What is "llvm"

The LLVM compiler infrastructure project (formerly Low Level Virtual Machine) is a "collection of modular and reusable compiler and toolchain technologies" used to develop compiler front ends and back ends.

LLVM is written in C++ and is designed for compile-time, link-time, run-time, and "idle-time" optimization of programs written in arbitrary programming languages. Originally implemented for C and C++, the language-agnostic design of LLVM has since spawned a wide variety of front ends: languages with compilers that use LLVM include ActionScript, Ada, C#, Common Lisp, Crystal, D, Delphi, Fortran, OpenGL Shading Language, Halide, Haskell, Java bytecode, Julia, Lua, Objective-C, Pony, Python, R, Ruby, Rust, Scala, and Swift.

The LLVM project started in 2000 at the University of Illinois at Urbana–Champaign, under the direction of Vikram Adve and Chris Lattner. LLVM was originally developed as a research infrastructure to investigate dynamic compilation techniques for static and dynamic programming languages. LLVM was released under the University of Illinois/NCSA Open Source License, a permissive free software licence. In 2005, Apple Inc. hired Lattner and formed a team to work on the LLVM system for various uses within Apple's development systems. LLVM is an integral part of Apple's latest development tools for OS X and iOS. Since 2013, Sony has been using LLVM's primary front end Clang compiler in the software development kit (SDK) of its PS4 console.

The name LLVM was originally an initialism for Low Level Virtual Machine, but this became increasingly less apt as LLVM became an "umbrella project" that included a variety of other compiler and low-level tool technologies, so the project abandoned the initialism. Now, LLVM is a brand that applies to the LLVM umbrella project, the LLVM intermediate representation (IR), the LLVM debugger, the LLVM C++ Standard Library, etc. LLVM is administered by the LLVM Foundation. Its president is compiler engineer Tanya Lattner.

The Association for Computing Machinery presented Adve, Lattner, and Evan Cheng with the 2012 ACM Software System Award for LLVM.