Program conversion apparatus, processor, and record medium

A computer-readable record medium recording a program that causes a computer to perform a program conversion process for converting a source program into machine-language instructions to be executed by a processor, the processor reading out the machine-language instructions sequentially from a memory unit via a bus, the program conversion process comprising:

• a program reading step for reading, from a memory, the source program which includes a plurality of instructions, each instruction specifying an operation;
• an operation code assigning step for assigning, to each operation, two types of operation codes having different bit patterns, wherein each operation code is assigned so that a Hamming distance between (i) each of two operation codes corresponding to an operation specified by one of a pair of instructions having a frequency level, higher than a threshold value, of appearing as two successive instructions in the source program and (ii) at least one of two operation codes corresponding to an operation specified by the other of the pair of instructions is always 1;
• and
• a conversion step for converting the plurality of instructions read in the program reading step into the machine-language instructions,
• wherein the conversion step converts a portion of each instruction specifying an operation selectively into one of the two types of operation codes so that changes in logical states of signal lines composing the bus are fewest for the machine-language instructions,
• wherein each digit of each machine-language instruction resulted from the conversion in the conversion step corresponds to one of the signal lines, and
• the conversion step converts the plurality of instructions one by one and in each conversion selects either of the two types of operation codes, the conversion step including:
• a reading step for reading, for each operation specified by each instruction, two types of operation codes corresponding to an operation;
• a calculating step for calculating the number of changes in digit values in terms of corresponding digits between (i) an operation code that has been selected most recently and (ii) each of the read two types of operation codes contained in an instruction that follows an instruction having the most recently selected operation code;
• a judging step for judging which of the two types of operation codes has a smaller number of changes;
• and
• a selecting step for selecting an operation code having been judged as having the smaller number of changes, from the two types of operation codes.

In a program conversion apparatus for converting a source program into machine-language instructions to be executed by a processor, the processor reading out the machine-language instructions sequentially from a memory unit via a bus, the program conversion apparatus including:

• a program storage means for storing the source program including a plurality of instructions, each instruction specifying an operation;
• a machine-language storage means for storing a plurality of sets of two types of operation codes, each set corresponding to an operation, the two types of operation codes in each set having different bit patterns;
• and
• a conversion means for converting the plurality of instructions stored in the program storage means into the machine-language instructions, the conversion means converting a portion of each instruction specifying an operation selectively into one of the two types of operation codes so that changes in logical states of signal lines composing the bus are reduced for the machine-language instructions, the improvement to the program conversion apparatus comprising:
• the machine-language storage means being determined so that a Hamming distance between each of two operation codes corresponding to an operation specified by one of a pair of instructions having a frequency level, higher than a predetermined threshold value, of appearing as two successive instructions in the source program and at least one of two operation codes corresponding to an operation specified by the other of the pair of instructions is always 1.