Integrate LLVM at llvm/llvm-project@ff81a2c95ddb
Integrate LLVM at llvm/llvm-project@ff81a2c95ddb

Updates LLVM usage to match
[ff81a2c95ddb](https://github.com/llvm/llvm-project/commit/ff81a2c95ddb)

PiperOrigin-RevId: 378745601

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