Search icon CANCEL
Subscription
0
Cart icon
Your Cart (0 item)
Close icon
You have no products in your basket yet
Save more on your purchases! discount-offer-chevron-icon
Savings automatically calculated. No voucher code required.
Arrow left icon
Explore Products
Best Sellers
New Releases
Books
Videos
Audiobooks
Learning Hub
Newsletter Hub
Free Learning
Arrow right icon
timer SALE ENDS IN
0 Days
:
00 Hours
:
00 Minutes
:
00 Seconds
LLVM Code Generation
LLVM Code Generation

LLVM Code Generation: A deep dive into compiler backend development

Arrow left icon
Profile Icon Quentin Colombet
Arrow right icon
$37.99
Paperback May 2025 608 pages 1st Edition
eBook
$29.99
Paperback
$37.99
Subscription
Free Trial
Renews at $19.99p/m
Arrow left icon
Profile Icon Quentin Colombet
Arrow right icon
$37.99
Paperback May 2025 608 pages 1st Edition
eBook
$29.99
Paperback
$37.99
Subscription
Free Trial
Renews at $19.99p/m
eBook
$29.99
Paperback
$37.99
Subscription
Free Trial
Renews at $19.99p/m

What do you get with Print?

Product feature icon Instant access to your digital copy whilst your Print order is Shipped
Product feature icon Paperback book shipped to your preferred address
Product feature icon Redeem a companion digital copy on all Print orders
Product feature icon Access this title in our online reader with advanced features
Product feature icon DRM FREE - Read whenever, wherever and however you want
OR
Modal Close icon
Payment Processing...
tick Completed

Shipping Address

Billing Address

Shipping Methods
Table of content icon View table of contents Preview book icon Preview Book

LLVM Code Generation

Building LLVM and Understanding the Directory Structure

The LLVM infrastructure provides a set of libraries that can be assembled to create different tools and compilers.

LLVM originally stood for Low-Level Virtual Machine. Nowadays, it is much more than that, as you will shortly learn, and people just use LLVM as a name.

Given the sheer volume of code that makes the LLVM repository, it can be daunting to even know where to start.

In this chapter, we will give you the keys to approach and use this code base confidently. Using this knowledge, you will be able to do the following:

  • Understand the different components that make a compiler
  • Build and test the LLVM project
  • Navigate LLVM’s directory structure and locate the implementation of different components
  • Contribute to the LLVM project

This chapter covers the basics needed to get started with LLVM. If you are already familiar with the LLVM infrastructure or followed the tutorial...

Technical requirements

To work with the LLVM code base, you need specific tools on your system. In this section, we list the required versions of these tools for the latest major LLVM release: 20.1.0.

Later, in Identifying the right version of the tools, you will learn how to find the version of the tools required to build a specific version of LLVM, including older and newer releases and the LLVM top-of-tree (that is, the actively developed repository). Additionally, you will learn how to install them.

With no further due, here are the versions of the tools required for LLVM 20.1.0:

Tool

Required version

Git

None specified

C/C++ toolchain

>=Clang 5.0

>=Apple Clang 10.0

>=GCC 7.4

&gt...

Getting ready for LLVM’s world

In the Technical requirement section, we already listed which version of tools you needed to work with LLVM 20.1.0. However, LLVM is a lively project and what is required today may be different than what is required tomorrow. Also, to step back a bit, you may not know why you need these tools to begin with and/or how to get them.

This section addresses these questions, and you will learn the following in the process:

  • The purpose of each required tool
  • How to check that your environment has the proper tools
  • How to install the proper tools

Depending on how familiar you are with development on Linux/macOS, this setup can be tedious or a walk in the park.

Ultimately, this section aims to teach you how to go beyond a fixed release of LLVM by giving you the knowledge required to find the information you need.

If you are familiar with package managers (e.g., the apt-get command-line tool on Linux and Homebrew...

