We will convert masqueradeAsUndefined from a virtual function to a TypeInfo flag. Then we can make operations involving the flag faster.
Created attachment 23640 [details] work in progress Patch seems to work, but is not a speedup.
We can probably turn this into a speedup by using it to allow us to JIT generate eq_null / neq_null. This is implemented in https://bugs.webkit.org/show_bug.cgi?id=20862 using a vptr hack – but broke a test in the webkit tests (never debugged – I'm guessing someone does subclass StringObjectThatMasqueradesAsUndefined, or there is another subclass that implements 'masqueradeAsUndefined()' – in which case the vptr hack won't have been safe).
did a version of this with the JIT logic, see bug 20823 *** This bug has been marked as a duplicate of 20823 ***