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| author | Drew Wock <ajwock@gmail.com> | 2020-01-15 12:51:42 -0500 |
|---|---|---|
| committer | Kevin P. Neal <kevin.neal@sas.com> | 2020-01-17 12:22:52 -0500 |
| commit | 0bcfafc5e71d4f636d456317a3a2e6fd903d4755 (patch) | |
| tree | 4d9c790fb791c403bdb8cd714ab140ab6d7410aa /llvm/lib/Bitcode/Writer/BitcodeWriter.cpp | |
| parent | f343544b813891387add8ef01406d36b82ed0a7e (diff) | |
| download | llvm-0bcfafc5e71d4f636d456317a3a2e6fd903d4755.zip llvm-0bcfafc5e71d4f636d456317a3a2e6fd903d4755.tar.gz llvm-0bcfafc5e71d4f636d456317a3a2e6fd903d4755.tar.bz2 | |
[SeparateConstOffsetFromGEP] Fix: sext(a) + sext(b) -> sext(a + b) matches add and sub instructions with one another
During the SeparateConstOffsetFromGEP pass, signed extensions are distributed
to the values that feed into them and then later recombined. The recombination
stage is somewhat problematic- it doesn't differ add and sub instructions
from another when matching the sext(a) +/- sext(b) -> sext(a +/- b) pattern
in some instances.
An example- the IR contains:
%unextendedA
%unextendedB
%subuAuB = unextendedA - unextendedB
%extA = extend A
%extB = extend B
%addeAeB = extA + extB
The problematic optimization will transform that into:
%unextendedA
%unextendedB
%subuAuB = unextendedA - unextendedB
%extA = extend A
%extB = extend B
%addeAeB = extend subuAuB ; Obviously not semantically equivalent to the IR input.
This patch fixes that.
Patch by Drew Wock <drew.wock@sas.com>
Differential Revision: https://reviews.llvm.org/D65967
Diffstat (limited to 'llvm/lib/Bitcode/Writer/BitcodeWriter.cpp')
0 files changed, 0 insertions, 0 deletions