The Java language provides a promising solution to the design of safe programs, with an application spectrum ranging from Web services to operating system components. The well-known tradeoff of Java's portability is the inefficiency of its basic execution model, which relies on the interpretation of an object-based virtual machine. Many solutions have been proposed to overcome this problem, such as just-in-time (JIT) and offline bytecode compilers. However, most compilers trade efficiency for either portability or the ability to dynamically load bytecode. In this paper, we present an approach which reconciles portability and efficiency, and preserves the ability to dynamically load bytecode. We have designed and implemented an efficient environment for the execution of Java programs, named Harissa. Harissa permits the mixing of compiled and interpreted methods. Harissa's compiler translates Java bytecode to C, incorporating aggressive optimizations such as virtualmethod call optimizati...

This paper provides details of the component of the Jalape~no adaptive optimization system that determines what methods to optimize. This component, called the controller , can choose from one of several optimization levels. In the current implementation, the controller uses a simple cost/benet analysis to drive adaptive compilation decisions. It has been demonstrated that even this simple analytic model can achieve reasonable performance compared to various JIT compilation scenarios in both startup and steady-state program regimes. This paper outlines several open questions in developing a more accurate controller model. We present two experiments that study the eects of how the current model predicts future execution from the past, a limited experimental evaluation of stability of the current model across applications, and describe our ongoing eorts to improve the Jalape~no controller. 1.

To compete with optimized C, object-oriented languages need classical optimizations as well as specific object-oriented optimizations. Therefore, a compiler infrastructure that enables object-oriented compiler research isof great interest for the research community. The SUIF compiler system with the OSUIF extension offers such a research environment. SUIF defines an intermediate representation for procedural languages and offers standard optimization passes. OSUIF extends SUIF with an intermediate representation tailored towards object-oriented languages, hence allowing specific object-oriented optimizations. To enable Java-related compiler research in (O)SUIF, we have implemented j2s, a Java bytecode front end for the OSUIF/SUIF 2.0 compiler system. Our compiler uses off-line compilation, so that the whole program is known at compile time. Thus, static whole-program optimizations such as class hierarchy analysis and type inference can be implemented with (O)SUIF and applied during the compilation. j2s supports the complete Java Virtual Machine specification, except for threads and exception handling, which are currently not supported by the runtime system and (O)SUIF. Because we implemented an off-line compiler, the dynamic loading of classes is also not supported. The compiler is divided into the (O)SUIF front end and the runtime system. The main part of