http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499
--- Comment #10 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-12-12 11:24:22 UTC --- Hmm. But we are vectorizing sum += a[i] sum += a[i+1] the same as sum += a[i+1] sum += a[i] no? Thus you have to check whether the summation occours in "memory order"?
