I don't know too much about HipHop or PHC, but i do know that it compiles PHP code into more efficient C++ code, I also know, that most likely i do not need it, but, phpfog, a cloud based php app host, offers the option of using either or, so, my questions is, basically the only thing my php code consists of is mysqli prepared statements, there are a couple of other functions, but not much beyond that, but could i even use such a compiler, and would there be any performance increase?
HipHop and PHC are specific to PHP; they do nothing with MySQL stuff. So, no, they won't affect MySQL performance.