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

Checking the source with the Clang Static Analyzer

The Clang Static Analyzer is a tool that performs additional checking on C, C++, and Objective C source code. The checks performed by the static analyzer are more thorough than the checks the compiler performs. They are also more costly in terms of time and required resources. The static analyzer has a set of checkers that check for certain bugs.

The tool performs a symbolic interpretation of the source code that looks at all the code paths through an application and derives constraints on the values used in the application from it. Symbolic interpretation is a common technique used in compilers, for example, to identify constant values. In the context of the static analyzer, the checkers are applied to the derived values.

For example, if the divisor of a division is 0, then the static analyzer warns about it. We can check this with the following example stored in the div.c file:

int divbyzero(int a, int b) { return a / b...