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 608 pages

Edition 1st Edition

Languages

C++

Tools

LLVM

Concepts

Programming Language

Author (1):

Quentin Colombet

View More author details

Table of Contents (29) Chapters

Preface

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. 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. Introduction to the Backend

14. Getting Started with the Backend

15. Getting Started with the Machine Code Layer

16. The Machine Pass Pipeline

17. 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. Final Lowering and Optimizations

23. Instruction Scheduling

24. Register Allocation

25. Lowering of the Stack Layout

26. Getting Started with the Assembler

27. Other Books You May Enjoy

28. Index

Overview of the instruction selection frameworks

You can view an instruction selector as a funnel that takes the massive space of a program that can be represented in LLVM IR and narrows it down to an equivalent program that only uses the instructions available for your backend.

The LLVM infrastructure offers two (and a half!) different frameworks to help you solve the instruction selection (ISel) problem. The main two frameworks are, respectively, SelectionDAG (also known as SDISel), which is the legacy instruction selector, and GlobalISel (also known as GISel), which is the newer selector. There is also a sub-framework called FastISel, which is part of the SDISel framework. From this point forward, we will use SDISel, GlobalISel, and FastISel as nouns, since this is what is done in all LLVM documentation.

Therefore, right off the bat, you must choose which selector you want to use for your backend. The frameworks all share some common infrastructure, thanks to TableGen,...