[llvm] [NVPTX] Add IR pass for FMA transformation in the llc pipeline (PR #154735)

[Alex MacLean via llvm-commits]

AlexMaclean wrote:

@nikic / @Artem-B Do either of you know if there is any existing support for LLVM IR level FMA-fusion? This seems broadly useful and maybe even like something that should be occurring in InstCombine (though I assume there is a good reason we don't do it there already)? 

https://github.com/llvm/llvm-project/pull/154735