CS 241 — Spring 2017 — Assignment 3

Assignments for CS 241
← Assignment 2 Assignment 3 Assignment 4 ↓
Tuesday, May 23, 2017 at 5:00 pm Monday, May 29, 2017 at 5:00 pm Monday, June 5, 2017 at 5:00 pm
P1P2P3P4

Assignments 3 and 4 may be done in either Racket or C++14. See language-specific notes for each option at the end of this document.

In assignments 3 and 4, you will incrementally write an assembler for MIPS assembly language (CS241 dialect).

Note carefully: In order to do assignment 4, you must do assignment 3 first. We will not be distributing a solution to assignment 3 for you to use as a starting point for assignment 4.

Reminder: For this and future assignments, be sure to run the command source /u/cs241/setup to gain access to the CS 241 tools.

Part I. Tree Parsing

Problem 1 — 15 marks of 66 (filename: traverse.rkt or traverse.cc)

Write a Racket or C++ program that reads a pre-order traversal of a non-empty tree from standard input and prints the corresponding post-order traversal for that tree. Each line of both the input and output will consist of two non-negative integers:

<NODE-VALUE> <NUMBER-OF-CHILDREN>

for example the following input:

1 3
2 2
5 0
6 0
3 1
7 0
4 4
8 0
9 0
10 0
11 1
12 0
    
corresponds to this tree and the output of the program given the above input would be:
5 0
6 0
2 2
7 0
3 1
8 0
9 0
10 0
12 0
11 1
4 4
1 3
    

Test your program with different input.

You must solve this problem by constructing a tree from the given pre-order traversal, and then performing a post-order traversal on this tree. We reserve the right to hand-check that you have done this.

Submit a file called traverse.rkt or traverse.cc containing the Racket or C++ source code for your program.

Click here to return to the top of Assignment 3.

Part II. Writing an Assembler

For the remaining problems in assignment 3 and assignment 4 you will implement an assembler for progressively larger subsets of MIPS assembly language. Subject to the assumptions stated in the problems, your assembler must report all errors, and must correctly translate all correct assembly language programs to MIPS machine language.

We have provided a scanner (also called a tokenizer) for MIPS assembly language for each available language option (see language-specific notes). You should use this scanner as a starting point for your assembler.

Each problem in Part II requires you to submit a program that reads from standard input and writes to standard output as well as standard error. The input and output specifications are identical regardless of which language you choose. The only difference is that you must submit the appropriate .rkt or .cc file depending on your choice of language.

For each problem, we ask you to implement support for additional instructions. You may submit the same assembler for all the problems. We encourage you to submit to Marmoset early. As soon as you implement support for the instructions specified by a problem, submit the current version of your assembler to Marmoset. That way, if you do not complete all of the problems before the deadline, you will still get credit for those that you did complete.

Hint: Depending on the design decisions you make in your solutions to problems 2 and 3, you may have to restructure your code to get a working solution to problem 4. Therefore, you may want to read and understand all of the problems (especially up to and including problem 4) before beginning problem 2. However, if you find this overwhelming, you may find it easier to just focus on solving problems 2 and 3 first, and deal with problem 4 when you come to it. The decision is yours.

Problem 2 — 17 marks of 66 (filename: asm.rkt or asm.cc)

Begin by writing an assembler that correctly translates input containing no labels and no instructions other than .word. You may assume that the input to your assembler contains no labels and no instructions other than .word.

Your assembler should never crash, even if the input is not a valid assembly language program. Your assembler should not silently ignore errors in the input program. If the input contains a line that is not valid in MIPS assembly language, your assembler should print an appropriate error message containing the word ERROR in all capitals to standard error and stop. It is good practice, but not a requirement, to embed ERROR within a meaningful error message.

Hint: there are relatively few ways in which an assembly language program can be valid (and all the valid forms are spelled out here), but many ways in which it can be invalid. You will find it much easier to write code that looks for valid input and rejects everything unexpected, rather than code that explicitly looks for all the different ways in which the input could be invalid.

If the input contains a correct MIPS assembly language program, your assembler should output the equivalent MIPS machine language to standard output.

Click here to return to the top of Assignment 3.

Problem 3 — 17 marks of 66 (filename: asm.rkt or asm.cc)

Add support for label definitions to your assembler. Other than the inclusion of label definitions, the restrictions, assumptions and output requirements (including error-checking) stated in problem 2 apply to problem 3.

