Density-aware Detailed Placement with Instant Legalization

Placement consists of three stages: global placement, legalization, and detailed placement (DP). Recently, most research works have concentrated on improving global placement and legalization, but innovations in DP have been rarely seen. ICCAD13 held a DP contest that formulates the emerging placement issues into a bin-utilization metric and maximum cell displacement constraint. This paper presents a detailed placer that can effectively reduce both half-perimeter wirelength and the peak bin-utilization under the displacement constraint. The proposed lazy-update based incremental density profit function supports efficient cell swapping. Combination of lazy-update density profit function and Density-Driven Swap lets our placer achieve AOFP of 0 for the majority of the ICCAD13 test cases. The placer presented produces the best placement results among the top3 teams in the ICCAD13 contest.