CS 4980 CC: Assignment 4: Intermediate Representation

The goal of this assignment is to give you experience generating intermediate representation from code. You will work in teams of two or three students for this.

A starting point for this assignment is in the IntelliJ project, as4irgen.zip. The solution should unpack and build with no errors, at least when using JDK 8. (It will likely build and run with other versions as well, but esubmit uses JDK 8.) To run, ensure the Project Structure includes the appropriate version of JDK and then add a start configuration:

• Set the program argument to test/0.mj. This will run your program on a file in the test directory by default; you can change which file you use during testing. 0.mj is good because everything in it is already implemented except code to evaluate a constant value expression. Once this is working, you will want to move on to the other tests. fact.mj exercises a lot of the mini-java language.
• On the right of the start configuration screen, note the blue text "Modify options". Click on this and select Add VM options. Set the VM options to -ea to enable assertion checks that are in the code. This will help you debug your solution.

Your edits will be in the file ToTree.java. See the TODO statements in this file. You can change other files in the top directory as well (Frame.java, MIPSFrame.java, ToTreeList.java, X86Frame.java), but it is unlikely you will need to make modifications to these files. Note that sablecc.jar has already been run on the grammar file and that your main is already set up to build the symbol table and typecheck the program.

Some additional notes on the files you have been given:

• Temp: Code from Chapter 6 of the textbook to manage temporaries and labels.
• Tree: Code from Chapter 7 of the textbook to manage intermediate representation trees.
• test: a few test files, some with odd names that I won't justify! esubmit may use additional tests.
• ToTree: the intent is that this will generate an intermediate representation from the given .mj source file.

Clarifications

• The intended target will be MIPS. Assume all integers and pointers occupy 4 bytes.
• In Java, the standard is that new arrays and new objects are initialized to all zeros. That is not a requirement for this assignment, but see below.
• The generated code will call a function we will need to write, sysprint, to print integers. We will not support printing other types of data.
• The provided code supports method calls but fails to include this, essentially implying all methods are static at the moment. We may fix this in a future assignment.
• In some cases it is convenient to use an ESEQ item so you can do a series of actions and return a result, even if that result is thrown away. If the result is being thrown away, return a new CONST(0) for uniformity with the tests.
• The sample output and some of the provided code is using Code instructions to add documentation in the output. This helps tremendously when trying to review and debug compiler output. You will need to match these in your solutions. More specifically, while loops are documented by

          ;;while text of test
  

  before the loop and

          ;;end while
  

  at the end. Assignments are documented by

          ;; id = expression
  

  (before the code computing the assignment), and the new expression is documented with

          ;;new classname()
  

  where the italicized words are replaced by the appropriate text. Each ;; comment is preceded by two tab characters.
• While it is possible to match the output in esubmit exactly, it is likely that many correct solutions will have small differences.

Sample Run

Not all tests will have sample output because the primary goal of the assignment is to determine what output to produce. It is also not clear that every correct solution will produce the same output. The instructor's solution produces factorial-output.txt for the input fact.mj.

Groups of 3

Groups of 3 will have additional requirements. These requirements will not be tested by esubmit, so we may use demos to confirm them.

• Add inline code to initialize arrays and objects to all 0s.
• Add support for a .length operation on arrays. This will include restoring the related productions, storing the array length in memory at runtime (probably at the start of the array's location, revising indexing to skip that location), and providing support for a .length factor in expressions.
• Add support for this and extended classes.

Submission

Make sure all group members are documented at the top of ToTree.java. Submit your solution to esubmit as as4ir. At a minimum, submit ToTree.java as the main and ToTreeList.java as an additional file. Include any other files you write or modify, but most solutions will not need additional files. Do not submit mjava.grammar; talk to your instructor if you needed to modify the grammar file for your solution.

Since this is a group assignment, your instructor needs to know which esubmit solution to grade. After your final submission, take a screen shot showing the top part of the submission (with the assignment name, the name of the user doing the submitting, the date, and the number of differences) and submit that screen shot to Canvas.