https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108583
--- Comment #4 from rguenther at suse dot de <rguenther at suse dot de> --- On Mon, 30 Jan 2023, tnfchris at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108583 > > Tamar Christina <tnfchris at gcc dot gnu.org> changed: > > What |Removed |Added > ---------------------------------------------------------------------------- > CC| |rguenth at gcc dot gnu.org, > | |rsandifo at gcc dot gnu.org > > --- Comment #3 from Tamar Christina <tnfchris at gcc dot gnu.org> --- > Right, so this is because in the expansion we don't have enough context to > decide how to optimize the division. > > This optimization is only possible when the input is widened because you need > an additional free bit so that the second addition can't overflow. > > The vectorizer has this context but since we didn't want a new IFN the > context should instead be derivable in > targetm.vectorize.can_special_div_by_const hook. The vectorizer doesn't check for a widened operand zero. In fact "can_special_div_by_const" doesn't suggest that widening is required. If the vectorizer checks that then why do we need another operand?
