Type Interference for Java Bytecodes

Dynamic binding (dispatch) in object-oriented languages prevents compilers from performing static optimizations, such as method inlining. Type Inference, a static optimization technique, helps eliminate dynamic binding by providing compilers with receiver class type information for virtual method invocations during compile time instead of runtime. Type Inference has been implemented on SELF, a pure object-oriented language, and proven effective by inlining (statically binding) 95% of virtual method calls. It has also been tested on other object-oriented languages, and results indicate that the technique is just as effective on other languages as it is on SELF. This research evaluates the effectiveness of Type Inference on Java Bytecodes using the Cartesian Product Algorithm. The technique is applied to a bytecode-to-bytecode optimizer, which reads and parses a Java class file, perforins dataflow analysis and type inference on the bytecodes, performs optimization by eliminating virtual method invocations, and recompiles the modified bytecode into a new Java class file. Evidence resulting from this research indicates that Concrete Type Inference is an effective optimization technique for object-oriented languages, including Java. More importantly, the technique was successfully implemented and tested on Java Bytecodes. The results are not outstanding; however, some improvements are evident from the results. Further improvements should be possible by implementing other optimization techniques, such as method inlining and side-effect analysis

Using abstract interpretation to add type checking for interfaces in Java bytecode verification

AbstractJava interface types support multiple inheritance. Because of this, the standard bytecode verifier ignores them, since it is not able to model the class hierarchy as a lattice. Thus, type checks on interfaces are performed at run time. We propose a verification methodology that removes the need for run-time checks. The methodology consists of: (1) an augmented verifier that is very similar to the standard one, but is also able to check for interface types in most cases; (2) for all other cases, a set of additional simpler verifiers, each one specialized for a single interface type. We obtain these verifiers in a systematic way by using abstract interpretation techniques. Finally, we describe an implementation of the methodology and evaluate it on a large set of benchmarks

An All-in-One Debugging Approach: Java Debugging, Execution Visualization and Verification

We devise a widely applicable debugging approach to deal with the prevailing issue that bugs cannot be precisely reproduced in nondeterministic complex concurrent programs. A distinct efficient record-and-playback mechanism is designed to record all the internal states of execution including intermediate results by injecting our own bytecode, which does not affect the source code, and, through a two-step data processing mechanism, these data will be aggregated, structured and parallel processed for the purpose of replay in high fidelity while keeping the overhead at a satisfactory level. Docker and Git are employed to create a clean environment such that the execution will be undertaken repeatedly with a maximum precision of reproducing bugs. In our development, several other forefront technologies, such as MongoDB, Spark and Node.js are utilized and smoothly integrated for easy implementation. Altogether, we develop a system for Java Debugging Execution Visualization and Verification (JDevv), a debugging tool for Java although our debugging approach can apply to other languages as well. JDevv also offers an aggregated and interactive visualization for the ease of users’ code verification

A selective dynamic compiler for embedded Java virtual machine targeting ARM processors

Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2004-2005Ce travail présente une nouvelle technique de compilation dynamique sélective pour les systèmes embarqués avec processeurs ARM. Ce compilateur a été intégré dans la plateforme J2ME/CLDC (Java 2 Micro Edition for Connected Limited Device Con- figuration). L’objectif principal de notre travail est d’obtenir une machine virtuelle accélérée, légère et compacte prête pour l’exécution sur les systèmes embarqués. Cela est atteint par l’implémentation d’un compilateur dynamique sélectif pour l’architecture ARM dans la Kilo machine virtuelle de Sun (KVM). Ce compilateur est appelé Armed E-Bunny. Premièrement, on présente la plateforme Java, le Java 2 Micro Edition(J2ME) pour les systèmes embarqués et les composants de la machine virtuelle Java. Ensuite, on discute les différentes techniques d’accélération pour la machine virtuelle Java et on détaille le principe de la compilation dynamique. Enfin, on illustre l’architecture, le design (la conception), l’implémentation et les résultats expérimentaux de notre compilateur dynamique sélective Armed E-Bunny. La version modifiée de KVM a été portée sur un ordinateur de poche (PDA) et a été testée en utilisant un benchmark standard de J2ME. Les résultats expérimentaux de la performance montrent une accélération de 360 % par rapport à la dernière version de la KVM de Sun avec un espace mémoire additionnel qui n’excède pas 119 kilobytes.This work presents a new selective dynamic compilation technique targeting ARM 16/32-bit embedded system processors. This compiler is built inside the J2ME/CLDC (Java 2 Micro Edition for Connected Limited Device Configuration) platform. The primary objective of our work is to come up with an efficient, lightweight and low-footprint accelerated Java virtual machine ready to be executed on embedded machines. This is achieved by implementing a selective ARM dynamic compiler called Armed E-Bunny into Sun’s Kilobyte Virtual Machine (KVM). We first present the Java platform, Java 2 Micro Edition (J2ME) for embedded systems and Java virtual machine components. Then, we discuss the different acceleration techniques for Java virtual machine and we detail the principle of dynamic compilation. After that we illustrate the architecture, design, implementation and experimental results of our selective dynamic compiler Armed E-Bunny. The modified KVM is ported on a handheld PDA and is tested using standard J2ME benchmarks. The experimental results on its performance demonstrate that a speedup of 360% over the last version of Sun’s KVM is accomplished with a footprint overhead that does not exceed 119 kilobytes

Computing stack maps with interfaces

International audienceLightweight bytecode verification uses stack maps to annotate Java bytecode programs with type information in order to reduce the verification to type checking. This paper describes an improved bytecode analyser together with algorithms for optimizing the stack maps generated. The analyser is simplified in its treatment of base values (keeping only the necessary information to ensure memory safety) and enriched in its representation of interface types, using the Dedekind-MacNeille completion technique. The computed interface information allows to remove the dynamic checks at interface method invocations. We prove the memory safety property guaranteed by the bytecode verifier using an operational semantics whose distinguishing feature is the use of un-tagged 32-bit values. For bytecode typable without sets of types we show how to prune the fix-point to obtain a stack map that can be checked without computing with sets of interfaces i.e., lightweight verification is not made more complex or costly. Experiments on three substantial test suites show that stack maps can be computed and correctly pruned by an optimized (but incomplete) pruning algorithm