Timing-driven cell placement optimization for early slack histogram compression

As interconnects dominate circuit performance in modern chip designs, placement becomes an essential stage in optimizing timing. Recent timing-driven placement (TDP) techniques focus mainly on optimizing late slack rather than early slack. This paper presents a TDP algorithm to improve the early slack while preserving an optimized late slack. The preservation is achieved by accurately predicting optimal Steiner tree topologies after each move in our TDP algorithm. An optimality-preserving pruning scheme for each move is proposed to speed up the optimization process, without sacrificing the solution quality. Experimental results show that our algorithm can substantially improve the early slacks and the overall quality scores of the top-2 winning placers of the 2015 ICCAD Incremental Timing-Driven Placement Contest, while preserving their late slacks.