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

[Stanislav Mekhanoshin via llvm-commits]

rampitec wrote:

> This broke UBSan bots
> 
> ```
> RUN: at line 2: /b/sanitizer-x86_64-linux-fast/build/llvm_build_asan_ubsan/bin/llc -march=amdgcn -mcpu=verde -verify-machineinstrs -show-mc-encoding < /b/sanitizer-x86_64-linux-fast/build/llvm-project/llvm/test/CodeGen/AMDGPU/llvm.amdgcn.s.setreg.ll | /b/sanitizer-x86_64-linux-fast/build/llvm_build_asan_ubsan/bin/FileCheck -check-prefixes=GFX6 /b/sanitizer-x86_64-linux-fast/build/llvm-project/llvm/test/CodeGen/AMDGPU/llvm.amdgcn.s.setreg.ll
> + /b/sanitizer-x86_64-linux-fast/build/llvm_build_asan_ubsan/bin/llc -march=amdgcn -mcpu=verde -verify-machineinstrs -show-mc-encoding
> + /b/sanitizer-x86_64-linux-fast/build/llvm_build_asan_ubsan/bin/FileCheck -check-prefixes=GFX6 /b/sanitizer-x86_64-linux-fast/build/llvm-project/llvm/test/CodeGen/AMDGPU/llvm.amdgcn.s.setreg.ll
> /b/sanitizer-x86_64-linux-fast/build/llvm-project/llvm/lib/Target/AMDGPU/SIModeRegister.cpp:288:27: runtime error: shift exponent 32 is too large for 32-bit type 'int'
> SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /b/sanitizer-x86_64-linux-fast/build/llvm-project/llvm/lib/Target/AMDGPU/SIModeRegister.cpp:288:27 in 
> FileCheck error: '<stdin>' is empty.
> FileCheck command line:  /b/sanitizer-x86_64-linux-fast/build/llvm_build_asan_ubsan/bin/FileCheck -check-prefixes=GFX6 /b/sanitizer-x86_64-linux-fast/build/llvm-project/llvm/test/CodeGen/AMDGPU/llvm.amdgcn.s.setreg.ll
> ```

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/77997