On Jun 16, 2011, at 4:32 PM, Mark S. Miller wrote:
> My "Bonus" remark was *only* about Array length. For a great number of
> non-configurable properties (e.g. global vars in ES5 implementations, not
> created by eval), we JIT authors need a general attribute to consult. We
> aren't hardcoding, as we do for Array length (all the fast VMs optimize
> a.length expressions in the dense array, or any array, case).
>
> Can we gather a list of all magical host properties that WebIDL says are
> currently non-configurable but that proxies can't emulate unless they are
> made configurable?
See the recent public-script-coord threads -- but I'm not sure enumerating
cases will help. We do not want to hardcode a list, even if short. Array
length, we hardcode for competitive reasons; that cost is mostly sunk (and
there's no sunk cost fallacy that I can see, just details about how one
optimizes arrays).
For any more general set of non-configurable properties, we want one bit to
condition judgment about how sealed or frozen the property is. We want this
from JIT code, and also for deciding whether it is safe to share deeply frozen
objects across threads via workers.
/be
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