[llvm] [CodeGen] Parse nusw flag (PR #138856)

[Pierre van Houtryve via llvm-commits]

Pierre-vh wrote:

### Merge activity

* **May 8, 4:38 AM EDT**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/138856).


https://github.com/llvm/llvm-project/pull/138856