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 CD2D13858D35; Fri, 15 Sep 2023 12:35:27 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org CD2D13858D35
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1694781327;
	bh=jZVF/5eAoSznDSBjM5ot0W0chuXyeTcZasDc3g4NBBg=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=XcBsYWyoWjcRDMH1rVR/hrZfKmFPXCzU9gdt6XpZ9/oNchFLWQPPWYlYpLQXxsXLz
	 oK4ixQMpRDWhmqPnllLZLhb/8XmJoQCKbEsaRpjq/Iny6XAMG5Q4PSFS4eZt3NuZJS
	 47h+gc9xGNCxN3k8XdcL91w7na2Nh2MP0QvPD7aM=
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/111422] Wrong code at -O3 on x86_64-linux-gnu
Date: Fri, 15 Sep 2023 12:35:27 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: missed-optimization, needs-bisection, wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rguenth 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: keywords
Message-ID: <bug-111422-4-33MDAuKuAh@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-111422-4@http.gcc.gnu.org/bugzilla/>
References: <bug-111422-4@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=3D111422

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
There's a missed optimization.  We have

  # PT =3D { D.2843 }
  _44 =3D &g + _43;
...
  *_44 =3D 8;
  g =3D{v} {CLOBBER(eol)};
...
  *_44 =3D 8;
  g =3D{v} {CLOBBER(eol)};
...
  *_44 =3D 8;
  g =3D{v} {CLOBBER(eol)};

I guess the clobber doesn't kill the ref according to stmt_kills_ref_p,
we'd have to special-case singleton points-to sets here.  Optimizing the
stores would avoid the bogus sharing of g and n.=