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

Overview of the lowering of a textual assembly file

The process of assembling a textual assembly file consists of taking a textual assembly file and turning it into a sequence of bits that comply with the target file format.

During this process, there are two main things that need to happen:

The encoding of the instructions, which you discovered how to do in Chapter 12
The encoding of the addresses of the symbols, such as the target of a jump or a call

The second point represents the main difficulty in assembling a textual assembly file. Indeed, resolving the address of a symbol may only be possible at (dynamic) link time when all object files and libraries are finally known.

In other words, the assembler needs to resolve all the symbols as best as it can, then leave some directive to the linker, called relocations, for the ones it could not resolve.

Figure 21.1 shows the overall steps that the assembler goes through when lowering assembly code...