Why is there a performance warning on cast pointer to bool?

Extends.

I thought I was being cool when I did something like:

bool hasParent()
{
  return this->parentNode ;
}

Even with a (bool) cast, the warning still doesn't go away.

Where this->parentNode is NULL when there is no parent node.

But I'm getting:

warning C4800: 'Node *' : forcing value to bool 'true' or 'false' (performance warning)

What's the deal, yo? Why is that a performance warning? I thought it'd be more efficient to not write something like:

bool hasParent()
{
  if( this->parentNode )
    return true ;
  else
    return false ;
}

But the second version generates no warnings and the compiler seems a lot happier. Which is faster though?