A schema for interprocedural modification side-effect analysis with pointer aliasing

Abstract

The first interprocedural modification side-effects analysis for C (MOD _C ) that obtains better than worst-case precision on programs with general-purpose pointer usage is presented with empirical results. The analysis consists of an algorithm schema corresponding to a family of MOD _C algorithms with two independent phases: one for determining pointer-induced aliases and a subsequent one for propagating interprocedural side effects. These MOD _C algorithms are parameterized by the aliasing method used. The empirical results compare the performance of two dissimilar MOD _C algorithms: MOD _C ( FSAlias ) uses a flow-sensitive, calling-context-sensitive interprocedural alias analysis; MOD _C ( FIAlias uses a flow-insensitive, calling-context-insensitive alias analysis which is much faster, but less accurate. These two algorithms were profiled on 45 programs ranging in size from 250 to 30,000 lines of C code, and the results demonstrate dramatically the possible cost-precision trade-offs. This first comparative implementation of MOD _C analyses offers insight into the differences between flow-/context-sensitive and flow-/context-insensitive analyses. The analysis cost versus precision trade-offs in side-effect information obtained are reported. The results show surprisingly that the precision of flow-sensitive side-effect analysis is not always prohibitive in cost, and that the precision of flow-insensitive analysis is substantially better than worst-case estimates and seems sufficient for certain applications. On average MOD _C ( FSAlias ) for procedures and calls is in the range of 20% more precise than MOD _C ( FIAlias ); however, the performance was found to be at least an order of magnitude slower than MOD _C ( FIAlias ).