© CyberThor Studios Ltd.
Release Notes: LLVM FOR RENESAS RL78 10.0.0.202110
Release Notes: LLVM FOR RENESAS RL78 10.0.0.202110
8th of October, 2021
CyberThor Studios Ltd. is releasing the LLVM for Renesas RL78 10.0.0.202110, a cross compiler tool for
Renesas RL78 micro-controllers.
SALIENT FEATURES
The LLVM for Renesas RL78 10.0.0.202110 toolchain is based on:❖ LLVM 10.0.0 [released]❖ Compiler-rt 10.0.0 [released]❖ Libcxx 10.0.0 [released]❖ Libcxx-abi 10.0.0 [released]❖ Newlib 3.1.0 [released]❖ GDB 7.8.2 [released]
LLVM RL78 comes with significant performance improvements (both code size and speed) compared to GCC
RL78. It also comes with support for latest language standards: full support for C17 and C++17 andexperimental support for the C2x (next C standard) and partial support for C++20.
The latest patches are applied to the LLVM sources.

ABOUT LLVM FOR RENESAS RL78 10.0.0.202110
Release Version:

LLVM for Renesas RL78 10.0.0.202110

Release Date:

8th of October, 2021
Ubuntu 18.04 or later (or compatible distribution)

Platforms Supported:
Windows 7 or later
Language:

C, C++

Targets:

G23, G1X, I1X, D1X, LIN MCP, F1X, and L1X

Object File Format:

ELF

CHANGES IN LLVM FOR RENESAS RL78 10.0.0.202110
This toolchain is the successor of GCC RL78 toolchain, and it is meant as a direct replacement to GCC RL78.
This section describes the fixes made in the LLVM for Renesas RL78 10.0.0.202110 release.
1. [Bug Fix] Align attribute issue.
_attribute_((aligned(alignment))) is not working for variables with automatic storage duration
when alignment > 2. This also affects std::experimental::simd introduced in C++17 and vectore_size
attribute: __attribute__ ((vector_size (N))).
The issue is now fixed
2. [Bug Fix] llvm-addr2line address interpretation issue.
The llvm-addr2line documentation states "llvm-addr2line interprets all addresses as hexadecimal andignores an optional 0x prefix". However, this is not true 0x prefix is required (not optional). This will be fixed
in a future release.
3.

Bug Fix] Assembly parsing issue of hex numbers followed by a dot and a number (e.g.: 0xffef2.4)

In case of bit manipulation instructions, it should be possible to specify an address followed by a dot thenumber of the bit to be modified. The dot is causing the parser to think this is a floating-point number
instead and handles it incorrectly.
4. [Improvement] LLVM now supports newlib nano library.
The nano version of newlib was added to the LLVM toolchain. Enabling the -fnewlib-nano option will toggle
the usage of the nano library version.
INSTALLER:
1. The LLVM FOR RENESAS RL78 10.0.0.202110 Installer onwards supports installations for all users(if administrator privileges are present), as well as installations for the current user only.
2. In both cases, the toolchain should be detected by compatible versions of e2 studio and should
integrate seamlessly with them.
Notes:
This installer does not provide an option to integrate the LLVM RL78 toolchain with e2 studio, as the e2studio IDE will automatically detect the LLVM RL78 toolchain installation on start-up for integration.
Alternatively, you may use the 'Toolchain Management' feature in e2 studio to achieve this.
For details on e2 studio please visit the following link below:
https://www.renesas.com/eu/en/software-tool/e-studio
There is no support in this installer to integrate toolchain with the HEW IDE.

KNOWN ISSUES IN LLVM FOR RENESAS RL78 10.0.0.202110
The following is a list of known issues for the tools we include for the LLVM for Renesas RL78 10.0.0.202110
toolchain:
1. Linker Map file generation
The map file generated by LLD has less information compared to the one generated by GNU LD. This will be
improved in future releases.
2. Assembly parsing of %lo16, %hi16 limited support.
When using %lo16, %hi16 operators only 2 basic operations are currently allowed, symbol + constant andsymbol - constant.
For example:.short %lo16(_my_symbol) + %lo16(my_const)
The parse will be enhanced in future versions to support more complex expressions.
3. Assembly parsing issue of callt instruction operand.
The assembly parser cannot handle any complex expressions as operands for callt instruction, only constantvalues are allowed at the moment.
4. Assembly parsing missing operand.
There is currently no assembly operand to extract 8-bit data from symbols in order to be used with MOV ES,#byte, MOV CS, #byte etc. Only immediate values can be used with those instructions at the moment. The
current workaround is to use %lo16, %hi16 to set the value in 16-bit register and then move the relevant
part in ES/CS. A new operand will be implemented in next release.
5. C++ debugging member access issue.
While debugging C++ projects It is sometimes necessary to use "this" pointer in order to access member
variables even in cases where there's no ambiguity and this could be implied.
6. -finput-charset=/-fexec-charset= unsupported character encodings.
Unlike GCC, Clang accepts only UTF-8 encoding (which is also the default) as valid arguments for -finputcharset and -fexec-charset options. More encoding will be added in future releases.
7. Linker script ASSERT command issue.
ASSERT command may fail erroneously in cases where it sections sizes are checked as it is executed before
final optimizations in the linker when the code size is reduced further. This will be fixed in next release.
8. Missing assembly listing support (-a[cdhlns] option in GNU AS).

