a modern C compiler on full optimization produces object much faster than any sane, maintainable assembly source.
Do you have any sources on this? I did a quick google but nothing aside from anecdotes turned up (my google-fu is absolutely abysmal, though).
From experience I know that a well-trained, well-weathered assembly hacker can generate code faster than the compiler. (The programmer who knows their code will produce much better code than a compiler.) But alas, that's still anecdotal.
I read somewhere (Can't remember where