[plq]

They have a computation to do, and they want to do it using a particular instruction. That's the only reason they are fiddling with the compiler. You would have to do so too, if you had decided to solve a problem at hand using a similar method.

The author is talking about a way to get a particular (version of) C/C++ compiler to emit the desired instruction. So I'd call this clang-18.1.0-specific but not C/C++-specific since this has nothing to do with the language.

Also such solutions are not portable nor stable since optimization behavior does change between compiler versions. As far as I can tell, they also would have to implement a compiler-level unit test that ensures that the desired machine code is emitted as toolchain versions change.