Building a compiler

In this section, we will introduce the different parts of what makes a compiler and how they relate to the LLVM code base. In the process, you will do the following:

  • Understand the overall architecture of a compiler
  • Learn how to build Clang from the source
  • Be able to decide which components of LLVM you need to build

If you are already familiar with the components of a compiler toolchain and want to jump straight into the action, skip directly to the Building LLVM section.

What is a compiler?

The definition of a compiler means different things for different people. For instance, for a student in their first year of computer science, a compiler may be seen as a tool that translates a source language into executable code. This is a possible definition, but it is also a very coarse-grain one.

When you look closer at a compiler, you will find that it is a collection of different tools, or libraries, working together to achieve...

Building LLVM

This is where your journey as a backend developer starts: you will learn how to build the core LLVM project.

Instead of just dropping a bunch of commands for you to run (we will do some of that too, we promise), you will discover the most relevant knobs that you can use to tailor the build process to your needs.

We believe this is important knowledge to gain as it will help you optimize your development process and increase your productivity by focusing on what you need to build/run for your use cases.

To set the context, the core LLVM project contains all the necessary pieces to build an optimizing backend from LLVM IR down to assembly code/an object file for 20+ different architectures. This is a lot of code and chances are that you do not care about all these architectures. Therefore, at the very least, learning how to build only the ones you care about will save you compile time and down the road will improve your development speed.

Configuring the...

Testing a compiler

In the previous section, you have learned how to run the core LLVM unit tests, but this is only the beginning of the story. There are two big missing pieces:

  • How do you understand and reproduce a failing unit test?
  • How do you go beyond unit testing?

Let us answer these questions in the following sections. However, first, we need a primer on some of the tools/infrastructure used for testing in LLVM.

Crash course on the Google test infrastructure

LLVM uses the Google test infrastructure (gtest) for some of its unit tests.

The tests based on gtest are regular C++ codes and produce regular executables. If you open one of the source files of the tests using this framework, you will find gtest-specific directives (e.g., EXPECT_EQ, TEST, etc.) but nothing complicated beyond that.

Running the related executable will directly reproduce whatever issue you may want to investigate and all the techniques you know for debugging C++ code...

Understanding the directory structure

In this section, you will learn the basics of how the LLVM folders are organized. This knowledge will come in handy when you start contributing to LLVM. This will help you shape patches that follow the philosophy behind the directory structure and hence, help you avoid unnecessary rounds of reviews where you would have to fix that.

High-level directory structure

At a high level, the LLVM code base is organized into projects: Clang, MLIR, the LLVM debugger (LLDB), and many more. Each project has its own directory, and its name matches the name of the related project in lowercase: clang, mlir, lldb, and so on.

You need to use these directory names in the LLVM_ENABLE_PROJECTS CMake variable to build the related projects.

The common theme around these projects is that they use or contribute to a part of the LLVM infrastructure.

Focusing on the core LLVM project

Unsurprisingly, the core LLVM project lives in the llvm directory...

Summary

In this chapter, you learned how to set up your development environment and how to find the required version of the different tools to build the different versions of the LLVM infrastructure, including the open-source repository. This is a necessary step to be able to get started with building the LLVM infrastructure.

Next, you discovered the main components that make a compiler toolchain, namely the driver, frontend, backend, linker, and standard library, and which LLVM project they map to. This information will come in handy when you decide what you want to build out of the LLVM infrastructure.

After that, you dove into the build configurations of the core LLVM project and learned how to tweak the CMake variables to tailor the build to your needs while balancing the debuggability of the produced artifacts and the build time. You also learned how to use Ninja, the driver of the build system, efficiently to reduce the turnaround time between development, building,...

Quiz time

Now that you have completed reading this chapter, answer the following questions to test your knowledge:

  1. You have a pristine clone of the LLVM code base and yet the build fails with weird compiler errors. What could be the reason?

The most likely reasons are as follows:

  1. You have a C file, and you are curious about what the LLVM IR looks like without optimization. How can you print this IR using Clang?

