[all-commits] [llvm/llvm-project] 62d77f: [X86] combineX86ShuffleChain - don't combine to VP...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 62d77fcb3cebe80b3cf88588b5f94778799e86f3
      https://github.com/llvm/llvm-project/commit/62d77fcb3cebe80b3cf88588b5f94778799e86f3
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2025-02-20 (Thu, 20 Feb 2025)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    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-i16-stride-7.ll
    M llvm/test/CodeGen/X86/vector-interleaved-store-i16-stride-4.ll
    M llvm/test/CodeGen/X86/vector-shuffle-128-v16.ll
    M llvm/test/CodeGen/X86/vector-shuffle-128-v8.ll
    M llvm/test/CodeGen/X86/vector-shuffle-256-v32.ll
    M llvm/test/CodeGen/X86/vector-shuffle-512-v64.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] combineX86ShuffleChain - don't combine to VPERM2W/VPERM2B from just any single variable mask (#127914)

Despite them being more expensive than other variable mask shuffles, we
were combining shuffle chains to VPERM2W/VPERM2B if any shuffle in the
chain was a variable shuffle - including very cheap shuffles like PSHUFB
or AND mask patterns.

This patch adjusts the BWI VPERMV3 threshold - it still always permits
the merge if the chain (of 2 or more shuffles) contains any
X86ISD::VPERMV/VPERMV3 shuffles (including DQ variants), but otherwise
only reduces the depth threshold based off the number of other variable
shuffles we'd fold away.



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