From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
 id 08D023858406; Mon, 25 Apr 2022 07:52:43 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 08D023858406
From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/100810] [12 Regression] wrong code at -O1 and above
 on x86_64-linux-gnu since r12-397-gda9e6e63d1ae22e530ec7baf59f6ed028bf05776
Date: Mon, 25 Apr 2022 07:52:43 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: middle-end
X-Bugzilla-Version: 12.0
X-Bugzilla-Keywords: patch, wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: cvs-commit at gcc dot gnu.org
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P1
X-Bugzilla-Assigned-To: rguenth at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 12.0
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-100810-4-tR1YiogsoL@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-100810-4@http.gcc.gnu.org/bugzilla/>
References: <bug-100810-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Mon, 25 Apr 2022 07:52:44 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100810

--- Comment #14 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:ab91c10792cd3a1ba1495aa30a34ca17b043bafb

commit r12-8241-gab91c10792cd3a1ba1495aa30a34ca17b043bafb
Author: Richard Biener <rguenther@suse.de>
Date:   Fri Apr 1 11:30:00 2022 +0200

    tree-optimization/100810 - avoid undefs in IVOPT rewrites

    The following attempts to avoid IVOPTs rewriting uses using
    IV candidates that involve undefined behavior by using uninitialized
    SSA names.  First we restrict the set of candidates we produce
    for such IVs to the original ones and mark them as not important.
    Second we try to only allow expressing uses with such IV if they
    originally use them.  That is to avoid rewriting all such uses
    in terms of other IVs.  Since cand->iv and use->iv seem to never
    exactly match up we resort to comparing the IV bases.

    The approach ends up similar to the one posted by Roger at
    https://gcc.gnu.org/pipermail/gcc-patches/2021-August/578441.html
    but it marks IV candidates rather than use groups and the cases
    we allow in determine_group_iv_cost_generic are slightly different.

    2022-01-04  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/100810
            * tree-ssa-loop-ivopts.cc (struct iv_cand): Add involves_undefs
flag.
            (find_ssa_undef): New function.
            (add_candidate_1): Avoid adding derived candidates with
            undefined SSA names and mark the original ones.
            (determine_group_iv_cost_generic): Reject rewriting
            uses with a different IV when that involves undefined SSA names.

            * gcc.dg/torture/pr100810.c: New testcase.
            * gcc.dg/torture/pr105337.c: Likewise.=