[SotCodeLaureate]

> the compiler will never emit ... instructions like PSHUFB or PUNPCKxx

These are most certainly generated by GCC from C++ code (no intrinsics and such) - can even provide an evidence in the form of a codebase with appropriate build flags.

Their use is rather straightforward I think, but still.

[duskwuff]

Huh, TIL. I guess compilers have gotten smarter since I last looked into this a decade or so ago. :)