AIR: A Fast but Lazy Timing-Driven FPGA Router

Routing is a key step in the FPGA design process, which significantly impacts design implementation quality. Routing is also very time-consuming, and can scale poorly to very large designs. This paper describes the Adaptive Incremental Router (AIR), a high-performance timing-driven FPGA router. AIR dynamically adapts to the routing problem, which it solves `lazily' to minimize work. Compared to the widely used VPR 7 router, AIR significantly reduces route-time ($7.1 \times$ faster), while also improving quality (15% wirelength, and 18% critical path delay reductions). We also show how these techniques enable efficient incremental improvement of existing routing.