-/** Exchanges two nodes by conserving edges leaving old (i.e.,
- pointers pointing to old). Turns the old node into an Id. */
-void exchange(ir_node *old, ir_node *nw);
+/**
+ * Exchanges two nodes by conserving edges leaving old (i.e.,
+ * pointers pointing to old).
+ * The nodes op will be changed to op_Deleted and you must not do anything with
+ * the node anymore except testing its op.
+ */
+FIRM_API void exchange(ir_node *old, ir_node *nw);