[llvm] [SimplifyCFG] Transform switch to select when common bits uniquely identify one case (PR #145233)

[Yingwei Zheng via llvm-commits]

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

LGTM. We may generalize this pattern in the future since some "free" bits may be known. But I think the current implementation is enough to cover the motivating cases.


https://github.com/llvm/llvm-project/pull/145233