Binding Refinement for Multiplexer Reduction

In behavioral synthesis for resource shared architecture, multiplexers are inserted between registers and functional units as a result of binding if necessary. Multiplexer optimization in binding is important for performance, area and power of a synthesized circuit. In this paper, we propose a binding algorithm to reduce total amount of multiplexer ports. Unlike most of the previous works in which binding is performed by a constructive algorithm, our approach is based on an iterative improvement algorithm. Starting point of our approach is initial functional unit binding and initial register binding. Both functional unit binding and register binding are modified by local improvements based on taboo search iteratively. The binding in each iteration is feasible, hence actual value of total amount of multiplexer ports can be optimized. The smart neighborhood which considers an effect of sharing of connection is used in the proposed method for effective reduction of total amount of multiplexer ports. Additionally, the massive modification of binding is performed by regular intervals to achieve a further reduction of total amount of multiplexer ports and further robustness for an initial binding. Experimental results show that our approach can reduce total amount of multiplexer ports by 30% on an average compared to a traditional binding algorithm with computation time of several seconds to a few minutes. Also, results of robustness evaluation show that our approach barely depends on initial binding.