[all-commits] [llvm/llvm-project] 3e4ee7: [X86] Fold EXTRACT_SUBVECTOR(ONEUSE(EXTRACT_SUBVEC...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3e4ee76fe0a015e306b58f0d8c1565f9f06ff9c3
      https://github.com/llvm/llvm-project/commit/3e4ee76fe0a015e306b58f0d8c1565f9f06ff9c3
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2024-10-10 (Thu, 10 Oct 2024)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/any_extend_vector_inreg_of_broadcast.ll
    M llvm/test/CodeGen/X86/avx512-shuffles/partial_permute.ll
    M llvm/test/CodeGen/X86/kshift.ll
    M llvm/test/CodeGen/X86/vector-shuffle-512-v16.ll
    M llvm/test/CodeGen/X86/vector-shuffle-512-v8.ll
    M llvm/test/CodeGen/X86/zero_extend_vector_inreg_of_broadcast.ll

  Log Message:
  -----------
  [X86] Fold EXTRACT_SUBVECTOR(ONEUSE(EXTRACT_SUBVECTOR(V,C1))),C2) - EXTRACT_SUBVECTOR(V,C1+C2) (#111685)

Extract from the original source vector whenever possible.

This removes a number of dependency bottlenecks and helps a number of shuffle combining cases: either by allowing us to avoid a cross-lane variable shuffle on a slow target by keeping the instruction count below the threshold, or on fast targets make it easier to recognise that the subvectors all came form the same source.



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