Book Image

LLVM Techniques, Tips, and Best Practices Clang and Middle-End Libraries

By : Min-Yih Hsu
Book Image

LLVM Techniques, Tips, and Best Practices Clang and Middle-End Libraries

By: Min-Yih Hsu

Overview of this book

Every programmer or engineer, at some point in their career, works with compilers to optimize their applications. Compilers convert a high-level programming language into low-level machine-executable code. LLVM provides the infrastructure, reusable libraries, and tools needed for developers to build their own compilers. With LLVM’s extensive set of tooling, you can effectively generate code for different backends as well as optimize them. In this book, you’ll explore the LLVM compiler infrastructure and understand how to use it to solve different problems. You’ll start by looking at the structure and design philosophy of important components of LLVM and gradually move on to using Clang libraries to build tools that help you analyze high-level source code. As you advance, the book will show you how to process LLVM IR – a powerful way to transform and optimize the source program for various purposes. Equipped with this knowledge, you’ll be able to leverage LLVM and Clang to create a wide range of useful programming language tools, including compilers, interpreters, IDEs, and source code analyzers. By the end of this LLVM book, you’ll have developed the skills to create powerful tools using the LLVM framework to overcome different real-world challenges.
Table of Contents (18 chapters)
1
Section 1: Build System and LLVM-Specific Tooling
6
Section 2: Frontend Development
11
Section 3: "Middle-End" Development

Adding time measurements

LLVM is an enormous software, with hundreds of components working closely together. Its ever-increasing running time is slowly becoming an issue. This affects many use cases that are sensitive to compilation time—for example, the Just-in-Time (JIT) compiler. To diagnose this problem in a systematic way, LLVM provides some useful utilities for profiling the execution time.

Time profiling has always been an important topic in software development. With the running time collected from individual software components, we can spot performance bottlenecks more easily. In this section, we are going to learn about two tools provided by LLVM: the Timer class and the TimeTraceScope class. Let's start with the Timer class first.

Using the Timer class

The Timer class, as suggested by its name, can measure the execution time of a code region. Here is an example of this:

#include "llvm/Support/Timer.h"
…
Timer T("MyTimer&quot...