C90 (ANSI) to MIPS 1 Compiler

Introduction

• This is a (non fully featured) compiler written in C++ for ANSI C89/C90 to MIPS 1 (ABI Compliant)
• It uses Flex for lexical analysis, and Bison (3.3.2) for parsing to an AST.
• The target environment is Ubuntu 16, however a lot of the features may work on Unix based systems such as MacOS (exempt features are mentioned below).
• The compiler conforms to this specification: http://port70.net/~nsz/c/c89/c89-draft.html
• The project conforms to this specification: https://github.com/LangProc/langproc-2018-cw
• It assumes the input C is perfectly valid, well-formed, pre-processed C90. It performs some minimal optimization and error checking but do not rely on it for anything useful.
• Also includes a basic C to Python translator

Usage

Make the project:
make clean
make bin/c_compiler

To compile a C file into MIPS, simply run
bin/c_compiler -S <source-file.c> -o <dest-file.s>

To translate from C to Python (limitations described below), simply run
bin/c_compiler --translate <source-file.c> -o <dest-file.py>

Features

You will see these things printed to the console when running the compiler:

• The input C code printed in canonical form. This is to ensure the parser correctly read and converted the C code into an AST. It can be found in bin/printC.c
• The 3 address code intermediate language. It can be found in bin/intermediateLanguage.txt
• The MIPS code generated
• The translated Python (if running with the --translate flag)

Compiler:

The compiler does not support the full range of C90 features due to time constraints we had with the project, however we encourage anyone to improve/finish the compiler (hence the MIT License).

Some things the compiler fully supports:

• Functions with unlimited arguments
• Variables of int type
• Arithmetic and logical expressions
• If else and switch statements
• Operators
• For, while, and do while loops
• Arrays
• Char literals
• Sizeof (kind of)
• Pointers, addressing and dereferencing

Some things the compiler does not support:

• Structs and Unions
• Enums (started, never finished)
• Strings
• Multithreading
• Goto
• Macros and other preprocessing directives
• Comma operator (for sequencing within expressions)
• The old K&R style of declaring functions
• Variable-length arrays
• Const
• Pointer arithmetic
• Non int primitives
• Typedef

C to Python translator:

Some things the translator supports:

• Local and global integer variables (non nested scopes)
• Functions (definition and invocation) with integer arguments and void/integer return type
• Explicit support for main special functionality
• If, else, while, return, and sequences
• Decimal integer constants
• Integer arithmetic
• &&, ||, <, and ==
• Assignment as a direct expression statement

Some things the translator does not support:

• Variable shadowing
• Most other things not listed in support section above

Testbench

The testbench runs unit tests to test the C to Python translator and the compiler itself. The compiler-specific unit tests only (have been confirmed to) run on Linux, with mips-linux-gnu-gcc and qemu-mips installed.

The compiler tests can be run using:

test/compiler/src/runTests.sh

and the C to Python translator tests can be run using:

test/pythonTranslator/src/runTests.sh

You will see a pythonTranslator folder in test/compiler/tests. These were generated by a tool, devtools/translatorToCompilerTests.sh, that converts C to Python translator tests into compiler tests.

You can see the results in the log folder in test/compiler and test/pythonTranslator/log folders.

The compiler currently passes 172/177 tests

Extras

We added some cool features:

• View diagram of AST with Graphviz (or an online dot file viewer, like https://dreampuf.github.io/GraphvizOnline) (dot file can be found in bin/ast.dot once compiler has been run as described in Usage section)
• View the AST that the Clang compiler generates on any C file you give it using playground/ast/generateAST.sh <program_name.c>

Credits

The creators of this project are:
EthanSK https://github.com/EthanSK
QFSW https://github.com/QFSW