From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-379474-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 27016 invoked by alias); 11 Jan 2012 08:58:05 -0000
Received: (qmail 27005 invoked by uid 22791); 11 Jan 2012 08:58:04 -0000
X-SWARE-Spam-Status: No, hits=-2.9 required=5.0	tests=ALL_TRUSTED,AWL,BAYES_00
X-Spam-Check-By: sourceware.org
Received: from localhost (HELO gcc.gnu.org) (127.0.0.1)    by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 11 Jan 2012 08:57:51 +0000
From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/50176] [4.7 Regression] 4.7 generates spill-fill dealing with char->int conversion
Date: Wed, 11 Jan 2012 08:58:00 -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-Keywords: missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rguenther at suse dot de
X-Bugzilla-Status: NEW
X-Bugzilla-Priority: P1
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 4.7.0
X-Bugzilla-Changed-Fields:
Message-ID: <bug-50176-4-mXtqK2J6gk@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-50176-4@http.gcc.gnu.org/bugzilla/>
References: <bug-50176-4@http.gcc.gnu.org/bugzilla/>
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
Content-Type: text/plain; charset="UTF-8"
MIME-Version: 1.0
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
X-SW-Source: 2012-01/txt/msg01149.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50176

--- Comment #12 from rguenther at suse dot de <rguenther at suse dot de> 2012-01-11 08:56:27 UTC ---
On Tue, 10 Jan 2012, ebotcazou at gcc dot gnu.org wrote:

> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50176
> 
> Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:
> 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>                  CC|                            |ebotcazou at gcc dot
>                    |                            |gnu.org
> 
> --- Comment #11 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2012-01-10 22:03:43 UTC ---
> > thus there is a store between the load and the zero_extend (and combine
> > only combines forward, not backward):
> > 
> >   /* Verify that I2 and I1 are valid for combining.  */
> >   if (! can_combine_p (i2, i3, i0, i1, NULL_RTX, NULL_RTX, &i2dest, &i2src)
> > 
> > already fails.
> 
> combine is a peephole optimizer so you cannot ask it to combine insns with 8
> other intervening insns between them.  It looks like we have a real problem
> with extensions though and the good approach (backward combining) appears to be
> that of the REE pass, but it's too limited for the time being.

Yeah, it's a bit unfortunate that combines behavior depends on the
insn scheduling ...