Abstract: The present invention enables re-ordering of instructions to be executed while assuring a precise exception. In Java language, an optimization process of re-ordering instructions to be executed is performed by Just-In-Time compiler. For instance, the instructions lining in order from instruction E1 which was moved forward to instruction S2which had been located before E1 is registered as interrupt inhibited section R1, and from instruction S4 which was moved forward to instruction S3 which had been located before S4 is registered as interrupt inhibited section R2 (S is an instruction which has an affect observable from the outside at the execution, and E is an instruction which may cause an exception). Also, in FIG. 7, S4 which was an instruction behind E1 in the original order is registered as R1's instruction invalid at an exception. If E1 causes an exception, an interrupt handler is activated and the instructions of interrupt inhibited section R1 are copied to another area.