Data-flow analysis of program fragments

Abstract

Traditional interprocedural data-flow analysis is performed on whole programs; however, such whole-program analysis is not feasible for large or incomplete programs. We propose fragment data-flow analysis as an alternative approach which computes data-flow information for a specific program fragment. The analysis is parameterized by the additional information available about the rest of the program. We describe two frameworks for interprocedural flow-sensitive fragment analysis, the relationship between fragment analysis and whole-program analysis, and the requirements ensuring fragment analysis safety and feasibility. We propose an application of fragment analysis as a second analysis phase after an inexpensive flow-insensitive whole-program analysis, in order to obtain better information for important program fragments. We also describe the design of two fragment analyses derived from an already existing whole-program flow- and context-sensitive pointer alias analysis for C programs and present empirical evaluation of their cost and precision. Our experiments show evidence of dramatically better precision obtainable at a practical cost.