[llvm] AMDGPU/GlobalISel: Handle atomic sextload and zextload (PR #111721)

[Stanislav Mekhanoshin via llvm-commits]

rampitec wrote:

> > But patch adds several MUBUF_Pseudo_Load_Pats which are not covered by tests?
> 
> The only cases that might have missing coverage is extend to 16-bit register cases. In the DAG we didn't have legal 16-bit types on gfx6/7, but we could handle the loads here

I still think these added MUBUF patterns need at least some test coverage.

https://github.com/llvm/llvm-project/pull/111721