[clang] Hlsl or intrinsic (PR #128979)

[Damyan Pepper via cfe-commits]

https://github.com/damyanp commented:

Congrats on getting your first change in!  Some notes, mainly around comments, although we probably also want to fix the clang-format issue (if there is one).

https://github.com/llvm/llvm-project/pull/128979