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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/110702] [12/13/14 Regression] Wrong code at
 -O1 on x86_64-linux-gnu (regression since GCC-12.2)
Date: Thu, 03 Aug 2023 09:32:51 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110702

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|needs-bisection             |
             Status|NEW                         |ASSIGNED
                 CC|                            |hubicka at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot =
gnu.org
          Component|middle-end                  |tree-optimization

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
I think the bisected rev just exposes an existing issue.  Namely IVOPTs
generates

  _1 =3D MEM[(long int *)_52];
  _3 =3D MEM[(long int *)0B + ivtmp.36_9 + ivtmp.28_44 * 4];
  _4 =3D (int) _3;
  _2 =3D (int) _1;
  _5 =3D _2 | _4;

with -fno-ivopts it works fine and we sink

  _1 =3D e[0][0][b.7_29];
  _3 =3D e[a.9_30][b.7_29][a.9_30];

the issue is without IVOPTs the late pure-const pass correctly does nothing
but with IVOPTs and the above MEMs we get it to produce pure because:

  scanning: _1 =3D MEM[(long int *)_52];
    Indirect ref read is not const
  NULL memory access; terminating BB

which is because infer_nonnull_range_by_dereference eventually does

static bool
check_loadstore (gimple *, tree op, tree, void *data)
{
  if (TREE_CODE (op) =3D=3D MEM_REF || TREE_CODE (op) =3D=3D TARGET_MEM_REF)
    {=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20
      /* Some address spaces may legitimately dereference zero.  */
      addr_space_t as =3D TYPE_ADDR_SPACE (TREE_TYPE (op));
      if (targetm.addr_space.zero_address_valid (as))
        return false;

      return operand_equal_p (TREE_OPERAND (op, 0), (tree)data, 0);=