Apparatus and method for compiling a plurality of instruction sets for a processor and a media for recording the compiling method

An apparatus and method for compiling a source program for a processor having a plurality of different instruction sets at high speed by selecting an optimum instruction set. The compiling method comprises dividing a source program into a plurality of modules according to a predetermined unit, compiling the respective modules with respective ones of the plurality of different instruction sets, providing data for evaluating an efficient compiling process based upon the module compilations with the respective instruction sets, selecting an optimum instruction set among the plurality of different instruction sets by comparing the evaluation data, and inserting an instruction set changing command at a necessary portion for changing the instruction set.