofile-use** and **-fauto-profile**.
    
           **-funswitch-loops**
               Move branches with loop invariant conditions out of the loop,
               with duplicates of the loop on both branches (modified
               according to result of the condition).
    
               Enabled by **-fprofile-use** and **-fauto-profile**.
    
           **-fversion-loops-for-strides**
               If a loop iterates over an array with a variable stride,
               create another version of the loop that assumes the stride is
               always one.  For example:
    
                       for (int i = 0; i < n; ++i)
                         x[i * stride] = ...;
    
               becomes:
    
                       if (stride == 1)
                         for (int i = 0; i < n; ++i)
                           x[i] = ...;
                       else
                         for (int i = 0; i < n; ++i)
                           x[i * stride] = ...;
    
               This is particularly useful for assumed-shape arrays in
               Fortran where (for example) it allows better vectorization
               assuming contiguous accesses.  This flag is enabled by default
               at **-O3**.  It is also enabled by **-fprofile-use** and
               **-fauto-profile**.
    
           **-ffunction-sections**
           **-fdata-sections**
               Place each function or data item into its own section in the
               output file if the target supports arbitrary sections.  The
               name of the function or the name of the data item determines
               the section's name in the output file.
    
               Use these options on systems where the linker can perform
               optimizations to improve locality of reference in the
               instruction space.  Most systems using the ELF object format
               have linkers with such optimizations.  On AIX, the linker
               rearranges sections (CSECTs) based on the call graph.  The
               performance impact varies.
    
               Together with a linker garbage collection (linker
               **--gc-sections** option) these options may lead to smaller
               statically-linked executables (after stripping).
    
               On ELF/DWARF systems these options do not degenerate the
               quality of the debug information.  There could be issues with
               other object files/debug info formats.
    
               Only use these options when there are significant benefits
               from doing so.  When you specify these options, the assembler
               and linker create larger object and executable files and are
               also slower.  These options affect code generation.  They
               prevent optimizations by the compiler and assembler using
               relative locations inside a translation unit since the
               locations are unknown until link time.  An example of such an
               optimization is relaxing calls to short call instructions.
    
           **-fbranch-target-load-optimize**
               Perform branch target register load optimization before
               prologue / epilogue threading.  The use of target registers
               can typically be exposed only during reload, thus hoisting
               loads out of loops and doing inter-block scheduling needs a
               separate optimization pass.
    
           **-fbranch-target-load-optimize2**
               Perform branch target register load optimization after
               prologue / epilogue threading.
    
           **-fbtr-bb-exclusive**
               When performing branch target register load optimization,
               don't reuse branch target registers within any basic block.
    
           **-fstdarg-opt**
               Optimize the prologue of variadic argument functions with
               respect to usage of those arguments.
    
           **-fsection-anchors**
               Try to reduce the number of symbolic address calculations by
               using shared "anchor" symbols to address nearby objects.  This
               transformation can help to reduce the number of GOT entries
               and GOT accesses on some targets.
    
               For example, the implementation of the following function
               "foo":
    
                       static int a, b, c;
                       int foo (void) { return a + b + c; }
    
               usually calculates the addresses of all three variables, but
               if you compile it with **-fsection-anchors** , it accesses the
               variables from a common anchor point instead.  The effect is
               similar to the following pseudocode (which isn't valid C):
    
                       int foo (void)
                       {
                         register int *xr = &x;
                         return xr[&a - &x] + xr[&b - &x] + xr[&c - &x];
                       }
    
               Not all targets support this option.
    
           **--param** _name_**=**_value_
               In some places, GCC uses various constants to control the
               amount of optimization that is done.  For example, GCC does
               not inline functions that contain more than a certain number
               of instructions.  You can control some of these constants on
               the command line using the **--param** option.
    
               The names of specific parameters, and the meaning of the
               values, are tied to the internals of the compiler, and are
               subject to change without notice in future releases.
    
               In order to get minimal, maximal and default value of a
               parameter, one can use **--help=param -Q** options.
    
               In each case, the _value_ is an integer.  The allowable choices
               for _name_ are:
    
               **predictable-branch-outcome**
                   When branch is predicted to be taken with probability
                   lower than this threshold (in percent), then it is
                   considered well predictable.
    
               **max-rtl-if-conversion-insns**
                   RTL if-conversion tries to remove conditional branches
                   around a block and replace them with conditionally
                   executed instructions.  This parameter gives the maximum
                   number of instructions in a block which should be
                   considered for if-conversion.  The compiler will also use
                   other heuristics to decide whether if-conversion is likely
                   to be profitable.
    
               **max-rtl-if-conversion-predictable-cost**
               **max-rtl-if-conversion-unpredictable-cost**
                   RTL if-conversion will try to remove conditional branches
                   around a block and replace them with conditionally
                   executed instructions.  These parameters give the maximum
                   permissible cost for the sequence that would be generated
                   by if-conversion depending on whether the branch is
                   statically determined to be predictable or not.  The units
                   for this parameter are the same as those for the GCC
                   internal seq_cost metric.  The compiler will try to
                   provide a reasonable default for this parameter using the
                   BRANCH_COST target macro.
    
               **max-crossjump-edges**
                   The maximum number of incoming edges to consider for
                   cross-jumping.  The algorithm used by **-fcrossjumping** is
                   O(N^2) in the number of edges incoming to each block.
                   Increasing values mean more aggressive optimization,
                   making the compilation time increase with probably small
                   improvement in executable size.
    
               **min-crossjump-insns**
                   The minimum number of instructions that must be matched at
                   the end of two blocks before cross-jumping is performed on
                   them.  This value is ignored in the case where all
                   instructions in the block being cross-jumped from are
                   matched.
    
               **max-grow-copy-bb-insns**
                   The maximum code size expansion factor when copying basic
                   blocks instead of jumping.  The expansion is relative to a
                   jump instruction.
    
               **max-goto-duplication-insns**
                   The maximum number of instructions to duplicate to a block
                   that jumps to a computed goto.  To avoid O(N^2) behavior
                   in a number of passes, GCC factors computed gotos early in
                   the compilation process, and unfactors them as late as
                   possible.  Only computed jumps at the end of a basic
                   blocks with no more than max-goto-duplication-insns are
                   unfactored.
    
               **max-delay-slot-insn-search**
                   The maximum number of instructions to consider when
                   looking for an instruction to fill a delay slot.  If more
                   than this arbitrary number of instructions are searched,
                   the time savings from filling the delay slot are minimal,
                   so stop searching.  Increasing values mean more aggressive
                   optimization, making the compilation time increase with
                   probably small improvement in execution time.
    
               **max-delay-slot-live-search**
                   When trying to fill delay slots, the maximum number of
                   instructions to consider when searching for a block with
                   valid live register information.  Increasing this
                   arbitrarily chosen value means more aggressive
                   optimization, increasing the compilation time.  This
                   parameter should be removed when the delay slot code is
                   rewritten to maintain the control-flow graph.
    
               **max-gcse-memory**
                   The approximate maximum amount of memory that can be
                   allocated in order to perform the global common
                   subexpression elimination optimization.  If more memory
                   than specified is required, the optimization is not done.
    
               **max-gcse-insertion-ratio**
                   If the ratio of expression insertions to deletions is
                   larger than this value for any expression, then RTL PRE
                   inserts or removes the expression and thus leaves
                   partially redundant computations in the instruction
                   stream.
    
               **max-pending-list-length**
                   The maximum number of pending dependencies scheduling
                   allows before flushing the current state and starting
                   over.  Large functions with few branches or calls can
                   create excessively large lists which needlessly consume
                   memory and resources.
    
               **max-modulo-backtrack-attempts**
                   The maximum number of backtrack attempts the scheduler
                   should make when modulo scheduling a loop.  Larger values
                   can exponentially increase compilation time.
    
               **max-inline-insns-single**
                   Several parameters control the tree inliner used in GCC.
                   This number sets the maximum number of instructions
                   (counted in GCC's internal representation) in a single
                   function that the tree inliner considers for inlining.
                   This only affects functions declared inline and methods
                   implemented in a class declaration (C++).
    
               **max-inline-insns-auto**
                   When you use **-finline-functions**(included in **-O3**), a lot
                   of functions that would otherwise not be considered for
                   inlining by the compiler are investigated.  To those
                   functions, a different (more restrictive) limit compared
                   to functions declared inline can be applied.
    
               **max-inline-insns-small**
                   This is bound applied to calls which are considered
                   relevant with **-finline-small-functions**.
    
               **max-inline-insns-size**
                   This is bound applied to calls which are optimized for
                   size. Small growth may be desirable to anticipate
                   optimization oppurtunities exposed by inlining.
    
               **uninlined-function-insns**
                   Number of instructions accounted by inliner for function
                   overhead such as function prologue and epilogue.
    
               **uninlined-function-time**
                   Extra time accounted by inliner for function overhead such
                   as time needed to execute function prologue and epilogue
    
               **uninlined-thunk-insns**
               **uninlined-thunk-time**
                   Same as **--param uninlined-function-insns** and **--param**
                   **uninlined-function-time** but applied to function thunks
    
               **inline-min-speedup**
                   When estimated performance improvement of caller + callee
                   runtime exceeds this threshold (in percent), the function
                   can be inlined regardless of the limit on **--param max-**
                   **inline-insns-single** and **--param max-inline-insns-auto**.
    
               **large-function-insns**
                   The limit specifying really large functions.  For
                   functions larger than this limit after inlining, inlining
                   is constrained by **--param large-function-growth**.  This
                   parameter is useful primarily to avoid extreme compilation
                   time caused by non-linear algorithms used by the back end.
    
               **large-function-growth**
                   Specifies maximal growth of large function caused by
                   inlining in percents.  For example, parameter value 100
                   limits large function growth to 2.0 times the original
                   size.
    
               **large-unit-insns**
                   The limit specifying large translation unit.  Growth
                   caused by inlining of units larger than this limit is
                   limited by **--param inline-unit-growth**.  For small units
                   this might be too tight.  For example, consider a unit
                   consisting of function A that is inline and B that just
                   calls A three times.  If B is small relative to A, the
                   growth of unit is 300\% and yet such inlining is very
                   sane.  For very large units consisting of small inlineable
                   functions, however, the overall unit growth limit is
                   needed to avoid exponential explosion of code size.  Thus
                   for smaller units, the size is increased to **--param large-**
                   **unit-insns** before applying **--param inline-unit-growth**.
    
               **inline-unit-growth**
                   Specifies maximal overall growth of the compilation unit
                   caused by inlining.  For example, parameter value 20
                   limits unit growth to 1.2 times the original size. Cold
                   functions (either marked cold via an attribute or by
                   profile feedback) are not accounted into the unit size.
    
               **ipcp-unit-growth**
                   Specifies maximal overall growth of the compilation unit
                   caused by interprocedural constant propagation.  For
                   example, parameter value 10 limits unit growth to 1.1
                   times the original size.
    
               **large-stack-frame**
                   The limit specifying large stack frames.  While inlining
                   the algorithm is trying to not grow past this limit too
                   much.
    
               **large-stack-frame-growth**
                   Specifies maximal growth of large stack frames caused by
                   inlining in percents.  For example, parameter value 1000
                   limits large stack frame growth to 11 times the original
                   size.
    
               **max-inline-insns-recursive**
               **max-inline-insns-recursive-auto**
                   Specifies the maximum number of instructions an out-of-
                   line copy of a self-recursive inline function can grow
                   into by performing recursive inlining.
    
                   **--param max-inline-insns-recursive** applies to functions
                   declared inline.  For functions not declared inline,
                   recursive inlining happens only when **-finline-functions**
                   (included in **-O3**) is enabled; **--param max-inline-insns-**
                   **recursive-auto** applies instead.
    
               **max-inline-recursive-depth**
               **max-inline-recursive-depth-auto**
                   Specifies the maximum recursion depth used for recursive
                   inlining.
    
                   **--param max-inline-recursive-depth** applies to functions
                   declared inline.  For functions not declared inline,
                   recursive inlining happens only when **-finline-functions**
                   (included in **-O3**) is enabled; **--param max-inline-**
                   **recursive-depth-auto** applies instead.
    
               **min-inline-recursive-probability**
                   Recursive inlining is profitable only for function having
                   deep recursion in average and can hurt for function having
                   little recursion depth by increasing the prologue size or
                   complexity of function body to other optimizers.
    
                   When profile feedback is available (see
                   **-fprofile-generate**) the actual recursion depth can be
                   guessed from the probability that function recurses via a
                   given call expression.  This parameter limits inlining
                   only to call expressions whose probability exceeds the
                   given threshold (in percents).
    
               **early-inlining-insns**
                   Specify growth that the early inliner can make.  In effect
                   it increases the amount of inlining for code having a
                   large abstraction penalty.
    
               **max-early-inliner-iterations**
                   Limit of iterations of the early inliner.  This basically
                   bounds the number of nested indirect calls the early
                   inliner can resolve.  Deeper chains are still handled by
                   late inlining.
    
               **comdat-sharing-probability**
                   Probability (in percent) that C++ inline function with
                   comdat visibility are shared across multiple compilation
                   units.
    
               **profile-func-internal-id**
                   A parameter to control whether to use function internal id
                   in profile database lookup. If the value is 0, the
                   compiler uses an id that is based on function assembler
                   name and filename, which makes old profile data more
                   tolerant to source changes such as function reordering
                   etc.
    
               **min-vect-loop-bound**
                   The minimum number of iterations under which loops are not
                   vectorized when **-ftree-vectorize** is used.  The number of
                   iterations after vectorization needs to be greater than
                   the value specified by this option to allow vectorization.
    
               **gcse-cost-distance-ratio**
                   Scaling factor in calculation of maximum distance an
                   expression can be moved by GCSE optimizations.  This is
                   currently supported only in the code hoisting pass.  The
                   bigger the ratio, the more aggressive code hoisting is
                   with simple expressions, i.e., the expressions that have
                   cost less than **gcse-unrestricted-cost**.  Specifying 0
                   disables hoisting of simple expressions.
    
               **gcse-unrestricted-cost**
                   Cost, roughly measured as the cost of a single typical
                   machine instruction, at which GCSE optimizations do not
                   constrain the distance an expression can travel.  This is
                   currently supported only in the code hoisting pass.  The
                   lesser the cost, the more aggressive code hoisting is.
                   Specifying 0 allows all expressions to travel unrestricted
                   distances.
    
               **max-hoist-depth**
                   The depth of search in the dominator tree for expressions
                   to hoist.  This is used to avoid quadratic behavior in
                   hoisting algorithm.  The value of 0 does not limit on the
                   search, but may slow down compilation of huge functions.
    
               **max-tail-merge-comparisons**
                   The maximum amount of similar bbs to compare a bb with.
                   This is used to avoid quadratic behavior in tree tail
                   merging.
    
               **max-tail-merge-iterations**
                   The maximum amount of iterations of the pass over the
                   function.  This is used to limit compilation time in tree
                   tail merging.
    
               **store-merging-allow-unaligned**
                   Allow the store merging pass to introduce unaligned stores
                   if it is legal to do so.
    
               **max-stores-to-merge**
                   The maximum number of stores to attempt to merge into
                   wider stores in the store merging pass.
    
               **max-unrolled-insns**
                   The maximum number of instructions that a loop may have to
                   be unrolled.  If a loop is unrolled, this parameter also
                   determines how many times the loop code is unrolled.
    
               **max-average-unrolled-insns**
                   The maximum number of instructions biased by probabilities
                   of their execution that a loop may have to be unrolled.
                   If a loop is unrolled, this parameter also determines how
                   many times the loop code is unrolled.
    
               **max-unroll-times**
                   The maximum number of unrollings of a single loop.
    
               **max-peeled-insns**
                   The maximum number of instructions that a loop may have to
                   be peeled.  If a loop is peeled, this parameter also
                   determines how many times the loop code is peeled.
    
               **max-peel-times**
                   The maximum number of peelings of a single loop.
    
               **max-peel-branches**
                   The maximum number of branches on the hot path through the
                   peeled sequence.
    
               **max-completely-peeled-insns**
                   The maximum number of insns of a completely peeled loop.
    
               **max-completely-peel-times**
                   The maximum number of iterations of a loop to be suitable
                   for complete peeling.
    
               **max-completely-peel-loop-nest-depth**
                   The maximum depth of a loop nest suitable for complete
                   peeling.
    
               **max-unswitch-insns**
                   The maximum number of insns of an unswitched loop.
    
               **max-unswitch-level**
                   The maximum number of branches unswitched in a single
                   loop.
    
               **lim-expensive**
                   The minimum cost of an expensive expression in the loop
                   invariant motion.
    
               **iv-consider-all-candidates-bound**
                   Bound on number of candidates for induction variables,
                   below which all candidates are considered for each use in
                   induction variable optimizations.  If there are more
                   candidates than this, only the most relevant ones are
                   considered to avoid quadratic time complexity.
    
               **iv-max-considered-uses**
                   The induction variable optimizations give up on loops that
                   contain more induction variable uses.
    
               **iv-always-prune-cand-set-bound**
                   If the number of candidates in the set is smaller than
                   this value, always try to remove unnecessary ivs from the
                   set when adding a new one.
    
               **avg-loop-niter**
                   Average number of iterations of a loop.
    
               **dse-max-object-size**
                   Maximum size (in bytes) of objects tracked bytewise by
                   dead store elimination.  Larger values may result in
                   larger compilation times.
    
               **dse-max-alias-queries-per-store**
                   Maximum number of queries into the alias oracle per store.
                   Larger values result in larger compilation times and may
                   result in more removed dead stores.
    
               **scev-max-expr-size**
                   Bound on size of expressions used in the scalar evolutions
                   analyzer.  Large expressions slow the analyzer.
    
               **scev-max-expr-complexity**
                   Bound on the complexity of the expressions in the scalar
                   evolutions analyzer.  Complex expressions slow the
                   analyzer.
    
               **max-tree-if-conversion-phi-args**
                   Maximum number of arguments in a PHI supported by TREE if
                   conversion unless the loop is marked with simd pragma.
    
               **vect-max-version-for-alignment-checks**
                   The maximum number of run-time checks that can be
                   performed when doing loop versioning for alignment in the
                   vectorizer.
    
               **vect-max-version-for-alias-checks**
                   The maximum number of run-time checks that can be
                   performed when doing loop versioning for alias in the
                   vectorizer.
    
               **vect-max-peeling-for-alignment**
                   The maximum number of loop peels to enhance access
                   alignment for vectorizer. Value -1 means no limit.
    
               **max-iterations-to-track**
                   The maximum number of iterations of a loop the brute-force
                   algorithm for analysis of the number of iterations of the
                   loop tries to evaluate.
    
               **hot-bb-count-ws-permille**
                   A basic block profile count is considered hot if it
                   contributes to the given permillage (i.e. 0...1000) of the
                   entire profiled execution.
    
               **hot-bb-frequency-fraction**
                   Select fraction of the entry block frequency of executions
                   of basic block in function given basic block needs to have
                   to be considered hot.
    
               **max-predicted-iterations**
                   The maximum number of loop iterations we predict
                   statically.  This is useful in cases where a function
                   contains a single loop with known bound and another loop
                   with unknown bound.  The known number of iterations is
                   predicted correctly, while the unknown number of
                   iterations average to roughly 10.  This means that the
                   loop without bounds appears artificially cold relative to
                   the other one.
    
               **builtin-expect-probability**
                   Control the probability of the expression having the
                   specified value. This parameter takes a percentage (i.e. 0
                   ... 100) as input.
    
               **builtin-string-cmp-inline-length**
                   The maximum length of a constant string for a builtin
                   string cmp call eligible for inlining.
    
               **align-threshold**
                   Select fraction of the maximal frequency of executions of
                   a basic block in a function to align the basic block.
    
               **align-loop-iterations**
                   A loop expected to iterate at least the selected number of
                   iterations is aligned.
    
               **tracer-dynamic-coverage**
               **tracer-dynamic-coverage-feedback**
                   This value is used to limit superblock formation once the
                   given percentage of executed instructions is covered.
                   This limits unnecessary code size expansion.
    
                   The **tracer-dynamic-coverage-feedback** parameter is used
                   only when profile feedback is available.  The real
                   profiles (as opposed to statically estimated ones) are
                   much less balanced allowing the threshold to be larger
                   value.
    
               **tracer-max-code-growth**
                   Stop tail duplication once code growth has reached given
                   percentage.  This is a rather artificial limit, as most of
                   the duplicates are eliminated later in cross jumping, so
                   it may be set to much higher values than is the desired
                   code growth.
    
               **tracer-min-branch-ratio**
                   Stop reverse growth when the reverse probability of best
                   edge is less than this threshold (in percent).
    
               **tracer-min-branch-probability**
               **tracer-min-branch-probability-feedback**
                   Stop forward growth if the best edge has probability lower
                   than this threshold.
    
                   Similarly to **tracer-dynamic-coverage** two parameters are
                   provided.  **tracer-min-branch-probability-feedback** is used
                   for compilation with profile feedback and **tracer-min-**
                   **branch-probability** compilation without.  The value for
                   compilation with profile feedback needs to be more
                   conservative (higher) in order to make tracer effective.
    
               **stack-clash-protection-guard-size**
                   Specify the size of the operating system provided stack
                   guard as 2 raised to _num_ bytes.  Higher values may reduce
                   the number of explicit probes, but a value larger than the
                   operating system provided guard will leave code vulnerable
                   to stack clash style attacks.
    
               **stack-clash-protection-probe-interval**
                   Stack clash protection involves probing stack space as it
                   is allocated.  This param controls the maximum distance
                   between probes into the stack as 2 raised to _num_ bytes.
                   Higher values may reduce the number of explicit probes,
                   but a value larger than the operating system provided
                   guard will leave code vulnerable to stack clash style
                   attacks.
    
               **max-cse-path-length**
                   The maximum number of basic blocks on path that CSE
                   considers.
    
               **max-cse-insns**
                   The maximum number of instructions CSE processes before
                   flushing.
    
               **ggc-min-expand**
                   GCC uses a garbage collector to manage its own memory
                   allocation.  This parameter specifies the minimum
                   percentage by which the garbage collector's heap should be
                   allowed to expand between collections.  Tuning this may
                   improve compilation speed; it has no effect on code
                   generation.
    
                   The default is 30% + 70% * (RAM/1GB) with an upper bound
                   of 100% when RAM >= 1GB.  If "getrlimit" is available, the
                   notion of "RAM" is the smallest of actual RAM and
                   "RLIMIT_DATA" or "RLIMIT_AS".  If GCC is not able to
                   calculate RAM on a particular platform, the lower bound of
                   30% is used.  Setting this parameter and **ggc-min-heapsize**
                   to zero causes a full collection to occur at every
                   opportunity.  This is extremely slow, but can be useful
                   for debugging.
    
               **ggc-min-heapsize**
                   Minimum size of the garbage collector's heap before it
                   begins bothering to collect garbage.  The first collection
                   occurs after the heap expands by **ggc-min-expand** % beyond
                   **ggc-min-heapsize**.  Again, tuning this may improve
                   compilation speed, and has no effect on code generation.
    
                   The default is the smaller of RAM/8, RLIMIT_RSS, or a
                   limit that tries to ensure that RLIMIT_DATA or RLIMIT_AS
                   are not exceeded, but with a lower bound of 4096 (four
                   megabytes) and an upper bound of 131072 (128 megabytes).
                   If GCC is not able to calculate RAM on a particular
                   platform, the lower bound is used.  Setting this parameter
                   very large effectively disables garbage collection.
                   Setting this parameter and **ggc-min-expand** to zero causes a
                   full collection to occur at every opportunity.
    
               **max-reload-search-insns**
                   The maximum number of instruction reload should look
                   backward for equivalent register.  Increasing values mean
                   more aggressive optimization, making the compilation time
                   increase with probably slightly better performance.
    
               **max-cselib-memory-locations**
                   The maximum number of memory locations cselib should take
                   into account.  Increasing values mean more aggressive
                   optimization, making the compilation time increase with
                   probably slightly better performance.
    
               **max-sched-ready-insns**
                   The maximum number of instructions ready to be issued the
                   scheduler should consider at any given time during the
                   first scheduling pass.  Increasing values mean more
                   thorough searches, making the compilation time increase
                   with probably little benefit.
    
               **max-sched-region-blocks**
                   The maximum number of blocks in a region to be considered
                   for interblock scheduling.
    
               **max-pipeline-region-blocks**
                   The maximum number of blocks in a region to be considered
                   for pipelining in the selective scheduler.
    
               **max-sched-region-insns**
                   The maximum number of insns in a region to be considered
                   for interblock scheduling.
    
               **max-pipeline-region-insns**
                   The maximum number of insns in a region to be considered
                   for pipelining in the selective scheduler.
    
               **min-spec-prob**
                   The minimum probability (in percents) of reaching a source
                   block for interblock speculative scheduling.
    
               **max-sched-extend-regions-iters**
                   The maximum number of iterations through CFG to extend
                   regions.  A value of 0 disables region extensions.
    
               **max-sched-insn-conflict-delay**
                   The maximum conflict delay for an insn to be considered
                   for speculative motion.
    
               **sched-spec-prob-cutoff**
                   The minimal probability of speculation success (in
                   percents), so that speculative insns are scheduled.
    
               **sched-state-edge-prob-cutoff**
                   The minimum probability an edge must have for the
                   scheduler to save its state across it.
    
               **sched-mem-true-dep-cost**
                   Minimal distance (in CPU cycles) between store and load
                   targeting same memory locations.
    
               **selsched-max-lookahead**
                   The maximum size of the lookahead window of selective
                   scheduling.  It is a depth of search for available
                   instructions.
    
               **selsched-max-sched-times**
                   The maximum number of times that an instruction is
                   scheduled during selective scheduling.  This is the limit
                   on the number of iterations through which the instruction
                   may be pipelined.
    
               **selsched-insns-to-rename**
                   The maximum number of best instructions in the ready list
                   that are considered for renaming in the selective
                   scheduler.
    
               **sms-min-sc**
                   The minimum value of stage count that swing modulo
                   scheduler generates.
    
               **max-last-value-rtl**
                   The maximum size measured as number of RTLs that can be
                   recorded in an expression in combiner for a pseudo
                   register as last known value of that register.
    
               **max-combine-insns**
                   The maximum number of instructions the RTL combiner tries
                   to combine.
    
               **integer-share-limit**
                   Small integer constants can use a shared data structure,
                   reducing the compiler's memory usage and increasing its
                   speed.  This sets the maximum value of a shared integer
                   constant.
    
               **ssp-buffer-size**
                   The minimum size of buffers (i.e. arrays) that receive
                   stack smashing protection when **-fstack-protection** is used.
    
               **min-size-for-stack-sharing**
                   The minimum size of variables taking part in stack slot
                   sharing when not optimizing.
    
               **max-jump-thread-duplication-stmts**
                   Maximum number of statements allowed in a block that needs
                   to be duplicated when threading jumps.
    
               **max-fields-for-field-sensitive**
                   Maximum number of fields in a structure treated in a field
                   sensitive manner during pointer analysis.
    
               **prefetch-latency**
                   Estimate on average number of instructions that are
                   executed before prefetch finishes.  The distance
                   prefetched ahead is proportional to this constant.
                   Increasing this number may also lead to less streams being
                   prefetched (see **simultaneous-prefetches**).
    
               **simultaneous-prefetches**
                   Maximum number of prefetches that can run at the same
                   time.
    
               **l1-cache-line-size**
                   The size of cache line in L1 data cache, in bytes.
    
               **l1-cache-size**
                   The size of L1 data cache, in kilobytes.
    
               **l2-cache-size**
                   The size of L2 data cache, in kilobytes.
    
               **prefetch-dynamic-strides**
                   Whether the loop array prefetch pass should issue software
                   prefetch hints for strides that are non-constant.  In some
                   cases this may be beneficial, though the fact the stride
                   is non-constant may make it hard to predict when there is
                   clear benefit to issuing these hints.
    
                   Set to 1 if the prefetch hints should be issued for non-
                   constant strides.  Set to 0 if prefetch hints should be
                   issued only for strides that are known to be constant and
                   below **prefetch-minimum-stride**.
    
               **prefetch-minimum-stride**
                   Minimum constant stride, in bytes, to start using prefetch
                   hints for.  If the stride is less than this threshold,
                   prefetch hints will not be issued.
    
                   This setting is useful for processors that have hardware
                   prefetchers, in which case there may be conflicts between
                   the hardware prefetchers and the software prefetchers.  If
                   the hardware prefetchers have a maximum stride they can
                   handle, it should be used here to improve the use of
                   software prefetchers.
    
                   A value of -1 means we don't have a threshold and
                   therefore prefetch hints can be issued for any constant
                   stride.
    
                   This setting is only useful for strides that are known and
                   constant.
    
               **loop-interchange-max-num-stmts**
                   The maximum number of stmts in a loop to be interchanged.
    
               **loop-interchange-stride-ratio**
                   The minimum ratio between stride of two loops for
                   interchange to be profitable.
    
               **min-insn-to-prefetch-ratio**
                   The minimum ratio between the number of instructions and
                   the number of prefetches to enable prefetching in a loop.
    
               **prefetch-min-insn-to-mem-ratio**
                   The minimum ratio between the number of instructions and
                   the number of memory references to enable prefetching in a
                   loop.
    
               **use-canonical-types**
                   Whether the compiler should use the "canonical" type
                   system.  Should always be 1, which uses a more efficient
                   internal mechanism for comparing types in C++ and
                   Objective-C++.  However, if bugs in the canonical type
                   system are causing compilation failures, set this value to
                   0 to disable canonical types.
    
               **switch-conversion-max-branch-ratio**
                   Switch initialization conversion refuses to create arrays
                   that are bigger than **switch-conversion-max-branch-ratio**
                   times the number of branches in the switch.
    
               **max-partial-antic-length**
                   Maximum length of the partial antic set computed during
                   the tree partial redundancy elimination optimization
                   (**-ftree-pre**) when optimizing at **-O3** and above.  For some
                   sorts of source code the enhanced partial redundancy
                   elimination optimization can run away, consuming all of
                   the memory available on the host machine.  This parameter
                   sets a limit on the length of the sets that are computed,
                   which prevents the runaway behavior.  Setting a value of 0
                   for this parameter allows an unlimited set length.
    
               **rpo-vn-max-loop-depth**
                   Maximum loop depth that is value-numbered optimistically.
                   When the limit hits the innermost _rpo-vn-max-loop-depth_
                   loops and the outermost loop in the loop nest are value-
                   numbered optimistically and the remaining ones not.
    
               **sccvn-max-alias-queries-per-access**
                   Maximum number of alias-oracle queries we perform when
                   looking for redundancies for loads and stores.  If this
                   limit is hit the search is aborted and the load or store
                   is not considered redundant.  The number of queries is
                   algorithmically limited to the number of stores on all
                   paths from the load to the function entry.
    
               **ira-max-loops-num**
                   IRA uses regional register allocation by default.  If a
                   function contains more loops than the number given by this
                   parameter, only at most the given number of the most
                   frequently-executed loops form regions for regional
                   register allocation.
    
               **ira-max-conflict-table-size**
                   Although IRA uses a sophisticated algorithm to compress
                   the conflict table, the table can still require excessive
                   amounts of memory for huge functions.  If the conflict
                   table for a function could be more than the size in MB
                   given by this parameter, the register allocator instead
                   uses a faster, simpler, and lower-quality algorithm that
                   does not require building a pseudo-register conflict
                   table.
    
               **ira-loop-reserved-regs**
                   IRA can be used to evaluate more accurate register
                   pressure in loops for decisions to move loop invariants
                   (see **-O3**).  The number of available registers reserved for
                   some other purposes is given by this parameter.  Default
                   of the parameter is the best found from numerous
                   experiments.
    
               **lra-inheritance-ebb-probability-cutoff**
                   LRA tries to reuse values reloaded in registers in
                   subsequent insns.  This optimization is called
                   inheritance.  EBB is used as a region to do this
                   optimization.  The parameter defines a minimal fall-
                   through edge probability in percentage used to add BB to
                   inheritance EBB in LRA.  The default value was chosen from
                   numerous runs of SPEC2000 on x86-64.
    
               **loop-invariant-max-bbs-in-loop**
                   Loop invariant motion can be very expensive, both in
                   compilation time and in amount of needed compile-time
                   memory, with very large loops.  Loops with more basic
                   blocks than this parameter won't have loop invariant
                   motion optimization performed on them.
    
               **loop-max-datarefs-for-datadeps**
                   Building data dependencies is expensive for very large
                   loops.  This parameter limits the number of data
                   references in loops that are considered for data
                   dependence analysis.  These large loops are no handled by
                   the optimizations using loop data dependencies.
    
               **max-vartrack-size**
                   Sets a maximum number of hash table slots to use during
                   variable tracking dataflow analysis of any function.  If
                   this limit is exceeded with variable tracking at
                   assignments enabled, analysis for that function is retried
                   without it, after removing all debug insns from the
                   function.  If the limit is exceeded even without debug
                   insns, var tracking analysis is completely disabled for
                   the function.  Setting the parameter to zero makes it
                   unlimited.
    
               **max-vartrack-expr-depth**
                   Sets a maximum number of recursion levels when attempting
                   to map variable names or debug temporaries to value
                   expressions.  This trades compilation time for more
                   complete debug information.  If this is set too low, value
                   expressions that are available and could be represented in
                   debug information may end up not being used; setting this
                   higher may enable the compiler to find more complex debug
                   expressions, but compile time and memory use may grow.
    
               **max-debug-marker-count**
                   Sets a threshold on the number of debug markers (e.g.
                   begin stmt markers) to avoid complexity explosion at
                   inlining or expanding to RTL.  If a function has more such
                   gimple stmts than the set limit, such stmts will be
                   dropped from the inlined copy of a function, and from its
                   RTL expansion.
    
               **min-nondebug-insn-uid**
                   Use uids starting at this parameter for nondebug insns.
                   The range below the parameter is reserved exclusively for
                   debug insns created by **-fvar-tracking-assignments** , but
                   debug insns may get (non-overlapping) uids above it if the
                   reserved range is exhausted.
    
               **ipa-sra-ptr-growth-factor**
                   IPA-SRA replaces a pointer to an aggregate with one or
                   more new parameters only when their cumulative size is
                   less or equal to **ipa-sra-ptr-growth-factor** times the size
                   of the original pointer parameter.
    
               **sra-max-scalarization-size-Ospeed**
               **sra-max-scalarization-size-Osize**
                   The two Scalar Reduction of Aggregates passes (SRA and
                   IPA-SRA) aim to replace scalar parts of aggregates with
                   uses of independent scalar variables.  These parameters
                   control the maximum size, in storage units, of aggregate
                   which is considered for replacement when compiling for
                   speed (**sra-max-scalarization-size-Ospeed**) or size (**sra-**
                   **max-scalarization-size-Osize**) respectively.
    
               **sra-max-propagations**
                   The maximum number of artificial accesses that Scalar
                   Replacement of Aggregates (SRA) will track, per one local
                   variable, in order to facilitate copy propagation.
    
               **tm-max-aggregate-size**
                   When making copies of thread-local variables in a
                   transaction, this parameter specifies the size in bytes
                   after which variables are saved with the logging functions
                   as opposed to save/restore code sequence pairs.  This
                   option only applies when using **-fgnu-tm**.
    
               **graphite-max-nb-scop-params**
                   To avoid exponential effects in the Graphite loop
                   transforms, the number of parameters in a Static Control
                   Part (SCoP) is bounded.  A value of zero can be used to
                   lift the bound.  A variable whose value is unknown at
                   compilation time and defined outside a SCoP is a parameter
                   of the SCoP.
    
               **loop-block-tile-size**
                   Loop blocking or strip mining transforms, enabled with
                   **-floop-block** or **-floop-strip-mine** , strip mine each loop in
                   the loop nest by a given number of iterations.  The strip
                   length can be changed using the **loop-block-tile-size**
                   parameter.
    
               **ipa-cp-value-list-size**
                   IPA-CP attempts to track all possible values and types
                   passed to a function's parameter in order to propagate
                   them and perform devirtualization.  **ipa-cp-value-list-size**
                   is the maximum number of values and types it stores per
                   one formal parameter of a function.
    
               **ipa-cp-eval-threshold**
                   IPA-CP calculates its own score of cloning profitability
                   heuristics and performs those cloning opportunities with
                   scores that exceed **ipa-cp-eval-threshold**.
    
               **ipa-cp-recursion-penalty**
                   Percentage penalty the recursive functions will receive
                   when they are evaluated for cloning.
    
               **ipa-cp-single-call-penalty**
                   Percentage penalty functions containing a single call to
                   another function will receive when they are evaluated for
                   cloning.
    
               **ipa-max-agg-items**
                   IPA-CP is also capable to propagate a number of scalar
                   values passed in an aggregate. **ipa-max-agg-items** controls
                   the maximum number of such values per one parameter.
    
               **ipa-cp-loop-hint-bonus**
                   When IPA-CP determines that a cloning candidate would make
                   the number of iterations of a loop known, it adds a bonus
                   of **ipa-cp-loop-hint-bonus** to the profitability score of
                   the candidate.
    
               **ipa-cp-array-index-hint-bonus**
                   When IPA-CP determines that a cloning candidate would make
                   the index of an array access known, it adds a bonus of
                   **ipa-cp-array-index-hint-bonus** to the profitability score
                   of the candidate.
    
               **ipa-max-aa-steps**
                   During its analysis of function bodies, IPA-CP employs
                   alias analysis in order to track values pointed to by
                   function parameters.  In order not spend too much time
                   analyzing huge functions, it gives up and consider all
                   memory clobbered after examining **ipa-max-aa-steps**
                   statements modifying memory.
    
               **lto-partitions**
                   Specify desired number of partitions produced during WHOPR
                   compilation.  The number of partitions should exceed the
                   number of CPUs used for compilation.
    
               **lto-min-partition**
                   Size of minimal partition for WHOPR (in estimated
                   instructions).  This prevents expenses of splitting very
                   small programs into too many partitions.
    
               **lto-max-partition**
                   Size of max partition for WHOPR (in estimated
                   instructions).  to provide an upper bound for individual
                   size of partition.  Meant to be used only with balanced
                   partitioning.
    
               **lto-max-streaming-parallelism**
                   Maximal number of parallel processes used for LTO
                   streaming.
    
               **cxx-max-namespaces-for-diagnostic-help**
                   The maximum number of namespaces to consult for
                   suggestions when C++ name lookup fails for an identifier.
    
               **sink-frequency-threshold**
                   The maximum relative execution frequency (in percents) of
                   the target block relative to a statement's original block
                   to allow statement sinking of a statement.  Larger numbers
                   result in more aggressive statement sinking.  A small
                   positive adjustment is applied for statements with memory
                   operands as those are even more profitable so sink.
    
               **max-stores-to-sink**
                   The maximum number of conditional store pairs that can be
                   sunk.  Set to 0 if either vectorization (**-ftree-vectorize**)
                   or if-conversion (**-ftree-loop-if-convert**) is disabled.
    
               **allow-store-data-races**
                   Allow optimizers to introduce new data races on stores.
                   Set to 1 to allow, otherwise to 0.
    
               **case-values-threshold**
                   The smallest number of different values for which it is
                   best to use a jump-table instead of a tree of conditional
                   branches.  If the value is 0, use the default for the
                   machine.
    
               **tree-reassoc-width**
                   Set the maximum number of instructions executed in
                   parallel in reassociated tree. This parameter overrides
                   target dependent heuristics used by default if has non
                   zero value.
    
               **sched-pressure-algorithm**
                   Choose between the two available implementations of
                   **-fsched-pressure**.  Algorithm 1 is the original
                   implementation and is the more likely to prevent
                   instructions from being reordered.  Algorithm 2 was
                   designed to be a compromise between the relatively
                   conservative approach taken by algorithm 1 and the rather
                   aggressive approach taken by the default scheduler.  It
                   relies more heavily on having a regular register file and
                   accurate register pressure classes.  See _haifa-sched.c_ in
                   the GCC sources for more details.
    
                   The default choice depends on the target.
    
               **max-slsr-cand-scan**
                   Set the maximum number of existing candidates that are
                   considered when seeking a basis for a new straight-line
                   strength reduction candidate.
    
               **asan-globals**
                   Enable buffer overflow detection for global objects.  This
                   kind of protection is enabled by default if you are using
                   **-fsanitize=address** option.  To disable global objects
                   protection use **--param asan-globals=0**.
    
               **asan-stack**
                   Enable buffer overflow detection for stack objects.  This
                   kind of protection is enabled by default when using
                   **-fsanitize=address**.  To disable stack protection use
                   **--param asan-stack=0** option.
    
               **asan-instrument-reads**
                   Enable buffer overflow detection for memory reads.  This
                   kind of protection is enabled by default when using
                   **-fsanitize=address**.  To disable memory reads protection
                   use **--param asan-instrument-reads=0**.
    
               **asan-instrument-writes**
                   Enable buffer overflow detection for memory writes.  This
                   kind of protection is enabled by default when using
                   **-fsanitize=address**.  To disable memory writes protection
                   use **--param asan-instrument-writes=0** option.
    
               **asan-memintrin**
                   Enable detection for built-in functions.  This kind of
                   protection is enabled by default when using
                   **-fsanitize=address**.  To disable built-in functions
                   protection use **--param asan-memintrin=0**.
    
               **asan-use-after-return**
                   Enable detection of use-after-return.  This kind of
                   protection is enabled by default when using the
                   **-fsanitize=address** option.  To disable it use **--param**
                   **asan-use-after-return=0**.
    
                   Note: By default the check is disabled at run time.  To
                   enable it, add "detect_stack_use_after_return=1" to the
                   environment variable **ASAN_OPTIONS**.
    
               **asan-instrumentation-with-call-threshold**
                   If number of memory accesses in function being
                   instrumented is greater or equal to this number, use
                   callbacks instead of inline checks.  E.g. to disable
                   inline code use **--param**
                   **asan-instrumentation-with-call-threshold=0**.
    
               **use-after-scope-direct-emission-threshold**
                   If the size of a local variable in bytes is smaller or
                   equal to this number, directly poison (or unpoison) shadow
                   memory instead of using run-time callbacks.
    
               **max-fsm-thread-path-insns**
                   Maximum number of instructions to copy when duplicating
                   blocks on a finite state automaton jump thread path.
    
               **max-fsm-thread-length**
                   Maximum number of basic blocks on a finite state automaton
                   jump thread path.
    
               **max-fsm-thread-paths**
                   Maximum number of new jump thread paths to create for a
                   finite state automaton.
    
               **parloops-chunk-size**
                   Chunk size of omp schedule for loops parallelized by
                   parloops.
    
               **parloops-schedule**
                   Schedule type of omp schedule for loops parallelized by
                   parloops (static, dynamic, guided, auto, runtime).
    
               **parloops-min-per-thread**
                   The minimum number of iterations per thread of an
                   innermost parallelized loop for which the parallelized
                   variant is preferred over the single threaded one.  Note
                   that for a parallelized loop nest the minimum number of
                   iterations of the outermost loop per thread is two.
    
               **max-ssa-name-query-depth**
                   Maximum depth of recursion when querying properties of SSA
                   names in things like fold routines.  One level of
                   recursion corresponds to following a use-def chain.
    
               **hsa-gen-debug-stores**
                   Enable emission of special debug stores within HSA kernels
                   which are then read and reported by libgomp plugin.
                   Generation of these stores is disabled by default, use
                   **--param hsa-gen-debug-stores=1** to enable it.
    
               **max-speculative-devirt-maydefs**
                   The maximum number of may-defs we analyze when looking for
                   a must-def specifying the dynamic type of an object that
                   invokes a virtual call we may be able to devirtualize
                   speculatively.
    
               **max-vrp-switch-assertions**
                   The maximum number of assertions to add along the default
                   edge of a switch statement during VRP.
    
               **unroll-jam-min-percent**
                   The minimum percentage of memory references that must be
                   optimized away for the unroll-and-jam transformation to be
                   considered profitable.
    
               **unroll-jam-max-unroll**
                   The maximum number of times the outer loop should be
                   unrolled by the unroll-and-jam transformation.
    
               **max-rtl-if-conversion-unpredictable-cost**
                   Maximum permissible cost for the sequence that would be
                   generated by the RTL if-conversion pass for a branch that
                   is considered unpredictable.
    
               **max-variable-expansions-in-unroller**
                   If **-fvariable-expansion-in-unroller** is used, the maximum
                   number of times that an individual variable will be
                   expanded during loop unrolling.
    
               **tracer-min-branch-probability-feedback**
                   Stop forward growth if the probability of best edge is
                   less than this threshold (in percent). Used when profile
                   feedback is available.
    
               **partial-inlining-entry-probability**
                   Maximum probability of the entry BB of split region (in
                   percent relative to entry BB of the function) to make
                   partial inlining happen.
    
               **max-tracked-strlens**
                   Maximum number of strings for which strlen optimization
                   pass will track string lengths.
    
               **gcse-after-reload-partial-fraction**
                   The threshold ratio for performing partial redundancy
                   elimination after reload.
    
               **gcse-after-reload-critical-fraction**
                   The threshold ratio of critical edges execution count that
                   permit performing redundancy elimination after reload.
    
               **max-loop-header-insns**
                   The maximum number of insns in loop header duplicated by
                   the copy loop headers pass.
    
               **vect-epilogues-nomask**
                   Enable loop epilogue vectorization using smaller vector
                   size.
    
               **slp-max-insns-in-bb**
                   Maximum number of instructions in basic block to be
                   considered for SLP vectorization.
    
               **avoid-fma-max-bits**
                   Maximum number of bits for which we avoid creating FMAs.
    
               **sms-loop-average-count-threshold**
                   A threshold on the average loop count considered by the
                   swing modulo scheduler.
    
               **sms-dfa-history**
                   The number of cycles the swing modulo scheduler considers
                   when checking conflicts using DFA.
    
               **hot-bb-count-fraction**
                   Select fraction of the maximal count of repetitions of
                   basic block in program given basic block needs to have to
                   be considered hot (used in non-LTO mode)
    
               **max-inline-insns-recursive-auto**
                   The maximum number of instructions non-inline function can
                   grow to via recursive inlining.
    
               **graphite-allow-codegen-errors**
                   Whether codegen errors should be ICEs when **-fchecking**.
    
               **sms-max-ii-factor**
                   A factor for tuning the upper bound that swing modulo
                   scheduler uses for scheduling a loop.
    
               **lra-max-considered-reload-pseudos**
                   The max number of reload pseudos which are considered
                   during spilling a non-reload pseudo.
    
               **max-pow-sqrt-depth**
                   Maximum depth of sqrt chains to use when synthesizing
                   exponentiation by a real constant.
    
               **max-dse-active-local-stores**
                   Maximum number of active local stores in RTL dead store
                   elimination.
    
               **asan-instrument-allocas**
                   Enable asan allocas/VLAs protection.
    
               **max-iterations-computation-cost**
                   Bound on the cost of an expression to compute the number
                   of iterations.
    
               **max-isl-operations**
                   Maximum number of isl operations, 0 means unlimited.
    
               **graphite-max-arrays-per-scop**
                   Maximum number of arrays per scop.
    
               **max-vartrack-reverse-op-size**
                   Max. size of loc list for which reverse ops should be
                   added.
    
               **unlikely-bb-count-fraction**
                   The minimum fraction of profile runs a given basic block
                   execution count must be not to be considered unlikely.
    
               **tracer-dynamic-coverage-feedback**
                   The percentage of function, weighted by execution
                   frequency, that must be covered by trace formation.  Used
                   when profile feedback is available.
    
               **max-inline-recursive-depth-auto**
                   The maximum depth of recursive inlining for non-inline
                   functions.
    
               **fsm-scale-path-stmts**
                   Scale factor to apply to the number of statements in a
                   threading path when comparing to the number of (scaled)
                   blocks.
    
               **fsm-maximum-phi-arguments**
                   Maximum number of arguments a PHI may have before the FSM
                   threader will not try to thread through its block.
    
               **uninit-control-dep-attempts**
                   Maximum number of nested calls to search for control
                   dependencies during uninitialized variable analysis.
    
               **indir-call-topn-profile**
                   Track top N target addresses in indirect-call profile.
    
               **max-once-peeled-insns**
                   The maximum number of insns of a peeled loop that rolls
                   only once.
    
               **sra-max-scalarization-size-Osize**
                   Maximum size, in storage units, of an aggregate which
                   should be considered for scalarization when compiling for
                   size.
    
               **fsm-scale-path-blocks**
                   Scale factor to apply to the number of blocks in a
                   threading path when comparing to the number of (scaled)
                   statements.
    
               **sched-autopref-queue-depth**
                   Hardware autoprefetcher scheduler model control flag.
                   Number of lookahead cycles the model looks into; at ' '
                   only enable instruction sorting heuristic.
    
               **loop-versioning-max-inner-insns**
                   The maximum number of instructions that an inner loop can
                   have before the loop versioning pass considers it too big
                   to copy.
    
               **loop-versioning-max-outer-insns**
                   The maximum number of instructions that an outer loop can
                   have before the loop versioning pass considers it too big
                   to copy, discounting any instructions in inner loops that
                   directly benefit from versioning.
    
               **ssa-name-def-chain-limit**
                   The maximum number of SSA_NAME assignments to follow in
                   determining a property of a variable such as its value.
                   This limits the number of iterations or recursive calls
                   GCC performs when optimizing certain statements or when
                   determining their validity prior to issuing diagnostics.
    
       **Program Instrumentation Options**
           GCC supports a number of command-line options that control adding
           run-time instrumentation to the code it normally generates.  For
           example, one purpose of instrumentation is collect profiling
           statistics for use in finding program hot spots, code coverage
           analysis, or profile-guided optimizations.  Another class of
           program instrumentation is adding run-time checking to detect
           programming errors like invalid pointer dereferences or out-of-
           bounds array accesses, as well as deliberately hostile attacks
           such as stack smashing or C++ vtable hijacking.  There is also a
           general hook which can be used to implement other forms of tracing
           or function-level instrumentation for debug or program analysis
           purposes.
    
           **-p**
           **-pg** Generate extra code to write profile information suitable for
               the analysis program **prof**(for **-p**) or **gprof**(for **-pg**).  You
               must use this option when compiling the source files you want
               data about, and you must also use it when linking.
    
               You can use the function attribute "no_instrument_function" to
               suppress profiling of individual functions when compiling with
               these options.
    
           **-fprofile-arcs**
               Add code so that program flow _arcs_ are instrumented.  During
               execution the program records how many times each branch and
               call is executed and how many times it is taken or returns.
               On targets that support constructors with priority support,
               profiling properly handles constructors, destructors and C++
               constructors (and destructors) of classes which are used as a
               type of a global variable.
    
               When the compiled program exits it saves this data to a file
               called _auxname.gcda_ for each source file.  The data may be
               used for profile-directed optimizations
               (**-fbranch-probabilities**), or for test coverage analysis
               (**-ftest-coverage**).  Each object file's _auxname_ is generated
               from the name of the output file, if explicitly specified and
               it is not the final executable, otherwise it is the basename
               of the source file.  In both cases any suffix is removed (e.g.
               _foo.gcda_ for input file _dir/foo.c_ , or _dir/foo.gcda_ for output
               file specified as **-o dir/foo.o**).
    
           **--coverage**
               This option is used to compile and link code instrumented for
               coverage analysis.  The option is a synonym for **-fprofile-arcs**
               **-ftest-coverage**(when compiling) and **-lgcov**(when linking).
               See the documentation for those options for more details.
    
               *   Compile the source files with **-fprofile-arcs** plus
                   optimization and code generation options.  For test
                   coverage analysis, use the additional **-ftest-coverage**
                   option.  You do not need to profile every source file in a
                   program.
    
               *   Compile the source files additionally with
                   **-fprofile-abs-path** to create absolute path names in the
                   _.gcno_ files.  This allows **gcov** to find the correct sources
                   in projects where compilations occur with different
                   working directories.
    
               *   Link your object files with **-lgcov** or **-fprofile-arcs**(the
                   latter implies the former).
    
               *   Run the program on a representative workload to generate
                   the arc profile information.  This may be repeated any
                   number of times.  You can run concurrent instances of your
                   program, and provided that the file system supports
                   locking, the data files will be correctly updated.  Unless
                   a strict ISO C dialect option is in effect, "fork" calls
                   are detected and correctly handled without double
                   counting.
    
               *   For profile-directed optimizations, compile the source
                   files again with the same optimization and code generation
                   options plus **-fbranch-probabilities**.
    
               *   For test coverage analysis, use **gcov** to produce human
                   readable information from the _.gcno_ and _.gcda_ files.
                   Refer to the **gcov** documentation for further information.
    
               With **-fprofile-arcs** , for each function of your program GCC
               creates a program flow graph, then finds a spanning tree for
               the graph.  Only arcs that are not on the spanning tree have
               to be instrumented: the compiler adds code to count the number
               of times that these arcs are executed.  When an arc is the
               only exit or only entrance to a block, the instrumentation
               code can be added to the block; otherwise, a new basic block
               must be created to hold the instrumentation code.
    
           **-ftest-coverage**
               Produce a notes file that the **gcov** code-coverage utility can
               use to show program coverage.  Each source file's note file is
               called _auxname.gcno_.  Refer to the **-fprofile-arcs** option above
               for a description of _auxname_ and instructions on how to
               generate test coverage data.  Coverage data matches the source
               files more closely if you do not optimize.
    
           **-fprofile-abs-path**
               Automatically convert relative source file names to absolute
               path names in the _.gcno_ files.  This allows **gcov** to find the
               correct sources in projects where compilations occur with
               different working directories.
    
           **-fprofile-dir=**_path_
               Set the directory to search for the profile data files in to
               _path_.  This option affects only the profile data generated by
               **-fprofile-generate** , **-ftest-coverage** , **-fprofile-arcs** and used
               by **-fprofile-use** and **-fbranch-probabilities** and its related
               options.  Both absolute and relative paths can be used.  By
               default, GCC uses the current directory as _path_ , thus the
               profile data file appears in the same directory as the object
               file.  In order to prevent the file name clashing, if the
               object file name is not an absolute path, we mangle the
               absolute path of the _sourcename.gcda_ file and use it as the
               file name of a _.gcda_ file.
    
               When an executable is run in a massive parallel environment,
               it is recommended to save profile to different folders.  That
               can be done with variables in _path_ that are exported during
               run-time:
    
               **%p** process ID.
    
               **%q{VAR}**
                   value of environment variable _VAR_
    
           **-fprofile-generate**
           **-fprofile-generate=**_path_
               Enable options usually used for instrumenting application to
               produce profile useful for later recompilation with profile
               feedback based optimization.  You must use **-fprofile-generate**
               both when compiling and when linking your program.
    
               The following options are enabled: **-fprofile-arcs** ,
               **-fprofile-values** , **-finline-functions** , and **-fipa-bit-cp**.
    
               If _path_ is specified, GCC looks at the _path_ to find the
               profile feedback data files. See **-fprofile-dir**.
    
               To optimize the program based on the collected profile
               information, use **-fprofile-use**.
    
           **-fprofile-update=**_method_
               Alter the update method for an application instrumented for
               profile feedback based optimization.  The _method_ argument
               should be one of **single** , **atomic** or **prefer-atomic**.  The first
               one is useful for single-threaded applications, while the
               second one prevents profile corruption by emitting thread-safe
               code.
    
               **Warning:** When an application does not properly join all
               threads (or creates an detached thread), a profile file can be
               still corrupted.
    
               Using **prefer-atomic** would be transformed either to **atomic** ,
               when supported by a target, or to **single** otherwise.  The GCC
               driver automatically selects **prefer-atomic** when **-pthread** is
               present in the command line.
    
           **-fprofile-filter-files=**_regex_
               Instrument only functions from files where names match any
               regular expression (separated by a semi-colon).
    
               For example, **-fprofile-filter-files=main.c;module.*.c** will
               instrument only _main.c_ and all C files starting with 'module'.
    
           **-fprofile-exclude-files=**_regex_
               Instrument only functions from files where names do not match
               all the regular expressions (separated by a semi-colon).
    
               For example, **-fprofile-exclude-files=/usr/*** will prevent
               instrumentation of all files that are located in _/usr/_ folder.
    
           **-fsanitize=address**
               Enable AddressSanitizer, a fast memory error detector.  Memory
               access instructions are instrumented to detect out-of-bounds
               and use-after-free bugs.  The option enables
               **-fsanitize-address-use-after-scope**.  See
               <**https://github.com/google/sanitizers/wiki/AddressSanitizer **>
               for more details.  The run-time behavior can be influenced
               using the **ASAN_OPTIONS** environment variable.  When set to
               "help=1", the available options are shown at startup of the
               instrumented program.  See
               <**https://github.com/google/sanitizers/wiki/AddressSanitizerFlags#run-time-flags **>
               for a list of supported options.  The option cannot be
               combined with **-fsanitize=thread**.
    
           **-fsanitize=kernel-address**
               Enable AddressSanitizer for Linux kernel.  See
               <**https://github.com/google/kasan/wiki **> for more details.
    
           **-fsanitize=pointer-compare**
               Instrument comparison operation (<, <=, >, >=) with pointer
               operands.  The option must be combined with either
               **-fsanitize=kernel-address** or **-fsanitize=address** The option
               cannot be combined with **-fsanitize=thread**.  Note: By default
               the check is disabled at run time.  To enable it, add
               "detect_invalid_pointer_pairs=2" to the environment variable
               **ASAN_OPTIONS**. Using "detect_invalid_pointer_pairs=1" detects
               invalid operation only when both pointers are non-null.
    
           **-fsanitize=pointer-subtract**
               Instrument subtraction with pointer operands.  The option must
               be combined with either **-fsanitize=kernel-address** or
               **-fsanitize=address** The option cannot be combined with
               **-fsanitize=thread**.  Note: By default the check is disabled at
               run time.  To enable it, add "detect_invalid_pointer_pairs=2"
               to the environment variable **ASAN_OPTIONS**. Using
               "detect_invalid_pointer_pairs=1" detects invalid operation
               only when both pointers are non-null.
    
           **-fsanitize=thread**
               Enable ThreadSanitizer, a fast data race detector.  Memory
               access instructions are instrumented to detect data race bugs.
               See
               <**https://github.com/google/sanitizers/wiki#threadsanitizer **>
               for more details. The run-time behavior can be influenced
               using the **TSAN_OPTIONS** environment variable; see
               <**https://github.com/google/sanitizers/wiki/ThreadSanitizerFlags **>
               for a list of supported options.  The option cannot be
               combined with **-fsanitize=address** , **-fsanitize=leak**.
    
               Note that sanitized atomic builtins cannot throw exceptions
               when operating on invalid memory addresses with non-call
               exceptions (**-fnon-call-exceptions**).
    
           **-fsanitize=leak**
               Enable LeakSanitizer, a memory leak detector.  This option
               only matters for linking of executables and the executable is
               linked against a library that overrides "malloc" and other
               allocator functions.  See
               <**https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer **>
               for more details.  The run-time behavior can be influenced
               using the **LSAN_OPTIONS** environment variable.  The option
               cannot be combined with **-fsanitize=thread**.
    
           **-fsanitize=undefined**
               Enable UndefinedBehaviorSanitizer, a fast undefined behavior
               detector.  Various computations are instrumented to detect
               undefined behavior at runtime.  See
               <**https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html **>
               for more details.   The run-time behavior can be influenced
               using the **UBSAN_OPTIONS** environment variable.  Current
               suboptions are:
    
               **-fsanitize=shift**
                   This option enables checking that the result of a shift
                   operation is not undefined.  Note that what exactly is
                   considered undefined differs slightly between C and C++,
                   as well as between ISO C90 and C99, etc.  This option has
                   two suboptions, **-fsanitize=shift-base** and
                   **-fsanitize=shift-exponent**.
    
               **-fsanitize=shift-exponent**
                   This option enables checking that the second argument of a
                   shift operation is not negative and is smaller than the
                   precision of the promoted first argument.
    
               **-fsanitize=shift-base**
                   If the second argument of a shift operation is within
                   range, check that the result of a shift operation is not
                   undefined.  Note that what exactly is considered undefined
                   differs slightly between C and C++, as well as between ISO
                   C90 and C99, etc.
    
               **-fsanitize=integer-divide-by-zero**
                   Detect integer division by zero as well as "INT_MIN / -1"
                   division.
    
               **-fsanitize=unreachable**
                   With this option, the compiler turns the
                   "__builtin_unreachable" call into a diagnostics message
                   call instead.  When reaching the "__builtin_unreachable"
                   call, the behavior is undefined.
    
               **-fsanitize=vla-bound**
                   This option instructs the compiler to check that the size
                   of a variable length array is positive.
    
               **-fsanitize=null**
                   This option enables pointer checking.  Particularly, the
                   application built with this option turned on will issue an
                   error message when it tries to dereference a NULL pointer,
                   or if a reference (possibly an rvalue reference) is bound
                   to a NULL pointer, or if a method is invoked on an object
                   pointed by a NULL pointer.
    
               **-fsanitize=return**
                   This option enables return statement checking.  Programs
                   built with this option turned on will issue an error
                   message when the end of a non-void function is reached
                   without actually returning a value.  This option works in
                   C++ only.
    
               **-fsanitize=signed-integer-overflow**
                   This option enables signed integer overflow checking.  We
                   check that the result of "+", "*", and both unary and
                   binary "-" does not overflow in the signed arithmetics.
                   Note, integer promotion rules must be taken into account.
                   That is, the following is not an overflow:
    
                           signed char a = SCHAR_MAX;
                           a++;
    
               **-fsanitize=bounds**
                   This option enables instrumentation of array bounds.
                   Various out of bounds accesses are detected.  Flexible
                   array members, flexible array member-like arrays, and
                   initializers of variables with static storage are not
                   instrumented.
    
               **-fsanitize=bounds-strict**
                   This option enables strict instrumentation of array
                   bounds.  Most out of bounds accesses are detected,
                   including flexible array members and flexible array
                   member-like arrays.  Initializers of variables with static
                   storage are not instrumented.
    
               **-fsanitize=alignment**
                   This option enables checking of alignment of pointers when
                   they are dereferenced, or when a reference is bound to
                   insufficiently aligned target, or when a method or
                   constructor is invoked on insufficiently aligned object.
    
               **-fsanitize=object-size**
                   This option enables instrumentation of memory references
                   using the "__builtin_object_size" function.  Various out
                   of bounds pointer accesses are detected.
    
               **-fsanitize=float-divide-by-zero**
                   Detect floating-point division by zero.  Unlike other
                   similar options, **-fsanitize=float-divide-by-zero** is not
                   enabled by **-fsanitize=undefined** , since floating-point
                   division by zero can be a legitimate way of obtaining
                   infinities and NaNs.
    
               **-fsanitize=float-cast-overflow**
                   This option enables floating-point type to integer
                   conversion checking.  We check that the result of the
                   conversion does not overflow.  Unlike other similar
                   options, **-fsanitize=float-cast-overflow** is not enabled by
                   **-fsanitize=undefined**.  This option does not work well with
                   "FE_INVALID" exceptions enabled.
    
               **-fsanitize=nonnull-attribute**
                   This option enables instrumentation of calls, checking
                   whether null values are not passed to arguments marked as
                   requiring a non-null value by the "nonnull" function
                   attribute.
    
               **-fsanitize=returns-nonnull-attribute**
                   This option enables instrumentation of return statements
                   in functions marked with "returns_nonnull" function
                   attribute, to detect returning of null values from such
                   functions.
    
               **-fsanitize=bool**
                   This option enables instrumentation of loads from bool.
                   If a value other than 0/1 is loaded, a run-time error is
                   issued.
    
               **-fsanitize=enum**
                   This option enables instrumentation of loads from an enum
                   type.  If a value outside the range of values for the enum
                   type is loaded, a run-time error is issued.
    
               **-fsanitize=vptr**
                   This option enables instrumentation of C++ member function
                   calls, member accesses and some conversions between
                   pointers to base and derived classes, to verify the
                   referenced object has the correct dynamic type.
    
               **-fsanitize=pointer-overflow**
                   This option enables instrumentation of pointer
                   arithmetics.  If the pointer arithmetics overflows, a run-
                   time error is issued.
    
               **-fsanitize=builtin**
                   This option enables instrumentation of arguments to
                   selected builtin functions.  If an invalid value is passed
                   to such arguments, a run-time error is issued.  E.g.
                   passing 0 as the argument to "__builtin_ctz" or
                   "__builtin_clz" invokes undefined behavior and is
                   diagnosed by this option.
    
               While **-ftrapv** causes traps for signed overflows to be emitted,
               **-fsanitize=undefined** gives a diagnostic message.  This
               currently works only for the C family of languages.
    
           **-fno-sanitize=all**
               This option disables all previously enabled sanitizers.
               **-fsanitize=all** is not allowed, as some sanitizers cannot be
               used together.
    
           **-fasan-shadow-offset=**_number_
               This option forces GCC to use custom shadow offset in
               AddressSanitizer checks.  It is useful for experimenting with
               different shadow memory layouts in Kernel AddressSanitizer.
    
           **-fsanitize-sections=**_s1_**,**_s2_**,...**
               Sanitize global variables in selected user-defined sections.
               _si_ may contain wildcards.
    
           **-fsanitize-recover**[**=**_opts_]
               **-fsanitize-recover=** controls error recovery mode for
               sanitizers mentioned in comma-separated list of _opts_.
               Enabling this option for a sanitizer component causes it to
               attempt to continue running the program as if no error
               happened.  This means multiple runtime errors can be reported
               in a single program run, and the exit code of the program may
               indicate success even when errors have been reported.  The
               **-fno-sanitize-recover=** option can be used to alter this
               behavior: only the first detected error is reported and
               program then exits with a non-zero exit code.
    
               Currently this feature only works for **-fsanitize=undefined**
               (and its suboptions except for **-fsanitize=unreachable** and
               **-fsanitize=return**), **-fsanitize=float-cast-overflow** ,
               **-fsanitize=float-divide-by-zero** , **-fsanitize=bounds-strict** ,
               **-fsanitize=kernel-address** and **-fsanitize=address**.  For these
               sanitizers error recovery is turned on by default, except
               **-fsanitize=address** , for which this feature is experimental.
               **-fsanitize-recover=all** and **-fno-sanitize-recover=all** is also
               accepted, the former enables recovery for all sanitizers that
               support it, the latter disables recovery for all sanitizers
               that support it.
    
               Even if a recovery mode is turned on the compiler side, it
               needs to be also enabled on the runtime library side,
               otherwise the failures are still fatal.  The runtime library
               defaults to "halt_on_error=0" for ThreadSanitizer and
               UndefinedBehaviorSanitizer, while default value for
               AddressSanitizer is "halt_on_error=1". This can be overridden
               through setting the "halt_on_error" flag in the corresponding
               environment variable.
    
               Syntax without an explicit _opts_ parameter is deprecated.  It
               is equivalent to specifying an _opts_ list of:
    
                       undefined,float-cast-overflow,float-divide-by-zero,bounds-strict
    
           **-fsanitize-address-use-after-scope**
               Enable sanitization of local variables to detect use-after-
               scope bugs.  The option sets **-fstack-reuse** to **none**.
    
           **-fsanitize-undefined-trap-on-error**
               The **-fsanitize-undefined-trap-on-error** option instructs the
               compiler to report undefined behavior using "__builtin_trap"
               rather than a "libubsan" library routine.  The advantage of
               this is that the "libubsan" library is not needed and is not
               linked in, so this is usable even in freestanding
               environments.
    
           **-fsanitize-coverage=trace-pc**
               Enable coverage-guided fuzzing code instrumentation.  Inserts
               a call to "__sanitizer_cov_trace_pc" into every basic block.
    
           **-fsanitize-coverage=trace-cmp**
               Enable dataflow guided fuzzing code instrumentation.  Inserts
               a call to "__sanitizer_cov_trace_cmp1",
               "__sanitizer_cov_trace_cmp2", "__sanitizer_cov_trace_cmp4" or
               "__sanitizer_cov_trace_cmp8" for integral comparison with both
               operands variable or "__sanitizer_cov_trace_const_cmp1",
               "__sanitizer_cov_trace_const_cmp2",
               "__sanitizer_cov_trace_const_cmp4" or
               "__sanitizer_cov_trace_const_cmp8" for integral comparison
               with one operand constant, "__sanitizer_cov_trace_cmpf" or
               "__sanitizer_cov_trace_cmpd" for float or double comparisons
               and "__sanitizer_cov_trace_switch" for switch statements.
    
           **-fcf-protection=**[**full** |**branch** |**return** |**none**]
               Enable code instrumentation of control-flow transfers to
               increase program security by checking that target addresses of
               control-flow transfer instructions (such as indirect function
               call, function return, indirect jump) are valid.  This
               prevents diverting the flow of control to an unexpected
               target.  This is intended to protect against such threats as
               Return-oriented Programming (ROP), and similarly
               call/jmp-oriented programming (COP/JOP).
    
               The value "branch" tells the compiler to implement checking of
               validity of control-flow transfer at the point of indirect
               branch instructions, i.e. call/jmp instructions.  The value
               "return" implements checking of validity at the point of
               returning from a function.  The value "full" is an alias for
               specifying both "branch" and "return". The value "none" turns
               off instrumentation.
    
               The macro "__CET__" is defined when **-fcf-protection** is used.
               The first bit of "__CET__" is set to 1 for the value "branch"
               and the second bit of "__CET__" is set to 1 for the "return".
    
               You can also use the "nocf_check" attribute to identify which
               functions and calls should be skipped from instrumentation.
    
               Currently the x86 GNU/Linux target provides an implementation
               based on Intel Control-flow Enforcement Technology (CET) which
               works for i686 processor or newer.
    
           **-fstack-protector**
               Emit extra code to check for buffer overflows, such as stack
               smashing attacks.  This is done by adding a guard variable to
               functions with vulnerable objects.  This includes functions
               that call "alloca", and functions with buffers larger than 8
               bytes.  The guards are initialized when a function is entered
               and then checked when the function exits.  If a guard check
               fails, an error message is printed and the program exits.
    
           **-fstack-protector-all**
               Like **-fstack-protector** except that all functions are
               protected.
    
           **-fstack-protector-strong**
               Like **-fstack-protector** but includes additional functions to be
               protected --- those that have local array definitions, or have
               references to local frame addresses.
    
           **-fstack-protector-explicit**
               Like **-fstack-protector** but only protects those functions which
               have the "stack_protect" attribute.
    
           **-fstack-check**
               Generate code to verify that you do not go beyond the boundary
               of the stack.  You should specify this flag if you are running
               in an environment with multiple threads, but you only rarely
               need to specify it in a single-threaded environment since
               stack overflow is automatically detected on nearly all systems
               if there is only one stack.
    
               Note that this switch does not actually cause checking to be
               done; the operating system or the language runtime must do
               that.  The switch causes generation of code to ensure that
               they see the stack being extended.
    
               You can additionally specify a string parameter: **no** means no
               checking, **generic** means force the use of old-style checking,
               **specific** means use the best checking method and is equivalent
               to bare **-fstack-check**.
    
               Old-style checking is a generic mechanism that requires no
               specific target support in the compiler but comes with the
               following drawbacks:
    
               1.  Modified allocation strategy for large objects: they are
                   always allocated dynamically if their size exceeds a fixed
                   threshold.  Note this may change the semantics of some
                   code.
    
               2.  Fixed limit on the size of the static frame of functions:
                   when it is topped by a particular function, stack checking
                   is not reliable and a warning is issued by the compiler.
    
               3.  Inefficiency: because of both the modified allocation
                   strategy and the generic implementation, code performance
                   is hampered.
    
               Note that old-style stack checking is also the fallback method
               for **specific** if no target support has been added in the
               compiler.
    
               **-fstack-check=** is designed for Ada's needs to detect infinite
               recursion and stack overflows.  **specific** is an excellent
               choice when compiling Ada code.  It is not generally
               sufficient to protect against stack-clash attacks.  To protect
               against those you want **-fstack-clash-protection**.
    
           **-fstack-clash-protection**
               Generate code to prevent stack clash style attacks.  When this
               option is enabled, the compiler will only allocate one page of
               stack space at a time and each page is accessed immediately
               after allocation.  Thus, it prevents allocations from jumping
               over any stack guard page provided by the operating system.
    
               Most targets do not fully support stack clash protection.
               However, on those targets **-fstack-clash-protection** will
               protect dynamic stack allocations.  **-fstack-clash-protection**
               may also provide limited protection for static stack
               allocations if the target supports **-fstack-check=specific**.
    
           **-fstack-limit-register=**_reg_
           **-fstack-limit-symbol=**_sym_
           **-fno-stack-limit**
               Generate code to ensure that the stack does not grow beyond a
               certain value, either the value of a register or the address
               of a symbol.  If a larger stack is required, a signal is
               raised at run time.  For most targets, the signal is raised
               before the stack overruns the boundary, so it is possible to
               catch the signal without taking special precautions.
    
               For instance, if the stack starts at absolute address
               **0x80000000** and grows downwards, you can use the flags
               **-fstack-limit-symbol=__stack_limit** and
               **-Wl,--defsym,__stack_limit=0x7ffe0000** to enforce a stack limit
               of 128KB.  Note that this may only work with the GNU linker.
    
               You can locally override stack limit checking by using the
               "no_stack_limit" function attribute.
    
           **-fsplit-stack**
               Generate code to automatically split the stack before it
               overflows.  The resulting program has a discontiguous stack
               which can only overflow if the program is unable to allocate
               any more memory.  This is most useful when running threaded
               programs, as it is no longer necessary to calculate a good
               stack size to use for each thread.  This is currently only
               implemented for the x86 targets running GNU/Linux.
    
               When code compiled with **-fsplit-stack** calls code compiled
               without **-fsplit-stack** , there may not be much stack space
               available for the latter code to run.  If compiling all code,
               including library code, with **-fsplit-stack** is not an option,
               then the linker can fix up these calls so that the code
               compiled without **-fsplit-stack** always has a large stack.
               Support for this is implemented in the gold linker in GNU
               binutils release 2.21 and later.
    
           **-fvtable-verify=**[**std** |**preinit** |**none**]
               This option is only available when compiling C++ code.  It
               turns on (or off, if using **-fvtable-verify=none**) the security
               feature that verifies at run time, for every virtual call,
               that the vtable pointer through which the call is made is
               valid for the type of the object, and has not been corrupted
               or overwritten.  If an invalid vtable pointer is detected at
               run time, an error is reported and execution of the program is
               immediately halted.
    
               This option causes run-time data structures to be built at
               program startup, which are used for verifying the vtable
               pointers.  The options **std** and **preinit** control the timing of
               when these data structures are built.  In both cases the data
               structures are built before execution reaches "main".  Using
               **-fvtable-verify=std** causes the data structures to be built
               after shared libraries have been loaded and initialized.
               **-fvtable-verify=preinit** causes them to be built before shared
               libraries have been loaded and initialized.
    
               If this option appears multiple times in the command line with
               different values specified, **none** takes highest priority over
               both **std** and **preinit** ; **preinit** takes priority over **std**.
    
           **-fvtv-debug**
               When used in conjunction with **-fvtable-verify=std** or
               **-fvtable-verify=preinit** , causes debug versions of the runtime
               functions for the vtable verification feature to be called.
               This flag also causes the compiler to log information about
               which vtable pointers it finds for each class.  This
               information is written to a file named _vtv_set_ptr_data.log_ in
               the directory named by the environment variable **VTV_LOGS_DIR**
               if that is defined or the current working directory otherwise.
    
               Note:  This feature _appends_ data to the log file. If you want
               a fresh log file, be sure to delete any existing one.
    
           **-fvtv-counts**
               This is a debugging flag.  When used in conjunction with
               **-fvtable-verify=std** or **-fvtable-verify=preinit** , this causes
               the compiler to keep track of the total number of virtual
               calls it encounters and the number of verifications it
               inserts.  It also counts the number of calls to certain run-
               time library functions that it inserts and logs this
               information for each compilation unit.  The compiler writes
               this information to a file named _vtv_count_data.log_ in the
               directory named by the environment variable **VTV_LOGS_DIR** if
               that is defined or the current working directory otherwise.
               It also counts the size of the vtable pointer sets for each
               class, and writes this information to _vtv_class_set_sizes.log_
               in the same directory.
    
               Note:  This feature _appends_ data to the log files.  To get
               fresh log files, be sure to delete any existing ones.
    
           **-finstrument-functions**
               Generate instrumentation calls for entry and exit to
               functions.  Just after function entry and just before function
               exit, the following profiling functions are called with the
               address of the current function and its call site.  (On some
               platforms, "__builtin_return_address" does not work beyond the
               current function, so the call site information may not be
               available to the profiling functions otherwise.)
    
                       void __cyg_profile_func_enter (void *this_fn,
                                                      void *call_site);
                       void __cyg_profile_func_exit  (void *this_fn,
                                                      void *call_site);
    
               The first argument is the address of the start of the current
               function, which may be looked up exactly in the symbol table.
    
