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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/113734] [14 regression] libarchive miscompiled
 (fails libarchive_test_read_format_rar5_extra_field_version test) since
 r14-8768-g85094e2aa6dba7
Date: Thu, 08 Feb 2024 11:59:18 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113734

--- Comment #11 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Tamar Christina from comment #10)
> (In reply to Richard Biener from comment #9)
> > Another bug in the dependence checking code is
> >=20
> >                 if (dr_may_alias_p (dr_ref, dr_read, loop_nest))
> >=20
> > which will end up using TBAA - dr_may_alias_p doesn't think you are ever
> > going to move stores down across loads.  To verify if that's possible
> > you need to use
> >=20
> >                 if (dr_may_alias_p (dr_read, dr_ref, loop_nest))
> >=20
> > instead.
> >=20
> > Note there's still my very original review consideration that you move
> > stmts out-of-order but the main dependence checking the vectorizer does
> > assumes the stores and loads appear in their original order.  I'm not
> > sure whether with the above we prove this doesn't matter.
>=20
> But in the original review I had it that way and you said:
>=20
> > +		  for (auto dr_read : bases)
> > +		    if (dr_may_alias_p (dr_read, dr_ref, loop_nest))
>=20
> I think you need to swap dr_read and dr_ref operands, since you
> are walking stmts backwards and thus all reads from 'bases' are
> after the write.
>=20
> so I'm somewhat confused..

I was confused.=