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 03CAE3846450; Wed, 17 May 2023 14:35:36 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 03CAE3846450
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1684334137;
	bh=UpjW3RGOQEuXqGECdZCo6u/xTuT8URnrTI4J85LJG8w=;
	h=From:To:Subject:Date:From;
	b=kdjMGLWN44sazk4OHO7h9+mawvU94Ai/VZiH/TrfkxeEIQGNRkcEqxDEKtv17iWMy
	 tfDvQKl2P+tRJ1HtqZomn58aulUMNK14G/4DDY97EPb2WjFjWcTWMFslw4iqqU+Fil
	 QC+JVDa3pWbGbN1ZgyWx7lJ/jl5uwAO7MxxY8tbQ=
From: "amonakov at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/109892] New: SLP failure with explicit fma
Date: Wed, 17 May 2023 14:35:36 +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: 13.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: amonakov 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-109892-4@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=3D109892

            Bug ID: 109892
           Summary: SLP failure with explicit fma
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amonakov at gcc dot gnu.org
  Target Milestone: ---

At -O2 -mfma (x86) or -O3 (arm64) we fail to SLP-vectorize 'f', but succeed=
 in
'g':

double f(double x[], long n)
{
    double r0 =3D 0, r1 =3D 0;
    for (; n; x +=3D 2, n--) {
        r0 =3D __builtin_fma(x[0], x[0], r0);
        r1 =3D __builtin_fma(x[1], x[1], r1);
    }
    return r0 + r1;
}
static double muladd(double x, double y, double z)
{
    return x * y + z;
}
double g(double x[], long n)
{
    double r0 =3D 0, r1 =3D 0;
    for (; n; x +=3D 2, n--) {
        r0 =3D muladd(x[0], x[0], r0);
        r1 =3D muladd(x[1], x[1], r1);
    }
    return r0 + r1;
}

It seems we are calling vectorizable_reduction for __builtin_fma even thoug=
h it
would not participate in a reduction when vectorizing for 16-byte vectors?=