[PATCH] D155652: AMDGPU: Fold fsub [+-0] into fneg when folding source modifiers

[Matt Arsenault via Phabricator via llvm-commits]

arsenm created this revision.
arsenm added reviewers: AMDGPU, foad, rampitec, Pierre-vh, b-sumner.
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This isn't always folded to fneg for a freestanding fsub depending on
 the denormal mode. When matching source modifiers, we're implicitly
 canonicalizing the input so we can fold it here.

      

Doesn't bother handling the VOP3P case since it's only relevant with
DAZ, which nobody really uses with f16.


https://reviews.llvm.org/D155652

Files:
  llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp
  llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp
  llvm/test/CodeGen/AMDGPU/fneg-combines.ll
  llvm/test/CodeGen/AMDGPU/fneg-combines.new.ll
  llvm/test/CodeGen/AMDGPU/fsub-as-fneg-src-modifier.ll
  llvm/test/CodeGen/AMDGPU/llvm.exp.ll

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