Evolving Machine Microprograms: Application to the CODE2 Microarchitecture

The realization of a control unit can be done either using a complex circuitry or microprogramming. The latter may be considered as an alternative method of implementation of machine instructions that can reduce the complexity and increase the flexibility of the control unit. Microcode efficiency and speed are of vital importance for the computer to execute machine instructions fast. This is a difficult task and it requires expert knowledge. It would be interesting and helpful to have automated tools that, given a machine instruction description, could generate an efficient and correct microprogram. A good option is to use evolutionary computation techniques, which have been proved effective in the evolution of computer programs. We have developed a microarchitecture simulator of a real machine in order to evaluate every individual and to assign it a fitness value (to determine whether this candidate solution correctly implements the instruction machine). Proposed method is successful in generating correct solutions, not only for the machine code instruction set, but also for new machine instructions not included in such set. We show that our approach can generate microprogramms to execute (to schedule microinstructions) the machine level instructions for a real machine. Moreover this evolutive method could be applied to any microarchitecture just by changing the microinstruction set and pre-conditions of each machine instruction to guide evolution.