Mixed-cell-height legalization considering technology and region constraints

Mixed-cell-height circuits have become popular in advanced technologies for better power, area, routability, and performance trade-offs. With the technology and region constraints imposed by modern circuit designs, the mixed-cell-height legalization problem has become more challenging. In this paper, we present an effective and efficient legalization algorithm for mixed-cell-height circuit designs with technology and region constraints. We first present a fence region handling technique to unify the fence regions and the default ones. To obtain a desired cell assignment, we then propose a movement-aware cell reassignment method by iteratively reassigning cells in locally dense areas to their desired rows. After cell reassignment, a technology-aware legalization is presented to remove cell overlaps while satisfying the technology constraints. Finally, we propose a technology-aware refinement to further reduce the average and maximum cell movements without increasing the technology constraints violations. Compared with the champion of the 2017 ICCAD CAD Contest and the state-of-the-art work, experimental results show that our algorithm achieves the best average and maximum cell movements and significantly fewer technology constraint violations, in a comparable runtime.