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C Compiler

This is a compiler for a subset of C, written by a group of 6 people for a class. The lexer and parser are generated with Antlr4, while our compiler implements an IR, some optimizations, and assembler code emission for the x86 architecture.

Architecture

architecture.png

  • Antlr4 generates the lexer and parser from the grammar specified in ifcc.g4.
  • These Antlr classes generates the AST (Abstract Syntax Tree) from the source code.
  • With a visitor pattern, the AST is then used by:
    • Type checking vistior
    • IR generation visitor
  • The IR (Intermediate Representation) is composed of:
    • IR instructions: an abstraction over architecture dependent assembly instructions.
    • Basics blocks: a sequences of instructions without jumps. Each basic block has a scope, which contains a symbol table with all the variables declared, and a pointer to its parent scope.
    • Control flow graphs: a graph of basic blocks with the jumps between them, one graph per function.
  • A constant propagation optimizer is applied to the IR.
  • The IR is then used to generate the x86 assembly. It is achieved with a visitor pattern for decoupling, to easily add support for other architectures.

Supported subset of C

  • Comments with /* */ and //
  • Variables of type int and char
  • Arrays (declaration, assignment, and access only)
  • Arithmetic operators: + - * / %
  • Logic operators: | & ^ !
  • Comparison operators: == != < > <= >=
  • IO with getchar and putchar
  • Functions (with a return value or void)
  • Scopes with { } (with variable shadowing)
  • Control flow with if else while
  • break and continue

Each feature was rigorously tested in the tests directory, which serves as a detailed reference of the capabilities. Some example algorithms have been written in the examples directory to demonstrate the usability of the compiler.

The compiler also generates errors and warnings for various problems.

A more detailed user manual is available in French.

Usage

Dependency

Install Antlr4 using your system package manager, or by running the script ./install-antlr.sh.

In the makefile directory, make a copy of the appropriate makefile for your platform, and rename it to config.mk. If you have used the installation script, you can skip this step.

Compilation

Compile the project: make -j (this flag enables parallel compilation, which is much faster)

You can now compile a program from our subset of C to x86 assembler with ./ifcc program.c

Tests

Compile and run all tests: make -j test

To run a single test: ./ifcc-test.py program.c

Documentation

Generate the C++ documentation with Doxygen: make doc

The documentation is in HTML format. To view it, open the file doc/index.html.