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

Building blocks of a compiler

After computers became available in the middle of the last century, it quickly became apparent that a more abstract language than assembler would be useful for programming. As early as 1957, Fortran was the first available higher programming language. Since then, thousands of programming languages have been developed. It turns out that all compilers must solve the same tasks and that the implementation of a compiler is best structured according to these tasks.

At the highest level, a compiler consists of two parts: the frontend and the backend. The frontend is responsible for language-specific tasks. It reads a source file and computes a semantic analyzed representation of it, usually an annotated abstract syntax tree (AST). The backend creates optimized machine code from the frontend's result. The motivation behind there being a distinction between the frontend and the backend is reusability. Let's assume that the interface between the frontend...