               This instrumentation is also done for functions expanded
               inline in other functions.  The profiling calls indicate
               where, conceptually, the inline function is entered and
               exited.  This means that addressable versions of such
               functions must be available.  If all your uses of a function
               are expanded inline, this may mean an additional expansion of
               code size.  If you use "extern inline" in your C code, an
               addressable version of such functions must be provided.  (This
               is normally the case anyway, but if you get lucky and the
               optimizer always expands the functions inline, you might have
               gotten away without providing static copies.)
    
               A function may be given the attribute
               "no_instrument_function", in which case this instrumentation
               is not done.  This can be used, for example, for the profiling
               functions listed above, high-priority interrupt routines, and
               any functions from which the profiling functions cannot safely
               be called (perhaps signal handlers, if the profiling routines
               generate output or allocate memory).
    
           **-finstrument-functions-exclude-file-list=**_file_**,**_file_**,...**
               Set the list of functions that are excluded from
               instrumentation (see the description of
               **-finstrument-functions**).  If the file that contains a function
               definition matches with one of _file_ , then that function is not
               instrumented.  The match is done on substrings: if the _file_
               parameter is a substring of the file name, it is considered to
               be a match.
    
               For example:
    
                       -finstrument-functions-exclude-file-list=/bits/stl,include/sys
    
               excludes any inline function defined in files whose pathnames
               contain _/bits/stl_ or _include/sys_.
    
               If, for some reason, you want to include letter **,** in one of
               _sym_ , write **,**. For example,
               **-finstrument-functions-exclude-file-list=',,tmp'**(note the
               single quote surrounding the option).
    
           **-finstrument-functions-exclude-function-list=**_sym_**,**_sym_**,...**
               This is similar to **-finstrument-functions-exclude-file-list** ,
               but this option sets the list of function names to be excluded
               from instrumentation.  The function name to be matched is its
               user-visible name, such as "vector<int> blah(const vector<int>
               &)", not the internal mangled name (e.g.,
               "_Z4blahRSt6vectorIiSaIiEE").  The match is done on
               substrings: if the _sym_ parameter is a substring of the
               function name, it is considered to be a match.  For C99 and
               C++ extended identifiers, the function name must be given in
               UTF-8, not using universal character names.
    
           **-fpatchable-function-entry=**_N_**[,**_M_**]**
               Generate _N_ NOPs right at the beginning of each function, with
               the function entry point before the _M_ th NOP.  If _M_ is omitted,
               it defaults to 0 so the function entry points to the address
               just at the first NOP.  The NOP instructions reserve extra
               space which can be used to patch in any desired
               instrumentation at run time, provided that the code segment is
               writable.  The amount of space is controllable indirectly via
               the number of NOPs; the NOP instruction used corresponds to
               the instruction emitted by the internal GCC back-end interface
               "gen_nop".  This behavior is target-specific and may also
               depend on the architecture variant and/or other compilation
               options.
    
               For run-time identification, the starting addresses of these
               areas, which correspond to their respective function entries
               minus _M_ , are additionally collected in the
               "__patchable_function_entries" section of the resulting
               binary.
    
               Note that the value of "__attribute__
               ((patchable_function_entry (N,M)))" takes precedence over
               command-line option **-fpatchable-function-entry=N,M**.  This can
               be used to increase the area size or to remove it completely
               on a single function.  If "N=0", no pad location is recorded.
    
               The NOP instructions are inserted at---and maybe before,
               depending on _M_ ---the function entry address, even before the
               prologue.
    
       **Options Controlling the Preprocessor**
           These options control the C preprocessor, which is run on each C
           source file before actual compilation.
    
           If you use the **-E** option, nothing is done except preprocessing.
           Some of these options make sense only together with **-E** because
           they cause the preprocessor output to be unsuitable for actual
           compilation.
    
           In addition to the options listed here, there are a number of
           options to control search paths for include files documented in
           **Directory Options**.  Options to control preprocessor diagnostics
           are listed in **Warning Options**.
    
           **-D** _name_
               Predefine _name_ as a macro, with definition 1.
    
           **-D** _name_**=**_definition_
               The contents of _definition_ are tokenized and processed as if
               they appeared during translation phase three in a **#define**
               directive.  In particular, the definition is truncated by
               embedded newline characters.
    
               If you are invoking the preprocessor from a shell or shell-
               like program you may need to use the shell's quoting syntax to
               protect characters such as spaces that have a meaning in the
               shell syntax.
    
               If you wish to define a function-like macro on the command
               line, write its argument list with surrounding parentheses
               before the equals sign (if any).  Parentheses are meaningful
               to most shells, so you should quote the option.  With **sh** and
               **csh** , **-D'**_name_**(**_args..._**)=**_definition_**'** works.
    
               **-D** and **-U** options are processed in the order they are given on
               the command line.  All **-imacros** _file_ and **-include** _file_ options
               are processed after all **-D** and **-U** options.
    
           **-U** _name_
               Cancel any previous definition of _name_ , either built in or
               provided with a **-D** option.
    
           **-include** _file_
               Process _file_ as if "#include "file"" appeared as the first
               line of the primary source file.  However, the first directory
               searched for _file_ is the preprocessor's working directory
               _instead of_ the directory containing the main source file.  If
               not found there, it is searched for in the remainder of the
               "#include "..."" search chain as normal.
    
               If multiple **-include** options are given, the files are included
               in the order they appear on the command line.
    
           **-imacros** _file_
               Exactly like **-include** , except that any output produced by
               scanning _file_ is thrown away.  Macros it defines remain
               defined.  This allows you to acquire all the macros from a
               header without also processing its declarations.
    
               All files specified by **-imacros** are processed before all files
               specified by **-include**.
    
           **-undef**
               Do not predefine any system-specific or GCC-specific macros.
               The standard predefined macros remain defined.
    
           **-pthread**
               Define additional macros required for using the POSIX threads
               library.  You should use this option consistently for both
               compilation and linking.  This option is supported on
               GNU/Linux targets, most other Unix derivatives, and also on
               x86 Cygwin and MinGW targets.
    
           **-M** Instead of outputting the result of preprocessing, output a
               rule suitable for **make** describing the dependencies of the main
               source file.  The preprocessor outputs one **make** rule
               containing the object file name for that source file, a colon,
               and the names of all the included files, including those
               coming from **-include** or **-imacros** command-line options.
    
               Unless specified explicitly (with **-MT** or **-MQ**), the object file
               name consists of the name of the source file with any suffix
               replaced with object file suffix and with any leading
               directory parts removed.  If there are many included files
               then the rule is split into several lines using **\** -newline.
               The rule has no commands.
    
               This option does not suppress the preprocessor's debug output,
               such as **-dM**.  To avoid mixing such debug output with the
               dependency rules you should explicitly specify the dependency
               output file with **-MF** , or use an environment variable like
               **DEPENDENCIES_OUTPUT**.  Debug output is still sent to the
               regular output stream as normal.
    
               Passing **-M** to the driver implies **-E** , and suppresses warnings
               with an implicit **-w**.
    
           **-MM** Like **-M** but do not mention header files that are found in
               system header directories, nor header files that are included,
               directly or indirectly, from such a header.
    
               This implies that the choice of angle brackets or double
               quotes in an **#include** directive does not in itself determine
               whether that header appears in **-MM** dependency output.
    
           **-MF** _file_
               When used with **-M** or **-MM** , specifies a file to write the
               dependencies to.  If no **-MF** switch is given the preprocessor
               sends the rules to the same place it would send preprocessed
               output.
    
               When used with the driver options **-MD** or **-MMD** , **-MF** overrides
               the default dependency output file.
    
               If _file_ is _-_ , then the dependencies are written to _stdout_.
    
           **-MG** In conjunction with an option such as **-M** requesting dependency
               generation, **-MG** assumes missing header files are generated
               files and adds them to the dependency list without raising an
               error.  The dependency filename is taken directly from the
               "#include" directive without prepending any path.  **-MG** also
               suppresses preprocessed output, as a missing header file
               renders this useless.
    
               This feature is used in automatic updating of makefiles.
    
           **-MP** This option instructs CPP to add a phony target for each
               dependency other than the main file, causing each to depend on
               nothing.  These dummy rules work around errors **make** gives if
               you remove header files without updating the _Makefile_ to
               match.
    
               This is typical output:
    
                       test.o: test.c test.h
    
                       test.h:
    
           **-MT** _target_
               Change the target of the rule emitted by dependency
               generation.  By default CPP takes the name of the main input
               file, deletes any directory components and any file suffix
               such as **.c** , and appends the platform's usual object suffix.
               The result is the target.
    
               An **-MT** option sets the target to be exactly the string you
               specify.  If you want multiple targets, you can specify them
               as a single argument to **-MT** , or use multiple **-MT** options.
    
               For example, **-MT '$(objpfx)foo.o'** might give
    
                       $(objpfx)foo.o: foo.c
    
           **-MQ** _target_
               Same as **-MT** , but it quotes any characters which are special to
               Make.  **-MQ '$(objpfx)foo.o'** gives
    
                       $$(objpfx)foo.o: foo.c
    
               The default target is automatically quoted, as if it were
               given with **-MQ**.
    
           **-MD -MD** is equivalent to **-M -MF** _file_ , except that **-E** is not
               implied.  The driver determines _file_ based on whether an **-o**
               option is given.  If it is, the driver uses its argument but
               with a suffix of _.d_ , otherwise it takes the name of the input
               file, removes any directory components and suffix, and applies
               a _.d_ suffix.
    
               If **-MD** is used in conjunction with **-E** , any **-o** switch is
               understood to specify the dependency output file, but if used
               without **-E** , each **-o** is understood to specify a target object
               file.
    
               Since **-E** is not implied, **-MD** can be used to generate a
               dependency output file as a side effect of the compilation
               process.
    
           **-MMD**
               Like **-MD** except mention only user header files, not system
               header files.
    
           **-fpreprocessed**
               Indicate to the preprocessor that the input file has already
               been preprocessed.  This suppresses things like macro
               expansion, trigraph conversion, escaped newline splicing, and
               processing of most directives.  The preprocessor still
               recognizes and removes comments, so that you can pass a file
               preprocessed with **-C** to the compiler without problems.  In
               this mode the integrated preprocessor is little more than a
               tokenizer for the front ends.
    
               **-fpreprocessed** is implicit if the input file has one of the
               extensions **.i** , **.ii** or **.mi**.  These are the extensions that GCC
               uses for preprocessed files created by **-save-temps**.
    
           **-fdirectives-only**
               When preprocessing, handle directives, but do not expand
               macros.
    
               The option's behavior depends on the **-E** and **-fpreprocessed**
               options.
    
               With **-E** , preprocessing is limited to the handling of
               directives such as "#define", "#ifdef", and "#error".  Other
               preprocessor operations, such as macro expansion and trigraph
               conversion are not performed.  In addition, the **-dD** option is
               implicitly enabled.
    
               With **-fpreprocessed** , predefinition of command line and most
               builtin macros is disabled.  Macros such as "__LINE__", which
               are contextually dependent, are handled normally.  This
               enables compilation of files previously preprocessed with "-E
               -fdirectives-only".
    
               With both **-E** and **-fpreprocessed** , the rules for **-fpreprocessed**
               take precedence.  This enables full preprocessing of files
               previously preprocessed with "-E -fdirectives-only".
    
           **-fdollars-in-identifiers**
               Accept **$** in identifiers.
    
           **-fextended-identifiers**
               Accept universal character names in identifiers.  This option
               is enabled by default for C99 (and later C standard versions)
               and C++.
    
           **-fno-canonical-system-headers**
               When preprocessing, do not shorten system header paths with
               canonicalization.
    
           **-ftabstop=**_width_
               Set the distance between tab stops.  This helps the
               preprocessor report correct column numbers in warnings or
               errors, even if tabs appear on the line.  If the value is less
               than 1 or greater than 100, the option is ignored.  The
               default is 8.
    
           **-ftrack-macro-expansion**[**=**_level_]
               Track locations of tokens across macro expansions. This allows
               the compiler to emit diagnostic about the current macro
               expansion stack when a compilation error occurs in a macro
               expansion. Using this option makes the preprocessor and the
               compiler consume more memory. The _level_ parameter can be used
               to choose the level of precision of token location tracking
               thus decreasing the memory consumption if necessary. Value **0**
               of _level_ de-activates this option. Value **1** tracks tokens
               locations in a degraded mode for the sake of minimal memory
               overhead. In this mode all tokens resulting from the expansion
               of an argument of a function-like macro have the same
               location. Value **2** tracks tokens locations completely. This
               value is the most memory hungry.  When this option is given no
               argument, the default parameter value is **2**.
    
               Note that "-ftrack-macro-expansion=2" is activated by default.
    
           **-fmacro-prefix-map=**_old_**=**_new_
               When preprocessing files residing in directory _old_ , expand the
               "__FILE__" and "__BASE_FILE__" macros as if the files resided
               in directory _new_ instead.  This can be used to change an
               absolute path to a relative path by using _._ for _new_ which can
               result in more reproducible builds that are location
               independent.  This option also affects "__builtin_FILE()"
               during compilation.  See also **-ffile-prefix-map**.
    
           **-fexec-charset=**_charset_
               Set the execution character set, used for string and character
               constants.  The default is UTF-8.  _charset_ can be any encoding
               supported by the system's "iconv" library routine.
    
           **-fwide-exec-charset=**_charset_
               Set the wide execution character set, used for wide string and
               character constants.  The default is UTF-32 or UTF-16,
               whichever corresponds to the width of "wchar_t".  As with
               **-fexec-charset** , _charset_ can be any encoding supported by the
               system's "iconv" library routine; however, you will have
               problems with encodings that do not fit exactly in "wchar_t".
    
           **-finput-charset=**_charset_
               Set the input character set, used for translation from the
               character set of the input file to the source character set
               used by GCC.  If the locale does not specify, or GCC cannot
               get this information from the locale, the default is UTF-8.
               This can be overridden by either the locale or this command-
               line option.  Currently the command-line option takes
               precedence if there's a conflict.  _charset_ can be any encoding
               supported by the system's "iconv" library routine.
    
           **-fpch-deps**
               When using precompiled headers, this flag causes the
               dependency-output flags to also list the files from the
               precompiled header's dependencies.  If not specified, only the
               precompiled header are listed and not the files that were used
               to create it, because those files are not consulted when a
               precompiled header is used.
    
           **-fpch-preprocess**
               This option allows use of a precompiled header together with
               **-E**.  It inserts a special "#pragma", "#pragma GCC
               pch_preprocess "_filename""_ in the output to mark the place
               where the precompiled header was found, and its _filename_.
               When **-fpreprocessed** is in use, GCC recognizes this "#pragma"
               and loads the PCH.
    
               This option is off by default, because the resulting
               preprocessed output is only really suitable as input to GCC.
               It is switched on by **-save-temps**.
    
               You should not write this "#pragma" in your own code, but it
               is safe to edit the filename if the PCH file is available in a
               different location.  The filename may be absolute or it may be
               relative to GCC's current directory.
    
           **-fworking-directory**
               Enable generation of linemarkers in the preprocessor output
               that let the compiler know the current working directory at
               the time of preprocessing.  When this option is enabled, the
               preprocessor emits, after the initial linemarker, a second
               linemarker with the current working directory followed by two
               slashes.  GCC uses this directory, when it's present in the
               preprocessed input, as the directory emitted as the current
               working directory in some debugging information formats.  This
               option is implicitly enabled if debugging information is
               enabled, but this can be inhibited with the negated form
               **-fno-working-directory**.  If the **-P** flag is present in the
               command line, this option has no effect, since no "#line"
               directives are emitted whatsoever.
    
           **-A** _predicate_**=**_answer_
               Make an assertion with the predicate _predicate_ and answer
               _answer_.  This form is preferred to the older form **-A**
               _predicate_**(**_answer_**)** , which is still supported, because it does
               not use shell special characters.
    
           **-A -**_predicate_**=**_answer_
               Cancel an assertion with the predicate _predicate_ and answer
               _answer_.
    
           **-C** Do not discard comments.  All comments are passed through to
               the output file, except for comments in processed directives,
               which are deleted along with the directive.
    
               You should be prepared for side effects when using **-C** ; it
               causes the preprocessor to treat comments as tokens in their
               own right.  For example, comments appearing at the start of
               what would be a directive line have the effect of turning that
               line into an ordinary source line, since the first token on
               the line is no longer a **#**.
    
           **-CC** Do not discard comments, including during macro expansion.
               This is like **-C** , except that comments contained within macros
               are also passed through to the output file where the macro is
               expanded.
    
               In addition to the side effects of the **-C** option, the **-CC**
               option causes all C++-style comments inside a macro to be
               converted to C-style comments.  This is to prevent later use
               of that macro from inadvertently commenting out the remainder
               of the source line.
    
               The **-CC** option is generally used to support lint comments.
    
           **-P** Inhibit generation of linemarkers in the output from the
               preprocessor.  This might be useful when running the
               preprocessor on something that is not C code, and will be sent
               to a program which might be confused by the linemarkers.
    
           **-traditional**
           **-traditional-cpp**
               Try to imitate the behavior of pre-standard C preprocessors,
               as opposed to ISO C preprocessors.  See the GNU CPP manual for
               details.
    
               Note that GCC does not otherwise attempt to emulate a pre-
               standard C compiler, and these options are only supported with
               the **-E** switch, or when invoking CPP explicitly.
    
           **-trigraphs**
               Support ISO C trigraphs.  These are three-character sequences,
               all starting with **??** , that are defined by ISO C to stand for
               single characters.  For example, **??/** stands for **\** , so **'??/n'**
               is a character constant for a newline.
    
               The nine trigraphs and their replacements are
    
                       Trigraph:       ??(  ??)  ??<  ??>  ??=  ??/  ??'  ??!  ??-
                       Replacement:      [    ]    {    }    #    \    ^    |    ~
    
               By default, GCC ignores trigraphs, but in standard-conforming
               modes it converts them.  See the **-std** and **-ansi** options.
    
           **-remap**
               Enable special code to work around file systems which only
               permit very short file names, such as MS-DOS.
    
           **-H** Print the name of each header file used, in addition to other
               normal activities.  Each name is indented to show how deep in
               the **#include** stack it is.  Precompiled header files are also
               printed, even if they are found to be invalid; an invalid
               precompiled header file is printed with **...x** and a valid one
               with **...!**.
    
           **-d** _letters_
               Says to make debugging dumps during compilation as specified
               by _letters_.  The flags documented here are those relevant to
               the preprocessor.  Other _letters_ are interpreted by the
               compiler proper, or reserved for future versions of GCC, and
               so are silently ignored.  If you specify _letters_ whose
               behavior conflicts, the result is undefined.
    
               **-dM** Instead of the normal output, generate a list of **#define**
                   directives for all the macros defined during the execution
                   of the preprocessor, including predefined macros.  This
                   gives you a way of finding out what is predefined in your
                   version of the preprocessor.  Assuming you have no file
                   _foo.h_ , the command
    
                           touch foo.h; cpp -dM foo.h
    
                   shows all the predefined macros.
    
                   If you use **-dM** without the **-E** option, **-dM** is interpreted
                   as a synonym for **-fdump-rtl-mach**.
    
               **-dD** Like **-dM** except in two respects: it does _not_ include the
                   predefined macros, and it outputs _both_ the **#define**
                   directives and the result of preprocessing.  Both kinds of
                   output go to the standard output file.
    
               **-dN** Like **-dD** , but emit only the macro names, not their
                   expansions.
    
               **-dI** Output **#include** directives in addition to the result of
                   preprocessing.
    
               **-dU** Like **-dD** except that only macros that are expanded, or
                   whose definedness is tested in preprocessor directives,
                   are output; the output is delayed until the use or test of
                   the macro; and **#undef** directives are also output for
                   macros tested but undefined at the time.
    
           **-fdebug-cpp**
               This option is only useful for debugging GCC.  When used from
               CPP or with **-E** , it dumps debugging information about location
               maps.  Every token in the output is preceded by the dump of
               the map its location belongs to.
    
               When used from GCC without **-E** , this option has no effect.
    
           **-Wp,**_option_
               You can use **-Wp,**_option_ to bypass the compiler driver and pass
               _option_ directly through to the preprocessor.  If _option_
               contains commas, it is split into multiple options at the
               commas.  However, many options are modified, translated or
               interpreted by the compiler driver before being passed to the
               preprocessor, and **-Wp** forcibly bypasses this phase.  The
               preprocessor's direct interface is undocumented and subject to
               change, so whenever possible you should avoid using **-Wp** and
               let the driver handle the options instead.
    
           **-Xpreprocessor** _option_
               Pass _option_ as an option to the preprocessor.  You can use
               this to supply system-specific preprocessor options that GCC
               does not recognize.
    
               If you want to pass an option that takes an argument, you must
               use **-Xpreprocessor** twice, once for the option and once for the
               argument.
    
           **-no-integrated-cpp**
               Perform preprocessing as a separate pass before compilation.
               By default, GCC performs preprocessing as an integrated part
               of input tokenization and parsing.  If this option is
               provided, the appropriate language front end (**cc1** , **cc1plus** , or
               **cc1obj** for C, C++, and Objective-C, respectively) is instead
               invoked twice, once for preprocessing only and once for actual
               compilation of the preprocessed input.  This option may be
               useful in conjunction with the **-B** or **-wrapper** options to
               specify an alternate preprocessor or perform additional
               processing of the program source between normal preprocessing
               and compilation.
    
       **Passing Options to the Assembler**
           You can pass options to the assembler.
    
           **-Wa,**_option_
               Pass _option_ as an option to the assembler.  If _option_ contains
               commas, it is split into multiple options at the commas.
    
           **-Xassembler** _option_
               Pass _option_ as an option to the assembler.  You can use this
               to supply system-specific assembler options that GCC does not
               recognize.
    
               If you want to pass an option that takes an argument, you must
               use **-Xassembler** twice, once for the option and once for the
               argument.
    
       **Options for Linking**
           These options come into play when the compiler links object files
           into an executable output file.  They are meaningless if the
           compiler is not doing a link step.
    
           _object-file-name_
               A file name that does not end in a special recognized suffix
               is considered to name an object file or library.  (Object
               files are distinguished from libraries by the linker according
               to the file contents.)  If linking is done, these object files
               are used as input to the linker.
    
           **-c**
           **-S**
           **-E** If any of these options is used, then the linker is not run,
               and object file names should not be used as arguments.
    
           **-flinker-output=**_type_
               This option controls the code generation of the link time
               optimizer.  By default the linker output is determined by the
               linker plugin automatically. For debugging the compiler and in
               the case of incremental linking to non-lto object file is
               desired, it may be useful to control the type manually.
    
               If _type_ is **exec** the code generation is configured to produce
               static binary. In this case **-fpic** and **-fpie** are both disabled.
    
               If _type_ is **dyn** the code generation is configured to produce
               shared library. In this case **-fpic** or **-fPIC** is preserved, but
               not enabled automatically.  This makes it possible to build
               shared libraries without position independent code on
               architectures this is possible, i.e. on x86.
    
               If _type_ is **pie** the code generation is configured to produce
               **-fpie** executable. This result in similar optimizations as **exec**
               except that **-fpie** is not disabled if specified at compilation
               time.
    
               If _type_ is **rel** the compiler assumes that incremental linking
               is done.  The sections containing intermediate code for link-
               time optimization are merged, pre-optimized, and output to the
               resulting object file. In addition, if **-ffat-lto-objects** is
               specified the binary code is produced for future non-lto
               linking. The object file produced by incremental linking will
               be smaller than a static library produced from the same object
               files.  At link-time the result of incremental linking will
               also load faster to compiler than a static library assuming
               that majority of objects in the library are used.
    
               Finally **nolto-rel** configure compiler to for incremental
               linking where code generation is forced, final binary is
               produced and the intermediate code for later link-time
               optimization is stripped. When multiple object files are
               linked together the resulting code will be optimized better
               than with link time optimizations disabled (for example, the
               cross-module inlining will happen), most of benefits of whole
               program optimizations are however lost.
    
               During the incremental link (by **-r**) the linker plugin will
               default to **rel**. With current interfaces to GNU Binutils it is
               however not possible to link incrementally LTO objects and
               non-LTO objects into a single mixed object file.  In the case
               any of object files in incremental link cannot be used for
               link-time optimization the linker plugin will output warning
               and use **nolto-rel**. To maintain the whole program optimization
               it is recommended to link such objects into static library
               instead. Alternatively it is possible to use H.J. Lu's
               binutils with support for mixed objects.
    
           **-fuse-ld=bfd**
               Use the **bfd** linker instead of the default linker.
    
           **-fuse-ld=gold**
               Use the **gold** linker instead of the default linker.
    
           **-fuse-ld=lld**
               Use the LLVM **lld** linker instead of the default linker.
    
           **-l** _library_
           **-l** _library_
               Search the library named _library_ when linking.  (The second
               alternative with the library as a separate argument is only
               for POSIX compliance and is not recommended.)
    
               The **-l** option is passed directly to the linker by GCC.  Refer
               to your linker documentation for exact details.  The general
               description below applies to the GNU linker.
    
               The linker searches a standard list of directories for the
               library.  The directories searched include several standard
               system directories plus any that you specify with **-L**.
    
               Static libraries are archives of object files, and have file
               names like _liblibrary.a_.  Some targets also support shared
               libraries, which typically have names like _liblibrary.so_.  If
               both static and shared libraries are found, the linker gives
               preference to linking with the shared library unless the
               **-static** option is used.
    
               It makes a difference where in the command you write this
               option; the linker searches and processes libraries and object
               files in the order they are specified.  Thus, **foo.o -lz bar.o**
               searches library **z** after file _foo.o_ but before _bar.o_.  If
               _bar.o_ refers to functions in **z** , those functions may not be
               loaded.
    
           **-lobjc**
               You need this special case of the **-l** option in order to link
               an Objective-C or Objective-C++ program.
    
           **-nostartfiles**
               Do not use the standard system startup files when linking.
               The standard system libraries are used normally, unless
               **-nostdlib** , **-nolibc** , or **-nodefaultlibs** is used.
    
           **-nodefaultlibs**
               Do not use the standard system libraries when linking.  Only
               the libraries you specify are passed to the linker, and
               options specifying linkage of the system libraries, such as
               **-static-libgcc** or **-shared-libgcc** , are ignored.  The standard
               startup files are used normally, unless **-nostartfiles** is used.
    
               The compiler may generate calls to "memcmp", "memset",
               "memcpy" and "memmove".  These entries are usually resolved by
               entries in libc.  These entry points should be supplied
               through some other mechanism when this option is specified.
    
           **-nolibc**
               Do not use the C library or system libraries tightly coupled
               with it when linking.  Still link with the startup files,
               _libgcc_ or toolchain provided language support libraries such
               as _libgnat_ , _libgfortran_ or _libstdc++_ unless options preventing
               their inclusion are used as well.  This typically removes **-lc**
               from the link command line, as well as system libraries that
               normally go with it and become meaningless when absence of a C
               library is assumed, for example **-lpthread** or **-lm** in some
               configurations.  This is intended for bare-board targets when
               there is indeed no C library available.
    
           **-nostdlib**
               Do not use the standard system startup files or libraries when
               linking.  No startup files and only the libraries you specify
               are passed to the linker, and options specifying linkage of
               the system libraries, such as **-static-libgcc** or
               **-shared-libgcc** , are ignored.
    
               The compiler may generate calls to "memcmp", "memset",
               "memcpy" and "memmove".  These entries are usually resolved by
               entries in libc.  These entry points should be supplied
               through some other mechanism when this option is specified.
    
               One of the standard libraries bypassed by **-nostdlib** and
               **-nodefaultlibs** is _libgcc.a_ , a library of internal subroutines
               which GCC uses to overcome shortcomings of particular
               machines, or special needs for some languages.
    
               In most cases, you need _libgcc.a_ even when you want to avoid
               other standard libraries.  In other words, when you specify
               **-nostdlib** or **-nodefaultlibs** you should usually specify **-lgcc**
               as well.  This ensures that you have no unresolved references
               to internal GCC library subroutines.  (An example of such an
               internal subroutine is "__main", used to ensure C++
               constructors are called.)
    
           **-e** _entry_
           **--entry=**_entry_
               Specify that the program entry point is _entry_.  The argument
               is interpreted by the linker; the GNU linker accepts either a
               symbol name or an address.
    
           **-pie**
               Produce a dynamically linked position independent executable
               on targets that support it.  For predictable results, you must
               also specify the same set of options used for compilation
               (**-fpie** , **-fPIE** , or model suboptions) when you specify this
               linker option.
    
           **-no-pie**
               Don't produce a dynamically linked position independent
               executable.
    
           **-static-pie**
               Produce a static position independent executable on targets
               that support it.  A static position independent executable is
               similar to a static executable, but can be loaded at any
               address without a dynamic linker.  For predictable results,
               you must also specify the same set of options used for
               compilation (**-fpie** , **-fPIE** , or model suboptions) when you
               specify this linker option.
    
           **-pthread**
               Link with the POSIX threads library.  This option is supported
               on GNU/Linux targets, most other Unix derivatives, and also on
               x86 Cygwin and MinGW targets.  On some targets this option
               also sets flags for the preprocessor, so it should be used
               consistently for both compilation and linking.
    
           **-r** Produce a relocatable object as output.  This is also known as
               partial linking.
    
           **-rdynamic**
               Pass the flag **-export-dynamic** to the ELF linker, on targets
               that support it. This instructs the linker to add all symbols,
               not only used ones, to the dynamic symbol table. This option
               is needed for some uses of "dlopen" or to allow obtaining
               backtraces from within a program.
    
           **-s** Remove all symbol table and relocation information from the
               executable.
    
           **-static**
               On systems that support dynamic linking, this overrides **-pie**
               and prevents linking with the shared libraries.  On other
               systems, this option has no effect.
    
           **-shared**
               Produce a shared object which can then be linked with other
               objects to form an executable.  Not all systems support this
               option.  For predictable results, you must also specify the
               same set of options used for compilation (**-fpic** , **-fPIC** , or
               model suboptions) when you specify this linker option.[1]
    
           **-shared-libgcc**
           **-static-libgcc**
               On systems that provide _libgcc_ as a shared library, these
               options force the use of either the shared or static version,
               respectively.  If no shared version of _libgcc_ was built when
               the compiler was configured, these options have no effect.
    
               There are several situations in which an application should
               use the shared _libgcc_ instead of the static version.  The most
               common of these is when the application wishes to throw and
               catch exceptions across different shared libraries.  In that
               case, each of the libraries as well as the application itself
               should use the shared _libgcc_.
    
               Therefore, the G++ driver automatically adds **-shared-libgcc**
               whenever you build a shared library or a main executable,
               because C++ programs typically use exceptions, so this is the
               right thing to do.
    
               If, instead, you use the GCC driver to create shared
               libraries, you may find that they are not always linked with
               the shared _libgcc_.  If GCC finds, at its configuration time,
               that you have a non-GNU linker or a GNU linker that does not
               support option **--eh-frame-hdr** , it links the shared version of
               _libgcc_ into shared libraries by default.  Otherwise, it takes
               advantage of the linker and optimizes away the linking with
               the shared version of _libgcc_ , linking with the static version
               of libgcc by default.  This allows exceptions to propagate
               through such shared libraries, without incurring relocation
               costs at library load time.
    
               However, if a library or main executable is supposed to throw
               or catch exceptions, you must link it using the G++ driver, or
               using the option **-shared-libgcc** , such that it is linked with
               the shared _libgcc_.
    
           **-static-libasan**
               When the **-fsanitize=address** option is used to link a program,
               the GCC driver automatically links against **libasan**.  If
               _libasan_ is available as a shared library, and the **-static**
               option is not used, then this links against the shared version
               of _libasan_.  The **-static-libasan** option directs the GCC driver
               to link _libasan_ statically, without necessarily linking other
               libraries statically.
    
           **-static-libtsan**
               When the **-fsanitize=thread** option is used to link a program,
               the GCC driver automatically links against **libtsan**.  If
               _libtsan_ is available as a shared library, and the **-static**
               option is not used, then this links against the shared version
               of _libtsan_.  The **-static-libtsan** option directs the GCC driver
               to link _libtsan_ statically, without necessarily linking other
               libraries statically.
    
           **-static-liblsan**
               When the **-fsanitize=leak** option is used to link a program, the
               GCC driver automatically links against **liblsan**.  If _liblsan_ is
               available as a shared library, and the **-static** option is not
               used, then this links against the shared version of _liblsan_.
               The **-static-liblsan** option directs the GCC driver to link
               _liblsan_ statically, without necessarily linking other
               libraries statically.
    
           **-static-libubsan**
               When the **-fsanitize=undefined** option is used to link a
               program, the GCC driver automatically links against **libubsan**.
               If _libubsan_ is available as a shared library, and the **-static**
               option is not used, then this links against the shared version
               of _libubsan_.  The **-static-libubsan** option directs the GCC
               driver to link _libubsan_ statically, without necessarily
               linking other libraries statically.
    
           **-static-libstdc++**
               When the **g++** program is used to link a C++ program, it
               normally automatically links against **libstdc++**.  If _libstdc++_
               is available as a shared library, and the **-static** option is
               not used, then this links against the shared version of
               _libstdc++_.  That is normally fine.  However, it is sometimes
               useful to freeze the version of _libstdc++_ used by the program
               without going all the way to a fully static link.  The
               **-static-libstdc++** option directs the **g++** driver to link
               _libstdc++_ statically, without necessarily linking other
               libraries statically.
    
           **-symbolic**
               Bind references to global symbols when building a shared
               object.  Warn about any unresolved references (unless
               overridden by the link editor option **-Xlinker -z -Xlinker**
               **defs**).  Only a few systems support this option.
    
           **-T** _script_
               Use _script_ as the linker script.  This option is supported by
               most systems using the GNU linker.  On some targets, such as
               bare-board targets without an operating system, the **-T** option
               may be required when linking to avoid references to undefined
               symbols.
    
           **-Xlinker** _option_
               Pass _option_ as an option to the linker.  You can use this to
               supply system-specific linker options that GCC does not
               recognize.
    
               If you want to pass an option that takes a separate argument,
               you must use **-Xlinker** twice, once for the option and once for
               the argument.  For example, to pass **-assert definitions** , you
               must write **-Xlinker -assert -Xlinker definitions**.  It does not
               work to write **-Xlinker "-assert definitions"** , because this
               passes the entire string as a single argument, which is not
               what the linker expects.
    
               When using the GNU linker, it is usually more convenient to
               pass arguments to linker options using the _option_**=**_value_ syntax
               than as separate arguments.  For example, you can specify
               **-Xlinker -Map=output.map** rather than **-Xlinker -Map -Xlinker**
               **output.map**.  Other linkers may not support this syntax for
               command-line options.
    
           **-Wl,**_option_
               Pass _option_ as an option to the linker.  If _option_ contains
               commas, it is split into multiple options at the commas.  You
               can use this syntax to pass an argument to the option.  For
               example, **-Wl,-Map,output.map** passes **-Map output.map** to the
               linker.  When using the GNU linker, you can also get the same
               effect with **-Wl,-Map=output.map**.
    
           **-u** _symbol_
               Pretend the symbol _symbol_ is undefined, to force linking of
               library modules to define it.  You can use **-u** multiple times
               with different symbols to force loading of additional library
               modules.
    
           **-z** _keyword_
               **-z** is passed directly on to the linker along with the keyword
               _keyword_. See the section in the documentation of your linker
               for permitted values and their meanings.
    
       **Options for Directory Search**
           These options specify directories to search for header files, for
           libraries and for parts of the compiler:
    
           **-I** _dir_
           **-iquote** _dir_
           **-isystem** _dir_
           **-idirafter** _dir_
               Add the directory _dir_ to the list of directories to be
               searched for header files during preprocessing.  If _dir_ begins
               with **=** or $SYSROOT, then the **=** or $SYSROOT is replaced by the
               sysroot prefix; see **--sysroot** and **-isysroot**.
    
               Directories specified with **-iquote** apply only to the quote
               form of the directive, "#include "_file""_.  Directories
               specified with **-I** , **-isystem** , or **-idirafter** apply to lookup for
               both the "#include "_file""_ and "#include <_file >"_ directives.
    
               You can specify any number or combination of these options on
               the command line to search for header files in several
               directories.  The lookup order is as follows:
    
               1.  For the quote form of the include directive, the directory
                   of the current file is searched first.
    
               2.  For the quote form of the include directive, the
                   directories specified by **-iquote** options are searched in
                   left-to-right order, as they appear on the command line.
    
               3.  Directories specified with **-I** options are scanned in left-
                   to-right order.
    
               4.  Directories specified with **-isystem** options are scanned in
                   left-to-right order.
    
               5.  Standard system directories are scanned.
    
               6.  Directories specified with **-idirafter** options are scanned
                   in left-to-right order.
    
               You can use **-I** to override a system header file, substituting
               your own version, since these directories are searched before
               the standard system header file directories.  However, you
               should not use this option to add directories that contain
               vendor-supplied system header files; use **-isystem** for that.
    
               The **-isystem** and **-idirafter** options also mark the directory as
               a system directory, so that it gets the same special treatment
               that is applied to the standard system directories.
    
               If a standard system include directory, or a directory
               specified with **-isystem** , is also specified with **-I** , the **-I**
               option is ignored.  The directory is still searched but as a
               system directory at its normal position in the system include
               chain.  This is to ensure that GCC's procedure to fix buggy
               system headers and the ordering for the "#include_next"
               directive are not inadvertently changed.  If you really need
               to change the search order for system directories, use the
               **-nostdinc** and/or **-isystem** options.
    
           **-I-** Split the include path.  This option has been deprecated.
               Please use **-iquote** instead for **-I** directories before the **-I-**
               and remove the **-I-** option.
    
               Any directories specified with **-I** options before **-I-** are
               searched only for headers requested with "#include "_file""_ ;
               they are not searched for "#include <_file >"_.  If additional
               directories are specified with **-I** options after the **-I-** , those
               directories are searched for all **#include** directives.
    
               In addition, **-I-** inhibits the use of the directory of the
               current file directory as the first search directory for
               "#include "_file""_.  There is no way to override this effect of
               **-I-**.
    
           **-iprefix** _prefix_
               Specify _prefix_ as the prefix for subsequent **-iwithprefix**
               options.  If the prefix represents a directory, you should
               include the final **/**.
    
           **-iwithprefix** _dir_
           **-iwithprefixbefore** _dir_
               Append _dir_ to the prefix specified previously with **-iprefix** ,
               and add the resulting directory to the include search path.
               **-iwithprefixbefore** puts it in the same place **-I** would;
               **-iwithprefix** puts it where **-idirafter** would.
    
           **-isysroot** _dir_
               This option is like the **--sysroot** option, but applies only to
               header files (except for Darwin targets, where it applies to
               both header files and libraries).  See the **--sysroot** option
               for more information.
    
           **-imultilib** _dir_
               Use _dir_ as a subdirectory of the directory containing target-
               specific C++ headers.
    
           **-nostdinc**
               Do not search the standard system directories for header
               files.  Only the directories explicitly specified with **-I** ,
               **-iquote** , **-isystem** , and/or **-idirafter** options (and the
               directory of the current file, if appropriate) are searched.
    
           **-nostdinc++**
               Do not search for header files in the C++-specific standard
               directories, but do still search the other standard
               directories.  (This option is used when building the C++
               library.)
    
           **-iplugindir=**_dir_
               Set the directory to search for plugins that are passed by
               **-fplugin=**_name_ instead of **-fplugin=**_path_**/**_name_**.so**.  This option
               is not meant to be used by the user, but only passed by the
               driver.
    
           **-L** _dir_
               Add directory _dir_ to the list of directories to be searched
               for **-l**.
    
           **-B** _prefix_
               This option specifies where to find the executables,
               libraries, include files, and data files of the compiler
               itself.
    
               The compiler driver program runs one or more of the
               subprograms **cpp** , **cc1** , **as** and **ld**.  It tries _prefix_ as a prefix
               for each program it tries to run, both with and without
               _machine_**/**_version_**/** for the corresponding target machine and
               compiler version.
    
               For each subprogram to be run, the compiler driver first tries
               the **-B** prefix, if any.  If that name is not found, or if **-B** is
               not specified, the driver tries two standard prefixes,
               _/usr/lib/gcc/_ and _/usr/local/lib/gcc/_.  If neither of those
               results in a file name that is found, the unmodified program
               name is searched for using the directories specified in your
               **PATH** environment variable.
    
               The compiler checks to see if the path provided by **-B** refers
               to a directory, and if necessary it adds a directory separator
               character at the end of the path.
    
               **-B** prefixes that effectively specify directory names also
               apply to libraries in the linker, because the compiler
               translates these options into **-L** options for the linker.  They
               also apply to include files in the preprocessor, because the
               compiler translates these options into **-isystem** options for
               the preprocessor.  In this case, the compiler appends **include**
               to the prefix.
    
               The runtime support file _libgcc.a_ can also be searched for
               using the **-B** prefix, if needed.  If it is not found there, the
               two standard prefixes above are tried, and that is all.  The
               file is left out of the link if it is not found by those
               means.
    
               Another way to specify a prefix much like the **-B** prefix is to
               use the environment variable **GCC_EXEC_PREFIX**.
    
               As a special kludge, if the path provided by **-B** is
               _[dir/]stageN/_ , where _N_ is a number in the range 0 to 9, then
               it is replaced by _[dir/]include_.  This is to help with boot-
               strapping the compiler.
    
           **-no-canonical-prefixes**
               Do not expand any symbolic links, resolve references to **/../**
               or **/./** , or make the path absolute when generating a relative
               prefix.
    
           **--sysroot=**_dir_
               Use _dir_ as the logical root directory for headers and
               libraries.  For example, if the compiler normally searches for
               headers in _/usr/include_ and libraries in _/usr/lib_ , it instead
               searches _dir/usr/include_ and _dir/usr/lib_.
    
               If you use both this option and the **-isysroot** option, then the
               **--sysroot** option applies to libraries, but the **-isysroot**
               option applies to header files.
    
               The GNU linker (beginning with version 2.16) has the necessary
               support for this option.  If your linker does not support this
               option, the header file aspect of **--sysroot** still works, but
               the library aspect does not.
    
           **--no-sysroot-suffix**
               For some targets, a suffix is added to the root directory
               specified with **--sysroot** , depending on the other options used,
               so that headers may for example be found in
               _dir/suffix/usr/include_ instead of _dir/usr/include_.  This
               option disables the addition of such a suffix.
    
       **Options for Code Generation Conventions**
           These machine-independent options control the interface
           conventions used in code generation.
    
           Most of them have both positive and negative forms; the negative
           form of **-ffoo** is **-fno-foo**.  In the table below, only one of the
           forms is listed---the one that is not the default.  You can figure
           out the other form by either removing **no-** or adding it.
    
           **-fstack-reuse=**_reuse-level_
               This option controls stack space reuse for user declared
               local/auto variables and compiler generated temporaries.
               _reuse_level_ can be **all** , **named_vars** , or **none**. **all** enables stack
               reuse for all local variables and temporaries, **named_vars**
               enables the reuse only for user defined local variables with
               names, and **none** disables stack reuse completely. The default
               value is **all**. The option is needed when the program extends
               the lifetime of a scoped local variable or a compiler
               generated temporary beyond the end point defined by the
               language.  When a lifetime of a variable ends, and if the
               variable lives in memory, the optimizing compiler has the
               freedom to reuse its stack space with other temporaries or
               scoped local variables whose live range does not overlap with
               it. Legacy code extending local lifetime is likely to break
               with the stack reuse optimization.
    
               For example,
    
                          int *p;
                          {
                            int local1;
    
                            p = &local1;
                            local1 = 10;
                            ....
                          }
                          {
                             int local2;
                             local2 = 20;
                             ...
                          }
    
                          if (*p == 10)  // out of scope use of local1
                            {
    
                            }
    
               Another example:
    
                          struct A
                          {
                              A(int k) : i(k), j(k) { }
                              int i;
                              int j;
                          };
    
                          A *ap;
    
                          void foo(const A& ar)
                          {
                             ap = &ar;
                          }
    
                          void bar()
                          {
                             foo(A(10)); // temp object's lifetime ends when foo returns
    
                             {
                               A a(20);
                               ....
                             }
                             ap->i+= 10;  // ap references out of scope temp whose space
                                          // is reused with a. What is the value of ap->i?
                          }
    
               The lifetime of a compiler generated temporary is well defined
               by the C++ standard. When a lifetime of a temporary ends, and
               if the temporary lives in memory, the optimizing compiler has
               the freedom to reuse its stack space with other temporaries or
               scoped local variables whose live range does not overlap with
               it. However some of the legacy code relies on the behavior of
               older compilers in which temporaries' stack space is not
               reused, the aggressive stack reuse can lead to runtime errors.
               This option is used to control the temporary stack reuse
               optimization.
    
           **-ftrapv**
               This option generates traps for signed overflow on addition,
               subtraction, multiplication operations.  The options **-ftrapv**
               and **-fwrapv** override each other, so using **-ftrapv -fwrapv** on
               the command-line results in **-fwrapv** being effective.  Note
               that only active options override, so using **-ftrapv -fwrapv**
               **-fno-wrapv** on the command-line results in **-ftrapv** being
               effective.
    
           **-fwrapv**
               This option instructs the compiler to assume that signed
               arithmetic overflow of addition, subtraction and
               multiplication wraps around using twos-complement
               representation.  This flag enables some optimizations and
               disables others.  The options **-ftrapv** and **-fwrapv** override
               each other, so using **-ftrapv -fwrapv** on the command-line
               results in **-fwrapv** being effective.  Note that only active
               options override, so using **-ftrapv -fwrapv -fno-wrapv** on the
               command-line results in **-ftrapv** being effective.
    
           **-fwrapv-pointer**
               This option instructs the compiler to assume that pointer
               arithmetic overflow on addition and subtraction wraps around
               using twos-complement representation.  This flag disables some
               optimizations which assume pointer overflow is invalid.
    
           **-fstrict-overflow**
               This option implies **-fno-wrapv -fno-wrapv-pointer** and when
               negated implies **-fwrapv -fwrapv-pointer**.
    
           **-fexceptions**
               Enable exception handling.  Generates extra code needed to
               propagate exceptions.  For some targets, this implies GCC
               generates frame unwind information for all functions, which
               can produce significant data size overhead, although it does
               not affect execution.  If you do not specify this option, GCC
               enables it by default for languages like C++ that normally
               require exception handling, and disables it for languages like
               C that do not normally require it.  However, you may need to
               enable this option when compiling C code that needs to
               interoperate properly with exception handlers written in C++.
               You may also wish to disable this option if you are compiling
               older C++ programs that don't use exception handling.
    
           **-fnon-call-exceptions**
               Generate code that allows trapping instructions to throw
               exceptions.  Note that this requires platform-specific runtime
               support that does not exist everywhere.  Moreover, it only
               allows _trapping_ instructions to throw exceptions, i.e. memory
               references or floating-point instructions.  It does not allow
               exceptions to be thrown from arbitrary signal handlers such as
               "SIGALRM".
    
           **-fdelete-dead-exceptions**
               Consider that instructions that may throw exceptions but don't
               otherwise contribute to the execution of the program can be
               optimized away.  This option is enabled by default for the Ada
               front end, as permitted by the Ada language specification.
               Optimization passes that cause dead exceptions to be removed
               are enabled independently at different optimization levels.
    
           **-funwind-tables**
               Similar to **-fexceptions** , except that it just generates any
               needed static data, but does not affect the generated code in
               any other way.  You normally do not need to enable this
               option; instead, a language processor that needs this handling
               enables it on your behalf.
    
           **-fasynchronous-unwind-tables**
               Generate unwind table in DWARF format, if supported by target
               machine.  The table is exact at each instruction boundary, so
               it can be used for stack unwinding from asynchronous events
               (such as debugger or garbage collector).
    
           **-fno-gnu-unique**
               On systems with recent GNU assembler and C library, the C++
               compiler uses the "STB_GNU_UNIQUE" binding to make sure that
               definitions of template static data members and static local
               variables in inline functions are unique even in the presence
               of "RTLD_LOCAL"; this is necessary to avoid problems with a
               library used by two different "RTLD_LOCAL" plugins depending
               on a definition in one of them and therefore disagreeing with
               the other one about the binding of the symbol.  But this
               causes "dlclose" to be ignored for affected DSOs; if your
               program relies on reinitialization of a DSO via "dlclose" and
               "dlopen", you can use **-fno-gnu-unique**.
    
           **-fpcc-struct-return**
               Return "short" "struct" and "union" values in memory like
               longer ones, rather than in registers.  This convention is
               less efficient, but it has the advantage of allowing
               intercallability between GCC-compiled files and files compiled
               with other compilers, particularly the Portable C Compiler
               (pcc).
    
               The precise convention for returning structures in memory
               depends on the target configuration macros.
    
               Short structures and unions are those whose size and alignment
               match that of some integer type.
    
               **Warning:** code compiled with the **-fpcc-struct-return** switch is
               not binary compatible with code compiled with the
               **-freg-struct-return** switch.  Use it to conform to a non-
               default application binary interface.
    
           **-freg-struct-return**
               Return "struct" and "union" values in registers when possible.
               This is more efficient for small structures than
               **-fpcc-struct-return**.
    
               If you specify neither **-fpcc-struct-return** nor
               **-freg-struct-return** , GCC defaults to whichever convention is
               standard for the target.  If there is no standard convention,
               GCC defaults to **-fpcc-struct-return** , except on targets where
               GCC is the principal compiler.  In those cases, we can choose
               the standard, and we chose the more efficient register return
               alternative.
    
               **Warning:** code compiled with the **-freg-struct-return** switch is
               not binary compatible with code compiled with the
               **-fpcc-struct-return** switch.  Use it to conform to a non-
               default application binary interface.
    
           **-fshort-enums**
               Allocate to an "enum" type only as many bytes as it needs for
               the declared range of possible values.  Specifically, the
               "enum" type is equivalent to the smallest integer type that
               has enough room.
    
               **Warning:** the **-fshort-enums** switch causes GCC to generate code
               that is not binary compatible with code generated without that
               switch.  Use it to conform to a non-default application binary
               interface.
    
           **-fshort-wchar**
               Override the underlying type for "wchar_t" to be "short
               unsigned int" instead of the default for the target.  This
               option is useful for building programs to run under WINE.
    
               **Warning:** the **-fshort-wchar** switch causes GCC to generate code
               that is not binary compatible with code generated without that
               switch.  Use it to conform to a non-default application binary
               interface.
    
           **-fno-common**
               In C code, this option controls the placement of global
               variables defined without an initializer, known as _tentative_
               _definitions_ in the C standard.  Tentative definitions are
               distinct from declarations of a variable with the "extern"
               keyword, which do not allocate storage.
    
               Unix C compilers have traditionally allocated storage for
               uninitialized global variables in a common block.  This allows
               the linker to resolve all tentative definitions of the same
               variable in different compilation units to the same object, or
               to a non-tentative definition.  This is the behavior specified
               by **-fcommon** , and is the default for GCC on most targets.  On
               the other hand, this behavior is not required by ISO C, and on
               some targets may carry a speed or code size penalty on
               variable references.
    
               The **-fno-common** option specifies that the compiler should
               instead place uninitialized global variables in the BSS
               section of the object file.  This inhibits the merging of
               tentative definitions by the linker so you get a multiple-
               definition error if the same variable is defined in more than
               one compilation unit.  Compiling with **-fno-common** is useful on
               targets for which it provides better performance, or if you
               wish to verify that the program will work on other systems
               that always treat uninitialized variable definitions this way.
    
           **-fno-ident**
               Ignore the "#ident" directive.
    
           **-finhibit-size-directive**
               Don't output a ".size" assembler directive, or anything else
               that would cause trouble if the function is split in the
               middle, and the two halves are placed at locations far apart
               in memory.  This option is used when compiling _crtstuff.c_ ; you
               should not need to use it for anything else.
    
           **-fverbose-asm**
               Put extra commentary information in the generated assembly
               code to make it more readable.  This option is generally only
               of use to those who actually need to read the generated
               assembly code (perhaps while debugging the compiler itself).
    
               **-fno-verbose-asm** , the default, causes the extra information to
               be omitted and is useful when comparing two assembler files.
    
               The added comments include:
    
               *   information on the compiler version and command-line
                   options,
    
               *   the source code lines associated with the assembly
                   instructions, in the form FILENAME:LINENUMBER:CONTENT OF
                   LINE,
    
               *   hints on which high-level expressions correspond to the
                   various assembly instruction operands.
    
               For example, given this C source file:
    
                       int test (int n)
                       {
                         int i;
                         int total = 0;
    
                         for (i = 0; i < n; i++)
                           total += i * i;
    
                         return total;
                       }
    
               compiling to (x86_64) assembly via **-S** and emitting the result
               direct to stdout via **-o -**
    
                       gcc -S test.c -fverbose-asm -Os -o -
    
               gives output similar to this:
    
                               .file   "test.c"
                       # GNU C11 (GCC) version 7.0.0 20160809 (experimental) (x86_64-pc-linux-gnu)
                         [...snip...]
                       # options passed:
                         [...snip...]
    
                               .text
                               .globl  test
                               .type   test, @function
                       test:
                       .LFB0:
                               .cfi_startproc
                       # test.c:4:   int total = 0;
                               xorl    %eax, %eax      # <retval>
                       # test.c:6:   for (i = 0; i < n; i++)
                               xorl    %edx, %edx      # i
                       .L2:
                       # test.c:6:   for (i = 0; i < n; i++)
                               cmpl    %edi, %edx      # n, i
                               jge     .L5     #,
                       # test.c:7:     total += i * i;
                               movl    %edx, %ecx      # i, tmp92
                               imull   %edx, %ecx      # i, tmp92
                       # test.c:6:   for (i = 0; i < n; i++)
                               incl    %edx    # i
                       # test.c:7:     total += i * i;
                               addl    %ecx, %eax      # tmp92, <retval>
                               jmp     .L2     #
                       .L5:
                       # test.c:10: }
                               ret
                               .cfi_endproc
                       .LFE0:
                               .size   test, .-test
                               .ident  "GCC: (GNU) 7.0.0 20160809 (experimental)"
                               .section        .note.GNU-stack,"",@progbits
    
               The comments are intended for humans rather than machines and
               hence the precise format of the comments is subject to change.
    
           **-frecord-gcc-switches**
               This switch causes the command line used to invoke the
               compiler to be recorded into the object file that is being
               created.  This switch is only implemented on some targets and
               the exact format of the recording is target and binary file
               format dependent, but it usually takes the form of a section
               containing ASCII text.  This switch is related to the
               **-fverbose-asm** switch, but that switch only records information
               in the assembler output file as comments, so it never reaches
               the object file.  See also **-grecord-gcc-switches** for another
               way of storing compiler options into the object file.
    
           **-fpic**
               Generate position-independent code (PIC) suitable for use in a
               shared library, if supported for the target machine.  Such
               code accesses all constant addresses through a global offset
               table (GOT).  The dynamic loader resolves the GOT entries when
               the program starts (the dynamic loader is not part of GCC; it
               is part of the operating system).  If the GOT size for the
               linked executable exceeds a machine-specific maximum size, you
               get an error message from the linker indicating that **-fpic**
               does not work; in that case, recompile with **-fPIC** instead.
               (These maximums are 8k on the SPARC, 28k on AArch64 and 32k on
               the m68k and RS/6000.  The x86 has no such limit.)
    
               Position-independent code requires special support, and
               therefore works only on certain machines.  For the x86, GCC
               supports PIC for System V but not for the Sun 386i.  Code
               generated for the IBM RS/6000 is always position-independent.
    
               When this flag is set, the macros "__pic__" and "__PIC__" are
               defined to 1.
    
           **-fPIC**
               If supported for the target machine, emit position-independent
               code, suitable for dynamic linking and avoiding any limit on
               the size of the global offset table.  This option makes a
               difference on AArch64, m68k, PowerPC and SPARC.
    
               Position-independent code requires special support, and
               therefore works only on certain machines.
    
               When this flag is set, the macros "__pic__" and "__PIC__" are
               defined to 2.
    
           **-fpie**
           **-fPIE**
               These options are similar to **-fpic** and **-fPIC** , but the
               generated position-independent code can be only linked into
               executables.  Usually these options are used to compile code
               that will be linked using the **-pie** GCC option.
    
               **-fpie** and **-fPIE** both define the macros "__pie__" and
               "__PIE__".  The macros have the value 1 for **-fpie** and 2 for
               **-fPIE**.
    
           **-fno-plt**
               Do not use the PLT for external function calls in position-
               independent code.  Instead, load the callee address at call
               sites from the GOT and branch to it.  This leads to more
               efficient code by eliminating PLT stubs and exposing GOT loads
               to optimizations.  On architectures such as 32-bit x86 where
               PLT stubs expect the GOT pointer in a specific register, this
               gives more register allocation freedom to the compiler.  Lazy
               binding requires use of the PLT; with **-fno-plt** all external
               symbols are resolved at load time.
    
               Alternatively, the function attribute "noplt" can be used to
               avoid calls through the PLT for specific external functions.
    
               In position-dependent code, a few targets also convert calls
               to functions that are marked to not use the PLT to use the GOT
               instead.
    
           **-fno-jump-tables**
               Do not use jump tables for switch statements even where it
               would be more efficient than other code generation strategies.
               This option is of use in conjunction with **-fpic** or **-fPIC** for
               building code that forms part of a dynamic linker and cannot
               reference the address of a jump table.  On some targets, jump
               tables do not require a GOT and this option is not needed.
    
           **-ffixed-**_reg_
               Treat the register named _reg_ as a fixed register; generated
               code should never refer to it (except perhaps as a stack
               pointer, frame pointer or in some other fixed role).
    
               _reg_ must be the name of a register.  The register names
               accepted are machine-specific and are defined in the
               "REGISTER_NAMES" macro in the machine description macro file.
    
               This flag does not have a negative form, because it specifies
               a three-way choice.
    
           **-fcall-used-**_reg_
               Treat the register named _reg_ as an allocable register that is
               clobbered by function calls.  It may be allocated for
               temporaries or variables that do not live across a call.
               Functions compiled this way do not save and restore the
               register _reg_.
    
               It is an error to use this flag with the frame pointer or
               stack pointer.  Use of this flag for other registers that have
               fixed pervasive roles in the machine's execution model
               produces disastrous results.
    
               This flag does not have a negative form, because it specifies
               a three-way choice.
    
           **-fcall-saved-**_reg_
               Treat the register named _reg_ as an allocable register saved by
               functions.  It may be allocated even for temporaries or
               variables that live across a call.  Functions compiled this
               way save and restore the register _reg_ if they use it.
    
               It is an error to use this flag with the frame pointer or
               stack pointer.  Use of this flag for other registers that have
               fixed pervasive roles in the machine's execution model
               produces disastrous results.
    
               A different sort of disaster results from the use of this flag
               for a register in which function values may be returned.
    
               This flag does not have a negative form, because it specifies
               a three-way choice.
    
           **-fpack-struct[=**_n_**]**
               Without a value specified, pack all structure members together
               without holes.  When a value is specified (which must be a
               small power of two), pack structure members according to this
               value, representing the maximum alignment (that is, objects
               with default alignment requirements larger than this are
               output potentially unaligned at the next fitting location.
    
               **Warning:** the **-fpack-struct** switch causes GCC to generate code
               that is not binary compatible with code generated without that
               switch.  Additionally, it makes the code suboptimal.  Use it
               to conform to a non-default application binary interface.
    
           **-fleading-underscore**
               This option and its counterpart, **-fno-leading-underscore** ,
               forcibly change the way C symbols are represented in the
               object file.  One use is to help link with legacy assembly
               code.
    
               **Warning:** the **-fleading-underscore** switch causes GCC to
               generate code that is not binary compatible with code
               generated without that switch.  Use it to conform to a non-
               default application binary interface.  Not all targets provide
               complete support for this switch.
    
           **-ftls-model=**_model_
               Alter the thread-local storage model to be used.  The _model_
               argument should be one of **global-dynamic** , **local-dynamic** ,
               **initial-exec** or **local-exec**.  Note that the choice is subject
               to optimization: the compiler may use a more efficient model
               for symbols not visible outside of the translation unit, or if
               **-fpic** is not given on the command line.
    
               The default without **-fpic** is **initial-exec** ; with **-fpic** the
               default is **global-dynamic**.
    
           **-ftrampolines**
               For targets that normally need trampolines for nested
               functions, always generate them instead of using descriptors.
               Otherwise, for targets that do not need them, like for example
               HP-PA or IA-64, do nothing.
    
               A trampoline is a small piece of code that is created at run
               time on the stack when the address of a nested function is
               taken, and is used to call the nested function indirectly.
               Therefore, it requires the stack to be made executable in
               order for the program to work properly.
    
               **-fno-trampolines** is enabled by default on a language by
               language basis to let the compiler avoid generating them, if
               it computes that this is safe, and replace them with
               descriptors.  Descriptors are made up of data only, but the
               generated code must be prepared to deal with them.  As of this
               writing, **-fno-trampolines** is enabled by default only for Ada.
    
               Moreover, code compiled with **-ftrampolines** and code compiled
               with **-fno-trampolines** are not binary compatible if nested
               functions are present.  This option must therefore be used on
               a program-wide basis and be manipulated with extreme care.
    
           **-fvisibility=**[**default** |**internal** |**hidden** |**protected**]
               Set the default ELF image symbol visibility to the specified
               option---all symbols are marked with this unless overridden
               within the code.  Using this feature can very substantially
               improve linking and load times of shared object libraries,
               produce more optimized code, provide near-perfect API export
               and prevent symbol clashes.  It is **strongly** recommended that
               you use this in any shared objects you distribute.
    
               Despite the nomenclature, **default** always means public; i.e.,
               available to be linked against from outside the shared object.
               **protected** and **internal** are pretty useless in real-world usage
               so the only other commonly used option is **hidden**.  The default
               if **-fvisibility** isn't specified is **default** , i.e., make every
               symbol public.
    
               A good explanation of the benefits offered by ensuring ELF
               symbols have the correct visibility is given by "How To Write
               Shared Libraries" by Ulrich Drepper (which can be found at
               <**https://www.akkadia.org/drepper/ **>)---however a superior
               solution made possible by this option to marking things hidden
               when the default is public is to make the default hidden and
               mark things public.  This is the norm with DLLs on Windows and
               with **-fvisibility=hidden** and "__attribute__
               ((visibility("default")))" instead of "__declspec(dllexport)"
               you get almost identical semantics with identical syntax.
               This is a great boon to those working with cross-platform
               projects.
    
               For those adding visibility support to existing code, you may
               find "#pragma GCC visibility" of use.  This works by you
               enclosing the declarations you wish to set visibility for with
               (for example) "#pragma GCC visibility push(hidden)" and
               "#pragma GCC visibility pop".  Bear in mind that symbol
               visibility should be viewed **as part of the API interface**
               **contract** and thus all new code should always specify
               visibility when it is not the default; i.e., declarations only
               for use within the local DSO should **always** be marked
               explicitly as hidden as so to avoid PLT indirection
               overheads---making this abundantly clear also aids readability
               and self-documentation of the code.  Note that due to ISO C++
               specification requirements, "operator new" and "operator
               delete" must always be of default visibility.
    
               Be aware that headers from outside your project, in particular
               system headers and headers from any other library you use, may
               not be expecting to be compiled with visibility other than the
               default.  You may need to explicitly say "#pragma GCC
               visibility push(default)" before including any such headers.
    
               "extern" declarations are not affected by **-fvisibility** , so a
               lot of code can be recompiled with **-fvisibility=hidden** with no
               modifications.  However, this means that calls to "extern"
               functions with no explicit visibility use the PLT, so it is
               more effective to use "__attribute ((visibility))" and/or
               "#pragma GCC visibility" to tell the compiler which "extern"
               declarations should be treated as hidden.
    
               Note that **-fvisibility** does affect C++ vague linkage entities.
               This means that, for instance, an exception class that is be
               thrown between DSOs must be explicitly marked with default
               visibility so that the **type_info** nodes are unified between the
               DSOs.
    
               An overview of these techniques, their benefits and how to use
               them is at <**http://gcc.gnu.org/wiki/Visibility **>.
    
           **-fstrict-volatile-bitfields**
               This option should be used if accesses to volatile bit-fields
               (or other structure fields, although the compiler usually
               honors those types anyway) should use a single access of the
               width of the field's type, aligned to a natural alignment if
               possible.  For example, targets with memory-mapped peripheral
               registers might require all such accesses to be 16 bits wide;
               with this flag you can declare all peripheral bit-fields as
               "unsigned short" (assuming short is 16 bits on these targets)
               to force GCC to use 16-bit accesses instead of, perhaps, a
               more efficient 32-bit access.
    
               If this option is disabled, the compiler uses the most
               efficient instruction.  In the previous example, that might be
               a 32-bit load instruction, even though that accesses bytes
               that do not contain any portion of the bit-field, or memory-
               mapped registers unrelated to the one being updated.
    
               In some cases, such as when the "packed" attribute is applied
               to a structure field, it may not be possible to access the
               field with a single read or write that is correctly aligned
               for the target machine.  In this case GCC falls back to
               generating multiple accesses rather than code that will fault
               or truncate the result at run time.
    
               Note:  Due to restrictions of the C/C++11 memory model, write
               accesses are not allowed to touch non bit-field members.  It
               is therefore recommended to define all bits of the field's
               type as bit-field members.
    
               The default value of this option is determined by the
               application binary interface for the target processor.
    
           **-fsync-libcalls**
               This option controls whether any out-of-line instance of the
               "__sync" family of functions may be used to implement the
               C++11 "__atomic" family of functions.
    
               The default value of this option is enabled, thus the only
               useful form of the option is **-fno-sync-libcalls**.  This option
               is used in the implementation of the _libatomic_ runtime
               library.
    
       **GCC Developer Options**
           This section describes command-line options that are primarily of
           interest to GCC developers, including options to support compiler
           testing and investigation of compiler bugs and compile-time
           performance problems.  This includes options that produce debug
           dumps at various points in the compilation; that print statistics
           such as memory use and execution time; and that print information
           about GCC's configuration, such as where it searches for
           libraries.  You should rarely need to use any of these options for
           ordinary compilation and linking tasks.
    
           Many developer options that cause GCC to dump output to a file
           take an optional **=**_filename_ suffix. You can specify **stdout** or **-** to
           dump to standard output, and **stderr** for standard error.
    
           If **=**_filename_ is omitted, a default dump file name is constructed
           by concatenating the base dump file name, a pass number, phase
           letter, and pass name.  The base dump file name is the name of
           output file produced by the compiler if explicitly specified and
           not an executable; otherwise it is the source file name.  The pass
           number is determined by the order passes are registered with the
           compiler's pass manager.  This is generally the same as the order
           of execution, but passes registered by plugins, target-specific
           passes, or passes that are otherwise registered late are numbered
           higher than the pass named **final** , even if they are executed
           earlier.  The phase letter is one of **i**(inter-procedural
           analysis), **l**(language-specific), **r**(RTL), or **t**(tree).  The files
           are created in the directory of the output file.
    
           **-d** _letters_
           **-fdump-rtl-**_pass_
           **-fdump-rtl-**_pass_**=**_filename_
               Says to make debugging dumps during compilation at times
               specified by _letters_.  This is used for debugging the RTL-
               based passes of the compiler.
    
               Some **-d** _letters_ switches have different meaning when **-E** is used
               for preprocessing.
    
               Debug dumps can be enabled with a **-fdump-rtl** switch or some **-d**
               option _letters_.  Here are the possible letters for use in _pass_
               and _letters_ , and their meanings:
    
               **-fdump-rtl-alignments**
                   Dump after branch alignments have been computed.
    
               **-fdump-rtl-asmcons**
                   Dump after fixing rtl statements that have unsatisfied
                   in/out constraints.
    
               **-fdump-rtl-auto_inc_dec**
                   Dump after auto-inc-dec discovery.  This pass is only run
                   on architectures that have auto inc or auto dec
                   instructions.
    
               **-fdump-rtl-barriers**
                   Dump after cleaning up the barrier instructions.
    
               **-fdump-rtl-bbpart**
                   Dump after partitioning hot and cold basic blocks.
    
               **-fdump-rtl-bbro**
                   Dump after block reordering.
    
               **-fdump-rtl-btl1**
               **-fdump-rtl-btl2**
                   **-fdump-rtl-btl1** and **-fdump-rtl-btl2** enable dumping after
                   the two branch target load optimization passes.
    
               **-fdump-rtl-bypass**
                   Dump after jump bypassing and control flow optimizations.
    
               **-fdump-rtl-combine**
                   Dump after the RTL instruction combination pass.
    
               **-fdump-rtl-compgotos**
                   Dump after duplicating the computed gotos.
    
               **-fdump-rtl-ce1**
               **-fdump-rtl-ce2**
               **-fdump-rtl-ce3**
                   **-fdump-rtl-ce1** , **-fdump-rtl-ce2** , and **-fdump-rtl-ce3** enable
                   dumping after the three if conversion passes.
    
               **-fdump-rtl-cprop_hardreg**
                   Dump after hard register copy propagation.
    
               **-fdump-rtl-csa**
                   Dump after combining stack adjustments.
    
               **-fdump-rtl-cse1**
               **-fdump-rtl-cse2**
                   **-fdump-rtl-cse1** and **-fdump-rtl-cse2** enable dumping after
                   the two common subexpression elimination passes.
    
               **-fdump-rtl-dce**
                   Dump after the standalone dead code elimination passes.
    
               **-fdump-rtl-dbr**
                   Dump after delayed branch scheduling.
    
               **-fdump-rtl-dce1**
               **-fdump-rtl-dce2**
                   **-fdump-rtl-dce1** and **-fdump-rtl-dce2** enable dumping after
                   the two dead store elimination passes.
    
               **-fdump-rtl-eh**
                   Dump after finalization of EH handling code.
    
               **-fdump-rtl-eh_ranges**
                   Dump after conversion of EH handling range regions.
    
               **-fdump-rtl-expand**
                   Dump after RTL generation.
    
               **-fdump-rtl-fwprop1**
               **-fdump-rtl-fwprop2**
                   **-fdump-rtl-fwprop1** and **-fdump-rtl-fwprop2** enable dumping
                   after the two forward propagation passes.
    
               **-fdump-rtl-gcse1**
               **-fdump-rtl-gcse2**
                   **-fdump-rtl-gcse1** and **-fdump-rtl-gcse2** enable dumping after
                   global common subexpression elimination.
    
               **-fdump-rtl-init-regs**
                   Dump after the initialization of the registers.
    
               **-fdump-rtl-initvals**
                   Dump after the computation of the initial value sets.
    
               **-fdump-rtl-into_cfglayout**
                   Dump after converting to cfglayout mode.
    
               **-fdump-rtl-ira**
                   Dump after iterated register allocation.
    
               **-fdump-rtl-jump**
                   Dump after the second jump optimization.
    
               **-fdump-rtl-loop2**
                   **-fdump-rtl-loop2** enables dumping after the rtl loop
                   optimization passes.
    
               **-fdump-rtl-mach**
                   Dump after performing the machine dependent reorganization
                   pass, if that pass exists.
    
               **-fdump-rtl-mode_sw**
                   Dump after removing redundant mode switches.
    
               **-fdump-rtl-rnreg**
                   Dump after register renumbering.
    
               **-fdump-rtl-outof_cfglayout**
                   Dump after converting from cfglayout mode.
    
               **-fdump-rtl-peephole2**
                   Dump after the peephole pass.
    
               **-fdump-rtl-postreload**
                   Dump after post-reload optimizations.
    
               **-fdump-rtl-pro_and_epilogue**
                   Dump after generating the function prologues and
                   epilogues.
    
               **-fdump-rtl-sched1**
               **-fdump-rtl-sched2**
                   **-fdump-rtl-sched1** and **-fdump-rtl-sched2** enable dumping
                   after the basic block scheduling passes.
    
               **-fdump-rtl-ree**
                   Dump after sign/zero extension elimination.
    
               **-fdump-rtl-seqabstr**
                   Dump after common sequence discovery.
    
               **-fdump-rtl-shorten**
                   Dump after shortening branches.
    
               **-fdump-rtl-sibling**
                   Dump after sibling call optimizations.
    
               **-fdump-rtl-split1**
               **-fdump-rtl-split2**
               **-fdump-rtl-split3**
               **-fdump-rtl-split4**
               **-fdump-rtl-split5**
                   These options enable dumping after five rounds of
                   instruction splitting.
    
               **-fdump-rtl-sms**
                   Dump after modulo scheduling.  This pass is only run on
                   some architectures.
    
               **-fdump-rtl-stack**
                   Dump after conversion from GCC's "flat register file"
                   registers to the x87's stack-like registers.  This pass is
                   only run on x86 variants.
    
               **-fdump-rtl-subreg1**
               **-fdump-rtl-subreg2**
                   **-fdump-rtl-subreg1** and **-fdump-rtl-subreg2** enable dumping
                   after the two subreg expansion passes.
    
               **-fdump-rtl-unshare**
                   Dump after all rtl has been unshared.
    
               **-fdump-rtl-vartrack**
                   Dump after variable tracking.
    
               **-fdump-rtl-vregs**
                   Dump after converting virtual registers to hard registers.
    
               **-fdump-rtl-web**
                   Dump after live range splitting.
    
               **-fdump-rtl-regclass**
               **-fdump-rtl-subregs_of_mode_init**
               **-fdump-rtl-subregs_of_mode_finish**
               **-fdump-rtl-dfinit**
               **-fdump-rtl-dfinish**
                   These dumps are defined but always produce empty files.
    
               **-da**
               **-fdump-rtl-all**
                   Produce all the dumps listed above.
    
               **-dA** Annotate the assembler output with miscellaneous debugging
                   information.
    
               **-dD** Dump all macro definitions, at the end of preprocessing,
                   in addition to normal output.
    
               **-dH** Produce a core dump whenever an error occurs.
    
               **-dp** Annotate the assembler output with a comment indicating
                   which pattern and alternative is used.  The length and
                   cost of each instruction are also printed.
    
               **-dP** Dump the RTL in the assembler output as a comment before
                   each instruction.  Also turns on **-dp** annotation.
    
               **-dx** Just generate RTL for a function instead of compiling it.
                   Usually used with **-fdump-rtl-expand**.
    
           **-fdump-debug**
               Dump debugging information generated during the debug
               generation phase.
    
           **-fdump-earlydebug**
               Dump debugging information generated during the early debug
               generation phase.
    
           **-fdump-noaddr**
               When doing debugging dumps, suppress address output.  This
               makes it more feasible to use diff on debugging dumps for
               compiler invocations with different compiler binaries and/or
               different text / bss / data / heap / stack / dso start
               locations.
    
           **-freport-bug**
               Collect and dump debug information into a temporary file if an
               internal compiler error (ICE) occurs.
    
           **-fdump-unnumbered**
               When doing debugging dumps, suppress instruction numbers and
               address output.  This makes it more feasible to use diff on
               debugging dumps for compiler invocations with different
               options, in particular with and without **-g**.
    
           **-fdump-unnumbered-links**
               When doing debugging dumps (see **-d** option above), suppress
               instruction numbers for the links to the previous and next
               instructions in a sequence.
    
           **-fdump-ipa-**_switch_
           **-fdump-ipa-**_switch_**-**_options_
               Control the dumping at various stages of inter-procedural
               analysis language tree to a file.  The file name is generated
               by appending a switch specific suffix to the source file name,
               and the file is created in the same directory as the output
               file.  The following dumps are possible:
    
               **all** Enables all inter-procedural analysis dumps.
    
               **cgraph**
                   Dumps information about call-graph optimization, unused
                   function removal, and inlining decisions.
    
               **inline**
                   Dump after function inlining.
    
               Additionally, the options **-optimized** , **-missed** , **-note** , and **-all**
               can be provided, with the same meaning as for **-fopt-info** ,
               defaulting to **-optimized**.
    
               For example, **-fdump-ipa-inline-optimized-missed** will emit
               information on callsites that were inlined, along with
               callsites that were not inlined.
    
               By default, the dump will contain messages about successful
               optimizations (equivalent to **-optimized**) together with low-
               level details about the analysis.
    
           **-fdump-lang-all**
           **-fdump-lang-**_switch_
           **-fdump-lang-**_switch_**-**_options_
           **-fdump-lang-**_switch_**-**_options_**=**_filename_
               Control the dumping of language-specific information.  The
               _options_ and _filename_ portions behave as described in the
               **-fdump-tree** option.  The following _switch_ values are accepted:
    
               **all** Enable all language-specific dumps.
    
               **class**
                   Dump class hierarchy information.  Virtual table
                   information is emitted unless '**slim** ' is specified.  This
                   option is applicable to C++ only.
    
