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 3FF423858C54; Tue, 23 May 2023 17:52:01 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 3FF423858C54
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1684864322;
	bh=XKbgpzS8OWBU0t/1DhssKdvV1ZjhQxuBtcUtmNFowcw=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=Wvin6uLXDsia6ZJxoPrnGRjBwX+KSxl5eeqKJ8bbKtQyKzWjCuEXvBlwEQ9bYISSa
	 MsQLQlWnGpeUXQ+Oewm6asYtCKLGevEm6sMvQG4WOhMYdqwa9ocWHzUT0La/+O7eCd
	 JUW45Eeuklvs1QMJk5yDgABFOOHT6nncUHE4N8Us=
From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/109945] Escape analysis hates copy elision:
 different result with -O1 vs -O2
Date: Tue, 23 May 2023 17:52:01 +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: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: pinskia at gcc dot gnu.org
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: rguenth at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-109945-4-YSV38HEwby@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-109945-4@http.gcc.gnu.org/bugzilla/>
References: <bug-109945-4@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=3D109945

--- Comment #9 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #8)
> (In reply to Arthur O'Dwyer from comment #7)
> > // https://godbolt.org/z/Ea43Y65z4
> > struct Widget {
> >     int i =3D 1;
> ...
> > In this case, Widget has no constructors,
>=20
> No, it has a constructor because of the NSDMI . NSDMI causes a non-trival
> constexpr constructor to be created.

Now this version does not:
```
struct Widget {
    int i;
    int a[4];
};
Widget *global =3D 0;
Widget make2() { Widget w; w.i =3D 1; global =3D &w; return w; }
void g() { global->i =3D 42; }
int main() {
  Widget w =3D make2();
  int i =3D w.i;
  g();
  return (i =3D=3D w.i);
    // Does this need to be reloaded and
    // compared? or is it obviously true?=20=20
}
```

But does w go out of the scope at the end of make2? Similar question to mak=
e in
the original testcase, does the temp go out of scope?=