Hi!
While working on previous patch, I've noticed a severe omission in the
-fsanitize=signed-integer-overflow support. Nothing ever
folds addition/subtraction of 0 and multiplication by [0,1], none of these
may ever overflow and thus we can fold them to normal operations and let
those be folded as normal operations.
Bootstrapped/regtested on x86_64-linux and i686-linux, tested with
--with-build-config=bootstrap-ubsan bootstrap on i686-linux, ok for trunk?
2014-03-25 Jakub Jelinek <ja...@redhat.com>
* tree-vrp.c (simplify_internal_call_using_ranges): If only
one range is range_int_cst_p, but not both, at least optimize
addition/subtraction of 0 and multiplication by 0 or 1.
--- gcc/tree-vrp.c.jj 2014-03-12 10:14:18.000000000 +0100
+++ gcc/tree-vrp.c 2014-03-24 16:14:50.822674164 +0100
@@ -9336,31 +9336,58 @@ simplify_internal_call_using_ranges (gim
else if (TREE_CODE (op0) == INTEGER_CST)
set_value_range_to_value (&vr0, op0, NULL);
else
- return false;
+ set_value_range_to_varying (&vr0);
if (TREE_CODE (op1) == SSA_NAME)
vr1 = *get_value_range (op1);
else if (TREE_CODE (op1) == INTEGER_CST)
set_value_range_to_value (&vr1, op1, NULL);
else
- return false;
+ set_value_range_to_varying (&vr1);
- if (!range_int_cst_p (&vr0) || !range_int_cst_p (&vr1))
- return false;
-
- tree r1 = int_const_binop (subcode, vr0.min, vr1.min);
- tree r2 = int_const_binop (subcode, vr0.max, vr1.max);
- if (r1 == NULL_TREE || TREE_OVERFLOW (r1)
- || r2 == NULL_TREE || TREE_OVERFLOW (r2))
- return false;
- if (subcode == MULT_EXPR)
+ if (!range_int_cst_p (&vr0))
+ {
+ /* If one range is VR_ANTI_RANGE, VR_VARYING etc.,
+ optimize at least x = y + 0; x = y - 0; x = y * 0;
+ and x = y * 1; which never overflow. */
+ if (!range_int_cst_p (&vr1))
+ return false;
+ if (tree_int_cst_sgn (vr1.min) == -1)
+ return false;
+ if (compare_tree_int (vr1.max, subcode == MULT_EXPR) == 1)
+ return false;
+ }
+ else if (!range_int_cst_p (&vr1))
+ {
+ /* If one range is VR_ANTI_RANGE, VR_VARYING etc.,
+ optimize at least x = 0 + y; x = 0 * y; and x = 1 * y;
+ which never overflow. */
+ if (subcode == MINUS_EXPR)
+ return false;
+ if (!range_int_cst_p (&vr0))
+ return false;
+ if (tree_int_cst_sgn (vr0.min) == -1)
+ return false;
+ if (compare_tree_int (vr0.max, subcode == MULT_EXPR) == 1)
+ return false;
+ }
+ else
{
- tree r3 = int_const_binop (subcode, vr0.min, vr1.max);
- tree r4 = int_const_binop (subcode, vr0.max, vr1.min);
- if (r3 == NULL_TREE || TREE_OVERFLOW (r3)
- || r4 == NULL_TREE || TREE_OVERFLOW (r4))
+ tree r1 = int_const_binop (subcode, vr0.min, vr1.min);
+ tree r2 = int_const_binop (subcode, vr0.max, vr1.max);
+ if (r1 == NULL_TREE || TREE_OVERFLOW (r1)
+ || r2 == NULL_TREE || TREE_OVERFLOW (r2))
return false;
+ if (subcode == MULT_EXPR)
+ {
+ tree r3 = int_const_binop (subcode, vr0.min, vr1.max);
+ tree r4 = int_const_binop (subcode, vr0.max, vr1.min);
+ if (r3 == NULL_TREE || TREE_OVERFLOW (r3)
+ || r4 == NULL_TREE || TREE_OVERFLOW (r4))
+ return false;
+ }
}
+
gimple g = gimple_build_assign_with_ops (subcode, gimple_call_lhs (stmt),
op0, op1);
gsi_replace (gsi, g, false);
Jakub
