[all-commits] [llvm/llvm-project] fd82e9: AMDGPU: Mark the SCC def dead when merging lane masks

[Matt Arsenault via All-commits]

  Branch: refs/heads/users/arsenm/amdgpu/lane-mask-merge-dead-scc
  Home:   https://github.com/llvm/llvm-project
  Commit: fd82e9020637f16a2b7a186d564f9e839b9e85b6
      https://github.com/llvm/llvm-project/commit/fd82e9020637f16a2b7a186d564f9e839b9e85b6
  Author: Matt Arsenault <Matthew.Arsenault at amd.com>
  Date:   2026-09-24 (Thu, 24 Sep 2026)

  Changed paths:
    M llvm/lib/Target/AMDGPU/AMDGPUGlobalISelDivergenceLowering.cpp
    M llvm/lib/Target/AMDGPU/SILowerI1Copies.cpp
    M llvm/test/CodeGen/AMDGPU/GlobalISel/divergence-divergent-i1-phis-no-lane-mask-merging.ll
    M llvm/test/CodeGen/AMDGPU/GlobalISel/divergence-divergent-i1-phis-no-lane-mask-merging.mir
    M llvm/test/CodeGen/AMDGPU/GlobalISel/divergence-divergent-i1-used-outside-loop.ll
    M llvm/test/CodeGen/AMDGPU/GlobalISel/divergence-divergent-i1-used-outside-loop.mir
    M llvm/test/CodeGen/AMDGPU/GlobalISel/divergence-structurizer.ll
    M llvm/test/CodeGen/AMDGPU/GlobalISel/divergence-structurizer.mir
    M llvm/test/CodeGen/AMDGPU/GlobalISel/divergence-temporal-divergent-i1.mir
    M llvm/test/CodeGen/AMDGPU/i1-divergent-phi-fix-sgpr-copies-assert.mir
    M llvm/test/CodeGen/AMDGPU/lower-i1-copies-clear-kills.mir
    M llvm/test/CodeGen/AMDGPU/lower-i1-copies-implicit-def-unstructured-loop.mir
    M llvm/test/CodeGen/AMDGPU/mmra.ll
    M llvm/test/CodeGen/AMDGPU/si-annotate-nested-control-flows.ll
    M llvm/test/CodeGen/AMDGPU/si-lower-i1-copies-order-of-phi-incomings.mir
    M llvm/test/CodeGen/AMDGPU/si-lower-i1-copies.mir

  Log Message:
  -----------
  AMDGPU: Mark the SCC def dead when merging lane masks

The scalar and/or/xor used to merge a lane mask with EXEC clobber SCC, but
nothing reads the result. Avoid depending on later dead flag inference.

Co-Authored-By: Claude Opus 5 <noreply at anthropic.com>



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