[all-commits] [llvm/llvm-project] 51a095: [InstCombine][X86] Only demand used bits for PSHUF...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 51a095121e11c757f05492e345f84f4b3b84188b
      https://github.com/llvm/llvm-project/commit/51a095121e11c757f05492e345f84f4b3b84188b
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2024-08-28 (Wed, 28 Aug 2024)

  Changed paths:
    M llvm/lib/Target/X86/X86InstCombineIntrinsic.cpp
    M llvm/test/Transforms/InstCombine/X86/x86-pshufb-inseltpoison.ll
    M llvm/test/Transforms/InstCombine/X86/x86-pshufb.ll

  Log Message:
  -----------
  [InstCombine][X86] Only demand used bits for PSHUFB mask values (#106377)

(V)PSHUFB only uses the sign bit (for zeroing) and the lower 4 bits (to index per-lane byte 0-15) - so use SimplifyDemandedBits to ignore anything touching the remaining bits.

Fixes #106256



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