+tp_op *get_tpop_id(void);
+
+/**
+ * This type opcode is an auxiliary opcode dedicated to support type analyses.
+ *
+ * Types with this opcode represents that there is no type.
+ * The type can be used to initialize fields of the type* that actually can not
+ * contain a type or that are initialized for an analysis. There exists exactly
+ * one type with this opcode.
+ */
+extern tp_op *tpop_none;
+tp_op *get_tpop_none(void);
+
+/**
+ * This type opcode is an auxiliary opcode dedicated to support type analyses.
+ *
+ * Types with this opcode represents that there could be a type, but it is not
+ * known. This type can be used to initialize fields before an analysis (not known
+ * yet) or to represent the top of a lattice (could not be determined). There exists
+ * exactly one type with this opcode.
+ */
+extern tp_op *tpop_unknown;
+tp_op *get_tpop_unknown(void);