[all-commits] [llvm/llvm-project] 6dc23b: [SCEVExpander] Don't try to reuse SCEVUnknown valu...

[Nikita Popov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6dc23b70097e4135ecde33f49550b1f473a5c385
      https://github.com/llvm/llvm-project/commit/6dc23b70097e4135ecde33f49550b1f473a5c385
  Author: Nikita Popov <npopov at redhat.com>
  Date:   2024-11-11 (Mon, 11 Nov 2024)

  Changed paths:
    M llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
    M llvm/test/Transforms/LoopStrengthReduce/Power/incomplete-phi.ll
    M llvm/test/Transforms/LoopStrengthReduce/lsr-term-fold.ll
    M llvm/test/Transforms/LoopVectorize/pr45259.ll

  Log Message:
  -----------
  [SCEVExpander] Don't try to reuse SCEVUnknown values (#115141)

The expansion of a SCEVUnknown is trivial (it's just the wrapped value).
If we try to reuse an existing value it might be a more complex
expression that simplifies to the SCEVUnknown.

This is inspired by https://github.com/llvm/llvm-project/issues/114879,
because SCEVExpander replacing a constant with a phi node is just silly.
(I don't consider this a fix for that issue though.)



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