[PATCH] D130040: [AMDGPU] Remove old operand from VOPC DPP

[Joe Nash via Phabricator via llvm-commits]

Joe_Nash added inline comments.


================
Comment at: llvm/lib/Target/AMDGPU/SIInstrInfo.cpp:5015
+    if (!DefinedRC)
+      return false;
     if (!isLegalRegOperand(MRI, OpInfo, *MO))
----------------
foad wrote:
> foad wrote:
> > I guess we want to return "true" here for a case like COPY, where the source operand should be a register but has no defined RC, but "false" for operands that should be immediates. Can we distinguish these cases by looking at the OpInfo?
> > 
> > Having said that, I guess returning false is OK for now. It's more conservative, just prevents some folding, and in the D122737 test case that does not matter because the unfolded copy get optimized away by register allocation anyway.
> Maybe `return OpInfo.OperandType == MCOI::OPERAND_UNKNOWN;`? That would preserve the existing behaviour for COPY.
Nice idea, this seems to work.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D130040/new/

https://reviews.llvm.org/D130040