RippleFPGA: Routability-Driven Simultaneous Packing and Placement for Modern FPGAs

As a good tradeoff between central processing unit (CPU) and application specific integrated circuit (ASIC), field-programmable gate array (FPGA) is becoming more widely used in both industry and academia. The increasing complexity and scale of modern FPGA, however, impose great challenges on the FPGA placement and packing problem. In this paper, we propose RippleFPGA to solve the packing and placement simultaneously through a set of novel techniques: 1) smooth stair-step flow; 2) implicit packing similar to ASIC legalization (LG); and 3) two-level detailed placement (DP). To enable the flow, a generic, efficient, and false-alarm-free legality checking method is also proposed. Besides, due to the insufficiency of ASIC-like congestion alleviation methods, some FPGA-routing-architecture-aware optimization techniques are proposed to improve the routability. When evaluated by ISPD 2016 Contest benchmarks, RippleFPGA has 5.1% better routed wirelength and 5.5× speedup compared to all the state-of-the-art FPGA placers.