Slack budgeting and slack to length converting for multi-bit flip-flop merging

Abstract

In this paper we propose a flexible slack budgeting approach for post-placement multi-bit flip-flop (MBFF) merging. Our approach considers existing wiring topology and flip-flop delay changes for achieving more accurate slack budgeting. Besides, we propose a slack-to-length converting approach to translating timing slack into equivalent wire length for simplifying a merging process. We also develop a merging method to evaluate our slack budgeting approach. Our slack budgeting and MBFF merging programs are fully integrated into an industrial design flow. Experimental results show that our approach on average achieves 3.4% area saving, 50% clock tree power saving, and 5.3% total power saving.