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arXiv · 2512.04527

FLEX: Leveraging FPGA-CPU Synergy for Mixed-Cell-Height Legalization Acceleration

Xingyu Liu·Jiawei Liang·Linfeng Du·Yipu Zhang·Chaofang Ma·Hanwei Fan·Jiang Xu·Wei Zhang
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Abstract

In this work, we present FLEX, an FPGA-CPU accelerator for mixed-cell-height legalization tasks. We address challenges from the following perspectives. First, we optimize the task assignment strategy and perform an efficient task partition between FPGA and CPU to exploit their complementary strengths. Second, a multi-granularity pipelining technique is employed to accelerate the most time-consuming step, finding optimal placement position (FOP), in legalization. At last, we particularly target the computationally intensive cell shifting process in FOP, optimizing the design to align it seamlessly with the multi-granularity pipelining framework for further speedup. Experimental results show that FLEX achieves up to 18.3x and 5.4x speedups compared to state-of-the-art CPU-GPU and multi-threaded CPU legalizers with better scalability, while improving legalization quality by 4% and 1%.

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Xingyu Liu, Jiawei Liang, Linfeng Du, Yipu Zhang, Chaofang Ma, Hanwei Fan, Jiang Xu, Wei Zhang. 2025-12-04. FLEX: Leveraging FPGA-CPU Synergy for Mixed-Cell-Height Legalization Acceleration. https://arxiv.org/abs/2512.04527

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