[all-commits] [llvm/llvm-project] 317c41: MachineUniformityAnalysis: Improve isConstantOrUnd...

[Petar Avramovic via All-commits]

  Branch: refs/heads/users/petar-avramovic/new-rbs-phis-with-undef
  Home:   https://github.com/llvm/llvm-project
  Commit: 317c41b80b26e55ee35c5859700d91d36e58cd2a
      https://github.com/llvm/llvm-project/commit/317c41b80b26e55ee35c5859700d91d36e58cd2a
  Author: Petar Avramovic <Petar.Avramovic at amd.com>
  Date:   2024-10-18 (Fri, 18 Oct 2024)

  Changed paths:
    M llvm/lib/CodeGen/MachineSSAContext.cpp
    M llvm/test/Analysis/UniformityAnalysis/AMDGPU/MIR/hidden-diverge-gmir.mir
    M llvm/test/Analysis/UniformityAnalysis/AMDGPU/MIR/hidden-loop-diverge.mir
    M llvm/test/Analysis/UniformityAnalysis/AMDGPU/MIR/uses-value-from-cycle.mir
    M llvm/test/CodeGen/AMDGPU/GlobalISel/divergence-structurizer.mir
    M llvm/test/CodeGen/AMDGPU/GlobalISel/regbankselect-mui-rb-legalize.mir
    M llvm/test/CodeGen/AMDGPU/GlobalISel/regbankselect-mui-rb-select.mir
    M llvm/test/CodeGen/AMDGPU/GlobalISel/regbankselect-mui.ll
    M llvm/test/CodeGen/AMDGPU/GlobalISel/regbankselect-mui.mir

  Log Message:
  -----------
  MachineUniformityAnalysis: Improve isConstantOrUndefValuePhi

Change existing code to match what LLVM-IR version is doing via
PHINode::hasConstantOrUndefValue.
Most notably this improves number of values that can be allocated
to sgpr in AMDGPU's RBSelect.
Common case here are phis that appear in structurize-cfg lowering
for cycles with multiple exits:
Undef incoming value is coming from block that reached cycle exit
condition, if other incoming is uniform keep the phi uniform despite
the fact it is joining values from pair of blocks that are entered
via divergent condition branch.



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