You're reading from LLVM Code Generation A deep dive into compiler backend development

Product type Paperback

Published in May 2025

Publisher Packt

ISBN-13 9781837637782

Length 620 pages

Edition 1st Edition

Languages

C++

Tools

LLVM

Concepts

Programming Language

Author (1):

Quentin Colombet

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Table of Contents (30) Chapters

Preface

1. Part 1: Getting Started with LLVM

2. Building LLVM and Understanding the Directory Structure FREE CHAPTER

3. Contributing to LLVM

4. Compiler Basics and How They Map to LLVM APIs

5. Writing Your First Optimization

6. Dealing with Pass Managers

7. TableGen – LLVM Swiss Army Knife for Modeling

8. Part 2: Middle-End: LLVM IR to LLVM IR

9. Understanding LLVM IR

10. Survey of the Existing Passes

11. Introducing Target-Specific Constructs

12. Hands-On Debugging LLVM IR Passes

13. Part 3: Introduction to the Backend

14. Getting Started with the Backend

15. Getting Started with the Machine Code Layer

16. The Machine Pass Pipeline

17. Part 4: LLVM IR to Machine IR

18. Getting Started with Instruction Selection

19. Instruction Selection: The IR Building Phase

20. Instruction Selection: The Legalization Phase

21. Instruction Selection: The Selection Phase and Beyond

22. Part 5: Final Lowering and Optimizations

23. Instruction Scheduling

24. Register Allocation

25. Lowering of the Stack Layout

26. Getting Started with the Assembler

27. Unlock Your Book’s Exclusive Benefits

28. Other Books You May Enjoy

29. Index

Understanding the need for an IR

Until this point, we have not properly defined what an IR is and why you need one in a compiler. In this section, we will answer these two questions.

What an IR is

An IR is a data structure suitable for the tasks a compiler needs to do. The right IR depends on what the related compiler is expected to achieve.

For instance, if you build a tool that obfuscates the name of the variables of a C program by replacing them with random names, it might be enough to manipulate a string representing your program. Your transformation does not need to go too deep into the semantics of the input program, and since you support only C programs, you do not need to abstract away the syntax either. Similarly, imagine you build a compiler that translates C programs to assembly code for a specific X86 microarchitecture for a specific operating system (OS). Given the requirement of this tool, there are a lot of things that you do not need to abstract away, such...