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

Here comes the Machine IR

If you’ve already followed the logs that were produced by the print-before-all or print-after-all option (see Chapter 10) to the assembly code, then you’ve already encountered the Machine IR.

Indeed, any transformation that runs after the instruction selection pass produces the Machine IR. Figure 11.1 illustrates the whole compilation process and mentions where the Machine IR appears:

Figure 11.1 shows the input file (input.c) going through the frontend and being converted into the LLVM IR. Then, the backend takes over and starts by performing a sequence of LLVM IR to LLVM IR transformations. This sequence is, as you know, called the middle-end. Next, the backend runs the instruction selection pass, which translates the LLVM IR into Machine IR. This marks the beginning of the backend part of the backend (confusing, we know!). From this point forward, all the remaining passes...