The most noticeable design decision of LLVM is its segregation between backend and frontend as two separate projects, LLVM core and Clang. LLVM started as a set of tools orbiting around the LLVM intermediate representation (IR) and depended on a hacked GCC to translate high-level language programs to its particular IR, stored in bitcode files. Bitcode is a term coined as a parody of Java bytecode files. An important milestone of the LLVM project happened when Clang appeared as the first frontend specifically designed by the LLVM team, bringing with it the same level of quality, clear documentation, and library organization as the core LLVM. It is not only able to convert C and C++ programs into LLVM IR but also to supervise the entire compilation process as a flexible compiler driver that strives to stay compatible with GCC.

We will henceforth refer to Clang as a frontend program rather than a driver, responsible for translating C and C++ programs to the LLVM IR....