Improve += operator performance

Question

I am writing an application that must be very fast. I use Qt 5.5 with Qt Creator, the 64 bit MSVC2013 compiled version of Qt.

I used very sleepy CS to profile my application, and I saw that the function that took the most exclusive time was an operator+= overload (which is called, as you guess, a lot of times).

Here's the piece of code.

struct Coordinate
{
    float                   x;
    float                   y;

    Coordinate operator+=(const Coordinate &coord)
    {
        this->x += coord.x;
        this->y += coord.y;
        return (*this);
    }
};

I wondered if there were a way to improve performance of a function as simple as this one.

Answer 1

operator+= is not quite defined the way you did. Rather, it should be:

Coordinate& operator+=(const Coordinate &coord);

Note the return value of a reference.

This also has the benefit of not creating another copy.

Answer 2

Check if you are profiling Release configurion and compiler optimizations are enabled. Such calls should be inlined by any decent compiler.