POLAR: A High Performance Mixed-Size Wirelengh-Driven Placer With Density Constraints

Abstract

Wirelength is one of the most important metrics in the placement problem. Minimizing wirelength is not only beneficial, but also a fundamental step to optimize other metrics, such as timing, power, and routability. In this paper, we propose a high performance mixed-size wirelengh-driven placer called POLAR. POLAR is based on the recent popular look-ahead legalization idea. The goals of our look-ahead legalization are: 1) to achieve a roughly legalized placement and 2) to maintain cells' relative positions of quadratic placement while minimizing cell movements. To achieve these goals, in POLAR, look-ahead legalization is realized in a simple and elegant manner. Firstly, all placement density hotspots (where placement overflow occurs) are detected. Secondly, for each hotspot, an appropriate window is searched to cover it by enumerating many feasible candidates. Finally, cell-to-bin assignment is performed within each window by a fast recursive bisection method. The experimental results verify the efficiency of POLAR over the ISPD 2005 and 2006 benchmarks.