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

Inserting a scalar into a vector

LLVM also provides the API to emit an instruction, which inserts a scalar into a vector type. Note that this vector is different from an array. A vector type is a simple derived type that represents a vector of elements. Vector types are used when multiple primitive data are operated in parallel using single instruction multiple data (SIMD). A vector type requires a size (number of elements) and an underlying primitive data type. For example, we have a vector Vec that has four integers of i32 type <4 x i32>. Now, we want to insert the values 10, 20, 30, and 40 at 0, 1, 2, and 3 indexes of the vector.

The insertelement instruction takes three arguments. The first argument is a value of vector type. The second operand is a scalar value whose type must equal the element type of the first operand. The third operand is an index indicating the position at which to insert the value. The resultant value is a vector of the same type.

The insertelement instruction...