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 2. Building LLVM IR

A high level programming language facilitates human interaction with the target machine. Most of the popular high level languages today have certain basic elements such as variables, loops, if-else decision making statements, blocks, functions, and so on. A variable holds value of data types; a basic block gives an idea of the scope of the variable. An if-else decision statement helps in selection of a path of code. A function makes a block of code reusable. High level languages may vary in type checking, type casting, variable declarations, complex data types, and so on. However, almost every other language has the basic building blocks listed earlier in this section.

A language may have its own parser which tokenizes the statement and extracts meaningful information such as identifier, its data type; a function name, its declaration, definition and calls; a loop condition, and so on. This meaningful information may be stored in a data structure where the flow...