Transformation-based verification using generalized retiming

Abstract

In this paper we present the application of generalized retiming for temporal property checking. Retiming is a structural transformation that relocates registers in a circuit-based design representation without changing its actual input-output behavior. We discuss the application of retiming to minimize the number of registers with the goal of increasing the capacity of symbolic state traversal. In particular, we demonstrate that the classical definition of retiming can be generalized for verification by relaxing the notion of design equivalence and physical implementability. This includes (1) omitting the need for equivalent reset states by using an initialization stump, (2) supporting negative registers, handled by a general functional relation to future time frames, and (3) eliminating peripheral registers by converting them into simple temporal offsets. The presented results demonstrate that the application of retiming in verification can significantly increase the capacity of symbolic state traversal. Our experiments also demonstrate that the repeated use of retiming interleaved with other structural simplifications can yield reductions beyond those possible with single applications of the individual approaches. This result suggests that a tool architecture based on re-entrant transformation engines can potentially decompose and solve verification problems that otherwise would be infeasible.