From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-355904-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 13554 invoked by alias); 6 May 2011 13:21:21 -0000
Received: (qmail 13545 invoked by uid 22791); 6 May 2011 13:21:21 -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; Fri, 06 May 2011 13:21:07 +0000
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/15596] [4.3/4.4/4.5/4.6/4.7 Regression] Missed optimization with bitfields with return value
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: missed-optimization
X-Bugzilla-Severity: minor
X-Bugzilla-Who: rguenth at gcc dot gnu.org
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Priority: P5
X-Bugzilla-Assigned-To: rguenth at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 4.3.6
X-Bugzilla-Changed-Fields: Status AssignedTo
Message-ID: <bug-15596-4-mwpQ4MX0pi@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-15596-4@http.gcc.gnu.org/bugzilla/>
References: <bug-15596-4@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: Fri, 06 May 2011 13:21:00 -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: 2011-05/txt/msg00571.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15596

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |ASSIGNED
         AssignedTo|unassigned at gcc dot       |rguenth at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #19 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-05-06 13:18:31 UTC ---
Even with bitfield accesses lowered at the tree level we end up with

<bb 2>:
  D.1736_2 = (<unnamed-signed:20>) s_1(D);
  BF.0_3 = MEM[(struct bitstr *)&<retval>];
  D.1741_4 = BF.0_3 & -1048576;
  D.1742_5 = (<unnamed-unsigned:20>) D.1736_2;
  D.1743_6 = (int) D.1742_5;
  BF.0_7 = D.1741_4 | 1048576;
  BF.1_9 = BF.0_7 | D.1743_6;
  D.1737_13 = (signed char) l_12(D);
  D.1738_14 = (<unnamed-signed:1>) D.1737_13;
  D.1747_16 = BF.1_9 & -6291457;
  D.1748_17 = (<unnamed-unsigned:1>) D.1738_14;
  D.1749_18 = (int) D.1748_17;
  D.1750_19 = D.1749_18 << 22;
  BF.3_20 = D.1750_19 | D.1747_16;
  MEM[(struct bitstr *)&<retval>] = BF.3_20;
  return <retval>;

there's some optimization possibilities if we can recognize the truncating
and extending conversions as bit manipulations.