[llvm] [AMDGPU] Folding imm offset in more cases for scratch access (PR #70634)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> For scratch load/store, our hardware only accept non-negative value in SGPR/VGPR. 

Should refine this to specify this is for MUBUF, scratch instructions do have signed offsets (we also still need to implement stack support using negative offsetting)




https://github.com/llvm/llvm-project/pull/70634