In addition, if the input is a correct MIPS assembly program, your assembler should output a symbol table: a listing of the names and values of all defined labels to standard error. The list should be printed on several lines, one line for each label in the input. Each line should consist of the label (without the trailing colon), followed by a space, followed by the value of the label (in decimal). The labels may appear in the symbol table in any order.

In handling labels, you may use any data structure or data structures you choose, but be sure to take efficiency into account.

Click here to return to the top of Assignment 3.

Problem 4 — 17 marks of 66 (filename: asm.rkt or asm.cc)

Modify your assembler to allow labels to be defined and also to be used as operands.

Other than the inclusion of label definitions and labels as operands, the restrictions, assumptions, and output requirements (including error-checking) stated in problem 2 apply to problem 4. (Note that you need not list the names and values of defined labels as in problem 3.)

Click here to return to the top of Assignment 3.

CS 241 — Spring 2017 — Assignment 4

Assignments for CS 241
↑ Assignment 3 Assignment 4 Assignment 5→
Monday, May 29, 2017 at 5:00 pm Monday, June 5, 2017 at 5:00 pm Monday, June 12, 2017 at 5:00 pm
P1P2P3P4P5P6P7

Note: The restrictions, assumptions, and output requirements (including error-checking) as stated in assignment 3 apply throughout assignment 4 as well. In addition, your solution for each problem should continue to be a correct solution for each problem that came before it (for example, a correct solution of A4P3 will also meet the requirements of A4P1 and A4P2).

Problem 1 — 9 marks of 60 (filename: asm.rkt or asm.cc)

Modify your assembler to correctly handle jr and jalr instructions.

Click here to return to the top of Assignment 4.

Problem 2 — 9 marks of 60 (filename: asm.rkt or asm.cc)

Modify your assembler to correctly handle add, sub, slt, and sltu instructions.

Click here to return to the top of Assignment 4.

Problem 3 — 9 marks of 60 (filename: asm.rkt or asm.cc)

Modify your assembler to correctly handle beq and bne instructions with an integer or hex constant as the branch offset.

Click here to return to the top of Assignment 4.

Problem 4 — 9 marks of 60 (filename: asm.rkt or asm.cc)

Modify your assembler to correctly handle beq and bne instructions with a label as the branch target operand.

Click here to return to the top of Assignment 4.

Problem 5 — 8 marks of 60 (filename: asm.rkt or asm.cc)

Modify your assembler to correctly handle the lis, mflo, and mfhi instructions.

Click here to return to the top of Assignment 4.

Problem 6 — 8 marks of 60 (filename: asm.rkt or asm.cc)

Modify your assembler to correctly handle the mult, multu, div, and divu instructions.

Click here to return to the top of Assignment 4.

Problem 7 — 8 marks of 60 (filename: asm.rkt or asm.cc)

Modify your assembler to correctly handle the sw and lw instructions.

Your assembler should correctly translate any MIPS assembly language program, and write ERROR to standard error for any input that is not a valid MIPS assembly program.

Click here to return to the top of Assignment 4.

Language-Specific Details

Racket

The provided starter asm.rkt has a function called scan that takes as input a string and returns a list of tokens.

The Using Racket in CS 241 document contains hints and techniques for using Racket to write the assembler. See also the comments in the provided scanner.

Run a Racket program using the command: racket asm.rkt

C++14

The provided starter asm.zip has a method called ASM::Lexer::scan that returns a vector of token pointers.

When submitting to Marmoset, if you have chosen C++, you will need to add all of your files to a .zip (or similar archive) and submit that to Marmoset.

The STL Quick Reference for CS 241 document outlines the parts of the STL most likely to be of use in CS 241.

You are strongly advised to check for pointer-related errors by vetting your programs with valgrind. To do this, run "valgrind program optionsAndArguments" instead of just "program optionsAndArguments" on a Linux or Macintosh computer — valgrind is not available for the Solaris or Windows environments. Marmoset will run your submissions with valgrind as well, and will reject any submission that is reported to leak memory. Be aware that running valgrind increases the execution time of your program by a factor of 5 to 20.

Compile a program in C++ using the command "g++ -o asm asm.cc lexer.cc kind.cc".

This command will create a file called asm containing the compiled code.

Run the program using the command: ./asm