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 E24B4385802D; Wed,  6 Oct 2021 07:23:25 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org E24B4385802D
From: "aldyh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/102622] [12 Regression] Wrong code with -O3
 for skylake-avx512 and icelake-server by r12-3903
Date: Wed, 06 Oct 2021 07:23:25 +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: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 12.0
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: cc
Message-ID: <bug-102622-4-8DCBURYEw9@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-102622-4@http.gcc.gnu.org/bugzilla/>
References: <bug-102622-4@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: Wed, 06 Oct 2021 07:23:26 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102622

Aldy Hernandez <aldyh at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |aldyh at gcc dot gnu.org

--- Comment #4 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #3)
> (In reply to Andrew Pinski from comment #2)
> > Here is a slightly more reduced testcase (without the reasonable values=
):
>=20
> Looks like the store to var_22 was fully removed, I think this is not a
> vectorizer bug really, but rather some issue with jump threading ....

I'm getting an illegal instruction, so perhaps I don't have a machine with =
the
appropriate hardware.  I even get the illegal instruction with
-fno-thread-jumps:

(base) abulafia:~/bld/t/gcc$ ./xg++ -B./ a.c -O3
-L/usr/lib/gcc/x86_64-redhat-linux/11/ -march=3Dskylake-avx512=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20
                   (base) abulafia:~/bld/t/gcc$ ./a.out
Illegal instruction (core dumped)

Can you try with -fno-thread-jumps to make sure its really the threader at
play?

If so, you could try to narrow it down to the problematic threading path wi=
th:

-fdbg-cnt=3Dregistered_jump_thread:N:N

where N is the number that causes the problem.

Once it's narrowed, I could look at the path and see if it's valid.

Thanks.=