Harissa: A flexible and efficient Java']Java environment mixing bytecode and compiled code

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(1) Harissa permits the mixing of compiled and interpreted methods. Harissa's compiler translates Java bytecode to C, incorporating aggressive optimizations such as virtual-method call optimization based on the Class Hierarchy Analysis. To evaluate the performance of Harissa, we have conducted an extensive experimental study aimed at comparing the various existing alternatives to execute Java programs. The C code produced by Harissa's compiler is more efficient than all other alternative ways of executing Java programs (that were available to us): it is up to 140 times faster than the JDK interpreter, up to 13 times faster than the Softway Guava JIT, and 30% faster than the Toba bytecode to C compiler.