Addressing the timing closure problem by integrating logic optimization and placement

Abstract

Timing closure problems occur when timing estimates computed during logic synthesis do not match with timing estimates computed from the layout of the circuit. In such a situation, logic synthesis and layout synthesis are iterated until the estimates match. The number of such iterations is becoming larger as technology scales. Timing closure problems occur mainly due to the difficulty in accurately predicting interconnect delay during logic synthesis. In this paper, we present an algorithm that integrates logic synthesis and global placement to address the timing closure problem. We introduce technology independent algorithms as well as technology dependent algorithms. Our technology independent algorithms are based on the notion of "wire-planning". All these algorithms interleave their logic operations with local and incremental/full global placement, in order to maintain a consistent placement while the algorithm is run. We show that by integrating logic synthesis and placement, we avoid the need to predict interconnect delay during logic synthesis. We demonstrate that our scheme significantly enhances the predictability of wire delays, thereby solving the timing closure problem. This is the main result of our paper. Our results also show that our algorithms result in a significant reduction in total circuit delay. In addition, our technology independent algorithms result in a significant circuit area reduction.