执行时间有差异吗？

Question

Consider this piece of code:

class A {
  void methodX() {
  // snip (1 liner function)
  }
}

class B {
  void methodX() {
   // same -code
  }
}

Now other way i can go is, I have a class(AppManager) most of whose members are static, (from legacy code, don't suggest me singleton ;))

class AppManager {
  public:
  static void methodX(){
   // same-code
  }
}

Which one should be preferred? As both are inlined, there shouldn't be a runtime difference, right?
Which form is more cleaner?

Answer 1

Now first of all, this is a concern so minuscule that you would never have to worry about it unless the functions are called thousands of times per frame (and you're doing something where "frames" matter).

Second, IF they are inlined, the code will be (hopefully) optimized so much that there is no sign whatsoever of the function being non-static. It would be identical.

Even if they were not inlined, the difference would be minor. The ABI would put the "this" pointer into a register (or the stack), which it wouldn't do in a static function, but again, the net result would be almost not measurable.

Bottom line - write your code in the cleanest possible way. Performance is not a concern at this point.

Answer 2

In my opinion Inline way would be faster. because inline functions are replaced in code in compile time and therefor there is no need to save registers, make a function call and then return again. but when you call a static function it's just a function call and it has much overhead than the inline one.

Answer 3

I think that this is most common optimisation problem. At first level when you writing a code you try every single trick that would help compiler so if compiler can not optimise code well, you already have. This is wrong. What are you looking for in first stage of optimisation during writing code is just clean and understandable code, design and structure. That will make by far better code, that "optimised" by hand.

Rule is:
If you do not have resources to benchmark code, rewrite it and spend lot of time for optimisation than you do not need optimised code. In most cases it is hard to gain any speed boost whit any kind optimisation, if you structured your code well.