Spec compliance of HHVM?

[olydis]

Maybe I missed some details but running the tests (in tests folder) with fresh HHVM does not yield the expected results in all cases (e.g. errors out on negative shift, different output in several cases). Was the idea to have the spec model HHVM or have HHVM follow the spec? I think for some of the discrepancies I saw, HHVM is actually behaving the same as PHP, so I get it if that is behavior that HHVM users rely on.