C/C++: is GOTO faster than WHILE and FOR?

Question

I know, that everybody hates GOTO and nobody recommends it. But that's not the point. I just want to know, which code is the fastest:

1. the goto loop

   int i=3;
   loop:
   printf("something");
   if(--i) goto loop;
   

2. the while loop

   int i=3;
   while(i--) {
       printf("something");
   }
   

3. the for loop

   for(int i=3; i; i--) {
       printf("something");
   }
   

Answer 1

Write short programs, then do this:

gcc -S -O2 p1.c 
gcc -S -O2 p2.c 
gcc -S -O2 p3.c 

Analyze the output and see if there's any difference. Be sure to introduce some level of unpredictability such that the compiler doesn't optimize the program away to nothing.

Compilers do a great job of optimizing these trivial concerns. I'd suggest not to worry about it, and instead focus on what makes you more productive as a programmer.

Speed and efficiency is a great thing to worry about it, but 99% of the time that involves using proper data structures and algorithms... not worrying about whether a for is faster than a while or a goto, etc.