Decaf Compiler

A compiler for Decaf, a simplified C-like language, written in Rust. Includes several dataflow optimizations and a register allocator. Built with Andrew and Selena for Computer Language Engineering (spring 2025)!

Pipeline

The compiler runs through six stages to convert .dcf source files to x86-64 Assembly:

1. Scanning - scans the source file and converts it into tokens
2. Parsing - parses the tokens into an AST (abstract syntax tree)
3. Semantic checking - checks that the syntax tree conforms to the Decaf language's rules
4. CFG construction - constructs a control flow graph representing the source code's path(s) of execution
5. Dataflow optimizations - perform several optimizations to make the resulting code smaller and faster
6. Register allocation & x86-64 code generation - allocates variables to CPU registers in a way that maximizes program execution speed, then generates the final x86-64 code

Usage

./build.sh          # cargo build --release
./run.sh -t <stage> [-O <opt,..>] [-o <outfile>] [-d] <input.dcf>

• -t / --target — stage to run: scan, parse, inter (semantic check), or assembly
• -O / --opt — comma-separated optimizations to apply (currently dce, or all)
• -o / --output — output file (defaults to stdout)
• -d / --debug — print intermediate representations (AST, CFG, etc.) to stderr

Compile and run a Decaf program end-to-end:

./run.sh -t assembly tests/codegen/input/01-import.dcf -o out.S -O dce
gcc -O0 -no-pie out.S -o out
./out