There are no listing options implemented in LLVM at the moment. This will be implemented in a futureversion.
Current workaround is to use llvm-objdump to obtain a source code interleaved with assembly (-S, --sourceoption).
9. Linker script section ordering issue.
If the sections that have load or virtual memory address specified in the linker script are not in ascendingorder of the load memory address inside the linker script the link process will fail.
Please check Bug 47853 for more details.
10. Unsigned bitfields not supported.
Currently, there is no support for unsigned bitfields in LLVM. This will be implemented in a future release.
11. Binding of references to packed fields.
Creating references to struct members which are declared as packed, e.q. __attribute__ ((packed)), isincorrect as it can cause unaligned access issues. The compiler should return an error in this case however
this is not currently the case. This will be fixed in a future release.
12. Warnings generated using -mfar-rom option.
When using -mfar-rom the linker will generate several warnings like "warning: incompatible rodata area
flags...". The root cause of this issue is that there are no prebuilt libraries with this option. The same issue
exists in GCC with the corresponding option, -mes0, the differences being that GCC ignores the problem
silently. There are currently no known issues caused by this however this will be investigated further in next
release and handled accordingly.
13. llvm-objdump does not display symbol name instead of raw address where possible.
llvm-objdump is not displaying symbol names instead of raw address where possible. This makes thedisassembly slightly harder to read than in case of rl78-elf-objdump. This will be fixed in next release.
14. llvm-objdump missing features
llvm-objdump does not currently support -i and -g options supported by rl78-elf-objdump. This will be fixed
in a future release.
15. Inline assembly missing constraints and modifiers support for parameters.
Clang supports, in case of RL78, inline assembly constructs without parameters, e.q. asm(AssembleTemplate).
The extended syntax available in GCC, asm (AssemblerTemplate : OutputOperands : InputOperands :Clobbers : GotoLabels), is not currently supported. This will be fixed in the next release, however theconstraints will not be the same as in GCC.
16. lld may report wrong overlap between .text and .bss when no load memory region specified.

When no load memory region is specified for .text and for .bss the llld linker may report that the sections
overlap although they are in different memory areas.
The workaround is to add Load memory regions for the .text and the .bss sections.
17. llvm-size is using NOLOAD sections when determining the total size.
Currently, the lld NOLOAD sections are contributing to the object/executable size when calling llvm-size.
18. Other issues, non-specific to RL78
LLVM tries to be a complete replacement. As such there are still a couple of missing features from GCC
which will be implemented in future releases. In particular, the following issues should be noted:
lld: Information printed using --print-gc-sections is not as nice as when using the GNU ld. Bug 46783
llvm-ar: Errors when printing multiple members with the same name. Bug 42521
llvm-dwarfdump: Does not print section attribute flags yet. Bug 38488
llvm-nm: Unable to understand symbols built with gcc-lto Bug 41437
llvm-nm: Needs support for --line-numbers to llvm-nm Bug 40001
llvm-objcopy: Unknown argument '--change-section-address'. Bug 45217
llvm-objcopy: Objcopy zero-size section might cause huge binaries. Bug 46299
llvm-objdump: Prints wrong line number info for obj file compiled with -ffunction-sections. Bug 40703
llvm-objdump: Wrong behavior for non-relocatable objects when suing llvm-objdump with -r option. Bug
Bug 41901
llvm-readobj: Make GNU style symbol printing invalid symbol section indexes match GNU readelf Bug 43850
llvm-readelf: Relocation addends printed style does not match GNU readelf Bug 45235
llvm-string: Short option with argument grouping not GNU compatible Bug 42942
llvm-string: Allow "-<integer>" as an alias for "-n <integer>" Bug 42964
llvm-symbolizer: Shows incorrect source line info if --gc-sections used Bug 41124
llvm-symbolizer: llvm-addr2line does not exit when passed a non-existent file Bug 42754
19. Other issues
Finally, for better understanding regarding the status of the toolchain please visit https://bugs.llvm.org/ .
In particular, the following queries will help better understand the status of each tool.

https://bugs.llvm.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=CONFIRMED&
bug_status=REOPENED&component=ELF&product=lld&query_format=advanced&resolution=--https://bugs.llvm.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=CONFIRMED&
bug_status=REOPENED&component=llvm-ar&product=tools&query_format=advanced&resolution=--https://bugs.llvm.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=CONFIRMED&
bug_status=REOPENED&component=llvmdwarfdump&product=tools&query_format=advanced&resolution=--https://bugs.llvm.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=CONFIRMED&
bug_status=REOPENED&component=llvm-nm&product=tools&query_format=advanced&resolution=--https://bugs.llvm.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=CONFIRMED&
bug_status=REOPENED&component=llvmobjcopy%2Fstrip&product=tools&query_format=advanced&resolution=--https://bugs.llvm.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=CONFIRMED&
bug_status=REOPENED&component=llvm-objdump&product=tools&query_format=advanced&resolution=-https://bugs.llvm.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=CONFIRMED&
bug_status=REOPENED&component=llvm-readobj&product=tools&query_format=advanced&resolution=--https://bugs.llvm.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=CONFIRMED&
bug_status=REOPENED&component=llvm-size&product=tools&query_format=advanced&resolution=--https://bugs.llvm.org/buglist.cgi?bug_status=NEW&bug_status=CONFIRMED&bug_status=REOPENED&com
ponent=llvm-symbolizer&product=tools&query_format=advanced&resolution=---FREE SUPPORT FOR LLVM FOR RENESAS RL78 10.0.0.202110
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