               **raw** Dump the raw internal tree data.  This option is
                   applicable to C++ only.
    
           **-fdump-passes**
               Print on _stderr_ the list of optimization passes that are
               turned on and off by the current command-line options.
    
           **-fdump-statistics-**_option_
               Enable and control dumping of pass statistics in a separate
               file.  The file name is generated by appending a suffix ending
               in **.statistics** to the source file name, and the file is
               created in the same directory as the output file.  If the
               **-**_option_ form is used, **-stats** causes counters to be summed over
               the whole compilation unit while **-details** dumps every event as
               the passes generate them.  The default with no option is to
               sum counters for each function compiled.
    
           **-fdump-tree-all**
           **-fdump-tree-**_switch_
           **-fdump-tree-**_switch_**-**_options_
           **-fdump-tree-**_switch_**-**_options_**=**_filename_
               Control the dumping at various stages of processing the
               intermediate language tree to a file.  If the **-**_options_ form is
               used, _options_ is a list of **-** separated options which control
               the details of the dump.  Not all options are applicable to
               all dumps; those that are not meaningful are ignored.  The
               following options are available
    
               **address**
                   Print the address of each node.  Usually this is not
                   meaningful as it changes according to the environment and
                   source file.  Its primary use is for tying up a dump file
                   with a debug environment.
    
               **asmname**
                   If "DECL_ASSEMBLER_NAME" has been set for a given decl,
                   use that in the dump instead of "DECL_NAME".  Its primary
                   use is ease of use working backward from mangled names in
                   the assembly file.
    
               **slim**
                   When dumping front-end intermediate representations,
                   inhibit dumping of members of a scope or body of a
                   function merely because that scope has been reached.  Only
                   dump such items when they are directly reachable by some
                   other path.
    
                   When dumping pretty-printed trees, this option inhibits
                   dumping the bodies of control structures.
    
                   When dumping RTL, print the RTL in slim (condensed) form
                   instead of the default LISP-like representation.
    
               **raw** Print a raw representation of the tree.  By default, trees
                   are pretty-printed into a C-like representation.
    
               **details**
                   Enable more detailed dumps (not honored by every dump
                   option). Also include information from the optimization
                   passes.
    
               **stats**
                   Enable dumping various statistics about the pass (not
                   honored by every dump option).
    
               **blocks**
                   Enable showing basic block boundaries (disabled in raw
                   dumps).
    
               **graph**
                   For each of the other indicated dump files
                   (**-fdump-rtl-**_pass_), dump a representation of the control
                   flow graph suitable for viewing with GraphViz to
                   _file.passid.pass.dot_.  Each function in the file is
                   pretty-printed as a subgraph, so that GraphViz can render
                   them all in a single plot.
    
                   This option currently only works for RTL dumps, and the
                   RTL is always dumped in slim form.
    
               **vops**
                   Enable showing virtual operands for every statement.
    
               **lineno**
                   Enable showing line numbers for statements.
    
               **uid** Enable showing the unique ID ("DECL_UID") for each
                   variable.
    
               **verbose**
                   Enable showing the tree dump for each statement.
    
               **eh** Enable showing the EH region number holding each
                   statement.
    
               **scev**
                   Enable showing scalar evolution analysis details.
    
               **optimized**
                   Enable showing optimization information (only available in
                   certain passes).
    
               **missed**
                   Enable showing missed optimization information (only
                   available in certain passes).
    
               **note**
                   Enable other detailed optimization information (only
                   available in certain passes).
    
               **all** Turn on all options, except **raw** , **slim** , **verbose** and **lineno**.
    
               **optall**
                   Turn on all optimization options, i.e., **optimized** , **missed** ,
                   and **note**.
    
               To determine what tree dumps are available or find the dump
               for a pass of interest follow the steps below.
    
               1.  Invoke GCC with **-fdump-passes** and in the _stderr_ output
                   look for a code that corresponds to the pass you are
                   interested in.  For example, the codes "tree-evrp",
                   "tree-vrp1", and "tree-vrp2" correspond to the three Value
                   Range Propagation passes.  The number at the end
                   distinguishes distinct invocations of the same pass.
    
               2.  To enable the creation of the dump file, append the pass
                   code to the **-fdump-** option prefix and invoke GCC with it.
                   For example, to enable the dump from the Early Value Range
                   Propagation pass, invoke GCC with the **-fdump-tree-evrp**
                   option.  Optionally, you may specify the name of the dump
                   file.  If you don't specify one, GCC creates as described
                   below.
    
               3.  Find the pass dump in a file whose name is composed of
                   three components separated by a period: the name of the
                   source file GCC was invoked to compile, a numeric suffix
                   indicating the pass number followed by the letter **t** for
                   tree passes (and the letter **r** for RTL passes), and finally
                   the pass code.  For example, the Early VRP pass dump might
                   be in a file named _myfile.c.038t.evrp_ in the current
                   working directory.  Note that the numeric codes are not
                   stable and may change from one version of GCC to another.
    
           **-fopt-info**
           **-fopt-info-**_options_
           **-fopt-info-**_options_**=**_filename_
               Controls optimization dumps from various optimization passes.
               If the **-**_options_ form is used, _options_ is a list of **-** separated
               option keywords to select the dump details and optimizations.
    
               The _options_ can be divided into three groups:
    
               1.  options describing what kinds of messages should be
                   emitted,
    
               2.  options describing the verbosity of the dump, and
    
               3.  options describing which optimizations should be included.
    
               The options from each group can be freely mixed as they are
               non-overlapping. However, in case of any conflicts, the later
               options override the earlier options on the command line.
    
               The following options control which kinds of messages should
               be emitted:
    
               **optimized**
                   Print information when an optimization is successfully
                   applied. It is up to a pass to decide which information is
                   relevant. For example, the vectorizer passes print the
                   source location of loops which are successfully
                   vectorized.
    
               **missed**
                   Print information about missed optimizations. Individual
                   passes control which information to include in the output.
    
               **note**
                   Print verbose information about optimizations, such as
                   certain transformations, more detailed messages about
                   decisions etc.
    
               **all** Print detailed optimization information. This includes
                   **optimized** , **missed** , and **note**.
    
               The following option controls the dump verbosity:
    
               **internals**
                   By default, only "high-level" messages are emitted. This
                   option enables additional, more detailed, messages, which
                   are likely to only be of interest to GCC developers.
    
               One or more of the following option keywords can be used to
               describe a group of optimizations:
    
               **ipa** Enable dumps from all interprocedural optimizations.
    
               **loop**
                   Enable dumps from all loop optimizations.
    
               **inline**
                   Enable dumps from all inlining optimizations.
    
               **omp** Enable dumps from all OMP (Offloading and Multi
                   Processing) optimizations.
    
               **vec** Enable dumps from all vectorization optimizations.
    
               **optall**
                   Enable dumps from all optimizations. This is a superset of
                   the optimization groups listed above.
    
               If _options_ is omitted, it defaults to **optimized-optall** , which
               means to dump messages about successful optimizations from all
               the passes, omitting messages that are treated as "internals".
    
               If the _filename_ is provided, then the dumps from all the
               applicable optimizations are concatenated into the _filename_.
               Otherwise the dump is output onto _stderr_. Though multiple
               **-fopt-info** options are accepted, only one of them can include
               a _filename_. If other filenames are provided then all but the
               first such option are ignored.
    
               Note that the output _filename_ is overwritten in case of
               multiple translation units. If a combined output from multiple
               translation units is desired, _stderr_ should be used instead.
    
               In the following example, the optimization info is output to
               _stderr_ :
    
                       gcc -O3 -fopt-info
    
               This example:
    
                       gcc -O3 -fopt-info-missed=missed.all
    
               outputs missed optimization report from all the passes into
               _missed.all_ , and this one:
    
                       gcc -O2 -ftree-vectorize -fopt-info-vec-missed
    
               prints information about missed optimization opportunities
               from vectorization passes on _stderr_.  Note that
               **-fopt-info-vec-missed** is equivalent to **-fopt-info-missed-vec**.
               The order of the optimization group names and message types
               listed after **-fopt-info** does not matter.
    
               As another example,
    
                       gcc -O3 -fopt-info-inline-optimized-missed=inline.txt
    
               outputs information about missed optimizations as well as
               optimized locations from all the inlining passes into
               _inline.txt_.
    
               Finally, consider:
    
                       gcc -fopt-info-vec-missed=vec.miss -fopt-info-loop-optimized=loop.opt
    
               Here the two output filenames _vec.miss_ and _loop.opt_ are in
               conflict since only one output file is allowed. In this case,
               only the first option takes effect and the subsequent options
               are ignored. Thus only _vec.miss_ is produced which contains
               dumps from the vectorizer about missed opportunities.
    
           **-fsave-optimization-record**
               Write a SRCFILE.opt-record.json.gz file detailing what
               optimizations were performed, for those optimizations that
               support **-fopt-info**.
    
               This option is experimental and the format of the data within
               the compressed JSON file is subject to change.
    
               It is roughly equivalent to a machine-readable version of
               **-fopt-info-all** , as a collection of messages with source file,
               line number and column number, with the following additional
               data for each message:
    
               *   the execution count of the code being optimized, along
                   with metadata about whether this was from actual profile
                   data, or just an estimate, allowing consumers to
                   prioritize messages by code hotness,
    
               *   the function name of the code being optimized, where
                   applicable,
    
               *   the "inlining chain" for the code being optimized, so that
                   when a function is inlined into several different places
                   (which might themselves be inlined), the reader can
                   distinguish between the copies,
    
               *   objects identifying those parts of the message that refer
                   to expressions, statements or symbol-table nodes, which of
                   these categories they are, and, when available, their
                   source code location,
    
               *   the GCC pass that emitted the message, and
    
               *   the location in GCC's own code from which the message was
                   emitted
    
               Additionally, some messages are logically nested within other
               messages, reflecting implementation details of the
               optimization passes.
    
           **-fsched-verbose=**_n_
               On targets that use instruction scheduling, this option
               controls the amount of debugging output the scheduler prints
               to the dump files.
    
               For _n_ greater than zero, **-fsched-verbose** outputs the same
               information as **-fdump-rtl-sched1** and **-fdump-rtl-sched2**.  For _n_
               greater than one, it also output basic block probabilities,
               detailed ready list information and unit/insn info.  For _n_
               greater than two, it includes RTL at abort point, control-flow
               and regions info.  And for _n_ over four, **-fsched-verbose** also
               includes dependence info.
    
           **-fenable-**_kind_**-**_pass_
           **-fdisable-**_kind_**-**_pass_**=**_range-list_
               This is a set of options that are used to explicitly
               disable/enable optimization passes.  These options are
               intended for use for debugging GCC.  Compiler users should use
               regular options for enabling/disabling passes instead.
    
               **-fdisable-ipa-**_pass_
                   Disable IPA pass _pass_. _pass_ is the pass name.  If the same
                   pass is statically invoked in the compiler multiple times,
                   the pass name should be appended with a sequential number
                   starting from 1.
    
               **-fdisable-rtl-**_pass_
               **-fdisable-rtl-**_pass_**=**_range-list_
                   Disable RTL pass _pass_.  _pass_ is the pass name.  If the
                   same pass is statically invoked in the compiler multiple
                   times, the pass name should be appended with a sequential
                   number starting from 1.  _range-list_ is a comma-separated
                   list of function ranges or assembler names.  Each range is
                   a number pair separated by a colon.  The range is
                   inclusive in both ends.  If the range is trivial, the
                   number pair can be simplified as a single number.  If the
                   function's call graph node's _uid_ falls within one of the
                   specified ranges, the _pass_ is disabled for that function.
                   The _uid_ is shown in the function header of a dump file,
                   and the pass names can be dumped by using option
                   **-fdump-passes**.
    
               **-fdisable-tree-**_pass_
               **-fdisable-tree-**_pass_**=**_range-list_
                   Disable tree pass _pass_.  See **-fdisable-rtl** for the
                   description of option arguments.
    
               **-fenable-ipa-**_pass_
                   Enable IPA pass _pass_.  _pass_ is the pass name.  If the same
                   pass is statically invoked in the compiler multiple times,
                   the pass name should be appended with a sequential number
                   starting from 1.
    
               **-fenable-rtl-**_pass_
               **-fenable-rtl-**_pass_**=**_range-list_
                   Enable RTL pass _pass_.  See **-fdisable-rtl** for option
                   argument description and examples.
    
               **-fenable-tree-**_pass_
               **-fenable-tree-**_pass_**=**_range-list_
                   Enable tree pass _pass_.  See **-fdisable-rtl** for the
                   description of option arguments.
    
               Here are some examples showing uses of these options.
    
                       # disable ccp1 for all functions
                          -fdisable-tree-ccp1
                       # disable complete unroll for function whose cgraph node uid is 1
                          -fenable-tree-cunroll=1
                       # disable gcse2 for functions at the following ranges [1,1],
                       # [300,400], and [400,1000]
                       # disable gcse2 for functions foo and foo2
                          -fdisable-rtl-gcse2=foo,foo2
                       # disable early inlining
                          -fdisable-tree-einline
                       # disable ipa inlining
                          -fdisable-ipa-inline
                       # enable tree full unroll
                          -fenable-tree-unroll
    
           **-fchecking**
           **-fchecking=**_n_
               Enable internal consistency checking.  The default depends on
               the compiler configuration.  **-fchecking=2** enables further
               internal consistency checking that might affect code
               generation.
    
           **-frandom-seed=**_string_
               This option provides a seed that GCC uses in place of random
               numbers in generating certain symbol names that have to be
               different in every compiled file.  It is also used to place
               unique stamps in coverage data files and the object files that
               produce them.  You can use the **-frandom-seed** option to produce
               reproducibly identical object files.
    
               The _string_ can either be a number (decimal, octal or hex) or
               an arbitrary string (in which case it's converted to a number
               by computing CRC32).
    
               The _string_ should be different for every file you compile.
    
           **-save-temps**
           **-save-temps=cwd**
               Store the usual "temporary" intermediate files permanently;
               place them in the current directory and name them based on the
               source file.  Thus, compiling _foo.c_ with **-c -save-temps**
               produces files _foo.i_ and _foo.s_ , as well as _foo.o_.  This
               creates a preprocessed _foo.i_ output file even though the
               compiler now normally uses an integrated preprocessor.
    
               When used in combination with the **-x** command-line option,
               **-save-temps** is sensible enough to avoid over writing an input
               source file with the same extension as an intermediate file.
               The corresponding intermediate file may be obtained by
               renaming the source file before using **-save-temps**.
    
               If you invoke GCC in parallel, compiling several different
               source files that share a common base name in different
               subdirectories or the same source file compiled for multiple
               output destinations, it is likely that the different parallel
               compilers will interfere with each other, and overwrite the
               temporary files.  For instance:
    
                       gcc -save-temps -o outdir1/foo.o indir1/foo.c&
                       gcc -save-temps -o outdir2/foo.o indir2/foo.c&
    
               may result in _foo.i_ and _foo.o_ being written to simultaneously
               by both compilers.
    
           **-save-temps=obj**
               Store the usual "temporary" intermediate files permanently.
               If the **-o** option is used, the temporary files are based on the
               object file.  If the **-o** option is not used, the
               **-save-temps=obj** switch behaves like **-save-temps**.
    
               For example:
    
                       gcc -save-temps=obj -c foo.c
                       gcc -save-temps=obj -c bar.c -o dir/xbar.o
                       gcc -save-temps=obj foobar.c -o dir2/yfoobar
    
               creates _foo.i_ , _foo.s_ , _dir/xbar.i_ , _dir/xbar.s_ , _dir2/yfoobar.i_ ,
               _dir2/yfoobar.s_ , and _dir2/yfoobar.o_.
    
           **-time**[**=**_file_]
               Report the CPU time taken by each subprocess in the
               compilation sequence.  For C source files, this is the
               compiler proper and assembler (plus the linker if linking is
               done).
    
               Without the specification of an output file, the output looks
               like this:
    
                       # cc1 0.12 0.01
                       # as 0.00 0.01
    
               The first number on each line is the "user time", that is time
               spent executing the program itself.  The second number is
               "system time", time spent executing operating system routines
               on behalf of the program.  Both numbers are in seconds.
    
               With the specification of an output file, the output is
               appended to the named file, and it looks like this:
    
                       0.12 0.01 cc1 <options>
                       0.00 0.01 as <options>
    
               The "user time" and the "system time" are moved before the
               program name, and the options passed to the program are
               displayed, so that one can later tell what file was being
               compiled, and with which options.
    
           **-fdump-final-insns**[**=**_file_]
               Dump the final internal representation (RTL) to _file_.  If the
               optional argument is omitted (or if _file_ is "."), the name of
               the dump file is determined by appending ".gkd" to the
               compilation output file name.
    
           **-fcompare-debug**[**=**_opts_]
               If no error occurs during compilation, run the compiler a
               second time, adding _opts_ and **-fcompare-debug-second** to the
               arguments passed to the second compilation.  Dump the final
               internal representation in both compilations, and print an
               error if they differ.
    
               If the equal sign is omitted, the default **-gtoggle** is used.
    
               The environment variable **GCC_COMPARE_DEBUG** , if defined, non-
               empty and nonzero, implicitly enables **-fcompare-debug**.  If
               **GCC_COMPARE_DEBUG** is defined to a string starting with a dash,
               then it is used for _opts_ , otherwise the default **-gtoggle** is
               used.
    
               **-fcompare-debug=** , with the equal sign but without _opts_ , is
               equivalent to **-fno-compare-debug** , which disables the dumping
               of the final representation and the second compilation,
               preventing even **GCC_COMPARE_DEBUG** from taking effect.
    
               To verify full coverage during **-fcompare-debug** testing, set
               **GCC_COMPARE_DEBUG** to say **-fcompare-debug-not-overridden** , which
               GCC rejects as an invalid option in any actual compilation
               (rather than preprocessing, assembly or linking).  To get just
               a warning, setting **GCC_COMPARE_DEBUG** to **-w%n-fcompare-debug**
               **not overridden** will do.
    
           **-fcompare-debug-second**
               This option is implicitly passed to the compiler for the
               second compilation requested by **-fcompare-debug** , along with
               options to silence warnings, and omitting other options that
               would cause the compiler to produce output to files or to
               standard output as a side effect.  Dump files and preserved
               temporary files are renamed so as to contain the ".gk"
               additional extension during the second compilation, to avoid
               overwriting those generated by the first.
    
               When this option is passed to the compiler driver, it causes
               the _first_ compilation to be skipped, which makes it useful for
               little other than debugging the compiler proper.
    
           **-gtoggle**
               Turn off generation of debug info, if leaving out this option
               generates it, or turn it on at level 2 otherwise.  The
               position of this argument in the command line does not matter;
               it takes effect after all other options are processed, and it
               does so only once, no matter how many times it is given.  This
               is mainly intended to be used with **-fcompare-debug**.
    
           **-fvar-tracking-assignments-toggle**
               Toggle **-fvar-tracking-assignments** , in the same way that
               **-gtoggle** toggles **-g**.
    
           **-Q** Makes the compiler print out each function name as it is
               compiled, and print some statistics about each pass when it
               finishes.
    
           **-ftime-report**
               Makes the compiler print some statistics about the time
               consumed by each pass when it finishes.
    
           **-ftime-report-details**
               Record the time consumed by infrastructure parts separately
               for each pass.
    
           **-fira-verbose=**_n_
               Control the verbosity of the dump file for the integrated
               register allocator.  The default value is 5.  If the value _n_
               is greater or equal to 10, the dump output is sent to stderr
               using the same format as _n_ minus 10.
    
           **-flto-report**
               Prints a report with internal details on the workings of the
               link-time optimizer.  The contents of this report vary from
               version to version.  It is meant to be useful to GCC
               developers when processing object files in LTO mode (via
               **-flto**).
    
               Disabled by default.
    
           **-flto-report-wpa**
               Like **-flto-report** , but only print for the WPA phase of Link
               Time Optimization.
    
           **-fmem-report**
               Makes the compiler print some statistics about permanent
               memory allocation when it finishes.
    
           **-fmem-report-wpa**
               Makes the compiler print some statistics about permanent
               memory allocation for the WPA phase only.
    
           **-fpre-ipa-mem-report**
           **-fpost-ipa-mem-report**
               Makes the compiler print some statistics about permanent
               memory allocation before or after interprocedural
               optimization.
    
           **-fprofile-report**
               Makes the compiler print some statistics about consistency of
               the (estimated) profile and effect of individual passes.
    
           **-fstack-usage**
               Makes the compiler output stack usage information for the
               program, on a per-function basis.  The filename for the dump
               is made by appending _.su_ to the _auxname_.  _auxname_ is generated
               from the name of the output file, if explicitly specified and
               it is not an executable, otherwise it is the basename of the
               source file.  An entry is made up of three fields:
    
               *   The name of the function.
    
               *   A number of bytes.
    
               *   One or more qualifiers: "static", "dynamic", "bounded".
    
               The qualifier "static" means that the function manipulates the
               stack statically: a fixed number of bytes are allocated for
               the frame on function entry and released on function exit; no
               stack adjustments are otherwise made in the function.  The
               second field is this fixed number of bytes.
    
               The qualifier "dynamic" means that the function manipulates
               the stack dynamically: in addition to the static allocation
               described above, stack adjustments are made in the body of the
               function, for example to push/pop arguments around function
               calls.  If the qualifier "bounded" is also present, the amount
               of these adjustments is bounded at compile time and the second
               field is an upper bound of the total amount of stack used by
               the function.  If it is not present, the amount of these
               adjustments is not bounded at compile time and the second
               field only represents the bounded part.
    
           **-fstats**
               Emit statistics about front-end processing at the end of the
               compilation.  This option is supported only by the C++ front
               end, and the information is generally only useful to the G++
               development team.
    
           **-fdbg-cnt-list**
               Print the name and the counter upper bound for all debug
               counters.
    
           **-fdbg-cnt=**_counter-value-list_
               Set the internal debug counter lower and upper bound.
               _counter-value-list_ is a comma-separated list of
               _name_ :_lower_bound_ :_upper_bound_ tuples which sets the lower and
               the upper bound of each debug counter _name_.  The _lower_bound_
               is optional and is zero initialized if not set.  All debug
               counters have the initial upper bound of "UINT_MAX"; thus
               "dbg_cnt" returns true always unless the upper bound is set by
               this option.  For example, with
               **-fdbg-cnt=dce:2:4,tail_call:10** , "dbg_cnt(dce)" returns true
               only for third and fourth invocation.  For
               "dbg_cnt(tail_call)" true is returned for first 10
               invocations.
    
           **-print-file-name=**_library_
               Print the full absolute name of the library file _library_ that
               would be used when linking---and don't do anything else.  With
               this option, GCC does not compile or link anything; it just
               prints the file name.
    
           **-print-multi-directory**
               Print the directory name corresponding to the multilib
               selected by any other switches present in the command line.
               This directory is supposed to exist in **GCC_EXEC_PREFIX**.
    
           **-print-multi-lib**
               Print the mapping from multilib directory names to compiler
               switches that enable them.  The directory name is separated
               from the switches by **;** , and each switch starts with an **@**
               instead of the **-** , without spaces between multiple switches.
               This is supposed to ease shell processing.
    
           **-print-multi-os-directory**
               Print the path to OS libraries for the selected multilib,
               relative to some _lib_ subdirectory.  If OS libraries are
               present in the _lib_ subdirectory and no multilibs are used,
               this is usually just _._ , if OS libraries are present in
               _libsuffix_ sibling directories this prints e.g. _../lib64_ ,
               _../lib_ or _../lib32_ , or if OS libraries are present in
               _lib/subdir_ subdirectories it prints e.g. _amd64_ , _sparcv9_ or
               _ev6_.
    
           **-print-multiarch**
               Print the path to OS libraries for the selected multiarch,
               relative to some _lib_ subdirectory.
    
           **-print-prog-name=**_program_
               Like **-print-file-name** , but searches for a program such as **cpp**.
    
           **-print-libgcc-file-name**
               Same as **-print-file-name=libgcc.a**.
    
               This is useful when you use **-nostdlib** or **-nodefaultlibs** but
               you do want to link with _libgcc.a_.  You can do:
    
                       gcc -nostdlib <files>... `gcc -print-libgcc-file-name`
    
           **-print-search-dirs**
               Print the name of the configured installation directory and a
               list of program and library directories **gcc** searches---and
               don't do anything else.
    
               This is useful when **gcc** prints the error message **installation**
               **problem, cannot exec cpp0: No such file or directory**.  To
               resolve this you either need to put _cpp0_ and the other
               compiler components where **gcc** expects to find them, or you can
               set the environment variable **GCC_EXEC_PREFIX** to the directory
               where you installed them.  Don't forget the trailing **/**.
    
           **-print-sysroot**
               Print the target sysroot directory that is used during
               compilation.  This is the target sysroot specified either at
               configure time or using the **--sysroot** option, possibly with an
               extra suffix that depends on compilation options.  If no
               target sysroot is specified, the option prints nothing.
    
           **-print-sysroot-headers-suffix**
               Print the suffix added to the target sysroot when searching
               for headers, or give an error if the compiler is not
               configured with such a suffix---and don't do anything else.
    
           **-dumpmachine**
               Print the compiler's target machine (for example,
               **i686-pc-linux-gnu**)---and don't do anything else.
    
           **-dumpversion**
               Print the compiler version (for example, 3.0, 6.3.0 or
               7)---and don't do anything else.  This is the compiler version
               used in filesystem paths and specs. Depending on how the
               compiler has been configured it can be just a single number
               (major version), two numbers separated by a dot (major and
               minor version) or three numbers separated by dots (major,
               minor and patchlevel version).
    
           **-dumpfullversion**
               Print the full compiler version---and don't do anything else.
               The output is always three numbers separated by dots, major,
               minor and patchlevel version.
    
           **-dumpspecs**
               Print the compiler's built-in specs---and don't do anything
               else.  (This is used when GCC itself is being built.)
    
       **Machine-Dependent Options**
           Each target machine supported by GCC can have its own
           options---for example, to allow you to compile for a particular
           processor variant or ABI, or to control optimizations specific to
           that machine.  By convention, the names of machine-specific
           options start with **-m**.
    
           Some configurations of the compiler also support additional
           target-specific options, usually for compatibility with other
           compilers on the same platform.
    
           _AArch64 Options_
    
           These options are defined for AArch64 implementations:
    
           **-mabi=**_name_
               Generate code for the specified data model.  Permissible
               values are **ilp32** for SysV-like data model where int, long int
               and pointers are 32 bits, and **lp64** for SysV-like data model
               where int is 32 bits, but long int and pointers are 64 bits.
    
               The default depends on the specific target configuration.
               Note that the LP64 and ILP32 ABIs are not link-compatible; you
               must compile your entire program with the same ABI, and link
               with a compatible set of libraries.
    
           **-mbig-endian**
               Generate big-endian code.  This is the default when GCC is
               configured for an **aarch64_be-*-*** target.
    
           **-mgeneral-regs-only**
               Generate code which uses only the general-purpose registers.
               This will prevent the compiler from using floating-point and
               Advanced SIMD registers but will not impose any restrictions
               on the assembler.
    
           **-mlittle-endian**
               Generate little-endian code.  This is the default when GCC is
               configured for an **aarch64-*-*** but not an **aarch64_be-*-***
               target.
    
           **-mcmodel=tiny**
               Generate code for the tiny code model.  The program and its
               statically defined symbols must be within 1MB of each other.
               Programs can be statically or dynamically linked.
    
           **-mcmodel=small**
               Generate code for the small code model.  The program and its
               statically defined symbols must be within 4GB of each other.
               Programs can be statically or dynamically linked.  This is the
               default code model.
    
           **-mcmodel=large**
               Generate code for the large code model.  This makes no
               assumptions about addresses and sizes of sections.  Programs
               can be statically linked only.
    
           **-mstrict-align**
           **-mno-strict-align**
               Avoid or allow generating memory accesses that may not be
               aligned on a natural object boundary as described in the
               architecture specification.
    
           **-momit-leaf-frame-pointer**
           **-mno-omit-leaf-frame-pointer**
               Omit or keep the frame pointer in leaf functions.  The former
               behavior is the default.
    
           **-mstack-protector-guard=**_guard_
           **-mstack-protector-guard-reg=**_reg_
           **-mstack-protector-guard-offset=**_offset_
               Generate stack protection code using canary at _guard_.
               Supported locations are **global** for a global canary or **sysreg**
               for a canary in an appropriate system register.
    
               With the latter choice the options
               **-mstack-protector-guard-reg=**_reg_ and
               **-mstack-protector-guard-offset=**_offset_ furthermore specify
               which system register to use as base register for reading the
               canary, and from what offset from that base register. There is
               no default register or offset as this is entirely for use
               within the Linux kernel.
    
           **-mstack-protector-guard=**_guard_
           **-mstack-protector-guard-reg=**_reg_
           **-mstack-protector-guard-offset=**_offset_
               Generate stack protection code using canary at _guard_.
               Supported locations are **global** for a global canary or **sysreg**
               for a canary in an appropriate system register.
    
               With the latter choice the options
               **-mstack-protector-guard-reg=**_reg_ and
               **-mstack-protector-guard-offset=**_offset_ furthermore specify
               which system register to use as base register for reading the
               canary, and from what offset from that base register. There is
               no default register or offset as this is entirely for use
               within the Linux kernel.
    
           **-mtls-dialect=desc**
               Use TLS descriptors as the thread-local storage mechanism for
               dynamic accesses of TLS variables.  This is the default.
    
           **-mtls-dialect=traditional**
               Use traditional TLS as the thread-local storage mechanism for
               dynamic accesses of TLS variables.
    
           **-mtls-size=**_size_
               Specify bit size of immediate TLS offsets.  Valid values are
               12, 24, 32, 48.  This option requires binutils 2.26 or newer.
    
           **-mfix-cortex-a53-835769**
           **-mno-fix-cortex-a53-835769**
               Enable or disable the workaround for the ARM Cortex-A53
               erratum number 835769.  This involves inserting a NOP
               instruction between memory instructions and 64-bit integer
               multiply-accumulate instructions.
    
           **-mfix-cortex-a53-843419**
           **-mno-fix-cortex-a53-843419**
               Enable or disable the workaround for the ARM Cortex-A53
               erratum number 843419.  This erratum workaround is made at
               link time and this will only pass the corresponding flag to
               the linker.
    
           **-mlow-precision-recip-sqrt**
           **-mno-low-precision-recip-sqrt**
               Enable or disable the reciprocal square root approximation.
               This option only has an effect if **-ffast-math** or
               **-funsafe-math-optimizations** is used as well.  Enabling this
               reduces precision of reciprocal square root results to about
               16 bits for single precision and to 32 bits for double
               precision.
    
           **-mlow-precision-sqrt**
           **-mno-low-precision-sqrt**
               Enable or disable the square root approximation.  This option
               only has an effect if **-ffast-math** or
               **-funsafe-math-optimizations** is used as well.  Enabling this
               reduces precision of square root results to about 16 bits for
               single precision and to 32 bits for double precision.  If
               enabled, it implies **-mlow-precision-recip-sqrt**.
    
           **-mlow-precision-div**
           **-mno-low-precision-div**
               Enable or disable the division approximation.  This option
               only has an effect if **-ffast-math** or
               **-funsafe-math-optimizations** is used as well.  Enabling this
               reduces precision of division results to about 16 bits for
               single precision and to 32 bits for double precision.
    
           **-mtrack-speculation**
           **-mno-track-speculation**
               Enable or disable generation of additional code to track
               speculative execution through conditional branches.  The
               tracking state can then be used by the compiler when expanding
               calls to "__builtin_speculation_safe_copy" to permit a more
               efficient code sequence to be generated.
    
           **-moutline-atomics**
           **-mno-outline-atomics**
               Enable or disable calls to out-of-line helpers to implement
               atomic operations.  These helpers will, at runtime, determine
               if the LSE instructions from ARMv8.1-A can be used; if not,
               they will use the load/store-exclusive instructions that are
               present in the base ARMv8.0 ISA.
    
               This option is only applicable when compiling for the base
               ARMv8.0 instruction set.  If using a later revision, e.g.
               **-march=armv8.1-a** or **-march=armv8-a+lse** , the ARMv8.1-Atomics
               instructions will be used directly.  The same applies when
               using **-mcpu=** when the selected cpu supports the **lse** feature.
    
           **-march=**_name_
               Specify the name of the target architecture and, optionally,
               one or more feature modifiers.  This option has the form
               **-march=**_arch_{**+**[**no**]_feature_}*.
    
               The permissible values for _arch_ are **armv8-a** , **armv8.1-a** ,
               **armv8.2-a** , **armv8.3-a** , **armv8.4-a** , **armv8.5-a** or _native_.
    
               The value **armv8.5-a** implies **armv8.4-a** and enables compiler
               support for the ARMv8.5-A architecture extensions.
    
               The value **armv8.4-a** implies **armv8.3-a** and enables compiler
               support for the ARMv8.4-A architecture extensions.
    
               The value **armv8.3-a** implies **armv8.2-a** and enables compiler
               support for the ARMv8.3-A architecture extensions.
    
               The value **armv8.2-a** implies **armv8.1-a** and enables compiler
               support for the ARMv8.2-A architecture extensions.
    
               The value **armv8.1-a** implies **armv8-a** and enables compiler
               support for the ARMv8.1-A architecture extension.  In
               particular, it enables the **+crc** , **+lse** , and **+rdma** features.
    
               The value **native** is available on native AArch64 GNU/Linux and
               causes the compiler to pick the architecture of the host
               system.  This option has no effect if the compiler is unable
               to recognize the architecture of the host system,
    
               The permissible values for _feature_ are listed in the sub-
               section on **aarch64-feature-modifiers,,-march and -mcpu Feature**
               **Modifiers**.  Where conflicting feature modifiers are specified,
               the right-most feature is used.
    
               GCC uses _name_ to determine what kind of instructions it can
               emit when generating assembly code.  If **-march** is specified
               without either of **-mtune** or **-mcpu** also being specified, the
               code is tuned to perform well across a range of target
               processors implementing the target architecture.
    
           **-mtune=**_name_
               Specify the name of the target processor for which GCC should
               tune the performance of the code.  Permissible values for this
               option are: **generic** , **cortex-a35** , **cortex-a53** , **cortex-a55** ,
               **cortex-a57** , **cortex-a72** , **cortex-a73** , **cortex-a75** , **cortex-a76** ,
               **ares** , **exynos-m1** , **emag** , **falkor** , **neoverse-e1** , **neoverse-n1** ,
               **neoverse-n2** , **neoverse-v1** , **neoverse-512tvb** , **qdf24xx** , **saphira** ,
               **phecda** , **xgene1** , **vulcan** , **octeontx** , **octeontx81** ,  **octeontx83** ,
               **a64fx** , **thunderx** , **thunderxt88** , **thunderxt88p1** , **thunderxt81** ,
               **tsv110** , **thunderxt83** , **thunderx2t99** , **zeus** ,
               **cortex-a57.cortex-a53** , **cortex-a72.cortex-a53** ,
               **cortex-a73.cortex-a35** , **cortex-a73.cortex-a53** ,
               **cortex-a75.cortex-a55** , **cortex-a76.cortex-a55 native**.
    
               The values **cortex-a57.cortex-a53** , **cortex-a72.cortex-a53** ,
               **cortex-a73.cortex-a35** , **cortex-a73.cortex-a53** ,
               **cortex-a75.cortex-a55** , **cortex-a76.cortex-a55** specify that GCC
               should tune for a big.LITTLE system.
    
               The value **neoverse-512tvb** specifies that GCC should tune for
               Neoverse cores that (a) implement SVE and (b) have a total
               vector bandwidth of 512 bits per cycle.  In other words, the
               option tells GCC to tune for Neoverse cores that can execute 4
               128-bit Advanced SIMD arithmetic instructions a cycle and that
               can execute an equivalent number of SVE arithmetic
               instructions per cycle (2 for 256-bit SVE, 4 for 128-bit SVE).
               This is more general than tuning for a specific core like
               Neoverse V1 but is more specific than the default tuning
               described below.
    
               Additionally on native AArch64 GNU/Linux systems the value
               **native** tunes performance to the host system.  This option has
               no effect if the compiler is unable to recognize the processor
               of the host system.
    
               Where none of **-mtune=** , **-mcpu=** or **-march=** are specified, the
               code is tuned to perform well across a range of target
               processors.
    
               This option cannot be suffixed by feature modifiers.
    
           **-mcpu=**_name_
               Specify the name of the target processor, optionally suffixed
               by one or more feature modifiers.  This option has the form
               **-mcpu=**_cpu_{**+**[**no**]_feature_}*, where the permissible values for _cpu_
               are the same as those available for **-mtune**.  The permissible
               values for _feature_ are documented in the sub-section on
               **aarch64-feature-modifiers,,-march and -mcpu Feature Modifiers**.
               Where conflicting feature modifiers are specified, the right-
               most feature is used.
    
               GCC uses _name_ to determine what kind of instructions it can
               emit when generating assembly code (as if by **-march**) and to
               determine the target processor for which to tune for
               performance (as if by **-mtune**).  Where this option is used in
               conjunction with **-march** or **-mtune** , those options take
               precedence over the appropriate part of this option.
    
               **-mcpu=neoverse-512tvb** is special in that it does not refer to
               a specific core, but instead refers to all Neoverse cores that
               (a) implement SVE and (b) have a total vector bandwidth of 512
               bits a cycle.  Unless overridden by **-march** ,
               **-mcpu=neoverse-512tvb** generates code that can run on a
               Neoverse V1 core, since Neoverse V1 is the first Neoverse core
               with these properties.  Unless overridden by **-mtune** ,
               **-mcpu=neoverse-512tvb** tunes code in the same way as for
               **-mtune=neoverse-512tvb**.
    
           **-moverride=**_string_
               Override tuning decisions made by the back-end in response to
               a **-mtune=** switch.  The syntax, semantics, and accepted values
               for _string_ in this option are not guaranteed to be consistent
               across releases.
    
               This option is only intended to be useful when developing GCC.
    
           **-mverbose-cost-dump**
               Enable verbose cost model dumping in the debug dump files.
               This option is provided for use in debugging the compiler.
    
           **-mpc-relative-literal-loads**
           **-mno-pc-relative-literal-loads**
               Enable or disable PC-relative literal loads.  With this option
               literal pools are accessed using a single instruction and
               emitted after each function.  This limits the maximum size of
               functions to 1MB.  This is enabled by default for
               **-mcmodel=tiny**.
    
           **-msign-return-address=**_scope_
               Select the function scope on which return address signing will
               be applied.  Permissible values are **none** , which disables
               return address signing, **non-leaf** , which enables pointer
               signing for functions which are not leaf functions, and **all** ,
               which enables pointer signing for all functions.  The default
               value is **none**. This option has been deprecated by
               -mbranch-protection.
    
           **-mbranch-protection=**_none_**|**_standard_**|**_pac-ret_**[+**_leaf_**]|**_bti_
               Select the branch protection features to use.  **none** is the
               default and turns off all types of branch protection.
               **standard** turns on all types of branch protection features.  If
               a feature has additional tuning options, then **standard** sets it
               to its standard level.  **pac-ret[+**_leaf_**]** turns on return address
               signing to its standard level: signing functions that save the
               return address to memory (non-leaf functions will practically
               always do this) using the a-key.  The optional argument **leaf**
               can be used to extend the signing to include leaf functions.
               **bti** turns on branch target identification mechanism.
    
           **-mharden-sls=**_opts_
               Enable compiler hardening against straight line speculation
               (SLS).  _opts_ is a comma-separated list of the following
               options:
    
               **retbr**
               **blr**
    
               In addition, **-mharden-sls=all** enables all SLS hardening while
               **-mharden-sls=none** disables all SLS hardening.
    
           **-msve-vector-bits=**_bits_
               Specify the number of bits in an SVE vector register.  This
               option only has an effect when SVE is enabled.
    
               GCC supports two forms of SVE code generation: "vector-length
               agnostic" output that works with any size of vector register
               and "vector-length specific" output that allows GCC to make
               assumptions about the vector length when it is useful for
               optimization reasons.  The possible values of **bits** are:
               **scalable** , **128** , **256** , **512** , **1024** and **2048**.  Specifying **scalable**
               selects vector-length agnostic output.  At present
               **-msve-vector-bits=128** also generates vector-length agnostic
               output.  All other values generate vector-length specific
               code.  The behavior of these values may change in future
               releases and no value except **scalable** should be relied on for
               producing code that is portable across different hardware SVE
               vector lengths.
    
               The default is **-msve-vector-bits=scalable** , which produces
               vector-length agnostic code.
    
           **-march** and **-mcpu** Feature Modifiers
    
           Feature modifiers used with **-march** and **-mcpu** can be any of the
           following and their inverses **no** _feature_ :
    
           **crc** Enable CRC extension.  This is on by default for
               **-march=armv8.1-a**.
    
           **crypto**
               Enable Crypto extension.  This also enables Advanced SIMD and
               floating-point instructions.
    
           **fp** Enable floating-point instructions.  This is on by default for
               all possible values for options **-march** and **-mcpu**.
    
           **simd**
               Enable Advanced SIMD instructions.  This also enables
               floating-point instructions.  This is on by default for all
               possible values for options **-march** and **-mcpu**.
    
           **sve** Enable Scalable Vector Extension instructions.  This also
               enables Advanced SIMD and floating-point instructions.
    
           **lse** Enable Large System Extension instructions.  This is on by
               default for **-march=armv8.1-a**.
    
           **rdma**
               Enable Round Double Multiply Accumulate instructions.  This is
               on by default for **-march=armv8.1-a**.
    
           **fp16**
               Enable FP16 extension.  This also enables floating-point
               instructions.
    
           **fp16fml**
               Enable FP16 fmla extension.  This also enables FP16 extensions
               and floating-point instructions. This option is enabled by
               default for **-march=armv8.4-a**. Use of this option with
               architectures prior to Armv8.2-A is not supported.
    
           **rcpc**
               Enable the RcPc extension.  This does not change code
               generation from GCC, but is passed on to the assembler,
               enabling inline asm statements to use instructions from the
               RcPc extension.
    
           **dotprod**
               Enable the Dot Product extension.  This also enables Advanced
               SIMD instructions.
    
           **aes** Enable the Armv8-a aes and pmull crypto extension.  This also
               enables Advanced SIMD instructions.
    
           **sha2**
               Enable the Armv8-a sha2 crypto extension.  This also enables
               Advanced SIMD instructions.
    
           **sha3**
               Enable the sha512 and sha3 crypto extension.  This also
               enables Advanced SIMD instructions. Use of this option with
               architectures prior to Armv8.2-A is not supported.
    
           **sm4** Enable the sm3 and sm4 crypto extension.  This also enables
               Advanced SIMD instructions.  Use of this option with
               architectures prior to Armv8.2-A is not supported.
    
           **profile**
               Enable the Statistical Profiling extension.  This option is
               only to enable the extension at the assembler level and does
               not affect code generation.
    
           **rng** Enable the Armv8.5-a Random Number instructions.  This option
               is only to enable the extension at the assembler level and
               does not affect code generation.
    
           **memtag**
               Enable the Armv8.5-a Memory Tagging Extensions.  This option
               is only to enable the extension at the assembler level and
               does not affect code generation.
    
           **sb** Enable the Armv8-a Speculation Barrier instruction.  This
               option is only to enable the extension at the assembler level
               and does not affect code generation.  This option is enabled
               by default for **-march=armv8.5-a**.
    
           **ssbs**
               Enable the Armv8-a Speculative Store Bypass Safe instruction.
               This option is only to enable the extension at the assembler
               level and does not affect code generation.  This option is
               enabled by default for **-march=armv8.5-a**.
    
           **predres**
               Enable the Armv8-a Execution and Data Prediction Restriction
               instructions.  This option is only to enable the extension at
               the assembler level and does not affect code generation.  This
               option is enabled by default for **-march=armv8.5-a**.
    
           Feature **crypto** implies **aes** , **sha2** , and **simd** , which implies **fp**.
           Conversely, **nofp** implies **nosimd** , which implies **nocrypto** , **noaes** and
           **nosha2**.
    
           _Adapteva Epiphany Options_
    
           These **-m** options are defined for Adapteva Epiphany:
    
           **-mhalf-reg-file**
               Don't allocate any register in the range "r32"..."r63".  That
               allows code to run on hardware variants that lack these
               registers.
    
           **-mprefer-short-insn-regs**
               Preferentially allocate registers that allow short instruction
               generation.  This can result in increased instruction count,
               so this may either reduce or increase overall code size.
    
           **-mbranch-cost=**_num_
               Set the cost of branches to roughly _num_ "simple" instructions.
               This cost is only a heuristic and is not guaranteed to produce
               consistent results across releases.
    
           **-mcmove**
               Enable the generation of conditional moves.
    
           **-mnops=**_num_
               Emit _num_ NOPs before every other generated instruction.
    
           **-mno-soft-cmpsf**
               For single-precision floating-point comparisons, emit an
               "fsub" instruction and test the flags.  This is faster than a
               software comparison, but can get incorrect results in the
               presence of NaNs, or when two different small numbers are
               compared such that their difference is calculated as zero.
               The default is **-msoft-cmpsf** , which uses slower, but IEEE-
               compliant, software comparisons.
    
           **-mstack-offset=**_num_
               Set the offset between the top of the stack and the stack
               pointer.  E.g., a value of 8 means that the eight bytes in the
               range "sp+0...sp+7" can be used by leaf functions without
               stack allocation.  Values other than **8** or **16** are untested and
               unlikely to work.  Note also that this option changes the ABI;
               compiling a program with a different stack offset than the
               libraries have been compiled with generally does not work.
               This option can be useful if you want to evaluate if a
               different stack offset would give you better code, but to
               actually use a different stack offset to build working
               programs, it is recommended to configure the toolchain with
               the appropriate **--with-stack-offset=**_num_ option.
    
           **-mno-round-nearest**
               Make the scheduler assume that the rounding mode has been set
               to truncating.  The default is **-mround-nearest**.
    
           **-mlong-calls**
               If not otherwise specified by an attribute, assume all calls
               might be beyond the offset range of the "b" / "bl"
               instructions, and therefore load the function address into a
               register before performing a (otherwise direct) call.  This is
               the default.
    
           **-mshort-calls**
               If not otherwise specified by an attribute, assume all direct
               calls are in the range of the "b" / "bl" instructions, so use
               these instructions for direct calls.  The default is
               **-mlong-calls**.
    
           **-msmall16**
               Assume addresses can be loaded as 16-bit unsigned values.
               This does not apply to function addresses for which
               **-mlong-calls** semantics are in effect.
    
           **-mfp-mode=**_mode_
               Set the prevailing mode of the floating-point unit.  This
               determines the floating-point mode that is provided and
               expected at function call and return time.  Making this mode
               match the mode you predominantly need at function start can
               make your programs smaller and faster by avoiding unnecessary
               mode switches.
    
               _mode_ can be set to one the following values:
    
               **caller**
                   Any mode at function entry is valid, and retained or
                   restored when the function returns, and when it calls
                   other functions.  This mode is useful for compiling
                   libraries or other compilation units you might want to
                   incorporate into different programs with different
                   prevailing FPU modes, and the convenience of being able to
                   use a single object file outweighs the size and speed
                   overhead for any extra mode switching that might be
                   needed, compared with what would be needed with a more
                   specific choice of prevailing FPU mode.
    
               **truncate**
                   This is the mode used for floating-point calculations with
                   truncating (i.e. round towards zero) rounding mode.  That
                   includes conversion from floating point to integer.
    
               **round-nearest**
                   This is the mode used for floating-point calculations with
                   round-to-nearest-or-even rounding mode.
    
               **int** This is the mode used to perform integer calculations in
                   the FPU, e.g.  integer multiply, or integer multiply-and-
                   accumulate.
    
               The default is **-mfp-mode=caller**
    
           **-mno-split-lohi**
           **-mno-postinc**
           **-mno-postmodify**
               Code generation tweaks that disable, respectively, splitting
               of 32-bit loads, generation of post-increment addresses, and
               generation of post-modify addresses.  The defaults are **msplit-**
               **lohi** , **-mpost-inc** , and **-mpost-modify**.
    
           **-mnovect-double**
               Change the preferred SIMD mode to SImode.  The default is
               **-mvect-double** , which uses DImode as preferred SIMD mode.
    
           **-max-vect-align=**_num_
               The maximum alignment for SIMD vector mode types.  _num_ may be
               4 or 8.  The default is 8.  Note that this is an ABI change,
               even though many library function interfaces are unaffected if
               they don't use SIMD vector modes in places that affect size
               and/or alignment of relevant types.
    
           **-msplit-vecmove-early**
               Split vector moves into single word moves before reload.  In
               theory this can give better register allocation, but so far
               the reverse seems to be generally the case.
    
           **-m1reg-**_reg_
               Specify a register to hold the constant -1, which makes
               loading small negative constants and certain bitmasks faster.
               Allowable values for _reg_ are **r43** and **r63** , which specify use of
               that register as a fixed register, and **none** , which means that
               no register is used for this purpose.  The default is
               **-m1reg-none**.
    
           _AMD GCN Options_
    
           These options are defined specifically for the AMD GCN port.
    
           **-march=**_gpu_
           **-mtune=**_gpu_
               Set architecture type or tuning for _gpu_. Supported values for
               _gpu_ are
    
               **fiji**
                   Compile for GCN3 Fiji devices (gfx803).
    
               **gfx900**
                   Compile for GCN5 Vega 10 devices (gfx900).
    
           **-mstack-size=**_bytes_
               Specify how many _bytes_ of stack space will be requested for
               each GPU thread (wave-front).  Beware that there may be many
               threads and limited memory available.  The size of the stack
               allocation may also have an impact on run-time performance.
               The default is 32KB when using OpenACC or OpenMP, and 1MB
               otherwise.
    
           _ARC Options_
    
           The following options control the architecture variant for which
           code is being compiled:
    
           **-mbarrel-shifter**
               Generate instructions supported by barrel shifter.  This is
               the default unless **-mcpu=ARC601** or **-mcpu=ARCEM** is in effect.
    
           **-mjli-always**
               Force to call a function using jli_s instruction.  This option
               is valid only for ARCv2 architecture.
    
           **-mcpu=**_cpu_
               Set architecture type, register usage, and instruction
               scheduling parameters for _cpu_.  There are also shortcut alias
               options available for backward compatibility and convenience.
               Supported values for _cpu_ are
    
               **arc600**
                   Compile for ARC600.  Aliases: **-mA6** , **-mARC600**.
    
               **arc601**
                   Compile for ARC601.  Alias: **-mARC601**.
    
               **arc700**
                   Compile for ARC700.  Aliases: **-mA7** , **-mARC700**.  This is the
                   default when configured with **--with-cpu=arc700**.
    
               **arcem**
                   Compile for ARC EM.
    
               **archs**
                   Compile for ARC HS.
    
               **em** Compile for ARC EM CPU with no hardware extensions.
    
               **em4** Compile for ARC EM4 CPU.
    
               **em4_dmips**
                   Compile for ARC EM4 DMIPS CPU.
    
               **em4_fpus**
                   Compile for ARC EM4 DMIPS CPU with the single-precision
                   floating-point extension.
    
               **em4_fpuda**
                   Compile for ARC EM4 DMIPS CPU with single-precision
                   floating-point and double assist instructions.
    
               **hs** Compile for ARC HS CPU with no hardware extensions except
                   the atomic instructions.
    
               **hs34**
                   Compile for ARC HS34 CPU.
    
               **hs38**
                   Compile for ARC HS38 CPU.
    
               **hs38_linux**
                   Compile for ARC HS38 CPU with all hardware extensions on.
    
               **arc600_norm**
                   Compile for ARC 600 CPU with "norm" instructions enabled.
    
               **arc600_mul32x16**
                   Compile for ARC 600 CPU with "norm" and 32x16-bit multiply
                   instructions enabled.
    
               **arc600_mul64**
                   Compile for ARC 600 CPU with "norm" and "mul64"-family
                   instructions enabled.
    
               **arc601_norm**
                   Compile for ARC 601 CPU with "norm" instructions enabled.
    
               **arc601_mul32x16**
                   Compile for ARC 601 CPU with "norm" and 32x16-bit multiply
                   instructions enabled.
    
               **arc601_mul64**
                   Compile for ARC 601 CPU with "norm" and "mul64"-family
                   instructions enabled.
    
               **nps400**
                   Compile for ARC 700 on NPS400 chip.
    
               **em_mini**
                   Compile for ARC EM minimalist configuration featuring
                   reduced register set.
    
           **-mdpfp**
           **-mdpfp-compact**
               Generate double-precision FPX instructions, tuned for the
               compact implementation.
    
           **-mdpfp-fast**
               Generate double-precision FPX instructions, tuned for the fast
               implementation.
    
           **-mno-dpfp-lrsr**
               Disable "lr" and "sr" instructions from using FPX extension
               aux registers.
    
           **-mea**
               Generate extended arithmetic instructions.  Currently only
               "divaw", "adds", "subs", and "sat16" are supported.  This is
               always enabled for **-mcpu=ARC700**.
    
           **-mno-mpy**
               Do not generate "mpy"-family instructions for ARC700.  This
               option is deprecated.
    
           **-mmul32x16**
               Generate 32x16-bit multiply and multiply-accumulate
               instructions.
    
           **-mmul64**
               Generate "mul64" and "mulu64" instructions.  Only valid for
               **-mcpu=ARC600**.
    
           **-mnorm**
               Generate "norm" instructions.  This is the default if
               **-mcpu=ARC700** is in effect.
    
           **-mspfp**
           **-mspfp-compact**
               Generate single-precision FPX instructions, tuned for the
               compact implementation.
    
           **-mspfp-fast**
               Generate single-precision FPX instructions, tuned for the fast
               implementation.
    
           **-msimd**
               Enable generation of ARC SIMD instructions via target-specific
               builtins.  Only valid for **-mcpu=ARC700**.
    
           **-msoft-float**
               This option ignored; it is provided for compatibility purposes
               only.  Software floating-point code is emitted by default, and
               this default can overridden by FPX options; **-mspfp** ,
               **-mspfp-compact** , or **-mspfp-fast** for single precision, and
               **-mdpfp** , **-mdpfp-compact** , or **-mdpfp-fast** for double precision.
    
           **-mswap**
               Generate "swap" instructions.
    
           **-matomic**
               This enables use of the locked load/store conditional
               extension to implement atomic memory built-in functions.  Not
               available for ARC 6xx or ARC EM cores.
    
           **-mdiv-rem**
               Enable "div" and "rem" instructions for ARCv2 cores.
    
           **-mcode-density**
               Enable code density instructions for ARC EM.  This option is
               on by default for ARC HS.
    
           **-mll64**
               Enable double load/store operations for ARC HS cores.
    
           **-mtp-regno=**_regno_
               Specify thread pointer register number.
    
           **-mmpy-option=**_multo_
               Compile ARCv2 code with a multiplier design option.  You can
               specify the option using either a string or numeric value for
               _multo_.  **wlh1** is the default value.  The recognized values are:
    
               **0**
               **none**
                   No multiplier available.
    
               **1**
               **w** 16x16 multiplier, fully pipelined.  The following
                   instructions are enabled: "mpyw" and "mpyuw".
    
               **2**
               **wlh1**
                   32x32 multiplier, fully pipelined (1 stage).  The
                   following instructions are additionally enabled: "mpy",
                   "mpyu", "mpym", "mpymu", and "mpy_s".
    
               **3**
               **wlh2**
                   32x32 multiplier, fully pipelined (2 stages).  The
                   following instructions are additionally enabled: "mpy",
                   "mpyu", "mpym", "mpymu", and "mpy_s".
    
               **4**
               **wlh3**
                   Two 16x16 multipliers, blocking, sequential.  The
                   following instructions are additionally enabled: "mpy",
                   "mpyu", "mpym", "mpymu", and "mpy_s".
    
               **5**
               **wlh4**
                   One 16x16 multiplier, blocking, sequential.  The following
                   instructions are additionally enabled: "mpy", "mpyu",
                   "mpym", "mpymu", and "mpy_s".
    
               **6**
               **wlh5**
                   One 32x4 multiplier, blocking, sequential.  The following
                   instructions are additionally enabled: "mpy", "mpyu",
                   "mpym", "mpymu", and "mpy_s".
    
               **7**
               **plus_dmpy**
                   ARC HS SIMD support.
    
               **8**
               **plus_macd**
                   ARC HS SIMD support.
    
               **9**
               **plus_qmacw**
                   ARC HS SIMD support.
    
               This option is only available for ARCv2 cores.
    
           **-mfpu=**_fpu_
               Enables support for specific floating-point hardware
               extensions for ARCv2 cores.  Supported values for _fpu_ are:
    
               **fpus**
                   Enables support for single-precision floating-point
                   hardware extensions.
    
               **fpud**
                   Enables support for double-precision floating-point
                   hardware extensions.  The single-precision floating-point
                   extension is also enabled.  Not available for ARC EM.
    
               **fpuda**
                   Enables support for double-precision floating-point
                   hardware extensions using double-precision assist
                   instructions.  The single-precision floating-point
                   extension is also enabled.  This option is only available
                   for ARC EM.
    
               **fpuda_div**
                   Enables support for double-precision floating-point
                   hardware extensions using double-precision assist
                   instructions.  The single-precision floating-point,
                   square-root, and divide extensions are also enabled.  This
                   option is only available for ARC EM.
    
               **fpuda_fma**
                   Enables support for double-precision floating-point
                   hardware extensions using double-precision assist
                   instructions.  The single-precision floating-point and
                   fused multiply and add hardware extensions are also
                   enabled.  This option is only available for ARC EM.
    
               **fpuda_all**
                   Enables support for double-precision floating-point
                   hardware extensions using double-precision assist
                   instructions.  All single-precision floating-point
                   hardware extensions are also enabled.  This option is only
                   available for ARC EM.
    
               **fpus_div**
                   Enables support for single-precision floating-point,
                   square-root and divide hardware extensions.
    
               **fpud_div**
                   Enables support for double-precision floating-point,
                   square-root and divide hardware extensions.  This option
                   includes option **fpus_div**. Not available for ARC EM.
    
               **fpus_fma**
                   Enables support for single-precision floating-point and
                   fused multiply and add hardware extensions.
    
               **fpud_fma**
                   Enables support for double-precision floating-point and
                   fused multiply and add hardware extensions.  This option
                   includes option **fpus_fma**.  Not available for ARC EM.
    
               **fpus_all**
                   Enables support for all single-precision floating-point
                   hardware extensions.
    
               **fpud_all**
                   Enables support for all single- and double-precision
                   floating-point hardware extensions.  Not available for ARC
                   EM.
    
           **-mirq-ctrl-saved=**_register-range_**,**_blink_**,**_lp_count_
               Specifies general-purposes registers that the processor
               automatically saves/restores on interrupt entry and exit.
               _register-range_ is specified as two registers separated by a
               dash.  The register range always starts with "r0", the upper
               limit is "fp" register.  _blink_ and _lp_count_ are optional.
               This option is only valid for ARC EM and ARC HS cores.
    
           **-mrgf-banked-regs=**_number_
               Specifies the number of registers replicated in second
               register bank on entry to fast interrupt.  Fast interrupts are
               interrupts with the highest priority level P0.  These
               interrupts save only PC and STATUS32 registers to avoid memory
               transactions during interrupt entry and exit sequences.  Use
               this option when you are using fast interrupts in an ARC V2
               family processor.  Permitted values are 4, 8, 16, and 32.
    
           **-mlpc-width=**_width_
               Specify the width of the "lp_count" register.  Valid values
               for _width_ are 8, 16, 20, 24, 28 and 32 bits.  The default
               width is fixed to 32 bits.  If the width is less than 32, the
               compiler does not attempt to transform loops in your program
               to use the zero-delay loop mechanism unless it is known that
               the "lp_count" register can hold the required loop-counter
               value.  Depending on the width specified, the compiler and
               run-time library might continue to use the loop mechanism for
               various needs.  This option defines macro "__ARC_LPC_WIDTH__"
               with the value of _width_.
    
           **-mrf16**
               This option instructs the compiler to generate code for a
               16-entry register file.  This option defines the
               "__ARC_RF16__" preprocessor macro.
    
           **-mbranch-index**
               Enable use of "bi" or "bih" instructions to implement jump
               tables.
    
           The following options are passed through to the assembler, and
           also define preprocessor macro symbols.
    
           **-mdsp-packa**
               Passed down to the assembler to enable the DSP Pack A
               extensions.  Also sets the preprocessor symbol "__Xdsp_packa".
               This option is deprecated.
    
           **-mdvbf**
               Passed down to the assembler to enable the dual Viterbi
               butterfly extension.  Also sets the preprocessor symbol
               "__Xdvbf".  This option is deprecated.
    
           **-mlock**
               Passed down to the assembler to enable the locked load/store
               conditional extension.  Also sets the preprocessor symbol
               "__Xlock".
    
           **-mmac-d16**
               Passed down to the assembler.  Also sets the preprocessor
               symbol "__Xxmac_d16".  This option is deprecated.
    
           **-mmac-24**
               Passed down to the assembler.  Also sets the preprocessor
               symbol "__Xxmac_24".  This option is deprecated.
    
           **-mrtsc**
               Passed down to the assembler to enable the 64-bit time-stamp
               counter extension instruction.  Also sets the preprocessor
               symbol "__Xrtsc".  This option is deprecated.
    
           **-mswape**
               Passed down to the assembler to enable the swap byte ordering
               extension instruction.  Also sets the preprocessor symbol
               "__Xswape".
    
           **-mtelephony**
               Passed down to the assembler to enable dual- and single-
               operand instructions for telephony.  Also sets the
               preprocessor symbol "__Xtelephony".  This option is
               deprecated.
    
           **-mxy**
               Passed down to the assembler to enable the XY memory
               extension.  Also sets the preprocessor symbol "__Xxy".
    
           The following options control how the assembly code is annotated:
    
           **-misize**
               Annotate assembler instructions with estimated addresses.
    
           **-mannotate-align**
               Explain what alignment considerations lead to the decision to
               make an instruction short or long.
    
           The following options are passed through to the linker:
    
           **-marclinux**
               Passed through to the linker, to specify use of the "arclinux"
               emulation.  This option is enabled by default in tool chains
               built for "arc-linux-uclibc" and "arceb-linux-uclibc" targets
               when profiling is not requested.
    
           **-marclinux_prof**
               Passed through to the linker, to specify use of the
               "arclinux_prof" emulation.  This option is enabled by default
               in tool chains built for "arc-linux-uclibc" and
               "arceb-linux-uclibc" targets when profiling is requested.
    
           The following options control the semantics of generated code:
    
           **-mlong-calls**
               Generate calls as register indirect calls, thus providing
               access to the full 32-bit address range.
    
           **-mmedium-calls**
               Don't use less than 25-bit addressing range for calls, which
               is the offset available for an unconditional branch-and-link
               instruction.  Conditional execution of function calls is
               suppressed, to allow use of the 25-bit range, rather than the
               21-bit range with conditional branch-and-link.  This is the
               default for tool chains built for "arc-linux-uclibc" and
               "arceb-linux-uclibc" targets.
    
           **-G** _num_
               Put definitions of externally-visible data in a small data
               section if that data is no bigger than _num_ bytes.  The default
               value of _num_ is 4 for any ARC configuration, or 8 when we have
               double load/store operations.
    
           **-mno-sdata**
               Do not generate sdata references.  This is the default for
               tool chains built for "arc-linux-uclibc" and
               "arceb-linux-uclibc" targets.
    
           **-mvolatile-cache**
               Use ordinarily cached memory accesses for volatile references.
               This is the default.
    
           **-mno-volatile-cache**
               Enable cache bypass for volatile references.
    
           The following options fine tune code generation:
    
           **-malign-call**
               Do alignment optimizations for call instructions.
    
           **-mauto-modify-reg**
               Enable the use of pre/post modify with register displacement.
    
           **-mbbit-peephole**
               Enable bbit peephole2.
    
           **-mno-brcc**
               This option disables a target-specific pass in _arc_reorg_ to
               generate compare-and-branch ("br _cc"_) instructions.  It has no
               effect on generation of these instructions driven by the
               combiner pass.
    
           **-mcase-vector-pcrel**
               Use PC-relative switch case tables to enable case table
               shortening.  This is the default for **-Os**.
    
           **-mcompact-casesi**
               Enable compact "casesi" pattern.  This is the default for **-Os** ,
               and only available for ARCv1 cores.  This option is
               deprecated.
    
           **-mno-cond-exec**
               Disable the ARCompact-specific pass to generate conditional
               execution instructions.
    
               Due to delay slot scheduling and interactions between operand
               numbers, literal sizes, instruction lengths, and the support
               for conditional execution, the target-independent pass to
               generate conditional execution is often lacking, so the ARC
               port has kept a special pass around that tries to find more
               conditional execution generation opportunities after register
               allocation, branch shortening, and delay slot scheduling have
               been done.  This pass generally, but not always, improves
               performance and code size, at the cost of extra compilation
               time, which is why there is an option to switch it off.  If
               you have a problem with call instructions exceeding their
               allowable offset range because they are conditionalized, you
               should consider using **-mmedium-calls** instead.
    
           **-mearly-cbranchsi**
               Enable pre-reload use of the "cbranchsi" pattern.
    
           **-mexpand-adddi**
               Expand "adddi3" and "subdi3" at RTL generation time into
               "add.f", "adc" etc.  This option is deprecated.
    
           **-mindexed-loads**
               Enable the use of indexed loads.  This can be problematic
               because some optimizers then assume that indexed stores exist,
               which is not the case.
    
           **-mlra**
               Enable Local Register Allocation.  This is still experimental
               for ARC, so by default the compiler uses standard reload (i.e.
               **-mno-lra**).
    
           **-mlra-priority-none**
               Don't indicate any priority for target registers.
    
           **-mlra-priority-compact**
               Indicate target register priority for r0..r3 / r12..r15.
    
           **-mlra-priority-noncompact**
               Reduce target register priority for r0..r3 / r12..r15.
    
           **-mmillicode**
               When optimizing for size (using **-Os**), prologues and epilogues
               that have to save or restore a large number of registers are
               often shortened by using call to a special function in libgcc;
               this is referred to as a _millicode_ call.  As these calls can
               pose performance issues, and/or cause linking issues when
               linking in a nonstandard way, this option is provided to turn
               on or off millicode call generation.
    
           **-mcode-density-frame**
               This option enable the compiler to emit "enter" and "leave"
               instructions.  These instructions are only valid for CPUs with
               code-density feature.
    
           **-mmixed-code**
               Tweak register allocation to help 16-bit instruction
               generation.  This generally has the effect of decreasing the
               average instruction size while increasing the instruction
               count.
    
           **-mq-class**
               Enable **q** instruction alternatives.  This is the default for
               **-Os**.
    
           **-mRcq**
               Enable **Rcq** constraint handling.  Most short code generation
               depends on this.  This is the default.
    
           **-mRcw**
               Enable **Rcw** constraint handling.  Most ccfsm condexec mostly
               depends on this.  This is the default.
    
           **-msize-level=**_level_
               Fine-tune size optimization with regards to instruction
               lengths and alignment.  The recognized values for _level_ are:
    
               **0** No size optimization.  This level is deprecated and
                   treated like **1**.
    
               **1** Short instructions are used opportunistically.
    
               **2** In addition, alignment of loops and of code after barriers
                   are dropped.
    
               **3** In addition, optional data alignment is dropped, and the
                   option **Os** is enabled.
    
               This defaults to **3** when **-Os** is in effect.  Otherwise, the
               behavior when this is not set is equivalent to level **1**.
    
           **-mtune=**_cpu_
               Set instruction scheduling parameters for _cpu_ , overriding any
               implied by **-mcpu=**.
    
               Supported values for _cpu_ are
    
               **ARC600**
                   Tune for ARC600 CPU.
    
               **ARC601**
                   Tune for ARC601 CPU.
    
               **ARC700**
                   Tune for ARC700 CPU with standard multiplier block.
    
               **ARC700-xmac**
                   Tune for ARC700 CPU with XMAC block.
    
               **ARC725D**
                   Tune for ARC725D CPU.
    
               **ARC750D**
                   Tune for ARC750D CPU.
    
           **-mmultcost=**_num_
               Cost to assume for a multiply instruction, with **4** being equal
               to a normal instruction.
    
           **-munalign-prob-threshold=**_probability_
               Set probability threshold for unaligning branches.  When
               tuning for **ARC700** and optimizing for speed, branches without
               filled delay slot are preferably emitted unaligned and long,
               unless profiling indicates that the probability for the branch
               to be taken is below _probability_.  The default is
               (REG_BR_PROB_BASE/2), i.e. 5000.
    
           The following options are maintained for backward compatibility,
           but are now deprecated and will be removed in a future release:
    
           **-margonaut**
               Obsolete FPX.
    
           **-mbig-endian**
           **-EB** Compile code for big-endian targets.  Use of these options is
               now deprecated.  Big-endian code is supported by configuring
               GCC to build "arceb-elf32" and "arceb-linux-uclibc" targets,
               for which big endian is the default.
    
           **-mlittle-endian**
           **-EL** Compile code for little-endian targets.  Use of these options
               is now deprecated.  Little-endian code is supported by
               configuring GCC to build "arc-elf32" and "arc-linux-uclibc"
               targets, for which little endian is the default.
    
           **-mbarrel_shifter**
               Replaced by **-mbarrel-shifter**.
    
           **-mdpfp_compact**
               Replaced by **-mdpfp-compact**.
    
           **-mdpfp_fast**
               Replaced by **-mdpfp-fast**.
    
           **-mdsp_packa**
               Replaced by **-mdsp-packa**.
    
           **-mEA**
               Replaced by **-mea**.
    
           **-mmac_24**
               Replaced by **-mmac-24**.
    
           **-mmac_d16**
               Replaced by **-mmac-d16**.
    
           **-mspfp_compact**
               Replaced by **-mspfp-compact**.
    
           **-mspfp_fast**
               Replaced by **-mspfp-fast**.
    
           **-mtune=**_cpu_
               Values **arc600** , **arc601** , **arc700** and **arc700-xmac** for _cpu_ are
               replaced by **ARC600** , **ARC601** , **ARC700** and **ARC700-xmac**
               respectively.
    
           **-multcost=**_num_
               Replaced by **-mmultcost**.
    
           _ARM Options_
    
           These **-m** options are defined for the ARM port:
    
           **-mabi=**_name_
               Generate code for the specified ABI.  Permissible values are:
               **apcs-gnu** , **atpcs** , **aapcs** , **aapcs-linux** and **iwmmxt**.
    
           **-mapcs-frame**
               Generate a stack frame that is compliant with the ARM
               Procedure Call Standard for all functions, even if this is not
               strictly necessary for correct execution of the code.
               Specifying **-fomit-frame-pointer** with this option causes the
               stack frames not to be generated for leaf functions.  The
               default is **-mno-apcs-frame**.  This option is deprecated.
    
           **-mapcs**
               This is a synonym for **-mapcs-frame** and is deprecated.
    
           **-mthumb-interwork**
               Generate code that supports calling between the ARM and Thumb
               instruction sets.  Without this option, on pre-v5
               architectures, the two instruction sets cannot be reliably
               used inside one program.  The default is **-mno-thumb-interwork** ,
               since slightly larger code is generated when **-mthumb-interwork**
               is specified.  In AAPCS configurations this option is
               meaningless.
    
           **-mno-sched-prolog**
               Prevent the reordering of instructions in the function
               prologue, or the merging of those instruction with the
               instructions in the function's body.  This means that all
               functions start with a recognizable set of instructions (or in
               fact one of a choice from a small set of different function
               prologues), and this information can be used to locate the
               start of functions inside an executable piece of code.  The
               default is **-msched-prolog**.
    
           **-mfloat-abi=**_name_
               Specifies which floating-point ABI to use.  Permissible values
               are: **soft** , **softfp** and **hard**.
    
               Specifying **soft** causes GCC to generate output containing
               library calls for floating-point operations.  **softfp** allows
               the generation of code using hardware floating-point
               instructions, but still uses the soft-float calling
               conventions.  **hard** allows generation of floating-point
               instructions and uses FPU-specific calling conventions.
    
               The default depends on the specific target configuration.
               Note that the hard-float and soft-float ABIs are not link-
               compatible; you must compile your entire program with the same
               ABI, and link with a compatible set of libraries.
    
           **-mgeneral-regs-only**
               Generate code which uses only the general-purpose registers.
               This will prevent the compiler from using floating-point and
               Advanced SIMD registers but will not impose any restrictions
               on the assembler.
    
           **-mlittle-endian**
               Generate code for a processor running in little-endian mode.
               This is the default for all standard configurations.
    
           **-mbig-endian**
               Generate code for a processor running in big-endian mode; the
               default is to compile code for a little-endian processor.
    
           **-mbe8**
           **-mbe32**
               When linking a big-endian image select between BE8 and BE32
               formats.  The option has no effect for little-endian images
               and is ignored.  The default is dependent on the selected
               target architecture.  For ARMv6 and later architectures the
               default is BE8, for older architectures the default is BE32.
               BE32 format has been deprecated by ARM.
    
           **-march=**_name_[**+extension...**]
               This specifies the name of the target ARM architecture.  GCC
               uses this name to determine what kind of instructions it can
               emit when generating assembly code.  This option can be used
               in conjunction with or instead of the **-mcpu=** option.
    
               Permissible names are: **armv4t** , **armv5t** , **armv5te** , **armv6** , **armv6j** ,
               **armv6k** , **armv6kz** , **armv6t2** , **armv6z** , **armv6zk** , **armv7** , **armv7-a** ,
               **armv7ve** , **armv8-a** , **armv8.1-a** , **armv8.2-a** , **armv8.3-a** , **armv8.4-a** ,
               **armv8.5-a** , **armv7-r** , **armv8-r** , **armv6-m** , **armv6s-m** , **armv7-m** ,
               **armv7e-m** , **armv8-m.base** , **armv8-m.main** , **iwmmxt** and **iwmmxt2**.
    
               Additionally, the following architectures, which lack support
               for the Thumb execution state, are recognized but support is
               deprecated: **armv4**.
    
               Many of the architectures support extensions.  These can be
               added by appending **+**_extension_ to the architecture name.
               Extension options are processed in order and capabilities
               accumulate.  An extension will also enable any necessary base
               extensions upon which it depends.  For example, the **+crypto**
               extension will always enable the **+simd** extension.  The
               exception to the additive construction is for extensions that
               are prefixed with **+no...** : these extensions disable the
               specified option and any other extensions that may depend on
               the presence of that extension.
    
               For example, **-march=armv7-a+simd+nofp+vfpv4** is equivalent to
               writing **-march=armv7-a+vfpv4** since the **+simd** option is
               entirely disabled by the **+nofp** option that follows it.
    
               Most extension names are generically named, but have an effect
               that is dependent upon the architecture to which it is
               applied.  For example, the **+simd** option can be applied to both
               **armv7-a** and **armv8-a** architectures, but will enable the
               original ARMv7-A Advanced SIMD (Neon) extensions for **armv7-a**
               and the ARMv8-A variant for **armv8-a**.
    
               The table below lists the supported extensions for each
               architecture.  Architectures not mentioned do not support any
               extensions.
    
               **armv5te**
               **armv6**
               **armv6j**
               **armv6k**
               **armv6kz**
               **armv6t2**
               **armv6z**
               **armv6zk**
                   **+fp** The VFPv2 floating-point instructions.  The extension
                       **+vfpv2** can be used as an alias for this extension.
    
                   **+nofp**
                       Disable the floating-point instructions.
    
               **armv7**
                   The common subset of the ARMv7-A, ARMv7-R and ARMv7-M
                   architectures.
    
                   **+fp** The VFPv3 floating-point instructions, with 16 double-
                       precision registers.  The extension **+vfpv3-d16** can be
                       used as an alias for this extension.  Note that
                       floating-point is not supported by the base ARMv7-M
                       architecture, but is compatible with both the ARMv7-A
                       and ARMv7-R architectures.
    
                   **+nofp**
                       Disable the floating-point instructions.
    
               **armv7-a**
                   **+mp** The multiprocessing extension.
    
                   **+sec**
                       The security extension.
    
                   **+fp** The VFPv3 floating-point instructions, with 16 double-
                       precision registers.  The extension **+vfpv3-d16** can be
                       used as an alias for this extension.
    
                   **+simd**
                       The Advanced SIMD (Neon) v1 and the VFPv3 floating-
                       point instructions.  The extensions **+neon** and
                       **+neon-vfpv3** can be used as aliases for this extension.
    
                   **+vfpv3**
                       The VFPv3 floating-point instructions, with 32 double-
                       precision registers.
    
                   **+vfpv3-d16-fp16**
                       The VFPv3 floating-point instructions, with 16 double-
                       precision registers and the half-precision floating-
                       point conversion operations.
    
