https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82926
Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED CC| |jakub at gcc dot gnu.org Resolution|--- |INVALID --- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> --- If it is __x86_64__ only, then the push/pop is totally useless, %rbx is like any other reg (for __i386__ too if not pic or when using a recent gcc). So just asm ("cpuid" : "=a" (*a), "=b" (*b), "=c" (*c), "=d" (*d) : "0" (op)); Or you could e.g. xchg %%ebx, %%esi and back for __i386__ instead of the push/pop, or, if for whatever weird reason you don't want to clobber %rbx for __x86_64__, you could e.g. subtract the red zone size from %rsp first, then push and after poping add back.