Jimple: Simplifying Java Bytecode for Analyses and Transformations

In this paper we present Jimple, a 3-address intermediate representation that has been designed to simplify analysis and transformation of Java bytecode. We motivate the need for a new intermediate representation by illustrating several difficulties with optimizing the stack-based Java bytecode directly. In general, these difficulties are due to the fact that bytecode instructions affect an expression stack, and thus have implicit uses and definitions of stack locations. We propose Jimple as an alternative representation, in which each statement refers explicitly to the variables it uses. We provide both the definition of Jimple and a complete procedure for translating from Java bytecode to Jimple. This definition and translation have been implemented using Java, and finally we show how this implementation forms the heart of the Sable research projects