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

The use of the MC layer

The MC layer is used to handle the final representation of the actual instructions of the target. The final representation in the context of a backend compiler is either the textual or binary representation of the object file.

Figure 12.2 illustrates when the MC layer is used in the LLVM infrastructure:

Figure 12.2: MC, the glue for handling with the final output of the compiler

Looking closer at Figure 12.2, you can see that the Machine IR gets compiled to the MC representation. Then you can print the MC representation to produce assembly files (.s), in other words, the textual representation of an object file, or assemble it to produce the binary file that is typically called the object file (.o). These are the two main output paths used with MC.

Similarly, MC is used as the representation when coming from either an assembly or object file. For assembly files, the LLVM infrastructure parses the textual representation and internally produces...