Standard Cells Do Matter: Uncovering Hidden Connections for High-Quality Macro Placement

It becomes increasingly critical for an intelligent macro placer to be able to uncover a good dataflow for a large-scale chip to reduce churns from manual trials and errors. Existing macro placers or mixed-size placement engines that were equipped with dataflow awareness mostly focused on extracting intrinsic relations among macros only, ignoring the fact that standard cell clusters play an essential role in determining the location of macros. In this paper, we identify the necessity of macro-cell connection awareness for high-quality macro placement and propose a novel methodology to extract all “hidden” relationships efficiently among macros and cell clusters. By integrating the discovered connections as part of the placement constraints, the proposed methodology achieves an average of 2.8% and 5.5% half perimeter wire length (HPWL) improvement for considering one-hop macro-cell and two-hop macro-cell-cell dataflow connections respectively, when compared against a recently proposed dataflow-aware macro placer. A maximum of 9.7% HPWL improvement has been achieved, incurring only less than 1% runtime penalty. In addition, the congestion has been improved significantly by the proposed method, yielding an average of 62.9% and 73.4% overflow reduction for one-hop and two-hop dataflow considerations. The proposed dataflow connection extraction methodology has been demonstrated to be a significant starting point for macro placement and can be integrated into the existing design flows while delivering better design quality.