[PATCH] D138044: AMDGPU/GlobalISel: Fix crash after mad/fma_mix fails selection

[Petar Avramovic via Phabricator via llvm-commits]

Petar.Avramovic created this revision.
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When selectVOP3PMadMixModsImpl fails, it can still create new copy instr
via selectVOP3ModsImpl. When selectG_FMA_FMAD gives up, new copy instr
will remain dead but will not be automatically removed.
InstructionSelect does not check if instructions created during selection
are dead.
Such dead copy doesn't have register class on dst operand and causes crash.
Fix is to first peek through selectVOP3ModsImpl and see if Src is G_FPEXT,
from here selection will succeed and we use regular selectVOP3ModsImpl.


https://reviews.llvm.org/D138044

Files:
  llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp
  llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.h
  llvm/test/CodeGen/AMDGPU/GlobalISel/combine-fma-add-mul.ll

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