[PATCH] D151069: [AMDGPU] Handle multiple occurences of an incoming value in break large PHIs

[Pierre van Houtryve via Phabricator via llvm-commits]

Pierre-vh created this revision.
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We naively broke all incoming values, assuming they'd be unique.
However it's not illegal to have multiple occurences of, e.g. `[BB0, V0]`
in a PHI node. What's illegal though is having the same basic block
multiple times but with different values, and it's exactly what the
transform caused. This broke in some rare applications where the pattern
arised.

Now we cache the `BasicBlock, Value` pairs we're breaking so we can reuse the values and preserve this invariant.

Solves SWDEV-399460


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D151069

Files:
  llvm/lib/Target/AMDGPU/AMDGPUCodeGenPrepare.cpp
  llvm/test/CodeGen/AMDGPU/amdgpu-codegenprepare-break-large-phis-heuristics.ll
  llvm/test/CodeGen/AMDGPU/amdgpu-codegenprepare-break-large-phis.ll

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