A SimPLR method for routability-driven placement

Abstract

Highly-optimized placements may lead to irreparable routing congestion due to inadequate models of modern interconnect stacks and the impact of partial routing obstacles. Additional challenges in routability-driven placement include scalability to large netlists and limiting the complexity of software integration. Addressing these challenges, we develop lookahead routing to give the placer advance, firsthand knowledge of trouble spots, not distorted by crude congestion models. We also extend global placement to (i) spread cells apart in congested areas, and (ii) move cells together in less-congested areas to ensure short, routable interconnects and moderate runtime. While previous work adds isolated steps to global placement, our SIMultaneous PLace-and-Route tool SimPLR integrates a layer- and via-aware global router into a leading-edge, force-directed placer. The complexity of integration is mitigated by careful design of simple yet effective optimizations. On the ISPD 2011 Contest Benchmark Suite, with the official evaluation protocol, SimPLR outperforms every contestant on every benchmark.