[all-commits] [llvm/llvm-project] 3bee9b: AMDGPU/GFX12: Fix s_barrier_signal_isfirst for sin...

Nicolai Hähnle via All-commits all-commits at lists.llvm.org
Thu Jun 19 11:23:10 PDT 2025


  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3bee9ba0156ee130fa88379a5a89de0812936a3d
      https://github.com/llvm/llvm-project/commit/3bee9ba0156ee130fa88379a5a89de0812936a3d
  Author: Nicolai Hähnle <nicolai.haehnle at amd.com>
  Date:   2025-06-19 (Thu, 19 Jun 2025)

  Changed paths:
    M llvm/docs/AMDGPUUsage.rst
    M llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp
    M llvm/lib/Target/AMDGPU/SIISelLowering.cpp
    M llvm/lib/Target/AMDGPU/SOPInstructions.td
    M llvm/test/CodeGen/AMDGPU/insert-skips-gfx12.mir
    A llvm/test/CodeGen/AMDGPU/llvm.amdgcn.s.barrier.signal.isfirst.ll

  Log Message:
  -----------
  AMDGPU/GFX12: Fix s_barrier_signal_isfirst for single-wave workgroups (#143634)

Barrier instructions are no-ops in single-wave workgroups. This includes
s_barrier_signal_isfirst, which will leave SCC unmodified.

Model this correctly (via an implicit use of SCC) and ensure SCC==1
before the barrier instruction (if the wave is the only one of the
workgroup, then it is the first).

---------

Co-authored-by: Matt Arsenault <arsenm2 at gmail.com>



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