https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66917
Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |rguenth at gcc dot gnu.org --- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> --- Probably because you access a.u/b.u which is uint64_t and thus the union is laid out as having 8 byte alignment? How do the original GENERIC trees produced look like?