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From: "msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/107038] [13 Regression] Bogus
 -Wstringop-overflow= since r13-2789-gb40b3035879cf695
Date: Mon, 26 Sep 2022 16:16:37 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107038

--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
Just a quick note from what I see in GDB.  The warning is issued by the 2nd=
 run
of the waccess pass (-fdump-tree-waccess2) for the following statement in b=
b 22
in pread():

  iftmp.21_88 =3D __pread_alias (_50, _82, _81, _79);

_81's range reported by range_query::range_of_expr (vr, exp, stmt) is [58,
ULONG_MAX], matching the range in the warning.

A partial output of debug_ranger() for the function is below.  I must be
reading it wrong because  I don't see what the range above is derived from.

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D BB 19 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
Imports: recvd_78  _83=20=20
Exports: _51  recvd_78  recvd.17_80  _83  _94  _116  _125=20=20
_83     [irange] UNDEFINED
    <bb 19> [local count: 169058114]:
    if (_83 =3D=3D 18446744073709551615)
      goto <bb 22>; [34.00%]
    else
      goto <bb 20>; [66.00%]

19->22  (T) _83 :       [irange] UNDEFINED
19->20  (F) _83 :       [irange] UNDEFINED

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D BB 20 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
Imports: _81  _83=20=20
Exports: _81  _83  _85  _86  _87=20=20
         _85 : _81(I)  _83(I)=20=20
         _86 : _81(I)  _83(I)  _85=20=20
         _87 : _81(I)  _83(I)  _85  _86=20=20
_81     [irange] long unsigned int VARYING
_83     [irange] long unsigned int VARYING
    <bb 20> [local count: 280636469]:
    _85 =3D _81 <=3D _83;
    _86 =3D (int) _85;
    _87 =3D __builtin_constant_p (_86);
    if (_87 !=3D 0)
      goto <bb 21>; [50.00%]
    else
      goto <bb 24>; [50.00%]

_86 : [irange] int [0, 1] NONZERO 0x1
_87 : [irange] int [0, 0] NONZERO 0x0
20->21  (T) _81 :       [irange] UNDEFINED
20->21  (T) _83 :       [irange] UNDEFINED
20->21  (T) _85 :       [irange] UNDEFINED
20->21  (T) _86 :       [irange] UNDEFINED
20->21  (T) _87 :       [irange] UNDEFINED
20->24  (F) _86 :       [irange] int [0, 1] NONZERO 0x1
20->24  (F) _87 :       [irange] int [0, 0] NONZERO 0x0

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D BB 21 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
Imports: recvd_78  _81  _83=20=20
Exports: _51  recvd_78  recvd.17_80  _81  _83  _94  _116  _125=20=20
_81     [irange] UNDEFINED
_83     [irange] UNDEFINED
    <bb 21> [local count: 140318235]:
    if (_81 <=3D _83)
      goto <bb 22>; [50.00%]
    else
      goto <bb 23>; [50.00%]

21->22  (T) _81 :       [irange] UNDEFINED
21->22  (T) _83 :       [irange] UNDEFINED
21->23  (F) _81 :       [irange] UNDEFINED
21->23  (F) _83 :       [irange] UNDEFINED

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D BB 22 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
    <bb 22> [local count: 127638877]:
    iftmp.21_88 =3D __pread_alias (_50, _82, _81, _79);
    goto <bb 25>; [100.00%]=