From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-407386-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 5678 invoked by alias); 21 Nov 2012 14:42:53 -0000
Received: (qmail 3927 invoked by uid 48); 21 Nov 2012 14:42:14 -0000
From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/54471] [4.8 Regression] FAIL: gcc.dg/sms-8.c execution test
Date: Wed, 21 Nov 2012 14:42:00 -0000
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: jakub at gcc dot gnu.org
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: jakub at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 4.8.0
X-Bugzilla-Changed-Fields: Status AssignedTo
Message-ID: <bug-54471-4-AdNCDdh6LH@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-54471-4@http.gcc.gnu.org/bugzilla/>
References: <bug-54471-4@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: 2012-11/txt/msg02048.txt.bz2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54471

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |jakub at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-11-21 14:42:13 UTC ---
Created attachment 28755
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28755
gcc48-pr54471.patch

Untested fix.  I believe the bug is in invalid canonicalization.  When
sizem1 is { -1, -1 } double_int, sizem1 + double_int_one is { 0, 0 }, as it
wrapped, instead of { 0, 0, 1, 0 } quad_int.  And if min0 or min1 is zero, then
size - min{0,1} is also zero, and so is very likely smaller than max{0,1}
(unless min{0,1} == max{0,1}), but we still don't want to "canonicalize" that
to signed.  IMHO testing min2.is_zero () is sufficient, as min0 or min1 should
be a valid double_int in the range 0 to { -1, -1 }, which is always smaller
than the maximum unsigned integer + 1 in infinite precision and thus min2
should never be zero, unless size overflowed to 0 and min{0,1} is zero.