1344177 - Need a faster DefineElement for ArraySpliceCopy

Status: NEW

(Core :: JavaScript Engine, enhancement, P3)

Description

[Jan de Mooij [:jandem]]

This is the main reason we're slower than Chrome in bug 1342797 (after fixing bug 1344173).

If for some reason we don't inline the DefineDataProperty intrinsic or are unable to optimize array.splice better, we fall back to the extremely slow DefineProperty/DefineElement path.

We should at least add a fast path for arrays.

Comment 1

[Jan de Mooij [:jandem]]

Maybe we should add a separate DefineElement intrinsic. DefineElement would always take 3 arguments (instead of DefineDataProperty's 3 or 4), and we could add a fast path to DefineElement for when we're defining an array element at offset denseInitializedLength. Ion could try to inline both intrinsics so there shouldn't be any difference there.

Till, what do you think?

Comment 2

[Till Schneidereit [:till]]

That sounds very good!

It'd be even better if we could also do something about defineProperty for non-elements, but yes, this would sure be very helpful, including on lots of real-world code. Let me know if I can help somehow.

Comment 3

[Jan de Mooij [:jandem]]

Cool. I have some other performance bugs to fix so I'm not working on this yet, but this is definitely something we should fix.

Comment 4

[Jan de Mooij [:jandem]]

Bug 1344463 will deal with _DefineDataProperty.

We should still make ArraySpliceCopy faster, once the other bugs are fixed this will be the main reason why we're slower than Chrome on bug 1342797.

Comment 5

[Sylvestre Ledru [:Sylvestre]]

Moving to p3 because no activity for at least 1 year(s).
See https://github.com/mozilla/bug-handling/blob/master/policy/triage-bugzilla.md#how-do-you-triage for more information