Routability-driven Mixed-size Placement Prototyping Approach Considering Design Hierarchy and Indirect Connectivity Between Macros

Abstract

The mixed-size placement becomes a great challenge in the modern VLSI design. To handle this problem, the three-stage mixed-size placement methodology is considered as the most suitable approach for a commercial design flow, where the placement prototyping is the most important stage. Since standard cells and macros have to be considered simultaneously in this stage, it is more complicated than the other two stages. To reduce complexity and improve design quality, this paper applies the multilevel framework with a design hierarchy-guided clustering scheme for getting a better coarsening result in order to improve outcome in the following stages. We propose an efficient and effective clustering scheme to group standard cells and macros based on the tree built from their design hierarchies. More importantly, our clustering algorithm considers indirect connectivity between macros which is ignored by previous works. Moreover, we propose a new overlapping bounding box constraint to avoid clustering improper macros which have connections to fixed pins. The experimental results show that wirelength and routability are improved by our methodology.