Abstract: To eliminate pipeline stall due to data hazard in a superscalar system and to increase the processing speed. An instruction decoder is provided with a circuit which detects two neighboring 2-operand instructions which are equivalent to one 3-operand instruction, and a circuit which, if it is equivalent, integrates the two instructions into the 3-operand instruction and sends it to a succeeding execution stage. Or, provision is made of a circuit which sends the source data of a preceding instruction to an arithmetic unit for a succeeding instruction when the two neighboring instructions have a relationship of data flow but cannot be integrated into one 3-operand instruction. It is allowed to execute the processing of two instructions in one clock, which so far required two clocks due to data flow between the neighboring instructions. Therefore, the number of execution clocks as a whole can be decreased.