Well, link time optimization does this for C code in principle. It is fairly new in gcc and clang so it is not clear what it buys you in real world cases. A lot

Well, link time optimization does this for C code in principle. It is fairly new in gcc and clang so it is not clear what it buys you in real world cases. A lot of code cant be compiled out because it is hard to prove it cannot be called. I plan to experiment with LTO and compiling a kernel and an application together at some point to see how it goes.