Simple Swift Compiler

A simple Swift compiler implementation written in Rust. This project implements a basic lexer, parser, and LLVM code generator for a subset of the Swift programming language.

Features

• Lexer: Tokenizes Swift source code
• Parser: Builds an Abstract Syntax Tree (AST) with operator precedence
• LLVM Code Generator: Generates LLVM IR from the AST
• Native Execution: Compiles and executes code via LLVM toolchain
• Arithmetic Operations: Supports basic math operations (+, -, *, /)
• Variable Declaration: Support for let declarations with type inference
• Variable References: Use declared variables in expressions
• Command-line Options: Verbose mode for detailed compilation output

Building the Project

cargo build

Running the Compiler

Basic Usage

cargo run -- example/Test.swift

Verbose Mode

For detailed compilation output including tokens, AST, and LLVM IR:

cargo run -- --verbose example/Test.swift
# or
cargo run -- -v example/Test.swift

Command-line Options

• --verbose or -v: Enable verbose output showing all compilation stages

This will:

1. Read the Swift source file
2. Tokenize the input (Frontend: Lexical Analysis)
3. Parse the tokens into an AST (Frontend: Syntax Analysis)
4. Generate LLVM IR code (Frontend: IR Generation)
5. Save LLVM IR to target/llvm/output.ll
6. Execute the code using LLVM toolchain (if installed)

Supported Features

Currently, the compiler supports:

• print statements
• Integer literals
• Variable declarations with let
• Variable references in expressions
• Arithmetic expressions (+, -, *, /)
• Expression parsing with operator precedence
• Abstract Syntax Tree (AST) generation
• LLVM IR generation with stack allocation for variables

Requirements

• Rust 1.56 or later
• Cargo
• LLVM toolchain (optional, for code execution)

Installing LLVM on macOS

brew install llvm
export PATH="/opt/homebrew/opt/llvm/bin:$PATH"

Installing LLVM on Linux

sudo apt-get install llvm  # Ubuntu/Debian
# or
sudo yum install llvm      # RHEL/CentOS

Development

To check for compilation errors without building:

cargo check

Architecture

The compiler follows a modular architecture:

1. Frontend (Source → LLVM IR):

   • lexer.rs: Converts source code into tokens
   • parser.rs: Builds AST from tokens with operator precedence
   • codegen.rs: Generates LLVM IR from AST

2. Backend (LLVM IR → Execution):

   • llvm_backend.rs: Handles LLVM toolchain interaction
   • Saves IR to files
   • Executes via LLVM interpreter (lli)
   • Can compile to native code (llc + clang)

3. Orchestration:

   • compiler.rs: Coordinates the compilation pipeline
   • main.rs: CLI interface

Generated Files

When you run the compiler, it generates:

• target/llvm/output.ll - LLVM IR code
• target/llvm/output.s - Assembly code (when using llc)
• target/llvm/output - Native executable (when using clang)

License

Apache 2.0