From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-120009-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 18172 invoked by alias); 28 Nov 2004 01:28:26 -0000
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
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
Received: (qmail 18154 invoked by uid 48); 28 Nov 2004 01:28:23 -0000
Date: Sun, 28 Nov 2004 01:28:00 -0000
Message-ID: <20041128012823.18153.qmail@sourceware.org>
From: "pinskia at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
In-Reply-To: <20041031010322.18241.ak@muc.de>
References: <20041031010322.18241.ak@muc.de>
Reply-To: gcc-bugzilla@gcc.gnu.org
Subject: [Bug tree-optimization/18241] [4.0 Regression] linux kernel loop gets miscompiled
X-Bugzilla-Reason: CC
X-SW-Source: 2004-11/txt/msg03418.txt.bz2
List-Id: <gcc-bugs.sourceware.org>


------- Additional Comments From pinskia at gcc dot gnu dot org  2004-11-28 01:28 -------
Confirmed,  this looks like a jump threading bug.
Before we have:
 goto <bb 9> (<L10>);

<L8>:;
  D.7815_42 = pathp_2->node;
  tag_43 = tag_27;
  idx_44 = idx_6;
  D.7819_45 = D.7815_42->tags[tag_43][idx_44];
  if (D.7819_45 != 0) goto out; else goto <L9>;

<L9>:;
  idx_46 = idx_6 + 1;

  # idx_6 = PHI <idx_39(6), idx_46(8)>;
<L10>:;
  if (idx_6 == 0) goto <L8>; else goto <L11>;


But after:
 goto <bb 8> (<L10>);

<L9>:;
  idx_46 = 1;
  goto <bb 10> (<L15>);

  # idx_57 = PHI <0(6)>;
<L10>:;
  D.7815_42 = pathp_2->node;
  tag_43 = tag_27; 
  idx_44 = 0;   <---- this is just plainly wrong.
  D.7819_45 = D.7815_42->tags[tag_27][0];
  if (D.7819_45 != 0) goto out; else goto <L9>;

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2004-11-28 01:28:23
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18241