You can run the following:

$ clang -S -O0 -emit-llvm myFile.c -o -

See Experimenting with Clang.

  1. You want to build LLVM for just the AMDGPU and X86 backends. Which CMake variable should you set and how do you set it?

You want to set the variable...

Left arrow icon Right arrow icon
Download code icon Download Code

Key benefits

  • Understand the steps involved in generating assembly code from LLVM IR
  • Learn the key constructs needed to leverage LLVM for your hardware or backend
  • Strengthen your understanding with targeted exercises and practical examples in every chapter
  • Purchase of the print or Kindle book includes a free PDF eBook

Description

The LLVM infrastructure is a popular compiler ecosystem widely used in the tech industry and academia. This technology is crucial for both experienced and aspiring compiler developers looking to make an impact in the field. Written by Quentin Colombet, a veteran LLVM contributor and architect of the GlobalISel framework, this book provides a primer on the main aspects of LLVM, with an emphasis on its backend infrastructure; that is, everything needed to transform the intermediate representation (IR) produced by frontends like Clang into assembly code and object files. You’ll learn how to write an optimizing code generator for a toy backend in LLVM. The chapters will guide you step by step through building this backend while exploring key concepts, such as the ABI, cost model, and register allocation. You’ll also find out how to express these concepts using LLVM's existing infrastructure and how established backends address these challenges. Furthermore, the book features code snippets that demonstrate the actual APIs. By the end of this book, you’ll have gained a deeper understanding of LLVM. The concepts presented are expected to remain stable across different LLVM versions, making this book a reliable quick reference guide for understanding LLVM.

Who is this book for?

This book is for both beginners to LLVM and experienced LLVM developers. If you’re new to LLVM, it offers a clear, approachable guide to compiler backends, starting with foundational concepts. For seasoned LLVM developers, it dives into less-documented areas such as TableGen, MachineIR, and MC, enabling you to solve complex problems and expand your expertise. Whether you’re starting out or looking to deepen your knowledge, this book has something for you.

What you will learn

  • Understand essential compiler concepts, such as SSA, dominance, and ABI
  • Build and extend LLVM backends for creating custom compiler features
  • Optimize code by manipulating LLVM's Intermediate Representation
  • Contribute effectively to LLVM open-source projects and development
  • Develop debugging skills for LLVM optimizations and passes
  • Grasp how encoding and (dis)assembling work in the context of compilers
  • Utilize LLVM's TableGen DSL for creating custom compiler models
Estimated delivery fee Deliver to United States

Economy delivery 10 - 13 business days

Free $6.95

Premium delivery 6 - 9 business days

$21.95
(Includes tracking information)

Product Details

Country selected
Publication date, Length, Edition, Language, ISBN-13
Publication date : May 23, 2025
Length: 608 pages
Edition : 1st
Language : English
ISBN-13 : 9781837637782
Category :
Languages :
Tools :

What do you get with Print?

Product feature icon Instant access to your digital copy whilst your Print order is Shipped
Product feature icon Paperback book shipped to your preferred address
Product feature icon Redeem a companion digital copy on all Print orders
Product feature icon Access this title in our online reader with advanced features
Product feature icon DRM FREE - Read whenever, wherever and however you want
OR
Modal Close icon
Payment Processing...
tick Completed

Shipping Address

Billing Address

Shipping Methods
Estimated delivery fee Deliver to United States

Economy delivery 10 - 13 business days

Free $6.95

Premium delivery 6 - 9 business days

$21.95
(Includes tracking information)

Product Details

Publication date : May 23, 2025
Length: 608 pages
Edition : 1st
Language : English
ISBN-13 : 9781837637782
Category :
Languages :
Tools :

