"Up variables" is the Lua terminology for "variables in an outer closure". By separating out variables local to the current closure from those in an outer closure, we do get a small speed increase (3-4% on the JSON benchmark), but more importantly we start to move the VM in a direction where we can put variables on the stack.
"Up variables" is the Lua terminology for "variables in an outer closure". By separating out variables local to the current closure from those in an outer closure, we do get a small speed increase (3-4% on the JSON benchmark), but more importantly we start to move the VM in a direction where we can put variables on the stack.