Boolean algebra of shape analysis constraints

Abstract

The parametric shape analysis framework of Sagiv, Reps, and Wilhelm [45, 46] uses three-valued structures as dataflow lattice elements to represent sets of states at different program points. The recent work of Yorsh, Reps, Sagiv, Wilhelm [48, 50] introduces a family of formulas in (classical, two-valued) logic that are isomorphic to three-valued structures [46] and represent the same sets of concrete states. In this paper we introduce a larger syntactic class of formulas that has the same expressive power as the formulas in [48]. The formulas in [48] can be viewed as a normal form of the formulas in our syntactic class; we give an algorithm for transforming our formulas to this normal form. Our formulas make it obvious that the constraints are closed under all boolean operations and therefore form a boolean algebra. Our algorithm also gives a reduction of the entailment and the equivalence problems for these constraints to the satisfiability problem.