[llvm] [X86] Improve FREEZE node elimination for SETCC operations (PR #192362)

[Phoebe Wang via llvm-commits]

phoebewang wrote:

> For the generic ISD::SETCC comparisons, we have to be more careful with fp comparisons as certain combos can create poison - are there any nodes that feed into X86ISD::SETCC/CARRY that can still create poison/undef?

By poison, do you mean when `fast fcmp` have INF/NAN in inputs? But I think it's poisonous only in IR semantics. For a `X86ISD::SETCC`, we should have a determined output no matter what inputs it has?

https://github.com/llvm/llvm-project/pull/192362