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


In this chapter, you learned how to develop a new backend target for LLVM. You first collected the required documentation and made LLVM aware of the new architecture by enhancing the Triple class. The documentation also includes the relocation definition for the ELF file format, and you added support for that to LLVM.

You learned about the different parts the target description contains, and using the C++ source generated from it, you learned how to implement an instruction selection. For outputting the generated code, you developed an assembler printer and learned which support classes are needed to write to an object file. You also learned how to add support for disassembling, which is used to turn an object file back into assembler text. Lastly, you extended the build system to include the new target in the build.

You are now equipped with everything you need to use LLVM in creative ways in your own projects. The LLVM ecosystem is very active, and new features are...