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

Lowering the ABI with FastISel

Aside from the lowering of the formal arguments, the lowering of the ABI in FastISel is intermixed with the selection process itself and, as such, there are fewer target hooks that need to be implemented.

In practice, this means that you must handle the lowering of the ABI yourself when you do the selection of the LLVM IR call and ret instructions. You will see where this code lives in Chapter 17.

For formal arguments, you need to override the FastISel::fastLowerArguments method. This method returns true if you manage to handle the lowering of the formal arguments or false otherwise. When false is returned and the fallback mechanism is enabled, SDISel will switch to a selection process based purely on a SelectionDAG instance for the current basic block.

In the implementation of FastISel::fastLowerArguments (or any FastISel method), you are free to leverage the CCState class. However, usually, FastISel is only implemented for very specific...