[all-commits] [llvm/llvm-project] 41146b: [X86][SSE] combineX86ShuffleChain - attempt to rec...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 41146bfe82aecc79961c3de898cda02998172e4b
      https://github.com/llvm/llvm-project/commit/41146bfe82aecc79961c3de898cda02998172e4b
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2021-03-27 (Sat, 27 Mar 2021)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/horizontal-sum.ll

  Log Message:
  -----------
  [X86][SSE] combineX86ShuffleChain - attempt to recognise 'hidden' identity shuffles

See if the combined shuffle mask is equivalent to an identity shuffle, typically this is due to repeated LHS/RHS ops in horiz-ops, but isTargetShuffleEquivalent might see other patterns as well.

This is another small step towards getting rid of foldShuffleOfHorizOp and relying on canonicalizeShuffleMaskWithHorizOp and generic shuffle combining.