[all-commits] [llvm/llvm-project] 49c5ce: [X86] Improve support for vXi8 arithmetic shifts, ...

[David Majnemer via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 49c5cebb2966d5e8f0784370d818023a1054e189
      https://github.com/llvm/llvm-project/commit/49c5cebb2966d5e8f0784370d818023a1054e189
  Author: David Majnemer <david.majnemer at gmail.com>
  Date:   2024-09-16 (Mon, 16 Sep 2024)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/vector-shift-ashr-128.ll
    M llvm/test/CodeGen/X86/vector-shift-ashr-256.ll
    M llvm/test/CodeGen/X86/vector-shift-ashr-512.ll
    M llvm/test/CodeGen/X86/vector-shift-lshr-128.ll
    M llvm/test/CodeGen/X86/vector-shift-lshr-256.ll
    M llvm/test/CodeGen/X86/vector-shift-shl-128.ll
    M llvm/test/CodeGen/X86/vector-shift-shl-256.ll
    M llvm/test/CodeGen/X86/vector-shift-shl-512.ll

  Log Message:
  -----------
  [X86] Improve support for vXi8 arithmetic shifts, logical left shifts

Use SWAR techniques for arithmetic shifts: we use the same technique as
logical right shift but with an additional step of sign extending the
result.

Also, use the logical shift left technique even on AVX512 as vpmovzxbw
and vpmovwb are actually quite expensive.



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