A new horizontal and vertical common subexpression elimination method for multiple constant multiplication

The common subexpression elimination (CSE) techniques address the issue of minimizing the number of adders needed to implement the multiple constant multiplication (MCM) blocks. In this paper, we propose a new CSE method using a combining horizontal and vertical technique. The proposed method searches firstly the frequency of higher order horizontal common subexpression, i.e., 3-5 bits, and then searches vertical. Our simulation results show that our method offers a good tradeoff between the implementation cost and the synthesis run-time in comparison with conventional methods.