Commit e135087d authored by Matthias Braun's avatar Matthias Braun
Browse files

remove (a+b)*c => a*c + b*c reassoc rule for now

This rule produces more nodes than before and is therefore very
dangerous. The original argument that localopt rules will revert this in
non-profitable cases is not good enough as in combination with CSE, etc.
not everything will get reverted.

In the future someone could write an analysis that can detect cases
where the rule will have a positive effect and reenable it for these
cases.
parent 4afe0598
......@@ -268,58 +268,6 @@ static int reassoc_commutative(ir_node **node)
return 0;
}
/**
* Reassociate using commutative law for Mul and distributive law for Mul and
* Add/Sub:
*/
static int reassoc_Mul(ir_node **node)
{
ir_node *n = *node;
if (reassoc_commutative(&n))
return 1;
ir_node *add_sub, *c;
get_comm_Binop_ops(n, &add_sub, &c);
ir_op *op = get_irn_op(add_sub);
/* handles rules R11, R12, R13, R14, R15, R16, R17, R18, R19, R20 */
if (op == op_Add || op == op_Sub) {
ir_mode *mode = get_irn_mode(n);
ir_node *block = get_nodes_block(n);
ir_node *t1 = get_binop_left(add_sub);
ir_node *t2 = get_binop_right(add_sub);
/* we can only multiplication rules on integer arithmetic */
if (mode_is_int(get_irn_mode(t1)) && mode_is_int(get_irn_mode(t2))) {
ir_node *in[] = {
new_r_Mul(block, c, t1, mode),
new_r_Mul(block, c, t2, mode)
};
ir_node *irn = create_node(NULL, block, op, mode,
ARRAY_SIZE(in), in);
/* In some cases it might happen that the new irn is equal the old
* one, for instance in:
* (x - 1) * y == x * y - y
* will be transformed back by simpler optimization
* We could switch simple optimizations off, but this only happens
* iff y is a loop-invariant expression and that it is not clear if
* the new form is better.
* So, we let the old one.
*/
if (irn != n) {
DBG((dbg, LEVEL_5, "Applied: (%n .%s. %n) %n %n => (%n %n %n) .%s. (%n %n %n)\n",
t1, get_op_name(op), t2, n, c, t1, n, c, get_op_name(op), t2, n, c));
exchange(n, irn);
*node = irn;
return 1;
}
}
}
return 0;
}
/**
* The walker for the reassociation.
*/
......@@ -682,7 +630,7 @@ void ir_register_reassoc_node_ops(void)
register_node_reassoc_func(op_Add, reassoc_commutative);
register_node_reassoc_func(op_And, reassoc_commutative);
register_node_reassoc_func(op_Eor, reassoc_commutative);
register_node_reassoc_func(op_Mul, reassoc_Mul);
register_node_reassoc_func(op_Mul, reassoc_commutative);
register_node_reassoc_func(op_Or, reassoc_commutative);
}
......
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