Enabling constant-time interface method dispatch in embedded Java processors

Abstract

This paper describes an approach that enables the fast constant-time and memory-efficient runtime handling of interface data types as found in several object-oriented programming languages like Java. It extends an idea presented by League et al. [22] to attach an itable to a class object to obtain an interface object. A practical implementation of this approach based on an automated rather than a manual type conversion is presented. Its practibility in the context of Java is evaluated by an adaptation in the SableVM [15]. Several measures for its improvement have been derived and implemented. The adoption of the resulting technique for the implementation of interface method dispatches within SHAP [26,32], a small-footprint embedded implementation of a Java bytecode processor, is described. This realization currently also contains a tradeoff compromising some generality of the support for interface typecasts while it ensures both a small memory demand as well as a fast constant-time interface method dispatch. The loss of generality is shown to be of minimal practical impact under the measures taken before.

A Java Processor IP Design for Embedded SoC

“…Less attention has been dedicated to the study of interface design between a Java processor core and a general-purpose processor core. The most well studied objected-oriented features in the Java language include the schemes for method and interface invocations [Alpern et al 2001;Preusser et al 2007], the dynamic optimization of object accesses [Duesterwald 2005], and the garbage collectors [Schoeberl and Puffitsch 2010]. In addition, due to the objected-oriented programming practices, the locality behavior of the method bytecode execution is quite different from that of executing imperative programs on a register-based processor.…”

Increasing the efficiency of an embedded multi-core bytecode processor using an object cache

“…This tool does, however, not simply recompile the application classes but computes class and object layouts, resolves the class constant pools against these layouts, and also performs link-time optimizations such as method inlining, method call virtualization and devirtualization. The improved reference type constraints computed by a data flow analysis are also used for a SHAP-specific interface type coercion, which enables a constant-time interface method dispatch [10]. With this unique feature, the execution time of code on SHAP can be easily and safely predicted in the absence of exceptions.…”