DBC: Can't we just manually inline 'in' here?
if I am not mistaken x in y essentially just calls IN function from runtime.js In this particular case you should be able just to replace i in array with %HasElement(i, array) and hopefully fast path in the %HasElement would take care of the rest. Ideally Crankshaft should take care of this but well... One can dream :-) Vyacheslav Egorov On Tue, Aug 13, 2013 at 5:47 PM, <mstarzin...@chromium.org> wrote: > > https://codereview.chromium.**org/22545007/diff/20001/src/**array.js<https://codereview.chromium.org/22545007/diff/20001/src/array.js> > File src/array.js (right): > > https://codereview.chromium.**org/22545007/diff/20001/src/** > array.js#newcode1263<https://codereview.chromium.org/22545007/diff/20001/src/array.js#newcode1263> > src/array.js:1263: if (!isProxy && %HasFastPackedElements(array) || i in > array) { > On 2013/08/13 14:10:22, Michael Starzinger wrote: > >> It is _really_ surprising that the runtime call into >> Runtime_HasFastPackedElements is cheaper than the "in" keyword. This >> > suggests > >> that there is a lot of potential in actually improving "in" in >> > general. This > >> needs investigation of the generated code! >> > > Now that I think about it, I don't actually think that this is a valid > optimization either. What happens if the callback actually changes the > array in a way so that it remains in fast-packed mode, but "i" still > runs out of bounds. Imagine the following callback. > > var array = [1,2,3,4,5,6]; > Object.defineProperty(array, '1', { > get: function () { array.length = 3; }, > configurable: true > }); > array.forEach(f); > > > https://codereview.chromium.**org/22545007/<https://codereview.chromium.org/22545007/> > > -- > -- > v8-dev mailing list > v8-dev@googlegroups.com > http://groups.google.com/**group/v8-dev<http://groups.google.com/group/v8-dev> > ---You received this message because you are subscribed to the Google > Groups "v8-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to > v8-dev+unsubscribe@**googlegroups.com<v8-dev%2bunsubscr...@googlegroups.com> > . > For more options, visit > https://groups.google.com/**groups/opt_out<https://groups.google.com/groups/opt_out> > . > -- -- v8-dev mailing list v8-dev@googlegroups.com http://groups.google.com/group/v8-dev --- You received this message because you are subscribed to the Google Groups "v8-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to v8-dev+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
