Superinstructions and Replication in the Cacao JVM interpreter

M. Anton Ertl and Christian Thalinger and Andreas Krall

Institut für Computersprachen
Technische Universität Wien
Argentinierstraße 8
A-1040 Wien, Austria



Dynamic superinstructions and replication can provide large speedups over plain interpretation. In a JVM implementation we have to overcome two problems to realize the full potential of these optimizations: the conflict between superinstructions and the quickening optimization; and the non-relocatability of JVM instructions that can throw exceptions. In this paper, we present solutions for these problems. We also present empirical results: We see speedups of up to a factor of 4 on SpecJVM98 benchmarks from superinstructions with all these problems solved. The contribution of making potentially throwing JVM instructions relocatable is up to a factor of 2. A simple way of dealing with quickening instructions is good enough, if superinstructions are generated in JIT style. Replication has little effect on performance.