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Optimize Your Code with LLVM: A Multiplication to Shift Conversion Pass Tutorial

Are you ready to take your compiler optimization skills to the next level? Our team has created an exciting new tutorial that demonstrates how to create a custom LLVM optimization pass. This tutorial builds on our previous LLVM pass plugin guide, diving deeper into practical code optimization techniques.

The Power of Custom LLVM Passes

LLVM’s extensibility allows developers to create custom optimization passes tailored to specific needs. In this tutorial, we showcase a practical example: converting multiplication by constant powers of two into more efficient left shift operations.

What You’ll Learn

Our GitHub tutorial walks you through creating an LLVM pass plugin called “MultiplicationShifts”. This optimization pass will:

  1. Identify multiplication operations in the code
  2. Check if the multiplier is a constant power of two
  3. Replace eligible multiplications with equivalent left shift operations

This optimization can lead to more efficient code execution, as shift operations are typically faster than multiplication on many processors.

Tutorial Highlights

The tutorial covers several advanced aspects of LLVM pass plugin development:

  • Writing a more complex pass that modifies code
  • Using LLVM’s IRBuilder to create new instructions
  • Deleting an instruction and replacing its uses with the new instruction
  • Creating a printer pass to provide feedback on the optimization process
  • Running and verifying the optimization using LLVM tools like opt, llvm-dis, and llvm-diff

Each step is explained in detail, with code snippets and command-line instructions to guide you through the process.

Who Is This For?

This tutorial is perfect for:

  • Developers who have completed our basic LLVM plugin tutorial and want to go further
  • Compiler enthusiasts interested in practical optimization techniques
  • Software engineers looking to improve code performance at the compiler level
  • Students and researchers in the field of program analysis and optimization

While some familiarity with LLVM is helpful, our step-by-step guide will help you navigate the process even if you’re relatively new to LLVM development.

Ready to Optimize?

We invite you to check out the full tutorial on our GitHub repository. Whether you’re looking to enhance your compiler skills, optimize specific code patterns, or explore the depths of LLVM, this guide will provide you with valuable insights and practical experience.

GitHub Tutorial 

Explore the code

Get ready to transform your code and boost its performance with your very own LLVM optimization pass!


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