198:415 Compilers
Spring 1999
Professor Barbara G. Ryder


Programming Assignment 6
Code Generation II: Producing SPIM Code

due: midnight Friday, April 30, 1999
NO EXTENSIONS

This assignment involves generating executable SPIM code from the intermediate code fragments you generated in Assignment 5. You will need all of the classes from Assginment 5 plus some new ones in /use/local/class/cs415/sp99/tiger/PROJECT6. We expect you to run your outputted SPIM codes to make sure they work. We will supply some simple test programs so you can tell what output to expect. A description of the new subdirectories and files is as follows:

• Canon/

  Canon package is used for symplifying the intermidiate code tree produced so far . We will use only one translormation called linearize , which will transform the intermidiate code tree into a list of smaller and simpler subtrees linked in a list, which will subsequently be used for SPIM code generation.

  linearize() method is called in the provided Parse/Main.java file .

• Assem/ contains the Assem package as described by the text book at page 210 .
• Semant/ contains our answer files from Assignment 4. If your assignment was not correct, you can use our package, but this will be difficult as this package is quite large and thus a bit hard to understand. It would be better for you to look at our code and fix yours; otherwise, come in and consult with us after you have looked at the package.
• Parse/Main.java This file is the driver for this assignment.
• Frame/

  A new abstract method ( implemented in SPIM/SPIMFrame.java) has been added to the class Frame.java :
  
  abstract public Tree.StmList procEntryExit3(Tree.StmList body);

• SPIM/
  • SPIMFrame.java

    The implementation for procEntryExit3 has been added . This method adds the prologue and epilogue of a function ( in our case only the main program ). It is called in the Parse/Main.java driver provided .

  • Codegen.java

    This class contains the code generation routines as suggested in book at page 215 .

    Here is where you have to write code for this part of the project .

    It contains

    • a list of instructions ilist
    • a method to add a new instruction to the list : emit
    • a method which returns the list : codegen
    • 2 dispacher methods for traversing the intermediate code trees and generating SPIM code : munchStm and munchExp . these are the methods which you have to implement , together with their auxiliary methods , if need be .

      You are given some startup code which generates SPIM code for a program containing just a number . I suggest you run the project as soon as you copy it using the test1 file .

  Suggestion: As we will not use register allocation , don't construct any new temporary register . You will use the following rules :

  • The result of any expression evaluation will be placed in

    $v0 

    register.
  • only one temporayy register will be used :

    $t0

  Example : addition will have the following code
  
  

  add $v0,$v0,$t0 

  Hint: You will have to use the stack to save $t0 , each time you will generate code for an expression/ statement which uses it. Here is the code you have to generate for saving a register on the stack :

  
  sw $t0,($sp)
  addi $sp,$sp,-4
  
  

  and for restoring a register:

  
  addi $sp,$sp,4
  lw $t0,($sp)
  
  

  After you generate the code, run it on the SPIM to make sure it's error free.

  Suggested Progression

  As usual, in writing the methods in this assignment, you should proceed incrementally. We suggest first generating SPIM code for Ocelot programs consisting solely of numerical expressions with constant operands. Next add let expressions and scalar variables. Then add conditional expressions, assignments, looping statements without breaks and then breaks.

  Make sure you check the errata sheet for the textbook before starting.

  How to proceed?

  For organizing your cs415 work, you should create a new subdirectory for every new assignment. All assignment directories and files should be read and write protected so that only you can read or write the directory and its files.

  In addition, you will need to add to your CLASSPATH in order to access the packages needed to do this, and subsequent assignments. The easiest way to do this is to add the following line to your .cshrc or .tshrc file:

   #a change to access
  packages in cs415 setenv CLASSPATH
  .:/ug/s1/class/cs415/sp99/JLex/classes/:/ug/s1/class/cs415/sp99/CUP/classes/

  To begin, you should create a working directory proj6 for Assignment 6 and then copy the directories contained in /usr/local/class/cs415/sp99/tiger/PROJECT6. recursively (use -R to get subdirectories) into your working directory. If you don't use your files you can start . If you use your files , read the list of modifications above and update your files appropriately.

  To execute your program on input file test.tig in your working directory using the main method in Parse.Main, type:
  java Parse.Main test.tig

  We will be using tar to turn in all the packages and classes you use in this assignment, so we can see how you may have customized them. Please follow these directions:

  • Connect to your working directory (where your makefile is); let's assume this is proj6

  • Type tar cvf proj6.tar proj6

  • Then use the handin program we have been using to turn in the file proj6.tar

  We also want you to turn in a hard copy of your COMMENTED Codegen.java class , including a listing of the test data used to test your program. We require a 1-2 page (not handwritten) summary of what you have done. Please make sure your code is runnable. It is preferable to submit code which contains only a subset of the language assigned but which runs, rather than code that supposedly covers everything assigned, but does not compile or run correctly.

  
  
  Last updated by Florin Isaila at 3:04pm on April 15, 1999.