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 BBB3F385BF84; Fri, 20 Aug 2021 02:35:48 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org BBB3F385BF84
From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/101991] New: bit_and or bit_ior with an
 invariant inside loop is not pulled out of the loop
Date: Fri, 20 Aug 2021 02:35:48 +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: 12.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: pinskia 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
 keywords bug_severity priority component assigned_to reporter
 target_milestone
Message-ID: <bug-101991-4@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, 20 Aug 2021 02:35:48 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101991

            Bug ID: 101991
           Summary: bit_and or bit_ior with an invariant inside loop is
                    not pulled out of the loop
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take these two functions:
int f(int t, int d, int e)
{
  int r =3D d;
  for(int i =3D 0; i < t; i++)
    r &=3D e;
  return r;
}

int f1(int t, int d, int e)
{
  int r =3D d;
  if (0 < t)
    r &=3D e;
  return r;
}
They should produce the same code.  Right now f still has a loop in it.
The same is true with bit_ior.

Note the code is really bad when the vectorizer comes around really.
I forgot how I found this either.
Note clang/ICC also vectorize this code crappily.
clang on the trunk almost gets there but still has a loop:

        movl    %esi, %eax
        xorl    %esi, %esi
        testl   %edi, %edi
        cmovgl  %edi, %esi
        jle     .LBB0_6
# %bb.1:
        leal    -1(%rsi), %edi
        movl    %esi, %ecx
        andl    $7, %ecx
        cmpl    $7, %edi
        jb      .LBB0_4
# %bb.2:
        andl    $-8, %esi
        negl    %esi
        .p2align        4, 0x90
.LBB0_3:                                # =3D>This Inner Loop Header: Depth=
=3D1
        addl    $8, %esi
        jne     .LBB0_3
.LBB0_4:
        andl    %edx, %eax
        testl   %ecx, %ecx
        je      .LBB0_6
        .p2align        4, 0x90
.LBB0_5:                                # =3D>This Inner Loop Header: Depth=
=3D1
        addl    $-1, %ecx
        jne     .LBB0_5
.LBB0_6:
        retq=