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 3914D3858D20; Fri, 31 Mar 2023 07:17:51 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 3914D3858D20
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1680247071;
	bh=p10ynTucJ8V1SL5ih0bkcWo+u/m95aHPXO2t8oIhhh4=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=sku0BWEPW0ENsUxw8+5mdlZ29h6++uNSa0m6a3uL34D6bA/1rryv1Mm7Q/Sf80VQm
	 CWOwM0oMnpEdLe+rySWHCRnIxQkY78d7pAuzuSH6iEIrMFEFn5qHqKMmIniTjfqAeP
	 Wm3JQv8nACVnF/OM1Az8U2al9Hr8wo+1sUH4i2zs=
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/109350] FAIL:
 g++.dg/warn/Wstringop-overflow-4.C
Date: Fri, 31 Mar 2023 07:17:50 +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: 13.0
X-Bugzilla-Keywords: diagnostic
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rguenth 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: cc
Message-ID: <bug-109350-4-PLTvMIHDpV@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-109350-4@http.gcc.gnu.org/bugzilla/>
References: <bug-109350-4@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=3D109350

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |amacleod at redhat dot com

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Hmm, the same reproduces with r_imin_imax as ptrdiff_t but the IL is a bit
more obvious:

<bb 2> [local count: 1073741824]:
_27 =3D{v} signed_value_source;
_4 =3D (unsigned long) _27;
_8 =3D _4 + 2147483648;
if (_8 > 4294967295)
  goto <bb 8>; [50.00%]
else
  goto <bb 3>; [50.00%]

<bb 3> [local count: 536870913]:
_30 =3D _27 + 1;
_28 =3D (sizetype) _30;
if (_4 <=3D 4611686018427387900)
  goto <bb 4>; [50.00%]
else
  goto <bb 5>; [50.00%]

<bb 5> [local count: 268435458]:
_12 =3D operator new [] (18446744073709551615);
__builtin_memcpy (_12, &MEM <const char[37]> [(void
*)"0123456789abcdefghijklmnopqrstuvwxyz" + 35B], 2);
sink (_12);
if (_28 <=3D 4611686018427387900)
  goto <bb 9>; [100.00%]
else
  goto <bb 7>; [0.00%]

<bb 9> [local count: 0]:
iftmp.2_37 =3D _28 * 2;
_39 =3D operator new [] (iftmp.2_37);
__builtin_memcpy (_39, &MEM <const char[37]> [(void
*)"0123456789abcdefghijklmnopqrstuvwxyz" + 34B], 3);

so we have (unsigned long)[int_min, int_max] > 4611686018427387900
&& (unsigned long)[int_min+1, int_max+1] <=3D 4611686018427387900 to
constrain _4.  I don't see how we can arrive at [0,0] for iftmp.2_37.

In fact if I put this into a separate testcase like

void __attribute__((noipa))
foo (long signed_value_source)
{
  unsigned long temu =3D signed_value_source;
  if (temu + 2147483648 > 4294967295)
    ;
  else
    {
     long tems =3D signed_value_source + 1;
     unsigned long temu2 =3D tems;
     if (temu > 4611686018427387900)
       if (temu2 <=3D 4611686018427387900)
         {
           unsigned long iftmp =3D temu2 * 2;
           if (iftmp =3D=3D 0)
             __builtin_abort ();
         }
    }
}

then we optimize this to

  <bb 2> [local count: 1073741824]:
  temu_3 =3D (long unsigned int) signed_value_source_2(D);
  _1 =3D temu_3 + 2147483648;
  if (_1 > 4294967295)
    goto <bb 5>; [50.00%]
  else
    goto <bb 3>; [50.00%]

  <bb 3> [local count: 536870913]:
  if (signed_value_source_2(D) =3D=3D -1)
    goto <bb 4>; [0.00%]
  else
    goto <bb 5>; [100.00%]

  <bb 4> [count: 0]:
  __builtin_abort ();

and the outer if doesn't change the inner range result.=