[all-commits] [llvm/llvm-project] 9d60e9: [AMDGPU] Use poison instead of undef for non-deman...

[Nikita Popov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 9d60e95bcdce44fcf592bfcc9f847640b1bf6e5d
      https://github.com/llvm/llvm-project/commit/9d60e95bcdce44fcf592bfcc9f847640b1bf6e5d
  Author: Nikita Popov <npopov at redhat.com>
  Date:   2023-12-20 (Wed, 20 Dec 2023)

  Changed paths:
    M llvm/lib/Target/AMDGPU/AMDGPUInstCombineIntrinsic.cpp
    M llvm/test/Transforms/InstCombine/AMDGPU/amdgcn-demanded-vector-elts-inseltpoison.ll
    M llvm/test/Transforms/InstCombine/AMDGPU/amdgcn-demanded-vector-elts.ll

  Log Message:
  -----------
  [AMDGPU] Use poison instead of undef for non-demanded elements (#75914)

Return poison instead of undef for non-demanded lanes in the AMDGPU
demanded element simplification hook.

Also bail out of dmask is 0, as this case has special semantics:

> If DMASK==0, the TA overrides DMASK=1 and puts zeros in VGPR followed by
> LWE status if exists. TFE status is not generated since the fetch is dropped.