[llvm] [NVPTX] Add max/minimumnum to ISel (PR #155804)

[Princeton Ferro via llvm-commits]

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Prince781 wrote:

Can we also add support for the 3-input min/max instructions using fminimumnum/fmaximumnum? You would need to add custom nodes in `NVPTXISD`.

https://github.com/llvm/llvm-project/pull/155804