[llvm] [DFAJumpThreading] Avoid exploring the paths that never come back (PR #85505)

[Nikita Popov via llvm-commits]

nikic wrote:

Can you please add something like `if (VerifyLoopInfo) LI->verify(DT)` and add `-verify-loop-info` to all the DFAJumpThreading tests? Can also mark the analysis as preserved.

https://github.com/llvm/llvm-project/pull/85505