Design Optimization by Fine-grained Interleaving of Local Netlist Transformations in Lagrangian Relaxation

Design optimization modifies a netlist with the goal of satisfying the timing constraints at the minimum area and leakage power, without violating any slew or load capacitance constraints. Lagrangian relaxation (LR) based optimization has been established as a viable approach for this. We extend LR-based optimization by interleaving in each iteration techniques such as: gate and flip-flop sizing; buffering to fix late and early timing violations; pin swapping; and useful clock skew. Locally optimal decisions are made using LR-based cost functions, without the need for incremental timing updates. Sub-steps are applied in a balanced manner, accounting for the expected savings and any conflicting timing violations, maximizing the final quality of results under multiple process/operating corners with a reasonable runtime. Experimental results show that our approach achieves better timing, and both lower area and leakage power than the winner of the TAU 2019 contest, on those benchmarks.