Is there a way to save HHVM bytecode as a file, since HHVM uses JIT bytecode compilation instead of compiling? If not, are there any alternatives for modern PHP versions (5.5,5.6)?
You can generate bytecode, which is saved in internal SQLite database and then switch on Repo.Authoritative mode, under which HHVM will only use bytecode from SQLite db and never touch source .php files. See http://hhvm.com/blog/4061/go-faster