[clang] [llvm] [NVPTX] Consolidate and cleanup various NVPTXISD nodes (NFC) (PR #145581)

[Thomas Raoux via cfe-commits]

ThomasRaoux wrote:

@AlexMaclean, this PR doesn't seem to be NFC. This generates different PTX than before. In particular I see extra `mov.b32 	%r, global_smem;` that seem to generate different sass and causes regressions in some Triton workloads.
Before this PR I would only have one of those moves, now I see multiple. I haven't debugged why yet.

Is this is something you have noticed?

https://github.com/llvm/llvm-project/pull/145581