http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49330
--- Comment #7 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2011-06-10 09:50:28 UTC --- The alias.c machinery is clearly based on the fundamental assumption of pointer arithmetics, i.e. that you aren't allowed to compute a difference unless both pointers point to the same enclosing object. The testcase is a nice attempt at smuggling the violation of this rule behind a uintptr_t based manipulation. Not clear what to do IMO. Richard is proposing to leverage the escape sites: px_1 = (uintptr_t) &x; py_2 = (uintptr_t) &y; but this will pessimize. Ideally we should leverage the one problematic line: p.2_6 = (int *) p_5; which creates the pointer out of the integer, but it has already disappeared in the very first RTL representation.