Book Image

LLVM Essentials

By : Mayur Pandey, Suyog Sarda, David Farago
Book Image

LLVM Essentials

By: Mayur Pandey, Suyog Sarda, David Farago

Overview of this book

LLVM is currently the point of interest for many firms, and has a very active open source community. It provides us with a compiler infrastructure that can be used to write a compiler for a language. It provides us with a set of reusable libraries that can be used to optimize code, and a target-independent code generator to generate code for different backends. It also provides us with a lot of other utility tools that can be easily integrated into compiler projects. This book details how you can use the LLVM compiler infrastructure libraries effectively, and will enable you to design your own custom compiler with LLVM in a snap. We start with the basics, where you’ll get to know all about LLVM. We then cover how you can use LLVM library calls to emit intermediate representation (IR) of simple and complex high-level language paradigms. Moving on, we show you how to implement optimizations at different levels, write an optimization pass, generate code that is independent of a target, and then map the code generated to a backend. The book also walks you through CLANG, IR to IR transformations, advanced IR block transformations, and target machines. By the end of this book, you’ll be able to easily utilize the LLVM libraries in your own projects.
Table of Contents (14 chapters)
LLVM Essentials
About the Authors
About the Reviewer

Chapter 1. Playing with LLVM

The LLVM Compiler infrastructure project, started in 2000 in University of Illinois, was originally a research project to provide modern, SSA based compilation technique for arbitrary static and dynamic programming languages. Now it has grown to be an umbrella project with many sub projects within it, providing a set of reusable libraries having well defined interfaces.

LLVM is implemented in C++ and the main crux of it is the LLVM core libraries it provides. These libraries provide us with opt tool, the target independent optimizer, and code generation support for various target architectures. There are other tools which make use of core libraries, but our main focus in the book will be related to the three mentioned above. These are built around LLVM Intermediate Representation (LLVM IR), which can almost map all the high-level languages. So basically, to use LLVM's optimizer and code generation technique for code written in a certain programming language, all we need to do is write a frontend for a language that takes the high level language and generates LLVM IR. There are already many frontends available for languages such as C, C++, Go, Python, and so on. We will cover the following topics in this chapter:

  • Modular design and collection of libraries

  • Getting familiar with LLVM IR

  • LLVM Tools and using them at command line