Abstract: Each entry of an instruction out-of-order buffer 330 has a Y-operand referencing succeeding-entry information field 335 and a Z-operand referencing succeeding-entry information field 336. In the field 335, the entry number of a succeeding instruction that will reference the execution result of the instruction in the entry as the Y operand is stored. In the field 336, the entry number of a succeeding instruction that will reference the execution result of the instruction in the entry as the Z operand is stored. When the succeeding instruction is stored in the instruction out-of-order buffer 330, a reference relation setting circuit 320 sets the reference relation between the execution result of a preceding instruction and the operands of the succeeding instruction in the operand referencing succeeding-entry information fields of the preceding instruction. A ready flag setting circuit 340 reflects the fields 335 and 336 on ready flags 333 and 334 of the Y-operand and the Z-operand of the corresponding entry.