llvm/llvm-project

Analysis updated 2026-06-20

★ 38,195LLVMAudience · researcherComplexity · 5/5LicenseSetup · hard

Mindmap

mindmap
  root((LLVM Project))
    Components
      Clang frontend
      LLVM optimizer
      LLD linker
      libc++ stdlib
    What it does
      Compile C and C++
      Optimize programs
      Generate machine code
    Tech Stack
      C++
      LLVM IR
      CMake
    Use Cases
      New languages
      Compiler research
      Cross-compilation
    Language Users
      Rust
      Swift
      Julia

mindmap root((LLVM Project)) Components Clang frontend LLVM optimizer LLD linker libc++ stdlib What it does Compile C and C++ Optimize programs Generate machine code Tech Stack C++ LLVM IR CMake Use Cases New languages Compiler research Cross-compilation Language Users Rust Swift Julia

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What do people build with it?

USE CASE 1

Build a new programming language by writing a frontend that compiles to LLVM IR and letting LLVM handle optimization and code generation.

USE CASE 2

Contribute to or study the internals of the Clang C/C++ compiler, including its parser, AST, and diagnostics.

USE CASE 3

Use LLD as a faster drop-in replacement for system linkers in a large C++ build pipeline.

USE CASE 4

Cross-compile code for an embedded system or different CPU architecture using LLVM's backend.

What is it built with?

C++LLVM IRCMake

How do you get it running?

Difficulty · hard Time to first run · 1day+

Building from source requires CMake, Ninja, and a C++ compiler, a full build takes significant disk space and compilation time.

Apache 2.0 with LLVM exception, use freely in open-source and commercial projects, including linking without requiring your code to be open-source.

In plain English

The LLVM Project is a large collection of modular, reusable compiler and toolchain technologies. At its core, LLVM provides the infrastructure that makes it possible to build optimizing compilers: a set of libraries and tools for transforming source code into machine code in a way that runs fast and uses memory efficiently. It is the foundation that powers many real-world programming language compilers and runtimes. The project has several major components. LLVM itself is the core optimizer and code generator: it takes programs expressed in a portable intermediate representation (a kind of simplified assembly language that is CPU-independent) and optimizes and translates them into machine code for specific processors. Clang is the C, C++, Objective-C, and Objective-C++ frontend, the part that reads your source code and converts it into LLVM's intermediate form. Other parts of the project include libc++ (a modern implementation of the C++ standard library), LLD (a fast linker that connects compiled object files into a runnable program), and many other tools for analyzing and transforming programs. You would encounter LLVM when working on or studying compilers, building a new programming language, optimizing an existing language's runtime, working on embedded systems that need a cross-compiler, or contributing to languages like Rust, Swift, Julia, or Kotlin that compile through LLVM. Apple uses LLVM as the foundation for the Xcode toolchain, and it is widely used in research and industry. The codebase is primarily written in C++ with some components in LLVM's own assembly language. It is an open-source project hosted as a monorepo on GitHub.

Copy-paste prompts

Prompt 1

I want to build a toy programming language that compiles to native code. Show me how to emit LLVM IR from my AST using the LLVM C++ API and compile it with LLVM.

Prompt 2

How do I build Clang from source using the llvm-project monorepo and use it to compile a C++ project?

Prompt 3

What is LLVM IR and how does it differ from assembly language? Give me an example of a simple C function and its LLVM IR equivalent.

Prompt 4

How do I write an LLVM pass that instruments a C function to count how many times each basic block executes?

Frequently asked questions

What is llvm-project?

A large collection of compiler building blocks, including the Clang C/C++ compiler and the LLVM optimizer, that power many real-world programming languages like Rust, Swift, and Julia.

What language is llvm-project written in?

Mainly LLVM. The stack also includes C++, LLVM IR, CMake.

What license does llvm-project use?

Apache 2.0 with LLVM exception, use freely in open-source and commercial projects, including linking without requiring your code to be open-source.

How hard is llvm-project to set up?

Setup difficulty is rated hard, with roughly 1day+ to a first successful run.

Who is llvm-project for?

Mainly researcher.

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