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 988523887001; Tue,  7 Apr 2020 07:30:58 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 988523887001
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
 s=default; t=1586244658;
 bh=S4clrC4/YbDdHkdPBqvK7v65yW7vsupzP5MwaNtUiqc=;
 h=From:To:Subject:Date:In-Reply-To:References:From;
 b=dwUm5wB6SMLBB1Mz80ZnG6IOCmKbV7VXRU1eEMyYPMYhxTTSKsXwaKNLAsN10AKWi
 hu+r7ThQC67g+Gs+iIl3A6jc/tHDkEfy5XKnmRGkzXlpf42LewG3UyTXYp/vpdZE+t
 +SefO2e5qCbIQU0DnZN4S5DVODpy13C/0A08sUPs=
From: "luoxhu at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/61837] missed loop invariant expression optimization
Date: Tue, 07 Apr 2020 07:30:58 +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: 5.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: luoxhu 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: cc
Message-ID: <bug-61837-4-ahR3brQ4QZ@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-61837-4@http.gcc.gnu.org/bugzilla/>
References: <bug-61837-4@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: <http://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: <http://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Tue, 07 Apr 2020 07:30:58 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D61837

luoxhu at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |luoxhu at gcc dot gnu.org

--- Comment #3 from luoxhu at gcc dot gnu.org ---
"addi 8,4,-1" and "subf 9,8,5" could not be hoisted out as there are depend=
ency
to "lbzu 9,1(8)". r8 need be initialized to p2-1 in each iteration of outer
loop. Only the result of subf 9,8,5 is loop invariant (p2+s-1)-(p2-1).

But the latest GCC code could be optimized as A, B, C is loop invariant.

foo:
.LFB0:
        .cfi_startproc
        cmpwi 7,5,0
        li 6,0
        rldicl 5,5,0,32
        li 7,0
        .p2align 4,,15
.L2:
        ble 7,.L7
        addi 8,5,-1       // A
        addi 10,4,-1
        rldicl 8,8,0,32   // B
        mr 9,3
        addi 8,8,1        // C
        mtctr 8
        .p2align 5
.L4:
        lbzu 8,1(10)
        cmpw 0,8,7
        bne 0,.L3
        stw 6,0(9)
.L3:
        addi 9,9,4
        bdnz .L4
.L7:
        addi 6,6,88
        addi 7,7,1
        cmpwi 0,6,8888
        extsw 7,7
        extsw 6,6
        bne 0,.L2
        blr=