[llvm] [AMDGPU] Sink uniform buffer address offsets into soffset (PR #160939)

[Krzysztof Drewniak via llvm-commits]

https://github.com/krzysz00 commented:

I figure this makes sense - though you might also want to look for ((divergent + uniform) + constant)

Does this need a GlobalISel version too? I forget where DAGtoDAG runs.

... the other cases are `voffset = sgpr` where you'll want to reset `voffset` to `0`.

(The end goal here is that, if we're !IDXEN, voffset == 0, and we know that everything's naturally aligned, we can promote BUFFER_LOAD_* to S_BUFFER_LOAD_*)

https://github.com/llvm/llvm-project/pull/160939