The LLVM Compiler Infrastructure

The LLVM Project is a collection of modular and reusable compiler and toolchain technologies. Despite its name, LLVM has little to do with traditional virtual machines, though it does provide helpful libraries that can be used to build them.

LLVM began as a research project at the University of Illinois, with the goal of providing a modern, SSA-based compilation strategy capable of supporting both static and dynamic compilation of arbitrary programming languages. Since then, LLVM has grown to be an umbrella project consisting of a number of different subprojects, many of which are being used in production by a wide variety of commercial and open source projects as well as being widely used in academic research. Code in the LLVM project is licensed under the "UIUC" BSD-Style license.

Among the sub-projects of LLVM are:

  • The LLVM Core libraries provide a modern source- and target-independent optimizer, along with code generation support for many popular CPUs (as well as some less common ones!) These libraries are built around a well specified code representation known as the LLVM intermediate representation ("LLVM IR").

  • Clang is an "LLVM native" C/C++/Objective-C compiler, which aims to deliver amazingly fast compiles, extremely useful error and warning messages and to provide a platform for building great source level tools.

  • The polly project implements a suite of cache-locality optimizations as well as auto-parallelism and vectorization using a polyhedral model.

  • And many others!

In addition to official subprojects of LLVM, there are a broad variety of other projects that use components of LLVM for various tasks. A major strength of LLVM is its versatility, flexibility, and reusability, which is why it is being used for such a wide variety of different tasks: everything from doing light-weight JIT compiles of embedded languages like Lua to compiling Fortran code for massive super computers.

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