https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81907
--- Comment #14 from Richard Earnshaw <rearnsha at gcc dot gnu.org> --- (In reply to dongkyun.s from comment #13) > > Confirmed the call on 6.4.1 but GCC 7 and trunk don't generate the call for > > -mcpu=cortex-a9 . > > I also verified memset call is not generated with GCC 7.1 + "-mcpu=cortex-a9 > or -mtune=cortex-a9" or lower. > > It seems interesting that > in GCC6, > - don't generate the memset call for -mcpu=cortex-a12 or higer(e.g, > cortex-a15, V7 big.LITTLE) > - always generate the memset call for -mcpu=cortex-a9 or lower(e.g, > cortex-a7, cotex-a5) > > in GCC7.1 > - always don't generate the memset call (even with V3 Architecture > Processors. e.g, -mcpu=arm7) There's nothing in the compiler that explicitly says: use memset for these cores and not for others. The choice will be down to available instructions and their relative costs.
