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)
1
Section 1 – The Basics of Compiler Construction with LLVM
5
Section 2 – From Source to Machine Code Generation
11
Section 3 –Taking LLVM to the Next Level

Getting the application binary interface right

With the latest addition of arrays and records to the code generator, you may notice that sometimes the generated code does not execute as expected. The reason is that we have ignored the calling conventions of the platform so far. Each platform defines its own rules for how one function can call another function in the same program or a library. These rules are summarized in the application binary interface (ABI) documentation. Typical information includes the following:

  • Are machine registers used for parameter passing? If yes, which?
  • How are aggregates such as arrays and structs passed to a function?
  • How are return values handled?

There is a wide variety of rules in use. On some platforms, aggregates are always passed indirectly, meaning that a copy of the aggregate is placed on the stack and only a pointer to the copy is passed as a parameter. On other platforms, a small aggregate (say 128- or 256-bit-wide) is...