Optimal Constraint-Preserving Netlist Simplification

Abstract

We consider the problem of optimal netlist simplification in the presence of constraints. Because constraints restrict the reachable states of a netlist, they may enhance logic minimization techniques such as redundant gate elimination which generally benefit from unreachability invariants. However, optimizing the logic appearing in a constraint definition may weaken its state-restriction capability, hence prior solutions have resorted to suboptimally neglecting certain valid optimization opportunities. We develop the theoretical foundation, and corresponding efficient implementation, to enable the optimal simplification of netlists with constraints. Experiments confirm that our techniques enable a significantly greater degree of redundant gate elimination than prior approaches (often greater than 2x), which has been key to the automated solution of various difficult verification problems.