Compiling to machine language doesn't automatically make code fast, neither does compiling to C make it automatically slow(er).
There is very little about C that makes this inherently slow, and almost all of the stuff one has to do to make it fast has to be done when targeting machine code as well.
On the other hand the C compiler does lots of things very well that would otherwise have to be coded by hand, like register allocation, interfacing with existing code, and, yes, portability.
There is very little about C that makes this inherently slow, and almost all of the stuff one has to do to make it fast has to be done when targeting machine code as well.
On the other hand the C compiler does lots of things very well that would otherwise have to be coded by hand, like register allocation, interfacing with existing code, and, yes, portability.