[Bug middle-end/67052] New: tree_single_nonnegative_warnv_p and fold_relational_const are inconsistent with NaNs

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67052

            Bug ID: 67052
           Summary: tree_single_nonnegative_warnv_p and
                    fold_relational_const are inconsistent with NaNs
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Keywords: missed-optimization, wrong-code
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
                CC: jsm28 at gcc dot gnu.org
  Target Milestone: ---

int main ()
{
  double x = __builtin_nan ("");
  if (x < 0.0)
    return 1;
  return 0;
}

this simplifies via

      /* Convert ABS_EXPR<x> < 0 to false.  */
      strict_overflow_p = false;
      if (code == LT_EXPR
          && (integer_zerop (arg1) || real_zerop (arg1))
          && tree_expr_nonnegative_warnv_p (arg0, &strict_overflow_p))
        {
          if (strict_overflow_p)
            fold_overflow_warning (("assuming signed overflow does not occur "
                                    "when simplifying comparison of "
                                    "absolute value and zero"),
                                   WARN_STRICT_OVERFLOW_CONDITIONAL);
          return omit_one_operand_loc (loc, type,
                                       constant_boolean_node (false, type),
                                       arg0);
        }

(the ABS_EXPR<x> >= 0 case is guarded with ! HONOR_NANS)

but not via constant folding in fold_relational_const.

bool
tree_single_nonnegative_warnv_p (tree t, bool *strict_overflow_p)
{
...
    case REAL_CST:
      return ! REAL_VALUE_NEGATIVE (TREE_REAL_CST (t));

but

static tree
fold_relational_const (enum tree_code code, tree type, tree op0, tree op1)
{
...
      /* Handle the cases where either operand is a NaN.  */
      if (real_isnan (c0) || real_isnan (c1))
        {
...
            case LT_EXPR:
            case LE_EXPR:
            case GT_EXPR:
            case GE_EXPR:
            case LTGT_EXPR:
              if (flag_trapping_math)
                return NULL_TREE;

is this a missed optimization or wrong-code?