[llvm] [LangRef] Specify NaN behavior more precisely (PR #66579)

[James Y Knight via llvm-commits]

jyknight wrote:

> I've updated the PR description. The PR title still seems fine?

Thanks. I tweaked the title slightly.

> Should I squash the commits?

No, you shouldn't -- squash happens _during_ the merge (via the button labeled "Squash and Merge"). I will press said button now.

https://github.com/llvm/llvm-project/pull/66579