Beaver: Engineering an Efficient SMT Solver for Bit-Vector Arithmetic

We present the key ideas in the design and implementation of Beaver, an SMT solver for quantifierfree finite-precision bit-vector logic (QF BV). Beaver uses an eager approach, encoding the original SMT problem into a Boolean satisfiability (SAT) problem using a series of word-level and bit-level transformations. In this paper, we describe the most effective transformations, such as propagating constants and equalities at the word-level, and using and-inverter graph rewriting techniques at the bit-level. We highlight the implementation details of these transformations that distinguishes Beaver from other solvers. We present an experimental evaluation and analysis of the effectiveness of Beaver’s techniques on both hardware and software benchmarks with a selection of back-end SAT solvers. Beaver is an open-source tool implemented in Ocaml, usable with any back-end SAT engine, and has a well-documented extensible code base that can be used to experiment with new algorithms and techniques.