[all-commits] [llvm/llvm-project] e377dc: [AMDGPU] Max. WG size-induced occupancy limits max...

[Lucas Ramirez via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: e377dc4d38b69050a3301c68637d1b6dacaee3a9
      https://github.com/llvm/llvm-project/commit/e377dc4d38b69050a3301c68637d1b6dacaee3a9
  Author: Lucas Ramirez <11032120+lucas-rami at users.noreply.github.com>
  Date:   2025-05-01 (Thu, 01 May 2025)

  Changed paths:
    M llvm/lib/Target/AMDGPU/AMDGPUAttributor.cpp
    M llvm/lib/Target/AMDGPU/AMDGPUPromoteAlloca.cpp
    M llvm/lib/Target/AMDGPU/AMDGPUSubtarget.cpp
    M llvm/lib/Target/AMDGPU/AMDGPUSubtarget.h
    M llvm/test/CodeGen/AMDGPU/attr-amdgpu-flat-work-group-size.ll
    M llvm/test/CodeGen/AMDGPU/load-global-i16.ll
    M llvm/test/CodeGen/AMDGPU/schedule-regpressure-limit-clustering.ll

  Log Message:
  -----------
  [AMDGPU] Max. WG size-induced occupancy limits max. waves/EU (#137807)

The default maximum waves/EU returned by the family of
`AMDGPUSubtarget::getWavesPerEU` is currently the maximum number of
waves/EU supported by the subtarget (only a valid occupancy range in
"amdgpu-waves-per-eu" may lower that maximum). This ignores maximum
achievable occupancy imposed by flat workgroup size and LDS usage,
resulting in situations where `AMDGPUSubtarget::getWavesPerEU` produces
a maximum higher than the one from
`AMDGPUSubtarget::getOccupancyWithWorkGroupSizes`.

This limits the waves/EU range's maximum to the maximum achievable
occupancy derived from flat workgroup sizes and LDS usage. This only has
an impact on functions which restrict flat workgroup size with
"amdgpu-flat-work-group-size", since the default range of flat workgroup
sizes achieves the maximum number of waves/EU supported by the
subtarget.

Improvements to the handling of "amdgpu-waves-per-eu" are left for a
follow up PR (e.g., I think the attribute should be able to lower the
full range of waves/EU produced by these methods).



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