From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
 id 9D91B38515F2; Mon, 26 Jul 2021 19:18:39 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 9D91B38515F2
From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/26656] Optimization flaw on conditional set of a bit.
Date: Mon, 26 Jul 2021 19:18:39 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Version: 3.4.5
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: pinskia at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: component cf_gcctarget
Message-ID: <bug-26656-4-W1fVuuqJgR@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-26656-4@http.gcc.gnu.org/bugzilla/>
References: <bug-26656-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Mon, 26 Jul 2021 19:18:39 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D26656

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|tree-optimization           |target
             Target|                            |x86_64

--- Comment #9 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
flagQuestion:
.L2:
        cmpb    %bpl, (%r12,%rax)
        setb    %cl
        addl    %ecx, %ecx
        orb     %cl, (%rbx,%rax)
        addq    $1, %rax
        cmpq    $100000000, %rax
        jne     .L2
flagQuestionWorkaround:
.L7:
        cmpb    %bpl, (%r12,%rax)
        setb    %cl
        addl    %ecx, %ecx
        orb     %cl, (%rbx,%rax)
        addq    $1, %rax
        cmpq    $100000000, %rax
        jne     .L7
flagIf:
.L12:
        cmpb    %bl, (%r12,%rax)
        jnb     .L11
        orb     $2, 0(%rbp,%rax)
.L11:
        addq    $1, %rax
        cmpq    $100000000, %rax
        jne     .L12
flagIfWorkaround:
.L16:
        cmpb    %bpl, (%r12,%rax)
        setb    %cl
        addl    %ecx, %ecx
        orb     %cl, (%rbx,%rax)
        addq    $1, %rax
        cmpq    $100000000, %rax
        jne     .L16

There is not much be done with flagIf really since it is a conditional
load/store.=