                   **+vfpv3-fp16**
                       The VFPv3 floating-point instructions, with 32 double-
                       precision registers and the half-precision floating-
                       point conversion operations.
    
                   **+vfpv4-d16**
                       The VFPv4 floating-point instructions, with 16 double-
                       precision registers.
    
                   **+vfpv4**
                       The VFPv4 floating-point instructions, with 32 double-
                       precision registers.
    
                   **+neon-fp16**
                       The Advanced SIMD (Neon) v1 and the VFPv3 floating-
                       point instructions, with the half-precision floating-
                       point conversion operations.
    
                   **+neon-vfpv4**
                       The Advanced SIMD (Neon) v2 and the VFPv4 floating-
                       point instructions.
    
                   **+nosimd**
                       Disable the Advanced SIMD instructions (does not
                       disable floating point).
    
                   **+nofp**
                       Disable the floating-point and Advanced SIMD
                       instructions.
    
               **armv7ve**
                   The extended version of the ARMv7-A architecture with
                   support for virtualization.
    
                   **+fp** The VFPv4 floating-point instructions, with 16 double-
                       precision registers.  The extension **+vfpv4-d16** can be
                       used as an alias for this extension.
    
                   **+simd**
                       The Advanced SIMD (Neon) v2 and the VFPv4 floating-
                       point instructions.  The extension **+neon-vfpv4** can be
                       used as an alias for this extension.
    
                   **+vfpv3-d16**
                       The VFPv3 floating-point instructions, with 16 double-
                       precision registers.
    
                   **+vfpv3**
                       The VFPv3 floating-point instructions, with 32 double-
                       precision registers.
    
                   **+vfpv3-d16-fp16**
                       The VFPv3 floating-point instructions, with 16 double-
                       precision registers and the half-precision floating-
                       point conversion operations.
    
                   **+vfpv3-fp16**
                       The VFPv3 floating-point instructions, with 32 double-
                       precision registers and the half-precision floating-
                       point conversion operations.
    
                   **+vfpv4-d16**
                       The VFPv4 floating-point instructions, with 16 double-
                       precision registers.
    
                   **+vfpv4**
                       The VFPv4 floating-point instructions, with 32 double-
                       precision registers.
    
                   **+neon**
                       The Advanced SIMD (Neon) v1 and the VFPv3 floating-
                       point instructions.  The extension **+neon-vfpv3** can be
                       used as an alias for this extension.
    
                   **+neon-fp16**
                       The Advanced SIMD (Neon) v1 and the VFPv3 floating-
                       point instructions, with the half-precision floating-
                       point conversion operations.
    
                   **+nosimd**
                       Disable the Advanced SIMD instructions (does not
                       disable floating point).
    
                   **+nofp**
                       Disable the floating-point and Advanced SIMD
                       instructions.
    
               **armv8-a**
                   **+crc**
                       The Cyclic Redundancy Check (CRC) instructions.
    
                   **+simd**
                       The ARMv8-A Advanced SIMD and floating-point
                       instructions.
    
                   **+crypto**
                       The cryptographic instructions.
    
                   **+nocrypto**
                       Disable the cryptographic instructions.
    
                   **+nofp**
                       Disable the floating-point, Advanced SIMD and
                       cryptographic instructions.
    
                   **+sb** Speculation Barrier Instruction.
    
                   **+predres**
                       Execution and Data Prediction Restriction
                       Instructions.
    
               **armv8.1-a**
                   **+simd**
                       The ARMv8.1-A Advanced SIMD and floating-point
                       instructions.
    
                   **+crypto**
                       The cryptographic instructions.  This also enables the
                       Advanced SIMD and floating-point instructions.
    
                   **+nocrypto**
                       Disable the cryptographic instructions.
    
                   **+nofp**
                       Disable the floating-point, Advanced SIMD and
                       cryptographic instructions.
    
                   **+sb** Speculation Barrier Instruction.
    
                   **+predres**
                       Execution and Data Prediction Restriction
                       Instructions.
    
               **armv8.2-a**
               **armv8.3-a**
                   **+fp16**
                       The half-precision floating-point data processing
                       instructions.  This also enables the Advanced SIMD and
                       floating-point instructions.
    
                   **+fp16fml**
                       The half-precision floating-point fmla extension.
                       This also enables the half-precision floating-point
                       extension and Advanced SIMD and floating-point
                       instructions.
    
                   **+simd**
                       The ARMv8.1-A Advanced SIMD and floating-point
                       instructions.
    
                   **+crypto**
                       The cryptographic instructions.  This also enables the
                       Advanced SIMD and floating-point instructions.
    
                   **+dotprod**
                       Enable the Dot Product extension.  This also enables
                       Advanced SIMD instructions.
    
                   **+nocrypto**
                       Disable the cryptographic extension.
    
                   **+nofp**
                       Disable the floating-point, Advanced SIMD and
                       cryptographic instructions.
    
                   **+sb** Speculation Barrier Instruction.
    
                   **+predres**
                       Execution and Data Prediction Restriction
                       Instructions.
    
               **armv8.4-a**
                   **+fp16**
                       The half-precision floating-point data processing
                       instructions.  This also enables the Advanced SIMD and
                       floating-point instructions as well as the Dot Product
                       extension and the half-precision floating-point fmla
                       extension.
    
                   **+simd**
                       The ARMv8.3-A Advanced SIMD and floating-point
                       instructions as well as the Dot Product extension.
    
                   **+crypto**
                       The cryptographic instructions.  This also enables the
                       Advanced SIMD and floating-point instructions as well
                       as the Dot Product extension.
    
                   **+nocrypto**
                       Disable the cryptographic extension.
    
                   **+nofp**
                       Disable the floating-point, Advanced SIMD and
                       cryptographic instructions.
    
                   **+sb** Speculation Barrier Instruction.
    
                   **+predres**
                       Execution and Data Prediction Restriction
                       Instructions.
    
               **armv8.5-a**
                   **+fp16**
                       The half-precision floating-point data processing
                       instructions.  This also enables the Advanced SIMD and
                       floating-point instructions as well as the Dot Product
                       extension and the half-precision floating-point fmla
                       extension.
    
                   **+simd**
                       The ARMv8.3-A Advanced SIMD and floating-point
                       instructions as well as the Dot Product extension.
    
                   **+crypto**
                       The cryptographic instructions.  This also enables the
                       Advanced SIMD and floating-point instructions as well
                       as the Dot Product extension.
    
                   **+nocrypto**
                       Disable the cryptographic extension.
    
                   **+nofp**
                       Disable the floating-point, Advanced SIMD and
                       cryptographic instructions.
    
               **armv7-r**
                   **+fp.sp**
                       The single-precision VFPv3 floating-point
                       instructions.  The extension **+vfpv3xd** can be used as
                       an alias for this extension.
    
                   **+fp** The VFPv3 floating-point instructions with 16 double-
                       precision registers.  The extension +vfpv3-d16 can be
                       used as an alias for this extension.
    
                   **+vfpv3xd-d16-fp16**
                       The single-precision VFPv3 floating-point instructions
                       with 16 double-precision registers and the half-
                       precision floating-point conversion operations.
    
                   **+vfpv3-d16-fp16**
                       The VFPv3 floating-point instructions with 16 double-
                       precision registers and the half-precision floating-
                       point conversion operations.
    
                   **+nofp**
                       Disable the floating-point extension.
    
                   **+idiv**
                       The ARM-state integer division instructions.
    
                   **+noidiv**
                       Disable the ARM-state integer division extension.
    
               **armv7e-m**
                   **+fp** The single-precision VFPv4 floating-point
                       instructions.
    
                   **+fpv5**
                       The single-precision FPv5 floating-point instructions.
    
                   **+fp.dp**
                       The single- and double-precision FPv5 floating-point
                       instructions.
    
                   **+nofp**
                       Disable the floating-point extensions.
    
               **armv8-m.main**
                   **+dsp**
                       The DSP instructions.
    
                   **+nodsp**
                       Disable the DSP extension.
    
                   **+fp** The single-precision floating-point instructions.
    
                   **+fp.dp**
                       The single- and double-precision floating-point
                       instructions.
    
                   **+nofp**
                       Disable the floating-point extension.
    
               **armv8-r**
                   **+crc**
                       The Cyclic Redundancy Check (CRC) instructions.
    
                   **+fp.sp**
                       The single-precision FPv5 floating-point instructions.
    
                   **+simd**
                       The ARMv8-A Advanced SIMD and floating-point
                       instructions.
    
                   **+crypto**
                       The cryptographic instructions.
    
                   **+nocrypto**
                       Disable the cryptographic instructions.
    
                   **+nofp**
                       Disable the floating-point, Advanced SIMD and
                       cryptographic instructions.
    
               **-march=native** causes the compiler to auto-detect the
               architecture of the build computer.  At present, this feature
               is only supported on GNU/Linux, and not all architectures are
               recognized.  If the auto-detect is unsuccessful the option has
               no effect.
    
           **-mtune=**_name_
               This option specifies the name of the target ARM processor for
               which GCC should tune the performance of the code.  For some
               ARM implementations better performance can be obtained by
               using this option.  Permissible names are: **arm7tdmi** ,
               **arm7tdmi-s** , **arm710t** , **arm720t** , **arm740t** , **strongarm** ,
               **strongarm110** , **strongarm1100** , 0**strongarm1110** , **arm8** , **arm810** ,
               **arm9** , **arm9e** , **arm920** , **arm920t** , **arm922t** , **arm946e-s** , **arm966e-s** ,
               **arm968e-s** , **arm926ej-s** , **arm940t** , **arm9tdmi** , **arm10tdmi** , **arm1020t** ,
               **arm1026ej-s** , **arm10e** , **arm1020e** , **arm1022e** , **arm1136j-s** ,
               **arm1136jf-s** , **mpcore** , **mpcorenovfp** , **arm1156t2-s** , **arm1156t2f-s** ,
               **arm1176jz-s** , **arm1176jzf-s** , **generic-armv7-a** , **cortex-a5** ,
               **cortex-a7** , **cortex-a8** , **cortex-a9** , **cortex-a12** , **cortex-a15** ,
               **cortex-a17** , **cortex-a32** , **cortex-a35** , **cortex-a53** , **cortex-a55** ,
               **cortex-a57** , **cortex-a72** , **cortex-a73** , **cortex-a75** , **cortex-a76** ,
               **ares** , **cortex-r4** , **cortex-r4f** , **cortex-r5** , **cortex-r7** , **cortex-r8** ,
               **cortex-r52** , **cortex-m0** , **cortex-m0plus** , **cortex-m1** , **cortex-m3** ,
               **cortex-m4** , **cortex-m7** , **cortex-m23** , **cortex-m33** ,
               **cortex-m1.small-multiply** , **cortex-m0.small-multiply** ,
               **cortex-m0plus.small-multiply** , **exynos-m1** , **marvell-pj4** ,
               **neoverse-n1** , **neoverse-n2** , **neoverse-v1** , **xscale** , **iwmmxt** ,
               **iwmmxt2** , **ep9312** , **fa526** , **fa626** , **fa606te** , **fa626te** , **fmp626** ,
               **fa726te** , **xgene1**.
    
               Additionally, this option can specify that GCC should tune the
               performance of the code for a big.LITTLE system.  Permissible
               names are: **cortex-a15.cortex-a7** , **cortex-a17.cortex-a7** ,
               **cortex-a57.cortex-a53** , **cortex-a72.cortex-a53** ,
               **cortex-a72.cortex-a35** , **cortex-a73.cortex-a53** ,
               **cortex-a75.cortex-a55** , **cortex-a76.cortex-a55**.
    
               **-mtune=generic-**_arch_ specifies that GCC should tune the
               performance for a blend of processors within architecture
               _arch_.  The aim is to generate code that run well on the
               current most popular processors, balancing between
               optimizations that benefit some CPUs in the range, and
               avoiding performance pitfalls of other CPUs.  The effects of
               this option may change in future GCC versions as CPU models
               come and go.
    
               **-mtune** permits the same extension options as **-mcpu** , but the
               extension options do not affect the tuning of the generated
               code.
    
               **-mtune=native** causes the compiler to auto-detect the CPU of
               the build computer.  At present, this feature is only
               supported on GNU/Linux, and not all architectures are
               recognized.  If the auto-detect is unsuccessful the option has
               no effect.
    
           **-mcpu=**_name_[**+extension...**]
               This specifies the name of the target ARM processor.  GCC uses
               this name to derive the name of the target ARM architecture
               (as if specified by **-march**) and the ARM processor type for
               which to tune for performance (as if specified by **-mtune**).
               Where this option is used in conjunction with **-march** or
               **-mtune** , those options take precedence over the appropriate
               part of this option.
    
               Many of the supported CPUs implement optional architectural
               extensions.  Where this is so the architectural extensions are
               normally enabled by default.  If implementations that lack the
               extension exist, then the extension syntax can be used to
               disable those extensions that have been omitted.  For
               floating-point and Advanced SIMD (Neon) instructions, the
               settings of the options **-mfloat-abi** and **-mfpu** must also be
               considered: floating-point and Advanced SIMD instructions will
               only be used if **-mfloat-abi** is not set to **soft** ; and any
               setting of **-mfpu** other than **auto** will override the available
               floating-point and SIMD extension instructions.
    
               For example, **cortex-a9** can be found in three major
               configurations: integer only, with just a floating-point unit
               or with floating-point and Advanced SIMD.  The default is to
               enable all the instructions, but the extensions **+nosimd** and
               **+nofp** can be used to disable just the SIMD or both the SIMD
               and floating-point instructions respectively.
    
               Permissible names for this option are the same as those for
               **-mtune**.
    
               The following extension options are common to the listed CPUs:
    
               **+nodsp**
                   Disable the DSP instructions on **cortex-m33**.
    
               **+nofp**
                   Disables the floating-point instructions on **arm9e** ,
                   **arm946e-s** , **arm966e-s** , **arm968e-s** , **arm10e** , **arm1020e** ,
                   **arm1022e** , **arm926ej-s** , **arm1026ej-s** , **cortex-r5** , **cortex-r7** ,
                   **cortex-r8** , **cortex-m4** , **cortex-m7** and **cortex-m33**.  Disables
                   the floating-point and SIMD instructions on
                   **generic-armv7-a** , **cortex-a5** , **cortex-a7** , **cortex-a8** ,
                   **cortex-a9** , **cortex-a12** , **cortex-a15** , **cortex-a17** ,
                   **cortex-a15.cortex-a7** , **cortex-a17.cortex-a7** , **cortex-a32** ,
                   **cortex-a35** , **cortex-a53** and **cortex-a55**.
    
               **+nofp.dp**
                   Disables the double-precision component of the floating-
                   point instructions on **cortex-r5** , **cortex-r7** , **cortex-r8** ,
                   **cortex-r52** and **cortex-m7**.
    
               **+nosimd**
                   Disables the SIMD (but not floating-point) instructions on
                   **generic-armv7-a** , **cortex-a5** , **cortex-a7** and **cortex-a9**.
    
               **+crypto**
                   Enables the cryptographic instructions on **cortex-a32** ,
                   **cortex-a35** , **cortex-a53** , **cortex-a55** , **cortex-a57** ,
                   **cortex-a72** , **cortex-a73** , **cortex-a75** , **exynos-m1** , **xgene1** ,
                   **cortex-a57.cortex-a53** , **cortex-a72.cortex-a53** ,
                   **cortex-a73.cortex-a35** , **cortex-a73.cortex-a53** and
                   **cortex-a75.cortex-a55**.
    
               Additionally the **generic-armv7-a** pseudo target defaults to
               VFPv3 with 16 double-precision registers.  It supports the
               following extension options: **mp** , **sec** , **vfpv3-d16** , **vfpv3** ,
               **vfpv3-d16-fp16** , **vfpv3-fp16** , **vfpv4-d16** , **vfpv4** , **neon** ,
               **neon-vfpv3** , **neon-fp16** , **neon-vfpv4**.  The meanings are the same
               as for the extensions to **-march=armv7-a**.
    
               **-mcpu=generic-**_arch_ is also permissible, and is equivalent to
               **-march=**_arch_ **-mtune=generic-**_arch_.  See **-mtune** for more
               information.
    
               **-mcpu=native** causes the compiler to auto-detect the CPU of the
               build computer.  At present, this feature is only supported on
               GNU/Linux, and not all architectures are recognized.  If the
               auto-detect is unsuccessful the option has no effect.
    
           **-mfpu=**_name_
               This specifies what floating-point hardware (or hardware
               emulation) is available on the target.  Permissible names are:
               **auto** , **vfpv2** , **vfpv3** , **vfpv3-fp16** , **vfpv3-d16** , **vfpv3-d16-fp16** ,
               **vfpv3xd** , **vfpv3xd-fp16** , **neon-vfpv3** , **neon-fp16** , **vfpv4** ,
               **vfpv4-d16** , **fpv4-sp-d16** , **neon-vfpv4** , **fpv5-d16** , **fpv5-sp-d16** ,
               **fp-armv8** , **neon-fp-armv8** and **crypto-neon-fp-armv8**.  Note that
               **neon** is an alias for **neon-vfpv3** and **vfp** is an alias for **vfpv2**.
    
               The setting **auto** is the default and is special.  It causes the
               compiler to select the floating-point and Advanced SIMD
               instructions based on the settings of **-mcpu** and **-march**.
    
               If the selected floating-point hardware includes the NEON
               extension (e.g. **-mfpu=neon**), note that floating-point
               operations are not generated by GCC's auto-vectorization pass
               unless **-funsafe-math-optimizations** is also specified.  This is
               because NEON hardware does not fully implement the IEEE 754
               standard for floating-point arithmetic (in particular denormal
               values are treated as zero), so the use of NEON instructions
               may lead to a loss of precision.
    
               You can also set the fpu name at function level by using the
               "target("fpu=")" function attributes or pragmas.
    
           **-mfp16-format=**_name_
               Specify the format of the "__fp16" half-precision floating-
               point type.  Permissible names are **none** , **ieee** , and
               **alternative** ; the default is **none** , in which case the "__fp16"
               type is not defined.
    
           **-mstructure-size-boundary=**_n_
               The sizes of all structures and unions are rounded up to a
               multiple of the number of bits set by this option.
               Permissible values are 8, 32 and 64.  The default value varies
               for different toolchains.  For the COFF targeted toolchain the
               default value is 8.  A value of 64 is only allowed if the
               underlying ABI supports it.
    
               Specifying a larger number can produce faster, more efficient
               code, but can also increase the size of the program.
               Different values are potentially incompatible.  Code compiled
               with one value cannot necessarily expect to work with code or
               libraries compiled with another value, if they exchange
               information using structures or unions.
    
               This option is deprecated.
    
           **-mabort-on-noreturn**
               Generate a call to the function "abort" at the end of a
               "noreturn" function.  It is executed if the function tries to
               return.
    
           **-mlong-calls**
           **-mno-long-calls**
               Tells the compiler to perform function calls by first loading
               the address of the function into a register and then
               performing a subroutine call on this register.  This switch is
               needed if the target function lies outside of the 64-megabyte
               addressing range of the offset-based version of subroutine
               call instruction.
    
               Even if this switch is enabled, not all function calls are
               turned into long calls.  The heuristic is that static
               functions, functions that have the "short_call" attribute,
               functions that are inside the scope of a "#pragma
               no_long_calls" directive, and functions whose definitions have
               already been compiled within the current compilation unit are
               not turned into long calls.  The exceptions to this rule are
               that weak function definitions, functions with the "long_call"
               attribute or the "section" attribute, and functions that are
               within the scope of a "#pragma long_calls" directive are
               always turned into long calls.
    
               This feature is not enabled by default.  Specifying
               **-mno-long-calls** restores the default behavior, as does placing
               the function calls within the scope of a "#pragma
               long_calls_off" directive.  Note these switches have no effect
               on how the compiler generates code to handle function calls
               via function pointers.
    
           **-msingle-pic-base**
               Treat the register used for PIC addressing as read-only,
               rather than loading it in the prologue for each function.  The
               runtime system is responsible for initializing this register
               with an appropriate value before execution begins.
    
           **-mpic-register=**_reg_
               Specify the register to be used for PIC addressing.  For
               standard PIC base case, the default is any suitable register
               determined by compiler.  For single PIC base case, the default
               is **R9** if target is EABI based or stack-checking is enabled,
               otherwise the default is **R10**.
    
           **-mpic-data-is-text-relative**
               Assume that the displacement between the text and data
               segments is fixed at static link time.  This permits using PC-
               relative addressing operations to access data known to be in
               the data segment.  For non-VxWorks RTP targets, this option is
               enabled by default.  When disabled on such targets, it will
               enable **-msingle-pic-base** by default.
    
           **-mpoke-function-name**
               Write the name of each function into the text section,
               directly preceding the function prologue.  The generated code
               is similar to this:
    
                            t0
                                .ascii "arm_poke_function_name", 0
                                .align
                            t1
                                .word 0xff000000 + (t1 - t0)
                            arm_poke_function_name
                                mov     ip, sp
                                stmfd   sp!, {fp, ip, lr, pc}
                                sub     fp, ip, #4
    
               When performing a stack backtrace, code can inspect the value
               of "pc" stored at "fp + 0".  If the trace function then looks
               at location "pc - 12" and the top 8 bits are set, then we know
               that there is a function name embedded immediately preceding
               this location and has length "((pc[-3]) & 0xff000000)".
    
           **-mthumb**
           **-marm**
               Select between generating code that executes in ARM and Thumb
               states.  The default for most configurations is to generate
               code that executes in ARM state, but the default can be
               changed by configuring GCC with the **--with-mode=**_state_
               configure option.
    
               You can also override the ARM and Thumb mode for each function
               by using the "target("thumb")" and "target("arm")" function
               attributes or pragmas.
    
           **-mflip-thumb**
               Switch ARM/Thumb modes on alternating functions.  This option
               is provided for regression testing of mixed Thumb/ARM code
               generation, and is not intended for ordinary use in compiling
               code.
    
           **-mtpcs-frame**
               Generate a stack frame that is compliant with the Thumb
               Procedure Call Standard for all non-leaf functions.  (A leaf
               function is one that does not call any other functions.)  The
               default is **-mno-tpcs-frame**.
    
           **-mtpcs-leaf-frame**
               Generate a stack frame that is compliant with the Thumb
               Procedure Call Standard for all leaf functions.  (A leaf
               function is one that does not call any other functions.)  The
               default is **-mno-apcs-leaf-frame**.
    
           **-mcallee-super-interworking**
               Gives all externally visible functions in the file being
               compiled an ARM instruction set header which switches to Thumb
               mode before executing the rest of the function.  This allows
               these functions to be called from non-interworking code.  This
               option is not valid in AAPCS configurations because
               interworking is enabled by default.
    
           **-mcaller-super-interworking**
               Allows calls via function pointers (including virtual
               functions) to execute correctly regardless of whether the
               target code has been compiled for interworking or not.  There
               is a small overhead in the cost of executing a function
               pointer if this option is enabled.  This option is not valid
               in AAPCS configurations because interworking is enabled by
               default.
    
           **-mtp=**_name_
               Specify the access model for the thread local storage pointer.
               The valid models are **soft** , which generates calls to
               "__aeabi_read_tp", **cp15** , which fetches the thread pointer from
               "cp15" directly (supported in the arm6k architecture), and
               **auto** , which uses the best available method for the selected
               processor.  The default setting is **auto**.
    
           **-mtls-dialect=**_dialect_
               Specify the dialect to use for accessing thread local storage.
               Two _dialect_ s are supported---**gnu** and **gnu2**.  The **gnu** dialect
               selects the original GNU scheme for supporting local and
               global dynamic TLS models.  The **gnu2** dialect selects the GNU
               descriptor scheme, which provides better performance for
               shared libraries.  The GNU descriptor scheme is compatible
               with the original scheme, but does require new assembler,
               linker and library support.  Initial and local exec TLS models
               are unaffected by this option and always use the original
               scheme.
    
           **-mword-relocations**
               Only generate absolute relocations on word-sized values (i.e.
               R_ARM_ABS32).  This is enabled by default on targets (uClinux,
               SymbianOS) where the runtime loader imposes this restriction,
               and when **-fpic** or **-fPIC** is specified. This option conflicts
               with **-mslow-flash-data**.
    
           **-mfix-cortex-m3-ldrd**
               Some Cortex-M3 cores can cause data corruption when "ldrd"
               instructions with overlapping destination and base registers
               are used.  This option avoids generating these instructions.
               This option is enabled by default when **-mcpu=cortex-m3** is
               specified.
    
           **-munaligned-access**
           **-mno-unaligned-access**
               Enables (or disables) reading and writing of 16- and 32- bit
               values from addresses that are not 16- or 32- bit aligned.  By
               default unaligned access is disabled for all pre-ARMv6, all
               ARMv6-M and for ARMv8-M Baseline architectures, and enabled
               for all other architectures.  If unaligned access is not
               enabled then words in packed data structures are accessed a
               byte at a time.
    
               The ARM attribute "Tag_CPU_unaligned_access" is set in the
               generated object file to either true or false, depending upon
               the setting of this option.  If unaligned access is enabled
               then the preprocessor symbol "__ARM_FEATURE_UNALIGNED" is also
               defined.
    
           **-mneon-for-64bits**
               Enables using Neon to handle scalar 64-bits operations. This
               is disabled by default since the cost of moving data from core
               registers to Neon is high.
    
           **-mslow-flash-data**
               Assume loading data from flash is slower than fetching
               instruction.  Therefore literal load is minimized for better
               performance.  This option is only supported when compiling for
               ARMv7 M-profile and off by default. It conflicts with
               **-mword-relocations**.
    
           **-masm-syntax-unified**
               Assume inline assembler is using unified asm syntax.  The
               default is currently off which implies divided syntax.  This
               option has no impact on Thumb2. However, this may change in
               future releases of GCC.  Divided syntax should be considered
               deprecated.
    
           **-mrestrict-it**
               Restricts generation of IT blocks to conform to the rules of
               ARMv8-A.  IT blocks can only contain a single 16-bit
               instruction from a select set of instructions. This option is
               on by default for ARMv8-A Thumb mode.
    
           **-mprint-tune-info**
               Print CPU tuning information as comment in assembler file.
               This is an option used only for regression testing of the
               compiler and not intended for ordinary use in compiling code.
               This option is disabled by default.
    
           **-mverbose-cost-dump**
               Enable verbose cost model dumping in the debug dump files.
               This option is provided for use in debugging the compiler.
    
           **-mpure-code**
               Do not allow constant data to be placed in code sections.
               Additionally, when compiling for ELF object format give all
               text sections the ELF processor-specific section attribute
               "SHF_ARM_PURECODE".  This option is only available when
               generating non-pic code for M-profile targets.
    
           **-mcmse**
               Generate secure code as per the "ARMv8-M Security Extensions:
               Requirements on Development Tools Engineering Specification",
               which can be found on
               <**https://developer.arm.com/documentation/ecm0359818/latest/ **>.
    
           _AVR Options_
    
           These options are defined for AVR implementations:
    
           **-mmcu=**_mcu_
               Specify Atmel AVR instruction set architectures (ISA) or MCU
               type.
    
               The default for this option is **avr2**.
    
               GCC supports the following AVR devices and ISAs:
    
               "avr2"
                   "Classic" devices with up to 8 KiB of program memory.  _mcu_
                   = "attiny22", "attiny26", "at90s2313", "at90s2323",
                   "at90s2333", "at90s2343", "at90s4414", "at90s4433",
                   "at90s4434", "at90c8534", "at90s8515", "at90s8535".
    
               "avr25"
                   "Classic" devices with up to 8 KiB of program memory and
                   with the "MOVW" instruction.  _mcu_ = "attiny13",
                   "attiny13a", "attiny24", "attiny24a", "attiny25",
                   "attiny261", "attiny261a", "attiny2313", "attiny2313a",
                   "attiny43u", "attiny44", "attiny44a", "attiny45",
                   "attiny48", "attiny441", "attiny461", "attiny461a",
                   "attiny4313", "attiny84", "attiny84a", "attiny85",
                   "attiny87", "attiny88", "attiny828", "attiny841",
                   "attiny861", "attiny861a", "ata5272", "ata6616c",
                   "at86rf401".
    
               "avr3"
                   "Classic" devices with 16 KiB up to 64 KiB of program
                   memory.  _mcu_ = "at76c711", "at43usb355".
    
               "avr31"
                   "Classic" devices with 128 KiB of program memory.  _mcu_ =
                   "atmega103", "at43usb320".
    
               "avr35"
                   "Classic" devices with 16 KiB up to 64 KiB of program
                   memory and with the "MOVW" instruction.  _mcu_ =
                   "attiny167", "attiny1634", "atmega8u2", "atmega16u2",
                   "atmega32u2", "ata5505", "ata6617c", "ata664251",
                   "at90usb82", "at90usb162".
    
               "avr4"
                   "Enhanced" devices with up to 8 KiB of program memory.
                   _mcu_ = "atmega48", "atmega48a", "atmega48p", "atmega48pa",
                   "atmega48pb", "atmega8", "atmega8a", "atmega8hva",
                   "atmega88", "atmega88a", "atmega88p", "atmega88pa",
                   "atmega88pb", "atmega8515", "atmega8535", "ata6285",
                   "ata6286", "ata6289", "ata6612c", "at90pwm1", "at90pwm2",
                   "at90pwm2b", "at90pwm3", "at90pwm3b", "at90pwm81".
    
               "avr5"
                   "Enhanced" devices with 16 KiB up to 64 KiB of program
                   memory.  _mcu_ = "atmega16", "atmega16a", "atmega16hva",
                   "atmega16hva2", "atmega16hvb", "atmega16hvbrevb",
                   "atmega16m1", "atmega16u4", "atmega161", "atmega162",
                   "atmega163", "atmega164a", "atmega164p", "atmega164pa",
                   "atmega165", "atmega165a", "atmega165p", "atmega165pa",
                   "atmega168", "atmega168a", "atmega168p", "atmega168pa",
                   "atmega168pb", "atmega169", "atmega169a", "atmega169p",
                   "atmega169pa", "atmega32", "atmega32a", "atmega32c1",
                   "atmega32hvb", "atmega32hvbrevb", "atmega32m1",
                   "atmega32u4", "atmega32u6", "atmega323", "atmega324a",
                   "atmega324p", "atmega324pa", "atmega325", "atmega325a",
                   "atmega325p", "atmega325pa", "atmega328", "atmega328p",
                   "atmega328pb", "atmega329", "atmega329a", "atmega329p",
                   "atmega329pa", "atmega3250", "atmega3250a", "atmega3250p",
                   "atmega3250pa", "atmega3290", "atmega3290a",
                   "atmega3290p", "atmega3290pa", "atmega406", "atmega64",
                   "atmega64a", "atmega64c1", "atmega64hve", "atmega64hve2",
                   "atmega64m1", "atmega64rfr2", "atmega640", "atmega644",
                   "atmega644a", "atmega644p", "atmega644pa",
                   "atmega644rfr2", "atmega645", "atmega645a", "atmega645p",
                   "atmega649", "atmega649a", "atmega649p", "atmega6450",
                   "atmega6450a", "atmega6450p", "atmega6490", "atmega6490a",
                   "atmega6490p", "ata5795", "ata5790", "ata5790n",
                   "ata5791", "ata6613c", "ata6614q", "ata5782", "ata5831",
                   "ata8210", "ata8510", "ata5702m322", "at90pwm161",
                   "at90pwm216", "at90pwm316", "at90can32", "at90can64",
                   "at90scr100", "at90usb646", "at90usb647", "at94k",
                   "m3000".
    
               "avr51"
                   "Enhanced" devices with 128 KiB of program memory.  _mcu_ =
                   "atmega128", "atmega128a", "atmega128rfa1",
                   "atmega128rfr2", "atmega1280", "atmega1281", "atmega1284",
                   "atmega1284p", "atmega1284rfr2", "at90can128",
                   "at90usb1286", "at90usb1287".
    
               "avr6"
                   "Enhanced" devices with 3-byte PC, i.e. with more than 128
                   KiB of program memory.  _mcu_ = "atmega256rfr2",
                   "atmega2560", "atmega2561", "atmega2564rfr2".
    
               "avrxmega2"
                   "XMEGA" devices with more than 8 KiB and up to 64 KiB of
                   program memory.  _mcu_ = "atxmega8e5", "atxmega16a4",
                   "atxmega16a4u", "atxmega16c4", "atxmega16d4",
                   "atxmega16e5", "atxmega32a4", "atxmega32a4u",
                   "atxmega32c3", "atxmega32c4", "atxmega32d3",
                   "atxmega32d4", "atxmega32e5".
    
               "avrxmega3"
                   "XMEGA" devices with up to 64 KiB of combined program
                   memory and RAM, and with program memory visible in the RAM
                   address space.  _mcu_ = "attiny202", "attiny204",
                   "attiny212", "attiny214", "attiny402", "attiny404",
                   "attiny406", "attiny412", "attiny414", "attiny416",
                   "attiny417", "attiny804", "attiny806", "attiny807",
                   "attiny814", "attiny816", "attiny817", "attiny1604",
                   "attiny1606", "attiny1607", "attiny1614", "attiny1616",
                   "attiny1617", "attiny3214", "attiny3216", "attiny3217",
                   "atmega808", "atmega809", "atmega1608", "atmega1609",
                   "atmega3208", "atmega3209", "atmega4808", "atmega4809".
    
               "avrxmega4"
                   "XMEGA" devices with more than 64 KiB and up to 128 KiB of
                   program memory.  _mcu_ = "atxmega64a3", "atxmega64a3u",
                   "atxmega64a4u", "atxmega64b1", "atxmega64b3",
                   "atxmega64c3", "atxmega64d3", "atxmega64d4".
    
               "avrxmega5"
                   "XMEGA" devices with more than 64 KiB and up to 128 KiB of
                   program memory and more than 64 KiB of RAM.  _mcu_ =
                   "atxmega64a1", "atxmega64a1u".
    
               "avrxmega6"
                   "XMEGA" devices with more than 128 KiB of program memory.
                   _mcu_ = "atxmega128a3", "atxmega128a3u", "atxmega128b1",
                   "atxmega128b3", "atxmega128c3", "atxmega128d3",
                   "atxmega128d4", "atxmega192a3", "atxmega192a3u",
                   "atxmega192c3", "atxmega192d3", "atxmega256a3",
                   "atxmega256a3b", "atxmega256a3bu", "atxmega256a3u",
                   "atxmega256c3", "atxmega256d3", "atxmega384c3",
                   "atxmega384d3".
    
               "avrxmega7"
                   "XMEGA" devices with more than 128 KiB of program memory
                   and more than 64 KiB of RAM.  _mcu_ = "atxmega128a1",
                   "atxmega128a1u", "atxmega128a4u".
    
               "avrtiny"
                   "TINY" Tiny core devices with 512 B up to 4 KiB of program
                   memory.  _mcu_ = "attiny4", "attiny5", "attiny9",
                   "attiny10", "attiny20", "attiny40".
    
               "avr1"
                   This ISA is implemented by the minimal AVR core and
                   supported for assembler only.  _mcu_ = "attiny11",
                   "attiny12", "attiny15", "attiny28", "at90s1200".
    
           **-mabsdata**
               Assume that all data in static storage can be accessed by LDS
               / STS instructions.  This option has only an effect on reduced
               Tiny devices like ATtiny40.  See also the "absdata" **AVR**
               **Variable Attributes,variable attribute**.
    
           **-maccumulate-args**
               Accumulate outgoing function arguments and acquire/release the
               needed stack space for outgoing function arguments once in
               function prologue/epilogue.  Without this option, outgoing
               arguments are pushed before calling a function and popped
               afterwards.
    
               Popping the arguments after the function call can be expensive
               on AVR so that accumulating the stack space might lead to
               smaller executables because arguments need not be removed from
               the stack after such a function call.
    
               This option can lead to reduced code size for functions that
               perform several calls to functions that get their arguments on
               the stack like calls to printf-like functions.
    
           **-mbranch-cost=**_cost_
               Set the branch costs for conditional branch instructions to
               _cost_.  Reasonable values for _cost_ are small, non-negative
               integers. The default branch cost is 0.
    
           **-mcall-prologues**
               Functions prologues/epilogues are expanded as calls to
               appropriate subroutines.  Code size is smaller.
    
           **-mgas-isr-prologues**
               Interrupt service routines (ISRs) may use the "__gcc_isr"
               pseudo instruction supported by GNU Binutils.  If this option
               is on, the feature can still be disabled for individual ISRs
               by means of the **AVR Function Attributes,,"no_gccisr"** function
               attribute.  This feature is activated per default if
               optimization is on (but not with **-Og** , @pxref{Optimize
               Options}), and if GNU Binutils support PR21683
               ("https://sourceware.org/PR21683").
    
           **-mint8**
               Assume "int" to be 8-bit integer.  This affects the sizes of
               all types: a "char" is 1 byte, an "int" is 1 byte, a "long" is
               2 bytes, and "long long" is 4 bytes.  Please note that this
               option does not conform to the C standards, but it results in
               smaller code size.
    
           **-mmain-is-OS_task**
               Do not save registers in "main".  The effect is the same like
               attaching attribute **AVR Function Attributes,,"OS_task"** to
               "main". It is activated per default if optimization is on.
    
           **-mn-flash=**_num_
               Assume that the flash memory has a size of _num_ times 64 KiB.
    
           **-mno-interrupts**
               Generated code is not compatible with hardware interrupts.
               Code size is smaller.
    
           **-mrelax**
               Try to replace "CALL" resp. "JMP" instruction by the shorter
               "RCALL" resp. "RJMP" instruction if applicable.  Setting
               **-mrelax** just adds the **--mlink-relax** option to the assembler's
               command line and the **--relax** option to the linker's command
               line.
    
               Jump relaxing is performed by the linker because jump offsets
               are not known before code is located. Therefore, the assembler
               code generated by the compiler is the same, but the
               instructions in the executable may differ from instructions in
               the assembler code.
    
               Relaxing must be turned on if linker stubs are needed, see the
               section on "EIND" and linker stubs below.
    
           **-mrmw**
               Assume that the device supports the Read-Modify-Write
               instructions "XCH", "LAC", "LAS" and "LAT".
    
           **-mshort-calls**
               Assume that "RJMP" and "RCALL" can target the whole program
               memory.
    
               This option is used internally for multilib selection.  It is
               not an optimization option, and you don't need to set it by
               hand.
    
           **-msp8**
               Treat the stack pointer register as an 8-bit register, i.e.
               assume the high byte of the stack pointer is zero.  In
               general, you don't need to set this option by hand.
    
               This option is used internally by the compiler to select and
               build multilibs for architectures "avr2" and "avr25".  These
               architectures mix devices with and without "SPH".  For any
               setting other than **-mmcu=avr2** or **-mmcu=avr25** the compiler
               driver adds or removes this option from the compiler proper's
               command line, because the compiler then knows if the device or
               architecture has an 8-bit stack pointer and thus no "SPH"
               register or not.
    
           **-mstrict-X**
               Use address register "X" in a way proposed by the hardware.
               This means that "X" is only used in indirect, post-increment
               or pre-decrement addressing.
    
               Without this option, the "X" register may be used in the same
               way as "Y" or "Z" which then is emulated by additional
               instructions.  For example, loading a value with "X+const"
               addressing with a small non-negative "const < 64" to a
               register _Rn_ is performed as
    
                       adiw r26, const   ; X += const
                       ld   <Rn>, X        ; <Rn> = *X
                       sbiw r26, const   ; X -= const
    
           **-mtiny-stack**
               Only change the lower 8 bits of the stack pointer.
    
           **-mfract-convert-truncate**
               Allow to use truncation instead of rounding towards zero for
               fractional fixed-point types.
    
           **-nodevicelib**
               Don't link against AVR-LibC's device specific library
               "lib<mcu>.a".
    
           **-nodevicespecs**
               Don't add **-specs=device-specs/specs- <mcu> **to the compiler
               driver's command line.  The user takes responsibility for
               supplying the sub-processes like compiler proper, assembler
               and linker with appropriate command line options.
    
           **-Waddr-space-convert**
               Warn about conversions between address spaces in the case
               where the resulting address space is not contained in the
               incoming address space.
    
           **-Wmisspelled-isr**
               Warn if the ISR is misspelled, i.e. without __vector prefix.
               Enabled by default.
    
           "EIND" and Devices with More Than 128 Ki Bytes of Flash
    
           Pointers in the implementation are 16 bits wide.  The address of a
           function or label is represented as word address so that indirect
           jumps and calls can target any code address in the range of 64 Ki
           words.
    
           In order to facilitate indirect jump on devices with more than 128
           Ki bytes of program memory space, there is a special function
           register called "EIND" that serves as most significant part of the
           target address when "EICALL" or "EIJMP" instructions are used.
    
           Indirect jumps and calls on these devices are handled as follows
           by the compiler and are subject to some limitations:
    
           *   The compiler never sets "EIND".
    
           *   The compiler uses "EIND" implicitly in "EICALL"/"EIJMP"
               instructions or might read "EIND" directly in order to emulate
               an indirect call/jump by means of a "RET" instruction.
    
           *   The compiler assumes that "EIND" never changes during the
               startup code or during the application. In particular, "EIND"
               is not saved/restored in function or interrupt service routine
               prologue/epilogue.
    
           *   For indirect calls to functions and computed goto, the linker
               generates _stubs_. Stubs are jump pads sometimes also called
               _trampolines_. Thus, the indirect call/jump jumps to such a
               stub.  The stub contains a direct jump to the desired address.
    
           *   Linker relaxation must be turned on so that the linker
               generates the stubs correctly in all situations. See the
               compiler option **-mrelax** and the linker option **--relax**.  There
               are corner cases where the linker is supposed to generate
               stubs but aborts without relaxation and without a helpful
               error message.
    
           *   The default linker script is arranged for code with "EIND =
               0".  If code is supposed to work for a setup with "EIND != 0",
               a custom linker script has to be used in order to place the
               sections whose name start with ".trampolines" into the segment
               where "EIND" points to.
    
           *   The startup code from libgcc never sets "EIND".  Notice that
               startup code is a blend of code from libgcc and AVR-LibC.  For
               the impact of AVR-LibC on "EIND", see the AVR-LibC user manual
               ("http://nongnu.org/avr-libc/user-manual/").
    
           *   It is legitimate for user-specific startup code to set up
               "EIND" early, for example by means of initialization code
               located in section ".init3". Such code runs prior to general
               startup code that initializes RAM and calls constructors, but
               after the bit of startup code from AVR-LibC that sets "EIND"
               to the segment where the vector table is located.
    
                       #include <avr/io.h>
    
                       static void
                       __attribute__((section(".init3"),naked,used,no_instrument_function))
                       init3_set_eind (void)
                       {
                         __asm volatile ("ldi r24,pm_hh8(__trampolines_start)\n\t"
                                         "out %i0,r24" :: "n" (&EIND) : "r24","memory");
                       }
    
               The "__trampolines_start" symbol is defined in the linker
               script.
    
           *   Stubs are generated automatically by the linker if the
               following two conditions are met:
    
               -<The address of a label is taken by means of the "gs"
               modifier>
                   (short for _generate stubs_) like so:
    
                           LDI r24, lo8(gs(<func>))
                           LDI r25, hi8(gs(<func>))
    
               -<The final location of that label is in a code segment>
                   _outside_ the segment where the stubs are located.
    
           *   The compiler emits such "gs" modifiers for code labels in the
               following situations:
    
               -<Taking address of a function or code label.>
               -<Computed goto.>
               -<If prologue-save function is used, see **-mcall-prologues** >
                   command-line option.
    
               -<Switch/case dispatch tables. If you do not want such
               dispatch>
                   tables you can specify the **-fno-jump-tables** command-line
                   option.
    
               -<C and C++ constructors/destructors called during
               startup/shutdown.>
               -<If the tools hit a "gs()" modifier explained above.>
           *   Jumping to non-symbolic addresses like so is _not_ supported:
    
                       int main (void)
                       {
                           /* Call function at word address 0x2 */
                           return ((int(*)(void)) 0x2)();
                       }
    
               Instead, a stub has to be set up, i.e. the function has to be
               called through a symbol ("func_4" in the example):
    
                       int main (void)
                       {
                           extern int func_4 (void);
    
                           /* Call function at byte address 0x4 */
                           return func_4();
                       }
    
               and the application be linked with **-Wl,--defsym,func_4=0x4**.
               Alternatively, "func_4" can be defined in the linker script.
    
           Handling of the "RAMPD", "RAMPX", "RAMPY" and "RAMPZ" Special
           Function Registers
    
           Some AVR devices support memories larger than the 64 KiB range
           that can be accessed with 16-bit pointers.  To access memory
           locations outside this 64 KiB range, the content of a "RAMP"
           register is used as high part of the address: The "X", "Y", "Z"
           address register is concatenated with the "RAMPX", "RAMPY",
           "RAMPZ" special function register, respectively, to get a wide
           address. Similarly, "RAMPD" is used together with direct
           addressing.
    
           *   The startup code initializes the "RAMP" special function
               registers with zero.
    
           *   If a **AVR Named Address Spaces,named address space** other than
               generic or "__flash" is used, then "RAMPZ" is set as needed
               before the operation.
    
           *   If the device supports RAM larger than 64 KiB and the compiler
               needs to change "RAMPZ" to accomplish an operation, "RAMPZ" is
               reset to zero after the operation.
    
           *   If the device comes with a specific "RAMP" register, the ISR
               prologue/epilogue saves/restores that SFR and initializes it
               with zero in case the ISR code might (implicitly) use it.
    
           *   RAM larger than 64 KiB is not supported by GCC for AVR
               targets.  If you use inline assembler to read from locations
               outside the 16-bit address range and change one of the "RAMP"
               registers, you must reset it to zero after the access.
    
           AVR Built-in Macros
    
           GCC defines several built-in macros so that the user code can test
           for the presence or absence of features.  Almost any of the
           following built-in macros are deduced from device capabilities and
           thus triggered by the **-mmcu=** command-line option.
    
           For even more AVR-specific built-in macros see **AVR Named Address**
           **Spaces** and **AVR Built-in Functions**.
    
           "__AVR_ARCH__"
               Build-in macro that resolves to a decimal number that
               identifies the architecture and depends on the **-mmcu=**_mcu_
               option.  Possible values are:
    
               2, 25, 3, 31, 35, 4, 5, 51, 6
    
               for _mcu_ ="avr2", "avr25", "avr3", "avr31", "avr35", "avr4",
               "avr5", "avr51", "avr6",
    
               respectively and
    
               100, 102, 103, 104, 105, 106, 107
    
               for _mcu_ ="avrtiny", "avrxmega2", "avrxmega3", "avrxmega4",
               "avrxmega5", "avrxmega6", "avrxmega7", respectively.  If _mcu_
               specifies a device, this built-in macro is set accordingly.
               For example, with **-mmcu=atmega8** the macro is defined to 4.
    
           "__AVR__Device_ __"
               Setting **-mmcu=**_device_ defines this built-in macro which
               reflects the device's name. For example, **-mmcu=atmega8** defines
               the built-in macro "__AVR_ATmega8__", **-mmcu=attiny261a** defines
               "__AVR_ATtiny261A__", etc.
    
               The built-in macros' names follow the scheme "__AVR__Device__"_
               where _Device_ is the device name as from the AVR user manual.
               The difference between _Device_ in the built-in macro and _device_
               in **-mmcu=**_device_ is that the latter is always lowercase.
    
               If _device_ is not a device but only a core architecture like
               **avr51** , this macro is not defined.
    
           "__AVR_DEVICE_NAME__"
               Setting **-mmcu=**_device_ defines this built-in macro to the
               device's name. For example, with **-mmcu=atmega8** the macro is
               defined to "atmega8".
    
               If _device_ is not a device but only a core architecture like
               **avr51** , this macro is not defined.
    
           "__AVR_XMEGA__"
               The device / architecture belongs to the XMEGA family of
               devices.
    
           "__AVR_HAVE_ELPM__"
               The device has the "ELPM" instruction.
    
           "__AVR_HAVE_ELPMX__"
               The device has the "ELPM R _n,Z"_ and "ELPM R _n,Z+"_ instructions.
    
           "__AVR_HAVE_MOVW__"
               The device has the "MOVW" instruction to perform 16-bit
               register-register moves.
    
           "__AVR_HAVE_LPMX__"
               The device has the "LPM R _n,Z"_ and "LPM R _n,Z+"_ instructions.
    
           "__AVR_HAVE_MUL__"
               The device has a hardware multiplier.
    
           "__AVR_HAVE_JMP_CALL__"
               The device has the "JMP" and "CALL" instructions.  This is the
               case for devices with more than 8 KiB of program memory.
    
           "__AVR_HAVE_EIJMP_EICALL__"
           "__AVR_3_BYTE_PC__"
               The device has the "EIJMP" and "EICALL" instructions.  This is
               the case for devices with more than 128 KiB of program memory.
               This also means that the program counter (PC) is 3 bytes wide.
    
           "__AVR_2_BYTE_PC__"
               The program counter (PC) is 2 bytes wide. This is the case for
               devices with up to 128 KiB of program memory.
    
           "__AVR_HAVE_8BIT_SP__"
           "__AVR_HAVE_16BIT_SP__"
               The stack pointer (SP) register is treated as 8-bit
               respectively 16-bit register by the compiler.  The definition
               of these macros is affected by **-mtiny-stack**.
    
           "__AVR_HAVE_SPH__"
           "__AVR_SP8__"
               The device has the SPH (high part of stack pointer) special
               function register or has an 8-bit stack pointer, respectively.
               The definition of these macros is affected by **-mmcu=** and in
               the cases of **-mmcu=avr2** and **-mmcu=avr25** also by **-msp8**.
    
           "__AVR_HAVE_RAMPD__"
           "__AVR_HAVE_RAMPX__"
           "__AVR_HAVE_RAMPY__"
           "__AVR_HAVE_RAMPZ__"
               The device has the "RAMPD", "RAMPX", "RAMPY", "RAMPZ" special
               function register, respectively.
    
           "__NO_INTERRUPTS__"
               This macro reflects the **-mno-interrupts** command-line option.
    
           "__AVR_ERRATA_SKIP__"
           "__AVR_ERRATA_SKIP_JMP_CALL__"
               Some AVR devices (AT90S8515, ATmega103) must not skip 32-bit
               instructions because of a hardware erratum.  Skip instructions
               are "SBRS", "SBRC", "SBIS", "SBIC" and "CPSE".  The second
               macro is only defined if "__AVR_HAVE_JMP_CALL__" is also set.
    
           "__AVR_ISA_RMW__"
               The device has Read-Modify-Write instructions (XCH, LAC, LAS
               and LAT).
    
           "__AVR_SFR_OFFSET__=_offset_ "
               Instructions that can address I/O special function registers
               directly like "IN", "OUT", "SBI", etc. may use a different
               address as if addressed by an instruction to access RAM like
               "LD" or "STS". This offset depends on the device architecture
               and has to be subtracted from the RAM address in order to get
               the respective I/O address.
    
           "__AVR_SHORT_CALLS__"
               The **-mshort-calls** command line option is set.
    
           "__AVR_PM_BASE_ADDRESS__=_addr_ "
               Some devices support reading from flash memory by means of
               "LD*" instructions.  The flash memory is seen in the data
               address space at an offset of "__AVR_PM_BASE_ADDRESS__".  If
               this macro is not defined, this feature is not available.  If
               defined, the address space is linear and there is no need to
               put ".rodata" into RAM.  This is handled by the default linker
               description file, and is currently available for "avrtiny" and
               "avrxmega3".  Even more convenient, there is no need to use
               address spaces like "__flash" or features like attribute
               "progmem" and "pgm_read_*".
    
           "__WITH_AVRLIBC__"
               The compiler is configured to be used together with AVR-Libc.
               See the **--with-avrlibc** configure option.
    
           _Blackfin Options_
    
           **-mcpu=**_cpu_[**-**_sirevision_]
               Specifies the name of the target Blackfin processor.
               Currently, _cpu_ can be one of **bf512** , **bf514** , **bf516** , **bf518** ,
               **bf522** , **bf523** , **bf524** , **bf525** , **bf526** , **bf527** , **bf531** , **bf532** , **bf533** ,
               **bf534** , **bf536** , **bf537** , **bf538** , **bf539** , **bf542** , **bf544** , **bf547** , **bf548** ,
               **bf549** , **bf542m** , **bf544m** , **bf547m** , **bf548m** , **bf549m** , **bf561** , **bf592**.
    
               The optional _sirevision_ specifies the silicon revision of the
               target Blackfin processor.  Any workarounds available for the
               targeted silicon revision are enabled.  If _sirevision_ is **none** ,
               no workarounds are enabled.  If _sirevision_ is **any** , all
               workarounds for the targeted processor are enabled.  The
               "__SILICON_REVISION__" macro is defined to two hexadecimal
               digits representing the major and minor numbers in the silicon
               revision.  If _sirevision_ is **none** , the "__SILICON_REVISION__"
               is not defined.  If _sirevision_ is **any** , the
               "__SILICON_REVISION__" is defined to be 0xffff.  If this
               optional _sirevision_ is not used, GCC assumes the latest known
               silicon revision of the targeted Blackfin processor.
    
               GCC defines a preprocessor macro for the specified _cpu_.  For
               the **bfin-elf** toolchain, this option causes the hardware BSP
               provided by libgloss to be linked in if **-msim** is not given.
    
               Without this option, **bf532** is used as the processor by
               default.
    
               Note that support for **bf561** is incomplete.  For **bf561** , only
               the preprocessor macro is defined.
    
           **-msim**
               Specifies that the program will be run on the simulator.  This
               causes the simulator BSP provided by libgloss to be linked in.
               This option has effect only for **bfin-elf** toolchain.  Certain
               other options, such as **-mid-shared-library** and **-mfdpic** , imply
               **-msim**.
    
           **-momit-leaf-frame-pointer**
               Don't keep the frame pointer in a register for leaf functions.
               This avoids the instructions to save, set up and restore frame
               pointers and makes an extra register available in leaf
               functions.
    
           **-mspecld-anomaly**
               When enabled, the compiler ensures that the generated code
               does not contain speculative loads after jump instructions. If
               this option is used, "__WORKAROUND_SPECULATIVE_LOADS" is
               defined.
    
           **-mno-specld-anomaly**
               Don't generate extra code to prevent speculative loads from
               occurring.
    
           **-mcsync-anomaly**
               When enabled, the compiler ensures that the generated code
               does not contain CSYNC or SSYNC instructions too soon after
               conditional branches.  If this option is used,
               "__WORKAROUND_SPECULATIVE_SYNCS" is defined.
    
           **-mno-csync-anomaly**
               Don't generate extra code to prevent CSYNC or SSYNC
               instructions from occurring too soon after a conditional
               branch.
    
           **-mlow64k**
               When enabled, the compiler is free to take advantage of the
               knowledge that the entire program fits into the low 64k of
               memory.
    
           **-mno-low64k**
               Assume that the program is arbitrarily large.  This is the
               default.
    
           **-mstack-check-l1**
               Do stack checking using information placed into L1 scratchpad
               memory by the uClinux kernel.
    
           **-mid-shared-library**
               Generate code that supports shared libraries via the library
               ID method.  This allows for execute in place and shared
               libraries in an environment without virtual memory management.
               This option implies **-fPIC**.  With a **bfin-elf** target, this
               option implies **-msim**.
    
           **-mno-id-shared-library**
               Generate code that doesn't assume ID-based shared libraries
               are being used.  This is the default.
    
           **-mleaf-id-shared-library**
               Generate code that supports shared libraries via the library
               ID method, but assumes that this library or executable won't
               link against any other ID shared libraries.  That allows the
               compiler to use faster code for jumps and calls.
    
           **-mno-leaf-id-shared-library**
               Do not assume that the code being compiled won't link against
               any ID shared libraries.  Slower code is generated for jump
               and call insns.
    
           **-mshared-library-id=n**
               Specifies the identification number of the ID-based shared
               library being compiled.  Specifying a value of 0 generates
               more compact code; specifying other values forces the
               allocation of that number to the current library but is no
               more space- or time-efficient than omitting this option.
    
           **-msep-data**
               Generate code that allows the data segment to be located in a
               different area of memory from the text segment.  This allows
               for execute in place in an environment without virtual memory
               management by eliminating relocations against the text
               section.
    
           **-mno-sep-data**
               Generate code that assumes that the data segment follows the
               text segment.  This is the default.
    
           **-mlong-calls**
           **-mno-long-calls**
               Tells the compiler to perform function calls by first loading
               the address of the function into a register and then
               performing a subroutine call on this register.  This switch is
               needed if the target function lies outside of the 24-bit
               addressing range of the offset-based version of subroutine
               call instruction.
    
               This feature is not enabled by default.  Specifying
               **-mno-long-calls** restores the default behavior.  Note these
               switches have no effect on how the compiler generates code to
               handle function calls via function pointers.
    
           **-mfast-fp**
               Link with the fast floating-point library. This library
               relaxes some of the IEEE floating-point standard's rules for
               checking inputs against Not-a-Number (NAN), in the interest of
               performance.
    
           **-minline-plt**
               Enable inlining of PLT entries in function calls to functions
               that are not known to bind locally.  It has no effect without
               **-mfdpic**.
    
           **-mmulticore**
               Build a standalone application for multicore Blackfin
               processors.  This option causes proper start files and link
               scripts supporting multicore to be used, and defines the macro
               "__BFIN_MULTICORE".  It can only be used with
               **-mcpu=bf561**[**-**_sirevision_].
    
               This option can be used with **-mcorea** or **-mcoreb** , which selects
               the one-application-per-core programming model.  Without
               **-mcorea** or **-mcoreb** , the single-application/dual-core
               programming model is used. In this model, the main function of
               Core B should be named as "coreb_main".
    
               If this option is not used, the single-core application
               programming model is used.
    
           **-mcorea**
               Build a standalone application for Core A of BF561 when using
               the one-application-per-core programming model. Proper start
               files and link scripts are used to support Core A, and the
               macro "__BFIN_COREA" is defined.  This option can only be used
               in conjunction with **-mmulticore**.
    
           **-mcoreb**
               Build a standalone application for Core B of BF561 when using
               the one-application-per-core programming model. Proper start
               files and link scripts are used to support Core B, and the
               macro "__BFIN_COREB" is defined. When this option is used,
               "coreb_main" should be used instead of "main".  This option
               can only be used in conjunction with **-mmulticore**.
    
           **-msdram**
               Build a standalone application for SDRAM. Proper start files
               and link scripts are used to put the application into SDRAM,
               and the macro "__BFIN_SDRAM" is defined.  The loader should
               initialize SDRAM before loading the application.
    
           **-micplb**
               Assume that ICPLBs are enabled at run time.  This has an
               effect on certain anomaly workarounds.  For Linux targets, the
               default is to assume ICPLBs are enabled; for standalone
               applications the default is off.
    
           _C6X Options_
    
           **-march=**_name_
               This specifies the name of the target architecture.  GCC uses
               this name to determine what kind of instructions it can emit
               when generating assembly code.  Permissible names are: **c62x** ,
               **c64x** , **c64x+** , **c67x** , **c67x+** , **c674x**.
    
           **-mbig-endian**
               Generate code for a big-endian target.
    
           **-mlittle-endian**
               Generate code for a little-endian target.  This is the
               default.
    
           **-msim**
               Choose startup files and linker script suitable for the
               simulator.
    
           **-msdata=default**
               Put small global and static data in the ".neardata" section,
               which is pointed to by register "B14".  Put small
               uninitialized global and static data in the ".bss" section,
               which is adjacent to the ".neardata" section.  Put small read-
               only data into the ".rodata" section.  The corresponding
               sections used for large pieces of data are ".fardata", ".far"
               and ".const".
    
           **-msdata=all**
               Put all data, not just small objects, into the sections
               reserved for small data, and use addressing relative to the
               "B14" register to access them.
    
           **-msdata=none**
               Make no use of the sections reserved for small data, and use
               absolute addresses to access all data.  Put all initialized
               global and static data in the ".fardata" section, and all
               uninitialized data in the ".far" section.  Put all constant
               data into the ".const" section.
    
           _CRIS Options_
    
           These options are defined specifically for the CRIS ports.
    
           **-march=**_architecture-type_
           **-mcpu=**_architecture-type_
               Generate code for the specified architecture.  The choices for
               _architecture-type_ are **v3** , **v8** and **v10** for respectively ETRAX 4,
               ETRAX 100, and ETRAX 100 LX.  Default is **v0** except for cris-
               axis-linux-gnu, where the default is **v10**.
    
           **-mtune=**_architecture-type_
               Tune to _architecture-type_ everything applicable about the
               generated code, except for the ABI and the set of available
               instructions.  The choices for _architecture-type_ are the same
               as for **-march=**_architecture-type_.
    
           **-mmax-stack-frame=**_n_
               Warn when the stack frame of a function exceeds _n_ bytes.
    
           **-metrax4**
           **-metrax100**
               The options **-metrax4** and **-metrax100** are synonyms for **-march=v3**
               and **-march=v8** respectively.
    
           **-mmul-bug-workaround**
           **-mno-mul-bug-workaround**
               Work around a bug in the "muls" and "mulu" instructions for
               CPU models where it applies.  This option is active by
               default.
    
           **-mpdebug**
               Enable CRIS-specific verbose debug-related information in the
               assembly code.  This option also has the effect of turning off
               the **#NO_APP** formatted-code indicator to the assembler at the
               beginning of the assembly file.
    
           **-mcc-init**
               Do not use condition-code results from previous instruction;
               always emit compare and test instructions before use of
               condition codes.
    
           **-mno-side-effects**
               Do not emit instructions with side effects in addressing modes
               other than post-increment.
    
           **-mstack-align**
           **-mno-stack-align**
           **-mdata-align**
           **-mno-data-align**
           **-mconst-align**
           **-mno-const-align**
               These options (**no-** options) arrange (eliminate arrangements)
               for the stack frame, individual data and constants to be
               aligned for the maximum single data access size for the chosen
               CPU model.  The default is to arrange for 32-bit alignment.
               ABI details such as structure layout are not affected by these
               options.
    
           **-m32-bit**
           **-m16-bit**
           **-m8-bit**
               Similar to the stack- data- and const-align options above,
               these options arrange for stack frame, writable data and
               constants to all be 32-bit, 16-bit or 8-bit aligned.  The
               default is 32-bit alignment.
    
           **-mno-prologue-epilogue**
           **-mprologue-epilogue**
               With **-mno-prologue-epilogue** , the normal function prologue and
               epilogue which set up the stack frame are omitted and no
               return instructions or return sequences are generated in the
               code.  Use this option only together with visual inspection of
               the compiled code: no warnings or errors are generated when
               call-saved registers must be saved, or storage for local
               variables needs to be allocated.
    
           **-mno-gotplt**
           **-mgotplt**
               With **-fpic** and **-fPIC** , don't generate (do generate) instruction
               sequences that load addresses for functions from the PLT part
               of the GOT rather than (traditional on other architectures)
               calls to the PLT.  The default is **-mgotplt**.
    
           **-melf**
               Legacy no-op option only recognized with the cris-axis-elf and
               cris-axis-linux-gnu targets.
    
           **-mlinux**
               Legacy no-op option only recognized with the cris-axis-linux-
               gnu target.
    
           **-sim**
               This option, recognized for the cris-axis-elf, arranges to
               link with input-output functions from a simulator library.
               Code, initialized data and zero-initialized data are allocated
               consecutively.
    
           **-sim2**
               Like **-sim** , but pass linker options to locate initialized data
               at 0x40000000 and zero-initialized data at 0x80000000.
    
           _CR16 Options_
    
           These options are defined specifically for the CR16 ports.
    
           **-mmac**
               Enable the use of multiply-accumulate instructions. Disabled
               by default.
    
           **-mcr16cplus**
           **-mcr16c**
               Generate code for CR16C or CR16C+ architecture. CR16C+
               architecture is default.
    
           **-msim**
               Links the library libsim.a which is in compatible with
               simulator. Applicable to ELF compiler only.
    
           **-mint32**
               Choose integer type as 32-bit wide.
    
           **-mbit-ops**
               Generates "sbit"/"cbit" instructions for bit manipulations.
    
           **-mdata-model=**_model_
               Choose a data model. The choices for _model_ are **near** , **far** or
               **medium**. **medium** is default.  However, **far** is not valid with
               **-mcr16c** , as the CR16C architecture does not support the far
               data model.
    
           _C-SKY Options_
    
           GCC supports these options when compiling for C-SKY V2 processors.
    
           **-march=**_arch_
               Specify the C-SKY target architecture.  Valid values for _arch_
               are: **ck801** , **ck802** , **ck803** , **ck807** , and **ck810**.  The default is
               **ck810**.
    
           **-mcpu=**_cpu_
               Specify the C-SKY target processor.  Valid values for _cpu_ are:
               **ck801** , **ck801t** , **ck802** , **ck802t** , **ck802j** , **ck803** , **ck803h** , **ck803t** ,
               **ck803ht** , **ck803f** , **ck803fh** , **ck803e** , **ck803eh** , **ck803et** , **ck803eht** ,
               **ck803ef** , **ck803efh** , **ck803ft** , **ck803eft** , **ck803efht** , **ck803r1** ,
               **ck803hr1** , **ck803tr1** , **ck803htr1** , **ck803fr1** , **ck803fhr1** , **ck803er1** ,
               **ck803ehr1** , **ck803etr1** , **ck803ehtr1** , **ck803efr1** , **ck803efhr1** ,
               **ck803ftr1** , **ck803eftr1** , **ck803efhtr1** , **ck803s** , **ck803st** , **ck803se** ,
               **ck803sf** , **ck803sef** , **ck803seft** , **ck807e** , **ck807ef** , **ck807** , **ck807f** ,
               **ck810e** , **ck810et** , **ck810ef** , **ck810eft** , **ck810** , **ck810v** , **ck810f** ,
               **ck810t** , **ck810fv** , **ck810tv** , **ck810ft** , and **ck810ftv**.
    
           **-mbig-endian**
           **-EB**
           **-mlittle-endian**
           **-EL** Select big- or little-endian code.  The default is little-
               endian.
    
           **-mhard-float**
           **-msoft-float**
               Select hardware or software floating-point implementations.
               The default is soft float.
    
           **-mdouble-float**
           **-mno-double-float**
               When **-mhard-float** is in effect, enable generation of double-
               precision float instructions.  This is the default except when
               compiling for CK803.
    
           **-mfdivdu**
           **-mno-fdivdu**
               When **-mhard-float** is in effect, enable generation of
               "frecipd", "fsqrtd", and "fdivd" instructions.  This is the
               default except when compiling for CK803.
    
           **-mfpu=**_fpu_
               Select the floating-point processor.  This option can only be
               used with **-mhard-float**.  Values for _fpu_ are **fpv2_sf**
               (equivalent to **-mno-double-float -mno-fdivdu**), **fpv2**
               (**-mdouble-float -mno-divdu**), and **fpv2_divd**(**-mdouble-float**
               **-mdivdu**).
    
           **-melrw**
           **-mno-elrw**
               Enable the extended "lrw" instruction.  This option defaults
               to on for CK801 and off otherwise.
    
           **-mistack**
           **-mno-istack**
               Enable interrupt stack instructions; the default is off.
    
               The **-mistack** option is required to handle the "interrupt" and
               "isr" function attributes.
    
           **-mmp**
               Enable multiprocessor instructions; the default is off.
    
           **-mcp**
               Enable coprocessor instructions; the default is off.
    
           **-mcache**
               Enable coprocessor instructions; the default is off.
    
           **-msecurity**
               Enable C-SKY security instructions; the default is off.
    
           **-mtrust**
               Enable C-SKY trust instructions; the default is off.
    
           **-mdsp**
           **-medsp**
           **-mvdsp**
               Enable C-SKY DSP, Enhanced DSP, or Vector DSP instructions,
               respectively.  All of these options default to off.
    
           **-mdiv**
           **-mno-div**
               Generate divide instructions.  Default is off.
    
           **-msmart**
           **-mno-smart**
               Generate code for Smart Mode, using only registers numbered
               0-7 to allow use of 16-bit instructions.  This option is
               ignored for CK801 where this is the required behavior, and it
               defaults to on for CK802.  For other targets, the default is
               off.
    
           **-mhigh-registers**
           **-mno-high-registers**
               Generate code using the high registers numbered 16-31.  This
               option is not supported on CK801, CK802, or CK803, and is
               enabled by default for other processors.
    
           **-manchor**
           **-mno-anchor**
               Generate code using global anchor symbol addresses.
    
           **-mpushpop**
           **-mno-pushpop**
               Generate code using "push" and "pop" instructions.  This
               option defaults to on.
    
           **-mmultiple-stld**
           **-mstm**
           **-mno-multiple-stld**
           **-mno-stm**
               Generate code using "stm" and "ldm" instructions.  This option
               isn't supported on CK801 but is enabled by default on other
               processors.
    
           **-mconstpool**
           **-mno-constpool**
               Create constant pools in the compiler instead of deferring it
               to the assembler.  This option is the default and required for
               correct code generation on CK801 and CK802, and is optional on
               other processors.
    
           **-mstack-size**
           **-mno-stack-size**
               Emit ".stack_size" directives for each function in the
               assembly output.  This option defaults to off.
    
           **-mccrt**
           **-mno-ccrt**
               Generate code for the C-SKY compiler runtime instead of
               libgcc.  This option defaults to off.
    
           **-mbranch-cost=**_n_
               Set the branch costs to roughly "n" instructions.  The default
               is 1.
    
           **-msched-prolog**
           **-mno-sched-prolog**
               Permit scheduling of function prologue and epilogue sequences.
               Using this option can result in code that is not compliant
               with the C-SKY V2 ABI prologue requirements and that cannot be
               debugged or backtraced.  It is disabled by default.
    
           _Darwin Options_
    
           These options are defined for all architectures running the Darwin
           operating system.
    
           FSF GCC on Darwin does not create "fat" object files; it creates
           an object file for the single architecture that GCC was built to
           target.  Apple's GCC on Darwin does create "fat" files if multiple
           **-arch** options are used; it does so by running the compiler or
           linker multiple times and joining the results together with _lipo_.
    
           The subtype of the file created (like **ppc7400** or **ppc970** or **i686**)
           is determined by the flags that specify the ISA that GCC is
           targeting, like **-mcpu** or **-march**.  The **-force_cpusubtype_ALL** option
           can be used to override this.
    
           The Darwin tools vary in their behavior when presented with an ISA
           mismatch.  The assembler, _as_ , only permits instructions to be used
           that are valid for the subtype of the file it is generating, so
           you cannot put 64-bit instructions in a **ppc750** object file.  The
           linker for shared libraries, _/usr/bin/libtool_ , fails and prints an
           error if asked to create a shared library with a less restrictive
           subtype than its input files (for instance, trying to put a **ppc970**
           object file in a **ppc7400** library).  The linker for executables,
           **ld** , quietly gives the executable the most restrictive subtype of
           any of its input files.
    
           **-F** _dir_
               Add the framework directory _dir_ to the head of the list of
               directories to be searched for header files.  These
               directories are interleaved with those specified by **-I** options
               and are scanned in a left-to-right order.
    
               A framework directory is a directory with frameworks in it.  A
               framework is a directory with a _Headers_ and/or _PrivateHeaders_
               directory contained directly in it that ends in _.framework_.
               The name of a framework is the name of this directory
               excluding the _.framework_.  Headers associated with the
               framework are found in one of those two directories, with
               _Headers_ being searched first.  A subframework is a framework
               directory that is in a framework's _Frameworks_ directory.
               Includes of subframework headers can only appear in a header
               of a framework that contains the subframework, or in a sibling
               subframework header.  Two subframeworks are siblings if they
               occur in the same framework.  A subframework should not have
               the same name as a framework; a warning is issued if this is
               violated.  Currently a subframework cannot have subframeworks;
               in the future, the mechanism may be extended to support this.
               The standard frameworks can be found in
               _/System/Library/Frameworks_ and _/Library/Frameworks_.  An
               example include looks like "#include <Framework/header.h>",
               where _Framework_ denotes the name of the framework and _header.h_
               is found in the _PrivateHeaders_ or _Headers_ directory.
    
           **-iframework** _dir_
               Like **-F** except the directory is a treated as a system
               directory.  The main difference between this **-iframework** and
               **-F** is that with **-iframework** the compiler does not warn about
               constructs contained within header files found via _dir_.  This
               option is valid only for the C family of languages.
    
           **-gused**
               Emit debugging information for symbols that are used.  For
               stabs debugging format, this enables
               **-feliminate-unused-debug-symbols**.  This is by default ON.
    
           **-gfull**
               Emit debugging information for all symbols and types.
    
           **-mmacosx-version-min=**_version_
               The earliest version of MacOS X that this executable will run
               on is _version_.  Typical values of _version_ include 10.1, 10.2,
               and 10.3.9.
    
               If the compiler was built to use the system's headers by
               default, then the default for this option is the system
               version on which the compiler is running, otherwise the
               default is to make choices that are compatible with as many
               systems and code bases as possible.
    
           **-mkernel**
               Enable kernel development mode.  The **-mkernel** option sets
               **-static** , **-fno-common** , **-fno-use-cxa-atexit** , **-fno-exceptions** ,
               **-fno-non-call-exceptions** , **-fapple-kext** , **-fno-weak** and
               **-fno-rtti** where applicable.  This mode also sets **-mno-altivec** ,
               **-msoft-float** , **-fno-builtin** and **-mlong-branch** for PowerPC
               targets.
    
           **-mone-byte-bool**
               Override the defaults for "bool" so that "sizeof(bool)==1".
               By default "sizeof(bool)" is 4 when compiling for
               Darwin/PowerPC and 1 when compiling for Darwin/x86, so this
               option has no effect on x86.
    
               **Warning:** The **-mone-byte-bool** switch causes GCC to generate
               code that is not binary compatible with code generated without
               that switch.  Using this switch may require recompiling all
               other modules in a program, including system libraries.  Use
               this switch to conform to a non-default data model.
    
           **-mfix-and-continue**
           **-ffix-and-continue**
           **-findirect-data**
               Generate code suitable for fast turnaround development, such
               as to allow GDB to dynamically load _.o_ files into already-
               running programs.  **-findirect-data** and **-ffix-and-continue** are
               provided for backwards compatibility.
    
           **-all_load**
               Loads all members of static archive libraries.  See man _ld_(1)
               for more information.
    
           **-arch_errors_fatal**
               Cause the errors having to do with files that have the wrong
               architecture to be fatal.
    
           **-bind_at_load**
               Causes the output file to be marked such that the dynamic
               linker will bind all undefined references when the file is
               loaded or launched.
    
           **-bundle**
               Produce a Mach-o bundle format file.  See man _ld_(1) for more
               information.
    
           **-bundle_loader** _executable_
               This option specifies the _executable_ that will load the build
               output file being linked.  See man _ld_(1) for more information.
    
           **-dynamiclib**
               When passed this option, GCC produces a dynamic library
               instead of an executable when linking, using the Darwin
               _libtool_ command.
    
           **-force_cpusubtype_ALL**
               This causes GCC's output file to have the **ALL** subtype, instead
               of one controlled by the **-mcpu** or **-march** option.
    
           **-allowable_client** _client_name_
           **-client_name**
           **-compatibility_version**
           **-current_version**
           **-dead_strip**
           **-dependency-file**
           **-dylib_file**
           **-dylinker_install_name**
           **-dynamic**
           **-exported_symbols_list**
           **-filelist**
           **-flat_namespace**
           **-force_flat_namespace**
           **-headerpad_max_install_names**
           **-image_base**
           **-init**
           **-install_name**
           **-keep_private_externs**
           **-multi_module**
           **-multiply_defined**
           **-multiply_defined_unused**
           **-noall_load**
           **-no_dead_strip_inits_and_terms**
           **-nofixprebinding**
           **-nomultidefs**
           **-noprebind**
           **-noseglinkedit**
           **-pagezero_size**
           **-prebind**
           **-prebind_all_twolevel_modules**
           **-private_bundle**
           **-read_only_relocs**
           **-sectalign**
           **-sectobjectsymbols**
           **-whyload**
           **-seg1addr**
           **-sectcreate**
           **-sectobjectsymbols**
           **-sectorder**
           **-segaddr**
           **-segs_read_only_addr**
           **-segs_read_write_addr**
           **-seg_addr_table**
           **-seg_addr_table_filename**
           **-seglinkedit**
           **-segprot**
           **-segs_read_only_addr**
           **-segs_read_write_addr**
           **-single_module**
           **-static**
           **-sub_library**
           **-sub_umbrella**
           **-twolevel_namespace**
           **-umbrella**
           **-undefined**
           **-unexported_symbols_list**
           **-weak_reference_mismatches**
           **-whatsloaded**
               These options are passed to the Darwin linker.  The Darwin
               linker man page describes them in detail.
    
