How to write a compiler ?

This series of blogs acts as an analysis and deep dive into compiler design.

Currently I am building EEL. EEL is eBPF Language, this series of blogs consists of all the things I learned throughout the process of building it.

What is a compiler?

A compiler is a program that translates source code written in one language into another representation, usually machine code or an intermediate form that can be executed by a computer.

The Puzzle Pieces

Modern compilers are made up of several different pieces which come together as a puzzle to make a compiler.

These pieces are:

• Lexer - Converts character streams to token streams.
• Parser - Builds Abstract Syntax Trees (AST) based on grammar rules.
• Semantic Analyzer - Performs type check, scope validation, and AST checks.
• IR Generator - Produces Intermediate Representation.
• Optimizer - Refactors code pathways for high performance.
• Code Generator - Translates IR to target architecture assembly/bytecode.
• Assembler - Turns assembly text into binary machine instructions.
• Linker - Combines machine instructions and externs into an Executable.

We will analyze each of these one by one in great detail.

Source Code
     ↓
   Lexer
     ↓
  Tokens
     ↓
  Parser
     ↓
    AST
     ↓
Semantic Analysis
     ↓
     IR
     ↓
 Optimizer
     ↓
Code Generator
     ↓
 Assembler
     ↓
   Linker
     ↓
 Executable

Pseudocode Reference

Throughout the blogs we will take following pseudocode as reference:

fn add(a,b){
    price = 10;
    total = price + 42;
    print(total);
}

Aadarsh Chandra (Pi)

I am an 18-year-old self-employed developer building full-stack web applications, Python/Rust backends, and low-level systems. I learn by building things from first principles.