Handling complexities in modern large-scale mixed-size placement

In this paper, we propose an effective algorithm flow to handle large-scale mixed-size placement. The basic idea is to use floorplanning to guide the placement of objects at the global level. The flow consists of four steps: (1) The objects in the original netlist are clustered into blocks; (2) Floorplanning is performed on the blocks; (3) The blocks are shifted within the chip region to further optimize the wirelength; (4) With big macro locations fixed, incremental placement is applied to place the remaining objects. There are several advantages of handling placement at the global level with a floorplanning technique. First, the problem size can be significantly reduced. Second, exact HPWL can be minimized. Third, precise object distribution can be achieved so that legalization only needs to handle minor overlaps among small objects in a block. Fourth, rotation and various placement constraints on macros can be handled. To demonstrate the effectiveness of this new flow, we implement a high-quality floorplan-guided placer called FLOP. We also construct the Modern Mixed-Size (MMS) placement benchmarks which can effectively represent the complexities of modern mixed-size designs and the challenges faced by modern mixed-size placers. Compared with state-of-the-art mixed-size placers and leading macro placers, experimental results show that FLOP achieves the best wirelength, and easily obtains legal solutions on all circuits.