           _DEC Alpha Options_
    
           These **-m** options are defined for the DEC Alpha implementations:
    
           **-mno-soft-float**
           **-msoft-float**
               Use (do not use) the hardware floating-point instructions for
               floating-point operations.  When **-msoft-float** is specified,
               functions in _libgcc.a_ are used to perform floating-point
               operations.  Unless they are replaced by routines that emulate
               the floating-point operations, or compiled in such a way as to
               call such emulations routines, these routines issue floating-
               point operations.   If you are compiling for an Alpha without
               floating-point operations, you must ensure that the library is
               built so as not to call them.
    
               Note that Alpha implementations without floating-point
               operations are required to have floating-point registers.
    
           **-mfp-reg**
           **-mno-fp-regs**
               Generate code that uses (does not use) the floating-point
               register set.  **-mno-fp-regs** implies **-msoft-float**.  If the
               floating-point register set is not used, floating-point
               operands are passed in integer registers as if they were
               integers and floating-point results are passed in $0 instead
               of $f0.  This is a non-standard calling sequence, so any
               function with a floating-point argument or return value called
               by code compiled with **-mno-fp-regs** must also be compiled with
               that option.
    
               A typical use of this option is building a kernel that does
               not use, and hence need not save and restore, any floating-
               point registers.
    
           **-mieee**
               The Alpha architecture implements floating-point hardware
               optimized for maximum performance.  It is mostly compliant
               with the IEEE floating-point standard.  However, for full
               compliance, software assistance is required.  This option
               generates code fully IEEE-compliant code _except_ that the
               _inexact-flag_ is not maintained (see below).  If this option is
               turned on, the preprocessor macro "_IEEE_FP" is defined during
               compilation.  The resulting code is less efficient but is able
               to correctly support denormalized numbers and exceptional IEEE
               values such as not-a-number and plus/minus infinity.  Other
               Alpha compilers call this option **-ieee_with_no_inexact**.
    
           **-mieee-with-inexact**
               This is like **-mieee** except the generated code also maintains
               the IEEE _inexact-flag_.  Turning on this option causes the
               generated code to implement fully-compliant IEEE math.  In
               addition to "_IEEE_FP", "_IEEE_FP_EXACT" is defined as a
               preprocessor macro.  On some Alpha implementations the
               resulting code may execute significantly slower than the code
               generated by default.  Since there is very little code that
               depends on the _inexact-flag_ , you should normally not specify
               this option.  Other Alpha compilers call this option
               **-ieee_with_inexact**.
    
           **-mfp-trap-mode=**_trap-mode_
               This option controls what floating-point related traps are
               enabled.  Other Alpha compilers call this option **-fptm** _trap-_
               _mode_.  The trap mode can be set to one of four values:
    
               **n** This is the default (normal) setting.  The only traps that
                   are enabled are the ones that cannot be disabled in
                   software (e.g., division by zero trap).
    
               **u** In addition to the traps enabled by **n** , underflow traps are
                   enabled as well.
    
               **su** Like **u** , but the instructions are marked to be safe for
                   software completion (see Alpha architecture manual for
                   details).
    
               **sui** Like **su** , but inexact traps are enabled as well.
    
           **-mfp-rounding-mode=**_rounding-mode_
               Selects the IEEE rounding mode.  Other Alpha compilers call
               this option **-fprm** _rounding-mode_.  The _rounding-mode_ can be one
               of:
    
               **n** Normal IEEE rounding mode.  Floating-point numbers are
                   rounded towards the nearest machine number or towards the
                   even machine number in case of a tie.
    
               **m** Round towards minus infinity.
    
               **c** Chopped rounding mode.  Floating-point numbers are rounded
                   towards zero.
    
               **d** Dynamic rounding mode.  A field in the floating-point
                   control register (_fpcr_ , see Alpha architecture reference
                   manual) controls the rounding mode in effect.  The C
                   library initializes this register for rounding towards
                   plus infinity.  Thus, unless your program modifies the
                   _fpcr_ , **d** corresponds to round towards plus infinity.
    
           **-mtrap-precision=**_trap-precision_
               In the Alpha architecture, floating-point traps are imprecise.
               This means without software assistance it is impossible to
               recover from a floating trap and program execution normally
               needs to be terminated.  GCC can generate code that can assist
               operating system trap handlers in determining the exact
               location that caused a floating-point trap.  Depending on the
               requirements of an application, different levels of precisions
               can be selected:
    
               **p** Program precision.  This option is the default and means a
                   trap handler can only identify which program caused a
                   floating-point exception.
    
               **f** Function precision.  The trap handler can determine the
                   function that caused a floating-point exception.
    
               **i** Instruction precision.  The trap handler can determine the
                   exact instruction that caused a floating-point exception.
    
               Other Alpha compilers provide the equivalent options called
               **-scope_safe** and **-resumption_safe**.
    
           **-mieee-conformant**
               This option marks the generated code as IEEE conformant.  You
               must not use this option unless you also specify
               **-mtrap-precision=i** and either **-mfp-trap-mode=su** or
               **-mfp-trap-mode=sui**.  Its only effect is to emit the line
               **.eflag 48** in the function prologue of the generated assembly
               file.
    
           **-mbuild-constants**
               Normally GCC examines a 32- or 64-bit integer constant to see
               if it can construct it from smaller constants in two or three
               instructions.  If it cannot, it outputs the constant as a
               literal and generates code to load it from the data segment at
               run time.
    
               Use this option to require GCC to construct _all_ integer
               constants using code, even if it takes more instructions (the
               maximum is six).
    
               You typically use this option to build a shared library
               dynamic loader.  Itself a shared library, it must relocate
               itself in memory before it can find the variables and
               constants in its own data segment.
    
           **-mbwx**
           **-mno-bwx**
           **-mcix**
           **-mno-cix**
           **-mfix**
           **-mno-fix**
           **-mmax**
           **-mno-max**
               Indicate whether GCC should generate code to use the optional
               BWX, CIX, FIX and MAX instruction sets.  The default is to use
               the instruction sets supported by the CPU type specified via
               **-mcpu=** option or that of the CPU on which GCC was built if
               none is specified.
    
           **-mfloat-vax**
           **-mfloat-ieee**
               Generate code that uses (does not use) VAX F and G floating-
               point arithmetic instead of IEEE single and double precision.
    
           **-mexplicit-relocs**
           **-mno-explicit-relocs**
               Older Alpha assemblers provided no way to generate symbol
               relocations except via assembler macros.  Use of these macros
               does not allow optimal instruction scheduling.  GNU binutils
               as of version 2.12 supports a new syntax that allows the
               compiler to explicitly mark which relocations should apply to
               which instructions.  This option is mostly useful for
               debugging, as GCC detects the capabilities of the assembler
               when it is built and sets the default accordingly.
    
           **-msmall-data**
           **-mlarge-data**
               When **-mexplicit-relocs** is in effect, static data is accessed
               via _gp-relative_ relocations.  When **-msmall-data** is used,
               objects 8 bytes long or smaller are placed in a _small data_
               _area_ (the ".sdata" and ".sbss" sections) and are accessed via
               16-bit relocations off of the $gp register.  This limits the
               size of the small data area to 64KB, but allows the variables
               to be directly accessed via a single instruction.
    
               The default is **-mlarge-data**.  With this option the data area
               is limited to just below 2GB.  Programs that require more than
               2GB of data must use "malloc" or "mmap" to allocate the data
               in the heap instead of in the program's data segment.
    
               When generating code for shared libraries, **-fpic** implies
               **-msmall-data** and **-fPIC** implies **-mlarge-data**.
    
           **-msmall-text**
           **-mlarge-text**
               When **-msmall-text** is used, the compiler assumes that the code
               of the entire program (or shared library) fits in 4MB, and is
               thus reachable with a branch instruction.  When **-msmall-data**
               is used, the compiler can assume that all local symbols share
               the same $gp value, and thus reduce the number of instructions
               required for a function call from 4 to 1.
    
               The default is **-mlarge-text**.
    
           **-mcpu=**_cpu_type_
               Set the instruction set and instruction scheduling parameters
               for machine type _cpu_type_.  You can specify either the **EV**
               style name or the corresponding chip number.  GCC supports
               scheduling parameters for the EV4, EV5 and EV6 family of
               processors and chooses the default values for the instruction
               set from the processor you specify.  If you do not specify a
               processor type, GCC defaults to the processor on which the
               compiler was built.
    
               Supported values for _cpu_type_ are
    
               **ev4**
               **ev45**
               **21064**
                   Schedules as an EV4 and has no instruction set extensions.
    
               **ev5**
               **21164**
                   Schedules as an EV5 and has no instruction set extensions.
    
               **ev56**
               **21164a**
                   Schedules as an EV5 and supports the BWX extension.
    
               **pca56**
               **21164pc**
               **21164PC**
                   Schedules as an EV5 and supports the BWX and MAX
                   extensions.
    
               **ev6**
               **21264**
                   Schedules as an EV6 and supports the BWX, FIX, and MAX
                   extensions.
    
               **ev67**
               **21264a**
                   Schedules as an EV6 and supports the BWX, CIX, FIX, and
                   MAX extensions.
    
               Native toolchains also support the value **native** , which selects
               the best architecture option for the host processor.
               **-mcpu=native** has no effect if GCC does not recognize the
               processor.
    
           **-mtune=**_cpu_type_
               Set only the instruction scheduling parameters for machine
               type _cpu_type_.  The instruction set is not changed.
    
               Native toolchains also support the value **native** , which selects
               the best architecture option for the host processor.
               **-mtune=native** has no effect if GCC does not recognize the
               processor.
    
           **-mmemory-latency=**_time_
               Sets the latency the scheduler should assume for typical
               memory references as seen by the application.  This number is
               highly dependent on the memory access patterns used by the
               application and the size of the external cache on the machine.
    
               Valid options for _time_ are
    
               _number_
                   A decimal number representing clock cycles.
    
               **L1**
               **L2**
               **L3**
               **main**
                   The compiler contains estimates of the number of clock
                   cycles for "typical" EV4 & EV5 hardware for the Level 1, 2
                   & 3 caches (also called Dcache, Scache, and Bcache), as
                   well as to main memory.  Note that L3 is only valid for
                   EV5.
    
           _FR30 Options_
    
           These options are defined specifically for the FR30 port.
    
           **-msmall-model**
               Use the small address space model.  This can produce smaller
               code, but it does assume that all symbolic values and
               addresses fit into a 20-bit range.
    
           **-mno-lsim**
               Assume that runtime support has been provided and so there is
               no need to include the simulator library (_libsim.a_) on the
               linker command line.
    
           _FT32 Options_
    
           These options are defined specifically for the FT32 port.
    
           **-msim**
               Specifies that the program will be run on the simulator.  This
               causes an alternate runtime startup and library to be linked.
               You must not use this option when generating programs that
               will run on real hardware; you must provide your own runtime
               library for whatever I/O functions are needed.
    
           **-mlra**
               Enable Local Register Allocation.  This is still experimental
               for FT32, so by default the compiler uses standard reload.
    
           **-mnodiv**
               Do not use div and mod instructions.
    
           **-mft32b**
               Enable use of the extended instructions of the FT32B
               processor.
    
           **-mcompress**
               Compress all code using the Ft32B code compression scheme.
    
           **-mnopm**
               Do not generate code that reads program memory.
    
           _FRV Options_
    
           **-mgpr-32**
               Only use the first 32 general-purpose registers.
    
           **-mgpr-64**
               Use all 64 general-purpose registers.
    
           **-mfpr-32**
               Use only the first 32 floating-point registers.
    
           **-mfpr-64**
               Use all 64 floating-point registers.
    
           **-mhard-float**
               Use hardware instructions for floating-point operations.
    
           **-msoft-float**
               Use library routines for floating-point operations.
    
           **-malloc-cc**
               Dynamically allocate condition code registers.
    
           **-mfixed-cc**
               Do not try to dynamically allocate condition code registers,
               only use "icc0" and "fcc0".
    
           **-mdword**
               Change ABI to use double word insns.
    
           **-mno-dword**
               Do not use double word instructions.
    
           **-mdouble**
               Use floating-point double instructions.
    
           **-mno-double**
               Do not use floating-point double instructions.
    
           **-mmedia**
               Use media instructions.
    
           **-mno-media**
               Do not use media instructions.
    
           **-mmuladd**
               Use multiply and add/subtract instructions.
    
           **-mno-muladd**
               Do not use multiply and add/subtract instructions.
    
           **-mfdpic**
               Select the FDPIC ABI, which uses function descriptors to
               represent pointers to functions.  Without any PIC/PIE-related
               options, it implies **-fPIE**.  With **-fpic** or **-fpie** , it assumes
               GOT entries and small data are within a 12-bit range from the
               GOT base address; with **-fPIC** or **-fPIE** , GOT offsets are
               computed with 32 bits.  With a **bfin-elf** target, this option
               implies **-msim**.
    
           **-minline-plt**
               Enable inlining of PLT entries in function calls to functions
               that are not known to bind locally.  It has no effect without
               **-mfdpic**.  It's enabled by default if optimizing for speed and
               compiling for shared libraries (i.e., **-fPIC** or **-fpic**), or when
               an optimization option such as **-O3** or above is present in the
               command line.
    
           **-mTLS**
               Assume a large TLS segment when generating thread-local code.
    
           **-mtls**
               Do not assume a large TLS segment when generating thread-local
               code.
    
           **-mgprel-ro**
               Enable the use of "GPREL" relocations in the FDPIC ABI for
               data that is known to be in read-only sections.  It's enabled
               by default, except for **-fpic** or **-fpie** : even though it may help
               make the global offset table smaller, it trades 1 instruction
               for 4.  With **-fPIC** or **-fPIE** , it trades 3 instructions for 4,
               one of which may be shared by multiple symbols, and it avoids
               the need for a GOT entry for the referenced symbol, so it's
               more likely to be a win.  If it is not, **-mno-gprel-ro** can be
               used to disable it.
    
           **-multilib-library-pic**
               Link with the (library, not FD) pic libraries.  It's implied
               by **-mlibrary-pic** , as well as by **-fPIC** and **-fpic** without
               **-mfdpic**.  You should never have to use it explicitly.
    
           **-mlinked-fp**
               Follow the EABI requirement of always creating a frame pointer
               whenever a stack frame is allocated.  This option is enabled
               by default and can be disabled with **-mno-linked-fp**.
    
           **-mlong-calls**
               Use indirect addressing to call functions outside the current
               compilation unit.  This allows the functions to be placed
               anywhere within the 32-bit address space.
    
           **-malign-labels**
               Try to align labels to an 8-byte boundary by inserting NOPs
               into the previous packet.  This option only has an effect when
               VLIW packing is enabled.  It doesn't create new packets; it
               merely adds NOPs to existing ones.
    
           **-mlibrary-pic**
               Generate position-independent EABI code.
    
           **-macc-4**
               Use only the first four media accumulator registers.
    
           **-macc-8**
               Use all eight media accumulator registers.
    
           **-mpack**
               Pack VLIW instructions.
    
           **-mno-pack**
               Do not pack VLIW instructions.
    
           **-mno-eflags**
               Do not mark ABI switches in e_flags.
    
           **-mcond-move**
               Enable the use of conditional-move instructions (default).
    
               This switch is mainly for debugging the compiler and will
               likely be removed in a future version.
    
           **-mno-cond-move**
               Disable the use of conditional-move instructions.
    
               This switch is mainly for debugging the compiler and will
               likely be removed in a future version.
    
           **-mscc**
               Enable the use of conditional set instructions (default).
    
               This switch is mainly for debugging the compiler and will
               likely be removed in a future version.
    
           **-mno-scc**
               Disable the use of conditional set instructions.
    
               This switch is mainly for debugging the compiler and will
               likely be removed in a future version.
    
           **-mcond-exec**
               Enable the use of conditional execution (default).
    
               This switch is mainly for debugging the compiler and will
               likely be removed in a future version.
    
           **-mno-cond-exec**
               Disable the use of conditional execution.
    
               This switch is mainly for debugging the compiler and will
               likely be removed in a future version.
    
           **-mvliw-branch**
               Run a pass to pack branches into VLIW instructions (default).
    
               This switch is mainly for debugging the compiler and will
               likely be removed in a future version.
    
           **-mno-vliw-branch**
               Do not run a pass to pack branches into VLIW instructions.
    
               This switch is mainly for debugging the compiler and will
               likely be removed in a future version.
    
           **-mmulti-cond-exec**
               Enable optimization of "&&" and "||" in conditional execution
               (default).
    
               This switch is mainly for debugging the compiler and will
               likely be removed in a future version.
    
           **-mno-multi-cond-exec**
               Disable optimization of "&&" and "||" in conditional
               execution.
    
               This switch is mainly for debugging the compiler and will
               likely be removed in a future version.
    
           **-mnested-cond-exec**
               Enable nested conditional execution optimizations (default).
    
               This switch is mainly for debugging the compiler and will
               likely be removed in a future version.
    
           **-mno-nested-cond-exec**
               Disable nested conditional execution optimizations.
    
               This switch is mainly for debugging the compiler and will
               likely be removed in a future version.
    
           **-moptimize-membar**
               This switch removes redundant "membar" instructions from the
               compiler-generated code.  It is enabled by default.
    
           **-mno-optimize-membar**
               This switch disables the automatic removal of redundant
               "membar" instructions from the generated code.
    
           **-mtomcat-stats**
               Cause gas to print out tomcat statistics.
    
           **-mcpu=**_cpu_
               Select the processor type for which to generate code.
               Possible values are **frv** , **fr550** , **tomcat** , **fr500** , **fr450** , **fr405** ,
               **fr400** , **fr300** and **simple**.
    
           _GNU/Linux Options_
    
           These **-m** options are defined for GNU/Linux targets:
    
           **-mglibc**
               Use the GNU C library.  This is the default except on
               ***-*-linux-*uclibc*** , ***-*-linux-*musl*** and ***-*-linux-*android***
               targets.
    
           **-muclibc**
               Use uClibc C library.  This is the default on
               ***-*-linux-*uclibc*** targets.
    
           **-mmusl**
               Use the musl C library.  This is the default on
               ***-*-linux-*musl*** targets.
    
           **-mbionic**
               Use Bionic C library.  This is the default on
               ***-*-linux-*android*** targets.
    
           **-mandroid**
               Compile code compatible with Android platform.  This is the
               default on ***-*-linux-*android*** targets.
    
               When compiling, this option enables **-mbionic** , **-fPIC** ,
               **-fno-exceptions** and **-fno-rtti** by default.  When linking, this
               option makes the GCC driver pass Android-specific options to
               the linker.  Finally, this option causes the preprocessor
               macro "__ANDROID__" to be defined.
    
           **-tno-android-cc**
               Disable compilation effects of **-mandroid** , i.e., do not enable
               **-mbionic** , **-fPIC** , **-fno-exceptions** and **-fno-rtti** by default.
    
           **-tno-android-ld**
               Disable linking effects of **-mandroid** , i.e., pass standard
               Linux linking options to the linker.
    
           _H8/300 Options_
    
           These **-m** options are defined for the H8/300 implementations:
    
           **-mrelax**
               Shorten some address references at link time, when possible;
               uses the linker option **-relax**.
    
           **-mh** Generate code for the H8/300H.
    
           **-ms** Generate code for the H8S.
    
           **-mn** Generate code for the H8S and H8/300H in the normal mode.
               This switch must be used either with **-mh** or **-ms**.
    
           **-ms2600**
               Generate code for the H8S/2600.  This switch must be used with
               **-ms**.
    
           **-mexr**
               Extended registers are stored on stack before execution of
               function with monitor attribute. Default option is **-mexr**.
               This option is valid only for H8S targets.
    
           **-mno-exr**
               Extended registers are not stored on stack before execution of
               function with monitor attribute. Default option is **-mno-exr**.
               This option is valid only for H8S targets.
    
           **-mint32**
               Make "int" data 32 bits by default.
    
           **-malign-300**
               On the H8/300H and H8S, use the same alignment rules as for
               the H8/300.  The default for the H8/300H and H8S is to align
               longs and floats on 4-byte boundaries.  **-malign-300** causes
               them to be aligned on 2-byte boundaries.  This option has no
               effect on the H8/300.
    
           _HPPA Options_
    
           These **-m** options are defined for the HPPA family of computers:
    
           **-march=**_architecture-type_
               Generate code for the specified architecture.  The choices for
               _architecture-type_ are **1.0** for PA 1.0, **1.1** for PA 1.1, and **2.0**
               for PA 2.0 processors.  Refer to _/usr/lib/sched.models_ on an
               HP-UX system to determine the proper architecture option for
               your machine.  Code compiled for lower numbered architectures
               runs on higher numbered architectures, but not the other way
               around.
    
           **-mpa-risc-1-0**
           **-mpa-risc-1-1**
           **-mpa-risc-2-0**
               Synonyms for **-march=1.0** , **-march=1.1** , and **-march=2.0**
               respectively.
    
           **-mcaller-copies**
               The caller copies function arguments passed by hidden
               reference.  This option should be used with care as it is not
               compatible with the default 32-bit runtime.  However, only
               aggregates larger than eight bytes are passed by hidden
               reference and the option provides better compatibility with
               OpenMP.
    
           **-mjump-in-delay**
               This option is ignored and provided for compatibility purposes
               only.
    
           **-mdisable-fpregs**
               Prevent floating-point registers from being used in any
               manner.  This is necessary for compiling kernels that perform
               lazy context switching of floating-point registers.  If you
               use this option and attempt to perform floating-point
               operations, the compiler aborts.
    
           **-mdisable-indexing**
               Prevent the compiler from using indexing address modes.  This
               avoids some rather obscure problems when compiling MIG
               generated code under MACH.
    
           **-mno-space-regs**
               Generate code that assumes the target has no space registers.
               This allows GCC to generate faster indirect calls and use
               unscaled index address modes.
    
               Such code is suitable for level 0 PA systems and kernels.
    
           **-mfast-indirect-calls**
               Generate code that assumes calls never cross space boundaries.
               This allows GCC to emit code that performs faster indirect
               calls.
    
               This option does not work in the presence of shared libraries
               or nested functions.
    
           **-mfixed-range=**_register-range_
               Generate code treating the given register range as fixed
               registers.  A fixed register is one that the register
               allocator cannot use.  This is useful when compiling kernel
               code.  A register range is specified as two registers
               separated by a dash.  Multiple register ranges can be
               specified separated by a comma.
    
           **-mlong-load-store**
               Generate 3-instruction load and store sequences as sometimes
               required by the HP-UX 10 linker.  This is equivalent to the **+k**
               option to the HP compilers.
    
           **-mportable-runtime**
               Use the portable calling conventions proposed by HP for ELF
               systems.
    
           **-mgas**
               Enable the use of assembler directives only GAS understands.
    
           **-mschedule=**_cpu-type_
               Schedule code according to the constraints for the machine
               type _cpu-type_.  The choices for _cpu-type_ are **700 7100** , **7100LC** ,
               **7200** , **7300** and **8000**.  Refer to _/usr/lib/sched.models_ on an HP-
               UX system to determine the proper scheduling option for your
               machine.  The default scheduling is **8000**.
    
           **-mlinker-opt**
               Enable the optimization pass in the HP-UX linker.  Note this
               makes symbolic debugging impossible.  It also triggers a bug
               in the HP-UX 8 and HP-UX 9 linkers in which they give bogus
               error messages when linking some programs.
    
           **-msoft-float**
               Generate output containing library calls for floating point.
               **Warning:** the requisite libraries are not available for all
               HPPA targets.  Normally the facilities of the machine's usual
               C compiler are used, but this cannot be done directly in
               cross-compilation.  You must make your own arrangements to
               provide suitable library functions for cross-compilation.
    
               **-msoft-float** changes the calling convention in the output
               file; therefore, it is only useful if you compile _all_ of a
               program with this option.  In particular, you need to compile
               _libgcc.a_ , the library that comes with GCC, with **-msoft-float**
               in order for this to work.
    
           **-msio**
               Generate the predefine, "_SIO", for server IO.  The default is
               **-mwsio**.  This generates the predefines, "__hp9000s700",
               "__hp9000s700__" and "_WSIO", for workstation IO.  These
               options are available under HP-UX and HI-UX.
    
           **-mgnu-ld**
               Use options specific to GNU **ld**.  This passes **-shared** to **ld**
               when building a shared library.  It is the default when GCC is
               configured, explicitly or implicitly, with the GNU linker.
               This option does not affect which **ld** is called; it only
               changes what parameters are passed to that **ld**.  The **ld** that is
               called is determined by the **--with-ld** configure option, GCC's
               program search path, and finally by the user's **PATH**.  The
               linker used by GCC can be printed using **which `gcc**
               **-print-prog-name=ld`**.  This option is only available on the
               64-bit HP-UX GCC, i.e. configured with **hppa*64*-*-hpux***.
    
           **-mhp-ld**
               Use options specific to HP **ld**.  This passes **-b** to **ld** when
               building a shared library and passes **+Accept TypeMismatch** to
               **ld** on all links.  It is the default when GCC is configured,
               explicitly or implicitly, with the HP linker.  This option
               does not affect which **ld** is called; it only changes what
               parameters are passed to that **ld**.  The **ld** that is called is
               determined by the **--with-ld** configure option, GCC's program
               search path, and finally by the user's **PATH**.  The linker used
               by GCC can be printed using **which `gcc -print-prog-name=ld`**.
               This option is only available on the 64-bit HP-UX GCC, i.e.
               configured with **hppa*64*-*-hpux***.
    
           **-mlong-calls**
               Generate code that uses long call sequences.  This ensures
               that a call is always able to reach linker generated stubs.
               The default is to generate long calls only when the distance
               from the call site to the beginning of the function or
               translation unit, as the case may be, exceeds a predefined
               limit set by the branch type being used.  The limits for
               normal calls are 7,600,000 and 240,000 bytes, respectively for
               the PA 2.0 and PA 1.X architectures.  Sibcalls are always
               limited at 240,000 bytes.
    
               Distances are measured from the beginning of functions when
               using the **-ffunction-sections** option, or when using the **-mgas**
               and **-mno-portable-runtime** options together under HP-UX with
               the SOM linker.
    
               It is normally not desirable to use this option as it degrades
               performance.  However, it may be useful in large applications,
               particularly when partial linking is used to build the
               application.
    
               The types of long calls used depends on the capabilities of
               the assembler and linker, and the type of code being
               generated.  The impact on systems that support long absolute
               calls, and long pic symbol-difference or pc-relative calls
               should be relatively small.  However, an indirect call is used
               on 32-bit ELF systems in pic code and it is quite long.
    
           **-munix=**_unix-std_
               Generate compiler predefines and select a startfile for the
               specified UNIX standard.  The choices for _unix-std_ are **93** , **95**
               and **98**.  **93** is supported on all HP-UX versions.  **95** is
               available on HP-UX 10.10 and later.  **98** is available on HP-UX
               11.11 and later.  The default values are **93** for HP-UX 10.00,
               **95** for HP-UX 10.10 though to 11.00, and **98** for HP-UX 11.11 and
               later.
    
               **-munix=93** provides the same predefines as GCC 3.3 and 3.4.
               **-munix=95** provides additional predefines for "XOPEN_UNIX" and
               "_XOPEN_SOURCE_EXTENDED", and the startfile _unix95.o_.
               **-munix=98** provides additional predefines for "_XOPEN_UNIX",
               "_XOPEN_SOURCE_EXTENDED", "_INCLUDE__STDC_A1_SOURCE" and
               "_INCLUDE_XOPEN_SOURCE_500", and the startfile _unix98.o_.
    
               It is _important_ to note that this option changes the
               interfaces for various library routines.  It also affects the
               operational behavior of the C library.  Thus, _extreme_ care is
               needed in using this option.
    
               Library code that is intended to operate with more than one
               UNIX standard must test, set and restore the variable
               "__xpg4_extended_mask" as appropriate.  Most GNU software
               doesn't provide this capability.
    
           **-nolibdld**
               Suppress the generation of link options to search libdld.sl
               when the **-static** option is specified on HP-UX 10 and later.
    
           **-static**
               The HP-UX implementation of setlocale in libc has a dependency
               on libdld.sl.  There isn't an archive version of libdld.sl.
               Thus, when the **-static** option is specified, special link
               options are needed to resolve this dependency.
    
               On HP-UX 10 and later, the GCC driver adds the necessary
               options to link with libdld.sl when the **-static** option is
               specified.  This causes the resulting binary to be dynamic.
               On the 64-bit port, the linkers generate dynamic binaries by
               default in any case.  The **-nolibdld** option can be used to
               prevent the GCC driver from adding these link options.
    
           **-threads**
               Add support for multithreading with the _dce thread_ library
               under HP-UX.  This option sets flags for both the preprocessor
               and linker.
    
           _IA-64 Options_
    
           These are the **-m** options defined for the Intel IA-64 architecture.
    
           **-mbig-endian**
               Generate code for a big-endian target.  This is the default
               for HP-UX.
    
           **-mlittle-endian**
               Generate code for a little-endian target.  This is the default
               for AIX5 and GNU/Linux.
    
           **-mgnu-as**
           **-mno-gnu-as**
               Generate (or don't) code for the GNU assembler.  This is the
               default.
    
           **-mgnu-ld**
           **-mno-gnu-ld**
               Generate (or don't) code for the GNU linker.  This is the
               default.
    
           **-mno-pic**
               Generate code that does not use a global pointer register.
               The result is not position independent code, and violates the
               IA-64 ABI.
    
           **-mvolatile-asm-stop**
           **-mno-volatile-asm-stop**
               Generate (or don't) a stop bit immediately before and after
               volatile asm statements.
    
           **-mregister-names**
           **-mno-register-names**
               Generate (or don't) **in** , **loc** , and **out** register names for the
               stacked registers.  This may make assembler output more
               readable.
    
           **-mno-sdata**
           **-msdata**
               Disable (or enable) optimizations that use the small data
               section.  This may be useful for working around optimizer
               bugs.
    
           **-mconstant-gp**
               Generate code that uses a single constant global pointer
               value.  This is useful when compiling kernel code.
    
           **-mauto-pic**
               Generate code that is self-relocatable.  This implies
               **-mconstant-gp**.  This is useful when compiling firmware code.
    
           **-minline-float-divide-min-latency**
               Generate code for inline divides of floating-point values
               using the minimum latency algorithm.
    
           **-minline-float-divide-max-throughput**
               Generate code for inline divides of floating-point values
               using the maximum throughput algorithm.
    
           **-mno-inline-float-divide**
               Do not generate inline code for divides of floating-point
               values.
    
           **-minline-int-divide-min-latency**
               Generate code for inline divides of integer values using the
               minimum latency algorithm.
    
           **-minline-int-divide-max-throughput**
               Generate code for inline divides of integer values using the
               maximum throughput algorithm.
    
           **-mno-inline-int-divide**
               Do not generate inline code for divides of integer values.
    
           **-minline-sqrt-min-latency**
               Generate code for inline square roots using the minimum
               latency algorithm.
    
           **-minline-sqrt-max-throughput**
               Generate code for inline square roots using the maximum
               throughput algorithm.
    
           **-mno-inline-sqrt**
               Do not generate inline code for "sqrt".
    
           **-mfused-madd**
           **-mno-fused-madd**
               Do (don't) generate code that uses the fused multiply/add or
               multiply/subtract instructions.  The default is to use these
               instructions.
    
           **-mno-dwarf2-asm**
           **-mdwarf2-asm**
               Don't (or do) generate assembler code for the DWARF line
               number debugging info.  This may be useful when not using the
               GNU assembler.
    
           **-mearly-stop-bits**
           **-mno-early-stop-bits**
               Allow stop bits to be placed earlier than immediately
               preceding the instruction that triggered the stop bit.  This
               can improve instruction scheduling, but does not always do so.
    
           **-mfixed-range=**_register-range_
               Generate code treating the given register range as fixed
               registers.  A fixed register is one that the register
               allocator cannot use.  This is useful when compiling kernel
               code.  A register range is specified as two registers
               separated by a dash.  Multiple register ranges can be
               specified separated by a comma.
    
           **-mtls-size=**_tls-size_
               Specify bit size of immediate TLS offsets.  Valid values are
               14, 22, and 64.
    
           **-mtune=**_cpu-type_
               Tune the instruction scheduling for a particular CPU, Valid
               values are **itanium** , **itanium1** , **merced** , **itanium2** , and **mckinley**.
    
           **-milp32**
           **-mlp64**
               Generate code for a 32-bit or 64-bit environment.  The 32-bit
               environment sets int, long and pointer to 32 bits.  The 64-bit
               environment sets int to 32 bits and long and pointer to 64
               bits.  These are HP-UX specific flags.
    
           **-mno-sched-br-data-spec**
           **-msched-br-data-spec**
               (Dis/En)able data speculative scheduling before reload.  This
               results in generation of "ld.a" instructions and the
               corresponding check instructions ("ld.c" / "chk.a").  The
               default setting is disabled.
    
           **-msched-ar-data-spec**
           **-mno-sched-ar-data-spec**
               (En/Dis)able data speculative scheduling after reload.  This
               results in generation of "ld.a" instructions and the
               corresponding check instructions ("ld.c" / "chk.a").  The
               default setting is enabled.
    
           **-mno-sched-control-spec**
           **-msched-control-spec**
               (Dis/En)able control speculative scheduling.  This feature is
               available only during region scheduling (i.e. before reload).
               This results in generation of the "ld.s" instructions and the
               corresponding check instructions "chk.s".  The default setting
               is disabled.
    
           **-msched-br-in-data-spec**
           **-mno-sched-br-in-data-spec**
               (En/Dis)able speculative scheduling of the instructions that
               are dependent on the data speculative loads before reload.
               This is effective only with **-msched-br-data-spec** enabled.  The
               default setting is enabled.
    
           **-msched-ar-in-data-spec**
           **-mno-sched-ar-in-data-spec**
               (En/Dis)able speculative scheduling of the instructions that
               are dependent on the data speculative loads after reload.
               This is effective only with **-msched-ar-data-spec** enabled.  The
               default setting is enabled.
    
           **-msched-in-control-spec**
           **-mno-sched-in-control-spec**
               (En/Dis)able speculative scheduling of the instructions that
               are dependent on the control speculative loads.  This is
               effective only with **-msched-control-spec** enabled.  The default
               setting is enabled.
    
           **-mno-sched-prefer-non-data-spec-insns**
           **-msched-prefer-non-data-spec-insns**
               If enabled, data-speculative instructions are chosen for
               schedule only if there are no other choices at the moment.
               This makes the use of the data speculation much more
               conservative.  The default setting is disabled.
    
           **-mno-sched-prefer-non-control-spec-insns**
           **-msched-prefer-non-control-spec-insns**
               If enabled, control-speculative instructions are chosen for
               schedule only if there are no other choices at the moment.
               This makes the use of the control speculation much more
               conservative.  The default setting is disabled.
    
           **-mno-sched-count-spec-in-critical-path**
           **-msched-count-spec-in-critical-path**
               If enabled, speculative dependencies are considered during
               computation of the instructions priorities.  This makes the
               use of the speculation a bit more conservative.  The default
               setting is disabled.
    
           **-msched-spec-ldc**
               Use a simple data speculation check.  This option is on by
               default.
    
           **-msched-control-spec-ldc**
               Use a simple check for control speculation.  This option is on
               by default.
    
           **-msched-stop-bits-after-every-cycle**
               Place a stop bit after every cycle when scheduling.  This
               option is on by default.
    
           **-msched-fp-mem-deps-zero-cost**
               Assume that floating-point stores and loads are not likely to
               cause a conflict when placed into the same instruction group.
               This option is disabled by default.
    
           **-msel-sched-dont-check-control-spec**
               Generate checks for control speculation in selective
               scheduling.  This flag is disabled by default.
    
           **-msched-max-memory-insns=**_max-insns_
               Limit on the number of memory insns per instruction group,
               giving lower priority to subsequent memory insns attempting to
               schedule in the same instruction group. Frequently useful to
               prevent cache bank conflicts.  The default value is 1.
    
           **-msched-max-memory-insns-hard-limit**
               Makes the limit specified by **msched-max-memory-insns** a hard
               limit, disallowing more than that number in an instruction
               group.  Otherwise, the limit is "soft", meaning that non-
               memory operations are preferred when the limit is reached, but
               memory operations may still be scheduled.
    
           _LM32 Options_
    
           These **-m** options are defined for the LatticeMico32 architecture:
    
           **-mbarrel-shift-enabled**
               Enable barrel-shift instructions.
    
           **-mdivide-enabled**
               Enable divide and modulus instructions.
    
           **-mmultiply-enabled**
               Enable multiply instructions.
    
           **-msign-extend-enabled**
               Enable sign extend instructions.
    
           **-muser-enabled**
               Enable user-defined instructions.
    
           _M32C Options_
    
           **-mcpu=**_name_
               Select the CPU for which code is generated.  _name_ may be one
               of **r8c** for the R8C/Tiny series, **m16c** for the M16C (up to /60)
               series, **m32cm** for the M16C/80 series, or **m32c** for the M32C/80
               series.
    
           **-msim**
               Specifies that the program will be run on the simulator.  This
               causes an alternate runtime library to be linked in which
               supports, for example, file I/O.  You must not use this option
               when generating programs that will run on real hardware; you
               must provide your own runtime library for whatever I/O
               functions are needed.
    
           **-memregs=**_number_
               Specifies the number of memory-based pseudo-registers GCC uses
               during code generation.  These pseudo-registers are used like
               real registers, so there is a tradeoff between GCC's ability
               to fit the code into available registers, and the performance
               penalty of using memory instead of registers.  Note that all
               modules in a program must be compiled with the same value for
               this option.  Because of that, you must not use this option
               with GCC's default runtime libraries.
    
           _M32R/D Options_
    
           These **-m** options are defined for Renesas M32R/D architectures:
    
           **-m32r2**
               Generate code for the M32R/2.
    
           **-m32rx**
               Generate code for the M32R/X.
    
           **-m32r**
               Generate code for the M32R.  This is the default.
    
           **-mmodel=small**
               Assume all objects live in the lower 16MB of memory (so that
               their addresses can be loaded with the "ld24" instruction),
               and assume all subroutines are reachable with the "bl"
               instruction.  This is the default.
    
               The addressability of a particular object can be set with the
               "model" attribute.
    
           **-mmodel=medium**
               Assume objects may be anywhere in the 32-bit address space
               (the compiler generates "seth/add3" instructions to load their
               addresses), and assume all subroutines are reachable with the
               "bl" instruction.
    
           **-mmodel=large**
               Assume objects may be anywhere in the 32-bit address space
               (the compiler generates "seth/add3" instructions to load their
               addresses), and assume subroutines may not be reachable with
               the "bl" instruction (the compiler generates the much slower
               "seth/add3/jl" instruction sequence).
    
           **-msdata=none**
               Disable use of the small data area.  Variables are put into
               one of ".data", ".bss", or ".rodata" (unless the "section"
               attribute has been specified).  This is the default.
    
               The small data area consists of sections ".sdata" and ".sbss".
               Objects may be explicitly put in the small data area with the
               "section" attribute using one of these sections.
    
           **-msdata=sdata**
               Put small global and static data in the small data area, but
               do not generate special code to reference them.
    
           **-msdata=use**
               Put small global and static data in the small data area, and
               generate special instructions to reference them.
    
           **-G** _num_
               Put global and static objects less than or equal to _num_ bytes
               into the small data or BSS sections instead of the normal data
               or BSS sections.  The default value of _num_ is 8.  The **-msdata**
               option must be set to one of **sdata** or **use** for this option to
               have any effect.
    
               All modules should be compiled with the same **-G** _num_ value.
               Compiling with different values of _num_ may or may not work; if
               it doesn't the linker gives an error message---incorrect code
               is not generated.
    
           **-mdebug**
               Makes the M32R-specific code in the compiler display some
               statistics that might help in debugging programs.
    
           **-malign-loops**
               Align all loops to a 32-byte boundary.
    
           **-mno-align-loops**
               Do not enforce a 32-byte alignment for loops.  This is the
               default.
    
           **-missue-rate=**_number_
               Issue _number_ instructions per cycle.  _number_ can only be 1 or
               2.
    
           **-mbranch-cost=**_number_
               _number_ can only be 1 or 2.  If it is 1 then branches are
               preferred over conditional code, if it is 2, then the opposite
               applies.
    
           **-mflush-trap=**_number_
               Specifies the trap number to use to flush the cache.  The
               default is 12.  Valid numbers are between 0 and 15 inclusive.
    
           **-mno-flush-trap**
               Specifies that the cache cannot be flushed by using a trap.
    
           **-mflush-func=**_name_
               Specifies the name of the operating system function to call to
               flush the cache.  The default is **_flush_cache** , but a function
               call is only used if a trap is not available.
    
           **-mno-flush-func**
               Indicates that there is no OS function for flushing the cache.
    
           _M680x0 Options_
    
           These are the **-m** options defined for M680x0 and ColdFire
           processors.  The default settings depend on which architecture was
           selected when the compiler was configured; the defaults for the
           most common choices are given below.
    
           **-march=**_arch_
               Generate code for a specific M680x0 or ColdFire instruction
               set architecture.  Permissible values of _arch_ for M680x0
               architectures are: **68000** , **68010** , **68020** , **68030** , **68040** , **68060**
               and **cpu32**.  ColdFire architectures are selected according to
               Freescale's ISA classification and the permissible values are:
               **isaa** , **isaaplus** , **isab** and **isac**.
    
               GCC defines a macro "__mcf _arch__"_ whenever it is generating
               code for a ColdFire target.  The _arch_ in this macro is one of
               the **-march** arguments given above.
    
               When used together, **-march** and **-mtune** select code that runs on
               a family of similar processors but that is optimized for a
               particular microarchitecture.
    
           **-mcpu=**_cpu_
               Generate code for a specific M680x0 or ColdFire processor.
               The M680x0 _cpu_ s are: **68000** , **68010** , **68020** , **68030** , **68040** , **68060** ,
               **68302** , **68332** and **cpu32**.  The ColdFire _cpu_ s are given by the
               table below, which also classifies the CPUs into families:
    
               Family : **-mcpu** arguments
               **51** : **51 51ac 51ag 51cn 51em 51je 51jf 51jg 51jm 51mm 51qe 51qm**
               **5206** : **5202 5204 5206**
               **5206e** : **5206e**
               **5208** : **5207 5208**
               **5211a** : **5210a 5211a**
               **5213** : **5211 5212 5213**
               **5216** : **5214 5216**
               **52235** : **52230 52231 52232 52233 52234 52235**
               **5225** : **5224 5225**
               **52259** : **52252 52254 52255 52256 52258 52259**
               **5235** : **5232 5233 5234 5235 523x**
               **5249** : **5249**
               **5250** : **5250**
               **5271** : **5270 5271**
               **5272** : **5272**
               **5275** : **5274 5275**
               **5282** : **5280 5281 5282 528x**
               **53017** : **53011 53012 53013 53014 53015 53016 53017**
               **5307** : **5307**
               **5329** : **5327 5328 5329 532x**
               **5373** : **5372 5373 537x**
               **5407** : **5407**
               **5475** : **5470 5471 5472 5473 5474 5475 547x 5480 5481 5482 5483**
               **5484 5485**
    
               **-mcpu=**_cpu_ overrides **-march=**_arch_ if _arch_ is compatible with
               _cpu_.  Other combinations of **-mcpu** and **-march** are rejected.
    
               GCC defines the macro "__mcf_cpu__cpu"_ when ColdFire target _cpu_
               is selected.  It also defines "__mcf_family__family"_ , where the
               value of _family_ is given by the table above.
    
           **-mtune=**_tune_
               Tune the code for a particular microarchitecture within the
               constraints set by **-march** and **-mcpu**.  The M680x0
               microarchitectures are: **68000** , **68010** , **68020** , **68030** , **68040** ,
               **68060** and **cpu32**.  The ColdFire microarchitectures are: **cfv1** ,
               **cfv2** , **cfv3** , **cfv4** and **cfv4e**.
    
               You can also use **-mtune=68020-40** for code that needs to run
               relatively well on 68020, 68030 and 68040 targets.
               **-mtune=68020-60** is similar but includes 68060 targets as well.
               These two options select the same tuning decisions as
               **-m68020-40** and **-m68020-60** respectively.
    
               GCC defines the macros "__mc _arch"_ and "__mc _arch__"_ when tuning
               for 680x0 architecture _arch_.  It also defines "mc _arch"_ unless
               either **-ansi** or a non-GNU **-std** option is used.  If GCC is
               tuning for a range of architectures, as selected by
               **-mtune=68020-40** or **-mtune=68020-60** , it defines the macros for
               every architecture in the range.
    
               GCC also defines the macro "__m _uarch__"_ when tuning for
               ColdFire microarchitecture _uarch_ , where _uarch_ is one of the
               arguments given above.
    
           **-m68000**
           **-mc68000**
               Generate output for a 68000.  This is the default when the
               compiler is configured for 68000-based systems.  It is
               equivalent to **-march=68000**.
    
               Use this option for microcontrollers with a 68000 or EC000
               core, including the 68008, 68302, 68306, 68307, 68322, 68328
               and 68356.
    
           **-m68010**
               Generate output for a 68010.  This is the default when the
               compiler is configured for 68010-based systems.  It is
               equivalent to **-march=68010**.
    
           **-m68020**
           **-mc68020**
               Generate output for a 68020.  This is the default when the
               compiler is configured for 68020-based systems.  It is
               equivalent to **-march=68020**.
    
           **-m68030**
               Generate output for a 68030.  This is the default when the
               compiler is configured for 68030-based systems.  It is
               equivalent to **-march=68030**.
    
           **-m68040**
               Generate output for a 68040.  This is the default when the
               compiler is configured for 68040-based systems.  It is
               equivalent to **-march=68040**.
    
               This option inhibits the use of 68881/68882 instructions that
               have to be emulated by software on the 68040.  Use this option
               if your 68040 does not have code to emulate those
               instructions.
    
           **-m68060**
               Generate output for a 68060.  This is the default when the
               compiler is configured for 68060-based systems.  It is
               equivalent to **-march=68060**.
    
               This option inhibits the use of 68020 and 68881/68882
               instructions that have to be emulated by software on the
               68060.  Use this option if your 68060 does not have code to
               emulate those instructions.
    
           **-mcpu32**
               Generate output for a CPU32.  This is the default when the
               compiler is configured for CPU32-based systems.  It is
               equivalent to **-march=cpu32**.
    
               Use this option for microcontrollers with a CPU32 or CPU32+
               core, including the 68330, 68331, 68332, 68333, 68334, 68336,
               68340, 68341, 68349 and 68360.
    
           **-m5200**
               Generate output for a 520X ColdFire CPU.  This is the default
               when the compiler is configured for 520X-based systems.  It is
               equivalent to **-mcpu=5206** , and is now deprecated in favor of
               that option.
    
               Use this option for microcontroller with a 5200 core,
               including the MCF5202, MCF5203, MCF5204 and MCF5206.
    
           **-m5206e**
               Generate output for a 5206e ColdFire CPU.  The option is now
               deprecated in favor of the equivalent **-mcpu=5206e**.
    
           **-m528x**
               Generate output for a member of the ColdFire 528X family.  The
               option is now deprecated in favor of the equivalent
               **-mcpu=528x**.
    
           **-m5307**
               Generate output for a ColdFire 5307 CPU.  The option is now
               deprecated in favor of the equivalent **-mcpu=5307**.
    
           **-m5407**
               Generate output for a ColdFire 5407 CPU.  The option is now
               deprecated in favor of the equivalent **-mcpu=5407**.
    
           **-mcfv4e**
               Generate output for a ColdFire V4e family CPU (e.g.
               547x/548x).  This includes use of hardware floating-point
               instructions.  The option is equivalent to **-mcpu=547x** , and is
               now deprecated in favor of that option.
    
           **-m68020-40**
               Generate output for a 68040, without using any of the new
               instructions.  This results in code that can run relatively
               efficiently on either a 68020/68881 or a 68030 or a 68040.
               The generated code does use the 68881 instructions that are
               emulated on the 68040.
    
               The option is equivalent to **-march=68020 -mtune=68020-40**.
    
           **-m68020-60**
               Generate output for a 68060, without using any of the new
               instructions.  This results in code that can run relatively
               efficiently on either a 68020/68881 or a 68030 or a 68040.
               The generated code does use the 68881 instructions that are
               emulated on the 68060.
    
               The option is equivalent to **-march=68020 -mtune=68020-60**.
    
           **-mhard-float**
           **-m68881**
               Generate floating-point instructions.  This is the default for
               68020 and above, and for ColdFire devices that have an FPU.
               It defines the macro "__HAVE_68881__" on M680x0 targets and
               "__mcffpu__" on ColdFire targets.
    
           **-msoft-float**
               Do not generate floating-point instructions; use library calls
               instead.  This is the default for 68000, 68010, and 68832
               targets.  It is also the default for ColdFire devices that
               have no FPU.
    
           **-mdiv**
           **-mno-div**
               Generate (do not generate) ColdFire hardware divide and
               remainder instructions.  If **-march** is used without **-mcpu** , the
               default is "on" for ColdFire architectures and "off" for
               M680x0 architectures.  Otherwise, the default is taken from
               the target CPU (either the default CPU, or the one specified
               by **-mcpu**).  For example, the default is "off" for **-mcpu=5206**
               and "on" for **-mcpu=5206e**.
    
               GCC defines the macro "__mcfhwdiv__" when this option is
               enabled.
    
           **-mshort**
               Consider type "int" to be 16 bits wide, like "short int".
               Additionally, parameters passed on the stack are also aligned
               to a 16-bit boundary even on targets whose API mandates
               promotion to 32-bit.
    
           **-mno-short**
               Do not consider type "int" to be 16 bits wide.  This is the
               default.
    
           **-mnobitfield**
           **-mno-bitfield**
               Do not use the bit-field instructions.  The **-m68000** , **-mcpu32**
               and **-m5200** options imply **-mnobitfield**.
    
           **-mbitfield**
               Do use the bit-field instructions.  The **-m68020** option implies
               **-mbitfield**.  This is the default if you use a configuration
               designed for a 68020.
    
           **-mrtd**
               Use a different function-calling convention, in which
               functions that take a fixed number of arguments return with
               the "rtd" instruction, which pops their arguments while
               returning.  This saves one instruction in the caller since
               there is no need to pop the arguments there.
    
               This calling convention is incompatible with the one normally
               used on Unix, so you cannot use it if you need to call
               libraries compiled with the Unix compiler.
    
               Also, you must provide function prototypes for all functions
               that take variable numbers of arguments (including "printf");
               otherwise incorrect code is generated for calls to those
               functions.
    
               In addition, seriously incorrect code results if you call a
               function with too many arguments.  (Normally, extra arguments
               are harmlessly ignored.)
    
               The "rtd" instruction is supported by the 68010, 68020, 68030,
               68040, 68060 and CPU32 processors, but not by the 68000 or
               5200.
    
               The default is **-mno-rtd**.
    
           **-malign-int**
           **-mno-align-int**
               Control whether GCC aligns "int", "long", "long long",
               "float", "double", and "long double" variables on a 32-bit
               boundary (**-malign-int**) or a 16-bit boundary (**-mno-align-int**).
               Aligning variables on 32-bit boundaries produces code that
               runs somewhat faster on processors with 32-bit busses at the
               expense of more memory.
    
               **Warning:** if you use the **-malign-int** switch, GCC aligns
               structures containing the above types differently than most
               published application binary interface specifications for the
               m68k.
    
           **-mpcrel**
               Use the pc-relative addressing mode of the 68000 directly,
               instead of using a global offset table.  At present, this
               option implies **-fpic** , allowing at most a 16-bit offset for pc-
               relative addressing.  **-fPIC** is not presently supported with
               **-mpcrel** , though this could be supported for 68020 and higher
               processors.
    
           **-mno-strict-align**
           **-mstrict-align**
               Do not (do) assume that unaligned memory references are
               handled by the system.
    
           **-msep-data**
               Generate code that allows the data segment to be located in a
               different area of memory from the text segment.  This allows
               for execute-in-place in an environment without virtual memory
               management.  This option implies **-fPIC**.
    
           **-mno-sep-data**
               Generate code that assumes that the data segment follows the
               text segment.  This is the default.
    
           **-mid-shared-library**
               Generate code that supports shared libraries via the library
               ID method.  This allows for execute-in-place and shared
               libraries in an environment without virtual memory management.
               This option implies **-fPIC**.
    
           **-mno-id-shared-library**
               Generate code that doesn't assume ID-based shared libraries
               are being used.  This is the default.
    
           **-mshared-library-id=n**
               Specifies the identification number of the ID-based shared
               library being compiled.  Specifying a value of 0 generates
               more compact code; specifying other values forces the
               allocation of that number to the current library, but is no
               more space- or time-efficient than omitting this option.
    
           **-mxgot**
           **-mno-xgot**
               When generating position-independent code for ColdFire,
               generate code that works if the GOT has more than 8192
               entries.  This code is larger and slower than code generated
               without this option.  On M680x0 processors, this option is not
               needed; **-fPIC** suffices.
    
               GCC normally uses a single instruction to load values from the
               GOT.  While this is relatively efficient, it only works if the
               GOT is smaller than about 64k.  Anything larger causes the
               linker to report an error such as:
    
                       relocation truncated to fit: R_68K_GOT16O foobar
    
               If this happens, you should recompile your code with **-mxgot**.
               It should then work with very large GOTs.  However, code
               generated with **-mxgot** is less efficient, since it takes 4
               instructions to fetch the value of a global symbol.
    
               Note that some linkers, including newer versions of the GNU
               linker, can create multiple GOTs and sort GOT entries.  If you
               have such a linker, you should only need to use **-mxgot** when
               compiling a single object file that accesses more than 8192
               GOT entries.  Very few do.
    
               These options have no effect unless GCC is generating
               position-independent code.
    
           **-mlong-jump-table-offsets**
               Use 32-bit offsets in "switch" tables.  The default is to use
               16-bit offsets.
    
           _MCore Options_
    
           These are the **-m** options defined for the Motorola M*Core
           processors.
    
           **-mhardlit**
           **-mno-hardlit**
               Inline constants into the code stream if it can be done in two
               instructions or less.
    
           **-mdiv**
           **-mno-div**
               Use the divide instruction.  (Enabled by default).
    
           **-mrelax-immediate**
           **-mno-relax-immediate**
               Allow arbitrary-sized immediates in bit operations.
    
           **-mwide-bitfields**
           **-mno-wide-bitfields**
               Always treat bit-fields as "int"-sized.
    
           **-m4byte-functions**
           **-mno-4byte-functions**
               Force all functions to be aligned to a 4-byte boundary.
    
           **-mcallgraph-data**
           **-mno-callgraph-data**
               Emit callgraph information.
    
           **-mslow-bytes**
           **-mno-slow-bytes**
               Prefer word access when reading byte quantities.
    
           **-mlittle-endian**
           **-mbig-endian**
               Generate code for a little-endian target.
    
           **-m210**
           **-m340**
               Generate code for the 210 processor.
    
           **-mno-lsim**
               Assume that runtime support has been provided and so omit the
               simulator library (_libsim.a)_ from the linker command line.
    
           **-mstack-increment=**_size_
               Set the maximum amount for a single stack increment operation.
               Large values can increase the speed of programs that contain
               functions that need a large amount of stack space, but they
               can also trigger a segmentation fault if the stack is extended
               too much.  The default value is 0x1000.
    
           _MeP Options_
    
           **-mabsdiff**
               Enables the "abs" instruction, which is the absolute
               difference between two registers.
    
           **-mall-opts**
               Enables all the optional instructions---average, multiply,
               divide, bit operations, leading zero, absolute difference,
               min/max, clip, and saturation.
    
           **-maverage**
               Enables the "ave" instruction, which computes the average of
               two registers.
    
           **-mbased=**_n_
               Variables of size _n_ bytes or smaller are placed in the
               ".based" section by default.  Based variables use the $tp
               register as a base register, and there is a 128-byte limit to
               the ".based" section.
    
           **-mbitops**
               Enables the bit operation instructions---bit test ("btstm"),
               set ("bsetm"), clear ("bclrm"), invert ("bnotm"), and test-
               and-set ("tas").
    
           **-mc=**_name_
               Selects which section constant data is placed in.  _name_ may be
               **tiny** , **near** , or **far**.
    
           **-mclip**
               Enables the "clip" instruction.  Note that **-mclip** is not
               useful unless you also provide **-mminmax**.
    
           **-mconfig=**_name_
               Selects one of the built-in core configurations.  Each MeP
               chip has one or more modules in it; each module has a core CPU
               and a variety of coprocessors, optional instructions, and
               peripherals.  The "MeP-Integrator" tool, not part of GCC,
               provides these configurations through this option; using this
               option is the same as using all the corresponding command-line
               options.  The default configuration is **default**.
    
           **-mcop**
               Enables the coprocessor instructions.  By default, this is a
               32-bit coprocessor.  Note that the coprocessor is normally
               enabled via the **-mconfig=** option.
    
           **-mcop32**
               Enables the 32-bit coprocessor's instructions.
    
           **-mcop64**
               Enables the 64-bit coprocessor's instructions.
    
           **-mivc2**
               Enables IVC2 scheduling.  IVC2 is a 64-bit VLIW coprocessor.
    
           **-mdc**
               Causes constant variables to be placed in the ".near" section.
    
           **-mdiv**
               Enables the "div" and "divu" instructions.
    
           **-meb**
               Generate big-endian code.
    
           **-mel**
               Generate little-endian code.
    
           **-mio-volatile**
               Tells the compiler that any variable marked with the "io"
               attribute is to be considered volatile.
    
           **-ml** Causes variables to be assigned to the ".far" section by
               default.
    
           **-mleadz**
               Enables the "leadz" (leading zero) instruction.
    
           **-mm** Causes variables to be assigned to the ".near" section by
               default.
    
           **-mminmax**
               Enables the "min" and "max" instructions.
    
           **-mmult**
               Enables the multiplication and multiply-accumulate
               instructions.
    
           **-mno-opts**
               Disables all the optional instructions enabled by **-mall-opts**.
    
           **-mrepeat**
               Enables the "repeat" and "erepeat" instructions, used for low-
               overhead looping.
    
           **-ms** Causes all variables to default to the ".tiny" section.  Note
               that there is a 65536-byte limit to this section.  Accesses to
               these variables use the %gp base register.
    
           **-msatur**
               Enables the saturation instructions.  Note that the compiler
               does not currently generate these itself, but this option is
               included for compatibility with other tools, like "as".
    
           **-msdram**
               Link the SDRAM-based runtime instead of the default ROM-based
               runtime.
    
           **-msim**
               Link the simulator run-time libraries.
    
           **-msimnovec**
               Link the simulator runtime libraries, excluding built-in
               support for reset and exception vectors and tables.
    
           **-mtf**
               Causes all functions to default to the ".far" section.
               Without this option, functions default to the ".near" section.
    
           **-mtiny=**_n_
               Variables that are _n_ bytes or smaller are allocated to the
               ".tiny" section.  These variables use the $gp base register.
               The default for this option is 4, but note that there's a
               65536-byte limit to the ".tiny" section.
    
           _MicroBlaze Options_
    
           **-msoft-float**
               Use software emulation for floating point (default).
    
           **-mhard-float**
               Use hardware floating-point instructions.
    
           **-mmemcpy**
               Do not optimize block moves, use "memcpy".
    
           **-mno-clearbss**
               This option is deprecated.  Use **-fno-zero-initialized-in-bss**
               instead.
    
           **-mcpu=**_cpu-type_
               Use features of, and schedule code for, the given CPU.
               Supported values are in the format **v** _X_**.**_YY_**.**_Z_ , where _X_ is a major
               version, _YY_ is the minor version, and _Z_ is compatibility code.
               Example values are **v3.00.a** , **v4.00.b** , **v5.00.a** , **v5.00.b** ,
               **v6.00.a**.
    
           **-mxl-soft-mul**
               Use software multiply emulation (default).
    
           **-mxl-soft-div**
               Use software emulation for divides (default).
    
           **-mxl-barrel-shift**
               Use the hardware barrel shifter.
    
           **-mxl-pattern-compare**
               Use pattern compare instructions.
    
           **-msmall-divides**
               Use table lookup optimization for small signed integer
               divisions.
    
           **-mxl-stack-check**
               This option is deprecated.  Use **-fstack-check** instead.
    
           **-mxl-gp-opt**
               Use GP-relative ".sdata"/".sbss" sections.
    
           **-mxl-multiply-high**
               Use multiply high instructions for high part of 32x32
               multiply.
    
           **-mxl-float-convert**
               Use hardware floating-point conversion instructions.
    
           **-mxl-float-sqrt**
               Use hardware floating-point square root instruction.
    
           **-mbig-endian**
               Generate code for a big-endian target.
    
           **-mlittle-endian**
               Generate code for a little-endian target.
    
           **-mxl-reorder**
               Use reorder instructions (swap and byte reversed load/store).
    
           **-mxl-mode-**_app-model_
               Select application model _app-model_.  Valid models are
    
               **executable**
                   normal executable (default), uses startup code _crt0.o_.
    
               **-mpic-data-is-text-relative**
                   Assume that the displacement between the text and data
                   segments is fixed at static link time.  This allows data
                   to be referenced by offset from start of text address
                   instead of GOT since PC-relative addressing is not
                   supported.
    
               **xmdstub**
                   for use with Xilinx Microprocessor Debugger (XMD) based
                   software intrusive debug agent called xmdstub. This uses
                   startup file _crt1.o_ and sets the start address of the
                   program to 0x800.
    
               **bootstrap**
                   for applications that are loaded using a bootloader.  This
                   model uses startup file _crt2.o_ which does not contain a
                   processor reset vector handler. This is suitable for
                   transferring control on a processor reset to the
                   bootloader rather than the application.
    
               **novectors**
                   for applications that do not require any of the MicroBlaze
                   vectors. This option may be useful for applications
                   running within a monitoring application. This model uses
                   _crt3.o_ as a startup file.
    
               Option **-xl-mode-**_app-model_ is a deprecated alias for
               **-mxl-mode-**_app-model_.
    
           _MIPS Options_
    
           **-EB** Generate big-endian code.
    
           **-EL** Generate little-endian code.  This is the default for
               **mips*el-*-*** configurations.
    
           **-march=**_arch_
               Generate code that runs on _arch_ , which can be the name of a
               generic MIPS ISA, or the name of a particular processor.  The
               ISA names are: **mips1** , **mips2** , **mips3** , **mips4** , **mips32** , **mips32r2** ,
               **mips32r3** , **mips32r5** , **mips32r6** , **mips64** , **mips64r2** , **mips64r3** ,
               **mips64r5** and **mips64r6**.  The processor names are: **4kc** , **4km** ,
               **4kp** , **4ksc** , **4kec** , **4kem** , **4kep** , **4ksd** , **5kc** , **5kf** , **20kc** , **24kc** ,
               **24kf2_1** , **24kf1_1** , **24kec** , **24kef2_1** , **24kef1_1** , **34kc** , **34kf2_1** ,
               **34kf1_1** , **34kn** , **74kc** , **74kf2_1** , **74kf1_1** , **74kf3_2** , **1004kc** ,
               **1004kf2_1** , **1004kf1_1** , **i6400** , **i6500** , **interaptiv** , **loongson2e** ,
               **loongson2f** , **loongson3a** , **gs464** , **gs464e** , **gs264e** , **m4k** , **m14k** ,
               **m14kc** , **m14ke** , **m14kec** , **m5100** , **m5101** , **octeon** , **octeon+** , **octeon2** ,
               **octeon3** , **orion** , **p5600** , **p6600** , **r2000** , **r3000** , **r3900** , **r4000** ,
               **r4400** , **r4600** , **r4650** , **r4700** , **r5900** , **r6000** , **r8000** , **rm7000** ,
               **rm9000** , **r10000** , **r12000** , **r14000** , **r16000** , **sb1** , **sr71000** , **vr4100** ,
               **vr4111** , **vr4120** , **vr4130** , **vr4300** , **vr5000** , **vr5400** , **vr5500** , **xlr**
               and **xlp**.  The special value **from-abi** selects the most
               compatible architecture for the selected ABI (that is, **mips1**
               for 32-bit ABIs and **mips3** for 64-bit ABIs).
    
               The native Linux/GNU toolchain also supports the value **native** ,
               which selects the best architecture option for the host
               processor.  **-march=native** has no effect if GCC does not
               recognize the processor.
    
               In processor names, a final **000** can be abbreviated as **k**(for
               example, **-march=r2k**).  Prefixes are optional, and **vr** may be
               written **r**.
    
               Names of the form _n_**f2_1** refer to processors with FPUs clocked
               at half the rate of the core, names of the form _n_**f1_1** refer to
               processors with FPUs clocked at the same rate as the core, and
               names of the form _n_**f3_2** refer to processors with FPUs clocked
               a ratio of 3:2 with respect to the core.  For compatibility
               reasons, _n_**f** is accepted as a synonym for _n_**f2_1** while _n_**x** and
               _b_**fx** are accepted as synonyms for _n_**f1_1**.
    
               GCC defines two macros based on the value of this option.  The
               first is "_MIPS_ARCH", which gives the name of target
               architecture, as a string.  The second has the form
               "_MIPS_ARCH__foo"_ , where _foo_ is the capitalized value of
               "_MIPS_ARCH".  For example, **-march=r2000** sets "_MIPS_ARCH" to
               "r2000" and defines the macro "_MIPS_ARCH_R2000".
    
               Note that the "_MIPS_ARCH" macro uses the processor names
               given above.  In other words, it has the full prefix and does
               not abbreviate **000** as **k**.  In the case of **from-abi** , the macro
               names the resolved architecture (either "mips1" or "mips3").
               It names the default architecture when no **-march** option is
               given.
    
           **-mtune=**_arch_
               Optimize for _arch_.  Among other things, this option controls
               the way instructions are scheduled, and the perceived cost of
               arithmetic operations.  The list of _arch_ values is the same as
               for **-march**.
    
               When this option is not used, GCC optimizes for the processor
               specified by **-march**.  By using **-march** and **-mtune** together, it
               is possible to generate code that runs on a family of
               processors, but optimize the code for one particular member of
               that family.
    
               **-mtune** defines the macros "_MIPS_TUNE" and "_MIPS_TUNE__foo"_ ,
               which work in the same way as the **-march** ones described above.
    
           **-mips1**
               Equivalent to **-march=mips1**.
    
           **-mips2**
               Equivalent to **-march=mips2**.
    
           **-mips3**
               Equivalent to **-march=mips3**.
    
           **-mips4**
               Equivalent to **-march=mips4**.
    
           **-mips32**
               Equivalent to **-march=mips32**.
    
           **-mips32r3**
               Equivalent to **-march=mips32r3**.
    
           **-mips32r5**
               Equivalent to **-march=mips32r5**.
    
           **-mips32r6**
               Equivalent to **-march=mips32r6**.
    
           **-mips64**
               Equivalent to **-march=mips64**.
    
           **-mips64r2**
               Equivalent to **-march=mips64r2**.
    
           **-mips64r3**
               Equivalent to **-march=mips64r3**.
    
           **-mips64r5**
               Equivalent to **-march=mips64r5**.
    
           **-mips64r6**
               Equivalent to **-march=mips64r6**.
    
           **-mips16**
           **-mno-mips16**
               Generate (do not generate) MIPS16 code.  If GCC is targeting a
               MIPS32 or MIPS64 architecture, it makes use of the MIPS16e
               ASE.
    
               MIPS16 code generation can also be controlled on a per-
               function basis by means of "mips16" and "nomips16" attributes.
    
           **-mflip-mips16**
               Generate MIPS16 code on alternating functions.  This option is
               provided for regression testing of mixed MIPS16/non-MIPS16
               code generation, and is not intended for ordinary use in
               compiling user code.
    
           **-minterlink-compressed**
           **-mno-interlink-compressed**
               Require (do not require) that code using the standard
               (uncompressed) MIPS ISA be link-compatible with MIPS16 and
               microMIPS code, and vice versa.
    
               For example, code using the standard ISA encoding cannot jump
               directly to MIPS16 or microMIPS code; it must either use a
               call or an indirect jump.  **-minterlink-compressed** therefore
               disables direct jumps unless GCC knows that the target of the
               jump is not compressed.
    
           **-minterlink-mips16**
           **-mno-interlink-mips16**
               Aliases of **-minterlink-compressed** and
               **-mno-interlink-compressed**.  These options predate the
               microMIPS ASE and are retained for backwards compatibility.
    
           **-mabi=32**
           **-mabi=o64**
           **-mabi=n32**
           **-mabi=64**
           **-mabi=eabi**
               Generate code for the given ABI.
    
               Note that the EABI has a 32-bit and a 64-bit variant.  GCC
               normally generates 64-bit code when you select a 64-bit
               architecture, but you can use **-mgp32** to get 32-bit code
               instead.
    
               For information about the O64 ABI, see
               <**http://gcc.gnu.org/projects/mipso64-abi.html **>.
    
               GCC supports a variant of the o32 ABI in which floating-point
               registers are 64 rather than 32 bits wide.  You can select
               this combination with **-mabi=32 -mfp64**.  This ABI relies on the
               "mthc1" and "mfhc1" instructions and is therefore only
               supported for MIPS32R2, MIPS32R3 and MIPS32R5 processors.
    
               The register assignments for arguments and return values
               remain the same, but each scalar value is passed in a single
               64-bit register rather than a pair of 32-bit registers.  For
               example, scalar floating-point values are returned in **$f0**
               only, not a **$f0** /**$f1** pair.  The set of call-saved registers
               also remains the same in that the even-numbered double-
               precision registers are saved.
    
               Two additional variants of the o32 ABI are supported to enable
               a transition from 32-bit to 64-bit registers.  These are FPXX
               (**-mfpxx**) and FP64A (**-mfp64 -mno-odd-spreg**).  The FPXX
               extension mandates that all code must execute correctly when
               run using 32-bit or 64-bit registers.  The code can be
               interlinked with either FP32 or FP64, but not both.  The FP64A
               extension is similar to the FP64 extension but forbids the use
               of odd-numbered single-precision registers.  This can be used
               in conjunction with the "FRE" mode of FPUs in MIPS32R5
               processors and allows both FP32 and FP64A code to interlink
               and run in the same process without changing FPU modes.
    
           **-mabicalls**
           **-mno-abicalls**
               Generate (do not generate) code that is suitable for
               SVR4-style dynamic objects.  **-mabicalls** is the default for
               SVR4-based systems.
    
           **-mshared**
           **-mno-shared**
               Generate (do not generate) code that is fully position-
               independent, and that can therefore be linked into shared
               libraries.  This option only affects **-mabicalls**.
    
               All **-mabicalls** code has traditionally been position-
               independent, regardless of options like **-fPIC** and **-fpic**.
               However, as an extension, the GNU toolchain allows executables
               to use absolute accesses for locally-binding symbols.  It can
               also use shorter GP initialization sequences and generate
               direct calls to locally-defined functions.  This mode is
               selected by **-mno-shared**.
    
               **-mno-shared** depends on binutils 2.16 or higher and generates
               objects that can only be linked by the GNU linker.  However,
               the option does not affect the ABI of the final executable; it
               only affects the ABI of relocatable objects.  Using
               **-mno-shared** generally makes executables both smaller and
               quicker.
    
               **-mshared** is the default.
    
           **-mplt**
           **-mno-plt**
               Assume (do not assume) that the static and dynamic linkers
               support PLTs and copy relocations.  This option only affects
               **-mno-shared -mabicalls**.  For the n64 ABI, this option has no
               effect without **-msym32**.
    
               You can make **-mplt** the default by configuring GCC with
               **--with-mips-plt**.  The default is **-mno-plt** otherwise.
    
           **-mxgot**
           **-mno-xgot**
               Lift (do not lift) the usual restrictions on the size of the
               global offset table.
    
               GCC normally uses a single instruction to load values from the
               GOT.  While this is relatively efficient, it only works if the
               GOT is smaller than about 64k.  Anything larger causes the
               linker to report an error such as:
    
                       relocation truncated to fit: R_MIPS_GOT16 foobar
    
               If this happens, you should recompile your code with **-mxgot**.
               This works with very large GOTs, although the code is also
               less efficient, since it takes three instructions to fetch the
               value of a global symbol.
    
               Note that some linkers can create multiple GOTs.  If you have
               such a linker, you should only need to use **-mxgot** when a
               single object file accesses more than 64k's worth of GOT
               entries.  Very few do.
    
               These options have no effect unless GCC is generating position
               independent code.
    
           **-mgp32**
               Assume that general-purpose registers are 32 bits wide.
    
           **-mgp64**
               Assume that general-purpose registers are 64 bits wide.
    
           **-mfp32**
               Assume that floating-point registers are 32 bits wide.
    
           **-mfp64**
               Assume that floating-point registers are 64 bits wide.
    
           **-mfpxx**
               Do not assume the width of floating-point registers.
    
           **-mhard-float**
               Use floating-point coprocessor instructions.
    
           **-msoft-float**
               Do not use floating-point coprocessor instructions.  Implement
               floating-point calculations using library calls instead.
    
           **-mno-float**
               Equivalent to **-msoft-float** , but additionally asserts that the
               program being compiled does not perform any floating-point
               operations.  This option is presently supported only by some
               bare-metal MIPS configurations, where it may select a special
               set of libraries that lack all floating-point support
               (including, for example, the floating-point "printf" formats).
               If code compiled with **-mno-float** accidentally contains
               floating-point operations, it is likely to suffer a link-time
               or run-time failure.
    
           **-msingle-float**
               Assume that the floating-point coprocessor only supports
               single-precision operations.
    
           **-mdouble-float**
               Assume that the floating-point coprocessor supports double-
               precision operations.  This is the default.
    
           **-modd-spreg**
           **-mno-odd-spreg**
               Enable the use of odd-numbered single-precision floating-point
               registers for the o32 ABI.  This is the default for processors
               that are known to support these registers.  When using the o32
               FPXX ABI, **-mno-odd-spreg** is set by default.
    
           **-mabs=2008**
           **-mabs=legacy**
               These options control the treatment of the special not-a-
               number (NaN) IEEE 754 floating-point data with the "abs._fmt"_
               and "neg._fmt"_ machine instructions.
    
               By default or when **-mabs=legacy** is used the legacy treatment
               is selected.  In this case these instructions are considered
               arithmetic and avoided where correct operation is required and
               the input operand might be a NaN.  A longer sequence of
               instructions that manipulate the sign bit of floating-point
               datum manually is used instead unless the **-ffinite-math-only**
               option has also been specified.
    
               The **-mabs=2008** option selects the IEEE 754-2008 treatment.  In
               this case these instructions are considered non-arithmetic and
               therefore operating correctly in all cases, including in
               particular where the input operand is a NaN.  These
               instructions are therefore always used for the respective
               operations.
    
           **-mnan=2008**
           **-mnan=legacy**
               These options control the encoding of the special not-a-number
               (NaN) IEEE 754 floating-point data.
    
               The **-mnan=legacy** option selects the legacy encoding.  In this
               case quiet NaNs (qNaNs) are denoted by the first bit of their
               trailing significand field being 0, whereas signaling NaNs
               (sNaNs) are denoted by the first bit of their trailing
               significand field being 1.
    
               The **-mnan=2008** option selects the IEEE 754-2008 encoding.  In
               this case qNaNs are denoted by the first bit of their trailing
               significand field being 1, whereas sNaNs are denoted by the
               first bit of their trailing significand field being 0.
    
               The default is **-mnan=legacy** unless GCC has been configured
               with **--with-nan=2008**.
    
           **-mllsc**
           **-mno-llsc**
               Use (do not use) **ll** , **sc** , and **sync** instructions to implement
               atomic memory built-in functions.  When neither option is
               specified, GCC uses the instructions if the target
               architecture supports them.
    
               **-mllsc** is useful if the runtime environment can emulate the
               instructions and **-mno-llsc** can be useful when compiling for
               nonstandard ISAs.  You can make either option the default by
               configuring GCC with **--with-llsc** and **--without-llsc**
               respectively.  **--with-llsc** is the default for some
               configurations; see the installation documentation for
               details.
    
           **-mdsp**
           **-mno-dsp**
               Use (do not use) revision 1 of the MIPS DSP ASE.
                 This option defines the preprocessor macro "__mips_dsp".  It
               also defines "__mips_dsp_rev" to 1.
    
           **-mdspr2**
           **-mno-dspr2**
               Use (do not use) revision 2 of the MIPS DSP ASE.
                 This option defines the preprocessor macros "__mips_dsp" and
               "__mips_dspr2".  It also defines "__mips_dsp_rev" to 2.
    
           **-msmartmips**
           **-mno-smartmips**
               Use (do not use) the MIPS SmartMIPS ASE.
    
           **-mpaired-single**
           **-mno-paired-single**
               Use (do not use) paired-single floating-point instructions.
                 This option requires hardware floating-point support to be
               enabled.
    
