* tree-vrp.c (extract_range_from_unary_expr): Handle type

[pf3gnuchains/gcc-fork.git] / gcc / tree-vrp.c

diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index 217ecc3..81b0c0a 100644 (file)
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -1286,6 +1286,35 @@ extract_range_from_unary_expr (value_range_t *vr, tree expr)
       tree inner_type = TREE_TYPE (op0);
       tree outer_type = TREE_TYPE (expr);
 
+      /* If VR0 represents a simple range, then try to convert
+        the min and max values for the range to the same type
+        as OUTER_TYPE.  If the results compare equal to VR0's
+        min and max values and the new min is still less than
+        or equal to the new max, then we can safely use the newly
+        computed range for EXPR.  This allows us to compute
+        accurate ranges through many casts.  */
+      if (vr0.type == VR_RANGE)
+       {
+         tree new_min, new_max;
+
+         /* Convert VR0's min/max to OUTER_TYPE.  */
+         new_min = fold_convert (outer_type, vr0.min);
+         new_max = fold_convert (outer_type, vr0.max);
+
+         /* Verify the new min/max values are gimple values and
+            that they compare equal to VR0's min/max values.  */
+         if (is_gimple_val (new_min)
+             && is_gimple_val (new_max)
+             && tree_int_cst_equal (new_min, vr0.min)
+             && tree_int_cst_equal (new_max, vr0.max)
+             && compare_values (new_min, new_max) <= 0
+             && compare_values (new_min, new_max) >= -2)
+           {
+             set_value_range (vr, VR_RANGE, new_min, new_max, vr->equiv);
+             return;
+           }
+       }
+
       /* When converting types of different sizes, set the result to
         VARYING.  Things like sign extensions and precision loss may
         change the range.  For instance, if x_3 is of type 'long long