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 CA260385626B; Fri, 24 Jun 2022 18:07:35 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org CA260385626B
From: "segher at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/94026] combine missed opportunity to simplify
 comparisons with zero
Date: Fri, 24 Jun 2022 18:07:35 +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: 10.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: segher 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-94026-4-Xq2jwhhhhf@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-94026-4@http.gcc.gnu.org/bugzilla/>
References: <bug-94026-4@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: Fri, 24 Jun 2022 18:07:35 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94026

--- Comment #10 from Segher Boessenkool <segher at gcc dot gnu.org> ---
So on Arm we get

Trying 6 -> 8:
    6: r119:SI=3Dr123:SI>>0x8
      REG_DEAD r123:SI
    8: {cc:CC_NZ=3Dcmp(r119:SI&0x6,0);clobber scratch;}
      REG_DEAD r119:SI
Failed to match this instruction:
(parallel [
        (set (reg:CC_NZ 100 cc)
            (compare:CC_NZ (and:SI (lshiftrt:SI (reg:SI 123)
                        (const_int 8 [0x8]))
                    (const_int 6 [0x6]))
                (const_int 0 [0])))
        (clobber (scratch:SI))
    ])
Failed to match this instruction:
(set (reg:CC_NZ 100 cc)
    (compare:CC_NZ (and:SI (lshiftrt:SI (reg:SI 123)
                (const_int 8 [0x8]))
            (const_int 6 [0x6]))
        (const_int 0 [0])))

instead of something like

(set (reg:CC_NZ 100 cc)
     (compare:CC_NZ (and:SI (reg:SI 123)
                            (const_int 1536))
                    (const_int 0)))

which is correct for every CC mode even, not just NZ?=