http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49770
--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-07-18 10:46:28 UTC --- Ok, it's sth I worried about when doing the patch. Namely: /* Make sure to use a valueized reference ... */ if (!ao_ref_init_from_vn_reference (&r, vr1.set, vr1.type, vr1.operands)) ao_ref_init (&r, op); else /* ... but also preserve a full reference tree for advanced TBAA. */ r.ref = op; preserving op as r.ref is playing foul of the aliasing code which assumes that the base in r.ref is the one that corresponds to the r.base, r.offset pair. That is not the case when we valueized &MEM[&b]._M_finish into MEM[D.1719_29]._M_cur. Not doing the above loses some TBAA related disambiguations. I'm thinking about a good solution.