Question

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

In terms of usage of the following, please rate in terms of execution time in C.
In some interviews i was asked which shall i use among these variations and why.

a++
++a
a=a+1
a+=1

Answer 1

Here is what g++ -S produces:

void irrelevant_low_level_worries()
{
    int a = 0;
//  movl    $0, -4(%ebp)

    a++;
//  incl    -4(%ebp)

    ++a;
//  incl    -4(%ebp)

    a = a + 1;
//  incl    -4(%ebp)

    a += 1;
//  incl    -4(%ebp)
}

So even without any optimizer switches, all four statements compile to the exact same machine code.