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

Adding the new architecture to the Triple class

An instance of the Triple class represents the target platform LLVM is producing code for. To support a new architecture, the first task is to extend the Triple class. In the llvm/include/llvm/ADT/Triple.h file, you add a member to the ArchType enumeration and a new predicate:

class Triple {
  enum ArchType {
  // Many more members
    m88k,           // M88000 (big endian): m88k
  /// Tests whether the target is M88k.
  bool isM88k() const {
    return getArch() == Triple::m88k;
// Many more methods

Inside the llvm/lib/Support/Triple.cpp file, there are numerous methods that use the ArchType enumeration. You need to extend all of them; for example, in the getArchTypeName() method, you need to add a new case statement:

  switch (Kind) {
// Many...