(make_range, case PLUS_EXPR): Normalize an unsigned

range that wraps around 0.

From-SVN: r13030

gcc/fold-const.c

@@ -2809,7 +2809,15 @@ make_range (exp, pin_p, plow, phigh)
 	      || (n_high != 0 && TREE_OVERFLOW (n_high)))
 	    break;
 
-	  low = n_low, high = n_high;
+	  /* Check for an unsigned range which has wrapped around the maximum
+	     value thus making n_high < n_low, and normalize it.  */
+	  if (n_low && n_high && tree_int_cst_lt (n_high, n_low))
+	    {
+	      low = n_high, high = n_low;
+	      in_p = ! in_p;
+	    }
+	  else
+	    low = n_low, high = n_high;
 	  exp = arg0;
 	  continue;