Fern

Fern is a multi-stage optimizing compiler for a statically-typed imperative programming language.

Example

A simple program that calculates the 10th number in the Fibonacci series:

fn fib(n: int) -> int {
    if (n <= 1) {
        return n;
    }

    return fib(n - 1) + fib(n - 2);
}

fn main() -> int {
    return fib(10);
}

Compile and run:

$ fern example.fern
$ ./example
$ echo $?
55

Compilation Pipeline

The compiler implements a modern compilation pipeline with several optimization stages:

1. Source code is parsed into an Abstract Syntax Tree (AST)
2. A symbol table is generated to track variable and function scopes
3. The AST is converted to Three-Address Code (TAC)
4. Dead code elimination removes unreachable code paths
5. A Control Flow Graph (CFG) is built for analysis
6. Conversion to Static Single Assignment (SSA) form
7. SSA is translated to LLVM Intermediate Representation (IR)
8. Finally, LLVM compiles the IR to a native executable

Source

The source for Fern is available on GitHub.