From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-395295-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 23761 invoked by alias); 29 Jun 2012 09:57:31 -0000
Received: (qmail 23751 invoked by uid 22791); 29 Jun 2012 09:57:31 -0000
X-SWARE-Spam-Status: No, hits=-4.3 required=5.0	tests=ALL_TRUSTED,AWL,BAYES_00,KHOP_THREADED
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; Fri, 29 Jun 2012 09:57:18 +0000
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/53802] Spurious 'may be used uninitialized' related to shifts
Date: Fri, 29 Jun 2012 09:57:00 -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: diagnostic
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rguenth at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Changed-Fields: Keywords Status Last reconfirmed Ever Confirmed
Message-ID: <bug-53802-4-oATH2Tlmmy@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-53802-4@http.gcc.gnu.org/bugzilla/>
References: <bug-53802-4@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: 2012-06/txt/msg01922.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53802

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-06-29
     Ever Confirmed|0                           |1

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-06-29 09:57:17 UTC ---
Confirmed.  Reason is a missed "jump-threading" (peeling off one iteration):

<bb 2>:

<bb 3>:
  # number_59 = PHI <number_7(6), 4294967295(2)>
  # buf$2_60 = PHI <buf$2_44(6), buf$2_51(D)(2)>
  # buf$3_61 = PHI <buf$3_2(6), buf$3_52(D)(2)>
  # buf$4_64 = PHI <buf$4_6(6), buf$4_53(D)(2)>
  # buf$1_65 = PHI <buf$1_46(6), buf$1_50(D)(2)>
  if (number_59 == 0)
    goto <bb 5>;
  else
    goto <bb 4>;

<bb 4>:
  D.2247_18 = number_59 >> 24;
  buf$1_19 = (unsigned char) D.2247_18;
  D.2245_20 = number_59 >> 16;
  buf$2_21 = (unsigned char) D.2245_20;
  D.2243_22 = number_59 >> 8;
  buf$3_23 = (unsigned char) D.2243_22;
  buf$4_24 = (unsigned char) number_59;

<bb 5>:
  # buf$1_46 = PHI <buf$1_19(4), buf$1_65(3)>
  # buf$2_44 = PHI <buf$2_21(4), buf$2_60(3)>
  # buf$3_2 = PHI <buf$3_23(4), buf$3_61(3)>
  # buf$4_6 = PHI <buf$4_24(4), buf$4_64(3)>
  D.2257_29 = (unsigned int) buf$1_46;

so we decide there is a path from entry to BB 5 where buf$1_46 is not
initialized.