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 32398385DC14; Wed, 15 Apr 2020 09:57:01 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 32398385DC14
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
 s=default; t=1586944621;
 bh=839hlHSQM0u1I+HDI82ru6ciSQJntfGInD9Vo984ZwY=;
 h=From:To:Subject:Date:In-Reply-To:References:From;
 b=BBrgdv4ECb+vyDtVzzyxf2h11YbF1wGQGtXDld05RzPAVb76+ZrksWnFGo2LcS49u
 utaSWnoVoAFW5YmQda5ItIqTVf+/Vgmmo5l16MLFg4YRUEheI5SATGBXfraUK8jb0w
 I23ITQViASXgQsUAMwKGKLnrDJVprPjL9R7nLebA=
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/94567] [10 Regression] wrong code at -O2 and -O3 on
 x86_64-linux-gnu
Date: Wed, 15 Apr 2020 09:57:01 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Version: 10.0
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rguenth at gcc dot gnu.org
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P1
X-Bugzilla-Assigned-To: law at redhat dot com
X-Bugzilla-Target-Milestone: 10.0
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-94567-4-I0uSQbFtSu@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-94567-4@http.gcc.gnu.org/bugzilla/>
References: <bug-94567-4@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: <http://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: <http://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Wed, 15 Apr 2020 09:57:01 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94567

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jeffrey A. Law from comment #7)
> I think it's trying to use smaller modes because the encodings can be
> smaller.  In other cases it changes the mode to avoid partial register
> stalls.  It's a bit of a mess.
>=20
> WRT the fragment you mentioned, I looked at that repeatedly trying to
> ascertain the real motivation and whether or not that code needed
> generalization to handle this case or was a misguided attempt to fix anot=
her
> instance of this issue.
>=20
> The conclusion I came to was that hunk of code may well be working around
> another instance of this same problem, but it was neither generalizable to
> this BZ nor would my approach totally fix that instance.
>=20
> We may be able to remove the hack in the testqi_ext_3 pattern, but I think
> the corresponding hack in testdi_1 would have to stay unless we found a w=
ay
> to merge testdi_1 into the more general test<mode>_1 pattern.  Neither of
> those seems terribly appropriate right now.

agreed=