[llvm] [AMDGPU] CodeGen for SMEM instructions (PR #75579)

[Piotr Sobczak via llvm-commits]

piotrAMD wrote:

There is some duplication with #75492 (the part about the restricted offset) but I see why you need it in both patches and it looks the common parts will merge cleanly anyway.

https://github.com/llvm/llvm-project/pull/75579