https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81418
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> --- Hrm. So whenever a reducing pattern is exercised in the reduction "chain" we cannot handle regular uses of the PHI as we basically have to force a single_defuse_cycle. So we can't vectorize this case but we fail to reject it.
