[all-commits] [llvm/llvm-project] f2e93d: [CVP] prevent propagating poison when substituting...

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  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: f2e93d10fe0c7a845254d35f59f47d439e9ff89b
      https://github.com/llvm/llvm-project/commit/f2e93d10fe0c7a845254d35f59f47d439e9ff89b
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2019-10-28 (Mon, 28 Oct 2019)

  Changed paths:
    M llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
    M llvm/test/Transforms/CorrelatedValuePropagation/phi-common-val.ll

  Log Message:
  -----------
  [CVP] prevent propagating poison when substituting edge values into a phi (PR43802)

This phi simplification transform was added with:
D45448

However as shown in PR43802:
https://bugs.llvm.org/show_bug.cgi?id=43802

...we must be careful not to propagate poison when we do the substitution.
There might be some more complicated analysis possible to retain the overflow flag,
but it should always be safe and easy to drop flags (we have similar behavior in
instcombine and other passes).

Differential Revision: https://reviews.llvm.org/D69442