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

[Stefanos Baziotis via Phabricator via llvm-commits]

baziotis added a comment.

In D71799#1794768 <https://reviews.llvm.org/D71799#1794768>, @uenoku wrote:

> Sorry for my lack of words. I thought you were talking about in `updateImpl`. It can't happen **in updates** but can happen once reaches to a fix point.


I //am// talking about `updateImpl()`, the code above is inside `updateImpl()`. It seems true though that if it happens, then a fixpoint has been reached.
Essentially was assumption is that `AAValueSimplify` seems to return behave weirdly when the value `undef` (i.e. it returns `None` while an `undef` value might be known). So with that,
if it happens, we can deduce that the instruction is UB in `updateImpl()` and that pretty much solves the previous problems.


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