[all-commits] [llvm/llvm-project] 42ff31: [X86] combineTargetShuffle - fold VPERMV3(HI, MASK, ...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 42ff31aea5828a491269b4db1ba5cff6fef7ca60
      https://github.com/llvm/llvm-project/commit/42ff31aea5828a491269b4db1ba5cff6fef7ca60
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2025-02-15 (Sat, 15 Feb 2025)

  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/any_extend_vector_inreg_of_broadcast_from_memory.ll
    M llvm/test/CodeGen/X86/avx512-shuffles/partial_permute.ll
    M llvm/test/CodeGen/X86/vector-interleaved-load-i16-stride-6.ll
    M llvm/test/CodeGen/X86/vector-interleaved-load-i32-stride-3.ll
    M llvm/test/CodeGen/X86/vector-interleaved-load-i32-stride-7.ll
    M llvm/test/CodeGen/X86/zero_extend_vector_inreg_of_broadcast.ll
    M llvm/test/CodeGen/X86/zero_extend_vector_inreg_of_broadcast_from_memory.ll

  Log Message:
  -----------
  [X86] combineTargetShuffle - fold VPERMV3(HI,MASK,LO) -> VPERMV(COMMUTE(MASK),CONCAT(LO,HI)) (#127199)

We already handle the simpler VPERMV3(LO,MASK,HI) fold which can reuse
the (widened) mask, this attempts to match the flipped concatenation,
and commutes the mask to handle the flip.

I've limited this to cases where we can extract the constant mask for
commutation, a more general solution would XOR the MSB of the shuffle
mask indices to commute, but this almost never constant folds away after
lowering so the benefit was minimal.



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