Book Image

LLVM Techniques, Tips, and Best Practices Clang and Middle-End Libraries

By : Min-Yih Hsu
Book Image

LLVM Techniques, Tips, and Best Practices Clang and Middle-End Libraries

By: Min-Yih Hsu

Overview of this book

Every programmer or engineer, at some point in their career, works with compilers to optimize their applications. Compilers convert a high-level programming language into low-level machine-executable code. LLVM provides the infrastructure, reusable libraries, and tools needed for developers to build their own compilers. With LLVM’s extensive set of tooling, you can effectively generate code for different backends as well as optimize them. In this book, you’ll explore the LLVM compiler infrastructure and understand how to use it to solve different problems. You’ll start by looking at the structure and design philosophy of important components of LLVM and gradually move on to using Clang libraries to build tools that help you analyze high-level source code. As you advance, the book will show you how to process LLVM IR – a powerful way to transform and optimize the source program for various purposes. Equipped with this knowledge, you’ll be able to leverage LLVM and Clang to create a wide range of useful programming language tools, including compilers, interpreters, IDEs, and source code analyzers. By the end of this LLVM book, you’ll have developed the skills to create powerful tools using the LLVM framework to overcome different real-world challenges.
Table of Contents (18 chapters)
1
Section 1: Build System and LLVM-Specific Tooling
6
Section 2: Frontend Development
11
Section 3: "Middle-End" Development

Learning about AST in Clang

In this section, we are going to learn about Clang's AST in-memory representation and its essential API usage. The first part of this section will provide you with a high-level overview of Clang AST's hierarchy; the second part will focus on a more specific topic regarding type representation in Clang AST; and the final part will show you the basic usage of AST matcher, which is extremely useful when you're writing an AST plugin.

In-memory structure of Clang AST

The in-memory representation of AST in Clang is organized in a hierarchy structure that resembles the syntax structure of C-family language programs. Starting from the top-most level, there are two classes worth mentioning:

  • TranslationUnitDecl: This class represents an input source file, also called a translation unit (most of the time). It contains all the top-level declarations – global variables, classes, and functions, to name a few – as its children...