Book Image

LLVM Essentials

By : Mayur Pandey, Suyog Sarda, David Farago
Book Image

LLVM Essentials

By: Mayur Pandey, Suyog Sarda, David Farago

Overview of this book

LLVM is currently the point of interest for many firms, and has a very active open source community. It provides us with a compiler infrastructure that can be used to write a compiler for a language. It provides us with a set of reusable libraries that can be used to optimize code, and a target-independent code generator to generate code for different backends. It also provides us with a lot of other utility tools that can be easily integrated into compiler projects. This book details how you can use the LLVM compiler infrastructure libraries effectively, and will enable you to design your own custom compiler with LLVM in a snap. We start with the basics, where you’ll get to know all about LLVM. We then cover how you can use LLVM library calls to emit intermediate representation (IR) of simple and complex high-level language paradigms. Moving on, we show you how to implement optimizations at different levels, write an optimization pass, generate code that is independent of a target, and then map the code generated to a backend. The book also walks you through CLANG, IR to IR transformations, advanced IR block transformations, and target machines. By the end of this book, you’ll be able to easily utilize the LLVM libraries in your own projects.
Table of Contents (14 chapters)
LLVM Essentials
About the Authors
About the Reviewer


In this chapter, you learned how to create simple LLVM IR using rich libraries provided by LLVM. Remember that LLVM IR is an intermediate representation. The high-level programming languages are converted to LLVM IR using the custom parser, which breaks down the code into atomic pieces such as variables, functions, function return type, function arguments, if-else conditions, loops, pointers, array, and so on. These atomic elements can be stored into custom data structures and then those data structures can be used to emit LLVM IR, as demonstrated in this chapter.

In the parser phase, syntactic analysis can be done, while lexical analysis and type checking can be done in an intermediate stage after parsing and before emitting IR.

In practical usage, one would hardly find the IR being emitted in a hard-coded way as demonstrated in this chapter. Instead, a language is parsed and represented in an Abstract Syntax Tree. The tree is then used to emit LLVM IR with the help of the LLVM library...