[all-commits] [llvm/llvm-project] 178caa: [AMDGPU] Apply occupancy-aware register allocation...

[Syadus Sefat via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 178caae5c39dbf9a03f52f9a3d7edc11d3b02405
      https://github.com/llvm/llvm-project/commit/178caae5c39dbf9a03f52f9a3d7edc11d3b02405
  Author: Syadus Sefat <42645939+mssefat at users.noreply.github.com>
  Date:   2026-09-24 (Thu, 24 Sep 2026)

  Changed paths:
    M llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp
    M llvm/lib/Target/AMDGPU/SIRegisterInfo.h
    A llvm/test/CodeGen/AMDGPU/llvm.amdgcn.mfma.anti-hints.mir

  Log Message:
  -----------
  [AMDGPU] Apply occupancy-aware register allocation anti-hints (#218074)

This PR overrides applyRegAllocationAntiHints in the SIRegisterInfo so
anti-hints
try to protect against occupancy regression. Changing of the allocation
order is
confined to the vgpr budget of the current occupancy. Reordering is
skipped when
the allocation is near the budget (80% of the target-occupancy vgpr
limit or 95%
of the current occupancy vgpr limit). Below this, the anti-hinted
registers are
moved behind the non-anti-hinted ones within the budget.
## Stack
PR **3/4**. Depends on #218073. Next: Add anti-hints in
GCNPreRAOptimizatioins #218075.



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