           **-mdmx**
           **-mno-mdmx**
               Use (do not use) MIPS Digital Media Extension instructions.
               This option can only be used when generating 64-bit code and
               requires hardware floating-point support to be enabled.
    
           **-mips3d**
           **-mno-mips3d**
               Use (do not use) the MIPS-3D ASE.  The option **-mips3d** implies
               **-mpaired-single**.
    
           **-mmicromips**
           **-mno-micromips**
               Generate (do not generate) microMIPS code.
    
               MicroMIPS code generation can also be controlled on a per-
               function basis by means of "micromips" and "nomicromips"
               attributes.
    
           **-mmt**
           **-mno-mt**
               Use (do not use) MT Multithreading instructions.
    
           **-mmcu**
           **-mno-mcu**
               Use (do not use) the MIPS MCU ASE instructions.
    
           **-meva**
           **-mno-eva**
               Use (do not use) the MIPS Enhanced Virtual Addressing
               instructions.
    
           **-mvirt**
           **-mno-virt**
               Use (do not use) the MIPS Virtualization (VZ) instructions.
    
           **-mxpa**
           **-mno-xpa**
               Use (do not use) the MIPS eXtended Physical Address (XPA)
               instructions.
    
           **-mcrc**
           **-mno-crc**
               Use (do not use) the MIPS Cyclic Redundancy Check (CRC)
               instructions.
    
           **-mginv**
           **-mno-ginv**
               Use (do not use) the MIPS Global INValidate (GINV)
               instructions.
    
           **-mloongson-mmi**
           **-mno-loongson-mmi**
               Use (do not use) the MIPS Loongson MultiMedia extensions
               Instructions (MMI).
    
           **-mloongson-ext**
           **-mno-loongson-ext**
               Use (do not use) the MIPS Loongson EXTensions (EXT)
               instructions.
    
           **-mloongson-ext2**
           **-mno-loongson-ext2**
               Use (do not use) the MIPS Loongson EXTensions r2 (EXT2)
               instructions.
    
           **-mlong64**
               Force "long" types to be 64 bits wide.  See **-mlong32** for an
               explanation of the default and the way that the pointer size
               is determined.
    
           **-mlong32**
               Force "long", "int", and pointer types to be 32 bits wide.
    
               The default size of "int"s, "long"s and pointers depends on
               the ABI.  All the supported ABIs use 32-bit "int"s.  The n64
               ABI uses 64-bit "long"s, as does the 64-bit EABI; the others
               use 32-bit "long"s.  Pointers are the same size as "long"s, or
               the same size as integer registers, whichever is smaller.
    
           **-msym32**
           **-mno-sym32**
               Assume (do not assume) that all symbols have 32-bit values,
               regardless of the selected ABI.  This option is useful in
               combination with **-mabi=64** and **-mno-abicalls** because it allows
               GCC to generate shorter and faster references to symbolic
               addresses.
    
           **-G** _num_
               Put definitions of externally-visible data in a small data
               section if that data is no bigger than _num_ bytes.  GCC can
               then generate more efficient accesses to the data; see **-mgpopt**
               for details.
    
               The default **-G** option depends on the configuration.
    
           **-mlocal-sdata**
           **-mno-local-sdata**
               Extend (do not extend) the **-G** behavior to local data too, such
               as to static variables in C.  **-mlocal-sdata** is the default for
               all configurations.
    
               If the linker complains that an application is using too much
               small data, you might want to try rebuilding the less
               performance-critical parts with **-mno-local-sdata**.  You might
               also want to build large libraries with **-mno-local-sdata** , so
               that the libraries leave more room for the main program.
    
           **-mextern-sdata**
           **-mno-extern-sdata**
               Assume (do not assume) that externally-defined data is in a
               small data section if the size of that data is within the **-G**
               limit.  **-mextern-sdata** is the default for all configurations.
    
               If you compile a module _Mod_ with **-mextern-sdata -G** _num_
               **-mgpopt** , and _Mod_ references a variable _Var_ that is no bigger
               than _num_ bytes, you must make sure that _Var_ is placed in a
               small data section.  If _Var_ is defined by another module, you
               must either compile that module with a high-enough **-G** setting
               or attach a "section" attribute to _Var_ 's definition.  If _Var_
               is common, you must link the application with a high-enough **-G**
               setting.
    
               The easiest way of satisfying these restrictions is to compile
               and link every module with the same **-G** option.  However, you
               may wish to build a library that supports several different
               small data limits.  You can do this by compiling the library
               with the highest supported **-G** setting and additionally using
               **-mno-extern-sdata** to stop the library from making assumptions
               about externally-defined data.
    
           **-mgpopt**
           **-mno-gpopt**
               Use (do not use) GP-relative accesses for symbols that are
               known to be in a small data section; see **-G** , **-mlocal-sdata** and
               **-mextern-sdata**.  **-mgpopt** is the default for all
               configurations.
    
               **-mno-gpopt** is useful for cases where the $gp register might
               not hold the value of "_gp".  For example, if the code is part
               of a library that might be used in a boot monitor, programs
               that call boot monitor routines pass an unknown value in $gp.
               (In such situations, the boot monitor itself is usually
               compiled with **-G0**.)
    
               **-mno-gpopt** implies **-mno-local-sdata** and **-mno-extern-sdata**.
    
           **-membedded-data**
           **-mno-embedded-data**
               Allocate variables to the read-only data section first if
               possible, then next in the small data section if possible,
               otherwise in data.  This gives slightly slower code than the
               default, but reduces the amount of RAM required when
               executing, and thus may be preferred for some embedded
               systems.
    
           **-muninit-const-in-rodata**
           **-mno-uninit-const-in-rodata**
               Put uninitialized "const" variables in the read-only data
               section.  This option is only meaningful in conjunction with
               **-membedded-data**.
    
           **-mcode-readable=**_setting_
               Specify whether GCC may generate code that reads from
               executable sections.  There are three possible settings:
    
               **-mcode-readable=yes**
                   Instructions may freely access executable sections.  This
                   is the default setting.
    
               **-mcode-readable=pcrel**
                   MIPS16 PC-relative load instructions can access executable
                   sections, but other instructions must not do so.  This
                   option is useful on 4KSc and 4KSd processors when the code
                   TLBs have the Read Inhibit bit set.  It is also useful on
                   processors that can be configured to have a dual
                   instruction/data SRAM interface and that, like the M4K,
                   automatically redirect PC-relative loads to the
                   instruction RAM.
    
               **-mcode-readable=no**
                   Instructions must not access executable sections.  This
                   option can be useful on targets that are configured to
                   have a dual instruction/data SRAM interface but that
                   (unlike the M4K) do not automatically redirect PC-relative
                   loads to the instruction RAM.
    
           **-msplit-addresses**
           **-mno-split-addresses**
               Enable (disable) use of the "%hi()" and "%lo()" assembler
               relocation operators.  This option has been superseded by
               **-mexplicit-relocs** but is retained for backwards compatibility.
    
           **-mexplicit-relocs**
           **-mno-explicit-relocs**
               Use (do not use) assembler relocation operators when dealing
               with symbolic addresses.  The alternative, selected by
               **-mno-explicit-relocs** , is to use assembler macros instead.
    
               **-mexplicit-relocs** is the default if GCC was configured to use
               an assembler that supports relocation operators.
    
           **-mcheck-zero-division**
           **-mno-check-zero-division**
               Trap (do not trap) on integer division by zero.
    
               The default is **-mcheck-zero-division**.
    
           **-mdivide-traps**
           **-mdivide-breaks**
               MIPS systems check for division by zero by generating either a
               conditional trap or a break instruction.  Using traps results
               in smaller code, but is only supported on MIPS II and later.
               Also, some versions of the Linux kernel have a bug that
               prevents trap from generating the proper signal ("SIGFPE").
               Use **-mdivide-traps** to allow conditional traps on architectures
               that support them and **-mdivide-breaks** to force the use of
               breaks.
    
               The default is usually **-mdivide-traps** , but this can be
               overridden at configure time using **--with-divide=breaks**.
               Divide-by-zero checks can be completely disabled using
               **-mno-check-zero-division**.
    
           **-mload-store-pairs**
           **-mno-load-store-pairs**
               Enable (disable) an optimization that pairs consecutive load
               or store instructions to enable load/store bonding.  This
               option is enabled by default but only takes effect when the
               selected architecture is known to support bonding.
    
           **-mmemcpy**
           **-mno-memcpy**
               Force (do not force) the use of "memcpy" for non-trivial block
               moves.  The default is **-mno-memcpy** , which allows GCC to inline
               most constant-sized copies.
    
           **-mlong-calls**
           **-mno-long-calls**
               Disable (do not disable) use of the "jal" instruction.
               Calling functions using "jal" is more efficient but requires
               the caller and callee to be in the same 256 megabyte segment.
    
               This option has no effect on abicalls code.  The default is
               **-mno-long-calls**.
    
           **-mmad**
           **-mno-mad**
               Enable (disable) use of the "mad", "madu" and "mul"
               instructions, as provided by the R4650 ISA.
    
           **-mimadd**
           **-mno-imadd**
               Enable (disable) use of the "madd" and "msub" integer
               instructions.  The default is **-mimadd** on architectures that
               support "madd" and "msub" except for the 74k architecture
               where it was found to generate slower code.
    
           **-mfused-madd**
           **-mno-fused-madd**
               Enable (disable) use of the floating-point multiply-accumulate
               instructions, when they are available.  The default is
               **-mfused-madd**.
    
               On the R8000 CPU when multiply-accumulate instructions are
               used, the intermediate product is calculated to infinite
               precision and is not subject to the FCSR Flush to Zero bit.
               This may be undesirable in some circumstances.  On other
               processors the result is numerically identical to the
               equivalent computation using separate multiply, add, subtract
               and negate instructions.
    
           **-nocpp**
               Tell the MIPS assembler to not run its preprocessor over user
               assembler files (with a **.s** suffix) when assembling them.
    
           **-mfix-24k**
           **-mno-fix-24k**
               Work around the 24K E48 (lost data on stores during refill)
               errata.  The workarounds are implemented by the assembler
               rather than by GCC.
    
           **-mfix-r4000**
           **-mno-fix-r4000**
               Work around certain R4000 CPU errata:
    
               -   A double-word or a variable shift may give an incorrect
                   result if executed immediately after starting an integer
                   division.
    
               -   A double-word or a variable shift may give an incorrect
                   result if executed while an integer multiplication is in
                   progress.
    
               -   An integer division may give an incorrect result if
                   started in a delay slot of a taken branch or a jump.
    
           **-mfix-r4400**
           **-mno-fix-r4400**
               Work around certain R4400 CPU errata:
    
               -   A double-word or a variable shift may give an incorrect
                   result if executed immediately after starting an integer
                   division.
    
           **-mfix-r10000**
           **-mno-fix-r10000**
               Work around certain R10000 errata:
    
               -   "ll"/"sc" sequences may not behave atomically on revisions
                   prior to 3.0.  They may deadlock on revisions 2.6 and
                   earlier.
    
               This option can only be used if the target architecture
               supports branch-likely instructions.  **-mfix-r10000** is the
               default when **-march=r10000** is used; **-mno-fix-r10000** is the
               default otherwise.
    
           **-mfix-r5900**
           **-mno-fix-r5900**
               Do not attempt to schedule the preceding instruction into the
               delay slot of a branch instruction placed at the end of a
               short loop of six instructions or fewer and always schedule a
               "nop" instruction there instead.  The short loop bug under
               certain conditions causes loops to execute only once or twice,
               due to a hardware bug in the R5900 chip.  The workaround is
               implemented by the assembler rather than by GCC.
    
           **-mfix-rm7000**
           **-mno-fix-rm7000**
               Work around the RM7000 "dmult"/"dmultu" errata.  The
               workarounds are implemented by the assembler rather than by
               GCC.
    
           **-mfix-vr4120**
           **-mno-fix-vr4120**
               Work around certain VR4120 errata:
    
               -   "dmultu" does not always produce the correct result.
    
               -   "div" and "ddiv" do not always produce the correct result
                   if one of the operands is negative.
    
               The workarounds for the division errata rely on special
               functions in _libgcc.a_.  At present, these functions are only
               provided by the "mips64vr*-elf" configurations.
    
               Other VR4120 errata require a NOP to be inserted between
               certain pairs of instructions.  These errata are handled by
               the assembler, not by GCC itself.
    
           **-mfix-vr4130**
               Work around the VR4130 "mflo"/"mfhi" errata.  The workarounds
               are implemented by the assembler rather than by GCC, although
               GCC avoids using "mflo" and "mfhi" if the VR4130 "macc",
               "macchi", "dmacc" and "dmacchi" instructions are available
               instead.
    
           **-mfix-sb1**
           **-mno-fix-sb1**
               Work around certain SB-1 CPU core errata.  (This flag
               currently works around the SB-1 revision 2 "F1" and "F2"
               floating-point errata.)
    
           **-mr10k-cache-barrier=**_setting_
               Specify whether GCC should insert cache barriers to avoid the
               side effects of speculation on R10K processors.
    
               In common with many processors, the R10K tries to predict the
               outcome of a conditional branch and speculatively executes
               instructions from the "taken" branch.  It later aborts these
               instructions if the predicted outcome is wrong.  However, on
               the R10K, even aborted instructions can have side effects.
    
               This problem only affects kernel stores and, depending on the
               system, kernel loads.  As an example, a speculatively-executed
               store may load the target memory into cache and mark the cache
               line as dirty, even if the store itself is later aborted.  If
               a DMA operation writes to the same area of memory before the
               "dirty" line is flushed, the cached data overwrites the DMA-ed
               data.  See the R10K processor manual for a full description,
               including other potential problems.
    
               One workaround is to insert cache barrier instructions before
               every memory access that might be speculatively executed and
               that might have side effects even if aborted.
               **-mr10k-cache-barrier=**_setting_ controls GCC's implementation of
               this workaround.  It assumes that aborted accesses to any byte
               in the following regions does not have side effects:
    
               1.  the memory occupied by the current function's stack frame;
    
               2.  the memory occupied by an incoming stack argument;
    
               3.  the memory occupied by an object with a link-time-constant
                   address.
    
               It is the kernel's responsibility to ensure that speculative
               accesses to these regions are indeed safe.
    
               If the input program contains a function declaration such as:
    
                       void foo (void);
    
               then the implementation of "foo" must allow "j foo" and "jal
               foo" to be executed speculatively.  GCC honors this
               restriction for functions it compiles itself.  It expects non-
               GCC functions (such as hand-written assembly code) to do the
               same.
    
               The option has three forms:
    
               **-mr10k-cache-barrier=load-store**
                   Insert a cache barrier before a load or store that might
                   be speculatively executed and that might have side effects
                   even if aborted.
    
               **-mr10k-cache-barrier=store**
                   Insert a cache barrier before a store that might be
                   speculatively executed and that might have side effects
                   even if aborted.
    
               **-mr10k-cache-barrier=none**
                   Disable the insertion of cache barriers.  This is the
                   default setting.
    
           **-mflush-func=**_func_
           **-mno-flush-func**
               Specifies the function to call to flush the I and D caches, or
               to not call any such function.  If called, the function must
               take the same arguments as the common "_flush_func", that is,
               the address of the memory range for which the cache is being
               flushed, the size of the memory range, and the number 3 (to
               flush both caches).  The default depends on the target GCC was
               configured for, but commonly is either "_flush_func" or
               "__cpu_flush".
    
           **mbranch-cost=**_num_
               Set the cost of branches to roughly _num_ "simple" instructions.
               This cost is only a heuristic and is not guaranteed to produce
               consistent results across releases.  A zero cost redundantly
               selects the default, which is based on the **-mtune** setting.
    
           **-mbranch-likely**
           **-mno-branch-likely**
               Enable or disable use of Branch Likely instructions,
               regardless of the default for the selected architecture.  By
               default, Branch Likely instructions may be generated if they
               are supported by the selected architecture.  An exception is
               for the MIPS32 and MIPS64 architectures and processors that
               implement those architectures; for those, Branch Likely
               instructions are not be generated by default because the
               MIPS32 and MIPS64 architectures specifically deprecate their
               use.
    
           **-mcompact-branches=never**
           **-mcompact-branches=optimal**
           **-mcompact-branches=always**
               These options control which form of branches will be
               generated.  The default is **-mcompact-branches=optimal**.
    
               The **-mcompact-branches=never** option ensures that compact
               branch instructions will never be generated.
    
               The **-mcompact-branches=always** option ensures that a compact
               branch instruction will be generated if available.  If a
               compact branch instruction is not available, a delay slot form
               of the branch will be used instead.
    
               This option is supported from MIPS Release 6 onwards.
    
               The **-mcompact-branches=optimal** option will cause a delay slot
               branch to be used if one is available in the current ISA and
               the delay slot is successfully filled.  If the delay slot is
               not filled, a compact branch will be chosen if one is
               available.
    
           **-mfp-exceptions**
           **-mno-fp-exceptions**
               Specifies whether FP exceptions are enabled.  This affects how
               FP instructions are scheduled for some processors.  The
               default is that FP exceptions are enabled.
    
               For instance, on the SB-1, if FP exceptions are disabled, and
               we are emitting 64-bit code, then we can use both FP pipes.
               Otherwise, we can only use one FP pipe.
    
           **-mvr4130-align**
           **-mno-vr4130-align**
               The VR4130 pipeline is two-way superscalar, but can only issue
               two instructions together if the first one is 8-byte aligned.
               When this option is enabled, GCC aligns pairs of instructions
               that it thinks should execute in parallel.
    
               This option only has an effect when optimizing for the VR4130.
               It normally makes code faster, but at the expense of making it
               bigger.  It is enabled by default at optimization level **-O3**.
    
           **-msynci**
           **-mno-synci**
               Enable (disable) generation of "synci" instructions on
               architectures that support it.  The "synci" instructions (if
               enabled) are generated when "__builtin___clear_cache" is
               compiled.
    
               This option defaults to **-mno-synci** , but the default can be
               overridden by configuring GCC with **--with-synci**.
    
               When compiling code for single processor systems, it is
               generally safe to use "synci".  However, on many multi-core
               (SMP) systems, it does not invalidate the instruction caches
               on all cores and may lead to undefined behavior.
    
           **-mrelax-pic-calls**
           **-mno-relax-pic-calls**
               Try to turn PIC calls that are normally dispatched via
               register $25 into direct calls.  This is only possible if the
               linker can resolve the destination at link time and if the
               destination is within range for a direct call.
    
               **-mrelax-pic-calls** is the default if GCC was configured to use
               an assembler and a linker that support the ".reloc" assembly
               directive and **-mexplicit-relocs** is in effect.  With
               **-mno-explicit-relocs** , this optimization can be performed by
               the assembler and the linker alone without help from the
               compiler.
    
           **-mmcount-ra-address**
           **-mno-mcount-ra-address**
               Emit (do not emit) code that allows "_mcount" to modify the
               calling function's return address.  When enabled, this option
               extends the usual "_mcount" interface with a new _ra-address_
               parameter, which has type "intptr_t *" and is passed in
               register $12.  "_mcount" can then modify the return address by
               doing both of the following:
    
               *   Returning the new address in register $31.
    
               *   Storing the new address in "*_ra-address"_ , if _ra-address_ is
                   nonnull.
    
               The default is **-mno-mcount-ra-address**.
    
           **-mframe-header-opt**
           **-mno-frame-header-opt**
               Enable (disable) frame header optimization in the o32 ABI.
               When using the o32 ABI, calling functions will allocate 16
               bytes on the stack for the called function to write out
               register arguments.  When enabled, this optimization will
               suppress the allocation of the frame header if it can be
               determined that it is unused.
    
               This optimization is off by default at all optimization
               levels.
    
           **-mlxc1-sxc1**
           **-mno-lxc1-sxc1**
               When applicable, enable (disable) the generation of "lwxc1",
               "swxc1", "ldxc1", "sdxc1" instructions.  Enabled by default.
    
           **-mmadd4**
           **-mno-madd4**
               When applicable, enable (disable) the generation of 4-operand
               "madd.s", "madd.d" and related instructions.  Enabled by
               default.
    
           _MMIX Options_
    
           These options are defined for the MMIX:
    
           **-mlibfuncs**
           **-mno-libfuncs**
               Specify that intrinsic library functions are being compiled,
               passing all values in registers, no matter the size.
    
           **-mepsilon**
           **-mno-epsilon**
               Generate floating-point comparison instructions that compare
               with respect to the "rE" epsilon register.
    
           **-mabi=mmixware**
           **-mabi=gnu**
               Generate code that passes function parameters and return
               values that (in the called function) are seen as registers $0
               and up, as opposed to the GNU ABI which uses global registers
               $231 and up.
    
           **-mzero-extend**
           **-mno-zero-extend**
               When reading data from memory in sizes shorter than 64 bits,
               use (do not use) zero-extending load instructions by default,
               rather than sign-extending ones.
    
           **-mknuthdiv**
           **-mno-knuthdiv**
               Make the result of a division yielding a remainder have the
               same sign as the divisor.  With the default, **-mno-knuthdiv** ,
               the sign of the remainder follows the sign of the dividend.
               Both methods are arithmetically valid, the latter being almost
               exclusively used.
    
           **-mtoplevel-symbols**
           **-mno-toplevel-symbols**
               Prepend (do not prepend) a **:** to all global symbols, so the
               assembly code can be used with the "PREFIX" assembly
               directive.
    
           **-melf**
               Generate an executable in the ELF format, rather than the
               default **mmo** format used by the **mmix** simulator.
    
           **-mbranch-predict**
           **-mno-branch-predict**
               Use (do not use) the probable-branch instructions, when static
               branch prediction indicates a probable branch.
    
           **-mbase-addresses**
           **-mno-base-addresses**
               Generate (do not generate) code that uses _base addresses_.
               Using a base address automatically generates a request
               (handled by the assembler and the linker) for a constant to be
               set up in a global register.  The register is used for one or
               more base address requests within the range 0 to 255 from the
               value held in the register.  The generally leads to short and
               fast code, but the number of different data items that can be
               addressed is limited.  This means that a program that uses
               lots of static data may require **-mno-base-addresses**.
    
           **-msingle-exit**
           **-mno-single-exit**
               Force (do not force) generated code to have a single exit
               point in each function.
    
           _MN10300 Options_
    
           These **-m** options are defined for Matsushita MN10300 architectures:
    
           **-mmult-bug**
               Generate code to avoid bugs in the multiply instructions for
               the MN10300 processors.  This is the default.
    
           **-mno-mult-bug**
               Do not generate code to avoid bugs in the multiply
               instructions for the MN10300 processors.
    
           **-mam33**
               Generate code using features specific to the AM33 processor.
    
           **-mno-am33**
               Do not generate code using features specific to the AM33
               processor.  This is the default.
    
           **-mam33-2**
               Generate code using features specific to the AM33/2.0
               processor.
    
           **-mam34**
               Generate code using features specific to the AM34 processor.
    
           **-mtune=**_cpu-type_
               Use the timing characteristics of the indicated CPU type when
               scheduling instructions.  This does not change the targeted
               processor type.  The CPU type must be one of **mn10300** , **am33** ,
               **am33-2** or **am34**.
    
           **-mreturn-pointer-on-d0**
               When generating a function that returns a pointer, return the
               pointer in both "a0" and "d0".  Otherwise, the pointer is
               returned only in "a0", and attempts to call such functions
               without a prototype result in errors.  Note that this option
               is on by default; use **-mno-return-pointer-on-d0** to disable it.
    
           **-mno-crt0**
               Do not link in the C run-time initialization object file.
    
           **-mrelax**
               Indicate to the linker that it should perform a relaxation
               optimization pass to shorten branches, calls and absolute
               memory addresses.  This option only has an effect when used on
               the command line for the final link step.
    
               This option makes symbolic debugging impossible.
    
           **-mliw**
               Allow the compiler to generate _Long Instruction Word_
               instructions if the target is the **AM33** or later.  This is the
               default.  This option defines the preprocessor macro
               "__LIW__".
    
           **-mno-liw**
               Do not allow the compiler to generate _Long Instruction Word_
               instructions.  This option defines the preprocessor macro
               "__NO_LIW__".
    
           **-msetlb**
               Allow the compiler to generate the _SETLB_ and _Lcc_ instructions
               if the target is the **AM33** or later.  This is the default.
               This option defines the preprocessor macro "__SETLB__".
    
           **-mno-setlb**
               Do not allow the compiler to generate _SETLB_ or _Lcc_
               instructions.  This option defines the preprocessor macro
               "__NO_SETLB__".
    
           _Moxie Options_
    
           **-meb**
               Generate big-endian code.  This is the default for **moxie-*-***
               configurations.
    
           **-mel**
               Generate little-endian code.
    
           **-mmul.x**
               Generate mul.x and umul.x instructions.  This is the default
               for **moxiebox-*-*** configurations.
    
           **-mno-crt0**
               Do not link in the C run-time initialization object file.
    
           _MSP430 Options_
    
           These options are defined for the MSP430:
    
           **-masm-hex**
               Force assembly output to always use hex constants.  Normally
               such constants are signed decimals, but this option is
               available for testsuite and/or aesthetic purposes.
    
           **-mmcu=**
               Select the MCU to target.  This is used to create a C
               preprocessor symbol based upon the MCU name, converted to
               upper case and pre- and post-fixed with **__**.  This in turn is
               used by the _msp430.h_ header file to select an MCU-specific
               supplementary header file.
    
               The option also sets the ISA to use.  If the MCU name is one
               that is known to only support the 430 ISA then that is
               selected, otherwise the 430X ISA is selected.  A generic MCU
               name of **msp430** can also be used to select the 430 ISA.
               Similarly the generic **msp430x** MCU name selects the 430X ISA.
    
               In addition an MCU-specific linker script is added to the
               linker command line.  The script's name is the name of the MCU
               with _.ld_ appended.  Thus specifying **-mmcu=xxx** on the **gcc**
               command line defines the C preprocessor symbol "__XXX__" and
               cause the linker to search for a script called _xxx.ld_.
    
               This option is also passed on to the assembler.
    
           **-mwarn-mcu**
           **-mno-warn-mcu**
               This option enables or disables warnings about conflicts
               between the MCU name specified by the **-mmcu** option and the ISA
               set by the **-mcpu** option and/or the hardware multiply support
               set by the **-mhwmult** option.  It also toggles warnings about
               unrecognized MCU names.  This option is on by default.
    
           **-mcpu=**
               Specifies the ISA to use.  Accepted values are **msp430** , **msp430x**
               and **msp430xv2**.  This option is deprecated.  The **-mmcu=** option
               should be used to select the ISA.
    
           **-msim**
               Link to the simulator runtime libraries and linker script.
               Overrides any scripts that would be selected by the **-mmcu=**
               option.
    
           **-mlarge**
               Use large-model addressing (20-bit pointers, 32-bit "size_t").
    
           **-msmall**
               Use small-model addressing (16-bit pointers, 16-bit "size_t").
    
           **-mrelax**
               This option is passed to the assembler and linker, and allows
               the linker to perform certain optimizations that cannot be
               done until the final link.
    
           **mhwmult=**
               Describes the type of hardware multiply supported by the
               target.  Accepted values are **none** for no hardware multiply,
               **16bit** for the original 16-bit-only multiply supported by early
               MCUs.  **32bit** for the 16/32-bit multiply supported by later
               MCUs and **f5series** for the 16/32-bit multiply supported by
               F5-series MCUs.  A value of **auto** can also be given.  This
               tells GCC to deduce the hardware multiply support based upon
               the MCU name provided by the **-mmcu** option.  If no **-mmcu** option
               is specified or if the MCU name is not recognized then no
               hardware multiply support is assumed.  "auto" is the default
               setting.
    
               Hardware multiplies are normally performed by calling a
               library routine.  This saves space in the generated code.
               When compiling at **-O3** or higher however the hardware
               multiplier is invoked inline.  This makes for bigger, but
               faster code.
    
               The hardware multiply routines disable interrupts whilst
               running and restore the previous interrupt state when they
               finish.  This makes them safe to use inside interrupt handlers
               as well as in normal code.
    
           **-minrt**
               Enable the use of a minimum runtime environment - no static
               initializers or constructors.  This is intended for memory-
               constrained devices.  The compiler includes special symbols in
               some objects that tell the linker and runtime which code
               fragments are required.
    
           **-mcode-region=**
           **-mdata-region=**
               These options tell the compiler where to place functions and
               data that do not have one of the "lower", "upper", "either" or
               "section" attributes.  Possible values are "lower", "upper",
               "either" or "any".  The first three behave like the
               corresponding attribute.  The fourth possible value - "any" -
               is the default.  It leaves placement entirely up to the linker
               script and how it assigns the standard sections (".text",
               ".data", etc) to the memory regions.
    
           **-msilicon-errata=**
               This option passes on a request to assembler to enable the
               fixes for the named silicon errata.
    
           **-msilicon-errata-warn=**
               This option passes on a request to the assembler to enable
               warning messages when a silicon errata might need to be
               applied.
    
           _NDS32 Options_
    
           These options are defined for NDS32 implementations:
    
           **-mbig-endian**
               Generate code in big-endian mode.
    
           **-mlittle-endian**
               Generate code in little-endian mode.
    
           **-mreduced-regs**
               Use reduced-set registers for register allocation.
    
           **-mfull-regs**
               Use full-set registers for register allocation.
    
           **-mcmov**
               Generate conditional move instructions.
    
           **-mno-cmov**
               Do not generate conditional move instructions.
    
           **-mext-perf**
               Generate performance extension instructions.
    
           **-mno-ext-perf**
               Do not generate performance extension instructions.
    
           **-mext-perf2**
               Generate performance extension 2 instructions.
    
           **-mno-ext-perf2**
               Do not generate performance extension 2 instructions.
    
           **-mext-string**
               Generate string extension instructions.
    
           **-mno-ext-string**
               Do not generate string extension instructions.
    
           **-mv3push**
               Generate v3 push25/pop25 instructions.
    
           **-mno-v3push**
               Do not generate v3 push25/pop25 instructions.
    
           **-m16-bit**
               Generate 16-bit instructions.
    
           **-mno-16-bit**
               Do not generate 16-bit instructions.
    
           **-misr-vector-size=**_num_
               Specify the size of each interrupt vector, which must be 4 or
               16.
    
           **-mcache-block-size=**_num_
               Specify the size of each cache block, which must be a power of
               2 between 4 and 512.
    
           **-march=**_arch_
               Specify the name of the target architecture.
    
           **-mcmodel=**_code-model_
               Set the code model to one of
    
               **small**
                   All the data and read-only data segments must be within
                   512KB addressing space.  The text segment must be within
                   16MB addressing space.
    
               **medium**
                   The data segment must be within 512KB while the read-only
                   data segment can be within 4GB addressing space.  The text
                   segment should be still within 16MB addressing space.
    
               **large**
                   All the text and data segments can be within 4GB
                   addressing space.
    
           **-mctor-dtor**
               Enable constructor/destructor feature.
    
           **-mrelax**
               Guide linker to relax instructions.
    
           _Nios II Options_
    
           These are the options defined for the Altera Nios II processor.
    
           **-G** _num_
               Put global and static objects less than or equal to _num_ bytes
               into the small data or BSS sections instead of the normal data
               or BSS sections.  The default value of _num_ is 8.
    
           **-mgpopt=**_option_
           **-mgpopt**
           **-mno-gpopt**
               Generate (do not generate) GP-relative accesses.  The
               following _option_ names are recognized:
    
               **none**
                   Do not generate GP-relative accesses.
    
               **local**
                   Generate GP-relative accesses for small data objects that
                   are not external, weak, or uninitialized common symbols.
                   Also use GP-relative addressing for objects that have been
                   explicitly placed in a small data section via a "section"
                   attribute.
    
               **global**
                   As for **local** , but also generate GP-relative accesses for
                   small data objects that are external, weak, or common.  If
                   you use this option, you must ensure that all parts of
                   your program (including libraries) are compiled with the
                   same **-G** setting.
    
               **data**
                   Generate GP-relative accesses for all data objects in the
                   program.  If you use this option, the entire data and BSS
                   segments of your program must fit in 64K of memory and you
                   must use an appropriate linker script to allocate them
                   within the addressable range of the global pointer.
    
               **all** Generate GP-relative addresses for function pointers as
                   well as data pointers.  If you use this option, the entire
                   text, data, and BSS segments of your program must fit in
                   64K of memory and you must use an appropriate linker
                   script to allocate them within the addressable range of
                   the global pointer.
    
               **-mgpopt** is equivalent to **-mgpopt=local** , and **-mno-gpopt** is
               equivalent to **-mgpopt=none**.
    
               The default is **-mgpopt** except when **-fpic** or **-fPIC** is specified
               to generate position-independent code.  Note that the Nios II
               ABI does not permit GP-relative accesses from shared
               libraries.
    
               You may need to specify **-mno-gpopt** explicitly when building
               programs that include large amounts of small data, including
               large GOT data sections.  In this case, the 16-bit offset for
               GP-relative addressing may not be large enough to allow access
               to the entire small data section.
    
           **-mgprel-sec=**_regexp_
               This option specifies additional section names that can be
               accessed via GP-relative addressing.  It is most useful in
               conjunction with "section" attributes on variable declarations
               and a custom linker script.  The _regexp_ is a POSIX Extended
               Regular Expression.
    
               This option does not affect the behavior of the **-G** option, and
               the specified sections are in addition to the standard
               ".sdata" and ".sbss" small-data sections that are recognized
               by **-mgpopt**.
    
           **-mr0rel-sec=**_regexp_
               This option specifies names of sections that can be accessed
               via a 16-bit offset from "r0"; that is, in the low 32K or high
               32K of the 32-bit address space.  It is most useful in
               conjunction with "section" attributes on variable declarations
               and a custom linker script.  The _regexp_ is a POSIX Extended
               Regular Expression.
    
               In contrast to the use of GP-relative addressing for small
               data, zero-based addressing is never generated by default and
               there are no conventional section names used in standard
               linker scripts for sections in the low or high areas of
               memory.
    
           **-mel**
           **-meb**
               Generate little-endian (default) or big-endian (experimental)
               code, respectively.
    
           **-march=**_arch_
               This specifies the name of the target Nios II architecture.
               GCC uses this name to determine what kind of instructions it
               can emit when generating assembly code.  Permissible names
               are: **r1** , **r2**.
    
               The preprocessor macro "__nios2_arch__" is available to
               programs, with value 1 or 2, indicating the targeted ISA
               level.
    
           **-mbypass-cache**
           **-mno-bypass-cache**
               Force all load and store instructions to always bypass cache
               by using I/O variants of the instructions. The default is not
               to bypass the cache.
    
           **-mno-cache-volatile**
           **-mcache-volatile**
               Volatile memory access bypass the cache using the I/O variants
               of the load and store instructions. The default is not to
               bypass the cache.
    
           **-mno-fast-sw-div**
           **-mfast-sw-div**
               Do not use table-based fast divide for small numbers. The
               default is to use the fast divide at **-O3** and above.
    
           **-mno-hw-mul**
           **-mhw-mul**
           **-mno-hw-mulx**
           **-mhw-mulx**
           **-mno-hw-div**
           **-mhw-div**
               Enable or disable emitting "mul", "mulx" and "div" family of
               instructions by the compiler. The default is to emit "mul" and
               not emit "div" and "mulx".
    
           **-mbmx**
           **-mno-bmx**
           **-mcdx**
           **-mno-cdx**
               Enable or disable generation of Nios II R2 BMX (bit
               manipulation) and CDX (code density) instructions.  Enabling
               these instructions also requires **-march=r2**.  Since these
               instructions are optional extensions to the R2 architecture,
               the default is not to emit them.
    
           **-mcustom-**_insn_**=**_N_
           **-mno-custom-**_insn_
               Each **-mcustom-**_insn_**=**_N_ option enables use of a custom
               instruction with encoding _N_ when generating code that uses
               _insn_.  For example, **-mcustom-fadds=253** generates custom
               instruction 253 for single-precision floating-point add
               operations instead of the default behavior of using a library
               call.
    
               The following values of _insn_ are supported.  Except as
               otherwise noted, floating-point operations are expected to be
               implemented with normal IEEE 754 semantics and correspond
               directly to the C operators or the equivalent GCC built-in
               functions.
    
               Single-precision floating point:
    
               **fadds** , **fsubs** , **fdivs** , **fmuls**
                   Binary arithmetic operations.
    
               **fnegs**
                   Unary negation.
    
               **fabss**
                   Unary absolute value.
    
               **fcmpeqs** , **fcmpges** , **fcmpgts** , **fcmples** , **fcmplts** , **fcmpnes**
                   Comparison operations.
    
               **fmins** , **fmaxs**
                   Floating-point minimum and maximum.  These instructions
                   are only generated if **-ffinite-math-only** is specified.
    
               **fsqrts**
                   Unary square root operation.
    
               **fcoss** , **fsins** , **ftans** , **fatans** , **fexps** , **flogs**
                   Floating-point trigonometric and exponential functions.
                   These instructions are only generated if
                   **-funsafe-math-optimizations** is also specified.
    
               Double-precision floating point:
    
               **faddd** , **fsubd** , **fdivd** , **fmuld**
                   Binary arithmetic operations.
    
               **fnegd**
                   Unary negation.
    
               **fabsd**
                   Unary absolute value.
    
               **fcmpeqd** , **fcmpged** , **fcmpgtd** , **fcmpled** , **fcmpltd** , **fcmpned**
                   Comparison operations.
    
               **fmind** , **fmaxd**
                   Double-precision minimum and maximum.  These instructions
                   are only generated if **-ffinite-math-only** is specified.
    
               **fsqrtd**
                   Unary square root operation.
    
               **fcosd** , **fsind** , **ftand** , **fatand** , **fexpd** , **flogd**
                   Double-precision trigonometric and exponential functions.
                   These instructions are only generated if
                   **-funsafe-math-optimizations** is also specified.
    
               Conversions:
    
               **fextsd**
                   Conversion from single precision to double precision.
    
               **ftruncds**
                   Conversion from double precision to single precision.
    
               **fixsi** , **fixsu** , **fixdi** , **fixdu**
                   Conversion from floating point to signed or unsigned
                   integer types, with truncation towards zero.
    
               **round**
                   Conversion from single-precision floating point to signed
                   integer, rounding to the nearest integer and ties away
                   from zero.  This corresponds to the "__builtin_lroundf"
                   function when **-fno-math-errno** is used.
    
               **floatis** , **floatus** , **floatid** , **floatud**
                   Conversion from signed or unsigned integer types to
                   floating-point types.
    
               In addition, all of the following transfer instructions for
               internal registers X and Y must be provided to use any of the
               double-precision floating-point instructions.  Custom
               instructions taking two double-precision source operands
               expect the first operand in the 64-bit register X.  The other
               operand (or only operand of a unary operation) is given to the
               custom arithmetic instruction with the least significant half
               in source register _src1_ and the most significant half in _src2_.
               A custom instruction that returns a double-precision result
               returns the most significant 32 bits in the destination
               register and the other half in 32-bit register Y.  GCC
               automatically generates the necessary code sequences to write
               register X and/or read register Y when double-precision
               floating-point instructions are used.
    
               **fwrx**
                   Write _src1_ into the least significant half of X and _src2_
                   into the most significant half of X.
    
               **fwry**
                   Write _src1_ into Y.
    
               **frdxhi** , **frdxlo**
                   Read the most or least (respectively) significant half of
                   X and store it in _dest_.
    
               **frdy**
                   Read the value of Y and store it into _dest_.
    
               Note that you can gain more local control over generation of
               Nios II custom instructions by using the
               "target("custom-_insn=N")"_ and "target("no-custom-_insn")"_
               function attributes or pragmas.
    
           **-mcustom-fpu-cfg=**_name_
               This option enables a predefined, named set of custom
               instruction encodings (see **-mcustom-**_insn_ above).  Currently,
               the following sets are defined:
    
               **-mcustom-fpu-cfg=60-1** is equivalent to: **-mcustom-fmuls=252**
               **-mcustom-fadds=253 -mcustom-fsubs=254**
               **-fsingle-precision-constant**
    
               **-mcustom-fpu-cfg=60-2** is equivalent to: **-mcustom-fmuls=252**
               **-mcustom-fadds=253 -mcustom-fsubs=254 -mcustom-fdivs=255**
               **-fsingle-precision-constant**
    
               **-mcustom-fpu-cfg=72-3** is equivalent to: **-mcustom-floatus=243**
               **-mcustom-fixsi=244 -mcustom-floatis=245 -mcustom-fcmpgts=246**
               **-mcustom-fcmples=249 -mcustom-fcmpeqs=250 -mcustom-fcmpnes=251**
               **-mcustom-fmuls=252 -mcustom-fadds=253 -mcustom-fsubs=254**
               **-mcustom-fdivs=255 -fsingle-precision-constant**
    
               Custom instruction assignments given by individual
               **-mcustom-**_insn_**=** options override those given by
               **-mcustom-fpu-cfg=** , regardless of the order of the options on
               the command line.
    
               Note that you can gain more local control over selection of a
               FPU configuration by using the "target("custom-fpu-cfg=_name")"_
               function attribute or pragma.
    
           These additional **-m** options are available for the Altera Nios II
           ELF (bare-metal) target:
    
           **-mhal**
               Link with HAL BSP.  This suppresses linking with the GCC-
               provided C runtime startup and termination code, and is
               typically used in conjunction with **-msys-crt0=** to specify the
               location of the alternate startup code provided by the HAL
               BSP.
    
           **-msmallc**
               Link with a limited version of the C library, **-lsmallc** , rather
               than Newlib.
    
           **-msys-crt0=**_startfile_
               _startfile_ is the file name of the startfile (crt0) to use when
               linking.  This option is only useful in conjunction with
               **-mhal**.
    
           **-msys-lib=**_systemlib_
               _systemlib_ is the library name of the library that provides
               low-level system calls required by the C library, e.g. "read"
               and "write".  This option is typically used to link with a
               library provided by a HAL BSP.
    
           _Nvidia PTX Options_
    
           These options are defined for Nvidia PTX:
    
           **-m32**
           **-m64**
               Generate code for 32-bit or 64-bit ABI.
    
           **-misa=**_ISA-string_
               Generate code for given the specified PTX ISA (e.g. **sm_35**).
               ISA strings must be lower-case.  Valid ISA strings include
               **sm_30** and **sm_35**.  The default ISA is sm_30.
    
           **-mmainkernel**
               Link in code for a __main kernel.  This is for stand-alone
               instead of offloading execution.
    
           **-moptimize**
               Apply partitioned execution optimizations.  This is the
               default when any level of optimization is selected.
    
           **-msoft-stack**
               Generate code that does not use ".local" memory directly for
               stack storage. Instead, a per-warp stack pointer is maintained
               explicitly. This enables variable-length stack allocation
               (with variable-length arrays or "alloca"), and when global
               memory is used for underlying storage, makes it possible to
               access automatic variables from other threads, or with atomic
               instructions. This code generation variant is used for OpenMP
               offloading, but the option is exposed on its own for the
               purpose of testing the compiler; to generate code suitable for
               linking into programs using OpenMP offloading, use option
               **-mgomp**.
    
           **-muniform-simt**
               Switch to code generation variant that allows to execute all
               threads in each warp, while maintaining memory state and side
               effects as if only one thread in each warp was active outside
               of OpenMP SIMD regions.  All atomic operations and calls to
               runtime (malloc, free, vprintf) are conditionally executed
               (iff current lane index equals the master lane index), and the
               register being assigned is copied via a shuffle instruction
               from the master lane.  Outside of SIMD regions lane 0 is the
               master; inside, each thread sees itself as the master.  Shared
               memory array "int __nvptx_uni[]" stores all-zeros or all-ones
               bitmasks for each warp, indicating current mode (0 outside of
               SIMD regions).  Each thread can bitwise-and the bitmask at
               position "tid.y" with current lane index to compute the master
               lane index.
    
           **-mgomp**
               Generate code for use in OpenMP offloading: enables
               **-msoft-stack** and **-muniform-simt** options, and selects
               corresponding multilib variant.
    
           _OpenRISC Options_
    
           These options are defined for OpenRISC:
    
           **-mboard=**_name_
               Configure a board specific runtime.  This will be passed to
               the linker for newlib board library linking.  The default is
               "or1ksim".
    
           **-mnewlib**
               For compatibility, it's always newlib for elf now.
    
           **-mhard-div**
               Generate code for hardware which supports divide instructions.
               This is the default.
    
           **-mhard-mul**
               Generate code for hardware which supports multiply
               instructions.  This is the default.
    
           **-mcmov**
               Generate code for hardware which supports the conditional move
               ("l.cmov") instruction.
    
           **-mror**
               Generate code for hardware which supports rotate right
               instructions.
    
           **-msext**
               Generate code for hardware which supports sign-extension
               instructions.
    
           **-msfimm**
               Generate code for hardware which supports set flag immediate
               ("l.sf*i") instructions.
    
           **-mshftimm**
               Generate code for hardware which supports shift immediate
               related instructions (i.e. "l.srai", "l.srli", "l.slli",
               "1.rori").  Note, to enable generation of the "l.rori"
               instruction the **-mror** flag must also be specified.
    
           **-msoft-div**
               Generate code for hardware which requires divide instruction
               emulation.
    
           **-msoft-mul**
               Generate code for hardware which requires multiply instruction
               emulation.
    
           _PDP-11 Options_
    
           These options are defined for the PDP-11:
    
           **-mfpu**
               Use hardware FPP floating point.  This is the default.  (FIS
               floating point on the PDP-11/40 is not supported.)  Implies
               -m45.
    
           **-msoft-float**
               Do not use hardware floating point.
    
           **-mac0**
               Return floating-point results in ac0 (fr0 in Unix assembler
               syntax).
    
           **-mno-ac0**
               Return floating-point results in memory.  This is the default.
    
           **-m40**
               Generate code for a PDP-11/40.  Implies -msoft-float
               -mno-split.
    
           **-m45**
               Generate code for a PDP-11/45.  This is the default.
    
           **-m10**
               Generate code for a PDP-11/10.  Implies -msoft-float
               -mno-split.
    
           **-mint16**
           **-mno-int32**
               Use 16-bit "int".  This is the default.
    
           **-mint32**
           **-mno-int16**
               Use 32-bit "int".
    
           **-msplit**
               Target has split instruction and data space.  Implies -m45.
    
           **-munix-asm**
               Use Unix assembler syntax.
    
           **-mdec-asm**
               Use DEC assembler syntax.
    
           **-mgnu-asm**
               Use GNU assembler syntax.  This is the default.
    
           **-mlra**
               Use the new LRA register allocator.  By default, the old
               "reload" allocator is used.
    
           _picoChip Options_
    
           These **-m** options are defined for picoChip implementations:
    
           **-mae=**_ae_type_
               Set the instruction set, register set, and instruction
               scheduling parameters for array element type _ae_type_.
               Supported values for _ae_type_ are **ANY** , **MUL** , and **MAC**.
    
               **-mae=ANY** selects a completely generic AE type.  Code generated
               with this option runs on any of the other AE types.  The code
               is not as efficient as it would be if compiled for a specific
               AE type, and some types of operation (e.g., multiplication) do
               not work properly on all types of AE.
    
               **-mae=MUL** selects a MUL AE type.  This is the most useful AE
               type for compiled code, and is the default.
    
               **-mae=MAC** selects a DSP-style MAC AE.  Code compiled with this
               option may suffer from poor performance of byte (char)
               manipulation, since the DSP AE does not provide hardware
               support for byte load/stores.
    
           **-msymbol-as-address**
               Enable the compiler to directly use a symbol name as an
               address in a load/store instruction, without first loading it
               into a register.  Typically, the use of this option generates
               larger programs, which run faster than when the option isn't
               used.  However, the results vary from program to program, so
               it is left as a user option, rather than being permanently
               enabled.
    
           **-mno-inefficient-warnings**
               Disables warnings about the generation of inefficient code.
               These warnings can be generated, for example, when compiling
               code that performs byte-level memory operations on the MAC AE
               type.  The MAC AE has no hardware support for byte-level
               memory operations, so all byte load/stores must be synthesized
               from word load/store operations.  This is inefficient and a
               warning is generated to indicate that you should rewrite the
               code to avoid byte operations, or to target an AE type that
               has the necessary hardware support.  This option disables
               these warnings.
    
           _PowerPC Options_
    
           These are listed under
    
           _RISC-V Options_
    
           These command-line options are defined for RISC-V targets:
    
           **-mbranch-cost=**_n_
               Set the cost of branches to roughly _n_ instructions.
    
           **-mplt**
           **-mno-plt**
               When generating PIC code, do or don't allow the use of PLTs.
               Ignored for non-PIC.  The default is **-mplt**.
    
           **-mabi=**_ABI-string_
               Specify integer and floating-point calling convention.  _ABI-_
               _string_ contains two parts: the size of integer types and the
               registers used for floating-point types.  For example
               **-march=rv64ifd -mabi=lp64d** means that **long** and pointers are
               64-bit (implicitly defining **int** to be 32-bit), and that
               floating-point values up to 64 bits wide are passed in F
               registers.  Contrast this with **-march=rv64ifd -mabi=lp64f** ,
               which still allows the compiler to generate code that uses the
               F and D extensions but only allows floating-point values up to
               32 bits long to be passed in registers; or **-march=rv64ifd**
               **-mabi=lp64** , in which no floating-point arguments will be
               passed in registers.
    
               The default for this argument is system dependent, users who
               want a specific calling convention should specify one
               explicitly.  The valid calling conventions are: **ilp32** , **ilp32f** ,
               **ilp32d** , **lp64** , **lp64f** , and **lp64d**.  Some calling conventions are
               impossible to implement on some ISAs: for example,
               **-march=rv32if -mabi=ilp32d** is invalid because the ABI requires
               64-bit values be passed in F registers, but F registers are
               only 32 bits wide.  There is also the **ilp32e** ABI that can only
               be used with the **rv32e** architecture.  This ABI is not well
               specified at present, and is subject to change.
    
           **-mfdiv**
           **-mno-fdiv**
               Do or don't use hardware floating-point divide and square root
               instructions.  This requires the F or D extensions for
               floating-point registers.  The default is to use them if the
               specified architecture has these instructions.
    
           **-mdiv**
           **-mno-div**
               Do or don't use hardware instructions for integer division.
               This requires the M extension.  The default is to use them if
               the specified architecture has these instructions.
    
           **-march=**_ISA-string_
               Generate code for given RISC-V ISA (e.g. **rv64im**).  ISA strings
               must be lower-case.  Examples include **rv64i** , **rv32g** , **rv32e** , and
               **rv32imaf**.
    
           **-mtune=**_processor-string_
               Optimize the output for the given processor, specified by
               microarchitecture name.  Permissible values for this option
               are: **rocket** , **sifive-3-series** , **sifive-5-series** ,
               **sifive-7-series** , and **size**.
    
               When **-mtune=** is not specified, the default is **rocket**.
    
               The **size** choice is not intended for use by end-users.  This is
               used when **-Os** is specified.  It overrides the instruction cost
               info provided by **-mtune=** , but does not override the pipeline
               info.  This helps reduce code size while still giving good
               performance.
    
           **-mpreferred-stack-boundary=**_num_
               Attempt to keep the stack boundary aligned to a 2 raised to
               _num_ byte boundary.  If **-mpreferred-stack-boundary** is not
               specified, the default is 4 (16 bytes or 128-bits).
    
               **Warning:** If you use this switch, then you must build all
               modules with the same value, including any libraries.  This
               includes the system libraries and startup modules.
    
           **-msmall-data-limit=**_n_
               Put global and static data smaller than _n_ bytes into a special
               section (on some targets).
    
           **-msave-restore**
           **-mno-save-restore**
               Do or don't use smaller but slower prologue and epilogue code
               that uses library function calls.  The default is to use fast
               inline prologues and epilogues.
    
           **-mstrict-align**
           **-mno-strict-align**
               Do not or do generate unaligned memory accesses.  The default
               is set depending on whether the processor we are optimizing
               for supports fast unaligned access or not.
    
           **-mcmodel=medlow**
               Generate code for the medium-low code model. The program and
               its statically defined symbols must lie within a single 2 GiB
               address range and must lie between absolute addresses -2 GiB
               and +2 GiB. Programs can be statically or dynamically linked.
               This is the default code model.
    
           **-mcmodel=medany**
               Generate code for the medium-any code model. The program and
               its statically defined symbols must be within any single 2 GiB
               address range. Programs can be statically or dynamically
               linked.
    
           **-mexplicit-relocs**
           **-mno-exlicit-relocs**
               Use or do not use assembler relocation operators when dealing
               with symbolic addresses.  The alternative is to use assembler
               macros instead, which may limit optimization.
    
           **-mrelax**
           **-mno-relax**
               Take advantage of linker relaxations to reduce the number of
               instructions required to materialize symbol addresses. The
               default is to take advantage of linker relaxations.
    
           **-memit-attribute**
           **-mno-emit-attribute**
               Emit (do not emit) RISC-V attribute to record extra
               information into ELF objects.  This feature requires at least
               binutils 2.32.
    
           _RL78 Options_
    
           **-msim**
               Links in additional target libraries to support operation
               within a simulator.
    
           **-mmul=none**
           **-mmul=g10**
           **-mmul=g13**
           **-mmul=g14**
           **-mmul=rl78**
               Specifies the type of hardware multiplication and division
               support to be used.  The simplest is "none", which uses
               software for both multiplication and division.  This is the
               default.  The "g13" value is for the hardware multiply/divide
               peripheral found on the RL78/G13 (S2 core) targets.  The "g14"
               value selects the use of the multiplication and division
               instructions supported by the RL78/G14 (S3 core) parts.  The
               value "rl78" is an alias for "g14" and the value "mg10" is an
               alias for "none".
    
               In addition a C preprocessor macro is defined, based upon the
               setting of this option.  Possible values are:
               "__RL78_MUL_NONE__", "__RL78_MUL_G13__" or "__RL78_MUL_G14__".
    
           **-mcpu=g10**
           **-mcpu=g13**
           **-mcpu=g14**
           **-mcpu=rl78**
               Specifies the RL78 core to target.  The default is the G14
               core, also known as an S3 core or just RL78.  The G13 or S2
               core does not have multiply or divide instructions, instead it
               uses a hardware peripheral for these operations.  The G10 or
               S1 core does not have register banks, so it uses a different
               calling convention.
    
               If this option is set it also selects the type of hardware
               multiply support to use, unless this is overridden by an
               explicit **-mmul=none** option on the command line.  Thus
               specifying **-mcpu=g13** enables the use of the G13 hardware
               multiply peripheral and specifying **-mcpu=g10** disables the use
               of hardware multiplications altogether.
    
               Note, although the RL78/G14 core is the default target,
               specifying **-mcpu=g14** or **-mcpu=rl78** on the command line does
               change the behavior of the toolchain since it also enables G14
               hardware multiply support.  If these options are not specified
               on the command line then software multiplication routines will
               be used even though the code targets the RL78 core.  This is
               for backwards compatibility with older toolchains which did
               not have hardware multiply and divide support.
    
               In addition a C preprocessor macro is defined, based upon the
               setting of this option.  Possible values are: "__RL78_G10__",
               "__RL78_G13__" or "__RL78_G14__".
    
           **-mg10**
           **-mg13**
           **-mg14**
           **-mrl78**
               These are aliases for the corresponding **-mcpu=** option.  They
               are provided for backwards compatibility.
    
           **-mallregs**
               Allow the compiler to use all of the available registers.  By
               default registers "r24..r31" are reserved for use in interrupt
               handlers.  With this option enabled these registers can be
               used in ordinary functions as well.
    
           **-m64bit-doubles**
           **-m32bit-doubles**
               Make the "double" data type be 64 bits (**-m64bit-doubles**) or 32
               bits (**-m32bit-doubles**) in size.  The default is
               **-m32bit-doubles**.
    
           **-msave-mduc-in-interrupts**
           **-mno-save-mduc-in-interrupts**
               Specifies that interrupt handler functions should preserve the
               MDUC registers.  This is only necessary if normal code might
               use the MDUC registers, for example because it performs
               multiplication and division operations.  The default is to
               ignore the MDUC registers as this makes the interrupt handlers
               faster.  The target option -mg13 needs to be passed for this
               to work as this feature is only available on the G13 target
               (S2 core).  The MDUC registers will only be saved if the
               interrupt handler performs a multiplication or division
               operation or it calls another function.
    
           _IBM RS/6000 and PowerPC Options_
    
           These **-m** options are defined for the IBM RS/6000 and PowerPC:
    
           **-mpowerpc-gpopt**
           **-mno-powerpc-gpopt**
           **-mpowerpc-gfxopt**
           **-mno-powerpc-gfxopt**
           **-mpowerpc64**
           **-mno-powerpc64**
           **-mmfcrf**
           **-mno-mfcrf**
           **-mpopcntb**
           **-mno-popcntb**
           **-mpopcntd**
           **-mno-popcntd**
           **-mfprnd**
           **-mno-fprnd**
           **-mcmpb**
           **-mno-cmpb**
           **-mmfpgpr**
           **-mno-mfpgpr**
           **-mhard-dfp**
           **-mno-hard-dfp**
               You use these options to specify which instructions are
               available on the processor you are using.  The default value
               of these options is determined when configuring GCC.
               Specifying the **-mcpu=**_cpu_type_ overrides the specification of
               these options.  We recommend you use the **-mcpu=**_cpu_type_ option
               rather than the options listed above.
    
               Specifying **-mpowerpc-gpopt** allows GCC to use the optional
               PowerPC architecture instructions in the General Purpose
               group, including floating-point square root.  Specifying
               **-mpowerpc-gfxopt** allows GCC to use the optional PowerPC
               architecture instructions in the Graphics group, including
               floating-point select.
    
               The **-mmfcrf** option allows GCC to generate the move from
               condition register field instruction implemented on the POWER4
               processor and other processors that support the PowerPC V2.01
               architecture.  The **-mpopcntb** option allows GCC to generate the
               popcount and double-precision FP reciprocal estimate
               instruction implemented on the POWER5 processor and other
               processors that support the PowerPC V2.02 architecture.  The
               **-mpopcntd** option allows GCC to generate the popcount
               instruction implemented on the POWER7 processor and other
               processors that support the PowerPC V2.06 architecture.  The
               **-mfprnd** option allows GCC to generate the FP round to integer
               instructions implemented on the POWER5+ processor and other
               processors that support the PowerPC V2.03 architecture.  The
               **-mcmpb** option allows GCC to generate the compare bytes
               instruction implemented on the POWER6 processor and other
               processors that support the PowerPC V2.05 architecture.  The
               **-mmfpgpr** option allows GCC to generate the FP move to/from
               general-purpose register instructions implemented on the
               POWER6X processor and other processors that support the
               extended PowerPC V2.05 architecture.  The **-mhard-dfp** option
               allows GCC to generate the decimal floating-point instructions
               implemented on some POWER processors.
    
               The **-mpowerpc64** option allows GCC to generate the additional
               64-bit instructions that are found in the full PowerPC64
               architecture and to treat GPRs as 64-bit, doubleword
               quantities.  GCC defaults to **-mno-powerpc64**.
    
           **-mcpu=**_cpu_type_
               Set architecture type, register usage, and instruction
               scheduling parameters for machine type _cpu_type_.  Supported
               values for _cpu_type_ are **401** , **403** , **405** , **405fp** , **440** , **440fp** , **464** ,
               **464fp** , **476** , **476fp** , **505** , **601** , **602** , **603** , **603e** , **604** , **604e** , **620** ,
               **630** , **740** , **7400** , **7450** , **750** , **801** , **821** , **823** , **860** , **970** , **8540** , **a2** ,
               **e300c2** , **e300c3** , **e500mc** , **e500mc64** , **e5500** , **e6500** , **ec603e** , **G3** ,
               **G4** , **G5** , **titan** , **power3** , **power4** , **power5** , **power5+** , **power6** ,
               **power6x** , **power7** , **power8** , **power9** , **powerpc** , **powerpc64** ,
               **powerpc64le** , **rs64** , and **native**.
    
               **-mcpu=powerpc** , **-mcpu=powerpc64** , and **-mcpu=powerpc64le** specify
               pure 32-bit PowerPC (either endian), 64-bit big endian PowerPC
               and 64-bit little endian PowerPC architecture machine types,
               with an appropriate, generic processor model assumed for
               scheduling purposes.
    
               Specifying **native** as cpu type detects and selects the
               architecture option that corresponds to the host processor of
               the system performing the compilation.  **-mcpu=native** has no
               effect if GCC does not recognize the processor.
    
               The other options specify a specific processor.  Code
               generated under those options runs best on that processor, and
               may not run at all on others.
    
               The **-mcpu** options automatically enable or disable the
               following options:
    
               **-maltivec  -mfprnd  -mhard-float  -mmfcrf  -mmultiple**
               **-mpopcntb  -mpopcntd  -mpowerpc64 -mpowerpc-gpopt**
               **-mpowerpc-gfxopt -mmulhw  -mdlmzb  -mmfpgpr  -mvsx -mcrypto**
               **-mhtm  -mpower8-fusion  -mpower8-vector -mquad-memory**
               **-mquad-memory-atomic  -mfloat128  -mfloat128-hardware**
    
               The particular options set for any particular CPU varies
               between compiler versions, depending on what setting seems to
               produce optimal code for that CPU; it doesn't necessarily
               reflect the actual hardware's capabilities.  If you wish to
               set an individual option to a particular value, you may
               specify it after the **-mcpu** option, like **-mcpu=970**
               **-mno-altivec**.
    
               On AIX, the **-maltivec** and **-mpowerpc64** options are not enabled
               or disabled by the **-mcpu** option at present because AIX does
               not have full support for these options.  You may still enable
               or disable them individually if you're sure it'll work in your
               environment.
    
           **-mtune=**_cpu_type_
               Set the instruction scheduling parameters for machine type
               _cpu_type_ , but do not set the architecture type or register
               usage, as **-mcpu=**_cpu_type_ does.  The same values for _cpu_type_
               are used for **-mtune** as for **-mcpu**.  If both are specified, the
               code generated uses the architecture and registers set by
               **-mcpu** , but the scheduling parameters set by **-mtune**.
    
           **-mcmodel=small**
               Generate PowerPC64 code for the small model: The TOC is
               limited to 64k.
    
           **-mcmodel=medium**
               Generate PowerPC64 code for the medium model: The TOC and
               other static data may be up to a total of 4G in size.  This is
               the default for 64-bit Linux.
    
           **-mcmodel=large**
               Generate PowerPC64 code for the large model: The TOC may be up
               to 4G in size.  Other data and code is only limited by the
               64-bit address space.
    
           **-maltivec**
           **-mno-altivec**
               Generate code that uses (does not use) AltiVec instructions,
               and also enable the use of built-in functions that allow more
               direct access to the AltiVec instruction set.  You may also
               need to set **-mabi=altivec** to adjust the current ABI with
               AltiVec ABI enhancements.
    
               When **-maltivec** is used, the element order for AltiVec
               intrinsics such as "vec_splat", "vec_extract", and
               "vec_insert" match array element order corresponding to the
               endianness of the target.  That is, element zero identifies
               the leftmost element in a vector register when targeting a
               big-endian platform, and identifies the rightmost element in a
               vector register when targeting a little-endian platform.
    
           **-mvrsave**
           **-mno-vrsave**
               Generate VRSAVE instructions when generating AltiVec code.
    
           **-msecure-plt**
               Generate code that allows **ld** and **ld.so** to build executables
               and shared libraries with non-executable ".plt" and ".got"
               sections.  This is a PowerPC 32-bit SYSV ABI option.
    
           **-mbss-plt**
               Generate code that uses a BSS ".plt" section that **ld.so** fills
               in, and requires ".plt" and ".got" sections that are both
               writable and executable.  This is a PowerPC 32-bit SYSV ABI
               option.
    
           **-misel**
           **-mno-isel**
               This switch enables or disables the generation of ISEL
               instructions.
    
           **-mvsx**
           **-mno-vsx**
               Generate code that uses (does not use) vector/scalar (VSX)
               instructions, and also enable the use of built-in functions
               that allow more direct access to the VSX instruction set.
    
           **-mcrypto**
           **-mno-crypto**
               Enable the use (disable) of the built-in functions that allow
               direct access to the cryptographic instructions that were
               added in version 2.07 of the PowerPC ISA.
    
           **-mhtm**
           **-mno-htm**
               Enable (disable) the use of the built-in functions that allow
               direct access to the Hardware Transactional Memory (HTM)
               instructions that were added in version 2.07 of the PowerPC
               ISA.
    
           **-mpower8-fusion**
           **-mno-power8-fusion**
               Generate code that keeps (does not keeps) some integer
               operations adjacent so that the instructions can be fused
               together on power8 and later processors.
    
           **-mpower8-vector**
           **-mno-power8-vector**
               Generate code that uses (does not use) the vector and scalar
               instructions that were added in version 2.07 of the PowerPC
               ISA.  Also enable the use of built-in functions that allow
               more direct access to the vector instructions.
    
           **-mquad-memory**
           **-mno-quad-memory**
               Generate code that uses (does not use) the non-atomic quad
               word memory instructions.  The **-mquad-memory** option requires
               use of 64-bit mode.
    
           **-mquad-memory-atomic**
           **-mno-quad-memory-atomic**
               Generate code that uses (does not use) the atomic quad word
               memory instructions.  The **-mquad-memory-atomic** option requires
               use of 64-bit mode.
    
           **-mfloat128**
           **-mno-float128**
               Enable/disable the ___float128_ keyword for IEEE 128-bit
               floating point and use either software emulation for IEEE
               128-bit floating point or hardware instructions.
    
               The VSX instruction set (**-mvsx** , **-mcpu=power7** , **-mcpu=power8**),
               or **-mcpu=power9** must be enabled to use the IEEE 128-bit
               floating point support.  The IEEE 128-bit floating point
               support only works on PowerPC Linux systems.
    
               The default for **-mfloat128** is enabled on PowerPC Linux systems
               using the VSX instruction set, and disabled on other systems.
    
               If you use the ISA 3.0 instruction set (**-mpower9-vector** or
               **-mcpu=power9**) on a 64-bit system, the IEEE 128-bit floating
               point support will also enable the generation of ISA 3.0 IEEE
               128-bit floating point instructions.  Otherwise, if you do not
               specify to generate ISA 3.0 instructions or you are targeting
               a 32-bit big endian system, IEEE 128-bit floating point will
               be done with software emulation.
    
           **-mfloat128-hardware**
           **-mno-float128-hardware**
               Enable/disable using ISA 3.0 hardware instructions to support
               the ___float128_ data type.
    
               The default for **-mfloat128-hardware** is enabled on PowerPC
               Linux systems using the ISA 3.0 instruction set, and disabled
               on other systems.
    
           **-m32**
           **-m64**
               Generate code for 32-bit or 64-bit environments of Darwin and
               SVR4 targets (including GNU/Linux).  The 32-bit environment
               sets int, long and pointer to 32 bits and generates code that
               runs on any PowerPC variant.  The 64-bit environment sets int
               to 32 bits and long and pointer to 64 bits, and generates code
               for PowerPC64, as for **-mpowerpc64**.
    
           **-mfull-toc**
           **-mno-fp-in-toc**
           **-mno-sum-in-toc**
           **-mminimal-toc**
               Modify generation of the TOC (Table Of Contents), which is
               created for every executable file.  The **-mfull-toc** option is
               selected by default.  In that case, GCC allocates at least one
               TOC entry for each unique non-automatic variable reference in
               your program.  GCC also places floating-point constants in the
               TOC.  However, only 16,384 entries are available in the TOC.
    
               If you receive a linker error message that saying you have
               overflowed the available TOC space, you can reduce the amount
               of TOC space used with the **-mno-fp-in-toc** and **-mno-sum-in-toc**
               options.  **-mno-fp-in-toc** prevents GCC from putting floating-
               point constants in the TOC and **-mno-sum-in-toc** forces GCC to
               generate code to calculate the sum of an address and a
               constant at run time instead of putting that sum into the TOC.
               You may specify one or both of these options.  Each causes GCC
               to produce very slightly slower and larger code at the expense
               of conserving TOC space.
    
               If you still run out of space in the TOC even when you specify
               both of these options, specify **-mminimal-toc** instead.  This
               option causes GCC to make only one TOC entry for every file.
               When you specify this option, GCC produces code that is slower
               and larger but which uses extremely little TOC space.  You may
               wish to use this option only on files that contain less
               frequently-executed code.
    
           **-maix64**
           **-maix32**
               Enable 64-bit AIX ABI and calling convention: 64-bit pointers,
               64-bit "long" type, and the infrastructure needed to support
               them.  Specifying **-maix64** implies **-mpowerpc64** , while **-maix32**
               disables the 64-bit ABI and implies **-mno-powerpc64**.  GCC
               defaults to **-maix32**.
    
           **-mxl-compat**
           **-mno-xl-compat**
               Produce code that conforms more closely to IBM XL compiler
               semantics when using AIX-compatible ABI.  Pass floating-point
               arguments to prototyped functions beyond the register save
               area (RSA) on the stack in addition to argument FPRs.  Do not
               assume that most significant double in 128-bit long double
               value is properly rounded when comparing values and converting
               to double.  Use XL symbol names for long double support
               routines.
    
               The AIX calling convention was extended but not initially
               documented to handle an obscure K&R C case of calling a
               function that takes the address of its arguments with fewer
               arguments than declared.  IBM XL compilers access floating-
               point arguments that do not fit in the RSA from the stack when
               a subroutine is compiled without optimization.  Because always
               storing floating-point arguments on the stack is inefficient
               and rarely needed, this option is not enabled by default and
               only is necessary when calling subroutines compiled by IBM XL
               compilers without optimization.
    
           **-mpe**
               Support _IBM RS/6000 SP Parallel Environment_ (PE).  Link an
               application written to use message passing with special
               startup code to enable the application to run.  The system
               must have PE installed in the standard location
               (_/usr/lpp/ppe.poe/_), or the _specs_ file must be overridden with
               the **-specs=** option to specify the appropriate directory
               location.  The Parallel Environment does not support threads,
               so the **-mpe** option and the **-pthread** option are incompatible.
    
           **-malign-natural**
           **-malign-power**
               On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the
               option **-malign-natural** overrides the ABI-defined alignment of
               larger types, such as floating-point doubles, on their natural
               size-based boundary.  The option **-malign-power** instructs GCC
               to follow the ABI-specified alignment rules.  GCC defaults to
               the standard alignment defined in the ABI.
    
               On 64-bit Darwin, natural alignment is the default, and
               **-malign-power** is not supported.
    
           **-msoft-float**
           **-mhard-float**
               Generate code that does not use (uses) the floating-point
               register set.  Software floating-point emulation is provided
               if you use the **-msoft-float** option, and pass the option to GCC
               when linking.
    
           **-mmultiple**
           **-mno-multiple**
               Generate code that uses (does not use) the load multiple word
               instructions and the store multiple word instructions.  These
               instructions are generated by default on POWER systems, and
               not generated on PowerPC systems.  Do not use **-mmultiple** on
               little-endian PowerPC systems, since those instructions do not
               work when the processor is in little-endian mode.  The
               exceptions are PPC740 and PPC750 which permit these
               instructions in little-endian mode.
    
           **-mupdate**
           **-mno-update**
               Generate code that uses (does not use) the load or store
               instructions that update the base register to the address of
               the calculated memory location.  These instructions are
               generated by default.  If you use **-mno-update** , there is a
               small window between the time that the stack pointer is
               updated and the address of the previous frame is stored, which
               means code that walks the stack frame across interrupts or
               signals may get corrupted data.
    
           **-mavoid-indexed-addresses**
           **-mno-avoid-indexed-addresses**
               Generate code that tries to avoid (not avoid) the use of
               indexed load or store instructions. These instructions can
               incur a performance penalty on Power6 processors in certain
               situations, such as when stepping through large arrays that
               cross a 16M boundary.  This option is enabled by default when
               targeting Power6 and disabled otherwise.
    
           **-mfused-madd**
           **-mno-fused-madd**
               Generate code that uses (does not use) the floating-point
               multiply and accumulate instructions.  These instructions are
               generated by default if hardware floating point is used.  The
               machine-dependent **-mfused-madd** option is now mapped to the
               machine-independent **-ffp-contract=fast** option, and
               **-mno-fused-madd** is mapped to **-ffp-contract=off**.
    
           **-mmulhw**
           **-mno-mulhw**
               Generate code that uses (does not use) the half-word multiply
               and multiply-accumulate instructions on the IBM 405, 440, 464
               and 476 processors.  These instructions are generated by
               default when targeting those processors.
    
           **-mdlmzb**
           **-mno-dlmzb**
               Generate code that uses (does not use) the string-search **dlmzb**
               instruction on the IBM 405, 440, 464 and 476 processors.  This
               instruction is generated by default when targeting those
               processors.
    
           **-mno-bit-align**
           **-mbit-align**
               On System V.4 and embedded PowerPC systems do not (do) force
               structures and unions that contain bit-fields to be aligned to
               the base type of the bit-field.
    
               For example, by default a structure containing nothing but 8
               "unsigned" bit-fields of length 1 is aligned to a 4-byte
               boundary and has a size of 4 bytes.  By using **-mno-bit-align** ,
               the structure is aligned to a 1-byte boundary and is 1 byte in
               size.
    
           **-mno-strict-align**
           **-mstrict-align**
               On System V.4 and embedded PowerPC systems do not (do) assume
               that unaligned memory references are handled by the system.
    
           **-mrelocatable**
           **-mno-relocatable**
               Generate code that allows (does not allow) a static executable
               to be relocated to a different address at run time.  A simple
               embedded PowerPC system loader should relocate the entire
               contents of ".got2" and 4-byte locations listed in the
               ".fixup" section, a table of 32-bit addresses generated by
               this option.  For this to work, all objects linked together
               must be compiled with **-mrelocatable** or **-mrelocatable-lib**.
               **-mrelocatable** code aligns the stack to an 8-byte boundary.
    
           **-mrelocatable-lib**
           **-mno-relocatable-lib**
               Like **-mrelocatable** , **-mrelocatable-lib** generates a ".fixup"
               section to allow static executables to be relocated at run
               time, but **-mrelocatable-lib** does not use the smaller stack
               alignment of **-mrelocatable**.  Objects compiled with
               **-mrelocatable-lib** may be linked with objects compiled with any
               combination of the **-mrelocatable** options.
    
           **-mno-toc**
           **-mtoc**
               On System V.4 and embedded PowerPC systems do not (do) assume
               that register 2 contains a pointer to a global area pointing
               to the addresses used in the program.
    
           **-mlittle**
           **-mlittle-endian**
               On System V.4 and embedded PowerPC systems compile code for
               the processor in little-endian mode.  The **-mlittle-endian**
               option is the same as **-mlittle**.
    
           **-mbig**
           **-mbig-endian**
               On System V.4 and embedded PowerPC systems compile code for
               the processor in big-endian mode.  The **-mbig-endian** option is
               the same as **-mbig**.
    
           **-mdynamic-no-pic**
               On Darwin and Mac OS X systems, compile code so that it is not
               relocatable, but that its external references are relocatable.
               The resulting code is suitable for applications, but not
               shared libraries.
    
           **-msingle-pic-base**
               Treat the register used for PIC addressing as read-only,
               rather than loading it in the prologue for each function.  The
               runtime system is responsible for initializing this register
               with an appropriate value before execution begins.
    
           **-mprioritize-restricted-insns=**_priority_
               This option controls the priority that is assigned to
               dispatch-slot restricted instructions during the second
               scheduling pass.  The argument _priority_ takes the value **0** , **1** ,
               or **2** to assign no, highest, or second-highest (respectively)
               priority to dispatch-slot restricted instructions.
    
           **-msched-costly-dep=**_dependence_type_
               This option controls which dependences are considered costly
               by the target during instruction scheduling.  The argument
               _dependence_type_ takes one of the following values:
    
               **no** No dependence is costly.
    
               **all** All dependences are costly.
    
               **true_store_to_load**
                   A true dependence from store to load is costly.
    
               **store_to_load**
                   Any dependence from store to load is costly.
    
               _number_
                   Any dependence for which the latency is greater than or
                   equal to _number_ is costly.
    
           **-minsert-sched-nops=**_scheme_
               This option controls which NOP insertion scheme is used during
               the second scheduling pass.  The argument _scheme_ takes one of
               the following values:
    
               **no** Don't insert NOPs.
    
               **pad** Pad with NOPs any dispatch group that has vacant issue
                   slots, according to the scheduler's grouping.
    
               **regroup_exact**
                   Insert NOPs to force costly dependent insns into separate
                   groups.  Insert exactly as many NOPs as needed to force an
                   insn to a new group, according to the estimated processor
                   grouping.
    
