CS 453 Programming Assignment #2 — MiniJava and MIPS warmup

Due Wednesday February 17th (by 11:59pm)

Introduction

In this assignment you will be writing some MIPS functions so as to learn the stackframe layout we are using and to write some of the MIPS functions that will be in the MiniJava run-time library. Also you will be writing MiniJava programs and the corresponding MIPS assembly programs. This introduces you to the source and target languages for the MiniJava compiler. It also provides an opportunity for you to create a couple of MiniJava test cases.

The Assignment

Your MiniJava compiler will be generating MIPS assembly language, specifically you will be generating MIPS code that is compatible with the MARS simulator (http://courses.missouristate.edu/KenVollmar/MARS/).

For this assignment, you need to implement the following functions in MIPS:

void _printint(int): Prints given integer followed by a newline
void* _localtest(int n): Allocates space for 5 local variables and returns the address where the nth local variable is located. n will be a number in the range 1..5.
void* _halloc(int n): Allocates n consecutive bytes in the heap and returns the address of the first byte allocated. (Hint: sbrk syscall)

The MIPS functions will be called by the driver stackframe-testdriver.s (see stackframe-testdriver.c for an approximate C version). For grading we will use our own version of stackframe-testdriver.s, so do not modify the one given to "make things work". Put each MIPS implementation in a file named after the function, but remove the underscore. For example, _printint will be implemented in printint.s. We will be calling your routines by concatenating your .s files with stackframe-testdriver.s and then interpreting the full file in MARS.

We will be using the same stack frame layout as is used in the Patt and Patel book from CS 270. The calling convention is summarized in the stack frame example given to help with HW1, and we will be covering the calling convention in class.

You also need to implement the following programs in MiniJava and in MIPS. When running the MiniJava program using javac and java, you should get the same results as running the MIPS program through MARS. These programs are so simple that we will be looking at the code to makes sure the actual computation is being done.

CountDown.java and CountDown.s: Implement a recursive method called countdown, which should accept an integer as input and print that integer followed by all integers between that number and 0. For example, countdown(4) results in the output:
```
4
3
2
1
```
NOTE: It must be implemented recursively! For both CountDown.java and CountDown.s have your main routines call the countdown() method with the actual parameter 7.
ObjectFun.java and ObjectFun.s: Allocate space on the heap for two object instances of a class with an integer member variable and a boolean member variable.
```
    class MyClass {
        boolean b;
        int i;
    }
```
In the first instance set b to true and i to 42. In the second instance set b to false and i to 33. Then print the value of both fields in both object instances: one value per line.

When writing the MiniJava program make sure to only use Java language features that are in the MiniJava grammar. You can test this by grabbing a copy of the MJ.jar from ~cs453/public and executing the following:

    % java -jar MJ.jar Program.java

The MJ generates a bunch of files (Program.java.*). Check them out if you would like, but they are irrelevant for this assignment. If you run into problems, look at the MiniJava grammar and determine whether the program you wrote can be generated by that grammar.

Getting Started

To get started, put the following MIPS program into a file called helloworld.s, download a copy of the Mars.jar file from http://courses.missouristate.edu/KenVollmar/MARS/, and run helloworld.s through MARS by typing "java -jar Mars.jar helloworld.s" on any CS linux machine.

## helloworld.s
    .text
    .globl main
main:
    # There is no need to store $ra and $fp
    # in main for MARS because execution always
    # starts at the top of the input .s file
    # and $ra and $fp always have initial 
    # values of 0.
            
            
    # print Hello World!

    # The number put into $v0 selects MARS syscall.
    # A parameter to a system call should be passed in $a0.
    li      $v0, 4
    la      $a0, hello_world
    syscall



exit_main:
    # HALT the MARS simulation.
    li      $v0, 10
    syscall

        .data
hello_world:    .asciiz "Hello World!\n"

Also make sure to check out the MARS IDE by typing "java -jar Mars.jar". Some other examples to look at include sum5.s and readprint.s. sum5.s requires that you concatenate your implementation for _printint before running it.

    % cat sum5.s printint.s > sum5_all.s
    % java -jar Mars.jar sum5_all.s

Read the Appendix A: Assemblers, Linkers, and the SPIM Simulator from the third edition of Hennessy and Patterson, Computer Organization and Design: The Hardware/Software Interface for a description of various MIPS instructions and read the online syscalls notes for how to use MARS system calls.

Submitting the Assignment

Make sure you test your implementation thoroughly.
Only turnin one assignment per group.
Use subversion to export a copy of your assignment.
Include all the funcname.s files, all the MiniJava source files, a README file, and a subversion.txt file in a tar file.
- The README file should include your username(s), emails(s), and any information you want the TA to have before grading your assignment. E.g., this part is not working due to..., a favorite quote or joke to amuse the TA, etc.
- The subversion.txt file should include output from the following:
```
    svn log -r HEAD:1
    svn info
    svnlook tree REPOSITORY_PATH  svnlook must be issued on a department machine
    
```

Submit assignment using checkin utility.

~cs453/bin/checkin PA2 PA2_groupname.tar

Sanity Check (procedure TA will use to run your assignment):

    tar xf PA2_groupname.tar
    cd PA2

    cat stackframe-testdriver.s printint.s halloc.s localtest.s  > all.s
    java -jar Mars.jar all.s

    javac CountDown.java
    java CountDown > CountDown.java.out
    java -jar Mars.jar CountDown.s > CountDown.s.out
    diff CountDown.s.out CountDown.java.out

ObjectFun will be tested in the same way as CountDown. The extra output that MARS generates:

  
MARS 3.8  Copyright 2003-2010 Pete Sanderson and Kenneth Vollmar

will be ignored.

Late Policy

Late assignments will be accepted up to 24 hours past the due date and time for a deduction of 20% and will not accepted past this period. Late means anything after 11:59pm on the day the assignment is due, including 12 midnight.

mstrout@cs.colostate.edu .... February 6, 2010