Packt Subscriptions

See our plans and pricing
Modal Close icon
$19.99 billed monthly
Feature tick icon Unlimited access to Packt's library of 7,000+ practical books and videos
Feature tick icon Constantly refreshed with 50+ new titles a month
Feature tick icon Exclusive Early access to books as they're written
Feature tick icon Solve problems while you work with advanced search and reference features
Feature tick icon Offline reading on the mobile app
Feature tick icon Simple pricing, no contract
$199.99 billed annually
Feature tick icon Unlimited access to Packt's library of 7,000+ practical books and videos
Feature tick icon Constantly refreshed with 50+ new titles a month
Feature tick icon Exclusive Early access to books as they're written
Feature tick icon Solve problems while you work with advanced search and reference features
Feature tick icon Offline reading on the mobile app
Feature tick icon Choose a DRM-free eBook or Video every month to keep
Feature tick icon PLUS own as many other DRM-free eBooks or Videos as you like for just $5 each
Feature tick icon Exclusive print discounts
$279.99 billed in 18 months
Feature tick icon Unlimited access to Packt's library of 7,000+ practical books and videos
Feature tick icon Constantly refreshed with 50+ new titles a month
Feature tick icon Exclusive Early access to books as they're written
Feature tick icon Solve problems while you work with advanced search and reference features
Feature tick icon Offline reading on the mobile app
Feature tick icon Choose a DRM-free eBook or Video every month to keep
Feature tick icon PLUS own as many other DRM-free eBooks or Videos as you like for just $5 each
Feature tick icon Exclusive print discounts

Table of Contents

28 Chapters
Getting Started with LLVM Chevron down icon Chevron up icon
Building LLVM and Understanding the Directory Structure Chevron down icon Chevron up icon
Contributing to LLVM Chevron down icon Chevron up icon
Compiler Basics and How They Map to LLVM APIs Chevron down icon Chevron up icon
Writing Your First Optimization Chevron down icon Chevron up icon
Dealing with Pass Managers Chevron down icon Chevron up icon
TableGen – LLVM Swiss Army Knife for Modeling Chevron down icon Chevron up icon
Middle-End: LLVM IR to LLVM IR Chevron down icon Chevron up icon
Understanding LLVM IR Chevron down icon Chevron up icon
Survey of the Existing Passes Chevron down icon Chevron up icon
Introducing Target-Specific Constructs Chevron down icon Chevron up icon
Hands-On Debugging LLVM IR Passes Chevron down icon Chevron up icon
Introduction to the Backend Chevron down icon Chevron up icon
Getting Started with the Backend Chevron down icon Chevron up icon
Getting Started with the Machine Code Layer Chevron down icon Chevron up icon
The Machine Pass Pipeline Chevron down icon Chevron up icon
LLVM IR to Machine IR Chevron down icon Chevron up icon
Getting Started with Instruction Selection Chevron down icon Chevron up icon
Instruction Selection: The IR Building Phase Chevron down icon Chevron up icon
Instruction Selection: The Legalization Phase Chevron down icon Chevron up icon
Instruction Selection: The Selection Phase and Beyond Chevron down icon Chevron up icon
Final Lowering and Optimizations Chevron down icon Chevron up icon
Instruction Scheduling Chevron down icon Chevron up icon
Register Allocation Chevron down icon Chevron up icon
Lowering of the Stack Layout Chevron down icon Chevron up icon
Getting Started with the Assembler Chevron down icon Chevron up icon
Other Books You May Enjoy Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon
Get free access to Packt library with over 7500+ books and video courses for 7 days!
Start Free Trial

FAQs

What is the digital copy I get with my Print order? Chevron down icon Chevron up icon

When you buy any Print edition of our Books, you can redeem (for free) the eBook edition of the Print Book you’ve purchased. This gives you instant access to your book when you make an order via PDF, EPUB or our online Reader experience.

What is the delivery time and cost of print book? Chevron down icon Chevron up icon

Shipping Details

USA:

'

Economy: Delivery to most addresses in the US within 10-15 business days

Premium: Trackable Delivery to most addresses in the US within 3-8 business days

UK:

Economy: Delivery to most addresses in the U.K. within 7-9 business days.
Shipments are not trackable

Premium: Trackable delivery to most addresses in the U.K. within 3-4 business days!
Add one extra business day for deliveries to Northern Ireland and Scottish Highlands and islands

EU:

Premium: Trackable delivery to most EU destinations within 4-9 business days.

