[llvm] [InstSimplify] Improve `simplifyICmpWithConstant` by using KnownBits info (PR #76221)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

What's the compile-time impact?

IIRC it was always too expensive to use KnownBits to simplify all icmps in simplifyICmpInst, which is why this is left to InstCombine, which computes KnownBits anyway.

https://github.com/llvm/llvm-project/pull/76221