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 620103857805; Thu,  8 Apr 2021 07:19:45 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 620103857805
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/99966] Bounds check not eliminated by assert
Date: Thu, 08 Apr 2021 07:19:45 +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: 11.0
X-Bugzilla-Keywords: 
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: cf_reconfirmed_on everconfirmed bug_status blocked
Message-ID: <bug-99966-4-QDExtvuQsx@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-99966-4@http.gcc.gnu.org/bugzilla/>
References: <bug-99966-4@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
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Thu, 08 Apr 2021 07:19:45 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99966

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2021-04-08
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
             Blocks|                            |85316

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
For the testcase the issue is that the range check is inside the loop and
eliminating it requires symbolic range propagation to work "better".

We arrive at

i_28: long unsigned int [_32, +INF]  EQUIVALENCES: { i_1 i_12 } (2 elements)
i_12: size_t VARYING

for

  <bb 2> [local count: 118253447]:
  if (start_4(D) < end_5(D))
    goto <bb 3>; [99.96%]
  else
    goto <bb 4>; [0.04%]

  <bb 3> [local count: 118206146]:
  _9 =3D MEM[(const struct vector *)data_7(D)].D.18843._M_impl.D.18156._M_f=
inish;
  _8 =3D MEM[(const struct vector *)data_7(D)].D.18843._M_impl.D.18156._M_s=
tart;
  _14 =3D _9 - _8;
  _15 =3D _14 /[ex] 8;
  _16 =3D (long unsigned int) _15;
  _33 =3D _16 >=3D end_5(D);
  _34 =3D _16 > start_4(D);
  _22 =3D _33 & _34;
  if (_22 !=3D 0)
    goto <bb 7>; [99.92%]
  else
    goto <bb 4>; [0.08%]

  <bb 4> [local count: 141847]:
  __assert_fail ("start < end && start < data.size() && end <=3D data.size(=
)",
"t.C", 7, "uint64_t f(std::vector<long unsigned int>&, size_t, size_t)");

  <bb 5> [local count: 834435851]:
  if (i_12 >=3D _16)
    goto <bb 6>; [0.05%]
  else
    goto <bb 7>; [99.95%]

  <bb 6> [local count: 381018]:
  # i_38 =3D PHI <i_12(5)>
  std::__throw_out_of_range_fmt ("vector::_M_range_check: __n (which is %zu=
) >=3D
this->size() (which is %zu)", i_38, _16);

  <bb 7> [local count: 952166435]:
  # total_3 =3D PHI <total_11(5), 0(3)>
  # i_2 =3D PHI <i_12(5), start_4(D)(3)>
  _10 =3D MEM[(value_type &)_8 + i_2 * 8];
  total_11 =3D total_3 + _10;
  i_12 =3D i_2 + 1;
  if (i_12 !=3D end_5(D))
    goto <bb 5>; [87.64%]
  else
    goto <bb 8>; [12.36%]

  <bb 8> [local count: 117730583]:
  # total_37 =3D PHI <total_11(7)>
  return total_37;


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D85316
[Bug 85316] [meta-bug] VRP range propagation missed cases=