Optimal allocation of carry-save-adders in arithmetic optimization

Abstract

Carry-save-adder(CSA) is one of the most widely used schemes for fast arithmetic in industry. This paper provides a solution to the problem of finding an optimal-timing allocation of CSAs. Specifically, we present a polynomial time algorithm which finds an optimal-timing CSA allocation for a given arithmetic expression. In addition, we extend our result for CSA allocation to the problem of optimizing arithmetic expressions across the boundary of design hierarchy by introducing a new concept, called auxiliary ports. Our algorithm can be used to carry out the CSA allocation step optimally and automatically, and this can be done within the context of a standard HDL synthesis environment.