A Methodology and Algorithms for Post-Placement Delay Optimization

In this paper we present a placement-intelligent resynthesis methodology and optimization algorithms to meet post-layout timing constraints while at the same time reducing the interconnect congestion. We begin with the synthesized design netlist after initial placement and make incremental modifications - taking placement into account - to generate a final netlist and placement that meets the delay constraints after place and route. The algorithms described have been implemented as part of a tool for placement based resynthesis. The tool has been used with a number of pre-optimized designs from industry and to obtain improvements in post-placement delays ranging from 13 to 22% with improved routability.