1. A method of performing interconnect-driven physical synthesis, the method comprising: performing placement for a design; performing post-placement optimization based on the placement; selecting persistent nets of the design based on unpredictability and expected quality-of-result impact; generating routes for the persistent nets; extracting parasitics and delays for the persistent nets using the generated routes; performing synthesis by maintaining and updating the routes for the persistent nets across subsequent placement-based optimization steps while using the extracted parasitics and delays to drive the synthesis; performing routing for the remaining nets in the design while guaranteeing the existing routes for the persistent nets; performing optional post-routing optimization based on the routing; and outputting a final layout of the design based on the post-route optimization.