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 602E53858422; Tue,  2 Nov 2021 08:10:57 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 602E53858422
From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/103006] [9/10/11/12 Regression] wrong code at
 -O1 or -O2 on x86_64-linux-gnu by r7-7101
Date: Tue, 02 Nov 2021 08:10:57 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: rtl-optimization
X-Bugzilla-Version: 12.0
X-Bugzilla-Keywords: ra, wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rguenther at suse dot de
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: 9.5
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-103006-4-Ny9obsO77K@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-103006-4@http.gcc.gnu.org/bugzilla/>
References: <bug-103006-4@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: Tue, 02 Nov 2021 08:10:57 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103006

--- Comment #8 from rguenther at suse dot de <rguenther at suse dot de> ---
On Tue, 2 Nov 2021, jakub at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103006
>=20
> --- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
> Looks like that.
> What do you think about unrolling making variable copies?  We'd need to b=
e sure
> that the scope of the variable is the loop we are unrolling though (or
> something nested in it).

Being able to determine that would solve the very issue we're trying
to fix with making the copy.  The problem is that we put in CLOBBERs
based on the original BINDs but later optimizers do not respect the
birth boundary.  If we can figure that out we could ignore the
respective CLOBBERs for the CFG expansion live compute as well.

I think we may be able to compute the CFG SCC a CLOBBER resides in
and in case the CLOBBERed variable is live-in into that SCC we cannot
prune it with that CLOBBER.  Or so.=