[llvm] [BasicBlockUtils] Fixed LoopInfo update in UpdateAnalysisInformation() (PR #177147)

[Yevgeny Rouban via llvm-commits]

yrouban wrote:

> TBH I don't follow the logic of this change at all. This could use more explanation (either in code comments or the PR description).

Thank you for comments. I have added to the test commit message an explanation of what test becomes after SplitBlockPredecessors(catch_dest, { loop }, "", DT, LI) and what is the irreducible loop we have. So the fix is to not change the header of the irreducible loop but to destroy it. Please suggest any other changes you see to clarify the fix.

https://github.com/llvm/llvm-project/pull/177147