[llvm] [InstSimplify] Use multi-op replacement when simplify `select` (PR #121708)

[via llvm-commits]

goldsteinn wrote:

> Can you please check the compile-time impact?

Compile time data: https://llvm-compile-time-tracker.com/compare.php?from=c56b74315f57acb1b285ddc77b07031b773549b7&to=0c2ed79c43b8f7833566172e691dc702a1a2a5aa&stat=instructions%3Au

Maybe a bit on `kimwitu++ 	52485M 	52624M (+0.27%)`, but other than that seems fine (should also improve without the extra calls after rebasing on your patch).

https://github.com/llvm/llvm-project/pull/121708