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


In this chapter, we had a brief discussion about how a target architecture machine can be represented in LLVM. We saw the ease of using tablegen in organizing data such as register sets, instruction sets, calling conventions, and so on, for a given target. The llvm-tablegen then converts these target descriptor .td fies into enums, which can be used in program logic such as frame lowering, instruction selection, instruction printing, and so on. More detailed and complex architectures like ARM and X86 can give insight on a detailed description of the target.

In the first chapter, we tried a basic exercise to get hands-on with various tools provided by the LLVM infrastructure. In the subsequent chapters, that is, Chapter 2, Building LLVM IR, and Chapter 3, Advanced LLVM IR, we used APIs provided by LLVM to emit IRs. Readers can use those APIs in their frontend to convert their language to LLVM IR. In Chapter 5, Advanced IR Block Transformations, we got used to Pass Pipeline for IR optimization...