[llvm] [InstCombine] Support well-defined recurrences in isGuaranteedNotToBeUndefOrPoison (PR #150420)

[David Sherwood via llvm-commits]

https://github.com/david-arm commented:

This looks great now! I just had a comment about the use of `const_cast` that I hadn't spotted before - my apologies.

https://github.com/llvm/llvm-project/pull/150420