[llvm] IR: handle FP predicates in CmpPredicate::getMatching (PR #122924)

[Florian Hahn via llvm-commits]

https://github.com/fhahn approved this pull request.

LGTM, thanks.

Looks like this fixed all related crashes I was seeing on the unreduced reproducer

https://github.com/llvm/llvm-project/pull/122924