I'm not sure what you're talking about with respect to the C compiler. C compilers are the fastest around even before being paralllelized - and they can be.
C parsing is rather slow due to the preprocessor (also: huuuge include files) and due to context-dependent syntax (need symbol table). And compiling itself need not be slow, but the popular compilers are not exactly super fast even with -O0. LLVM in particular has a reputation of being somewhat bloated. And finally, due to common practice of using a standard object file format, which is slow to link (at least with common tools), the whole build experience is not exactly blazingly fast.
With clang/gcc/msvc, I think I'm more in the ballpark of 3K-30K lines/sec (-O0, 100-1000 lines/file, not counting basic std* includes).
gold is pretty fast. I don't have a source but those numbers seem very off to me. C compilers are fast. C++ much less so, but C++ is a different language.
I tried to follow gold's author's series on linkers once but gave up. Now that I've written an ELF-64 writer and know a little more about linking I should give it another shot. In any case, I think I've heard of still faster linkers than gold, and at the time I also found gold's object oriented architecture (as it was described in the series) questionable.
