Book Image

Learn LLVM 12

By : Kai Nacke
Book Image

Learn LLVM 12

By: Kai Nacke

Overview of this book

LLVM was built to bridge the gap between compiler textbooks and actual compiler development. It provides a modular codebase and advanced tools which help developers to build compilers easily. This book provides a practical introduction to LLVM, gradually helping you navigate through complex scenarios with ease when it comes to building and working with compilers. You’ll start by configuring, building, and installing LLVM libraries, tools, and external projects. Next, the book will introduce you to LLVM design and how it works in practice during each LLVM compiler stage: frontend, optimizer, and backend. Using a subset of a real programming language as an example, you will then learn how to develop a frontend and generate LLVM IR, hand it over to the optimization pipeline, and generate machine code from it. Later chapters will show you how to extend LLVM with a new pass and how instruction selection in LLVM works. You’ll also focus on Just-in-Time compilation issues and the current state of JIT-compilation support that LLVM provides, before finally going on to understand how to develop a new backend for LLVM. By the end of this LLVM book, you will have gained real-world experience in working with the LLVM compiler development framework with the help of hands-on examples and source code snippets.
Table of Contents (17 chapters)
Section 1 – The Basics of Compiler Construction with LLVM
Section 2 – From Source to Machine Code Generation
Section 3 –Taking LLVM to the Next Level

Chapter 12: Create Your Own Backend

LLVM has a very flexible architecture. You can also add a new target backend to it. The core of a backend is the target description, from which most of the code is generated. However, it is not yet possible to generate a complete backend, and implementing the calling convention requires manually written code. In this chapter, we will learn how to add support for a historical CPU.

In this chapter, we will cover the following:

  • Setting the stage for a new backend introduces you to the M88k CPU architecture and shows you where to find the information you need.
  • Adding the new architecture to the Triple class teaches you how to make LLVM aware of a new CPU architecture.
  • In Extending the ELF file format definition in LLVM, you will add support for the M88k-specific relocations to the libraries and tools that handle ELD object files.
  • In Creating the target description, you will develop all the parts of the target description in the...