               _number_
                   Insert NOPs to force costly dependent insns into separate
                   groups.  Insert _number_ NOPs to force an insn to a new
                   group.
    
           **-mcall-sysv**
               On System V.4 and embedded PowerPC systems compile code using
               calling conventions that adhere to the March 1995 draft of the
               System V Application Binary Interface, PowerPC processor
               supplement.  This is the default unless you configured GCC
               using **powerpc-*-eabiaix**.
    
           **-mcall-sysv-eabi**
           **-mcall-eabi**
               Specify both **-mcall-sysv** and **-meabi** options.
    
           **-mcall-sysv-noeabi**
               Specify both **-mcall-sysv** and **-mno-eabi** options.
    
           **-mcall-aixdesc**
               On System V.4 and embedded PowerPC systems compile code for
               the AIX operating system.
    
           **-mcall-linux**
               On System V.4 and embedded PowerPC systems compile code for
               the Linux-based GNU system.
    
           **-mcall-freebsd**
               On System V.4 and embedded PowerPC systems compile code for
               the FreeBSD operating system.
    
           **-mcall-netbsd**
               On System V.4 and embedded PowerPC systems compile code for
               the NetBSD operating system.
    
           **-mcall-openbsd**
               On System V.4 and embedded PowerPC systems compile code for
               the OpenBSD operating system.
    
           **-mtraceback=**_traceback_type_
               Select the type of traceback table. Valid values for
               _traceback_type_ are **full** , **part** , and **no**.
    
           **-maix-struct-return**
               Return all structures in memory (as specified by the AIX ABI).
    
           **-msvr4-struct-return**
               Return structures smaller than 8 bytes in registers (as
               specified by the SVR4 ABI).
    
           **-mabi=**_abi-type_
               Extend the current ABI with a particular extension, or remove
               such extension.  Valid values are **altivec** , **no-altivec** ,
               **ibmlongdouble** , **ieeelongdouble** , **elfv1** , **elfv2**.
    
           **-mabi=ibmlongdouble**
               Change the current ABI to use IBM extended-precision long
               double.  This is not likely to work if your system defaults to
               using IEEE extended-precision long double.  If you change the
               long double type from IEEE extended-precision, the compiler
               will issue a warning unless you use the **-Wno-psabi** option.
               Requires **-mlong-double-128** to be enabled.
    
           **-mabi=ieeelongdouble**
               Change the current ABI to use IEEE extended-precision long
               double.  This is not likely to work if your system defaults to
               using IBM extended-precision long double.  If you change the
               long double type from IBM extended-precision, the compiler
               will issue a warning unless you use the **-Wno-psabi** option.
               Requires **-mlong-double-128** to be enabled.
    
           **-mabi=elfv1**
               Change the current ABI to use the ELFv1 ABI.  This is the
               default ABI for big-endian PowerPC 64-bit Linux.  Overriding
               the default ABI requires special system support and is likely
               to fail in spectacular ways.
    
           **-mabi=elfv2**
               Change the current ABI to use the ELFv2 ABI.  This is the
               default ABI for little-endian PowerPC 64-bit Linux.
               Overriding the default ABI requires special system support and
               is likely to fail in spectacular ways.
    
           **-mgnu-attribute**
           **-mno-gnu-attribute**
               Emit .gnu_attribute assembly directives to set tag/value pairs
               in a .gnu.attributes section that specify ABI variations in
               function parameters or return values.
    
           **-mprototype**
           **-mno-prototype**
               On System V.4 and embedded PowerPC systems assume that all
               calls to variable argument functions are properly prototyped.
               Otherwise, the compiler must insert an instruction before
               every non-prototyped call to set or clear bit 6 of the
               condition code register ("CR") to indicate whether floating-
               point values are passed in the floating-point registers in
               case the function takes variable arguments.  With **-mprototype** ,
               only calls to prototyped variable argument functions set or
               clear the bit.
    
           **-msim**
               On embedded PowerPC systems, assume that the startup module is
               called _sim-crt0.o_ and that the standard C libraries are
               _libsim.a_ and _libc.a_.  This is the default for
               **powerpc-*-eabisim** configurations.
    
           **-mmvme**
               On embedded PowerPC systems, assume that the startup module is
               called _crt0.o_ and the standard C libraries are _libmvme.a_ and
               _libc.a_.
    
           **-mads**
               On embedded PowerPC systems, assume that the startup module is
               called _crt0.o_ and the standard C libraries are _libads.a_ and
               _libc.a_.
    
           **-myellowknife**
               On embedded PowerPC systems, assume that the startup module is
               called _crt0.o_ and the standard C libraries are _libyk.a_ and
               _libc.a_.
    
           **-mvxworks**
               On System V.4 and embedded PowerPC systems, specify that you
               are compiling for a VxWorks system.
    
           **-memb**
               On embedded PowerPC systems, set the "PPC_EMB" bit in the ELF
               flags header to indicate that **eabi** extended relocations are
               used.
    
           **-meabi**
           **-mno-eabi**
               On System V.4 and embedded PowerPC systems do (do not) adhere
               to the Embedded Applications Binary Interface (EABI), which is
               a set of modifications to the System V.4 specifications.
               Selecting **-meabi** means that the stack is aligned to an 8-byte
               boundary, a function "__eabi" is called from "main" to set up
               the EABI environment, and the **-msdata** option can use both "r2"
               and "r13" to point to two separate small data areas.
               Selecting **-mno-eabi** means that the stack is aligned to a
               16-byte boundary, no EABI initialization function is called
               from "main", and the **-msdata** option only uses "r13" to point
               to a single small data area.  The **-meabi** option is on by
               default if you configured GCC using one of the
               **powerpc*-*-eabi*** options.
    
           **-msdata=eabi**
               On System V.4 and embedded PowerPC systems, put small
               initialized "const" global and static data in the ".sdata2"
               section, which is pointed to by register "r2".  Put small
               initialized non-"const" global and static data in the ".sdata"
               section, which is pointed to by register "r13".  Put small
               uninitialized global and static data in the ".sbss" section,
               which is adjacent to the ".sdata" section.  The **-msdata=eabi**
               option is incompatible with the **-mrelocatable** option.  The
               **-msdata=eabi** option also sets the **-memb** option.
    
           **-msdata=sysv**
               On System V.4 and embedded PowerPC systems, put small global
               and static data in the ".sdata" section, which is pointed to
               by register "r13".  Put small uninitialized global and static
               data in the ".sbss" section, which is adjacent to the ".sdata"
               section.  The **-msdata=sysv** option is incompatible with the
               **-mrelocatable** option.
    
           **-msdata=default**
           **-msdata**
               On System V.4 and embedded PowerPC systems, if **-meabi** is used,
               compile code the same as **-msdata=eabi** , otherwise compile code
               the same as **-msdata=sysv**.
    
           **-msdata=data**
               On System V.4 and embedded PowerPC systems, put small global
               data in the ".sdata" section.  Put small uninitialized global
               data in the ".sbss" section.  Do not use register "r13" to
               address small data however.  This is the default behavior
               unless other **-msdata** options are used.
    
           **-msdata=none**
           **-mno-sdata**
               On embedded PowerPC systems, put all initialized global and
               static data in the ".data" section, and all uninitialized data
               in the ".bss" section.
    
           **-mreadonly-in-sdata**
               Put read-only objects in the ".sdata" section as well.  This
               is the default.
    
           **-mblock-move-inline-limit=**_num_
               Inline all block moves (such as calls to "memcpy" or structure
               copies) less than or equal to _num_ bytes.  The minimum value
               for _num_ is 32 bytes on 32-bit targets and 64 bytes on 64-bit
               targets.  The default value is target-specific.
    
           **-mblock-compare-inline-limit=**_num_
               Generate non-looping inline code for all block compares (such
               as calls to "memcmp" or structure compares) less than or equal
               to _num_ bytes. If _num_ is 0, all inline expansion (non-loop and
               loop) of block compare is disabled. The default value is
               target-specific.
    
           **-mblock-compare-inline-loop-limit=**_num_
               Generate an inline expansion using loop code for all block
               compares that are less than or equal to _num_ bytes, but greater
               than the limit for non-loop inline block compare expansion. If
               the block length is not constant, at most _num_ bytes will be
               compared before "memcmp" is called to compare the remainder of
               the block. The default value is target-specific.
    
           **-mstring-compare-inline-limit=**_num_
               Compare at most _num_ string bytes with inline code.  If the
               difference or end of string is not found at the end of the
               inline compare a call to "strcmp" or "strncmp" will take care
               of the rest of the comparison. The default is 64 bytes.
    
           **-G** _num_
               On embedded PowerPC systems, put global and static items less
               than or equal to _num_ bytes into the small data or BSS sections
               instead of the normal data or BSS section.  By default, _num_ is
               8.  The **-G** _num_ switch is also passed to the linker.  All
               modules should be compiled with the same **-G** _num_ value.
    
           **-mregnames**
           **-mno-regnames**
               On System V.4 and embedded PowerPC systems do (do not) emit
               register names in the assembly language output using symbolic
               forms.
    
           **-mlongcall**
           **-mno-longcall**
               By default assume that all calls are far away so that a longer
               and more expensive calling sequence is required.  This is
               required for calls farther than 32 megabytes (33,554,432
               bytes) from the current location.  A short call is generated
               if the compiler knows the call cannot be that far away.  This
               setting can be overridden by the "shortcall" function
               attribute, or by "#pragma longcall(0)".
    
               Some linkers are capable of detecting out-of-range calls and
               generating glue code on the fly.  On these systems, long calls
               are unnecessary and generate slower code.  As of this writing,
               the AIX linker can do this, as can the GNU linker for
               PowerPC/64.  It is planned to add this feature to the GNU
               linker for 32-bit PowerPC systems as well.
    
               On PowerPC64 ELFv2 and 32-bit PowerPC systems with newer GNU
               linkers, GCC can generate long calls using an inline PLT call
               sequence (see **-mpltseq**).  PowerPC with **-mbss-plt** and PowerPC64
               ELFv1 (big-endian) do not support inline PLT calls.
    
               On Darwin/PPC systems, "#pragma longcall" generates "jbsr
               callee, L42", plus a _branch island_ (glue code).  The two
               target addresses represent the callee and the branch island.
               The Darwin/PPC linker prefers the first address and generates
               a "bl callee" if the PPC "bl" instruction reaches the callee
               directly; otherwise, the linker generates "bl L42" to call the
               branch island.  The branch island is appended to the body of
               the calling function; it computes the full 32-bit address of
               the callee and jumps to it.
    
               On Mach-O (Darwin) systems, this option directs the compiler
               emit to the glue for every direct call, and the Darwin linker
               decides whether to use or discard it.
    
               In the future, GCC may ignore all longcall specifications when
               the linker is known to generate glue.
    
           **-mpltseq**
           **-mno-pltseq**
               Implement (do not implement) -fno-plt and long calls using an
               inline PLT call sequence that supports lazy linking and long
               calls to functions in dlopen'd shared libraries.  Inline PLT
               calls are only supported on PowerPC64 ELFv2 and 32-bit PowerPC
               systems with newer GNU linkers, and are enabled by default if
               the support is detected when configuring GCC, and, in the case
               of 32-bit PowerPC, if GCC is configured with
               **--enable-secureplt**.  **-mpltseq** code and **-mbss-plt** 32-bit
               PowerPC relocatable objects may not be linked together.
    
           **-mtls-markers**
           **-mno-tls-markers**
               Mark (do not mark) calls to "__tls_get_addr" with a relocation
               specifying the function argument.  The relocation allows the
               linker to reliably associate function call with argument setup
               instructions for TLS optimization, which in turn allows GCC to
               better schedule the sequence.
    
           **-mrecip**
           **-mno-recip**
               This option enables use of the reciprocal estimate and
               reciprocal square root estimate instructions with additional
               Newton-Raphson steps to increase precision instead of doing a
               divide or square root and divide for floating-point arguments.
               You should use the **-ffast-math** option when using **-mrecip**(or
               at least **-funsafe-math-optimizations** , **-ffinite-math-only** ,
               **-freciprocal-math** and **-fno-trapping-math**).  Note that while
               the throughput of the sequence is generally higher than the
               throughput of the non-reciprocal instruction, the precision of
               the sequence can be decreased by up to 2 ulp (i.e. the inverse
               of 1.0 equals 0.99999994) for reciprocal square roots.
    
           **-mrecip=**_opt_
               This option controls which reciprocal estimate instructions
               may be used.  _opt_ is a comma-separated list of options, which
               may be preceded by a "!" to invert the option:
    
               **all** Enable all estimate instructions.
    
               **default**
                   Enable the default instructions, equivalent to **-mrecip**.
    
               **none**
                   Disable all estimate instructions, equivalent to
                   **-mno-recip**.
    
               **div** Enable the reciprocal approximation instructions for both
                   single and double precision.
    
               **divf**
                   Enable the single-precision reciprocal approximation
                   instructions.
    
               **divd**
                   Enable the double-precision reciprocal approximation
                   instructions.
    
               **rsqrt**
                   Enable the reciprocal square root approximation
                   instructions for both single and double precision.
    
               **rsqrtf**
                   Enable the single-precision reciprocal square root
                   approximation instructions.
    
               **rsqrtd**
                   Enable the double-precision reciprocal square root
                   approximation instructions.
    
               So, for example, **-mrecip=all,!rsqrtd** enables all of the
               reciprocal estimate instructions, except for the "FRSQRTE",
               "XSRSQRTEDP", and "XVRSQRTEDP" instructions which handle the
               double-precision reciprocal square root calculations.
    
           **-mrecip-precision**
           **-mno-recip-precision**
               Assume (do not assume) that the reciprocal estimate
               instructions provide higher-precision estimates than is
               mandated by the PowerPC ABI.  Selecting **-mcpu=power6** ,
               **-mcpu=power7** or **-mcpu=power8** automatically selects
               **-mrecip-precision**.  The double-precision square root estimate
               instructions are not generated by default on low-precision
               machines, since they do not provide an estimate that converges
               after three steps.
    
           **-mveclibabi=**_type_
               Specifies the ABI type to use for vectorizing intrinsics using
               an external library.  The only type supported at present is
               **mass** , which specifies to use IBM's Mathematical Acceleration
               Subsystem (MASS) libraries for vectorizing intrinsics using
               external libraries.  GCC currently emits calls to "acosd2",
               "acosf4", "acoshd2", "acoshf4", "asind2", "asinf4", "asinhd2",
               "asinhf4", "atan2d2", "atan2f4", "atand2", "atanf4",
               "atanhd2", "atanhf4", "cbrtd2", "cbrtf4", "cosd2", "cosf4",
               "coshd2", "coshf4", "erfcd2", "erfcf4", "erfd2", "erff4",
               "exp2d2", "exp2f4", "expd2", "expf4", "expm1d2", "expm1f4",
               "hypotd2", "hypotf4", "lgammad2", "lgammaf4", "log10d2",
               "log10f4", "log1pd2", "log1pf4", "log2d2", "log2f4", "logd2",
               "logf4", "powd2", "powf4", "sind2", "sinf4", "sinhd2",
               "sinhf4", "sqrtd2", "sqrtf4", "tand2", "tanf4", "tanhd2", and
               "tanhf4" when generating code for power7.  Both
               **-ftree-vectorize** and **-funsafe-math-optimizations** must also be
               enabled.  The MASS libraries must be specified at link time.
    
           **-mfriz**
           **-mno-friz**
               Generate (do not generate) the "friz" instruction when the
               **-funsafe-math-optimizations** option is used to optimize
               rounding of floating-point values to 64-bit integer and back
               to floating point.  The "friz" instruction does not return the
               same value if the floating-point number is too large to fit in
               an integer.
    
           **-mpointers-to-nested-functions**
           **-mno-pointers-to-nested-functions**
               Generate (do not generate) code to load up the static chain
               register ("r11") when calling through a pointer on AIX and
               64-bit Linux systems where a function pointer points to a
               3-word descriptor giving the function address, TOC value to be
               loaded in register "r2", and static chain value to be loaded
               in register "r11".  The **-mpointers-to-nested-functions** is on
               by default.  You cannot call through pointers to nested
               functions or pointers to functions compiled in other languages
               that use the static chain if you use
               **-mno-pointers-to-nested-functions**.
    
           **-msave-toc-indirect**
           **-mno-save-toc-indirect**
               Generate (do not generate) code to save the TOC value in the
               reserved stack location in the function prologue if the
               function calls through a pointer on AIX and 64-bit Linux
               systems.  If the TOC value is not saved in the prologue, it is
               saved just before the call through the pointer.  The
               **-mno-save-toc-indirect** option is the default.
    
           **-mcompat-align-parm**
           **-mno-compat-align-parm**
               Generate (do not generate) code to pass structure parameters
               with a maximum alignment of 64 bits, for compatibility with
               older versions of GCC.
    
               Older versions of GCC (prior to 4.9.0) incorrectly did not
               align a structure parameter on a 128-bit boundary when that
               structure contained a member requiring 128-bit alignment.
               This is corrected in more recent versions of GCC.  This option
               may be used to generate code that is compatible with functions
               compiled with older versions of GCC.
    
               The **-mno-compat-align-parm** option is the default.
    
           **-mstack-protector-guard=**_guard_
           **-mstack-protector-guard-reg=**_reg_
           **-mstack-protector-guard-offset=**_offset_
           **-mstack-protector-guard-symbol=**_symbol_
               Generate stack protection code using canary at _guard_.
               Supported locations are **global** for global canary or **tls** for
               per-thread canary in the TLS block (the default with GNU libc
               version 2.4 or later).
    
               With the latter choice the options
               **-mstack-protector-guard-reg=**_reg_ and
               **-mstack-protector-guard-offset=**_offset_ furthermore specify
               which register to use as base register for reading the canary,
               and from what offset from that base register. The default for
               those is as specified in the relevant ABI.
               **-mstack-protector-guard-symbol=**_symbol_ overrides the offset
               with a symbol reference to a canary in the TLS block.
    
           _RX Options_
    
           These command-line options are defined for RX targets:
    
           **-m64bit-doubles**
           **-m32bit-doubles**
               Make the "double" data type be 64 bits (**-m64bit-doubles**) or 32
               bits (**-m32bit-doubles**) in size.  The default is
               **-m32bit-doubles**.  _Note_ RX floating-point hardware only works
               on 32-bit values, which is why the default is **-m32bit-doubles**.
    
           **-fpu**
           **-nofpu**
               Enables (**-fpu**) or disables (**-nofpu**) the use of RX floating-
               point hardware.  The default is enabled for the RX600 series
               and disabled for the RX200 series.
    
               Floating-point instructions are only generated for 32-bit
               floating-point values, however, so the FPU hardware is not
               used for doubles if the **-m64bit-doubles** option is used.
    
               _Note_ If the **-fpu** option is enabled then
               **-funsafe-math-optimizations** is also enabled automatically.
               This is because the RX FPU instructions are themselves unsafe.
    
           **-mcpu=**_name_
               Selects the type of RX CPU to be targeted.  Currently three
               types are supported, the generic **RX600** and **RX200** series
               hardware and the specific **RX610** CPU.  The default is **RX600**.
    
               The only difference between **RX600** and **RX610** is that the **RX610**
               does not support the "MVTIPL" instruction.
    
               The **RX200** series does not have a hardware floating-point unit
               and so **-nofpu** is enabled by default when this type is
               selected.
    
           **-mbig-endian-data**
           **-mlittle-endian-data**
               Store data (but not code) in the big-endian format.  The
               default is **-mlittle-endian-data** , i.e. to store data in the
               little-endian format.
    
           **-msmall-data-limit=**_N_
               Specifies the maximum size in bytes of global and static
               variables which can be placed into the small data area.  Using
               the small data area can lead to smaller and faster code, but
               the size of area is limited and it is up to the programmer to
               ensure that the area does not overflow.  Also when the small
               data area is used one of the RX's registers (usually "r13") is
               reserved for use pointing to this area, so it is no longer
               available for use by the compiler.  This could result in
               slower and/or larger code if variables are pushed onto the
               stack instead of being held in this register.
    
               Note, common variables (variables that have not been
               initialized) and constants are not placed into the small data
               area as they are assigned to other sections in the output
               executable.
    
               The default value is zero, which disables this feature.  Note,
               this feature is not enabled by default with higher
               optimization levels (**-O2** etc) because of the potentially
               detrimental effects of reserving a register.  It is up to the
               programmer to experiment and discover whether this feature is
               of benefit to their program.  See the description of the **-mpid**
               option for a description of how the actual register to hold
               the small data area pointer is chosen.
    
           **-msim**
           **-mno-sim**
               Use the simulator runtime.  The default is to use the libgloss
               board-specific runtime.
    
           **-mas100-syntax**
           **-mno-as100-syntax**
               When generating assembler output use a syntax that is
               compatible with Renesas's AS100 assembler.  This syntax can
               also be handled by the GAS assembler, but it has some
               restrictions so it is not generated by default.
    
           **-mmax-constant-size=**_N_
               Specifies the maximum size, in bytes, of a constant that can
               be used as an operand in a RX instruction.  Although the RX
               instruction set does allow constants of up to 4 bytes in
               length to be used in instructions, a longer value equates to a
               longer instruction.  Thus in some circumstances it can be
               beneficial to restrict the size of constants that are used in
               instructions.  Constants that are too big are instead placed
               into a constant pool and referenced via register indirection.
    
               The value _N_ can be between 0 and 4.  A value of 0 (the
               default) or 4 means that constants of any size are allowed.
    
           **-mrelax**
               Enable linker relaxation.  Linker relaxation is a process
               whereby the linker attempts to reduce the size of a program by
               finding shorter versions of various instructions.  Disabled by
               default.
    
           **-mint-register=**_N_
               Specify the number of registers to reserve for fast interrupt
               handler functions.  The value _N_ can be between 0 and 4.  A
               value of 1 means that register "r13" is reserved for the
               exclusive use of fast interrupt handlers.  A value of 2
               reserves "r13" and "r12".  A value of 3 reserves "r13", "r12"
               and "r11", and a value of 4 reserves "r13" through "r10".  A
               value of 0, the default, does not reserve any registers.
    
           **-msave-acc-in-interrupts**
               Specifies that interrupt handler functions should preserve the
               accumulator register.  This is only necessary if normal code
               might use the accumulator register, for example because it
               performs 64-bit multiplications.  The default is to ignore the
               accumulator as this makes the interrupt handlers faster.
    
           **-mpid**
           **-mno-pid**
               Enables the generation of position independent data.  When
               enabled any access to constant data is done via an offset from
               a base address held in a register.  This allows the location
               of constant data to be determined at run time without
               requiring the executable to be relocated, which is a benefit
               to embedded applications with tight memory constraints.  Data
               that can be modified is not affected by this option.
    
               Note, using this feature reserves a register, usually "r13",
               for the constant data base address.  This can result in slower
               and/or larger code, especially in complicated functions.
    
               The actual register chosen to hold the constant data base
               address depends upon whether the **-msmall-data-limit** and/or the
               **-mint-register** command-line options are enabled.  Starting
               with register "r13" and proceeding downwards, registers are
               allocated first to satisfy the requirements of **-mint-register** ,
               then **-mpid** and finally **-msmall-data-limit**.  Thus it is
               possible for the small data area register to be "r8" if both
               **-mint-register=4** and **-mpid** are specified on the command line.
    
               By default this feature is not enabled.  The default can be
               restored via the **-mno-pid** command-line option.
    
           **-mno-warn-multiple-fast-interrupts**
           **-mwarn-multiple-fast-interrupts**
               Prevents GCC from issuing a warning message if it finds more
               than one fast interrupt handler when it is compiling a file.
               The default is to issue a warning for each extra fast
               interrupt handler found, as the RX only supports one such
               interrupt.
    
           **-mallow-string-insns**
           **-mno-allow-string-insns**
               Enables or disables the use of the string manipulation
               instructions "SMOVF", "SCMPU", "SMOVB", "SMOVU", "SUNTIL"
               "SWHILE" and also the "RMPA" instruction.  These instructions
               may prefetch data, which is not safe to do if accessing an I/O
               register.  (See section 12.2.7 of the RX62N Group User's
               Manual for more information).
    
               The default is to allow these instructions, but it is not
               possible for GCC to reliably detect all circumstances where a
               string instruction might be used to access an I/O register, so
               their use cannot be disabled automatically.  Instead it is
               reliant upon the programmer to use the **-mno-allow-string-insns**
               option if their program accesses I/O space.
    
               When the instructions are enabled GCC defines the C
               preprocessor symbol "__RX_ALLOW_STRING_INSNS__", otherwise it
               defines the symbol "__RX_DISALLOW_STRING_INSNS__".
    
           **-mjsr**
           **-mno-jsr**
               Use only (or not only) "JSR" instructions to access functions.
               This option can be used when code size exceeds the range of
               "BSR" instructions.  Note that **-mno-jsr** does not mean to not
               use "JSR" but instead means that any type of branch may be
               used.
    
           _Note:_ The generic GCC command-line option **-ffixed-**_reg_ has special
           significance to the RX port when used with the "interrupt"
           function attribute.  This attribute indicates a function intended
           to process fast interrupts.  GCC ensures that it only uses the
           registers "r10", "r11", "r12" and/or "r13" and only provided that
           the normal use of the corresponding registers have been restricted
           via the **-ffixed-**_reg_ or **-mint-register** command-line options.
    
           _S/390 and zSeries Options_
    
           These are the **-m** options defined for the S/390 and zSeries
           architecture.
    
           **-mhard-float**
           **-msoft-float**
               Use (do not use) the hardware floating-point instructions and
               registers for floating-point operations.  When **-msoft-float** is
               specified, functions in _libgcc.a_ are used to perform floating-
               point operations.  When **-mhard-float** is specified, the
               compiler generates IEEE floating-point instructions.  This is
               the default.
    
           **-mhard-dfp**
           **-mno-hard-dfp**
               Use (do not use) the hardware decimal-floating-point
               instructions for decimal-floating-point operations.  When
               **-mno-hard-dfp** is specified, functions in _libgcc.a_ are used to
               perform decimal-floating-point operations.  When **-mhard-dfp** is
               specified, the compiler generates decimal-floating-point
               hardware instructions.  This is the default for **-march=z9-ec**
               or higher.
    
           **-mlong-double-64**
           **-mlong-double-128**
               These switches control the size of "long double" type. A size
               of 64 bits makes the "long double" type equivalent to the
               "double" type. This is the default.
    
           **-mbackchain**
           **-mno-backchain**
               Store (do not store) the address of the caller's frame as
               backchain pointer into the callee's stack frame.  A backchain
               may be needed to allow debugging using tools that do not
               understand DWARF call frame information.  When
               **-mno-packed-stack** is in effect, the backchain pointer is
               stored at the bottom of the stack frame; when **-mpacked-stack**
               is in effect, the backchain is placed into the topmost word of
               the 96/160 byte register save area.
    
               In general, code compiled with **-mbackchain** is call-compatible
               with code compiled with **-mmo-backchain** ; however, use of the
               backchain for debugging purposes usually requires that the
               whole binary is built with **-mbackchain**.  Note that the
               combination of **-mbackchain** , **-mpacked-stack** and **-mhard-float** is
               not supported.  In order to build a linux kernel use
               **-msoft-float**.
    
               The default is to not maintain the backchain.
    
           **-mpacked-stack**
           **-mno-packed-stack**
               Use (do not use) the packed stack layout.  When
               **-mno-packed-stack** is specified, the compiler uses the all
               fields of the 96/160 byte register save area only for their
               default purpose; unused fields still take up stack space.
               When **-mpacked-stack** is specified, register save slots are
               densely packed at the top of the register save area; unused
               space is reused for other purposes, allowing for more
               efficient use of the available stack space.  However, when
               **-mbackchain** is also in effect, the topmost word of the save
               area is always used to store the backchain, and the return
               address register is always saved two words below the
               backchain.
    
               As long as the stack frame backchain is not used, code
               generated with **-mpacked-stack** is call-compatible with code
               generated with **-mno-packed-stack**.  Note that some non-FSF
               releases of GCC 2.95 for S/390 or zSeries generated code that
               uses the stack frame backchain at run time, not just for
               debugging purposes.  Such code is not call-compatible with
               code compiled with **-mpacked-stack**.  Also, note that the
               combination of **-mbackchain** , **-mpacked-stack** and **-mhard-float** is
               not supported.  In order to build a linux kernel use
               **-msoft-float**.
    
               The default is to not use the packed stack layout.
    
           **-msmall-exec**
           **-mno-small-exec**
               Generate (or do not generate) code using the "bras"
               instruction to do subroutine calls.  This only works reliably
               if the total executable size does not exceed 64k.  The default
               is to use the "basr" instruction instead, which does not have
               this limitation.
    
           **-m64**
           **-m31**
               When **-m31** is specified, generate code compliant to the
               GNU/Linux for S/390 ABI.  When **-m64** is specified, generate
               code compliant to the GNU/Linux for zSeries ABI.  This allows
               GCC in particular to generate 64-bit instructions.  For the
               **s390** targets, the default is **-m31** , while the **s390x** targets
               default to **-m64**.
    
           **-mzarch**
           **-mesa**
               When **-mzarch** is specified, generate code using the
               instructions available on z/Architecture.  When **-mesa** is
               specified, generate code using the instructions available on
               ESA/390.  Note that **-mesa** is not possible with **-m64**.  When
               generating code compliant to the GNU/Linux for S/390 ABI, the
               default is **-mesa**.  When generating code compliant to the
               GNU/Linux for zSeries ABI, the default is **-mzarch**.
    
           **-mhtm**
           **-mno-htm**
               The **-mhtm** option enables a set of builtins making use of
               instructions available with the transactional execution
               facility introduced with the IBM zEnterprise EC12 machine
               generation **S/390 System z Built-in Functions**.  **-mhtm** is
               enabled by default when using **-march=zEC12**.
    
           **-mvx**
           **-mno-vx**
               When **-mvx** is specified, generate code using the instructions
               available with the vector extension facility introduced with
               the IBM z13 machine generation.  This option changes the ABI
               for some vector type values with regard to alignment and
               calling conventions.  In case vector type values are being
               used in an ABI-relevant context a GAS **.gnu_attribute** command
               will be added to mark the resulting binary with the ABI used.
               **-mvx** is enabled by default when using **-march=z13**.
    
           **-mzvector**
           **-mno-zvector**
               The **-mzvector** option enables vector language extensions and
               builtins using instructions available with the vector
               extension facility introduced with the IBM z13 machine
               generation.  This option adds support for **vector** to be used as
               a keyword to define vector type variables and arguments.
               **vector** is only available when GNU extensions are enabled.  It
               will not be expanded when requesting strict standard
               compliance e.g. with **-std=c99**.  In addition to the GCC low-
               level builtins **-mzvector** enables a set of builtins added for
               compatibility with AltiVec-style implementations like Power
               and Cell.  In order to make use of these builtins the header
               file _vecintrin.h_ needs to be included.  **-mzvector** is disabled
               by default.
    
           **-mmvcle**
           **-mno-mvcle**
               Generate (or do not generate) code using the "mvcle"
               instruction to perform block moves.  When **-mno-mvcle** is
               specified, use a "mvc" loop instead.  This is the default
               unless optimizing for size.
    
           **-mdebug**
           **-mno-debug**
               Print (or do not print) additional debug information when
               compiling.  The default is to not print debug information.
    
           **-march=**_cpu-type_
               Generate code that runs on _cpu-type_ , which is the name of a
               system representing a certain processor type.  Possible values
               for _cpu-type_ are **z900** /**arch5** , **z990** /**arch6** , **z9-109** , **z9-ec** /**arch7** ,
               **z10** /**arch8** , **z196** /**arch9** , **zEC12** , **z13** /**arch11** , **z14** /**arch12** , and
               **native**.
    
               The default is **-march=z900**.
    
               Specifying **native** as cpu type can be used to select the best
               architecture option for the host processor.  **-march=native** has
               no effect if GCC does not recognize the processor.
    
           **-mtune=**_cpu-type_
               Tune to _cpu-type_ everything applicable about the generated
               code, except for the ABI and the set of available
               instructions.  The list of _cpu-type_ values is the same as for
               **-march**.  The default is the value used for **-march**.
    
           **-mtpf-trace**
           **-mno-tpf-trace**
               Generate code that adds (does not add) in TPF OS specific
               branches to trace routines in the operating system.  This
               option is off by default, even when compiling for the TPF OS.
    
           **-mfused-madd**
           **-mno-fused-madd**
               Generate code that uses (does not use) the floating-point
               multiply and accumulate instructions.  These instructions are
               generated by default if hardware floating point is used.
    
           **-mwarn-framesize=**_framesize_
               Emit a warning if the current function exceeds the given frame
               size.  Because this is a compile-time check it doesn't need to
               be a real problem when the program runs.  It is intended to
               identify functions that most probably cause a stack overflow.
               It is useful to be used in an environment with limited stack
               size e.g. the linux kernel.
    
           **-mwarn-dynamicstack**
               Emit a warning if the function calls "alloca" or uses
               dynamically-sized arrays.  This is generally a bad idea with a
               limited stack size.
    
           **-mstack-guard=**_stack-guard_
           **-mstack-size=**_stack-size_
               If these options are provided the S/390 back end emits
               additional instructions in the function prologue that trigger
               a trap if the stack size is _stack-guard_ bytes above the _stack-_
               _size_ (remember that the stack on S/390 grows downward).  If
               the _stack-guard_ option is omitted the smallest power of 2
               larger than the frame size of the compiled function is chosen.
               These options are intended to be used to help debugging stack
               overflow problems.  The additionally emitted code causes only
               little overhead and hence can also be used in production-like
               systems without greater performance degradation.  The given
               values have to be exact powers of 2 and _stack-size_ has to be
               greater than _stack-guard_ without exceeding 64k.  In order to
               be efficient the extra code makes the assumption that the
               stack starts at an address aligned to the value given by
               _stack-size_.  The _stack-guard_ option can only be used in
               conjunction with _stack-size_.
    
           **-mhotpatch=**_pre-halfwords_**,**_post-halfwords_
               If the hotpatch option is enabled, a "hot-patching" function
               prologue is generated for all functions in the compilation
               unit.  The funtion label is prepended with the given number of
               two-byte NOP instructions (_pre-halfwords_ , maximum 1000000).
               After the label, 2 * _post-halfwords_ bytes are appended, using
               the largest NOP like instructions the architecture allows
               (maximum 1000000).
    
               If both arguments are zero, hotpatching is disabled.
    
               This option can be overridden for individual functions with
               the "hotpatch" attribute.
    
           _Score Options_
    
           These options are defined for Score implementations:
    
           **-meb**
               Compile code for big-endian mode.  This is the default.
    
           **-mel**
               Compile code for little-endian mode.
    
           **-mnhwloop**
               Disable generation of "bcnz" instructions.
    
           **-muls**
               Enable generation of unaligned load and store instructions.
    
           **-mmac**
               Enable the use of multiply-accumulate instructions. Disabled
               by default.
    
           **-mscore5**
               Specify the SCORE5 as the target architecture.
    
           **-mscore5u**
               Specify the SCORE5U of the target architecture.
    
           **-mscore7**
               Specify the SCORE7 as the target architecture. This is the
               default.
    
           **-mscore7d**
               Specify the SCORE7D as the target architecture.
    
           _SH Options_
    
           These **-m** options are defined for the SH implementations:
    
           **-m1** Generate code for the SH1.
    
           **-m2** Generate code for the SH2.
    
           **-m2e**
               Generate code for the SH2e.
    
           **-m2a-nofpu**
               Generate code for the SH2a without FPU, or for a SH2a-FPU in
               such a way that the floating-point unit is not used.
    
           **-m2a-single-only**
               Generate code for the SH2a-FPU, in such a way that no double-
               precision floating-point operations are used.
    
           **-m2a-single**
               Generate code for the SH2a-FPU assuming the floating-point
               unit is in single-precision mode by default.
    
           **-m2a**
               Generate code for the SH2a-FPU assuming the floating-point
               unit is in double-precision mode by default.
    
           **-m3** Generate code for the SH3.
    
           **-m3e**
               Generate code for the SH3e.
    
           **-m4-nofpu**
               Generate code for the SH4 without a floating-point unit.
    
           **-m4-single-only**
               Generate code for the SH4 with a floating-point unit that only
               supports single-precision arithmetic.
    
           **-m4-single**
               Generate code for the SH4 assuming the floating-point unit is
               in single-precision mode by default.
    
           **-m4** Generate code for the SH4.
    
           **-m4-100**
               Generate code for SH4-100.
    
           **-m4-100-nofpu**
               Generate code for SH4-100 in such a way that the floating-
               point unit is not used.
    
           **-m4-100-single**
               Generate code for SH4-100 assuming the floating-point unit is
               in single-precision mode by default.
    
           **-m4-100-single-only**
               Generate code for SH4-100 in such a way that no double-
               precision floating-point operations are used.
    
           **-m4-200**
               Generate code for SH4-200.
    
           **-m4-200-nofpu**
               Generate code for SH4-200 without in such a way that the
               floating-point unit is not used.
    
           **-m4-200-single**
               Generate code for SH4-200 assuming the floating-point unit is
               in single-precision mode by default.
    
           **-m4-200-single-only**
               Generate code for SH4-200 in such a way that no double-
               precision floating-point operations are used.
    
           **-m4-300**
               Generate code for SH4-300.
    
           **-m4-300-nofpu**
               Generate code for SH4-300 without in such a way that the
               floating-point unit is not used.
    
           **-m4-300-single**
               Generate code for SH4-300 in such a way that no double-
               precision floating-point operations are used.
    
           **-m4-300-single-only**
               Generate code for SH4-300 in such a way that no double-
               precision floating-point operations are used.
    
           **-m4-340**
               Generate code for SH4-340 (no MMU, no FPU).
    
           **-m4-500**
               Generate code for SH4-500 (no FPU).  Passes **-isa=sh4-nofpu** to
               the assembler.
    
           **-m4a-nofpu**
               Generate code for the SH4al-dsp, or for a SH4a in such a way
               that the floating-point unit is not used.
    
           **-m4a-single-only**
               Generate code for the SH4a, in such a way that no double-
               precision floating-point operations are used.
    
           **-m4a-single**
               Generate code for the SH4a assuming the floating-point unit is
               in single-precision mode by default.
    
           **-m4a**
               Generate code for the SH4a.
    
           **-m4al**
               Same as **-m4a-nofpu** , except that it implicitly passes **-dsp** to
               the assembler.  GCC doesn't generate any DSP instructions at
               the moment.
    
           **-mb** Compile code for the processor in big-endian mode.
    
           **-ml** Compile code for the processor in little-endian mode.
    
           **-mdalign**
               Align doubles at 64-bit boundaries.  Note that this changes
               the calling conventions, and thus some functions from the
               standard C library do not work unless you recompile it first
               with **-mdalign**.
    
           **-mrelax**
               Shorten some address references at link time, when possible;
               uses the linker option **-relax**.
    
           **-mbigtable**
               Use 32-bit offsets in "switch" tables.  The default is to use
               16-bit offsets.
    
           **-mbitops**
               Enable the use of bit manipulation instructions on SH2A.
    
           **-mfmovd**
               Enable the use of the instruction "fmovd".  Check **-mdalign** for
               alignment constraints.
    
           **-mrenesas**
               Comply with the calling conventions defined by Renesas.
    
           **-mno-renesas**
               Comply with the calling conventions defined for GCC before the
               Renesas conventions were available.  This option is the
               default for all targets of the SH toolchain.
    
           **-mnomacsave**
               Mark the "MAC" register as call-clobbered, even if **-mrenesas**
               is given.
    
           **-mieee**
           **-mno-ieee**
               Control the IEEE compliance of floating-point comparisons,
               which affects the handling of cases where the result of a
               comparison is unordered.  By default **-mieee** is implicitly
               enabled.  If **-ffinite-math-only** is enabled **-mno-ieee** is
               implicitly set, which results in faster floating-point
               greater-equal and less-equal comparisons.  The implicit
               settings can be overridden by specifying either **-mieee** or
               **-mno-ieee**.
    
           **-minline-ic_invalidate**
               Inline code to invalidate instruction cache entries after
               setting up nested function trampolines.  This option has no
               effect if **-musermode** is in effect and the selected code
               generation option (e.g. **-m4**) does not allow the use of the
               "icbi" instruction.  If the selected code generation option
               does not allow the use of the "icbi" instruction, and
               **-musermode** is not in effect, the inlined code manipulates the
               instruction cache address array directly with an associative
               write.  This not only requires privileged mode at run time,
               but it also fails if the cache line had been mapped via the
               TLB and has become unmapped.
    
           **-misize**
               Dump instruction size and location in the assembly code.
    
           **-mpadstruct**
               This option is deprecated.  It pads structures to multiple of
               4 bytes, which is incompatible with the SH ABI.
    
           **-matomic-model=**_model_
               Sets the model of atomic operations and additional parameters
               as a comma separated list.  For details on the atomic built-in
               functions see **__atomic Builtins**.  The following models and
               parameters are supported:
    
               **none**
                   Disable compiler generated atomic sequences and emit
                   library calls for atomic operations.  This is the default
                   if the target is not "sh*-*-linux*".
    
               **soft-gusa**
                   Generate GNU/Linux compatible gUSA software atomic
                   sequences for the atomic built-in functions.  The
                   generated atomic sequences require additional support from
                   the interrupt/exception handling code of the system and
                   are only suitable for SH3* and SH4* single-core systems.
                   This option is enabled by default when the target is
                   "sh*-*-linux*" and SH3* or SH4*.  When the target is SH4A,
                   this option also partially utilizes the hardware atomic
                   instructions "movli.l" and "movco.l" to create more
                   efficient code, unless **strict** is specified.
    
               **soft-tcb**
                   Generate software atomic sequences that use a variable in
                   the thread control block.  This is a variation of the gUSA
                   sequences which can also be used on SH1* and SH2* targets.
                   The generated atomic sequences require additional support
                   from the interrupt/exception handling code of the system
                   and are only suitable for single-core systems.  When using
                   this model, the **gbr-offset=** parameter has to be specified
                   as well.
    
               **soft-imask**
                   Generate software atomic sequences that temporarily
                   disable interrupts by setting "SR.IMASK = 1111".  This
                   model works only when the program runs in privileged mode
                   and is only suitable for single-core systems.  Additional
                   support from the interrupt/exception handling code of the
                   system is not required.  This model is enabled by default
                   when the target is "sh*-*-linux*" and SH1* or SH2*.
    
               **hard-llcs**
                   Generate hardware atomic sequences using the "movli.l" and
                   "movco.l" instructions only.  This is only available on
                   SH4A and is suitable for multi-core systems.  Since the
                   hardware instructions support only 32 bit atomic variables
                   access to 8 or 16 bit variables is emulated with 32 bit
                   accesses.  Code compiled with this option is also
                   compatible with other software atomic model
                   interrupt/exception handling systems if executed on an
                   SH4A system.  Additional support from the
                   interrupt/exception handling code of the system is not
                   required for this model.
    
               **gbr-offset=**
                   This parameter specifies the offset in bytes of the
                   variable in the thread control block structure that should
                   be used by the generated atomic sequences when the **soft-**
                   **tcb** model has been selected.  For other models this
                   parameter is ignored.  The specified value must be an
                   integer multiple of four and in the range 0-1020.
    
               **strict**
                   This parameter prevents mixed usage of multiple atomic
                   models, even if they are compatible, and makes the
                   compiler generate atomic sequences of the specified model
                   only.
    
           **-mtas**
               Generate the "tas.b" opcode for "__atomic_test_and_set".
               Notice that depending on the particular hardware and software
               configuration this can degrade overall performance due to the
               operand cache line flushes that are implied by the "tas.b"
               instruction.  On multi-core SH4A processors the "tas.b"
               instruction must be used with caution since it can result in
               data corruption for certain cache configurations.
    
           **-mprefergot**
               When generating position-independent code, emit function calls
               using the Global Offset Table instead of the Procedure Linkage
               Table.
    
           **-musermode**
           **-mno-usermode**
               Don't allow (allow) the compiler generating privileged mode
               code.  Specifying **-musermode** also implies
               **-mno-inline-ic_invalidate** if the inlined code would not work
               in user mode.  **-musermode** is the default when the target is
               "sh*-*-linux*".  If the target is SH1* or SH2* **-musermode** has
               no effect, since there is no user mode.
    
           **-multcost=**_number_
               Set the cost to assume for a multiply insn.
    
           **-mdiv=**_strategy_
               Set the division strategy to be used for integer division
               operations.  _strategy_ can be one of:
    
               **call-div1**
                   Calls a library function that uses the single-step
                   division instruction "div1" to perform the operation.
                   Division by zero calculates an unspecified result and does
                   not trap.  This is the default except for SH4, SH2A and
                   SHcompact.
    
               **call-fp**
                   Calls a library function that performs the operation in
                   double precision floating point.  Division by zero causes
                   a floating-point exception.  This is the default for
                   SHcompact with FPU.  Specifying this for targets that do
                   not have a double precision FPU defaults to "call-div1".
    
               **call-table**
                   Calls a library function that uses a lookup table for
                   small divisors and the "div1" instruction with case
                   distinction for larger divisors.  Division by zero
                   calculates an unspecified result and does not trap.  This
                   is the default for SH4.  Specifying this for targets that
                   do not have dynamic shift instructions defaults to
                   "call-div1".
    
               When a division strategy has not been specified the default
               strategy is selected based on the current target.  For SH2A
               the default strategy is to use the "divs" and "divu"
               instructions instead of library function calls.
    
           **-maccumulate-outgoing-args**
               Reserve space once for outgoing arguments in the function
               prologue rather than around each call.  Generally beneficial
               for performance and size.  Also needed for unwinding to avoid
               changing the stack frame around conditional code.
    
           **-mdivsi3_libfunc=**_name_
               Set the name of the library function used for 32-bit signed
               division to _name_.  This only affects the name used in the **call**
               division strategies, and the compiler still expects the same
               sets of input/output/clobbered registers as if this option
               were not present.
    
           **-mfixed-range=**_register-range_
               Generate code treating the given register range as fixed
               registers.  A fixed register is one that the register
               allocator cannot use.  This is useful when compiling kernel
               code.  A register range is specified as two registers
               separated by a dash.  Multiple register ranges can be
               specified separated by a comma.
    
           **-mbranch-cost=**_num_
               Assume _num_ to be the cost for a branch instruction.  Higher
               numbers make the compiler try to generate more branch-free
               code if possible.  If not specified the value is selected
               depending on the processor type that is being compiled for.
    
           **-mzdcbranch**
           **-mno-zdcbranch**
               Assume (do not assume) that zero displacement conditional
               branch instructions "bt" and "bf" are fast.  If **-mzdcbranch** is
               specified, the compiler prefers zero displacement branch code
               sequences.  This is enabled by default when generating code
               for SH4 and SH4A.  It can be explicitly disabled by specifying
               **-mno-zdcbranch**.
    
           **-mcbranch-force-delay-slot**
               Force the usage of delay slots for conditional branches, which
               stuffs the delay slot with a "nop" if a suitable instruction
               cannot be found.  By default this option is disabled.  It can
               be enabled to work around hardware bugs as found in the
               original SH7055.
    
           **-mfused-madd**
           **-mno-fused-madd**
               Generate code that uses (does not use) the floating-point
               multiply and accumulate instructions.  These instructions are
               generated by default if hardware floating point is used.  The
               machine-dependent **-mfused-madd** option is now mapped to the
               machine-independent **-ffp-contract=fast** option, and
               **-mno-fused-madd** is mapped to **-ffp-contract=off**.
    
           **-mfsca**
           **-mno-fsca**
               Allow or disallow the compiler to emit the "fsca" instruction
               for sine and cosine approximations.  The option **-mfsca** must be
               used in combination with **-funsafe-math-optimizations**.  It is
               enabled by default when generating code for SH4A.  Using
               **-mno-fsca** disables sine and cosine approximations even if
               **-funsafe-math-optimizations** is in effect.
    
           **-mfsrra**
           **-mno-fsrra**
               Allow or disallow the compiler to emit the "fsrra" instruction
               for reciprocal square root approximations.  The option **-mfsrra**
               must be used in combination with **-funsafe-math-optimizations**
               and **-ffinite-math-only**.  It is enabled by default when
               generating code for SH4A.  Using **-mno-fsrra** disables
               reciprocal square root approximations even if
               **-funsafe-math-optimizations** and **-ffinite-math-only** are in
               effect.
    
           **-mpretend-cmove**
               Prefer zero-displacement conditional branches for conditional
               move instruction patterns.  This can result in faster code on
               the SH4 processor.
    
           **-mfdpic**
               Generate code using the FDPIC ABI.
    
           _Solaris 2 Options_
    
           These **-m** options are supported on Solaris 2:
    
           **-mclear-hwcap**
               **-mclear-hwcap** tells the compiler to remove the hardware
               capabilities generated by the Solaris assembler.  This is only
               necessary when object files use ISA extensions not supported
               by the current machine, but check at runtime whether or not to
               use them.
    
           **-mimpure-text**
               **-mimpure-text** , used in addition to **-shared** , tells the compiler
               to not pass **-z text** to the linker when linking a shared
               object.  Using this option, you can link position-dependent
               code into a shared object.
    
               **-mimpure-text** suppresses the "relocations remain against
               allocatable but non-writable sections" linker error message.
               However, the necessary relocations trigger copy-on-write, and
               the shared object is not actually shared across processes.
               Instead of using **-mimpure-text** , you should compile all source
               code with **-fpic** or **-fPIC**.
    
           These switches are supported in addition to the above on Solaris
           2:
    
           **-pthreads**
               This is a synonym for **-pthread**.
    
           _SPARC Options_
    
           These **-m** options are supported on the SPARC:
    
           **-mno-app-regs**
           **-mapp-regs**
               Specify **-mapp-regs** to generate output using the global
               registers 2 through 4, which the SPARC SVR4 ABI reserves for
               applications.  Like the global register 1, each global
               register 2 through 4 is then treated as an allocable register
               that is clobbered by function calls.  This is the default.
    
               To be fully SVR4 ABI-compliant at the cost of some performance
               loss, specify **-mno-app-regs**.  You should compile libraries and
               system software with this option.
    
           **-mflat**
           **-mno-flat**
               With **-mflat** , the compiler does not generate save/restore
               instructions and uses a "flat" or single register window
               model.  This model is compatible with the regular register
               window model.  The local registers and the input registers
               (0--5) are still treated as "call-saved" registers and are
               saved on the stack as needed.
    
               With **-mno-flat**(the default), the compiler generates
               save/restore instructions (except for leaf functions).  This
               is the normal operating mode.
    
           **-mfpu**
           **-mhard-float**
               Generate output containing floating-point instructions.  This
               is the default.
    
           **-mno-fpu**
           **-msoft-float**
               Generate output containing library calls for floating point.
               **Warning:** the requisite libraries are not available for all
               SPARC targets.  Normally the facilities of the machine's usual
               C compiler are used, but this cannot be done directly in
               cross-compilation.  You must make your own arrangements to
               provide suitable library functions for cross-compilation.  The
               embedded targets **sparc-*-aout** and **sparclite-*-*** do provide
               software floating-point support.
    
               **-msoft-float** changes the calling convention in the output
               file; therefore, it is only useful if you compile _all_ of a
               program with this option.  In particular, you need to compile
               _libgcc.a_ , the library that comes with GCC, with **-msoft-float**
               in order for this to work.
    
           **-mhard-quad-float**
               Generate output containing quad-word (long double) floating-
               point instructions.
    
           **-msoft-quad-float**
               Generate output containing library calls for quad-word (long
               double) floating-point instructions.  The functions called are
               those specified in the SPARC ABI.  This is the default.
    
               As of this writing, there are no SPARC implementations that
               have hardware support for the quad-word floating-point
               instructions.  They all invoke a trap handler for one of these
               instructions, and then the trap handler emulates the effect of
               the instruction.  Because of the trap handler overhead, this
               is much slower than calling the ABI library routines.  Thus
               the **-msoft-quad-float** option is the default.
    
           **-mno-unaligned-doubles**
           **-munaligned-doubles**
               Assume that doubles have 8-byte alignment.  This is the
               default.
    
               With **-munaligned-doubles** , GCC assumes that doubles have 8-byte
               alignment only if they are contained in another type, or if
               they have an absolute address.  Otherwise, it assumes they
               have 4-byte alignment.  Specifying this option avoids some
               rare compatibility problems with code generated by other
               compilers.  It is not the default because it results in a
               performance loss, especially for floating-point code.
    
           **-muser-mode**
           **-mno-user-mode**
               Do not generate code that can only run in supervisor mode.
               This is relevant only for the "casa" instruction emitted for
               the LEON3 processor.  This is the default.
    
           **-mfaster-structs**
           **-mno-faster-structs**
               With **-mfaster-structs** , the compiler assumes that structures
               should have 8-byte alignment.  This enables the use of pairs
               of "ldd" and "std" instructions for copies in structure
               assignment, in place of twice as many "ld" and "st" pairs.
               However, the use of this changed alignment directly violates
               the SPARC ABI.  Thus, it's intended only for use on targets
               where the developer acknowledges that their resulting code is
               not directly in line with the rules of the ABI.
    
           **-mstd-struct-return**
           **-mno-std-struct-return**
               With **-mstd-struct-return** , the compiler generates checking code
               in functions returning structures or unions to detect size
               mismatches between the two sides of function calls, as per the
               32-bit ABI.
    
               The default is **-mno-std-struct-return**.  This option has no
               effect in 64-bit mode.
    
           **-mlra**
           **-mno-lra**
               Enable Local Register Allocation.  This is the default for
               SPARC since GCC 7 so **-mno-lra** needs to be passed to get old
               Reload.
    
           **-mcpu=**_cpu_type_
               Set the instruction set, register set, and instruction
               scheduling parameters for machine type _cpu_type_.  Supported
               values for _cpu_type_ are **v7** , **cypress** , **v8** , **supersparc** ,
               **hypersparc** , **leon** , **leon3** , **leon3v7** , **sparclite** , **f930** , **f934** ,
               **sparclite86x** , **sparclet** , **tsc701** , **v9** , **ultrasparc** , **ultrasparc3** ,
               **niagara** , **niagara2** , **niagara3** , **niagara4** , **niagara7** and **m8**.
    
               Native Solaris and GNU/Linux toolchains also support the value
               **native** , which selects the best architecture option for the
               host processor.  **-mcpu=native** has no effect if GCC does not
               recognize the processor.
    
               Default instruction scheduling parameters are used for values
               that select an architecture and not an implementation.  These
               are **v7** , **v8** , **sparclite** , **sparclet** , **v9**.
    
               Here is a list of each supported architecture and their
               supported implementations.
    
               v7  cypress, leon3v7
    
               v8  supersparc, hypersparc, leon, leon3
    
               sparclite
                   f930, f934, sparclite86x
    
               sparclet
                   tsc701
    
               v9  ultrasparc, ultrasparc3, niagara, niagara2, niagara3,
                   niagara4, niagara7, m8
    
               By default (unless configured otherwise), GCC generates code
               for the V7 variant of the SPARC architecture.  With
               **-mcpu=cypress** , the compiler additionally optimizes it for the
               Cypress CY7C602 chip, as used in the SPARCStation/SPARCServer
               3xx series.  This is also appropriate for the older
               SPARCStation 1, 2, IPX etc.
    
               With **-mcpu=v8** , GCC generates code for the V8 variant of the
               SPARC architecture.  The only difference from V7 code is that
               the compiler emits the integer multiply and integer divide
               instructions which exist in SPARC-V8 but not in SPARC-V7.
               With **-mcpu=supersparc** , the compiler additionally optimizes it
               for the SuperSPARC chip, as used in the SPARCStation 10, 1000
               and 2000 series.
    
               With **-mcpu=sparclite** , GCC generates code for the SPARClite
               variant of the SPARC architecture.  This adds the integer
               multiply, integer divide step and scan ("ffs") instructions
               which exist in SPARClite but not in SPARC-V7.  With
               **-mcpu=f930** , the compiler additionally optimizes it for the
               Fujitsu MB86930 chip, which is the original SPARClite, with no
               FPU.  With **-mcpu=f934** , the compiler additionally optimizes it
               for the Fujitsu MB86934 chip, which is the more recent
               SPARClite with FPU.
    
               With **-mcpu=sparclet** , GCC generates code for the SPARClet
               variant of the SPARC architecture.  This adds the integer
               multiply, multiply/accumulate, integer divide step and scan
               ("ffs") instructions which exist in SPARClet but not in
               SPARC-V7.  With **-mcpu=tsc701** , the compiler additionally
               optimizes it for the TEMIC SPARClet chip.
    
               With **-mcpu=v9** , GCC generates code for the V9 variant of the
               SPARC architecture.  This adds 64-bit integer and floating-
               point move instructions, 3 additional floating-point condition
               code registers and conditional move instructions.  With
               **-mcpu=ultrasparc** , the compiler additionally optimizes it for
               the Sun UltraSPARC I/II/IIi chips.  With **-mcpu=ultrasparc3** ,
               the compiler additionally optimizes it for the Sun UltraSPARC
               III/III+/IIIi/IIIi+/IV/IV+ chips.  With **-mcpu=niagara** , the
               compiler additionally optimizes it for Sun UltraSPARC T1
               chips.  With **-mcpu=niagara2** , the compiler additionally
               optimizes it for Sun UltraSPARC T2 chips. With **-mcpu=niagara3** ,
               the compiler additionally optimizes it for Sun UltraSPARC T3
               chips.  With **-mcpu=niagara4** , the compiler additionally
               optimizes it for Sun UltraSPARC T4 chips.  With
               **-mcpu=niagara7** , the compiler additionally optimizes it for
               Oracle SPARC M7 chips.  With **-mcpu=m8** , the compiler
               additionally optimizes it for Oracle M8 chips.
    
           **-mtune=**_cpu_type_
               Set the instruction scheduling parameters for machine type
               _cpu_type_ , but do not set the instruction set or register set
               that the option **-mcpu=**_cpu_type_ does.
    
               The same values for **-mcpu=**_cpu_type_ can be used for
               **-mtune=**_cpu_type_ , but the only useful values are those that
               select a particular CPU implementation.  Those are **cypress** ,
               **supersparc** , **hypersparc** , **leon** , **leon3** , **leon3v7** , **f930** , **f934** ,
               **sparclite86x** , **tsc701** , **ultrasparc** , **ultrasparc3** , **niagara** ,
               **niagara2** , **niagara3** , **niagara4** , **niagara7** and **m8**.  With native
               Solaris and GNU/Linux toolchains, **native** can also be used.
    
           **-mv8plus**
           **-mno-v8plus**
               With **-mv8plus** , GCC generates code for the SPARC-V8+ ABI.  The
               difference from the V8 ABI is that the global and out
               registers are considered 64 bits wide.  This is enabled by
               default on Solaris in 32-bit mode for all SPARC-V9 processors.
    
           **-mvis**
           **-mno-vis**
               With **-mvis** , GCC generates code that takes advantage of the
               UltraSPARC Visual Instruction Set extensions.  The default is
               **-mno-vis**.
    
           **-mvis2**
           **-mno-vis2**
               With **-mvis2** , GCC generates code that takes advantage of
               version 2.0 of the UltraSPARC Visual Instruction Set
               extensions.  The default is **-mvis2** when targeting a cpu that
               supports such instructions, such as UltraSPARC-III and later.
               Setting **-mvis2** also sets **-mvis**.
    
           **-mvis3**
           **-mno-vis3**
               With **-mvis3** , GCC generates code that takes advantage of
               version 3.0 of the UltraSPARC Visual Instruction Set
               extensions.  The default is **-mvis3** when targeting a cpu that
               supports such instructions, such as niagara-3 and later.
               Setting **-mvis3** also sets **-mvis2** and **-mvis**.
    
           **-mvis4**
           **-mno-vis4**
               With **-mvis4** , GCC generates code that takes advantage of
               version 4.0 of the UltraSPARC Visual Instruction Set
               extensions.  The default is **-mvis4** when targeting a cpu that
               supports such instructions, such as niagara-7 and later.
               Setting **-mvis4** also sets **-mvis3** , **-mvis2** and **-mvis**.
    
           **-mvis4b**
           **-mno-vis4b**
               With **-mvis4b** , GCC generates code that takes advantage of
               version 4.0 of the UltraSPARC Visual Instruction Set
               extensions, plus the additional VIS instructions introduced in
               the Oracle SPARC Architecture 2017.  The default is **-mvis4b**
               when targeting a cpu that supports such instructions, such as
               m8 and later.  Setting **-mvis4b** also sets **-mvis4** , **-mvis3** ,
               **-mvis2** and **-mvis**.
    
           **-mcbcond**
           **-mno-cbcond**
               With **-mcbcond** , GCC generates code that takes advantage of the
               UltraSPARC Compare-and-Branch-on-Condition instructions.  The
               default is **-mcbcond** when targeting a CPU that supports such
               instructions, such as Niagara-4 and later.
    
           **-mfmaf**
           **-mno-fmaf**
               With **-mfmaf** , GCC generates code that takes advantage of the
               UltraSPARC Fused Multiply-Add Floating-point instructions.
               The default is **-mfmaf** when targeting a CPU that supports such
               instructions, such as Niagara-3 and later.
    
           **-mfsmuld**
           **-mno-fsmuld**
               With **-mfsmuld** , GCC generates code that takes advantage of the
               Floating-point Multiply Single to Double (FsMULd) instruction.
               The default is **-mfsmuld** when targeting a CPU supporting the
               architecture versions V8 or V9 with FPU except **-mcpu=leon**.
    
           **-mpopc**
           **-mno-popc**
               With **-mpopc** , GCC generates code that takes advantage of the
               UltraSPARC Population Count instruction.  The default is
               **-mpopc** when targeting a CPU that supports such an instruction,
               such as Niagara-2 and later.
    
           **-msubxc**
           **-mno-subxc**
               With **-msubxc** , GCC generates code that takes advantage of the
               UltraSPARC Subtract-Extended-with-Carry instruction.  The
               default is **-msubxc** when targeting a CPU that supports such an
               instruction, such as Niagara-7 and later.
    
           **-mfix-at697f**
               Enable the documented workaround for the single erratum of the
               Atmel AT697F processor (which corresponds to erratum #13 of
               the AT697E processor).
    
           **-mfix-ut699**
               Enable the documented workarounds for the floating-point
               errata and the data cache nullify errata of the UT699
               processor.
    
           **-mfix-ut700**
               Enable the documented workaround for the back-to-back store
               errata of the UT699E/UT700 processor.
    
           **-mfix-gr712rc**
               Enable the documented workaround for the back-to-back store
               errata of the GR712RC processor.
    
           These **-m** options are supported in addition to the above on
           SPARC-V9 processors in 64-bit environments:
    
           **-m32**
           **-m64**
               Generate code for a 32-bit or 64-bit environment.  The 32-bit
               environment sets int, long and pointer to 32 bits.  The 64-bit
               environment sets int to 32 bits and long and pointer to 64
               bits.
    
           **-mcmodel=**_which_
               Set the code model to one of
    
               **medlow**
                   The Medium/Low code model: 64-bit addresses, programs must
                   be linked in the low 32 bits of memory.  Programs can be
                   statically or dynamically linked.
    
               **medmid**
                   The Medium/Middle code model: 64-bit addresses, programs
                   must be linked in the low 44 bits of memory, the text and
                   data segments must be less than 2GB in size and the data
                   segment must be located within 2GB of the text segment.
    
               **medany**
                   The Medium/Anywhere code model: 64-bit addresses, programs
                   may be linked anywhere in memory, the text and data
                   segments must be less than 2GB in size and the data
                   segment must be located within 2GB of the text segment.
    
               **embmedany**
                   The Medium/Anywhere code model for embedded systems:
                   64-bit addresses, the text and data segments must be less
                   than 2GB in size, both starting anywhere in memory
                   (determined at link time).  The global register %g4 points
                   to the base of the data segment.  Programs are statically
                   linked and PIC is not supported.
    
           **-mmemory-model=**_mem-model_
               Set the memory model in force on the processor to one of
    
               **default**
                   The default memory model for the processor and operating
                   system.
    
               **rmo** Relaxed Memory Order
    
               **pso** Partial Store Order
    
               **tso** Total Store Order
    
               **sc** Sequential Consistency
    
               These memory models are formally defined in Appendix D of the
               SPARC-V9 architecture manual, as set in the processor's
               "PSTATE.MM" field.
    
           **-mstack-bias**
           **-mno-stack-bias**
               With **-mstack-bias** , GCC assumes that the stack pointer, and
               frame pointer if present, are offset by -2047 which must be
               added back when making stack frame references.  This is the
               default in 64-bit mode.  Otherwise, assume no such offset is
               present.
    
           _SPU Options_
    
           These **-m** options are supported on the SPU:
    
           **-mwarn-reloc**
           **-merror-reloc**
               The loader for SPU does not handle dynamic relocations.  By
               default, GCC gives an error when it generates code that
               requires a dynamic relocation.  **-mno-error-reloc** disables the
               error, **-mwarn-reloc** generates a warning instead.
    
           **-msafe-dma**
           **-munsafe-dma**
               Instructions that initiate or test completion of DMA must not
               be reordered with respect to loads and stores of the memory
               that is being accessed.  With **-munsafe-dma** you must use the
               "volatile" keyword to protect memory accesses, but that can
               lead to inefficient code in places where the memory is known
               to not change.  Rather than mark the memory as volatile, you
               can use **-msafe-dma** to tell the compiler to treat the DMA
               instructions as potentially affecting all memory.
    
           **-mbranch-hints**
               By default, GCC generates a branch hint instruction to avoid
               pipeline stalls for always-taken or probably-taken branches.
               A hint is not generated closer than 8 instructions away from
               its branch.  There is little reason to disable them, except
               for debugging purposes, or to make an object a little bit
               smaller.
    
           **-msmall-mem**
           **-mlarge-mem**
               By default, GCC generates code assuming that addresses are
               never larger than 18 bits.  With **-mlarge-mem** code is generated
               that assumes a full 32-bit address.
    
           **-mstdmain**
               By default, GCC links against startup code that assumes the
               SPU-style main function interface (which has an unconventional
               parameter list).  With **-mstdmain** , GCC links your program
               against startup code that assumes a C99-style interface to
               "main", including a local copy of "argv" strings.
    
           **-mfixed-range=**_register-range_
               Generate code treating the given register range as fixed
               registers.  A fixed register is one that the register
               allocator cannot use.  This is useful when compiling kernel
               code.  A register range is specified as two registers
               separated by a dash.  Multiple register ranges can be
               specified separated by a comma.
    
           **-mea32**
           **-mea64**
               Compile code assuming that pointers to the PPU address space
               accessed via the "__ea" named address space qualifier are
               either 32 or 64 bits wide.  The default is 32 bits.  As this
               is an ABI-changing option, all object code in an executable
               must be compiled with the same setting.
    
           **-maddress-space-conversion**
           **-mno-address-space-conversion**
               Allow/disallow treating the "__ea" address space as superset
               of the generic address space.  This enables explicit type
               casts between "__ea" and generic pointer as well as implicit
               conversions of generic pointers to "__ea" pointers.  The
               default is to allow address space pointer conversions.
    
           **-mcache-size=**_cache-size_
               This option controls the version of libgcc that the compiler
               links to an executable and selects a software-managed cache
               for accessing variables in the "__ea" address space with a
               particular cache size.  Possible options for _cache-size_ are **8** ,
               **16** , **32** , **64** and **128**.  The default cache size is 64KB.
    
           **-matomic-updates**
           **-mno-atomic-updates**
               This option controls the version of libgcc that the compiler
               links to an executable and selects whether atomic updates to
               the software-managed cache of PPU-side variables are used.  If
               you use atomic updates, changes to a PPU variable from SPU
               code using the "__ea" named address space qualifier do not
               interfere with changes to other PPU variables residing in the
               same cache line from PPU code.  If you do not use atomic
               updates, such interference may occur; however, writing back
               cache lines is more efficient.  The default behavior is to use
               atomic updates.
    
           **-mdual-nops**
           **-mdual-nops=**_n_
               By default, GCC inserts NOPs to increase dual issue when it
               expects it to increase performance.  _n_ can be a value from 0
               to 10.  A smaller _n_ inserts fewer NOPs.  10 is the default, 0
               is the same as **-mno-dual-nops**.  Disabled with **-Os**.
    
           **-mhint-max-nops=**_n_
               Maximum number of NOPs to insert for a branch hint.  A branch
               hint must be at least 8 instructions away from the branch it
               is affecting.  GCC inserts up to _n_ NOPs to enforce this,
               otherwise it does not generate the branch hint.
    
           **-mhint-max-distance=**_n_
               The encoding of the branch hint instruction limits the hint to
               be within 256 instructions of the branch it is affecting.  By
               default, GCC makes sure it is within 125.
    
           **-msafe-hints**
               Work around a hardware bug that causes the SPU to stall
               indefinitely.  By default, GCC inserts the "hbrp" instruction
               to make sure this stall won't happen.
    
           _Options for System V_
    
           These additional options are available on System V Release 4 for
           compatibility with other compilers on those systems:
    
           **-G** Create a shared object.  It is recommended that **-symbolic** or
               **-shared** be used instead.
    
           **-Qy** Identify the versions of each tool used by the compiler, in a
               ".ident" assembler directive in the output.
    
           **-Qn** Refrain from adding ".ident" directives to the output file
               (this is the default).
    
           **-YP,**_dirs_
               Search the directories _dirs_ , and no others, for libraries
               specified with **-l**.
    
           **-Ym,**_dir_
               Look in the directory _dir_ to find the M4 preprocessor.  The
               assembler uses this option.
    
           _TILE-Gx Options_
    
           These **-m** options are supported on the TILE-Gx:
    
           **-mcmodel=small**
               Generate code for the small model.  The distance for direct
               calls is limited to 500M in either direction.  PC-relative
               addresses are 32 bits.  Absolute addresses support the full
               address range.
    
           **-mcmodel=large**
               Generate code for the large model.  There is no limitation on
               call distance, pc-relative addresses, or absolute addresses.
    
           **-mcpu=**_name_
               Selects the type of CPU to be targeted.  Currently the only
               supported type is **tilegx**.
    
           **-m32**
           **-m64**
               Generate code for a 32-bit or 64-bit environment.  The 32-bit
               environment sets int, long, and pointer to 32 bits.  The
               64-bit environment sets int to 32 bits and long and pointer to
               64 bits.
    
           **-mbig-endian**
           **-mlittle-endian**
               Generate code in big/little endian mode, respectively.
    
           _TILEPro Options_
    
           These **-m** options are supported on the TILEPro:
    
           **-mcpu=**_name_
               Selects the type of CPU to be targeted.  Currently the only
               supported type is **tilepro**.
    
           **-m32**
               Generate code for a 32-bit environment, which sets int, long,
               and pointer to 32 bits.  This is the only supported behavior
               so the flag is essentially ignored.
    
           _V850 Options_
    
           These **-m** options are defined for V850 implementations:
    
           **-mlong-calls**
           **-mno-long-calls**
               Treat all calls as being far away (near).  If calls are
               assumed to be far away, the compiler always loads the
               function's address into a register, and calls indirect through
               the pointer.
    
           **-mno-ep**
           **-mep**
               Do not optimize (do optimize) basic blocks that use the same
               index pointer 4 or more times to copy pointer into the "ep"
               register, and use the shorter "sld" and "sst" instructions.
               The **-mep** option is on by default if you optimize.
    
           **-mno-prolog-function**
           **-mprolog-function**
               Do not use (do use) external functions to save and restore
               registers at the prologue and epilogue of a function.  The
               external functions are slower, but use less code space if more
               than one function saves the same number of registers.  The
               **-mprolog-function** option is on by default if you optimize.
    
           **-mspace**
               Try to make the code as small as possible.  At present, this
               just turns on the **-mep** and **-mprolog-function** options.
    
           **-mtda=**_n_
               Put static or global variables whose size is _n_ bytes or less
               into the tiny data area that register "ep" points to.  The
               tiny data area can hold up to 256 bytes in total (128 bytes
               for byte references).
    
           **-msda=**_n_
               Put static or global variables whose size is _n_ bytes or less
               into the small data area that register "gp" points to.  The
               small data area can hold up to 64 kilobytes.
    
           **-mzda=**_n_
               Put static or global variables whose size is _n_ bytes or less
               into the first 32 kilobytes of memory.
    
           **-mv850**
               Specify that the target processor is the V850.
    
           **-mv850e3v5**
               Specify that the target processor is the V850E3V5.  The
               preprocessor constant "__v850e3v5__" is defined if this option
               is used.
    
           **-mv850e2v4**
               Specify that the target processor is the V850E3V5.  This is an
               alias for the **-mv850e3v5** option.
    
           **-mv850e2v3**
               Specify that the target processor is the V850E2V3.  The
               preprocessor constant "__v850e2v3__" is defined if this option
               is used.
    
           **-mv850e2**
               Specify that the target processor is the V850E2.  The
               preprocessor constant "__v850e2__" is defined if this option
               is used.
    
           **-mv850e1**
               Specify that the target processor is the V850E1.  The
               preprocessor constants "__v850e1__" and "__v850e__" are
               defined if this option is used.
    
           **-mv850es**
               Specify that the target processor is the V850ES.  This is an
               alias for the **-mv850e1** option.
    
           **-mv850e**
               Specify that the target processor is the V850E.  The
               preprocessor constant "__v850e__" is defined if this option is
               used.
    
               If neither **-mv850** nor **-mv850e** nor **-mv850e1** nor **-mv850e2** nor
               **-mv850e2v3** nor **-mv850e3v5** are defined then a default target
               processor is chosen and the relevant **__v850*__** preprocessor
               constant is defined.
    
               The preprocessor constants "__v850" and "__v851__" are always
               defined, regardless of which processor variant is the target.
    
           **-mdisable-callt**
           **-mno-disable-callt**
               This option suppresses generation of the "CALLT" instruction
               for the v850e, v850e1, v850e2, v850e2v3 and v850e3v5 flavors
               of the v850 architecture.
    
               This option is enabled by default when the RH850 ABI is in use
               (see **-mrh850-abi**), and disabled by default when the GCC ABI is
               in use.  If "CALLT" instructions are being generated then the
               C preprocessor symbol "__V850_CALLT__" is defined.
    
           **-mrelax**
           **-mno-relax**
               Pass on (or do not pass on) the **-mrelax** command-line option to
               the assembler.
    
           **-mlong-jumps**
           **-mno-long-jumps**
               Disable (or re-enable) the generation of PC-relative jump
               instructions.
    
           **-msoft-float**
           **-mhard-float**
               Disable (or re-enable) the generation of hardware floating
               point instructions.  This option is only significant when the
               target architecture is **V850E2V3** or higher.  If hardware
               floating point instructions are being generated then the C
               preprocessor symbol "__FPU_OK__" is defined, otherwise the
               symbol "__NO_FPU__" is defined.
    
           **-mloop**
               Enables the use of the e3v5 LOOP instruction.  The use of this
               instruction is not enabled by default when the e3v5
               architecture is selected because its use is still
               experimental.
    
           **-mrh850-abi**
           **-mghs**
               Enables support for the RH850 version of the V850 ABI.  This
               is the default.  With this version of the ABI the following
               rules apply:
    
               *   Integer sized structures and unions are returned via a
                   memory pointer rather than a register.
    
               *   Large structures and unions (more than 8 bytes in size)
                   are passed by value.
    
               *   Functions are aligned to 16-bit boundaries.
    
               *   The **-m8byte-align** command-line option is supported.
    
               *   The **-mdisable-callt** command-line option is enabled by
                   default.  The **-mno-disable-callt** command-line option is
                   not supported.
    
               When this version of the ABI is enabled the C preprocessor
               symbol "__V850_RH850_ABI__" is defined.
    
           **-mgcc-abi**
               Enables support for the old GCC version of the V850 ABI.  With
               this version of the ABI the following rules apply:
    
               *   Integer sized structures and unions are returned in
                   register "r10".
    
               *   Large structures and unions (more than 8 bytes in size)
                   are passed by reference.
    
               *   Functions are aligned to 32-bit boundaries, unless
                   optimizing for size.
    
               *   The **-m8byte-align** command-line option is not supported.
    
               *   The **-mdisable-callt** command-line option is supported but
                   not enabled by default.
    
               When this version of the ABI is enabled the C preprocessor
               symbol "__V850_GCC_ABI__" is defined.
    
           **-m8byte-align**
           **-mno-8byte-align**
               Enables support for "double" and "long long" types to be
               aligned on 8-byte boundaries.  The default is to restrict the
               alignment of all objects to at most 4-bytes.  When
               **-m8byte-align** is in effect the C preprocessor symbol
               "__V850_8BYTE_ALIGN__" is defined.
    
           **-mbig-switch**
               Generate code suitable for big switch tables.  Use this option
               only if the assembler/linker complain about out of range
               branches within a switch table.
    
