https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117952
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- +/* If we are compiling with GCC where %EBX register is fixed, then the + driver will just ignore -march and -mtune "native" target and will leave + to the newly built compiler to generate code for its default target. */ It comes from that cpuid instruction will clobber the ebx register but ebx is also used for the PIC register.
