Just to be clear, I think this is a very small disadvantage. GCC and therefore C/C++ supports some old stuff like SuperH, Intel Itanium, PA-RISC and a bunch of microcontroller archs that LLVM does not.

However, there is now a Rust codegen plugin for GCC, so even this disadvantage is now basically moot.

Rewrite all the things!

The GCC backend is fairly complete but still does not support everything.