Australia:

Economy: Can deliver to P. O. Boxes and private residences.
Trackable service with delivery to addresses in Australia only.
Delivery time ranges from 7-9 business days for VIC and 8-10 business days for Interstate metro
Delivery time is up to 15 business days for remote areas of WA, NT & QLD.

Premium: Delivery to addresses in Australia only
Trackable delivery to most P. O. Boxes and private residences in Australia within 4-5 days based on the distance to a destination following dispatch.

India:

Premium: Delivery to most Indian addresses within 5-6 business days

Rest of the World:

Premium: Countries in the American continent: Trackable delivery to most countries within 4-7 business days

Asia:

Premium: Delivery to most Asian addresses within 5-9 business days

Disclaimer:
All orders received before 5 PM U.K time would start printing from the next business day. So the estimated delivery times start from the next day as well. Orders received after 5 PM U.K time (in our internal systems) on a business day or anytime on the weekend will begin printing the second to next business day. For example, an order placed at 11 AM today will begin printing tomorrow, whereas an order placed at 9 PM tonight will begin printing the day after tomorrow.


Unfortunately, due to several restrictions, we are unable to ship to the following countries:

  1. Afghanistan
  2. American Samoa
  3. Belarus
  4. Brunei Darussalam
  5. Central African Republic
  6. The Democratic Republic of Congo
  7. Eritrea
  8. Guinea-bissau
  9. Iran
  10. Lebanon
  11. Libiya Arab Jamahriya
  12. Somalia
  13. Sudan
  14. Russian Federation
  15. Syrian Arab Republic
  16. Ukraine
  17. Venezuela
What is custom duty/charge? Chevron down icon Chevron up icon

Customs duty are charges levied on goods when they cross international borders. It is a tax that is imposed on imported goods. These duties are charged by special authorities and bodies created by local governments and are meant to protect local industries, economies, and businesses.

Do I have to pay customs charges for the print book order? Chevron down icon Chevron up icon

The orders shipped to the countries that are listed under EU27 will not bear custom charges. They are paid by Packt as part of the order.

List of EU27 countries: www.gov.uk/eu-eea:

A custom duty or localized taxes may be applicable on the shipment and would be charged by the recipient country outside of the EU27 which should be paid by the customer and these duties are not included in the shipping charges been charged on the order.

How do I know my custom duty charges? Chevron down icon Chevron up icon

The amount of duty payable varies greatly depending on the imported goods, the country of origin and several other factors like the total invoice amount or dimensions like weight, and other such criteria applicable in your country.

For example:

  • If you live in Mexico, and the declared value of your ordered items is over $ 50, for you to receive a package, you will have to pay additional import tax of 19% which will be $ 9.50 to the courier service.
  • Whereas if you live in Turkey, and the declared value of your ordered items is over € 22, for you to receive a package, you will have to pay additional import tax of 18% which will be € 3.96 to the courier service.
How can I cancel my order? Chevron down icon Chevron up icon

Cancellation Policy for Published Printed Books:

You can cancel any order within 1 hour of placing the order. Simply contact customercare@packt.com with your order details or payment transaction id. If your order has already started the shipment process, we will do our best to stop it. However, if it is already on the way to you then when you receive it, you can contact us at customercare@packt.com using the returns and refund process.

Please understand that Packt Publishing cannot provide refunds or cancel any order except for the cases described in our Return Policy (i.e. Packt Publishing agrees to replace your printed book because it arrives damaged or material defect in book), Packt Publishing will not accept returns.

