LLVM (Low Level Virtual Machine)

LLVM can provide the middle layers of a complete compiler system, taking intermediate form (IF) code from a compiler and emitting an optimized IF. This new IF can then be converted and linked into machine-dependent assembly code for a target platform. LLVM can accept the IF from the GCC toolchain, allowing it to be used with a wide array of extant compilers written for that project.

http://llvm.org/

clang ( new C, C++, Objective C and Objective C++ front-end for the LLVM compiler )

http://clang.llvm.org/

OdinMonkey

an Asm.js optimising module for Firefox's JavaScript engine

Asm.js is a subset of JavaScript which has been selected firstly to route around the things that tend to slow down Java, such as boxed floating point numbers (Statically-typed languages)

Emscripten is an open source LLVM to JavaScript compiler.

C/C++    =>    LLVM    =>    Emscripten    =>    JavaScript