[llvm] Reland "[SimplifyCFG] Check if the return instruction causes undefined behavior" (PR #76656)

[Quentin Dian via llvm-commits]

DianQK wrote:

> LGTM, but please wait until after LLVM 18 has branched to merge it. Please also perform the merge manually to avoid squashing the commits.

Okay, waiting until LLVM 19 is fine. Yes, I'm going to rebase and push.

https://github.com/llvm/llvm-project/pull/76656