[all-commits] [llvm/llvm-project] ccb983: [X86] LowerShift - lower vXi8 shifts of an uniform...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ccb9835edb4612f73abc9f13880ea671117347ce
      https://github.com/llvm/llvm-project/commit/ccb9835edb4612f73abc9f13880ea671117347ce
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2024-10-14 (Mon, 14 Oct 2024)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/vector-shift-lut.ll

  Log Message:
  -----------
  [X86] LowerShift - lower vXi8 shifts of an uniform constant using PSHUFB (#112175)

If each 128-bit vXi8 lane is shifting the same constant value, we can pre-compute the 8 valid shift results and use PSHUFB to act as a LUT with the shift amount.

Fixes #110317



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