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 9FC703858D39; Wed, 29 Dec 2021 03:53:58 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 9FC703858D39
From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/103855] Missed optimization: 64bit division
 used instead of 32bit division
Date: Wed, 29 Dec 2021 03:53:58 +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-Version: 12.0
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: 
Message-ID: <bug-103855-4-aLJoJftzNq@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-103855-4@http.gcc.gnu.org/bugzilla/>
References: <bug-103855-4@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: Wed, 29 Dec 2021 03:53:58 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103855

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---

unsigned int optimized(unsigned int a, unsigned int b) {
    return (unsigned long long)a / b;
}

unsigned int unoptimized(unsigned int a, unsigned int b) {
    unsigned long long all =3D a;
    return all / b;
}

unsigned long long unoptimized1(unsigned int a, unsigned int b) {
    unsigned long long all =3D a;
    return all / b;
}

unsigned long long unoptimized2(unsigned long a, unsigned long b) {
    if (((unsigned int)a) !=3D a) __builtin_unreachable();
    if (((unsigned int)b) !=3D b) __builtin_unreachable();
    return a / b;
}

Is the full testcase, clang is able to handle all of them.  GCC only handles
the first one. If you just do the match.pd patch, unoptimized2 would be not
handled.
expmed.c (expand_divmod) is where the expansion happens from gimple to rtl.=