regexes don't generally belong as compiler builtins. Those are more suitable for language standard libraries or OS standards like POSIX.

If there were an ISA out there that had some kind of regular expression feature, those could conceivably be supported with builtins, though.

https://pubs.opengroup.org/onlinepubs/009696899/functions/re...

The dividing line between compiler builtin, language primitive, standard library or compiler runtime doesn't really exist if you don't want it to. They're all variations on the same theme.