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, D, Fortran, OpenGL Shading Language, Haskell, Java bytecode, Julia, Lua, Objective-C, Python, R, Ruby, Rust, Scala, and Swift.