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

View More author details

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

Debugging the selectors

As you saw throughout this chapter, selectors are complicated pieces of machinery and it is common that they do not behave the way you would expect.

In this section, we will give you some guidelines to help you debug issues that are specific to the selectors.

For starters, everything that you learned so far for debugging LLVM still applies. You need to use the debug-only command-line option and the dump methods to help you inspect the IR.

Let us start with tips that are specific to SDISel.

Debugging SDISel

When debugging the SDISel issue, you can use the dumpr method of the SDNode instance. This method allows printing the children of a node and the children of its children and so on until the specified depth (and argument of this method) is reached. (Note that such a method also exists on the MachineInstr instances but requires you to provide a MachineRegisterInfo instance.) Moreover, when using the dump or dumpr method on an SDNode instance...