Precise Data Flow Analysis in the Presence of Correlated Method Calls

When two methods are invoked on the same object, the dispatch behaviours of these method calls will be correlated. If two correlated method calls are polymorphic (i.e., they dispatch to different method definitions depending on the type of the receiver object), a program’s interprocedural control flow graph will contain infeasible paths. Existing algorithms for data-flow analysis are unable to ignore such infeasible paths, giving rise to loss of precision. We show how infeasible paths due to correlated calls can be eliminated for Interprocedural Finite Distributive Subset (IFDS) problems, a large class of data-flow analysis problems with broad applications. Our approach is to transform an IFDS problem into an Interprocedural Distributive Environment (IDE) problem, in which edge functions filter out data flow along infeasible paths. A solution to this IDE problem can be mapped back to the solution space of the original IFDS problem. We formalize the approach, prove it correct, and report on an implementation in the WALA analysis framework.