[llvm] SelectionDAG: Expand fminimumnum/fmaximumnum for promote (PR #135614)

[YunQiang Su via llvm-commits]

wzssyqa wrote:

Yes. You are right, we can just claim that it is promoted.
Since for a ISD::FP_EXTEND Node, `SelectionDAG::isKnownNeverNaN` concludes that it won't be sNaN.

https://github.com/llvm/llvm-project/pull/135614