Milestone 5 : Code Generation

Your task in this milestone is to extend the StaticJava code generator to support ExtendedStaticJava programs. The differences between StaticJava and ExtendedStaticJava are highlighted in the EBNF for ExtendedStaticJava. Most of the work in this milestone requires you to override and extend the ByteCodeGenerator.Visitor visit methods in a file ExtendedByteCodeGenerator.java to implement code generation for the ESJ constructs.

For extra credit, you may implement a selection of different optimizations. These can be improvements to the code generation strategies that exist in the SJ ByteCodeGenerator. They can also be implemented as transformations of the AST. For example, you could implement a visitor that transforms expressions in the AST to, e.g., perform arithmetic on operators with constant operands at compile time, to simplify arithmetic expressions based on identities or other algebraic properties. Note that these simplifications can "cascade" through a program yielding additional opportunities for optimization. You can receive up to 25 additional points for completing this extra credit. Credit will be assigned in 5 point increments for each distinct optimization that is described, implemented and demonstrated via test cases.

You must submit your assignment through the course Project Upload site by 11:59pm CDT on Friday Nov. 30, 2007.

Download the file myname-milestone5.zip

This contains a skeletal implementation of the milestone with a JUnit testing framework for your use.

In order to import the projects into your workspace, do the following:

Goto the "File" menu, select "Import". Expand "General" and select "Existing Projects into Workspace". Click "Next". Select "Select archive file:" and click the "Browse" button associated with it. In the file browser, points to the milestone2.zip that you downloaded.

You should see "myname-milestone5", check the box, and click "Finish".

If you run Eclipse appropriately (i.e., using Java 5.0 and the right versions of plugins and by following the instructions in the course quick notes website), your workspace should be set.

Make sure you rename "myname" in the project's name into your CIS username by right clicking the project, select "Refactor" -> "Rename...".

Your assignment is to implement the bytecode generator for ESJ. You will do this by adding to the file:

sjc.codegen.extended.ExtendedByteCodeGenerator

ByteCodeGenerator

The milestone skeleton contains a completely working version of the ESJ compiler up through type checking.

You can tell if you are making progress by running the JUnit test suite. This is done by highlighting the class:

sjc.test.extended.ExtendedByteCodeGeneratorTest

You can see the source of the test cases in src-examples directory of the milestone. For this milestone, the unit testing is done by actually executing the generated code from your compiler. Some of the tests include assertion statements that test the results calculated by your generated code.

You are done when all of the test cases pass or your run out of time.

It is a useful design strategy to write down a code generation template for each new construct in ESJ before implementing it. Use the templates from lecture as a guide. Then you can map your rule to an implementation following the model of the StaticJava code generator.

IMPORTANT: Try to reuse as much of the StaticJava code generator as possible. You will definitely need to make some changes and perhaps add new visit methods, but there is much that can be reused and there is lots to learn from studying that code.

Your solution should consist of the following :

• a modified version of ExtendedByteCodeGenerator.java that correctly generates bytecodes for ExtendedStaticJava
• a description of all of the new code generation templates you implemented to handle the ESJ features. These should be integrated into the header comments for each code generation method in the visitor that you create. Note that while these are comments, I expect them to be precise.
• a single text file that describe your implementation including any limitations and anything special you had to do to handle the extensions
• for extra credit, you must all of the code that you modify or implement. You must also provide documentation of the optimizations you implement and provide at least two test cases for each optimization that illustrate how that optimization works.

As with all programming, I expect that you provide reasonable internal documentation describing tricky/subtle parts of your implementation. If you have any limitations in your implementation If you have any limitations in your implementation you should include documentation describing those as well, since if we find them we will assume that you did not.

Your grade will be based on your solution (80%), your in code generation template documentation (15%), and the description of limitations you provide (5%).