Project Overview

You may do this assignment in OCaml, Python, JavaScript, Haskell or Ruby.

You may work in a team of two people for this assignment. You may work in a team for any or all subsequent programming assignments. You do not need to keep the same teammate. The course staff are not responsible for finding you a willing teammate.

Goal

You will also write additional code to unserialize the class map, implementation map, parent map, and annotated AST produced by the semantic analyzer.

The Specification

1. A program that takes a single command-line argument (e.g., file.cl-type). That argument will be an ASCII text Cool class map, implementation map, parent map and annotated AST file (as described in PA4). Your program must emit either Cool Assembly Language (file.cl-asm) or x86-64 Assembly Language (file.s). Your program will consist of a number of files in a single programming language.
   • If you are targeting Cool Assembly Language, then executing file.cl-asm in a Cool CPU Simulator must produce the correct output for file.cl according to Cool's operational semantics.
   • If you are targeting x86-64, then compiling file.s with gcc on a 64-bit x86 Linux system must produce an executable that, when run, produces the correct output for file.cl according to Cool's operational semantics.
   • You will only be given .cl-type files from programs that pass the semantic analysis phase of the reference compiler. You are not responsible for correctly handling (1+"hello") programs.
2. A plain ASCII text file called readme.txt describing your design decisions and choice of test cases. See the grading rubric. A few paragraphs should suffice.
3. Testcases test1.cl and test2.cl. The testcases should exercise compiler corner cases.

Assembly Language

Cool Assembly Language is a simplified RISC-style assembly language that is similar to Java Bytecode.

• Pro: It is dynamically "well typed", so if you produce assembly code that tries to add a string to a code label, the system will notice immediately (rather than producing garbage and unhelpfully crashing later).
• Pro: It is portable and works anywhere the Reference Compiler works.
• Pro: It abstracts away notions like system calls and string handling so that you can focus on code generation and layout.
• Pro: It has just enough instructions to directly compile Cool and no more — learning it is simple.
• Pro: It includes built-in debugging and tracing suppot.
• Con: Because it is a simualted bytecode, you cannot use GDB or Visual Studio to debug your output.
• Con: Because it is a simulated bytecode, you cannot actually "run the raw .exe" on your computer.

x86-64 Assembly Language is the real deal — it's what most desktop machines use.

• Pro: You get a strong feeling of accomplishment for working close to "the bare metal" and using a real-world assembly language. Employers know that writing an optimizing compiler that targets x86 is not easy!
• Pro: You can use GDB or Visual Studio to step through and debug your resulting executable.
• Pro: For the subsequent optimization assignment, you can use any instruction, power or trick that is legal on x86-64 to squeeze every last drop of performance out of your code.
• Con: There are many dialect and syntax options of "x86 assembly language". This course only allows the 64-bit version supported by gcc on linux. If you can't run that on your development machine, you must use Cool Assembly.
• Con: You must handle all of the details, including laying out strings in memory and emitting assembly code that interfaces with standard library functions like malloc or scanf or exit to implement Cool's operational semantics.
• Con: You'll have to use GDB (or something similar) because there's no innate debugging support.
• Con: x86 assembly is infamous for being hideous. It's your funeral.

./cool --x86 hello-world.cl
gcc hello-world.s
./a.out

Although we're invoking gcc, that's just shorthand: it's calling as and collect2 and whatnot to assemble the .s file into an object file and link that object file into an executable. You can see the individual steps with gcc -v.

No Error Reporting

Restricted Subset of Cool

• attribute_*
• self_dispatch — except IO (e.g., in_out, out_int)
• static_dispatch
• dynamic_dispatch
• internal functions
• while
• isvoid
• case
• new
• let_binding_init
• any novel class/method — except "Main.main"
• run-time errors (e.g., division by zero)
• strings — programs will largely involve integers and booleans

Commentary

You will have to handle certain internal functions (e.g., IO.out_string) that are defined in PA4.

You can do basic testing as follows:

• $ cool --asm file.cl-type
  $ cool file.cl-asm >& reference-output
  $ my-code-generator file.cl-type 
  $ cool file.cl-asm >& my-output
  $ diff my-output reference-output
  

Whitespace and newlines do not matter in your file.{cl-asm,s} assembly code. However, whitespace and newlines do matter for your simulated Cool CPU output. This is because you are specifically being asked to implement IO (and, later, substring) functions.

You should implement all of the relevant operational semantics rules in the Reference Manual. You will also have to implement all of the relevant built-in functions on the IO class.

What To Turn In For CA3

1. readme.txt -- your README file
2. test1.cl -- a testcase
3. test2.cl -- a testcase
4. source_files -- your implementation, including
   • main.rb or
   • main.py or
   • main.js or
   • main.hs or
   • main.ml

• team.txt -- an optional file listing your other team member (see below -- if you are not working in a team, do not include this file)

Working In Pairs

Students on a team are expected to participate equally in the effort and to be thoroughly familiar with all aspects of the joint work. Both members bear full responsibility for the completion of assignments. Partners turn in one solution for each programming assignment; each member receives the same grade for the assignment. If a partnership is not going well, the teaching assistants will help to negotiate new partnerships. Teams may not be dissolved in the middle of an assignment.

If you are working in a team, exactly one team member should submit a CA3 zipfile. That submission should include the file team.txt, a one-line flat ASCII text file that contains exactly and only the email address of your teammate. Don't include the @virgnia.edu bit. Example: If ph4u and wrw6y are working together, ph4u would submit ph4u-ca3.zip with a team.txt file that contains the word wrw6y. Then ph4u and wrw6y will both receive the same grade for that submission.

Autograding

In each case we will then compare your output to the correct answer:

• diff testcase.out correct-answer.out

We will perform the autograding on a 64-bit Linux system. However, your submissions must officialy be platform-independent (not that hard with a scripting language). You cannot depend on your compiler running on any particular platform (although you can depend on the resulting assembly code running on its associated platform).

There is more to your grade than autograder results. See the Programming Assignment page for a point breakdown.

Your submission may not create any temporary files. Your submission may not read or write any files beyond its input and output. We may test your submission in a special "jail" or "sandbox".