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 AD1F23858C41; Fri,  3 Nov 2023 07:20:16 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org AD1F23858C41
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1698996016;
	bh=fqtmE22ntteAVoig71qoP/cuTOTWpnoIptbBRuNEgn0=;
	h=From:To:Subject:Date:From;
	b=oMTjEfw1+RVQUCNNXHTzLk/Ev4vCzRb8X8XrLvPCcVMpCtt8xGUbxdzdw5qX2rb4i
	 ecRfOBC1oxLdVlc2DINZUvhqhrz6PtrJc05wIUhj44VlD50/c/ip7B3xAU6z3FcBWJ
	 J7mkdeb9vfhQ9Mmng20n9A3k45PJR5khBj2lKzNU=
From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/112361] New: [14 Regression]
 avx512f-reduce-op-1.c miscompiled since r14-5076
Date: Fri, 03 Nov 2023 07:20:16 +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: 14.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: jakub 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-112361-4@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
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112361

            Bug ID: 112361
           Summary: [14 Regression] avx512f-reduce-op-1.c miscompiled
                    since r14-5076
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jakub at gcc dot gnu.org
  Target Milestone: ---

Since r14-5076-g01c18f58d37865d5f3bbe93e666183b54ec608c7 I see
gcc.target/i386/avx512f-reduce-op-1.c execution failure.
Reduced -O2 -mavx512f:
__attribute__((noipa)) float
foo (void)
{
  float a[16] =3D { 1, 2, 3, 4, 5, 6, 6, 5, 4, 3, 2, 1, 7, 6, 5, 4 };
  float r3 =3D 0.0f;
  for (int i =3D 0; i < 16; i++)
    if ((1 << i) & 0xA6BA)
      r3 =3D r3 + a[i];
  return r3;
}

int
main ()
{
  if (foo () !=3D 37.0f)
    __builtin_abort ();
}
where before r14-5076 r3 has been correctly computed as 37.0f, but starting
with r14-5076 it is 64.0f, i.e. the masking is ignored and all elements are
added, not just the ones under the mask.
The ifcvt dump has
  _1 =3D 42682 >> i_31;
  _2 =3D _1 & 1;
  _24 =3D _2 !=3D 0;
  _3 =3D a[i_31];
  _ifc__43 =3D .COND_ADD (_24, r3_29, _3, r3_29);
which I assume is correct, and vect dump shows computation of the mask but =
then
instead of using masked addition and at the end of loop reduction (well, ca=
n we
vectorize it at all without -ffast-math?) it scalarizes the addition but
doesn't actually conditionalize it.  Note, with -O2 -mavx512f -ffast-math t=
he
.COND_ADD is actually vectorized and so correctly returns 37.0f.=