Boris Zbarsky wrote:
On 3/28/14 2:15 PM, Gregory Szorc wrote:
I'm concerned about this as well.
Is the concern the spew, or the performance of changing __proto__?
In practice, what gets slow with a changing __proto__ is property
access on the object, because the JS engine throws away type inference
information and marks the object unoptimizable when you change __proto__.
But "slow" here is a relative term. Last I measured, something like a
basic property get in Ion code went from 2-3 instructions to 20-30
instructions when we deoptimize. That's huge on microbenchmarks or
for objects that are being used to store simulation state in physics
simulations or what not, but I doubt the difference matters for your
sqlite connection case. In fact, I doubt the consumers of your API
are even hot enough to get Ion-compiled. And the impact of __proto__
sets is much lower in baseline, and nonexistent in interp, I believe.
What about calls from xpconnect (the original object was a component
exposed as a chrome javascript global property)?
--
Warning: May contain traces of nuts.
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