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

The expansion of the frame indices

In principle, replacing the frame indices that you’ve used so far is an easy task. As already mentioned, the MachineFrameInfo instance of your function maintains a mapping of the frame indices to an offset in your stack. Therefore, replacing the frame indices with the stack address is as simple as translating each index with its corresponding computation: stack plus offset.

Note

The offset held by the mapping in the MachineFrameInfo instance is described from the beginning of the stack frame. Therefore, you can use this offset directly if you use a frame pointer, but you need to adjust it to account for the changes made in the prologue if you use a stack pointer. We will come back to this and illustrate it in Figure 20.3.

In practice, things get more complicated because materializing your stack-plus-offset value may require you to introduce additional instructions, and since the expansion happens after register allocation...