Why do the target-specific function declarations in GCC source use K&R style instead of prototypes?

Question

I've been studying the GCC source code and I noticed that most (if not all) target-specific source code files (like arm.c for example) use the old K&R function style.

Is there any particular reason for this? Backward compatibility? Portability?

Answer 1

So that you can compile gcc on a system with non-GNU, and potentially really old, compiler, to just get a better compiler on this very system.