+
+/* Some interfaces may be related such that accessing one interface
+ has side effects on a set of related interfaces. The interfaces
+ are partitioned into equivalence classes of related interfaces, and
+ each class is assigned a unique identifier number. This function
+ returns the class identifier for an interface, or XTENSA_UNDEFINED
+ on error. These identifiers can be compared to determine if two
+ interfaces are related; the specific values of the identifiers have
+ no particular meaning otherwise. */
+
+extern int
+xtensa_interface_class_id (xtensa_isa isa, xtensa_interface intf);
+
+