[all-commits] [llvm/llvm-project] cebc96: [AArch64] Match ZIP and UZP starting from undef el...

[David Green via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: cebc9609d8cdc6f488693cd8e4a616b935b38d2c
      https://github.com/llvm/llvm-project/commit/cebc9609d8cdc6f488693cd8e4a616b935b38d2c
  Author: David Green <david.green at arm.com>
  Date:   2024-04-23 (Tue, 23 Apr 2024)

  Changed paths:
    M llvm/lib/Target/AArch64/AArch64PerfectShuffle.h
    M llvm/test/CodeGen/AArch64/arm64-uzp.ll
    M llvm/test/CodeGen/AArch64/arm64-zip.ll

  Log Message:
  -----------
  [AArch64] Match ZIP and UZP starting from undef elements. (#89578)

In case the first element of a zip/uzp mask is undef, the isZIPMask and
isUZPMask functions have a 50% chance of picking the wrong
"WhichResult", meaning they don't match a zip/uzp where they could. This
patch alters the matching code to first check for the first non-undef
element, to try and get WhichResult correct.



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