[llvm] [ConstraintElim] Fix poison check before adding intrinsic facts (PR #136291)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

I was hoping that we would have a proper solution (https://github.com/llvm/llvm-project/pull/80121, https://github.com/llvm/llvm-project/pull/136558) to this soon.

Extending this check to abs is problematic due to the interaction with the int_min_is_poison flag.

https://github.com/llvm/llvm-project/pull/136291