Retiming-based factorization for sequential logic optimization

Abstract

Current sequential optimization techniques apply a variety of logic transformations that mainly target the combinational logic component of the circuit. Retiming is typically applied as a postprocessing step to the gate-level implementation obtained after technology mapping. This paper introduces a new sequential logic transformation which integrates retiming with logic transformations at the technology-independent level. This transformation is based on implicit retiming across logic blocks and fanout stems during logic optimization. Its application to sequential network synthesis results in the optimization of logic across register boundaries. It can be used in conjunction with any measure of circuit quality for which a fast and reliable gain estimation method can be obtained. We immplemented our new technique within the SIS framework and demonstrated its effectiveness in terms of cycle-time minimization on a set sequential benchmark circuits.