[llvm] KnownBits: refine KnownBits::srem for high-bits (PR #109121)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> Alive2 proof: https://alive2.llvm.org/ce/z/WcDkSX

Please provide a generic proof:
https://llvm.org/docs/InstCombineContributorGuide.html#use-generic-values-in-proofs

https://github.com/llvm/llvm-project/pull/109121