What is your returns and refunds policy? Chevron down icon Chevron up icon

Return Policy:

We want you to be happy with your purchase from Packtpub.com. We will not hassle you with returning print books to us. If the print book you receive from us is incorrect, damaged, doesn't work or is unacceptably late, please contact Customer Relations Team on customercare@packt.com with the order number and issue details as explained below:

  1. If you ordered (eBook, Video or Print Book) incorrectly or accidentally, please contact Customer Relations Team on customercare@packt.com within one hour of placing the order and we will replace/refund you the item cost.
  2. Sadly, if your eBook or Video file is faulty or a fault occurs during the eBook or Video being made available to you, i.e. during download then you should contact Customer Relations Team within 14 days of purchase on customercare@packt.com who will be able to resolve this issue for you.
  3. You will have a choice of replacement or refund of the problem items.(damaged, defective or incorrect)
  4. Once Customer Care Team confirms that you will be refunded, you should receive the refund within 10 to 12 working days.
  5. If you are only requesting a refund of one book from a multiple order, then we will refund you the appropriate single item.
  6. Where the items were shipped under a free shipping offer, there will be no shipping costs to refund.

On the off chance your printed book arrives damaged, with book material defect, contact our Customer Relation Team on customercare@packt.com within 14 days of receipt of the book with appropriate evidence of damage and we will work with you to secure a replacement copy, if necessary. Please note that each printed book you order from us is individually made by Packt's professional book-printing partner which is on a print-on-demand basis.

What tax is charged? Chevron down icon Chevron up icon

Currently, no tax is charged on the purchase of any print book (subject to change based on the laws and regulations). A localized VAT fee is charged only to our European and UK customers on eBooks, Video and subscriptions that they buy. GST is charged to Indian customers for eBooks and video purchases.

What payment methods can I use? Chevron down icon Chevron up icon

You can pay with the following card types:

  1. Visa Debit
  2. Visa Credit
  3. MasterCard
  4. PayPal
What is the delivery time and cost of print books? Chevron down icon Chevron up icon

Shipping Details

USA:

'

Economy: Delivery to most addresses in the US within 10-15 business days

Premium: Trackable Delivery to most addresses in the US within 3-8 business days

UK:

Economy: Delivery to most addresses in the U.K. within 7-9 business days.
Shipments are not trackable

Premium: Trackable delivery to most addresses in the U.K. within 3-4 business days!
Add one extra business day for deliveries to Northern Ireland and Scottish Highlands and islands

EU:

Premium: Trackable delivery to most EU destinations within 4-9 business days.

Australia:

Economy: Can deliver to P. O. Boxes and private residences.
Trackable service with delivery to addresses in Australia only.
Delivery time ranges from 7-9 business days for VIC and 8-10 business days for Interstate metro
Delivery time is up to 15 business days for remote areas of WA, NT & QLD.

Premium: Delivery to addresses in Australia only
Trackable delivery to most P. O. Boxes and private residences in Australia within 4-5 days based on the distance to a destination following dispatch.

India:

Premium: Delivery to most Indian addresses within 5-6 business days

Rest of the World:

Premium: Countries in the American continent: Trackable delivery to most countries within 4-7 business days

Asia:

Premium: Delivery to most Asian addresses within 5-9 business days

Disclaimer:
All orders received before 5 PM U.K time would start printing from the next business day. So the estimated delivery times start from the next day as well. Orders received after 5 PM U.K time (in our internal systems) on a business day or anytime on the weekend will begin printing the second to next business day. For example, an order placed at 11 AM today will begin printing tomorrow, whereas an order placed at 9 PM tonight will begin printing the day after tomorrow.


Unfortunately, due to several restrictions, we are unable to ship to the following countries:

  1. Afghanistan
  2. American Samoa
  3. Belarus
  4. Brunei Darussalam
  5. Central African Republic
  6. The Democratic Republic of Congo
  7. Eritrea
  8. Guinea-bissau
  9. Iran
  10. Lebanon
  11. Libiya Arab Jamahriya
  12. Somalia
  13. Sudan
  14. Russian Federation
  15. Syrian Arab Republic
  16. Ukraine
  17. Venezuela