[llvm] [ConstraintElim] Check the other signedness when hasSameSign (PR #128168)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

Could you also re-title this PR "[ConstraintElim] Teach checkAndReplaceCondition about samesign", as there are already other patches that teach other parts of ConstraintElim about samesign, and we want to disambiguate.

https://github.com/llvm/llvm-project/pull/128168