[llvm] [LoopSimplifyCFG] Fix SCEV invalidation after removing dead exit (PR #127536)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Could you please provide some more info on what happens in the test case? Like what the problematic SCEVs are that currently don't get invalidated.

In particular I'd like to understand why neither the SCEV VH callback invalidation nor the existing forgetBlockAndLoopDispositions call cover this.

https://github.com/llvm/llvm-project/pull/127536