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 818723857C48; Wed, 15 Feb 2023 18:43:09 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 818723857C48
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1676486589;
	bh=nnZcmhzIcOQeaVZmah99TdOdHzaXef35ePYQFmeDX6Q=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=WM/4ZiOpuUaOxiqzbrQ7c+PIOSk/hYJny+hR5nLX1GY70Nm6gtL09yjPPFYCUWmC4
	 g4RM8rDuzWfpMEX7NWuEMu3WOyCXZr/FVw6ZQFomGjTA156WAcX/A8D1xZoROmXSV8
	 3JA/xlXkN4tA0E3qAtF1Wn9g73MKpfKgqzVM6E5w=
From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/108657] [13 Regression] csmith: possible wrong
 checksum with -O3 and -ftrivial-auto-var-init=zero
Date: Wed, 15 Feb 2023 18:43:09 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: middle-end
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: needs-reduction, wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: jakub 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: 13.0
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: everconfirmed bug_status cf_reconfirmed_on
Message-ID: <bug-108657-4-TCvCOKvWHK@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-108657-4@http.gcc.gnu.org/bugzilla/>
References: <bug-108657-4@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=3D108657

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2023-02-15

--- Comment #17 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
In the assembly, the important difference is that with just -O3 c is assign=
ed 1
before calling the first bar, while -O3 -ftrivial-auto-var-init=3Dzero it is
assigned 0.  This is visible already in optimized dump, which for the latter
stores first c =3D 1; and then twice c =3D 0; among the various DEFERRED_IN=
ITs.

Even further reduced:
int c, e, f;
static int *d =3D &c;

__attribute__((noipa)) void
foo (void)
{
  if (c !=3D 1)
    __builtin_abort ();
}

int
main ()
{
  for (c =3D 1; c >=3D 0; c--)
    {
      e =3D 0;
      for (int j =3D 0; j <=3D 2; j++)
        {
          short k[1];
          if (e)
            break;
          e ^=3D f;
        }
    }
  *d =3D 1;
  foo ();
}=