Is there a performance difference between i++ and ++i in C++?

Question

We have the question is there a performance difference between i++ and ++i in C?

What\'s the answer for C++?

Answer 1

Both are as fast ;) If you want it is the same calculation for the processor, it's just the order in which it is done that differ.

For example, the following code :

#include 

int main()
{
    int a = 0;
    a++;
    int b = 0;
    ++b;
    return 0;
}

Produce the following assembly :

 0x0000000100000f24 : push   %rbp
 0x0000000100000f25 : mov    %rsp,%rbp
 0x0000000100000f28 : movl   $0x0,-0x4(%rbp)
 0x0000000100000f2f :    incl   -0x4(%rbp)
 0x0000000100000f32 :    movl   $0x0,-0x8(%rbp)
 0x0000000100000f39 :    incl   -0x8(%rbp)
 0x0000000100000f3c :    mov    $0x0,%eax
 0x0000000100000f41 :    leaveq 
 0x0000000100000f42 :    retq

You see that for a++ and b++ it's an incl mnemonic, so it's the same operation ;)