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From: "aldyh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/97721] [11 Regression] ICE in verify_range,
 at value-range.cc:361
Date: Thu, 05 Nov 2020 11:49:26 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97721

--- Comment #8 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #7)
> But TREE_OVERFLOW is meaningful during evaluation, e.g. inside of VRP or
> when folding some expression.  It just doesn't belong into the GIMPLE IL.
> So I'd say it would be better for ranger when it sees TREE_OVERFLOW const=
ant
> somewhere in the IL not to set the range to that constant, but to
> drop_tree_overflow of it.

That's certainly the easiest path for us.  We could drop_overflow in
get_tree_range while creating said ranges, and then no other changes to the
ranger are needed.

However, I wonder if compare_values_warnv is being unnecessarily restrictiv=
e.=20
For example, here, we bail on overflow, even though tree_int_cst_compare,
through its use of wi::cmps, is perfectly capable of comparing these intege=
rs:

  if (!POINTER_TYPE_P (TREE_TYPE (val1)))
    {
      /* We cannot compare overflowed values.  */
      if (TREE_OVERFLOW (val1) || TREE_OVERFLOW (val2))
        return -2;

      if (TREE_CODE (val1) =3D=3D INTEGER_CST
          && TREE_CODE (val2) =3D=3D INTEGER_CST)
        return tree_int_cst_compare (val1, val2);

as well as here:

     if (TREE_CODE (val1) =3D=3D INTEGER_CST && TREE_CODE (val2) =3D=3D INT=
EGER_CST)
        {
          /* We cannot compare overflowed values.  */
          if (TREE_OVERFLOW (val1) || TREE_OVERFLOW (val2))
            return -2;

          return tree_int_cst_compare (val1, val2);
        }=