[llvm] [InstCombine] Propagate poison pow[i] (PR #146750)

[Luke Lau via llvm-commits]

lukel97 wrote:

Is it possible to handle this in ConstantFolding? That way IRBuilder etc. will automatically fold it to poison without the need to run InstSimplify, see: https://github.com/llvm/llvm-project/pull/141821#pullrequestreview-2876118659

https://github.com/llvm/llvm-project/pull/146750