gcc/cp/ChangeLog:

	* cp-tree.h (cp_operator_id, cp_assignment_operator_id): Document.

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index da45d95..b4795d2 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -209,8 +209,19 @@ extern GTY(()) tree cp_global_trees[CPTI_MAX];
 /* std::align_val_t */
 #define align_type_node			cp_global_trees[CPTI_ALIGN_TYPE]
 
-/* We cache these tree nodes so as to call get_identifier less
-   frequently.  */
+/* We cache these tree nodes so as to call get_identifier less frequently.
+   For identifiers for functions, including special member functions such
+   as ctors and assignment operators, the nodes can be used (among other
+   things) to iterate over their overloads defined by/for a type.  For
+   example:
+
+     tree ovlid = cp_assignment_operator_id (NOP_EXPR);
+     tree overloads = lookup_fnfields_slot (type, ovlid);
+     for (ovl_iterator it (overloads); it; ++it) { ... }
+
+   iterates over the set of implicitly and explicitly defined overloads
+   of the assignment operator for type (including the copy and move
+   assignment operators, whether deleted or not).  */
 
 /* The name of a constructor that takes an in-charge parameter to
    decide whether or not to construct virtual base classes.  */
@@ -231,6 +242,18 @@ extern GTY(()) tree cp_global_trees[CPTI_MAX];
 /* The name of a destructor that destroys virtual base classes, and
    then deletes the entire object.  */
 #define deleting_dtor_identifier	cp_global_trees[CPTI_DELETING_DTOR_IDENTIFIER]
+
+/* The name of the identifier used internally to represent operator CODE.  */
+#define cp_operator_id(CODE) \
+  (operator_name_info[(int) (CODE)].identifier)
+
+/* The name of the identifier used to represent assignment operator CODE,
+   both simple (i.e., operator= with CODE == NOP_EXPR) and compound (e.g.,
+   operator+= with CODE == PLUS_EXPR).  Includes copy and move assignment.
+   Use copy_fn_p() to test specifically for copy assignment.  */
+#define cp_assignment_operator_id(CODE)				\
+  (assignment_operator_name_info[(int) (CODE)].identifier)
+
 #define delta_identifier		cp_global_trees[CPTI_DELTA_IDENTIFIER]
 #define in_charge_identifier		cp_global_trees[CPTI_IN_CHARGE_IDENTIFIER]
 /* The name of the parameter that contains a pointer to the VTT to use
@@ -1731,10 +1754,6 @@ struct GTY(()) language_function {
    || (NAME) == cp_operator_id (DELETE_EXPR)	\
    || (NAME) == cp_operator_id (VEC_DELETE_EXPR))
 
-#define cp_operator_id(CODE) \
-  (operator_name_info[(int) (CODE)].identifier)
-#define cp_assignment_operator_id(CODE) \
-  (assignment_operator_name_info[(int) (CODE)].identifier)
 /* In parser.c.  */
 extern tree cp_literal_operator_id (const char *);