[Bug tree-optimization/107561] [13 Regression] g++.dg/pr71488.C and [g++.dg/warn/Warray-bounds-16.C -m32] regression due to -Wstringop-overflow problem

["rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107561

--- Comment #10 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #9)
> Note I think there's still a bug in value_range (irange) here. 
> get_size_range
> does
> 
>   if (integral)
>     {
>       value_range vr;
> 
>       query->range_of_expr (vr, exp, stmt);
> 
>       if (vr.undefined_p ())
>         vr.set_varying (TREE_TYPE (exp));
>       range_type = vr.kind ();
>       min = wi::to_wide (vr.min ());
>       max = wi::to_wide (vr.max ());
> 
> and we have vr:
> 
> (gdb) p vr
> $13 = {<irange> = {<vrange> = {
>       _vptr.vrange = 0x3693a30 <vtable for int_range<1u>+16>, 
>       m_kind = VR_ANTI_RANGE, m_discriminator = VR_IRANGE}, 
>     m_num_ranges = 1 '\001', m_max_ranges = 1 '\001', 
>     m_nonzero_mask = <tree 0x0>, m_base = 0x7fffffffc8f0}, m_ranges = {
>     <integer_cst 0x7ffff68143f0>, <integer_cst 0x7ffff5e82090>}}
> (gdb) p vr.dump (stderr)
> [irange] unsigned int [0, 0][8, +INF]$17 = void
> 
> but vr.min () produces 1 and vr.max () produces 7, just as if it doesn't
> interpret VR_ANTI_RANGE transparently here (if that's the intent?!).
> At least
> 
> // Return the highest bound of a range expressed as a tree.
> 
> inline tree
> irange::tree_upper_bound () const
> 
> suggests that.  Note that vr.num_pairs () produces 2 (because constant_p ())
> but vr.m_num_ranges is 1 and tree_upper_bound uses m_num_ranges.
> 
> I suppose irange::{min,max,tree_lower_bound,tree_upper_bound} miss "support"
> for legacy_mode_p here.

OTOH gimple-array-bounds.cc does

  const value_range *vr = NULL;
  if (TREE_CODE (low_sub_org) == SSA_NAME)
    {                
      vr = get_value_range (low_sub_org, stmt);
      if (!vr->undefined_p () && !vr->varying_p ())
        {
          low_sub = vr->kind () == VR_RANGE ? vr->max () : vr->min ();
          up_sub = vr->kind () == VR_RANGE ? vr->min () : vr->max ();
        }

so the bug is a documentation bug on min/max/lower/upper bound?!

I'm policeing other uses of value_range right now.