Retiming-based timing analysis with an application to mincut-based global placement

Abstract

In this paper, we formulate the physical planning with retiming problem and propose an algorithm called GEO. Our performance-driven global placement algorithm GEO is mincut-based, where a multilevel partitioning is performed recursively to divide the netlist and assign gates to the tiles in a top-down fashion. The contribution of our work is on the development of retiming-aware timing analysis (RTA) that is used to guide our mincut-based global placement. Compared to the conventional static timing analysis, RTA provides timing slack information after retiming so that the clock period after retiming can be directly minimized during the placement. We show how to make an effective use of RTA timing slack information in a multilevel partitioning framework. Simultaneous consideration of partitioning and retiming under the geometric delay model enables GEO to hide global interconnect latency more effectively compared to the conventional approaches. In our comparison to the state-of-the art methods that perform partitioning, retiming, and simulated annealing-based floorplanning separately, GEO obtains significant improvement on retimed delay, while maintaining comparable wirelength and runtime results.