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

Targeting a different CPU architecture

Today, many small computers such as the Raspberry Pi are in use and have only limited resources. Running a compiler on such a computer is often not possible or takes too much runtime. Hence, a common requirement for a compiler is to generate code for a different CPU architecture. The whole process of creating an executable is called cross-compiling. In the previous section, you created a small example application based on the LLVM libraries. Now we will take this application and compile it for a different target.

With cross-compiling, there are two systems involved: the compiler runs on the host system and produces code for the target system. To denote the systems, the so-called triple is used. This is a configuration string that usually consists of the CPU architecture, the vendor, and the operating system. More information about the environment is often added. For example, the triple x86_64-pc-win32 is used for a Windows system running on...