> as fast as C
I mean, it actually is C, since the code is transpiled to C.
I mean, it actually is C, since the code is transpiled to C.
Or consider: Every native-compiled language ends up as machine code, which is equivalent to assembly language, but for most (perhaps all) it would be grossly misleading to say "as fast as assembler".
(A neat tool in one's toolbox, of course. But just transpiling to C does not get one as fast as C.)
Your comparison to machine code (or human readable assembly code) is less useful in that such a statement means very little until one knows how said machine code is being produced (e.g., manually, from a IR, etc.).
That a language is compiled to C does not mean that its compiler is going to be able to produce a C program that's as good as a that well-written C equivalent. (A relatively obvious example would be a compiler that introduces a heavy runtime, and doesn't give the C compiler enough information for it to get rid of the runtime)
It's the same with assembly code: that a compiler produces assembly does not mean the resulting program is fast.
That’s your interpretation, which is fine, but the objective meaning stands. Even the idea of “well-written C” is, in my experience, fairly subjective amongst C programmers.
That some particular C program exists that is at least as slow as a program in some other language is always true, trivially, and so is not a good interpretation of "as fast as C" regardless of its objectivity.
Where do you see me claiming otherwise?
> At the simplest level, the compiled code could add a bunch of unnecessary function calls and pointers and other forms of indirection that wouldn't be present in hand-written C.
Again, why are you telling me this? Please quote where I claimed otherwise.
> But for a more extreme example, you could also compile an interpreter or VM to C, and it would still be much slower than the equivalent hand-written C code.
The more that I read your response, the more that it seems that you’re debating yourself, because I’m not sure why you’re telling me this. You started your response by telling me that I’m “missing the point” when, in reality, you seem to have not even read my point. My main point was the following:
> If the code from which the resulting machine code is compiled is C, then it’s objectively “as fast as C” […] your resulting program will perform as fast as a C compiler [worth its salt] can get you.
This is true. I made no claims re efficiency; “as fast as C” and “as fast as efficient hand-written C” aren’t interchangeable claims. Forgive me for not assuming efficiency, because I’ve seen a good amount of inefficient hand-written C code in my years.
> This is why "as fast as C" typically refers to normal, hand-written C code—even though there is no formal definition for what "normal C" looks like, it's still a useful description.
Says who though? I’m professionally experienced in C, and as is very clear by this discussion, it’s down to individual interpretations.
But that doesn't at all follow from compiling to C. I gave one example above; here's another. Perhaps my programming language has arbitrary-length integers and the C code it produces for a simple loop looks something like this:
bignum_t i = bignum_from_int(0);
bignum_t x = bignum_from_int(0);
while (i < bignum_from_int(1000000)) {
bignum_add_in_place(x, bignum_bitand(i, bignum_from_int(1)));
}
Being as fast as C is not about using C as an intermediate language but having data structures and control flow that resemble what C compiler have been optimized for.
Case in point, Haskell GHC is capable of outputting C code but the algorithm will not get C performance (or Haskell performance without this intermediate C representation).
I've been trying to find out if I can take the generated C code that nim produces and, for example, compile it on some exotic architecture (say an ancient solaris/sparc system or some aix/power thing, or some mips microcontroller with linux) however I can't find any examples of people doing this...
Is it possible? Or should I abandon hope and continue writing C for these platforms? :}
And for CPUs - https://github.com/nim-lang/csources/blob/master/build.sh#L1...
Give it a try :)
[0]https://stackoverflow.com/questions/29956898/how-do-i-get-th...