[PATCH] D71974: [Attributor][WIP] Connect AAIsDead with AAUndefinedBehavior

[Stefanos Baziotis via Phabricator via llvm-commits]

baziotis added a comment.

Sorry for being late, this is an exam period so time is very limited. I saw again the problem and it changed a bit but it's similar. To be sure we're on the same page:
In this:

  define i32 @example(i1* %alloc) {
    %cond = load i1, i1* %alloc
    br i1 %cond, label %t, label %e
  t:
    ret i32 1
  e:
    ret i32 2
  }

The block of `br` initially is assumed live, but `AAIsDeadFunction::updateImpl()` is called, which, because the `br` is assumed UB, removes the block from the `AssumedLiveBlocks`.
`AAUB` looks only live instructions and the `br` now will never be live (also maybe the fact that we're removing - and it's the only place - messes with the monotony).

I think one solution is to only remove a block if it is known UB.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D71974/new/

https://reviews.llvm.org/D71974