Project 6: Compilation

In this project, you will complete a compiler for SwiJay (called JaySea, inspired by javac) which produces Java VM assembly (which can then be used to generate classfiles).

You should mainly think of this as a compiler for Jay, except that one extra tricky part--switch statements---is added at the end.

1. Set-up.

Many other pieces are provided for you, and can be found in a tar file.

cp ~tvandrun/Public/cs365/proj6.tar .

The system works like this. The program swijay/jaysea.py reads in a swijay file and parses it. Then the CompilerVisitor (which your task is to finish implementing) transforms that into Java assembly as defined for the Jasmin tool (the output here is a .jj file). Then JaySea feeds the Java assembly into Jasmin (whose output is a .class file). Finally JaySea executes the classfile using the Java VM.

Assembling and running the swijay program are optional. The --no-run flag makes JaySea produce a .class file supresses execution of the resulting file. The --no-assem flag supresses Jasmin (and hence also supresses execution, since we wouldn't have a .class file to execute)

2. Your task

Your task is finishing the visit methods in compilerVisitor.py. For all Jay statements and expressions, what series of instructions needs to be emitted, and how does that affect the stack?

Some specifics:

3. Suggestions

Make use of these resources:

Make your changes to JaySea incrementally. Then gradually add statements and expressions. Do switch statements last. Switch statements can be compiled to the instruction lookupswitch (or, if you're really ambitious, tableswitch). Remember that the statements inside a switch are called InSwitchStatements, and there are "regular" statements, cases, breaks, and defaults. You will need to do some processing of the whole switch statement at the beginning to generate the switch instruction, and then visit the InSwitchStatements.

As you work, I recommend you have both Jay and Java versions of your test files. Compile the Java versions and disassemble them with javap to see what the result might look like. Your output does not have to be identical to what javac produces--often there is an equivalent series of instructions that you'll find are easier to produce---but javac can guide you through some of the knottier statements.

4. Extra credit

All you need is a compiler that produces programs that work to get full credit. But there are some optimizations you could perform for which I will award extra credit. For example, if (x > 0)... would naively be complied by loading x, pushing 0, generating the sequence for >, and then ifne, but a more efficient version would load x and use if_icmpgt. Also, x = x + 1; could be done using the iinc instruction. Some switch statements can be compiled to a tableswitch instead of a lookupswitch.

5. To turn in

To turn in this project, please copy your compile.sml and, if you did any optimizations for extra credit, a text file describing what you did to

/cslab.all/ubuntu/cs365/turnin/xxxxxx/proj6

where "xxxxxx" is [elliot|payton|davidemmanuel|nathan|gill|brandon|sean|simon]. I will grade your project by running it against a collection of test files.

Due: Wed, April 2, 5:00 pm.


Thomas VanDrunen
Last modified: Tue Mar 25 13:18:27 CDT 2014