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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/108583] [13 Regression] wrong code with vector division
 by uint16 at -O2
Date: Mon, 30 Jan 2023 14:52:55 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108583

--- 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=3D108583
>=20
> Tamar Christina <tnfchris at gcc dot gnu.org> changed:
>=20
>            What    |Removed                     |Added
> -------------------------------------------------------------------------=
---
>                  CC|                            |rguenth at gcc dot gnu.o=
rg,
>                    |                            |rsandifo at gcc dot gnu.=
org
>=20
> --- 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.
>=20
> 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.
>=20
> The vectorizer has this context but since we didn't want a new IFN the=20
> context should instead be derivable in=20
> 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?=