Double question marks ('??') vs if when assigning same var
===

Referring to the following [SE answer](http://stackoverflow.com/a/446839/799379).

When writing

    A = A ?? B;

it is the same as

    if( null != A )
        A = A;
    else
        A = B;

Does that mean that

    if( null == A ) A = B;

would be preferred, performance wise?

Or can I assume that the compiler optimizes the code when the same object is in the `??` notation?
