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Kawa: Compiling Scheme to Java

1.14 Code generation

A Compilation object keeps track of the classes, methods, and temporary state generated as a result of compiling a single top-level ModuleExp.

class Compilation { ClassType[] classes; boolean immediate; public ClassType addClass (LambdaExp lexp, String name) { ... } public ClassType (ModuleExp exp, ...) { ...; addClass (exp, ...); } ... }

Each Compilation may create one or more ClassType objects, each of which generates the bytecodes for one class. Each ClassType is generated from a LambdaExp, including the top ModuleExp. The boolean immediate is true if we are compiling for immediate loading, and is false if the target is one or more .class files.

The addClass method does all the work to compile a given LambdaExp. It creates a ClassType, adds it to Compilation's classes array, and generates Method objects for the constructor and the main applyX method. Once the applyX Method has been created, addClass emits some bytecodes to set up the incoming parameters, and then invokes the virtual compile method on the body of the LambdaExp, which generates the code that does the actual work of the procedure.

The Compilation constructor gets a ModuleExp, which it passes to addClass. The compile method of LambdaExp (which gets called for all lambdas except the dummy top-level) also calls addClass to generate the class corresponding to the lambda, and then it emits instructions to create a new instance of the generated Procedure class, and pushes it on the Java stack.