Context - Insensitive Alias Analysis

part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for proot or commercial advantage and that copies bear this notice and the full citation on the rst page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, to republish, to post on servers, or to redistribute to lists, requires prior speciic permission and/or a fee. Request permissions from Publications Dept, ACM Inc., fax + 1 (212) 869-0481, or [email protected]. Abstract Recent work on alias analysis in the presence of pointers has concentrated on context-sensitive interprocedural analyses , which treat multiple calls to a single procedure independently rather than constructing a single approximation to a procedure's eeect on all of its callers. While context-sensitive modeling ooers the potential for greater precision by considering only realizable call-return paths, its empirical beneets have yet to be measured. This paper compares the precision of a simple, eecient, context-insensitive points-to analysis for the C programming language with that of a maximally context-sensitive version of the same analysis. We demonstrate that, for a number of pointer-intensive benchmark programs, context-insensitivity exerts little to no precision penalty. We also describe techniques for using the output of context-insensitive analysis to improve the eeciency of context-sensitive analysis without aaecting precision. 1 Introduction Modern compilers and programming environments are becoming increasingly dependent on semantic information extracted via dataaow analysis. In programs containing pointers , many dataaow analyses depend crucially on the ability to approximate the targets of indirect memory operations, so that all potential uses or modiications of a value can be taken into account. Alias analysis 1 provides this approximation ; its precision directly eeects the quality of virtually all other dataaow analyses. Early pointer alias analyses were completely ow-insensitive; both Weihl Wei80] and Coutant Cou86] computed alias information on a program-wide basis, building a single, global mapping between pointers and their potential referents. Others later found that these methods generated overly large, imprecise approximations, handicapping subsequent analyses Ryd89, LR92].