           **-mapp-regs**
               This option causes r2 and r5 to be used in the code generated
               by the compiler.  This setting is the default.
    
           **-mno-app-regs**
               This option causes r2 and r5 to be treated as fixed registers.
    
           _VAX Options_
    
           These **-m** options are defined for the VAX:
    
           **-munix**
               Do not output certain jump instructions ("aobleq" and so on)
               that the Unix assembler for the VAX cannot handle across long
               ranges.
    
           **-mgnu**
               Do output those jump instructions, on the assumption that the
               GNU assembler is being used.
    
           **-mg** Output code for G-format floating-point numbers instead of
               D-format.
    
           _Visium Options_
    
           **-mdebug**
               A program which performs file I/O and is destined to run on an
               MCM target should be linked with this option.  It causes the
               libraries libc.a and libdebug.a to be linked.  The program
               should be run on the target under the control of the GDB
               remote debugging stub.
    
           **-msim**
               A program which performs file I/O and is destined to run on
               the simulator should be linked with option.  This causes
               libraries libc.a and libsim.a to be linked.
    
           **-mfpu**
           **-mhard-float**
               Generate code containing floating-point instructions.  This is
               the default.
    
           **-mno-fpu**
           **-msoft-float**
               Generate code containing library calls for floating-point.
    
               **-msoft-float** changes the calling convention in the output
               file; therefore, it is only useful if you compile _all_ of a
               program with this option.  In particular, you need to compile
               _libgcc.a_ , the library that comes with GCC, with **-msoft-float**
               in order for this to work.
    
           **-mcpu=**_cpu_type_
               Set the instruction set, register set, and instruction
               scheduling parameters for machine type _cpu_type_.  Supported
               values for _cpu_type_ are **mcm** , **gr5** and **gr6**.
    
               **mcm** is a synonym of **gr5** present for backward compatibility.
    
               By default (unless configured otherwise), GCC generates code
               for the GR5 variant of the Visium architecture.
    
               With **-mcpu=gr6** , GCC generates code for the GR6 variant of the
               Visium architecture.  The only difference from GR5 code is
               that the compiler will generate block move instructions.
    
           **-mtune=**_cpu_type_
               Set the instruction scheduling parameters for machine type
               _cpu_type_ , but do not set the instruction set or register set
               that the option **-mcpu=**_cpu_type_ would.
    
           **-msv-mode**
               Generate code for the supervisor mode, where there are no
               restrictions on the access to general registers.  This is the
               default.
    
           **-muser-mode**
               Generate code for the user mode, where the access to some
               general registers is forbidden: on the GR5, registers r24 to
               r31 cannot be accessed in this mode; on the GR6, only
               registers r29 to r31 are affected.
    
           _VMS Options_
    
           These **-m** options are defined for the VMS implementations:
    
           **-mvms-return-codes**
               Return VMS condition codes from "main". The default is to
               return POSIX-style condition (e.g. error) codes.
    
           **-mdebug-main=**_prefix_
               Flag the first routine whose name starts with _prefix_ as the
               main routine for the debugger.
    
           **-mmalloc64**
               Default to 64-bit memory allocation routines.
    
           **-mpointer-size=**_size_
               Set the default size of pointers. Possible options for _size_
               are **32** or **short** for 32 bit pointers, **64** or **long** for 64 bit
               pointers, and **no** for supporting only 32 bit pointers.  The
               later option disables "pragma pointer_size".
    
           _VxWorks Options_
    
           The options in this section are defined for all VxWorks targets.
           Options specific to the target hardware are listed with the other
           options for that target.
    
           **-mrtp**
               GCC can generate code for both VxWorks kernels and real time
               processes (RTPs).  This option switches from the former to the
               latter.  It also defines the preprocessor macro "__RTP__".
    
           **-non-static**
               Link an RTP executable against shared libraries rather than
               static libraries.  The options **-static** and **-shared** can also be
               used for RTPs; **-static** is the default.
    
           **-Bstatic**
           **-Bdynamic**
               These options are passed down to the linker.  They are defined
               for compatibility with Diab.
    
           **-Xbind-lazy**
               Enable lazy binding of function calls.  This option is
               equivalent to **-Wl,-z,now** and is defined for compatibility with
               Diab.
    
           **-Xbind-now**
               Disable lazy binding of function calls.  This option is the
               default and is defined for compatibility with Diab.
    
           _x86 Options_
    
           These **-m** options are defined for the x86 family of computers.
    
           **-march=**_cpu-type_
               Generate instructions for the machine type _cpu-type_.  In
               contrast to **-mtune=**_cpu-type_ , which merely tunes the generated
               code for the specified _cpu-type_ , **-march=**_cpu-type_ allows GCC to
               generate code that may not run at all on processors other than
               the one indicated.  Specifying **-march=**_cpu-type_ implies
               **-mtune=**_cpu-type_.
    
               The choices for _cpu-type_ are:
    
               **native**
                   This selects the CPU to generate code for at compilation
                   time by determining the processor type of the compiling
                   machine.  Using **-march=native** enables all instruction
                   subsets supported by the local machine (hence the result
                   might not run on different machines).  Using **-mtune=native**
                   produces code optimized for the local machine under the
                   constraints of the selected instruction set.
    
               **x86-64**
                   A generic CPU with 64-bit extensions.
    
               **i386**
                   Original Intel i386 CPU.
    
               **i486**
                   Intel i486 CPU.  (No scheduling is implemented for this
                   chip.)
    
               **i586**
               **pentium**
                   Intel Pentium CPU with no MMX support.
    
               **lakemont**
                   Intel Lakemont MCU, based on Intel Pentium CPU.
    
               **pentium-mmx**
                   Intel Pentium MMX CPU, based on Pentium core with MMX
                   instruction set support.
    
               **pentiumpro**
                   Intel Pentium Pro CPU.
    
               **i686**
                   When used with **-march** , the Pentium Pro instruction set is
                   used, so the code runs on all i686 family chips.  When
                   used with **-mtune** , it has the same meaning as **generic**.
    
               **pentium2**
                   Intel Pentium II CPU, based on Pentium Pro core with MMX
                   instruction set support.
    
               **pentium3**
               **pentium3m**
                   Intel Pentium III CPU, based on Pentium Pro core with MMX
                   and SSE instruction set support.
    
               **pentium-m**
                   Intel Pentium M; low-power version of Intel Pentium III
                   CPU with MMX, SSE and SSE2 instruction set support.  Used
                   by Centrino notebooks.
    
               **pentium4**
               **pentium4m**
                   Intel Pentium 4 CPU with MMX, SSE and SSE2 instruction set
                   support.
    
               **prescott**
                   Improved version of Intel Pentium 4 CPU with MMX, SSE,
                   SSE2 and SSE3 instruction set support.
    
               **nocona**
                   Improved version of Intel Pentium 4 CPU with 64-bit
                   extensions, MMX, SSE, SSE2 and SSE3 instruction set
                   support.
    
               **core2**
                   Intel Core 2 CPU with 64-bit extensions, MMX, SSE, SSE2,
                   SSE3 and SSSE3 instruction set support.
    
               **nehalem**
                   Intel Nehalem CPU with 64-bit extensions, MMX, SSE, SSE2,
                   SSE3, SSSE3, SSE4.1, SSE4.2 and POPCNT instruction set
                   support.
    
               **westmere**
                   Intel Westmere CPU with 64-bit extensions, MMX, SSE, SSE2,
                   SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AES and PCLMUL
                   instruction set support.
    
               **sandybridge**
                   Intel Sandy Bridge CPU with 64-bit extensions, MMX, SSE,
                   SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AES and
                   PCLMUL instruction set support.
    
               **ivybridge**
                   Intel Ivy Bridge CPU with 64-bit extensions, MMX, SSE,
                   SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AES,
                   PCLMUL, FSGSBASE, RDRND and F16C instruction set support.
    
               **haswell**
                   Intel Haswell CPU with 64-bit extensions, MOVBE, MMX, SSE,
                   SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES,
                   PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2 and F16C
                   instruction set support.
    
               **broadwell**
                   Intel Broadwell CPU with 64-bit extensions, MOVBE, MMX,
                   SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AVX2,
                   AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2, F16C, RDSEED
                   ADCX and PREFETCHW instruction set support.
    
               **skylake**
                   Intel Skylake CPU with 64-bit extensions, MOVBE, MMX, SSE,
                   SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES,
                   PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2, F16C, RDSEED,
                   ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC and XSAVES instruction
                   set support.
    
               **bonnell**
                   Intel Bonnell CPU with 64-bit extensions, MOVBE, MMX, SSE,
                   SSE2, SSE3 and SSSE3 instruction set support.
    
               **silvermont**
                   Intel Silvermont CPU with 64-bit extensions, MOVBE, MMX,
                   SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AES,
                   PREFETCHW, PCLMUL and RDRND instruction set support.
    
               **goldmont**
                   Intel Goldmont CPU with 64-bit extensions, MOVBE, MMX,
                   SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AES,
                   PREFETCHW, PCLMUL, RDRND, XSAVE, XSAVEC, XSAVES, XSAVEOPT
                   and FSGSBASE instruction set support.
    
               **goldmont-plus**
                   Intel Goldmont Plus CPU with 64-bit extensions, MOVBE,
                   MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AES,
                   PREFETCHW, PCLMUL, RDRND, XSAVE, XSAVEC, XSAVES, XSAVEOPT,
                   FSGSBASE, PTWRITE, RDPID, SGX and UMIP instruction set
                   support.
    
               **tremont**
                   Intel Tremont CPU with 64-bit extensions, MOVBE, MMX, SSE,
                   SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AES, PREFETCHW,
                   PCLMUL, RDRND, XSAVE, XSAVEC, XSAVES, XSAVEOPT, FSGSBASE,
                   PTWRITE, RDPID, SGX, UMIP, GFNI-SSE, CLWB, MOVDIRI,
                   MOVDIR64B, CLDEMOTE and WAITPKG instruction set support.
    
               **knl** Intel Knight's Landing CPU with 64-bit extensions, MOVBE,
                   MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX,
                   AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2, F16C,
                   RDSEED, ADCX, PREFETCHW, PREFETCHWT1, AVX512F, AVX512PF,
                   AVX512ER and AVX512CD instruction set support.
    
               **knm** Intel Knights Mill CPU with 64-bit extensions, MOVBE, MMX,
                   SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AVX2,
                   AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2, F16C,
                   RDSEED, ADCX, PREFETCHW, PREFETCHWT1, AVX512F, AVX512PF,
                   AVX512ER, AVX512CD, AVX5124VNNIW, AVX5124FMAPS and
                   AVX512VPOPCNTDQ instruction set support.
    
               **skylake-avx512**
                   Intel Skylake Server CPU with 64-bit extensions, MOVBE,
                   MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, PKU,
                   AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
                   F16C, RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES,
                   AVX512F, CLWB, AVX512VL, AVX512BW, AVX512DQ and AVX512CD
                   instruction set support.
    
               **cannonlake**
                   Intel Cannonlake Server CPU with 64-bit extensions, MOVBE,
                   MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, PKU,
                   AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
                   F16C, RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES,
                   AVX512F, AVX512VL, AVX512BW, AVX512DQ, AVX512CD,
                   AVX512VBMI, AVX512IFMA, SHA and UMIP instruction set
                   support.
    
               **icelake-client**
                   Intel Icelake Client CPU with 64-bit extensions, MOVBE,
                   MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, PKU,
                   AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
                   F16C, RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES,
                   AVX512F, AVX512VL, AVX512BW, AVX512DQ, AVX512CD,
                   AVX512VBMI, AVX512IFMA, SHA, CLWB, UMIP, RDPID, GFNI,
                   AVX512VBMI2, AVX512VPOPCNTDQ, AVX512BITALG, AVX512VNNI,
                   VPCLMULQDQ, VAES instruction set support.
    
               **icelake-server**
                   Intel Icelake Server CPU with 64-bit extensions, MOVBE,
                   MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, PKU,
                   AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
                   F16C, RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES,
                   AVX512F, AVX512VL, AVX512BW, AVX512DQ, AVX512CD,
                   AVX512VBMI, AVX512IFMA, SHA, CLWB, UMIP, RDPID, GFNI,
                   AVX512VBMI2, AVX512VPOPCNTDQ, AVX512BITALG, AVX512VNNI,
                   VPCLMULQDQ, VAES, PCONFIG and WBNOINVD instruction set
                   support.
    
               **cascadelake**
                   Intel Cascadelake CPU with 64-bit extensions, MOVBE, MMX,
                   SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, PKU, AVX,
                   AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2, F16C,
                   RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES,
                   AVX512F, CLWB, AVX512VL, AVX512BW, AVX512DQ, AVX512CD and
                   AVX512VNNI instruction set support.
    
               **tigerlake**
                   Intel Tigerlake CPU with 64-bit extensions, MOVBE, MMX,
                   SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, PKU, AVX,
                   AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2, F16C,
                   RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES,
                   AVX512F, AVX512VL, AVX512BW, AVX512DQ, AVX512CD,
                   AVX512VBMI, AVX512IFMA, SHA, CLWB, UMIP, RDPID, GFNI,
                   AVX512VBMI2, AVX512VPOPCNTDQ, AVX512BITALG, AVX512VNNI,
                   VPCLMULQDQ, VAES, PCONFIG, WBNOINVD, MOVDIRI, MOVDIR64B
                   and CLWB instruction set support.
    
               **k6** AMD K6 CPU with MMX instruction set support.
    
               **k6-2**
               **k6-3**
                   Improved versions of AMD K6 CPU with MMX and 3DNow!
                   instruction set support.
    
               **athlon**
               **athlon-tbird**
                   AMD Athlon CPU with MMX, 3dNOW!, enhanced 3DNow! and SSE
                   prefetch instructions support.
    
               **athlon-4**
               **athlon-xp**
               **athlon-mp**
                   Improved AMD Athlon CPU with MMX, 3DNow!, enhanced 3DNow!
                   and full SSE instruction set support.
    
               **k8**
               **opteron**
               **athlon64**
               **athlon-fx**
                   Processors based on the AMD K8 core with x86-64
                   instruction set support, including the AMD Opteron, Athlon
                   64, and Athlon 64 FX processors.  (This supersets MMX,
                   SSE, SSE2, 3DNow!, enhanced 3DNow! and 64-bit instruction
                   set extensions.)
    
               **k8-sse3**
               **opteron-sse3**
               **athlon64-sse3**
                   Improved versions of AMD K8 cores with SSE3 instruction
                   set support.
    
               **amdfam10**
               **barcelona**
                   CPUs based on AMD Family 10h cores with x86-64 instruction
                   set support.  (This supersets MMX, SSE, SSE2, SSE3, SSE4A,
                   3DNow!, enhanced 3DNow!, ABM and 64-bit instruction set
                   extensions.)
    
               **bdver1**
                   CPUs based on AMD Family 15h cores with x86-64 instruction
                   set support.  (This supersets FMA4, AVX, XOP, LWP, AES,
                   PCL_MUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1,
                   SSE4.2, ABM and 64-bit instruction set extensions.)
    
               **bdver2**
                   AMD Family 15h core based CPUs with x86-64 instruction set
                   support.  (This supersets BMI, TBM, F16C, FMA, FMA4, AVX,
                   XOP, LWP, AES, PCL_MUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A,
                   SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set
                   extensions.)
    
               **bdver3**
                   AMD Family 15h core based CPUs with x86-64 instruction set
                   support.  (This supersets BMI, TBM, F16C, FMA, FMA4,
                   FSGSBASE, AVX, XOP, LWP, AES, PCL_MUL, CX16, MMX, SSE,
                   SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit
                   instruction set extensions.
    
               **bdver4**
                   AMD Family 15h core based CPUs with x86-64 instruction set
                   support.  (This supersets BMI, BMI2, TBM, F16C, FMA, FMA4,
                   FSGSBASE, AVX, AVX2, XOP, LWP, AES, PCL_MUL, CX16, MOVBE,
                   MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM
                   and 64-bit instruction set extensions.
    
               **znver1**
                   AMD Family 17h core based CPUs with x86-64 instruction set
                   support.  (This supersets BMI, BMI2, F16C, FMA, FSGSBASE,
                   AVX, AVX2, ADCX, RDSEED, MWAITX, SHA, CLZERO, AES,
                   PCL_MUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3,
                   SSE4.1, SSE4.2, ABM, XSAVEC, XSAVES, CLFLUSHOPT, POPCNT,
                   and 64-bit instruction set extensions.
    
               **znver2**
                   AMD Family 17h core based CPUs with x86-64 instruction set
                   support. (This supersets BMI, BMI2, ,CLWB, F16C, FMA,
                   FSGSBASE, AVX, AVX2, ADCX, RDSEED, MWAITX, SHA, CLZERO,
                   AES, PCL_MUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A,
                   SSSE3, SSE4.1, SSE4.2, ABM, XSAVEC, XSAVES, CLFLUSHOPT,
                   POPCNT, and 64-bit instruction set extensions.)
    
               **btver1**
                   CPUs based on AMD Family 14h cores with x86-64 instruction
                   set support.  (This supersets MMX, SSE, SSE2, SSE3, SSSE3,
                   SSE4A, CX16, ABM and 64-bit instruction set extensions.)
    
               **btver2**
                   CPUs based on AMD Family 16h cores with x86-64 instruction
                   set support. This includes MOVBE, F16C, BMI, AVX, PCL_MUL,
                   AES, SSE4.2, SSE4.1, CX16, ABM, SSE4A, SSSE3, SSE3, SSE2,
                   SSE, MMX and 64-bit instruction set extensions.
    
               **winchip-c6**
                   IDT WinChip C6 CPU, dealt in same way as i486 with
                   additional MMX instruction set support.
    
               **winchip2**
                   IDT WinChip 2 CPU, dealt in same way as i486 with
                   additional MMX and 3DNow!  instruction set support.
    
               **c3** VIA C3 CPU with MMX and 3DNow! instruction set support.
                   (No scheduling is implemented for this chip.)
    
               **c3-2**
                   VIA C3-2 (Nehemiah/C5XL) CPU with MMX and SSE instruction
                   set support.  (No scheduling is implemented for this
                   chip.)
    
               **c7** VIA C7 (Esther) CPU with MMX, SSE, SSE2 and SSE3
                   instruction set support.  (No scheduling is implemented
                   for this chip.)
    
               **samuel-2**
                   VIA Eden Samuel 2 CPU with MMX and 3DNow! instruction set
                   support.  (No scheduling is implemented for this chip.)
    
               **nehemiah**
                   VIA Eden Nehemiah CPU with MMX and SSE instruction set
                   support.  (No scheduling is implemented for this chip.)
    
               **esther**
                   VIA Eden Esther CPU with MMX, SSE, SSE2 and SSE3
                   instruction set support.  (No scheduling is implemented
                   for this chip.)
    
               **eden-x2**
                   VIA Eden X2 CPU with x86-64, MMX, SSE, SSE2 and SSE3
                   instruction set support.  (No scheduling is implemented
                   for this chip.)
    
               **eden-x4**
                   VIA Eden X4 CPU with x86-64, MMX, SSE, SSE2, SSE3, SSSE3,
                   SSE4.1, SSE4.2, AVX and AVX2 instruction set support.  (No
                   scheduling is implemented for this chip.)
    
               **nano**
                   Generic VIA Nano CPU with x86-64, MMX, SSE, SSE2, SSE3 and
                   SSSE3 instruction set support.  (No scheduling is
                   implemented for this chip.)
    
               **nano-1000**
                   VIA Nano 1xxx CPU with x86-64, MMX, SSE, SSE2, SSE3 and
                   SSSE3 instruction set support.  (No scheduling is
                   implemented for this chip.)
    
               **nano-2000**
                   VIA Nano 2xxx CPU with x86-64, MMX, SSE, SSE2, SSE3 and
                   SSSE3 instruction set support.  (No scheduling is
                   implemented for this chip.)
    
               **nano-3000**
                   VIA Nano 3xxx CPU with x86-64, MMX, SSE, SSE2, SSE3, SSSE3
                   and SSE4.1 instruction set support.  (No scheduling is
                   implemented for this chip.)
    
               **nano-x2**
                   VIA Nano Dual Core CPU with x86-64, MMX, SSE, SSE2, SSE3,
                   SSSE3 and SSE4.1 instruction set support.  (No scheduling
                   is implemented for this chip.)
    
               **nano-x4**
                   VIA Nano Quad Core CPU with x86-64, MMX, SSE, SSE2, SSE3,
                   SSSE3 and SSE4.1 instruction set support.  (No scheduling
                   is implemented for this chip.)
    
               **geode**
                   AMD Geode embedded processor with MMX and 3DNow!
                   instruction set support.
    
           **-mtune=**_cpu-type_
               Tune to _cpu-type_ everything applicable about the generated
               code, except for the ABI and the set of available
               instructions.  While picking a specific _cpu-type_ schedules
               things appropriately for that particular chip, the compiler
               does not generate any code that cannot run on the default
               machine type unless you use a **-march=**_cpu-type_ option.  For
               example, if GCC is configured for i686-pc-linux-gnu then
               **-mtune=pentium4** generates code that is tuned for Pentium 4 but
               still runs on i686 machines.
    
               The choices for _cpu-type_ are the same as for **-march**.  In
               addition, **-mtune** supports 2 extra choices for _cpu-type_ :
    
               **generic**
                   Produce code optimized for the most common
                   IA32/AMD64/EM64T processors.  If you know the CPU on which
                   your code will run, then you should use the corresponding
                   **-mtune** or **-march** option instead of **-mtune=generic**.  But,
                   if you do not know exactly what CPU users of your
                   application will have, then you should use this option.
    
                   As new processors are deployed in the marketplace, the
                   behavior of this option will change.  Therefore, if you
                   upgrade to a newer version of GCC, code generation
                   controlled by this option will change to reflect the
                   processors that are most common at the time that version
                   of GCC is released.
    
                   There is no **-march=generic** option because **-march** indicates
                   the instruction set the compiler can use, and there is no
                   generic instruction set applicable to all processors.  In
                   contrast, **-mtune** indicates the processor (or, in this
                   case, collection of processors) for which the code is
                   optimized.
    
               **intel**
                   Produce code optimized for the most current Intel
                   processors, which are Haswell and Silvermont for this
                   version of GCC.  If you know the CPU on which your code
                   will run, then you should use the corresponding **-mtune** or
                   **-march** option instead of **-mtune=intel**.  But, if you want
                   your application performs better on both Haswell and
                   Silvermont, then you should use this option.
    
                   As new Intel processors are deployed in the marketplace,
                   the behavior of this option will change.  Therefore, if
                   you upgrade to a newer version of GCC, code generation
                   controlled by this option will change to reflect the most
                   current Intel processors at the time that version of GCC
                   is released.
    
                   There is no **-march=intel** option because **-march** indicates
                   the instruction set the compiler can use, and there is no
                   common instruction set applicable to all processors.  In
                   contrast, **-mtune** indicates the processor (or, in this
                   case, collection of processors) for which the code is
                   optimized.
    
           **-mcpu=**_cpu-type_
               A deprecated synonym for **-mtune**.
    
           **-mfpmath=**_unit_
               Generate floating-point arithmetic for selected unit _unit_.
               The choices for _unit_ are:
    
               **387** Use the standard 387 floating-point coprocessor present on
                   the majority of chips and emulated otherwise.  Code
                   compiled with this option runs almost everywhere.  The
                   temporary results are computed in 80-bit precision instead
                   of the precision specified by the type, resulting in
                   slightly different results compared to most of other
                   chips.  See **-ffloat-store** for more detailed description.
    
                   This is the default choice for non-Darwin x86-32 targets.
    
               **sse** Use scalar floating-point instructions present in the SSE
                   instruction set.  This instruction set is supported by
                   Pentium III and newer chips, and in the AMD line by
                   Athlon-4, Athlon XP and Athlon MP chips.  The earlier
                   version of the SSE instruction set supports only single-
                   precision arithmetic, thus the double and extended-
                   precision arithmetic are still done using 387.  A later
                   version, present only in Pentium 4 and AMD x86-64 chips,
                   supports double-precision arithmetic too.
    
                   For the x86-32 compiler, you must use **-march=**_cpu-type_ ,
                   **-msse** or **-msse2** switches to enable SSE extensions and make
                   this option effective.  For the x86-64 compiler, these
                   extensions are enabled by default.
    
                   The resulting code should be considerably faster in the
                   majority of cases and avoid the numerical instability
                   problems of 387 code, but may break some existing code
                   that expects temporaries to be 80 bits.
    
                   This is the default choice for the x86-64 compiler, Darwin
                   x86-32 targets, and the default choice for x86-32 targets
                   with the SSE2 instruction set when **-ffast-math** is enabled.
    
               **sse,387**
               **sse+387**
               **both**
                   Attempt to utilize both instruction sets at once.  This
                   effectively doubles the amount of available registers, and
                   on chips with separate execution units for 387 and SSE the
                   execution resources too.  Use this option with care, as it
                   is still experimental, because the GCC register allocator
                   does not model separate functional units well, resulting
                   in unstable performance.
    
           **-masm=**_dialect_
               Output assembly instructions using selected _dialect_.  Also
               affects which dialect is used for basic "asm" and extended
               "asm". Supported choices (in dialect order) are **att** or **intel**.
               The default is **att**. Darwin does not support **intel**.
    
           **-mieee-fp**
           **-mno-ieee-fp**
               Control whether or not the compiler uses IEEE floating-point
               comparisons.  These correctly handle the case where the result
               of a comparison is unordered.
    
           **-m80387**
           **-mhard-float**
               Generate output containing 80387 instructions for floating
               point.
    
           **-mno-80387**
           **-msoft-float**
               Generate output containing library calls for floating point.
    
               **Warning:** the requisite libraries are not part of GCC.
               Normally the facilities of the machine's usual C compiler are
               used, but this cannot be done directly in cross-compilation.
               You must make your own arrangements to provide suitable
               library functions for cross-compilation.
    
               On machines where a function returns floating-point results in
               the 80387 register stack, some floating-point opcodes may be
               emitted even if **-msoft-float** is used.
    
           **-mno-fp-ret-in-387**
               Do not use the FPU registers for return values of functions.
    
               The usual calling convention has functions return values of
               types "float" and "double" in an FPU register, even if there
               is no FPU.  The idea is that the operating system should
               emulate an FPU.
    
               The option **-mno-fp-ret-in-387** causes such values to be
               returned in ordinary CPU registers instead.
    
           **-mno-fancy-math-387**
               Some 387 emulators do not support the "sin", "cos" and "sqrt"
               instructions for the 387.  Specify this option to avoid
               generating those instructions.  This option is overridden when
               **-march** indicates that the target CPU always has an FPU and so
               the instruction does not need emulation.  These instructions
               are not generated unless you also use the
               **-funsafe-math-optimizations** switch.
    
           **-malign-double**
           **-mno-align-double**
               Control whether GCC aligns "double", "long double", and "long
               long" variables on a two-word boundary or a one-word boundary.
               Aligning "double" variables on a two-word boundary produces
               code that runs somewhat faster on a Pentium at the expense of
               more memory.
    
               On x86-64, **-malign-double** is enabled by default.
    
               **Warning:** if you use the **-malign-double** switch, structures
               containing the above types are aligned differently than the
               published application binary interface specifications for the
               x86-32 and are not binary compatible with structures in code
               compiled without that switch.
    
           **-m96bit-long-double**
           **-m128bit-long-double**
               These switches control the size of "long double" type.  The
               x86-32 application binary interface specifies the size to be
               96 bits, so **-m96bit-long-double** is the default in 32-bit mode.
    
               Modern architectures (Pentium and newer) prefer "long double"
               to be aligned to an 8- or 16-byte boundary.  In arrays or
               structures conforming to the ABI, this is not possible.  So
               specifying **-m128bit-long-double** aligns "long double" to a
               16-byte boundary by padding the "long double" with an
               additional 32-bit zero.
    
               In the x86-64 compiler, **-m128bit-long-double** is the default
               choice as its ABI specifies that "long double" is aligned on
               16-byte boundary.
    
               Notice that neither of these options enable any extra
               precision over the x87 standard of 80 bits for a "long
               double".
    
               **Warning:** if you override the default value for your target
               ABI, this changes the size of structures and arrays containing
               "long double" variables, as well as modifying the function
               calling convention for functions taking "long double".  Hence
               they are not binary-compatible with code compiled without that
               switch.
    
           **-mlong-double-64**
           **-mlong-double-80**
           **-mlong-double-128**
               These switches control the size of "long double" type. A size
               of 64 bits makes the "long double" type equivalent to the
               "double" type. This is the default for 32-bit Bionic C
               library.  A size of 128 bits makes the "long double" type
               equivalent to the "__float128" type. This is the default for
               64-bit Bionic C library.
    
               **Warning:** if you override the default value for your target
               ABI, this changes the size of structures and arrays containing
               "long double" variables, as well as modifying the function
               calling convention for functions taking "long double".  Hence
               they are not binary-compatible with code compiled without that
               switch.
    
           **-malign-data=**_type_
               Control how GCC aligns variables.  Supported values for _type_
               are **compat** uses increased alignment value compatible uses GCC
               4.8 and earlier, **abi** uses alignment value as specified by the
               psABI, and **cacheline** uses increased alignment value to match
               the cache line size.  **compat** is the default.
    
           **-mlarge-data-threshold=**_threshold_
               When **-mcmodel=medium** is specified, data objects larger than
               _threshold_ are placed in the large data section.  This value
               must be the same across all objects linked into the binary,
               and defaults to 65535.
    
           **-mrtd**
               Use a different function-calling convention, in which
               functions that take a fixed number of arguments return with
               the "ret _num"_ instruction, which pops their arguments while
               returning.  This saves one instruction in the caller since
               there is no need to pop the arguments there.
    
               You can specify that an individual function is called with
               this calling sequence with the function attribute "stdcall".
               You can also override the **-mrtd** option by using the function
               attribute "cdecl".
    
               **Warning:** this calling convention is incompatible with the one
               normally used on Unix, so you cannot use it if you need to
               call libraries compiled with the Unix compiler.
    
               Also, you must provide function prototypes for all functions
               that take variable numbers of arguments (including "printf");
               otherwise incorrect code is generated for calls to those
               functions.
    
               In addition, seriously incorrect code results if you call a
               function with too many arguments.  (Normally, extra arguments
               are harmlessly ignored.)
    
           **-mregparm=**_num_
               Control how many registers are used to pass integer arguments.
               By default, no registers are used to pass arguments, and at
               most 3 registers can be used.  You can control this behavior
               for a specific function by using the function attribute
               "regparm".
    
               **Warning:** if you use this switch, and _num_ is nonzero, then you
               must build all modules with the same value, including any
               libraries.  This includes the system libraries and startup
               modules.
    
           **-msseregparm**
               Use SSE register passing conventions for float and double
               arguments and return values.  You can control this behavior
               for a specific function by using the function attribute
               "sseregparm".
    
               **Warning:** if you use this switch then you must build all
               modules with the same value, including any libraries.  This
               includes the system libraries and startup modules.
    
           **-mvect8-ret-in-mem**
               Return 8-byte vectors in memory instead of MMX registers.
               This is the default on Solaris 8 and 9 and VxWorks to match
               the ABI of the Sun Studio compilers until version 12.  Later
               compiler versions (starting with Studio 12 Update 1) follow
               the ABI used by other x86 targets, which is the default on
               Solaris 10 and later.  _Only_ use this option if you need to
               remain compatible with existing code produced by those
               previous compiler versions or older versions of GCC.
    
           **-mpc32**
           **-mpc64**
           **-mpc80**
               Set 80387 floating-point precision to 32, 64 or 80 bits.  When
               **-mpc32** is specified, the significands of results of floating-
               point operations are rounded to 24 bits (single precision);
               **-mpc64** rounds the significands of results of floating-point
               operations to 53 bits (double precision) and **-mpc80** rounds the
               significands of results of floating-point operations to 64
               bits (extended double precision), which is the default.  When
               this option is used, floating-point operations in higher
               precisions are not available to the programmer without setting
               the FPU control word explicitly.
    
               Setting the rounding of floating-point operations to less than
               the default 80 bits can speed some programs by 2% or more.
               Note that some mathematical libraries assume that extended-
               precision (80-bit) floating-point operations are enabled by
               default; routines in such libraries could suffer significant
               loss of accuracy, typically through so-called "catastrophic
               cancellation", when this option is used to set the precision
               to less than extended precision.
    
           **-mstackrealign**
               Realign the stack at entry.  On the x86, the **-mstackrealign**
               option generates an alternate prologue and epilogue that
               realigns the run-time stack if necessary.  This supports
               mixing legacy codes that keep 4-byte stack alignment with
               modern codes that keep 16-byte stack alignment for SSE
               compatibility.  See also the attribute
               "force_align_arg_pointer", applicable to individual functions.
    
           **-mpreferred-stack-boundary=**_num_
               Attempt to keep the stack boundary aligned to a 2 raised to
               _num_ byte boundary.  If **-mpreferred-stack-boundary** is not
               specified, the default is 4 (16 bytes or 128 bits).
    
               **Warning:** When generating code for the x86-64 architecture with
               SSE extensions disabled, **-mpreferred-stack-boundary=3** can be
               used to keep the stack boundary aligned to 8 byte boundary.
               Since x86-64 ABI require 16 byte stack alignment, this is ABI
               incompatible and intended to be used in controlled environment
               where stack space is important limitation.  This option leads
               to wrong code when functions compiled with 16 byte stack
               alignment (such as functions from a standard library) are
               called with misaligned stack.  In this case, SSE instructions
               may lead to misaligned memory access traps.  In addition,
               variable arguments are handled incorrectly for 16 byte aligned
               objects (including x87 long double and __int128), leading to
               wrong results.  You must build all modules with
               **-mpreferred-stack-boundary=3** , including any libraries.  This
               includes the system libraries and startup modules.
    
           **-mincoming-stack-boundary=**_num_
               Assume the incoming stack is aligned to a 2 raised to _num_ byte
               boundary.  If **-mincoming-stack-boundary** is not specified, the
               one specified by **-mpreferred-stack-boundary** is used.
    
               On Pentium and Pentium Pro, "double" and "long double" values
               should be aligned to an 8-byte boundary (see **-malign-double**)
               or suffer significant run time performance penalties.  On
               Pentium III, the Streaming SIMD Extension (SSE) data type
               "__m128" may not work properly if it is not 16-byte aligned.
    
               To ensure proper alignment of this values on the stack, the
               stack boundary must be as aligned as that required by any
               value stored on the stack.  Further, every function must be
               generated such that it keeps the stack aligned.  Thus calling
               a function compiled with a higher preferred stack boundary
               from a function compiled with a lower preferred stack boundary
               most likely misaligns the stack.  It is recommended that
               libraries that use callbacks always use the default setting.
    
               This extra alignment does consume extra stack space, and
               generally increases code size.  Code that is sensitive to
               stack space usage, such as embedded systems and operating
               system kernels, may want to reduce the preferred alignment to
               **-mpreferred-stack-boundary=2**.
    
           **-mmmx**
           **-msse**
           **-msse2**
           **-msse3**
           **-mssse3**
           **-msse4**
           **-msse4a**
           **-msse4.1**
           **-msse4.2**
           **-mavx**
           **-mavx2**
           **-mavx512f**
           **-mavx512pf**
           **-mavx512er**
           **-mavx512cd**
           **-mavx512vl**
           **-mavx512bw**
           **-mavx512dq**
           **-mavx512ifma**
           **-mavx512vbmi**
           **-msha**
           **-maes**
           **-mpclmul**
           **-mclflushopt**
           **-mclwb**
           **-mfsgsbase**
           **-mptwrite**
           **-mrdrnd**
           **-mf16c**
           **-mfma**
           **-mpconfig**
           **-mwbnoinvd**
           **-mfma4**
           **-mprfchw**
           **-mrdpid**
           **-mprefetchwt1**
           **-mrdseed**
           **-msgx**
           **-mxop**
           **-mlwp**
           **-m3dnow**
           **-m3dnowa**
           **-mpopcnt**
           **-mabm**
           **-madx**
           **-mbmi**
           **-mbmi2**
           **-mlzcnt**
           **-mfxsr**
           **-mxsave**
           **-mxsaveopt**
           **-mxsavec**
           **-mxsaves**
           **-mrtm**
           **-mhle**
           **-mtbm**
           **-mmwaitx**
           **-mclzero**
           **-mpku**
           **-mavx512vbmi2**
           **-mgfni**
           **-mvaes**
           **-mwaitpkg**
           **-mvpclmulqdq**
           **-mavx512bitalg**
           **-mmovdiri**
           **-mmovdir64b**
           **-mavx512vpopcntdq**
           **-mavx5124fmaps**
           **-mavx512vnni**
           **-mavx5124vnniw**
           **-mcldemote**
               These switches enable the use of instructions in the MMX, SSE,
               SSE2, SSE3, SSSE3, SSE4, SSE4A, SSE4.1, SSE4.2, AVX, AVX2,
               AVX512F, AVX512PF, AVX512ER, AVX512CD, AVX512VL, AVX512BW,
               AVX512DQ, AVX512IFMA, AVX512VBMI, SHA, AES, PCLMUL,
               CLFLUSHOPT, CLWB, FSGSBASE, PTWRITE, RDRND, F16C, FMA,
               PCONFIG, WBNOINVD, FMA4, PREFETCHW, RDPID, PREFETCHWT1,
               RDSEED, SGX, XOP, LWP, 3DNow!, enhanced 3DNow!, POPCNT, ABM,
               ADX, BMI, BMI2, LZCNT, FXSR, XSAVE, XSAVEOPT, XSAVEC, XSAVES,
               RTM, HLE, TBM, MWAITX, CLZERO, PKU, AVX512VBMI2, GFNI, VAES,
               WAITPKG, VPCLMULQDQ, AVX512BITALG, MOVDIRI, MOVDIR64B,
               AVX512VPOPCNTDQ, AVX5124FMAPS, AVX512VNNI, AVX5124VNNIW, or
               CLDEMOTE extended instruction sets.  Each has a corresponding
               **-mno-** option to disable use of these instructions.
    
               These extensions are also available as built-in functions: see
               **x86 Built-in Functions** , for details of the functions enabled
               and disabled by these switches.
    
               To generate SSE/SSE2 instructions automatically from floating-
               point code (as opposed to 387 instructions), see **-mfpmath=sse**.
    
               GCC depresses SSEx instructions when **-mavx** is used. Instead,
               it generates new AVX instructions or AVX equivalence for all
               SSEx instructions when needed.
    
               These options enable GCC to use these extended instructions in
               generated code, even without **-mfpmath=sse**.  Applications that
               perform run-time CPU detection must compile separate files for
               each supported architecture, using the appropriate flags.  In
               particular, the file containing the CPU detection code should
               be compiled without these options.
    
           **-mdump-tune-features**
               This option instructs GCC to dump the names of the x86
               performance tuning features and default settings. The names
               can be used in **-mtune-ctrl=**_feature-list_.
    
           **-mtune-ctrl=**_feature-list_
               This option is used to do fine grain control of x86 code
               generation features.  _feature-list_ is a comma separated list
               of _feature_ names. See also **-mdump-tune-features**. When
               specified, the _feature_ is turned on if it is not preceded with
               **^** , otherwise, it is turned off.  **-mtune-ctrl=**_feature-list_ is
               intended to be used by GCC developers. Using it may lead to
               code paths not covered by testing and can potentially result
               in compiler ICEs or runtime errors.
    
           **-mno-default**
               This option instructs GCC to turn off all tunable features.
               See also **-mtune-ctrl=**_feature-list_ and **-mdump-tune-features**.
    
           **-mcld**
               This option instructs GCC to emit a "cld" instruction in the
               prologue of functions that use string instructions.  String
               instructions depend on the DF flag to select between
               autoincrement or autodecrement mode.  While the ABI specifies
               the DF flag to be cleared on function entry, some operating
               systems violate this specification by not clearing the DF flag
               in their exception dispatchers.  The exception handler can be
               invoked with the DF flag set, which leads to wrong direction
               mode when string instructions are used.  This option can be
               enabled by default on 32-bit x86 targets by configuring GCC
               with the **--enable-cld** configure option.  Generation of "cld"
               instructions can be suppressed with the **-mno-cld** compiler
               option in this case.
    
           **-mvzeroupper**
               This option instructs GCC to emit a "vzeroupper" instruction
               before a transfer of control flow out of the function to
               minimize the AVX to SSE transition penalty as well as remove
               unnecessary "zeroupper" intrinsics.
    
           **-mprefer-avx128**
               This option instructs GCC to use 128-bit AVX instructions
               instead of 256-bit AVX instructions in the auto-vectorizer.
    
           **-mprefer-vector-width=**_opt_
               This option instructs GCC to use _opt_ -bit vector width in
               instructions instead of default on the selected platform.
    
               **none**
                   No extra limitations applied to GCC other than defined by
                   the selected platform.
    
               **128** Prefer 128-bit vector width for instructions.
    
               **256** Prefer 256-bit vector width for instructions.
    
               **512** Prefer 512-bit vector width for instructions.
    
           **-mcx16**
               This option enables GCC to generate "CMPXCHG16B" instructions
               in 64-bit code to implement compare-and-exchange operations on
               16-byte aligned 128-bit objects.  This is useful for atomic
               updates of data structures exceeding one machine word in size.
               The compiler uses this instruction to implement **__sync**
               **Builtins**.  However, for **__atomic Builtins** operating on 128-bit
               integers, a library call is always used.
    
           **-msahf**
               This option enables generation of "SAHF" instructions in
               64-bit code.  Early Intel Pentium 4 CPUs with Intel 64
               support, prior to the introduction of Pentium 4 G1 step in
               December 2005, lacked the "LAHF" and "SAHF" instructions which
               are supported by AMD64.  These are load and store
               instructions, respectively, for certain status flags.  In
               64-bit mode, the "SAHF" instruction is used to optimize
               "fmod", "drem", and "remainder" built-in functions; see **Other**
               **Builtins** for details.
    
           **-mmovbe**
               This option enables use of the "movbe" instruction to
               implement "__builtin_bswap32" and "__builtin_bswap64".
    
           **-mshstk**
               The **-mshstk** option enables shadow stack built-in functions
               from x86 Control-flow Enforcement Technology (CET).
    
           **-mcrc32**
               This option enables built-in functions
               "__builtin_ia32_crc32qi", "__builtin_ia32_crc32hi",
               "__builtin_ia32_crc32si" and "__builtin_ia32_crc32di" to
               generate the "crc32" machine instruction.
    
           **-mrecip**
               This option enables use of "RCPSS" and "RSQRTSS" instructions
               (and their vectorized variants "RCPPS" and "RSQRTPS") with an
               additional Newton-Raphson step to increase precision instead
               of "DIVSS" and "SQRTSS" (and their vectorized variants) for
               single-precision floating-point arguments.  These instructions
               are generated only when **-funsafe-math-optimizations** is enabled
               together with **-ffinite-math-only** and **-fno-trapping-math**.  Note
               that while the throughput of the sequence is higher than the
               throughput of the non-reciprocal instruction, the precision of
               the sequence can be decreased by up to 2 ulp (i.e. the inverse
               of 1.0 equals 0.99999994).
    
               Note that GCC implements "1.0f/sqrtf(_x)"_ in terms of "RSQRTSS"
               (or "RSQRTPS") already with **-ffast-math**(or the above option
               combination), and doesn't need **-mrecip**.
    
               Also note that GCC emits the above sequence with additional
               Newton-Raphson step for vectorized single-float division and
               vectorized "sqrtf(_x)"_ already with **-ffast-math**(or the above
               option combination), and doesn't need **-mrecip**.
    
           **-mrecip=**_opt_
               This option controls which reciprocal estimate instructions
               may be used.  _opt_ is a comma-separated list of options, which
               may be preceded by a **!** to invert the option:
    
               **all** Enable all estimate instructions.
    
               **default**
                   Enable the default instructions, equivalent to **-mrecip**.
    
               **none**
                   Disable all estimate instructions, equivalent to
                   **-mno-recip**.
    
               **div** Enable the approximation for scalar division.
    
               **vec-div**
                   Enable the approximation for vectorized division.
    
               **sqrt**
                   Enable the approximation for scalar square root.
    
               **vec-sqrt**
                   Enable the approximation for vectorized square root.
    
               So, for example, **-mrecip=all,!sqrt** enables all of the
               reciprocal approximations, except for square root.
    
           **-mveclibabi=**_type_
               Specifies the ABI type to use for vectorizing intrinsics using
               an external library.  Supported values for _type_ are **svml** for
               the Intel short vector math library and **acml** for the AMD math
               core library.  To use this option, both **-ftree-vectorize** and
               **-funsafe-math-optimizations** have to be enabled, and an SVML or
               ACML ABI-compatible library must be specified at link time.
    
               GCC currently emits calls to "vmldExp2", "vmldLn2",
               "vmldLog102", "vmldPow2", "vmldTanh2", "vmldTan2",
               "vmldAtan2", "vmldAtanh2", "vmldCbrt2", "vmldSinh2",
               "vmldSin2", "vmldAsinh2", "vmldAsin2", "vmldCosh2",
               "vmldCos2", "vmldAcosh2", "vmldAcos2", "vmlsExp4", "vmlsLn4",
               "vmlsLog104", "vmlsPow4", "vmlsTanh4", "vmlsTan4",
               "vmlsAtan4", "vmlsAtanh4", "vmlsCbrt4", "vmlsSinh4",
               "vmlsSin4", "vmlsAsinh4", "vmlsAsin4", "vmlsCosh4",
               "vmlsCos4", "vmlsAcosh4" and "vmlsAcos4" for corresponding
               function type when **-mveclibabi=svml** is used, and "__vrd2_sin",
               "__vrd2_cos", "__vrd2_exp", "__vrd2_log", "__vrd2_log2",
               "__vrd2_log10", "__vrs4_sinf", "__vrs4_cosf", "__vrs4_expf",
               "__vrs4_logf", "__vrs4_log2f", "__vrs4_log10f" and
               "__vrs4_powf" for the corresponding function type when
               **-mveclibabi=acml** is used.
    
           **-mabi=**_name_
               Generate code for the specified calling convention.
               Permissible values are **sysv** for the ABI used on GNU/Linux and
               other systems, and **ms** for the Microsoft ABI.  The default is
               to use the Microsoft ABI when targeting Microsoft Windows and
               the SysV ABI on all other systems.  You can control this
               behavior for specific functions by using the function
               attributes "ms_abi" and "sysv_abi".
    
           **-mforce-indirect-call**
               Force all calls to functions to be indirect. This is useful
               when using Intel Processor Trace where it generates more
               precise timing information for function calls.
    
           **-mmanual-endbr**
               Insert ENDBR instruction at function entry only via the
               "cf_check" function attribute. This is useful when used with
               the option **-fcf-protection=branch** to control ENDBR insertion
               at the function entry.
    
           **-mcall-ms2sysv-xlogues**
               Due to differences in 64-bit ABIs, any Microsoft ABI function
               that calls a System V ABI function must consider RSI, RDI and
               XMM6-15 as clobbered.  By default, the code for saving and
               restoring these registers is emitted inline, resulting in
               fairly lengthy prologues and epilogues.  Using
               **-mcall-ms2sysv-xlogues** emits prologues and epilogues that use
               stubs in the static portion of libgcc to perform these saves
               and restores, thus reducing function size at the cost of a few
               extra instructions.
    
           **-mtls-dialect=**_type_
               Generate code to access thread-local storage using the **gnu** or
               **gnu2** conventions.  **gnu** is the conservative default; **gnu2** is
               more efficient, but it may add compile- and run-time
               requirements that cannot be satisfied on all systems.
    
           **-mpush-args**
           **-mno-push-args**
               Use PUSH operations to store outgoing parameters.  This method
               is shorter and usually equally fast as method using SUB/MOV
               operations and is enabled by default.  In some cases disabling
               it may improve performance because of improved scheduling and
               reduced dependencies.
    
           **-maccumulate-outgoing-args**
               If enabled, the maximum amount of space required for outgoing
               arguments is computed in the function prologue.  This is
               faster on most modern CPUs because of reduced dependencies,
               improved scheduling and reduced stack usage when the preferred
               stack boundary is not equal to 2.  The drawback is a notable
               increase in code size.  This switch implies **-mno-push-args**.
    
           **-mthreads**
               Support thread-safe exception handling on MinGW.  Programs
               that rely on thread-safe exception handling must compile and
               link all code with the **-mthreads** option.  When compiling,
               **-mthreads** defines **-D_MT** ; when linking, it links in a special
               thread helper library **-lmingwthrd** which cleans up per-thread
               exception-handling data.
    
           **-mms-bitfields**
           **-mno-ms-bitfields**
               Enable/disable bit-field layout compatible with the native
               Microsoft Windows compiler.
    
               If "packed" is used on a structure, or if bit-fields are used,
               it may be that the Microsoft ABI lays out the structure
               differently than the way GCC normally does.  Particularly when
               moving packed data between functions compiled with GCC and the
               native Microsoft compiler (either via function call or as data
               in a file), it may be necessary to access either format.
    
               This option is enabled by default for Microsoft Windows
               targets.  This behavior can also be controlled locally by use
               of variable or type attributes.  For more information, see **x86**
               **Variable Attributes** and **x86 Type Attributes**.
    
               The Microsoft structure layout algorithm is fairly simple with
               the exception of the bit-field packing.  The padding and
               alignment of members of structures and whether a bit-field can
               straddle a storage-unit boundary are determine by these rules:
    
               1. Structure members are stored sequentially in the order in
               which they are
                   declared: the first member has the lowest memory address
                   and the last member the highest.
    
               2. Every data object has an alignment requirement.  The
               alignment requirement
                   for all data except structures, unions, and arrays is
                   either the size of the object or the current packing size
                   (specified with either the "aligned" attribute or the
                   "pack" pragma), whichever is less.  For structures,
                   unions, and arrays, the alignment requirement is the
                   largest alignment requirement of its members.  Every
                   object is allocated an offset so that:
    
                           offset % alignment_requirement == 0
    
               3. Adjacent bit-fields are packed into the same 1-, 2-, or
               4-byte allocation
                   unit if the integral types are the same size and if the
                   next bit-field fits into the current allocation unit
                   without crossing the boundary imposed by the common
                   alignment requirements of the bit-fields.
    
               MSVC interprets zero-length bit-fields in the following ways:
    
               1. If a zero-length bit-field is inserted between two bit-
               fields that
                   are normally coalesced, the bit-fields are not coalesced.
    
                   For example:
    
                           struct
                            {
                              unsigned long bf_1 : 12;
                              unsigned long : 0;
                              unsigned long bf_2 : 12;
                            } t1;
    
                   The size of "t1" is 8 bytes with the zero-length bit-
                   field.  If the zero-length bit-field were removed, "t1"'s
                   size would be 4 bytes.
    
               2. If a zero-length bit-field is inserted after a bit-field,
               "foo", and the
                   alignment of the zero-length bit-field is greater than the
                   member that follows it, "bar", "bar" is aligned as the
                   type of the zero-length bit-field.
    
                   For example:
    
                           struct
                            {
                              char foo : 4;
                              short : 0;
                              char bar;
                            } t2;
    
                           struct
                            {
                              char foo : 4;
                              short : 0;
                              double bar;
                            } t3;
    
                   For "t2", "bar" is placed at offset 2, rather than offset
                   1.  Accordingly, the size of "t2" is 4.  For "t3", the
                   zero-length bit-field does not affect the alignment of
                   "bar" or, as a result, the size of the structure.
    
                   Taking this into account, it is important to note the
                   following:
    
                   1. If a zero-length bit-field follows a normal bit-field,
                   the type of the
                       zero-length bit-field may affect the alignment of the
                       structure as whole. For example, "t2" has a size of 4
                       bytes, since the zero-length bit-field follows a
                       normal bit-field, and is of type short.
    
                   2. Even if a zero-length bit-field is not followed by a
                   normal bit-field, it may
                       still affect the alignment of the structure:
    
                               struct
                                {
                                  char foo : 6;
                                  long : 0;
                                } t4;
    
                       Here, "t4" takes up 4 bytes.
    
               3. Zero-length bit-fields following non-bit-field members are
               ignored:
                           struct
                            {
                              char foo;
                              long : 0;
                              char bar;
                            } t5;
    
                   Here, "t5" takes up 2 bytes.
    
           **-mno-align-stringops**
               Do not align the destination of inlined string operations.
               This switch reduces code size and improves performance in case
               the destination is already aligned, but GCC doesn't know about
               it.
    
           **-minline-all-stringops**
               By default GCC inlines string operations only when the
               destination is known to be aligned to least a 4-byte boundary.
               This enables more inlining and increases code size, but may
               improve performance of code that depends on fast "memcpy",
               "strlen", and "memset" for short lengths.
    
           **-minline-stringops-dynamically**
               For string operations of unknown size, use run-time checks
               with inline code for small blocks and a library call for large
               blocks.
    
           **-mstringop-strategy=**_alg_
               Override the internal decision heuristic for the particular
               algorithm to use for inlining string operations.  The allowed
               values for _alg_ are:
    
               **rep_byte**
               **rep_4byte**
               **rep_8byte**
                   Expand using i386 "rep" prefix of the specified size.
    
               **byte_loop**
               **loop**
               **unrolled_loop**
                   Expand into an inline loop.
    
               **libcall**
                   Always use a library call.
    
           **-mmemcpy-strategy=**_strategy_
               Override the internal decision heuristic to decide if
               "__builtin_memcpy" should be inlined and what inline algorithm
               to use when the expected size of the copy operation is known.
               _strategy_ is a comma-separated list of _alg_ :_max_size_ :_dest_align_
               triplets.  _alg_ is specified in **-mstringop-strategy** , _max_size_
               specifies the max byte size with which inline algorithm _alg_ is
               allowed.  For the last triplet, the _max_size_ must be "-1". The
               _max_size_ of the triplets in the list must be specified in
               increasing order.  The minimal byte size for _alg_ is 0 for the
               first triplet and "_max_size + 1"_ of the preceding range.
    
           **-mmemset-strategy=**_strategy_
               The option is similar to **-mmemcpy-strategy=** except that it is
               to control "__builtin_memset" expansion.
    
           **-momit-leaf-frame-pointer**
               Don't keep the frame pointer in a register for leaf functions.
               This avoids the instructions to save, set up, and restore
               frame pointers and makes an extra register available in leaf
               functions.  The option **-fomit-leaf-frame-pointer** removes the
               frame pointer for leaf functions, which might make debugging
               harder.
    
           **-mtls-direct-seg-refs**
           **-mno-tls-direct-seg-refs**
               Controls whether TLS variables may be accessed with offsets
               from the TLS segment register (%gs for 32-bit, %fs for
               64-bit), or whether the thread base pointer must be added.
               Whether or not this is valid depends on the operating system,
               and whether it maps the segment to cover the entire TLS area.
    
               For systems that use the GNU C Library, the default is on.
    
           **-msse2avx**
           **-mno-sse2avx**
               Specify that the assembler should encode SSE instructions with
               VEX prefix.  The option **-mavx** turns this on by default.
    
           **-mfentry**
           **-mno-fentry**
               If profiling is active (**-pg**), put the profiling counter call
               before the prologue.  Note: On x86 architectures the attribute
               "ms_hook_prologue" isn't possible at the moment for **-mfentry**
               and **-pg**.
    
           **-mrecord-mcount**
           **-mno-record-mcount**
               If profiling is active (**-pg**), generate a __mcount_loc section
               that contains pointers to each profiling call. This is useful
               for automatically patching and out calls.
    
           **-mnop-mcount**
           **-mno-nop-mcount**
               If profiling is active (**-pg**), generate the calls to the
               profiling functions as NOPs. This is useful when they should
               be patched in later dynamically. This is likely only useful
               together with **-mrecord-mcount**.
    
           **-minstrument-return=**_type_
               Instrument function exit in -pg -mfentry instrumented
               functions with call to specified function. This only
               instruments true returns ending with ret, but not sibling
               calls ending with jump. Valid types are _none_ to not
               instrument, _call_ to generate a call to __return__, or _nop5_ to
               generate a 5 byte nop.
    
           **-mrecord-return**
           **-mno-record-return**
               Generate a __return_loc section pointing to all return
               instrumentation code.
    
           **-mfentry-name=**_name_
               Set name of __fentry__ symbol called at function entry for -pg
               -mfentry functions.
    
           **-mfentry-section=**_name_
               Set name of section to record -mrecord-mcount calls (default
               __mcount_loc).
    
           **-mskip-rax-setup**
           **-mno-skip-rax-setup**
               When generating code for the x86-64 architecture with SSE
               extensions disabled, **-mskip-rax-setup** can be used to skip
               setting up RAX register when there are no variable arguments
               passed in vector registers.
    
               **Warning:** Since RAX register is used to avoid unnecessarily
               saving vector registers on stack when passing variable
               arguments, the impacts of this option are callees may waste
               some stack space, misbehave or jump to a random location.  GCC
               4.4 or newer don't have those issues, regardless the RAX
               register value.
    
           **-m8bit-idiv**
           **-mno-8bit-idiv**
               On some processors, like Intel Atom, 8-bit unsigned integer
               divide is much faster than 32-bit/64-bit integer divide.  This
               option generates a run-time check.  If both dividend and
               divisor are within range of 0 to 255, 8-bit unsigned integer
               divide is used instead of 32-bit/64-bit integer divide.
    
           **-mavx256-split-unaligned-load**
           **-mavx256-split-unaligned-store**
               Split 32-byte AVX unaligned load and store.
    
           **-mstack-protector-guard=**_guard_
           **-mstack-protector-guard-reg=**_reg_
           **-mstack-protector-guard-offset=**_offset_
               Generate stack protection code using canary at _guard_.
               Supported locations are **global** for global canary or **tls** for
               per-thread canary in the TLS block (the default).  This option
               has effect only when **-fstack-protector** or
               **-fstack-protector-all** is specified.
    
               With the latter choice the options
               **-mstack-protector-guard-reg=**_reg_ and
               **-mstack-protector-guard-offset=**_offset_ furthermore specify
               which segment register (%fs or %gs) to use as base register
               for reading the canary, and from what offset from that base
               register.  The default for those is as specified in the
               relevant ABI.
    
           **-mgeneral-regs-only**
               Generate code that uses only the general-purpose registers.
               This prevents the compiler from using floating-point, vector,
               mask and bound registers.
    
           **-mindirect-branch=**_choice_
               Convert indirect call and jump with _choice_.  The default is
               **keep** , which keeps indirect call and jump unmodified.  **thunk**
               converts indirect call and jump to call and return thunk.
               **thunk-inline** converts indirect call and jump to inlined call
               and return thunk.  **thunk-extern** converts indirect call and
               jump to external call and return thunk provided in a separate
               object file.  You can control this behavior for a specific
               function by using the function attribute "indirect_branch".
    
               Note that **-mcmodel=large** is incompatible with
               **-mindirect-branch=thunk** and **-mindirect-branch=thunk-extern**
               since the thunk function may not be reachable in the large
               code model.
    
               Note that **-mindirect-branch=thunk-extern** is compatible with
               **-fcf-protection=branch** since the external thunk can be made to
               enable control-flow check.
    
           **-mfunction-return=**_choice_
               Convert function return with _choice_.  The default is **keep** ,
               which keeps function return unmodified.  **thunk** converts
               function return to call and return thunk.  **thunk-inline**
               converts function return to inlined call and return thunk.
               **thunk-extern** converts function return to external call and
               return thunk provided in a separate object file.  You can
               control this behavior for a specific function by using the
               function attribute "function_return".
    
               Note that **-mindirect-return=thunk-extern** is compatible with
               **-fcf-protection=branch** since the external thunk can be made to
               enable control-flow check.
    
               Note that **-mcmodel=large** is incompatible with
               **-mfunction-return=thunk** and **-mfunction-return=thunk-extern**
               since the thunk function may not be reachable in the large
               code model.
    
           **-mindirect-branch-register**
               Force indirect call and jump via register.
    
           These **-m** switches are supported in addition to the above on x86-64
           processors in 64-bit environments.
    
           **-m32**
           **-m64**
           **-mx32**
           **-m16**
           **-miamcu**
               Generate code for a 16-bit, 32-bit or 64-bit environment.  The
               **-m32** option sets "int", "long", and pointer types to 32 bits,
               and generates code that runs on any i386 system.
    
               The **-m64** option sets "int" to 32 bits and "long" and pointer
               types to 64 bits, and generates code for the x86-64
               architecture.  For Darwin only the **-m64** option also turns off
               the **-fno-pic** and **-mdynamic-no-pic** options.
    
               The **-mx32** option sets "int", "long", and pointer types to 32
               bits, and generates code for the x86-64 architecture.
    
               The **-m16** option is the same as **-m32** , except for that it
               outputs the ".code16gcc" assembly directive at the beginning
               of the assembly output so that the binary can run in 16-bit
               mode.
    
               The **-miamcu** option generates code which conforms to Intel MCU
               psABI.  It requires the **-m32** option to be turned on.
    
           **-mno-red-zone**
               Do not use a so-called "red zone" for x86-64 code.  The red
               zone is mandated by the x86-64 ABI; it is a 128-byte area
               beyond the location of the stack pointer that is not modified
               by signal or interrupt handlers and therefore can be used for
               temporary data without adjusting the stack pointer.  The flag
               **-mno-red-zone** disables this red zone.
    
           **-mcmodel=small**
               Generate code for the small code model: the program and its
               symbols must be linked in the lower 2 GB of the address space.
               Pointers are 64 bits.  Programs can be statically or
               dynamically linked.  This is the default code model.
    
           **-mcmodel=kernel**
               Generate code for the kernel code model.  The kernel runs in
               the negative 2 GB of the address space.  This model has to be
               used for Linux kernel code.
    
           **-mcmodel=medium**
               Generate code for the medium model: the program is linked in
               the lower 2 GB of the address space.  Small symbols are also
               placed there.  Symbols with sizes larger than
               **-mlarge-data-threshold** are put into large data or BSS sections
               and can be located above 2GB.  Programs can be statically or
               dynamically linked.
    
           **-mcmodel=large**
               Generate code for the large model.  This model makes no
               assumptions about addresses and sizes of sections.
    
           **-maddress-mode=long**
               Generate code for long address mode.  This is only supported
               for 64-bit and x32 environments.  It is the default address
               mode for 64-bit environments.
    
           **-maddress-mode=short**
               Generate code for short address mode.  This is only supported
               for 32-bit and x32 environments.  It is the default address
               mode for 32-bit and x32 environments.
    
           _x86 Windows Options_
    
           These additional options are available for Microsoft Windows
           targets:
    
           **-mconsole**
               This option specifies that a console application is to be
               generated, by instructing the linker to set the PE header
               subsystem type required for console applications.  This option
               is available for Cygwin and MinGW targets and is enabled by
               default on those targets.
    
           **-mdll**
               This option is available for Cygwin and MinGW targets.  It
               specifies that a DLL---a dynamic link library---is to be
               generated, enabling the selection of the required runtime
               startup object and entry point.
    
           **-mnop-fun-dllimport**
               This option is available for Cygwin and MinGW targets.  It
               specifies that the "dllimport" attribute should be ignored.
    
           **-mthread**
               This option is available for MinGW targets. It specifies that
               MinGW-specific thread support is to be used.
    
           **-municode**
               This option is available for MinGW-w64 targets.  It causes the
               "UNICODE" preprocessor macro to be predefined, and chooses
               Unicode-capable runtime startup code.
    
           **-mwin32**
               This option is available for Cygwin and MinGW targets.  It
               specifies that the typical Microsoft Windows predefined macros
               are to be set in the pre-processor, but does not influence the
               choice of runtime library/startup code.
    
           **-mwindows**
               This option is available for Cygwin and MinGW targets.  It
               specifies that a GUI application is to be generated by
               instructing the linker to set the PE header subsystem type
               appropriately.
    
           **-fno-set-stack-executable**
               This option is available for MinGW targets. It specifies that
               the executable flag for the stack used by nested functions
               isn't set. This is necessary for binaries running in kernel
               mode of Microsoft Windows, as there the User32 API, which is
               used to set executable privileges, isn't available.
    
           **-fwritable-relocated-rdata**
               This option is available for MinGW and Cygwin targets.  It
               specifies that relocated-data in read-only section is put into
               the ".data" section.  This is a necessary for older runtimes
               not supporting modification of ".rdata" sections for pseudo-
               relocation.
    
           **-mpe-aligned-commons**
               This option is available for Cygwin and MinGW targets.  It
               specifies that the GNU extension to the PE file format that
               permits the correct alignment of COMMON variables should be
               used when generating code.  It is enabled by default if GCC
               detects that the target assembler found during configuration
               supports the feature.
    
           See also under **x86 Options** for standard options.
    
           _Xstormy16 Options_
    
           These options are defined for Xstormy16:
    
           **-msim**
               Choose startup files and linker script suitable for the
               simulator.
    
           _Xtensa Options_
    
           These options are supported for Xtensa targets:
    
           **-mconst16**
           **-mno-const16**
               Enable or disable use of "CONST16" instructions for loading
               constant values.  The "CONST16" instruction is currently not a
               standard option from Tensilica.  When enabled, "CONST16"
               instructions are always used in place of the standard "L32R"
               instructions.  The use of "CONST16" is enabled by default only
               if the "L32R" instruction is not available.
    
           **-mfused-madd**
           **-mno-fused-madd**
               Enable or disable use of fused multiply/add and
               multiply/subtract instructions in the floating-point option.
               This has no effect if the floating-point option is not also
               enabled.  Disabling fused multiply/add and multiply/subtract
               instructions forces the compiler to use separate instructions
               for the multiply and add/subtract operations.  This may be
               desirable in some cases where strict IEEE 754-compliant
               results are required: the fused multiply add/subtract
               instructions do not round the intermediate result, thereby
               producing results with _more_ bits of precision than specified
               by the IEEE standard.  Disabling fused multiply add/subtract
               instructions also ensures that the program output is not
               sensitive to the compiler's ability to combine multiply and
               add/subtract operations.
    
           **-mserialize-volatile**
           **-mno-serialize-volatile**
               When this option is enabled, GCC inserts "MEMW" instructions
               before "volatile" memory references to guarantee sequential
               consistency.  The default is **-mserialize-volatile**.  Use
               **-mno-serialize-volatile** to omit the "MEMW" instructions.
    
           **-mforce-no-pic**
               For targets, like GNU/Linux, where all user-mode Xtensa code
               must be position-independent code (PIC), this option disables
               PIC for compiling kernel code.
    
           **-mtext-section-literals**
           **-mno-text-section-literals**
               These options control the treatment of literal pools.  The
               default is **-mno-text-section-literals** , which places literals
               in a separate section in the output file.  This allows the
               literal pool to be placed in a data RAM/ROM, and it also
               allows the linker to combine literal pools from separate
               object files to remove redundant literals and improve code
               size.  With **-mtext-section-literals** , the literals are
               interspersed in the text section in order to keep them as
               close as possible to their references.  This may be necessary
               for large assembly files.  Literals for each function are
               placed right before that function.
    
           **-mauto-litpools**
           **-mno-auto-litpools**
               These options control the treatment of literal pools.  The
               default is **-mno-auto-litpools** , which places literals in a
               separate section in the output file unless
               **-mtext-section-literals** is used.  With **-mauto-litpools** the
               literals are interspersed in the text section by the
               assembler.  Compiler does not produce explicit ".literal"
               directives and loads literals into registers with "MOVI"
               instructions instead of "L32R" to let the assembler do
               relaxation and place literals as necessary.  This option
               allows assembler to create several literal pools per function
               and assemble very big functions, which may not be possible
               with **-mtext-section-literals**.
    
           **-mtarget-align**
           **-mno-target-align**
               When this option is enabled, GCC instructs the assembler to
               automatically align instructions to reduce branch penalties at
               the expense of some code density.  The assembler attempts to
               widen density instructions to align branch targets and the
               instructions following call instructions.  If there are not
               enough preceding safe density instructions to align a target,
               no widening is performed.  The default is **-mtarget-align**.
               These options do not affect the treatment of auto-aligned
               instructions like "LOOP", which the assembler always aligns,
               either by widening density instructions or by inserting NOP
               instructions.
    
           **-mlongcalls**
           **-mno-longcalls**
               When this option is enabled, GCC instructs the assembler to
               translate direct calls to indirect calls unless it can
               determine that the target of a direct call is in the range
               allowed by the call instruction.  This translation typically
               occurs for calls to functions in other source files.
               Specifically, the assembler translates a direct "CALL"
               instruction into an "L32R" followed by a "CALLX" instruction.
               The default is **-mno-longcalls**.  This option should be used in
               programs where the call target can potentially be out of
               range.  This option is implemented in the assembler, not the
               compiler, so the assembly code generated by GCC still shows
               direct call instructions---look at the disassembled object
               code to see the actual instructions.  Note that the assembler
               uses an indirect call for every cross-file call, not just
               those that really are out of range.
    
           _zSeries Options_
    
           These are listed under
    


## ENVIRONMENT



           This section describes several environment variables that affect
           how GCC operates.  Some of them work by specifying directories or
           prefixes to use when searching for various kinds of files.  Some
           are used to specify other aspects of the compilation environment.
    
           Note that you can also specify places to search using options such
           as **-B** , **-I** and **-L**.  These take precedence over places specified
           using environment variables, which in turn take precedence over
           those specified by the configuration of GCC.
    
           **LANG**
           **LC_CTYPE**
           **LC_MESSAGES**
           **LC_ALL**
               These environment variables control the way that GCC uses
               localization information which allows GCC to work with
               different national conventions.  GCC inspects the locale
               categories **LC_CTYPE** and **LC_MESSAGES** if it has been configured
               to do so.  These locale categories can be set to any value
               supported by your installation.  A typical value is
               **en_GB.UTF-8** for English in the United Kingdom encoded in
               UTF-8.
    
               The **LC_CTYPE** environment variable specifies character
               classification.  GCC uses it to determine the character
               boundaries in a string; this is needed for some multibyte
               encodings that contain quote and escape characters that are
               otherwise interpreted as a string end or escape.
    
               The **LC_MESSAGES** environment variable specifies the language to
               use in diagnostic messages.
    
               If the **LC_ALL** environment variable is set, it overrides the
               value of **LC_CTYPE** and **LC_MESSAGES** ; otherwise, **LC_CTYPE** and
               **LC_MESSAGES** default to the value of the **LANG** environment
               variable.  If none of these variables are set, GCC defaults to
               traditional C English behavior.
    
           **TMPDIR**
               If **TMPDIR** is set, it specifies the directory to use for
               temporary files.  GCC uses temporary files to hold the output
               of one stage of compilation which is to be used as input to
               the next stage: for example, the output of the preprocessor,
               which is the input to the compiler proper.
    
           **GCC_COMPARE_DEBUG**
               Setting **GCC_COMPARE_DEBUG** is nearly equivalent to passing
               **-fcompare-debug** to the compiler driver.  See the documentation
               of this option for more details.
    
           **GCC_EXEC_PREFIX**
               If **GCC_EXEC_PREFIX** is set, it specifies a prefix to use in the
               names of the subprograms executed by the compiler.  No slash
               is added when this prefix is combined with the name of a
               subprogram, but you can specify a prefix that ends with a
               slash if you wish.
    
               If **GCC_EXEC_PREFIX** is not set, GCC attempts to figure out an
               appropriate prefix to use based on the pathname it is invoked
               with.
    
               If GCC cannot find the subprogram using the specified prefix,
               it tries looking in the usual places for the subprogram.
    
               The default value of **GCC_EXEC_PREFIX** is _prefix/lib/gcc/_ where
               _prefix_ is the prefix to the installed compiler. In many cases
               _prefix_ is the value of "prefix" when you ran the _configure_
               script.
    
               Other prefixes specified with **-B** take precedence over this
               prefix.
    
               This prefix is also used for finding files such as _crt0.o_ that
               are used for linking.
    
               In addition, the prefix is used in an unusual way in finding
               the directories to search for header files.  For each of the
               standard directories whose name normally begins with
               **/usr/local/lib/gcc**(more precisely, with the value of
               **GCC_INCLUDE_DIR**), GCC tries replacing that beginning with the
               specified prefix to produce an alternate directory name.
               Thus, with **-Bfoo/** , GCC searches _foo/bar_ just before it
               searches the standard directory _/usr/local/lib/bar_.  If a
               standard directory begins with the configured _prefix_ then the
               value of _prefix_ is replaced by **GCC_EXEC_PREFIX** when looking
               for header files.
    
           **COMPILER_PATH**
               The value of **COMPILER_PATH** is a colon-separated list of
               directories, much like **PATH**.  GCC tries the directories thus
               specified when searching for subprograms, if it cannot find
               the subprograms using **GCC_EXEC_PREFIX**.
    
           **LIBRARY_PATH**
               The value of **LIBRARY_PATH** is a colon-separated list of
               directories, much like **PATH**.  When configured as a native
               compiler, GCC tries the directories thus specified when
               searching for special linker files, if it cannot find them
               using **GCC_EXEC_PREFIX**.  Linking using GCC also uses these
               directories when searching for ordinary libraries for the **-l**
               option (but directories specified with **-L** come first).
    
           **LANG**
               This variable is used to pass locale information to the
               compiler.  One way in which this information is used is to
               determine the character set to be used when character
               literals, string literals and comments are parsed in C and
               C++.  When the compiler is configured to allow multibyte
               characters, the following values for **LANG** are recognized:
    
               **C-JIS**
                   Recognize JIS characters.
    
               **C-SJIS**
                   Recognize SJIS characters.
    
               **C-EUCJP**
                   Recognize EUCJP characters.
    
               If **LANG** is not defined, or if it has some other value, then
               the compiler uses "mblen" and "mbtowc" as defined by the
               default locale to recognize and translate multibyte
               characters.
    
           Some additional environment variables affect the behavior of the
           preprocessor.
    
           **CPATH**
           **C_INCLUDE_PATH**
           **CPLUS_INCLUDE_PATH**
           **OBJC_INCLUDE_PATH**
               Each variable's value is a list of directories separated by a
               special character, much like **PATH** , in which to look for header
               files.  The special character, "PATH_SEPARATOR", is target-
               dependent and determined at GCC build time.  For Microsoft
               Windows-based targets it is a semicolon, and for almost all
               other targets it is a colon.
    
               **CPATH** specifies a list of directories to be searched as if
               specified with **-I** , but after any paths given with **-I** options
               on the command line.  This environment variable is used
               regardless of which language is being preprocessed.
    
               The remaining environment variables apply only when
               preprocessing the particular language indicated.  Each
               specifies a list of directories to be searched as if specified
               with **-isystem** , but after any paths given with **-isystem** options
               on the command line.
    
               In all these variables, an empty element instructs the
               compiler to search its current working directory.  Empty
               elements can appear at the beginning or end of a path.  For
               instance, if the value of **CPATH** is ":/special/include", that
               has the same effect as **-I. -I/special/include**.
    
           **DEPENDENCIES_OUTPUT**
               If this variable is set, its value specifies how to output
               dependencies for Make based on the non-system header files
               processed by the compiler.  System header files are ignored in
               the dependency output.
    
               The value of **DEPENDENCIES_OUTPUT** can be just a file name, in
               which case the Make rules are written to that file, guessing
               the target name from the source file name.  Or the value can
               have the form _file target_ , in which case the rules are written
               to file _file_ using _target_ as the target name.
    
               In other words, this environment variable is equivalent to
               combining the options **-MM** and **-MF** , with an optional **-MT** switch
               too.
    
           **SUNPRO_DEPENDENCIES**
               This variable is the same as **DEPENDENCIES_OUTPUT**(see above),
               except that system header files are not ignored, so it implies
               **-M** rather than **-MM**.  However, the dependence on the main input
               file is omitted.
    
           **SOURCE_DATE_EPOCH**
               If this variable is set, its value specifies a UNIX timestamp
               to be used in replacement of the current date and time in the
               "__DATE__" and "__TIME__" macros, so that the embedded
               timestamps become reproducible.
    
               The value of **SOURCE_DATE_EPOCH** must be a UNIX timestamp,
               defined as the number of seconds (excluding leap seconds)
               since 01 Jan 1970 00:00:00 represented in ASCII; identical to
               the output of **@command{date +%s**} on GNU/Linux and other
               systems that support the %s extension in the "date" command.
    
               The value should be a known timestamp such as the last
               modification time of the source or package and it should be
               set by the build process.
    


## BUGS



           For instructions on reporting bugs, see
           <**https://gcc.gnu.org/bugs/ **>.
    


## FOOTNOTES



           1.  On some systems, **gcc -shared** needs to build supplementary stub
               code for constructors to work.  On multi-libbed systems, **gcc**
               **-shared** must select the correct support libraries to link
               against.  Failing to supply the correct flags may lead to
               subtle defects.  Supplying them in cases where they are not
               necessary is innocuous.
    


* * *