LV is careful to respect -Os and not to create a scalar epilog in all cases (runtime tests, trip-counts that require a remainder loop) except for peeling due to gaps in interleave-groups. This patch fixes that; -Os will now have us invalidate such interleave-groups and vectorize without an epilog.
(Heads up: an upcoming patch will allow us to vectorize such interleave-group-with-gaps using masking instead of peeling, so we won't have to invalidate such groups for targets that support masked interleaving).
The patch also removes a related FIXME comment that is now obsolete, and was also inaccurate :
"FIXME: return None if loop requiresScalarEpilog(<MaxVF>), or look for a smaller MaxVF that does not require a scalar epilog."
(requiresScalarEpilog() has nothing to do with VF).