From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-patches-return-294160-listarch-gcc-patches=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 14656 invoked by alias); 10 Jun 2011 14:20:42 -0000
Received: (qmail 14644 invoked by uid 22791); 10 Jun 2011 14:20:40 -0000
X-SWARE-Spam-Status: No, hits=-3.3 required=5.0	tests=AWL,BAYES_00,T_RP_MATCHES_RCVD
X-Spam-Check-By: sourceware.org
Received: from cantor2.suse.de (HELO mx2.suse.de) (195.135.220.15)    by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Fri, 10 Jun 2011 14:20:25 +0000
Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.221.2])	by mx2.suse.de (Postfix) with ESMTP id D3F998738D;	Fri, 10 Jun 2011 16:20:23 +0200 (CEST)
Date: Fri, 10 Jun 2011 14:34:00 -0000
From: Richard Guenther <rguenther@suse.de>
To: Jason Merrill <jason@redhat.com>
Cc: Richard Guenther <richard.guenther@gmail.com>,	gcc-patches List <gcc-patches@gcc.gnu.org>
Subject: Re: RFA (fold): PATCH for c++/49290 (folding *(T*)(ar+10))
In-Reply-To: <4DF22656.9050700@redhat.com>
Message-ID: <alpine.LNX.2.00.1106101619070.810@zhemvz.fhfr.qr>
References: <4DEDB98F.6010508@redhat.com> <BANLkTimU_JPKgaqvhtb+m7fbDyTL340YJQ@mail.gmail.com> <4DEE2DCF.7020905@redhat.com> <BANLkTi=FX60RhEj2QF=t9MvkUCHR=D1m1A@mail.gmail.com> <4DEE3484.8030101@redhat.com> <4DF11FBC.3010304@redhat.com> <alpine.LNX.2.00.1106101029320.810@zhemvz.fhfr.qr> <4DF223D4.3080700@redhat.com> <alpine.LNX.2.00.1106101602530.810@zhemvz.fhfr.qr> <4DF22656.9050700@redhat.com>
User-Agent: Alpine 2.00 (LNX 1167 2008-08-23)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-patches.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-patches/>
List-Post: <mailto:gcc-patches@gcc.gnu.org>
List-Help: <mailto:gcc-patches-help@gcc.gnu.org>
Sender: gcc-patches-owner@gcc.gnu.org
X-SW-Source: 2011-06/txt/msg00845.txt.bz2

On Fri, 10 Jun 2011, Jason Merrill wrote:

> On 06/10/2011 10:03 AM, Richard Guenther wrote:
> > > > *((volatile int *)&a[0] + 1)
> > > 
> > > It would be correct to fold it to
> > > 
> > > VIEW_CONVERT_EXPR<volatile int,a[1]>
> > 
> > No, it wouldn't be correct.  It isn't correct to fold it to an array-ref
> > that isn't volatile.
> 
> Hmm?  The C expression produces a volatile int lvalue referring to the second
> element of a, as does the VIEW_CONVERT_EXPR.  They seem equivalent to me.

no, a VIEW_CONVERT_EXPR is generally not an lvalue (fold for example
would turn the above to (volatile int) a[1]).

Richard.