At least __attribute__((ifunc(..))) is common between clang and gcc. (E.g. no compiler conditionals are used in https://cgit.freebsd.org/src/tree/sys/arm64/incl

At least __attribute__((ifunc(..))) is common between clang and gcc. (E.g. no compiler conditionals are used in https://cgit.freebsd.org/src/tree/sys/arm64/include/ifunc.h https://cgit.freebsd.org/src/tree/sys/arm64/include/ifunc.h) The fancier high level stuff that automatically compiles multiple versions of a function, I'm not sure.