LLVM is a collection of libraries and tools that make it easy to build compilers, optimizers, just-in-time code generators, and many other compiler-related programs. LLVM uses a single, language-independent virtual instruction set both as an offline code representation (to communicate code between compiler phases and to run-time systems) and as the compiler internal representation (to analyze and transform programs). This persistent code representation allows a common set of sophisticated compiler techniques to be applied at compile-time, link-time, install-time, run-time, or "idle-time" (between program runs).