[PATCH] D151323: [AMDGPU] Switch to backwards scavenging in non-spill cases

[Jay Foad via Phabricator via llvm-commits]

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When the scavenger is not allowed to spill, the only difference between
forward and backward should be the heuristics used to pick an available
register. Forwards scavenging tries to pick a register that can be used
again later in the BB; backwards scavenging tries to pick one that can
be used earlier.

Backwards scavenging is preferred because it does not rely on accurate
kill flags.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D151323

Files:
  llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
  llvm/test/CodeGen/AMDGPU/accvgpr-copy.mir
  llvm/test/CodeGen/AMDGPU/llvm.amdgcn.mfma.bf16.ll
  llvm/test/CodeGen/AMDGPU/llvm.amdgcn.mfma.i8.ll
  llvm/test/CodeGen/AMDGPU/llvm.amdgcn.mfma.ll

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