Matching Multiplications in Bit-Vector Formulas

Abstract

Bit-vector formulas arising from hardware verification problems often contain word-level arithmetic operations. Empirical evidence shows that state-of-the-art SMT solvers are not very efficient at reasoning about bit-vector formulas with multiplication. This is particularly true when multiplication operators are decomposed and represented in alternative ways in the formula. We present a pre-processing heuristic that identifies certain types of decomposed multipliers, and adds special assertions to the input formula that encode the equivalence of sub-terms and word-level multiplication terms. The pre-processed formulas are then solved using an SMT solver. Our experiments with three SMT solvers show that our heuristic allows several formulas to be solved quickly, while the same formulas time out without the pre-processing step.