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From: "tnfchris at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/114234] [14 Regression] verify_ssa failure
 with early-break vectorisation
Date: Tue, 05 Mar 2024 14:23:00 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114234

Tamar Christina <tnfchris at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-03-05
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #3 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
started with

commit g:324d2907c86f05e40dc52d226940308f53a956c2
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Mar 4 09:46:13 2024 +0100

    tree-optimization/114192 - scalar reduction kept live with early break =
vect

    The following fixes a missing replacement of the reduction value
    used in the epilog, causing the scalar reduction to be kept live
    across the early break exit path.

            PR tree-optimization/114192
            * tree-vect-loop.cc (vect_create_epilog_for_reduction): Use the
            appropriate def for the live out stmt in case of an alternate
            exit.

the reduction seems to propagate out a single value for both exits:

  # a_39 =3D PHI <stmp_a_9.10_95(10), stmp_a_9.10_95(15)>

but since the PHI nodes carry their reduction values in the exits we have
different reduction statements, so using the same reduction value for all e=
xit
is wrong.

should be

  # a_39 =3D PHI <stmp_a_9.10_89(10), stmp_a_9.10_95(15)>=