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 7F47E3857C62; Fri, 28 Aug 2020 09:23:58 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 7F47E3857C62
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
 s=default; t=1598606638;
 bh=8B9t3e/BGXBfiO5mBxHUsJG7ij9roiRXobKzY4mFXqQ=;
 h=From:To:Subject:Date:From;
 b=WMC6XT/fjMmiidWgvpfJZ72YWUafjDu6QMVLMMMYIR6tpCRDmLb/4kYZW5j2PYLD8
 OcZPcJTppktVMLdpo1BU46x5LcvznY1Qkx4ik6lt5oGtzJrF/Ha3Eg63ABlGGX6En2
 DIq0WFWi23yrMUlzYENVGXTrwfi+kks4cABBCeXE=
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/96831] New: gcc.dg/tree-ssa/scev-[345].c FAIL
 on i?86 and arm
Date: Fri, 28 Aug 2020 09:23:58 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 11.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rguenth at gcc dot gnu.org
X-Bugzilla-Status: UNCONFIRMED
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: bug_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter target_milestone
Message-ID: <bug-96831-4@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, 28 Aug 2020 09:23:58 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D96831

            Bug ID: 96831
           Summary: gcc.dg/tree-ssa/scev-[345].c FAIL on i?86 and arm
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
  Target Milestone: ---

The testcases now FAIL after dumping TARGET_MEM_REF bases as &a instead of
symbol: a and thus show that IVOPTs doesn't consider using a pointer IV:

For lp64 (x86_64) I see

  <bb 4> :
  _10 =3D (sizetype) k_4(D);
  _8 =3D _10 * 8;
  _6 =3D (sizetype) k_4(D);
  _3 =3D _6 * 8;
  _2 =3D _3 + 4;
  _1 =3D &a + _2;
  ivtmp.5_7 =3D (unsigned long) _1;

  <bb 5> :
  # i_12 =3D PHI <k_4(D)(4), i_9(6)>
  # ivtmp.5_5 =3D PHI <ivtmp.5_7(4), ivtmp.5_11(6)>
  _1_16 =3D (int *) ivtmp.5_5;
  a_p =3D _1_16;
  _19 =3D (void *) ivtmp.5_5;
  MEM[(int *)_19] =3D 100;
  i_9 =3D k_4(D) + i_12;
  ivtmp.5_11 =3D ivtmp.5_5 + _8;
  if (i_9 <=3D 999)

so the ADDRESS use and the dereference use use the same IV.  But with ilp32
we end up with

  <bb 5> :
  # i_12 =3D PHI <k_4(D)(4), i_9(6)>
  _5 =3D (unsigned int) &a;
  _11 =3D (unsigned int) i_12;
  _10 =3D _11 * 8;
  _8 =3D _5 + _10;
  _7 =3D _8 + 4;
  _6 =3D (int *) _7;
  _1_16 =3D _6;
  a_p =3D _1_16;
  _3 =3D (sizetype) i_12;
  MEM[(int *)&a + _3 * 8] =3D 100;
  i_9 =3D k_4(D) + i_12;
  if (i_9 <=3D 999)

(scev-4.c) and eventually

.L2:
        movl    $100, a+4(,%eax,8)
        leal    a+4(,%eax,8), %ecx
        addl    %edx, %eax
        cmpl    $999, %eax
        jle     .L2
        movl    %ecx, a_p

instead of

.L3:
        addl    %edi, %ecx
        movl    $100, (%rax)
        movq    %rax, %rsi
        addq    %rdx, %rax
        cmpl    $999, %ecx
        jle     .L3
        movq    %rsi, a_p(%rip)

it's not entirely clear whether based on costs one is better than the other
(we are not able to replace the COMPARE use and thus the tested for variant
uses one more IV).=