Voltage island aware incremental floorplanning algorithm based on MILP formulation

Multiple supply voltages (MSV) is a widely-used technology in low power VLSI designs. In MSV design, the voltage island is a crucial concern that the blocks with the same voltage level are clustered into one or more voltage islands to reduce the cost of voltage supply network and level converter. In traditional MSV design approaches, the high level synthesis and physical exploring iterate with each other to achieve the convergence. During the iteration process, some incremental changes on voltage assignment are requested by re-synthesis processes so that the packing results need to be changed accordingly. In this paper, we propose a voltage island aware incremental floorplanning approach to handle the incremental requests. Instead of randomly exploring the packing solution spaces to cope with the required modifications, our algorithm can predict the area and wire length cost of incremental floorplanning efficiently and then move the block with voltage reassigned to the desired voltage island using MILP-based approach. During the incremental floorplanning, the chip area and the wire length are optimized simultaneously, and the performance would not be compromised. The experimental results show our algorithm is promising. To the best of our knowledge, this algorithm is the first incremental floorplanning algorithm that can handle the voltage island constraints.