[PATCH] D71799: [Attributor] AAUndefinedBehavior: Check for branches on undef value.

[Stefanos Baziotis via Phabricator via llvm-commits]

baziotis created this revision.
baziotis added a reviewer: jdoerfert.
Herald added subscribers: llvm-commits, jfb, hiraditya.
Herald added a reviewer: sstefan1.
Herald added a project: LLVM.

A branch is considered UB if it depends on an undefined / uninitialized value.
At this point this handles the simplest possible UB branches in the form: `br i1 undef, ...`
Note that it really must `undef` there. If it is e.g.:

  %cond = icmp ne i32 undef, 0
  br i1 %cond, label %t, label %e

Then right now, undef is not propagated. We depend on `AAValueSimplify` for this.

So, I'm open to any suggestion as to how we can make this more sophisticated.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D71799

Files:
  llvm/lib/Transforms/IPO/Attributor.cpp
  llvm/test/Transforms/Attributor/undefined_behavior.ll

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