It is determined that a write access is executed to a stack area of a main memory. It is then determined whether another write access to a corresponding access destination address in the stack area occurred in the past by referring to an access flag table. In contrast, it is determined that a write access is executed to a global area of the main memory. It is then determined whether another write access to a corresponding access destination address in the global area occurred in the past with referring to an access list. Such a configuration can efficiently provide individual advantages of the determination methods using both the access flag table and the address list. The presence or absence of the past saving execution can be efficiently determined at the time of write access.