From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-347026-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 23423 invoked by alias); 12 Feb 2011 06:36:21 -0000
Received: (qmail 23320 invoked by uid 22791); 12 Feb 2011 06:36:20 -0000
X-SWARE-Spam-Status: No, hits=-2.7 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; Sat, 12 Feb 2011 06:36:14 +0000
From: "pinskia at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/47708] incorrect code on -O2 without -fno-tree-pre
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: pinskia at gmail dot com
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Changed-Fields:
Message-ID: <bug-47708-4-rzkr0b3J16@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-47708-4@http.gcc.gnu.org/bugzilla/>
References: <bug-47708-4@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
Date: Sat, 12 Feb 2011 07:27:00 -0000
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: 2011-02/txt/msg01492.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47708

--- Comment #1 from pinskia at gmail dot com <pinskia at gmail dot com> 2011-02-12 06:36:09 UTC ---
You are violating c/c++ aliasing rules. &nbsp;The code is undefined.



Sent from my Palm Pre on AT&amp;T
On Feb 11, 2011 22:27, zephyrtronium at gmail dot com
&lt;gcc-bugzilla@gcc.gnu.org&gt; wrote: 

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47708



           Summary: incorrect code on -O2 without -fno-tree-pre

           Product: gcc

           Version: 4.5.2

            Status: UNCONFIRMED

          Severity: normal

          Priority: P3

         Component: tree-optimization

        AssignedTo: unassigned@gcc.gnu.org

        ReportedBy: zephyrtronium@gmail.com





Created attachment 23310

  --&gt; http://gcc.gnu.org/bugzilla/attachment.cgi?id=23310

minimal case



gcc -v

Using built-in specs.

COLLECT_GCC=gcc

COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-unknown-linux-gnu/4.5.2/lto-wrapper

Target: x86_64-unknown-linux-gnu

Configured with: ../gcc-4.5.2/configure --enable-lto

Thread model: posix

gcc version 4.5.2 (GCC)



Compiling the following minimal case on -O2 or -O3 and running results in

incorrect output; with -O0, -O1, or -Os, it is correct. -O2 -fno-tree-pre

results in correct output, but -O1 -ftree-pre is also correct. GCC 4.4.3

appears to work.