[PATCH] D33257: [JumpThreading] Dont RAUW condition if guards in block

[Anna Thomas via Phabricator via llvm-commits]

anna created this revision.

We should not RAUW the condition if experimental.guard [1] is a use of that
condition. This is because LazyValueInfo may have used the guard to identify the
value of the condition. We cannot apply the value back to the guard and change
the behaviour of the guard. For example, by RAUWing and replacing the guard use,
we may change a guard from:
guard(false) to guard(true). This changes the guard behaviour from `always
deoptimizing` to `sometimes deoptimizing`, and incorrectly affects the program semantics.

[1] http://llvm.org/docs/LangRef.html#llvm-experimental-guard-intrinsic


https://reviews.llvm.org/D33257

Files:
  lib/Transforms/Scalar/JumpThreading.cpp
  test/Transforms/JumpThreading/guards.ll

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