[PATCH] D153717: [SCCP] replace valuestate.isConstant with helper isConstant

[luxufan via Phabricator via llvm-commits]

StephenFan created this revision.
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nikic added a comment.

This only makes a difference when the binop returns a poison result, right? I think it's unfortunate that this ends up replacing that with an undef value.

I think it would be good to introduce a new lattice value for poison, which allows us to explicitly represent this and avoid refining poison to undef. Especially in conjunction with D153718 <https://reviews.llvm.org/D153718>, which is kind of weird in we claim no undefs but the result is represented as undef.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D153717

Files:
  llvm/lib/Transforms/Utils/SCCPSolver.cpp
  llvm/test/Transforms/SCCP/binaryops-range-special-cases.ll
  llvm/test/Transforms/SCCP/ip-ranges-phis.ll
  llvm/test/Transforms/SCCP/overdefined-div.ll
  llvm/test/Transforms/SCCP/ub-shift.ll

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