https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106680
--- Comment #9 from Kewen Lin <linkw at gcc dot gnu.org> --- Note that now we only disable implicit powerpc64 for -m32 when the OS_MISSING_POWERPC64 is set. /* Don't expect powerpc64 enabled on those OSes with OS_MISSING_POWERPC64, since they do not save and restore the high half of the GPRs correctly in all cases. If the user explicitly specifies it, we won't interfere with the user's specification. */ #ifdef OS_MISSING_POWERPC64 if (OS_MISSING_POWERPC64 && TARGET_32BIT && TARGET_POWERPC64 && !(rs6000_isa_flags_explicit & OPTION_MASK_POWERPC64)) rs6000_isa_flags &= ~OPTION_MASK_POWERPC64; #endif But rtems.h doesn't define OS_MISSING_POWERPC64 gcc/config/rs6000/linux.h:#define OS_MISSING_POWERPC64 1 gcc/config/rs6000/freebsd64.h:#define OS_MISSING_POWERPC64 !TARGET_64BIT gcc/config/rs6000/aix.h:#define OS_MISSING_POWERPC64 1 gcc/config/rs6000/linux64.h:#define OS_MISSING_POWERPC64 !TARGET_64BIT meanwhile cpu "e6500" has MASK_POWERPC64 set by default (it's 64bit core). That's why you still have powerpc64 flag set when you specify -m32 on rtems.