-static void rsm_add_reg(register_state_mapping_t *rsm,
- const arch_register_t *reg, arch_irn_flags_t flags)
+/**
+ * Add a register and its constraint flags to a register state map
+ * and return its index inside the map.
+ */
+static int rsm_add_reg(register_state_mapping_t *rsm,
+ const arch_register_t *reg,
+ arch_register_req_type_t flags)