933277 - Optimize creation of new typed objects, particularly non-scalars

Status: RESOLVED INVALID

(Core :: JavaScript Engine: JIT, defect, P5)

Description

[Niko Matsakis [:nmatsakis]]

We do not currently optimize code like:

    var PointType = new StructType({x: uint8, y: uint8});
    new PointType({x: 22, y: 44})

I plan to optimize this over the course of a couple of bugs. This particular bug is for performing the first step of the optimization, which is to detect constructs like "new TypeObject(expr)" and have IonBuilder produce MIR which perform two distinct steps (allocate, initialize):

       var N = NewTypedObject(TypeObject);
       ConvertAndCopy(N, expr, TypeObject); // self-hosted function found in TypedObject.js

This by itself is only a very slight optimization. It avoids the trip into C++ code and instead allocates the object inline. Implementing this is mildly non-trivial because we must obtain a template object. Since TypeObject is a native this requires modifying the baseline compiler (at least it looks that way now; I may try a different approach).

Comment 1

[Benjamin Bouvier [:bbouvier] (inactive)]

Assuming p5 because this is typed objects. (Niko, still working on this?)

Comment 2

[André Bargull [:anba]]

No longer valid, typed object can't be created from JavaScript code anymore.