1. An information processing system, comprising: a program storage unit in which a program that is to be executed is stored; at least two processors, each of which executes at least one instruction; an executability information storage unit in which executability information, which includes information specifying, for each instruction of a plurality of instructions necessary to execute the program, whether the respective instruction is executable or not executable by each of the at least two processors, is stored for each of the at least two processors; and a control unit that, at the time of execution of the program, selects at least one processor from among the at least two processors for execution of at least one instruction of the plurality of instructions necessary to execute the program, with reference to the executability information stored in the executability information storage unit, and causes the selected at least one processor to execute the at least one instruction.