A Robust Global Routing Engine with High-accuracy Cell Movement under Advanced Constraints

Abstract

Placement and routing are typically defined as two separate problems to reduce the design complexity. However, such a divide-and-conquer approach inevitably incurs the degradation of solution quality due to the correlation/objectives of placement and routing are not entirely consistent. Besides, with various constraints (e.g., timing, R/C characteristic, voltage area, etc.) imposed by advanced circuit designs, bridging the gap between placement and routing while satisfying the advanced constraints has become more challenging. In this paper, we develop a robust global routing engine with high-accuracy cell movement under advanced constraints to narrow the gap and improve the routing solution. We first present a routing refinement technique to obtain the convergent routing result based on fixed placement, which provides more accurate information for subsequent cell movement. To achieve fast and high-accuracy position prediction for cell movement, we construct a lookup table (LUT) considering complex constraints/objectives (e.g., routing direction and layer-based power consumption), and generate a timing-driven gain map for each cell based on the LUT. Finally, based on the prediction, we propose an alternating cell movement and cluster movement scheme followed by partial rip-up and reroute to optimize the routing solution. Experimental results on the ICCAD 2020 contest benchmarks show that our algorithm achieves the best total scores among all published works. Compared with the champion of the ICCAD 2021 contest, experimental results on the ICCAD 2021 contest benchmarks show that our algorithm achieves better solution quality in shorter runtime.