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 9C9983858280; Tue,  5 Jul 2022 16:57:25 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 9C9983858280
From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/96692] Failure to optimize xor+or+xor to
 andnot+xor
Date: Tue, 05 Jul 2022 16:57:25 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: rtl-optimization
X-Bugzilla-Version: 11.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: cvs-commit 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: 
Message-ID: <bug-96692-4-SdORk519F7@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-96692-4@http.gcc.gnu.org/bugzilla/>
References: <bug-96692-4@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: Tue, 05 Jul 2022 16:57:25 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D96692

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Roger Sayle <sayle@gcc.gnu.org>:

https://gcc.gnu.org/g:d458c53a6f37c8c49aa854d12e6867b4d914555f

commit r13-1507-gd458c53a6f37c8c49aa854d12e6867b4d914555f
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Tue Jul 5 17:55:53 2022 +0100

    PR rtl-optimization/96692: ((A|B)^C)^A using andn with -mbmi on x86.

    This patch addresses PR rtl-optimization/96692 on x86_64, by providing
    a set of combine splitters to convert the three operation ((A|B)^C)^D
    into a two operation sequence using andn when either A or B is the same
    register as C or D.  This is essentially a reassociation problem that's
    only a win if the target supports an and-not instruction (as with -mbmi=
).

    Hence for the new test case:

    int f(int a, int b, int c)
    {
        return (a ^ b) ^ (a | c);
    }

    GCC on x86_64-pc-linux-gnu wth -O2 -mbmi would previously generate:

            xorl    %edi, %esi
            orl     %edx, %edi
            movl    %esi, %eax
            xorl    %edi, %eax
            ret

    but with this patch now generates:

            andn    %edx, %edi, %eax
            xorl    %esi, %eax
            ret

    2022-07-05  Roger Sayle  <roger@nextmovesoftware.com>
                Uro=C3=85=C2=A1 Bizjak  <ubizjak@gmail.com>

    gcc/ChangeLog
            PR rtl-optimization/96692
            * config/i386/i386.md (define_split): Split ((A | B) ^ C) ^ D
            as (X & ~Y) ^ Z on target BMI when either C or D is A or B.

    gcc/testsuite/ChangeLog
            PR rtl-optimization/96692
            * gcc.target/i386/bmi-andn-4.c: New test case.=