Translating Java for resource constrained embedded systems

This paper discusses a strategy for translating the Java programming language to a form that is suitable for execution on resource limited embedded systems such as softcore processors in FPGAs, Network-on-Chip nodes and microcontrollers. The translation strategy prioritises the minimisation of runtime memory usage, generated code size, and suitability for a wide range of small architectures over other desirable goals such as execution speed and strict adherence to the Java standard. The translation procedure, or Concrete Hardware Implementation of a software application first converts the application's compiled Java class files to a self-contained intermediate representation conducive to optimisation and refactoring. The intermediate format is then serialised into a programming language compilable to the target architecture. This paper presents techniques for analysing whole Java applications, translating Java methods and building a stand-alone translated application with the same functional behaviour as the original Java. An example C-code generator is described and evaluated against similar previous approaches. An existing benchmark application, JavaBenchEmbedded, is demonstrated to require less than 30KiB of program code and 16KiB of runtime heap memory when executing on a Xilinx MicroBlaze Processor.