https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66665
H.J. Lu <hjl.tools at gmail dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Last reconfirmed| |2015-06-30 Ever confirmed|0 |1 --- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> --- It is caused by the combination of -mregparm=3 -mtune=i686. -mregparm=3 -mtune=generic -O2 gives f: .cfi_startproc movsbl a+1(%eax), %edx movsbl b+1(%eax), %eax addl %edx, %eax ret .cfi_endproc