*
* @return The first irn having some data assigned, NULL otherwise
*/
-ir_node *phase_get_first_node(ir_phase *phase);
+ir_node *phase_get_first_node(const ir_phase *phase);
/**
* Returns the next node after @p start having some data assigned.
*
* @return The next node after start having some data assigned, NULL otherwise
*/
-ir_node *phase_get_next_node(ir_phase *phase, ir_node *start);
+ir_node *phase_get_next_node(const ir_phase *phase, ir_node *start);
/**
* Convenience macro to iterate over all nodes of a phase