is an iterator allowed to reuse the same "state" object?

Jason Orendorff jason.orendorff at
Fri May 1 18:55:46 UTC 2015

On Wed, Apr 29, 2015 at 5:41 PM, Andreas Rossberg <rossberg at> wrote:
>> I'm inferring your comment about generator optimization hardship has to do
>> with a function that yields -- whose CFG has multiple entry points and whose
>> activation record must live in the heap.
> Yes, the biggest challenge perhaps is not even generator CFGs per se, but
> getting inlining to work with them, which is necessary to take advantage of
> escape analysis.

Since the objects to be eliminated here are not created in the body of
the generator-function, an implementation could create those objects
in an inline-able .next() method, and thus eliminate the object even
if none of the generator code can be inlined. Pseudocode: = function next(arg) {
        var value = INTERNALS.runGenerator(this, arg);
        var done = INTERNALS.generatorIsDone(this);
        return {value, done};

But this too can interfere with other optimizations. Your broader
point about generator optimization certainly stands.


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