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 36C733858023; Fri, 29 Jan 2021 09:36:41 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 36C733858023
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/98868] [8/9/10/11 Regression] polyhedron
 rnflow.f90 regression since r8-2555-g344be1fd47d7d64e
Date: Fri, 29 Jan 2021 09:36:41 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 11.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rguenth at gcc dot gnu.org
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: rguenth at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 8.5
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-98868-4-Tg3prqXD8X@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-98868-4@http.gcc.gnu.org/bugzilla/>
References: <bug-98868-4@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: Fri, 29 Jan 2021 09:36:41 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98868

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
Ah, so I have polyhedron11 and remember patching:

!CRAY - The following multiply must be done with 64 bits (not 46 bits)
!       The algoritm depends on the overflow characteristics of
!       a 32 or 64 bit multiply.
      jsee_long =3D jsee;
      jsee_long =3D jsee_long * jmul + jadd
      jsee =3D jsee_long;

see ~gcctest/spectests/c++bench/pb11/rnflow.patch which IIRC else caused
miscompiles at some point due to undefined overflow.  Might explain why
I can't reproduce the issue.=