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

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> 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.

Compile-time impact: http://llvm-compile-time-tracker.com/compare.php?from=1d4691a2338c816e18e0d7c7db9a6062dd89f68c&to=859aceb4b01b0f1d60847be303910f5702913b93&stat=instructions:u

I will move it into InstCombine.


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