An Effective Analytical Placement Approach to Handle Fence Region Constraint

Fence region constraints are essential in cell placement, as they can enhance design convergence speed and improve placement quality. This paper introduces a multilevel framework approach to tackle this challenge while maintaining placement quality and reducing complexity. First, the coarsening stage utilizes a fence region aware clustering to avoid inappropriate groupings. Next, recursive quadratic programming is employed to achieve a better initial cell distribution. Previous methods may result in longer wire-length because they typically assign fence objects to their placement regions before distributing cells over a placement region. To mitigate wirelength increases caused by overly restrictive constraints, our refinement stage uses a three-phase approach to gradually adjust the placement regions of fence objects. Additionally, cells are distributed across desired regions using an analytical placement formulation that includes a fence region aware penalty term. Experimental results demonstrate that our methodology achieves improved wirelength and routability while effectively managing fence region constraints.