[all-commits] [llvm/llvm-project] bdcaa0: [AArch64] match TRN starting from undef elements (...

[Philip Ginsbach-Chen via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: bdcaa0001a5081737b12b9ec0c284fe06002a97c
      https://github.com/llvm/llvm-project/commit/bdcaa0001a5081737b12b9ec0c284fe06002a97c
  Author: Philip Ginsbach-Chen <ginsbach at github.com>
  Date:   2025-11-19 (Wed, 19 Nov 2025)

  Changed paths:
    M llvm/lib/Target/AArch64/AArch64PerfectShuffle.h
    M llvm/test/CodeGen/AArch64/arm64-trn.ll
    M llvm/test/CodeGen/AArch64/insert-extend.ll
    M llvm/test/CodeGen/AArch64/reduce-shuffle.ll
    M llvm/test/CodeGen/AArch64/vldn_shuffle.ll

  Log Message:
  -----------
  [AArch64] match TRN starting from undef elements (#167955)

When the first element of a trn mask is undef, the `isTRNMask` function
assumes `WhichResult = 1`. That has a 50% chance of being wrong, so we
fail to match some valid trn1/trn2.

This patch introduces a more precise test to determine the correct value
of `WhichResult`, based on corresponding code in the `isZIPMask` and
`isUZPMask` functions.

- This change is based on #89578. I'd like to follow it up with a
further change along the lines of #167235.



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications