Display current username in conditional function

Hi! I’m fairly new to coding and I’m having trouble combining 2 funtions. Here’s what I’ve got:

<?php
if ( is_user_logged_in() ) {
    echo 'Welcome, registered user!';
} else {
    echo 'Welcome, visitor!';
};
?>

Instead of “registered user, I’d like it to display the current username.

This is what I had:

<?php global $user_identity ;
      get_currentuserinfo();

      echo $user_identity ;
?>

I’ve tried several combinations but I can’t seem to figure it out.