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While dynamic method calls are sources of reusability and extensibility in object-oriented languages, they have long been targets of optimizations because they incur runtime overhead and prevent classical compiler optimizations, resulting in many techniques to devirtualize the calls having been proposed. However, these techniques are less effective in Java since either Java is a statically-typed language, or not straightforwardly applicable since Java's capability of loading classes dynamically prevents whole program optimizations. This paper proposes a direct devirtualization technique with a code patching mechanism. This technique has lower overhead than a well-known recompilation approach. We have implemented a number of devirtualization techniques. This paper presents detailed characteristics and effectiveness as applied them to 16 real programs. We show reductions in the number of dynamic method calls ranging from 8.9% to 97.3% (an average of 40.4%). It conducts some interesting observations of program characteristics and potential performance problems. We also report performance improvements from -1% to 122% (an average of 19%).
By: Kazuaki Ishizaki, Motohiro Kawahito, Toshiaki Yasue, Hideaki Komatsu, Toshio Nakatani
Published in: ACM SIGPLAN Notices, volume 35, (no 10), pages 294-310 in 2000
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