Catálogo de publicaciones - libros

We introduce a new approach, called completeness analysis, to computing points-to sets for incomplete Java programs such as library modules or applications in the presence of dynamic class loading. One distinctive feature of this work is that the access and modification properties of fields are taken into account. By combining with a whole-program points-to analysis, completeness analysis yields not only the required points-to sets but also determines which points-to sets and call sites are complete (when the pointed-to objects and target methods are statically resolvable) or not. Such a compositional approach yields more precise points-to sets than those computed by the points-to analysis alone. In addition, our technique also determines (for the first time) which objects may be incompletely detectable, i.e., may be missing in some statically computed points-to sets. We provide experimental evidence to demonstrate that better analysis precision in benchmarks is obtained when the field access and modification properties are exploited. In particular, we are able to find significantly more complete and mono call sites in an incomplete program, which is useful in devirtualisation and inlining. Our analysis is simple since it is flow- and context-insensitive and achieves these improvements at reasonably small analysis costs.

Inter-procedural analyses such as side-effect analysis can provide information useful for performing aggressive optimizations. We present a study of whether side-effect information improves performance in just-in-time (JIT) compilers, and if so, what level of analysis precision is needed.

We used , the inter-procedural analysis component of the Java analysis and optimization framework, to compute side-effect information and encode it in class files. We modified Jikes RVM, a research JIT, to make use of side-effect analysis in local common sub-expression elimination, heap SSA, redundant load elimination and loop-invariant code motion. On the SpecJVM98 benchmarks, we measured the static number of memory operations removed, the dynamic counts of memory reads eliminated, and the execution time.

Our results show that the use of side-effect analysis increases the number of static opportunities for load elimination by up to 98%, and reduces dynamic field read instructions by up to 27%. Side-effect information enabled speedups in the range of 1.08x to 1.20x for some benchmarks. Finally, among the different levels of precision of side-effect information, a simple side-effect analysis is usually sufficient to obtain most of these speedups.