[PATCH] D49425: [MemorySSAUpdater] Update Phi operands after trivial Phi elimination

[Alexandros Lamprineas via Phabricator via llvm-commits]

labrinea added a comment.

A few remarks:

- `SmallVector<WeakVH, 8> PhiOps` fixes the bug on its own (without the rest changes)  and I am wondering why..
- When we mark a block as visited why do we cache it? When the recursion ends we might trivially remove the Phi. In that case the second cache insertion for the same key block should fail, no?
- Do we ever reach the `PHIExistsButNeedsUpdate` case? Is it when a Phi existed beforehand, meaning we did not create it? I can't think of another way to reach that state.
- Interestingly enough the reproducer only made opt crash in bitcode form and not in IR form.


https://reviews.llvm.org/D49425