1328858 - mootools $$("*") spends a lot of time in SetObjectElement

Status: NEW

(Core :: JavaScript Engine: JIT, defect, P3)

Description

[Tom S. (please needinfo tschuster)]

It seems like the biggest perfomance issue now is a missing IC for SetProp/SetElem. Especially it looks like this for me (all total time %):
- SetPropertyIC::update 43%
^ SetObjectElement 37%
^ NativeSetProperty 34%
^ SetNonExistantProperty 22%

So maybe we missing some IC for adding properties?

Comment 1

[Boris Zbarsky [:bzbarsky]]

Bug 1091978 might be relevant?

Comment 2

[Tom S. (please needinfo tschuster)]

The code is adding indexed properties to DOM objects, I don't think we support this an anywhere.

        var d = this.length;
        for (var b = 0, a = arguments.length; b < a; b++) {
            var c = document.id(arguments[b]);
            if (c) {
                this[d++] = c;
            }
        }
        return (this.length = d);

|this| here is HTMLAnchorElement, HTMLElement, HTMLParagraphElement etc.

Comment 3

[Tom S. (please needinfo tschuster)]

|this| is about 20 different HTML* types, so just above our IC limit, but attaching stubs would still hopefully handle 80% of the cases here.

The first reason why we can't attach a stub in this case is the |addProperty| class hook on DOM objects used for preserving wrappers. Ion seems to also guard on the ArrayObject class, which should be unnecessary, because everything can have dense elements. We should look into this after converting SETELEM dense/typed array to CacheIR.