[llvm] ConstraintElim: teach fact-transfer about samesign (PR #115893)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Probably makes sense to land https://github.com/llvm/llvm-project/pull/116867 first and then use it here...

https://github.com/llvm/llvm-project/pull/115893