Incremental 3-D Global Routing Considering Cell Movement and Complex Routing Constraints

Abstract

Placement and routing are two critical problems in VLSI physical design. However, there may be out-of-sync between the two problems considering congestion and wirelength. Therefore, it is desirable to design an efficient and highly coupled placement and routing engine to narrow the gap and minimize the mismatch between placement and routing. This paper proposes an incremental 3D global routing engine considering cell movement and complex routing constraints to relocate cells and reroute nets. We first apply a queue-based congestion-aware 3D maze routing with routing height restriction to improve the initial routing solution. Efficient multi-net-based location estimation is then presented to find the best location for each cell in multiple cell movement rounds. In each step of cell movement, we reroute nets for all candidate cell locations in parallel using a guided stack-based 3D routing algorithm while considering the routing constraints. Finally, we adopt an edge-adjusting technique to improve the routed wirelength further. Compared with the champion of the 2020 CAD Contest at ICCAD hu2020iccad and the state-of-the-art works, experiment results based on the contest benchmarks show that our proposed algorithm achieves the best routing wirelength and competitive runtime without maximum cell movement constraint.