From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-245966-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 28507 invoked by alias); 25 Feb 2008 05:39:38 -0000
Received: (qmail 16096 invoked by uid 48); 25 Feb 2008 05:38:52 -0000
Date: Mon, 25 Feb 2008 05:39:00 -0000
Subject: [Bug middle-end/35363]  New: Missing bit field coalscing optimization
X-Bugzilla-Reason: CC
Message-ID: <bug-35363-9436@http.gcc.gnu.org/bugzilla/>
Reply-To: gcc-bugzilla@gcc.gnu.org
To: gcc-bugs@gcc.gnu.org
From: "xinliangli at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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: 2008-02/txt/msg02620.txt.bz2

// David Li

struct A{
  int b1: 3;
  int b2: 3;
  int b3: 2;
  int b4: 17;
}a;
void foo()
{
    a.b1 = 2;
    a.b2 = 3;
    a.b4 = 8;
}

This requires one LOAD + one OR + one STORE, but the generate code looks like:

foo:
.LFB2:
        movzbl  a(%rip), %eax
        andl    $-64, %eax
        orl     $26, %eax
        movb    %al, a(%rip)
        movl    a(%rip), %eax
        andl    $-33554177, %eax
        orb     $8, %ah
        movl    %eax, a(%rip)
        ret


-- 
           Summary: Missing bit field coalscing optimization
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: xinliangli at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35363