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 100E13858D28; Fri, 12 Nov 2021 10:18:40 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 100E13858D28
From: "aldyh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/103202] [12 regression] gcc miscompiles
 ed-1.17 since r12-3876-g4a960d548b7d7d94
Date: Fri, 12 Nov 2021 10:18:40 +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: 12.0
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: aldyh at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P1
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 12.0
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-103202-4-V5dK5HjG4U@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-103202-4@http.gcc.gnu.org/bugzilla/>
References: <bug-103202-4@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, 12 Nov 2021 10:18:40 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103202

--- Comment #6 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
Not looking at this yet, but disabling jump threading from all passes (dom
included) makes the problem go away:

$ ./xgcc -B./ a.c -w -O2 -fno-thread-jumps && ./a.out
element 1
element 2
element 3

...so *maybe* threading related.

The minimum number of threads that reproduces this is:

 ./xgcc -B./ a.c -w -O2 -fdbg-cnt=3Dregistered_jump_thread:1-1:3-3:5-5  &&
./a.out
***dbgcnt: lower limit 1 reached for registered_jump_thread.***
***dbgcnt: upper limit 1 reached for registered_jump_thread.***
***dbgcnt: lower limit 3 reached for registered_jump_thread.***
***dbgcnt: upper limit 3 reached for registered_jump_thread.***
***dbgcnt: lower limit 5 reached for registered_jump_thread.***
***dbgcnt: upper limit 5 reached for registered_jump_thread.***
element 1
element 2
$ grep 'Register.*jump' a.c.*
a.c.111t.threadfull1:  [1] Registering jump thread: (6, 7) incoming edge;  =
(7,
9) nocopy;=20
a.c.126t.thread1:  [3] Registering jump thread: (2, 4) incoming edge;  (4, =
12)
nocopy;=20
a.c.191t.thread2:  [5] Registering jump thread: (13, 11) incoming edge;  (1=
1,
10) nocopy;=