http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56564
--- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-03-08 12:38:20 UTC --- Smaller testcase (-O2 -fpic): struct S { long a, b; } s; int foo (void) { return ((long) &s) & 15; } is since http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=162943 optimized into return 0, even when (probably) the psABI doesn't guarantee that. But e.g. for __builtin_memset (&s, 0, sizeof (s)); one can see already in 4.0 RTL dumps with -O2 -fpic that MEM_ALIGN of s is assumed to be 128-bit.