HybridGP: Global Placement for Hybrid-Row-Height Designs

Conventional global placement algorithms typically assume that all cell rows in a design have the same height. Nevertheless, a design making use of standard cells with short-row height, tall-row height, and double-row (short plus tall) height can provide a better sweet spot for performance and area co-optimization in advanced nodes. In this paper, we assume for a hybrid-row-height design, its placement region is composed of both tall rows and short rows, and a cell library containing multiple versions of each cell in the design is provided. We present a new analytical global placer, HybridGP, for such hybrid-row-height designs. Furthermore, we assume that a subset of cells with sufficient timing slacks is given so that we may change their versions without overall timing degradation if desired. Our approach considers the usage of short-row and tall-row resources and exploits the flexibility of cell version change to facilitate the subsequent legalization stage. Augmented with an identical legalizer for final placement legalization, we compared HybridGP with a conventional global placer. The experimental results show that legalized placement solutions of much better quality can be obtained in less run time with HybridGP.