[all-commits] [llvm/llvm-project] 28233b: [AMDGPU] New AMDGPUInsertSingleUseVDST pass (#72388)

[Jay Foad via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 28233b11ac0efd28ab1f6c83842342d2e7f0a4d3
      https://github.com/llvm/llvm-project/commit/28233b11ac0efd28ab1f6c83842342d2e7f0a4d3
  Author: Jay Foad <jay.foad at amd.com>
  Date:   2023-11-24 (Fri, 24 Nov 2023)

  Changed paths:
    M llvm/lib/Target/AMDGPU/AMDGPU.h
    A llvm/lib/Target/AMDGPU/AMDGPUInsertSingleUseVDST.cpp
    M llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
    M llvm/lib/Target/AMDGPU/CMakeLists.txt
    A llvm/test/CodeGen/AMDGPU/insert-singleuse-vdst.mir

  Log Message:
  -----------
  [AMDGPU] New AMDGPUInsertSingleUseVDST pass (#72388)

Add support for emitting GFX11.5 s_singleuse_vdst instructions. This is
a power saving feature whereby the compiler can annotate VALU
instructions whose results are known to have only a single use, so the
hardware can in some cases avoid writing the result back to VGPR RAM.

To begin with the pass is disabled by default because of one missing
feature: we need an exclusion list of opcodes that never qualify as
single-use producers and/or consumers. A future patch will implement
this and enable the pass by default.

---------

Co-authored-by: Scott Egerton <scott.egerton at amd.com>