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

Performing semantic analysis

The parser that we constructed in the previous section only checks the syntax of the input. The next step is to add the ability to perform semantic analysis. In the calc example in the previous chapter, the parser constructed an AST. In a separate phase, the semantic analyzer worked on this tree. This approach can always be used. In this section, we will use a slightly different approach and intertwine the parser and the semantic analyzer more.

These are some of the tasks a semantic analyzer must perform:

  • For each declaration, the semantic analyzer must check if the used name has not been declared elsewhere already.
  • For each occurrence of a name in an expression or statement, the semantic analyzer must check that the name is declared and that the desired use fits the declaration.
  • For each expression, the semantic analyzer must compute the resulting type. It is also necessary to compute if the expression is constant and if so, which value...