[all-commits] [llvm/llvm-project] ed38d6: PeepholeOpt: Handle subregister compose when looki...

[Matt Arsenault via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ed38d6702f7695092c9486016e2504f8c6bfef37
      https://github.com/llvm/llvm-project/commit/ed38d6702f7695092c9486016e2504f8c6bfef37
  Author: Matt Arsenault <Matthew.Arsenault at amd.com>
  Date:   2025-02-18 (Tue, 18 Feb 2025)

  Changed paths:
    M llvm/lib/CodeGen/PeepholeOptimizer.cpp
    M llvm/test/CodeGen/AMDGPU/GlobalISel/extractelement.ll
    M llvm/test/CodeGen/AMDGPU/issue92561-restore-undef-scc-verifier-error.ll
    M llvm/test/CodeGen/AMDGPU/peephole-opt-fold-reg-sequence-subreg.mir

  Log Message:
  -----------
  PeepholeOpt: Handle subregister compose when looking through reg_sequence (#127051)

Previously this would give up on folding subregister copies through
a reg_sequence if the input operand already had a subregister index.
d246cc618adc52fdbd69d44a2a375c8af97b6106 stopped introducing these
subregister uses, and this is the first step to lifting that restriction.

I was expecting to be able to implement this only purely with compose /
reverse compose, but I wasn't able to make it work so relies on testing
the lanemasks for whether the copy reads a subset of the input.



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