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From: "tnfchris 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: Mon, 12 Feb 2024 13:33:30 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113734

--- Comment #22 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #21)
> loop->nb_iterations_upper_bound exactly is an upper bound on the number of
> latch executions, so maybe I'm missing the point here.  When we update it=
 it
> as
> well has to reflect an upper bound on that, whether the last exit (the one
> before the latch) is the IV exit or a vectorized early exit.

Yes, but the issue here is that the bounds limit is coming from an exit oth=
er
than the one being chosen as the IV exit.

So the latch iterates X times not X - 1.

>=20
> But yes, if the last exit is an early one that last iteration might be
> partial
> (so we drop the -1), but that's what we already do?

I don't see where.  This code all seems to remove -1 from the iteration cou=
nt
and assuming the latch iteration count + 1 =3D=3D nbounds.

I don't really think this is about partial loops at all.

Change

    parse_tables_n >>=3D 9;
    parse_tables_n +=3D 11;

to

    parse_tables_n >>=3D 9;
    parse_tables_n +=3D 10;

then loop->nb_iterations_upper_bound is 136 and there is no partial iterati=
ons
here.

You do 17 full vector iterations with no residuals.=