[llvm] [InstCombine] Fold select of clamped shifts (PR #114797)

[Yingwei Zheng via llvm-commits]

https://github.com/dtcxzyw commented:

Two questions about the alive2 proof:
1. please provide a generalized proof.
2. There are some freeze instructions in the proof. Should we add `isGuaranteedNotToBeUndefOrPoison` check?

BTW, I think we can generalize this fold with a recursive function like `simplifyWithCond`. We already handle equality predicates via `simplifyWithOpReplaced`.


https://github.com/llvm/llvm-project/pull/114797