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

[Florian Mayer via llvm-commits]

fmayer 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
```

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