[llvm] [ConstraintElim] Simplify cmp after uadd.sat/usub.sat (PR #135603)

[Nikita Popov via llvm-commits]

nikic wrote:

@el-ev Would it be possible to fix this separately from adding support for simplifying usub.sat? These are not really related...

https://github.com/llvm/llvm-project/pull/135603