[PATCH] D28885: AMDGPU: Disable some fneg combines unless nsz

[Matt Arsenault via Phabricator via llvm-commits]

arsenm created this revision.
Herald added a reviewer: tstellarAMD.
Herald added subscribers: tony-tye, yaxunl, nhaehnle, wdng, kzhuravl.

For -(x + y) -> (-x) + (-y), if x == -y, this would
change the result from -0.0 to 0.0. Since the fma/fmad
combine is an extension of this problem it also
applies there.

      

fmul should be fine, and I don't think any of the unary
operators or conversions should be a problem either.


https://reviews.llvm.org/D28885

Files:
  lib/Target/AMDGPU/AMDGPUISelLowering.cpp
  lib/Target/AMDGPU/AMDGPUISelLowering.h
  test/CodeGen/AMDGPU/fneg-combines.ll
  test/CodeGen/AMDGPU/select-fabs-fneg-extract.ll

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