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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/111683] [11/12/13/14 Regression] Incorrect answer
 when using SSE2 intrinsics with -O3 since
 r7-3163-g973625a04b3d9351f2485e37f7d3382af2aed87e
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111683

--- Comment #25 from rguenther at suse dot de <rguenther at suse dot de> ---
On Fri, 22 Mar 2024, jakub at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111683
>=20
> --- Comment #24 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
> (In reply to Richard Biener from comment #23)
> > It looks like this could go to suitable_reference_p instead?
>=20
> You mean return false for those making them not suitable at all?
> I thought without a write such references would act more like RS_ANY, but
> a reason I didn't just treat such references as RS_ANY rather than RS_NON=
ZERO
> in suitable_reference_p was because of the assert that all refs in a comp=
onent
> have the same ref_step_type but nothing actually comparing it before the
> assertion.

Hmm, true.

> But if you think I should just return false from suitable_reference_p if =
the
> step isn't a multiple of the sizes, I can surely try that.
>=20
> > That said, I do wonder why with my patch split_data_refs_to_components
> > doesn't fixup.  I think it's supposed to handle the case where
> > dependences are unknown conservatively...
>=20
> I'm afraid I'm not familiar with data refs enough to know what was going =
on.

I tried to follow what happens there and I'm also somewhat lost.

Anyway, I think fixing this in predcom in a convenient place even if
it might be not the true fix is OK.  You might want to put a comment
before any such fix indicating there might be more latent issues
in predcom or dependence analysis in general.=