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 3. Advanced LLVM IR

LLVM provides a powerful intermediate representation for efficient compiler transformations and analysis, while providing a natural means to debug and visualize the transformations. The IR is so designed that it can be easily mapped to high level languages. LLVM IR provides typed information, which can be used for various optimizations.

In the last chapter, you learned how to create some simple LLVM instructions within a function and module. Starting from simple examples such as emitting binary operations, we constructed functions in a module and also created some complex programming paradigms such as if-else and loops. LLVM provides a rich set of instructions and intrinsics to emit a complex IR.

In this chapter, we will go through some more examples of LLVM IR which involve memory operations. Some advanced topics such as aggregate data types and operations on them will also be covered. The topics covered in this chapter are as follows:

  • Getting the address of an...