http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46316
--- Comment #13 from davidxl <xinliangli at gmail dot com> 2010-11-08 07:13:03
UTC ---
(In reply to comment #12)
> Won't there be similar problem when using TImode IVs on 64-bit targets (e.g.
> __int128 or int __attribute__((mode (TI)))) ?
> Normally overflows are detected when doing computations on trees rather than
> just in double_int.
yes. The following is the fix to this particular problem.
Index: tree-vrp.c
===================================================================
--- tree-vrp.c (revision 166426)
+++ tree-vrp.c (working copy)
@@ -3402,24 +3402,34 @@ adjust_range_with_scev (value_range_t *v
|| get_value_range (init)->type == VR_RANGE))
{
value_range_t maxvr = { VR_UNDEFINED, NULL_TREE, NULL_TREE, NULL };
- double_int dtmp;
- dtmp = double_int_mul (tree_to_double_int (step),
- double_int_sub (loop->nb_iterations_upper_bound,
- double_int_one));
- tem = double_int_to_tree (TREE_TYPE (init), dtmp);
- /* If the multiplication overflowed we can't do a meaningful
- adjustment. */
- if (double_int_equal_p (dtmp, tree_to_double_int (tem)))
- {
- extract_range_from_binary_expr (&maxvr, PLUS_EXPR,
- TREE_TYPE (init), init, tem);
- /* Likewise if the addition did. */
- if (maxvr.type == VR_RANGE)
- {
- tmin = maxvr.min;
- tmax = maxvr.max;
- }
- }
+ double_int upper_bound_m1, step_int, dtmp;
+ bool unsigned_p;
+
+ upper_bound_m1 = double_int_sub (loop->nb_iterations_upper_bound,
+ double_int_one);
+ step_int = tree_to_double_int (step);
+ dtmp = double_int_mul (step_int, upper_bound_m1);
+ unsigned_p = TYPE_UNSIGNED (TREE_TYPE (step));
+ /* Check overflow. */
+ if (double_int_equal_p (upper_bound_m1,
+ double_int_div (dtmp, step_int,
+ unsigned_p, ROUND_DIV_EXPR)))
+ {
+ tem = double_int_to_tree (TREE_TYPE (init), dtmp);
+ /* If the multiplication overflowed we can't do a meaningful
+ adjustment. */
+ if (double_int_equal_p (dtmp, tree_to_double_int (tem)))
+ {
+ extract_range_from_binary_expr (&maxvr, PLUS_EXPR,
+ TREE_TYPE (init), init, tem);
+ /* Likewise if the addition did. */
+ if (maxvr.type == VR_RANGE)
+ {
+ tmin = maxvr.min;
+ tmax = maxvr.max;
+ }
+ }
+ }
}
if (vr->type == VR_VARYING || vr->type == VR_UNDEFINED)
