GCC has the __builtin_cpu_supports() function on some architectures, so you may want to use that instead.

It's supported:

* on x86 since GCC 4.8

* on PowerPC since GCC 6 (you will also need glibc ≥ 2.23)

Documentation:

https://gcc.gnu.org/onlinedocs/gcc/x86-Built-in-Functions.ht...

https://gcc.gnu.org/onlinedocs/gcc/PowerPC-Built-in-Function...