Preface

A compiler is one of the most prevailing tools used by programmers. The majority of programmers have compilers – or some form of compilation technique – in their development flow. A modern compiler not only transforms high-level programming languages into low-level machine code, but also plays a key role in optimizing the speed, size, or even the memory footprint of the program it compiles. With these characteristics, building a production-ready compiler has always been a challenging task.

LLVM is a framework for compiler optimization and code generation. It provides building blocks that significantly reduce the efforts of developers to create high-quality optimizing compilers and programming language tools. One of its most famous products is Clang – the C-family language compiler that builds thousands of pieces of widely-used software including the Google Chrome browser and iOS apps. LLVM is also used in compilers for many different programming languages, such as the famous Swift programming language. It is not an exaggeration to say that LLVM is one of the hottest topics when it comes to creating a new programming language.

With hundreds of libraries and thousands of different APIs, LLVM provides a wide range of features, from key functionalities for optimizing a program to more general utilities. In this book, we provide a complete and thorough developer guide to two of the most important sub-systems in LLVM – Clang and the middle-end. We start with introductions to several components and development best practices that can benefit your general development experiences with LLVM. Then, we will show you how to develop with Clang. More specifically, we will focus on the topics that help you augment and customize the functionalities in Clang. In the last part of this book, you will learn crucial knowledge about LLVM IR development. This includes how to write an LLVM Pass with the latest syntax and mastering processing different IR constructions. We also show you several utilities that can greatly improve your productivity in LLVM development. Last but not least, we don't assume any particular LLVM version in this book – we try to keep up to date and include the latest features from the LLVM source tree.

This book provides a handful of code snippets and sample projects in every chapter. You are encouraged to download them from the GitHub repository of this book and play around with your own customizations.