Chapter 1: Saving Resources When Building LLVM

LLVM is the state-of-the-art compiler optimization and code generation framework adopted by many amazing industrial and academic projects, such as the Just-In-Time (JIT) compiler in JavaScript engines and machine learning (ML) frameworks. It is a useful toolbox for building programming languages and binary file tools. However, despite the project's robustness, its learning resources are scattered, and it doesn't have the best documentation either. Due to this, it has a pretty steep learning curve, even for developers with some LLVM experience. This book aims to tackle these issues by providing you with knowledge of common and important domains in LLVM in a pragmatic fashion – showing you some useful engineering tips, pointing out lesser-known but handy features, and illustrating useful examples.

As an LLVM developer, building LLVM from source has always been the first thing you should do. Given the scale of LLVM nowadays, this task can take hours to finish. Even worse, rebuilding the project to reflect changes might also take a long time and hinder your productivity. Therefore, it's crucial to know how to use the right tools and how to find the best build configurations for your project for the sake of saving various resources, especially your precious time.

In this chapter, we are going to cover the following topics:

• Cutting down building resources with better tooling
• Saving building resources by tweaking CMake arguments
• Learning how to use GN, an alternative LLVM build system, and its pros and cons