Book Image

Learn LLVM 12

By : Kai Nacke
Book Image

Learn LLVM 12

By: Kai Nacke

Overview of this book

LLVM was built to bridge the gap between compiler textbooks and actual compiler development. It provides a modular codebase and advanced tools which help developers to build compilers easily. This book provides a practical introduction to LLVM, gradually helping you navigate through complex scenarios with ease when it comes to building and working with compilers. You’ll start by configuring, building, and installing LLVM libraries, tools, and external projects. Next, the book will introduce you to LLVM design and how it works in practice during each LLVM compiler stage: frontend, optimizer, and backend. Using a subset of a real programming language as an example, you will then learn how to develop a frontend and generate LLVM IR, hand it over to the optimization pipeline, and generate machine code from it. Later chapters will show you how to extend LLVM with a new pass and how instruction selection in LLVM works. You’ll also focus on Just-in-Time compilation issues and the current state of JIT-compilation support that LLVM provides, before finally going on to understand how to develop a new backend for LLVM. By the end of this LLVM book, you will have gained real-world experience in working with the LLVM compiler development framework with the help of hands-on examples and source code snippets.
Table of Contents (17 chapters)
Section 1 – The Basics of Compiler Construction with LLVM
Section 2 – From Source to Machine Code Generation
Section 3 –Taking LLVM to the Next Level


In this chapter, you learned about the techniques a real-world compiler uses in the frontend. Starting with the project's layout, you created separate libraries for the lexer, the parser, and the semantic analyzer. To output messages to the user, you extended an existing LLVM class, which allowed the messages to be stored centrally. The lexer has now been separated into several interfaces.

You then learned how to construct a recursive descent parser from a grammar description, which pitfalls to avoid, and how to use generators to do the job. The semantic analyzer you constructed performs all the semantic checks that are required by the language while being intertwined with the parser and AST construction.

The result of your coding effort was a fully decorated AST, which will be used in the next chapter to generate IR code and object code.