[llvm] [SimplifyCFG] Prevent merging cbranch to cbranch if the branch probability from the first to second is too low. (PR #69375)

[Nicolai Hähnle via llvm-commits]

https://github.com/nhaehnle approved this pull request.

Thanks! I don't have better guidance on the threshold value either. The default choice seems pretty conservative which is probably a good thing. Perhaps somebody else wants to chime in, but this LGTM.

https://github.com/llvm/llvm-project/pull/69375