LLVM

Little over a year ago, Apple announced at WWDC 2015 the ability to embed bitcode in Mach-O files. Bitcode is the intermediate representation used by the LLVM compiler and contains all the information required to recompile an application. Having the bitcode present, in addition to machine code, Apple can further optimize applications by compiling and linking specifically for the user’s target device. This is one approach to app thinning, which aims to achieve smaller binaries and therefore more free space on your iDevice. It will most likely replace Apple’s current approach, where a developer uploads a fat binary to the App Store, which contains machine code for each target architecture. ...

Clang is everywhere; It is the core of my favorite Vim plugin YouCompleteMe, it recently got supported by Microsoft Visual Studio, it is mentioned in numerous episodes of CppCast and it powers the excellent clang formatter. Naturally, I wanted to get a better understanding of how the clang front end works under the hood. Clang Front End & AST Clang is a C language family front end for LLVM. In compiler design, a front end takes care of the analysis part, which means breaking up the source code into pieces according to a grammatical structure. The result is an intermediate representation which is transformed in a target program by the back end, called synthesis. Optionally, there is an intermediate step between the front- and back end for optimization. ...