Integrate LLVM at llvm/llvm-project@31b8a1dc46d2
Integrate LLVM at llvm/llvm-project@31b8a1dc46d2

Updates LLVM usage to match
[31b8a1dc46d2](https://github.com/llvm/llvm-project/commit/31b8a1dc46d2)

PiperOrigin-RevId: 438931053

google-research/structured-additive-IR,google-research/structured-additive-IR