[llvm] [NVPTX] Support slct for sign-based selects (PR #214860)

[Justin Fargnoli via llvm-commits]

https://github.com/justinfargnoli commented:

SASS diff: https://godbolt.org/z/3WqsnYdn9

I think this transformation may not be worthwhile on modern architectures. 

https://github.com/llvm/llvm-project/pull/214860