[llvm] [AMDGPU] Sign extend simm16 in setreg intrinsic (PR #77997)

[Stanislav Mekhanoshin via llvm-commits]

rampitec wrote:

> Thanks. The culprit is not the patch itself, but the added test has uncovered pre-existing problem:
> 
> ```
>  unsigned Mask = ((1 << Width) - 1) << Offset;
> ```
> 
> The test runs this part of code with Width == 32 which overflows unsigned int.

https://github.com/llvm/llvm-project/pull/78492

https://github.com/llvm/llvm-project/pull/77997