Program optimization by converting code portions to directly reference internal data representations

A non-transitory computer readable storage medium collectively storing program instructions that are executable by a computer to cause the computer to perform operations comprising:

• identifying a code portion that accesses a primitive value in a user-defined function included in a user program, the user-defined function including an object as an argument;
• converting the code portion and the argument to directly reference an internal data representation;
• and
• generating a code for calling the user-defined function converted by the conversion, the code including a pointer indicating an address of a memory region directly accessing the primitive value where the object manages the internal data representation.