1. An information processing apparatus including a processor that has at least one register and performs processing according to a machine language program, the register retaining data used in computation the information processing apparatus comprising: a compression judgment unit operable to judge whether the machine language program has information indicating that the data retained in the register should be compressed and then saved to a stack memory in response to call of a predetermined function; and a save unit operable to, when the judgment by the compression judgment unit is affirmative, compress and then save the data retained in the register to the stack memory in response to call of the predetermined function.