How to speed up Drupal 7 compiling PHP to C++?
Following the chain from a comment on this great Wordpress tutorial on the new HHVM, I was led to Nick Veenhof's blog where he posted very recently about his unsuccessful efforts to get hiphop-php working with Drupal.

For what it's worth, the awesome maintainer of hiphop, Sara Goleman, said in the comments that she was interested in supporting Drupal and was going to try to reproduce the issue.

I'm working at building a vagrant VM to help reproduce the error and get everyone on the same page as easily as possible. The plan is to [use a patch that supposedly worked against Drupal 7.4, and hopefully move forward from that working state :)

https://github.com/patcon/vagrant-hiphop-drupal