Run-time code generation is a well-known technique for improving the efficiency of programs by exploiting dynamic information. Unfortunately, the difficulty of constructing run-time code-generators has hampered their widespread use. We describe Jumbo, a tool for easily creating run-time code generators for Java. Jumbo is a compiler for a two-level version of Java, where programs can contain quoted code fragments. The Jumbo API allows the code fragments to be combined at run-time and then executed. We illustrate Jumbo with several examples that show significant speedups over similar code written in plain Java, and argue further that Jumbo is a generalized software component system.

A program executing on a low-end embedded system, such as a smart-card, faces scarce memory resources and fixed execution time constraints. We demonstrate that factorization of common instruction sequences in Java bytecode allows the memory footprint to be reduced, on average, to 85% of its original size, with a minimal execution time penalty. While preserving Java compatibility, our solution requires only a few modifications which are straightforward to implement in any JVM used in a low-end embedded system.

This paper describes Cream, an optimizer for Java bytecode using side-effect analysis to improve the optimizations. Dead-code elimination and loop-invariant removal are implemented and tested, as well as several variations of the side-effect analysis. The optimizer is tested on real-world applications such as itself and JavaSoft's Java compiler. Results show that the optimizations benefit well from the side-effect analysis. The best side-effect analysis gives five to ten times as many optimizations as without an analysis, and, in one case, makes a speed increase of 25% possible. © 1997 John Wiley & Sons, Ltd.