Introduce two command-line flags for the instrumentation pass to control whether the labels of pointers should be ignored in load and store instructions

The new command line flags are -dfsan-ignore-pointer-label-on-store and -dfsan-ignore-pointer-label-on-load. Their default value matches the current labelling scheme.

Additionally, the function __dfsan_union_load is marked as readonly.

Patch by Lorenzo Martignoni!

Differential Revision: http://llvm-reviews.chandlerc.com/D2187

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195382 91177308-0d34-0410-b5e6-96231b3b80d8
SHLD/SHRD are VectorPath (microcode) instructions known to have poor latency on certain architectures. While generating SHLD/SHRD instructions is acceptable when optimizing for size, optimizing for speed on these platforms should be implemented using alternative sequences of instructions composed of add, adc, shr, shl, or and lea which are directPath instructions. These alternative instructions not only have a lower latency but they also increase the decode bandwidth by allowing simultaneous decoding of a third directPath instruction.

AMD's processors family K7, K8, K10, K12, K15 and K16 are known to have SHLD/SHRD instructions with very poor latency. Optimization guides for these processors recommend using an alternative sequence of instructions. For these AMD's processors, I disabled folding (or (x << c) | (y >> (64 - c))) when we are not optimizing for size.

It might be beneficial to disable this folding for some of the Intel's processors. However, since I couldn't find specific recommendations regarding using SHLD/SHRD instructions on Intel's processors, I haven't disabled this peephole for Intel.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195383 91177308-0d34-0410-b5e6-96231b3b80d8
In Dwarf 3 (and Dwarf 2) attributes whose value are offsets into a
section use the form DW_FORM_data4 whilst in Dwarf 4 and later they
use the form DW_FORM_sec_offset.

This patch updates the places where such attributes are generated to
use the appropriate form depending on the Dwarf version. The DIE entries
affected have the following tags:
DW_AT_stmt_list, DW_AT_ranges, DW_AT_location, DW_AT_GNU_pubnames,
DW_AT_GNU_pubtypes, DW_AT_GNU_addr_base, DW_AT_GNU_ranges_base

It also adds a hidden command line option "--dwarf-version=<uint>"
to llc which allows the version of Dwarf to be generated to override
what is specified in the metadata; this makes it possible to update
existing tests to check the debugging information generated for both
Dwarf 4 (the default) and Dwarf 3 using the same metadata.

Patch (slightly modified) by Keith Walker!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195391 91177308-0d34-0410-b5e6-96231b3b80d8