Compatible class encoding in hyper-function decomposition for FPGA synthesis

Recently, functional decomposition has been adopted for LUT based FPGA technology mapping with good results. In this paper, we propose a novel method for functional multiple-output decomposition. We first address a compatible class encoding method to minimize the compatible classes in the image function. After the encoding algorithm is applied, the decomposability will be improved in the subsequent decomposition of the image function. The above encoding algorithm is then extended to encode multiple-output functions through the construction of a hyper-function. Common sub-expressions among these multiple-output functions can be extracted during the decomposition of the hyper-function. Therefore, we can handle the multiple-output decomposition in the same manner as the single-output decomposition. Experimental results show that our algorithms are very promising.