Before this change, PropertyNameIterator (used by for..in) and
`Object::enumerable_own_property_names()` (used by `Object.keys()`,
`Object.values()`, and `Object.entries()`) enumerated an object's own
enumerable properties exactly as the spec prescribes:
- Call `internal_own_property_keys()`, allocating a list of JS::Value
keys.
- For each key, call internal_get_own_property() to obtain a
descriptor and check `[[Enumerable]]`.
While that is required in the general case (e.g. for Proxy objects or
platform/exotic objects that override `[[OwnPropertyKeys]]`), it's
overkill for ordinary JS objects that store their own properties in the
shape table and indexed-properties storage.
This change introduces `for_each_own_property_with_enumerability()`,
which, for objects where
`eligible_for_own_property_enumeration_fast_path()` is `true`, lets us
read the enumerability directly from shape metadata (and from
indexed-properties storage) without a per-property descriptor lookup.
When we cannot avoid `internal_get_own_property()`, we still
benefit by skipping the temporary `Vector<Value>` of keys and avoiding
the unnecessary round-trip between PropertyKey and Value.
We already had IC support in PutById for the following cases:
- Changing an existing own property
- Calling a setter located in the prototype chain
This was enough to speed up code where structurally identical objects
(same shape) are processed in a loop:
```js
const arr = [{ a: 1 }, { a: 2 }, { a: 3 }];
for (let obj of arr) {
obj.a += 1;
}
```
However, creating structurally identical objects in a loop was still
slow:
```js
for (let i = 0; i < 10_000_000; i++) {
const o = {};
o.a = 1;
o.b = 2;
o.c = 3;
}
```
This change addresses that by adding a new IC type that caches both the
source and target shapes, allowing property additions to be fast-pathed
by directly jumping to the shape that already includes the new property.
This reverts commit c14173f651. We
should only annotate the minimum number of symbols that external
consumers actually use, so I am starting from scratch to do that
By doing that we avoid lots of `PropertyKey` -> `Value` -> `PropertyKey`
transforms, which are quite expensive because of underlying
`FlyString` -> `PrimitiveString` -> `FlyString` conversions.
10% improvement on MicroBench/object-keys.js
This is *extremely* common on the web, but barely shows up at all in
JavaScript benchmarks.
A typical example is setting Element.innerHTML on a HTMLDivElement.
HTMLDivElement doesn't have innerHTML, so it has to travel up the
prototype chain until it finds it.
Before this change, we didn't cache this at all, so we had to travel
the prototype chain every time a setter like this was used.
We now use the same mechanism we already had for GetBydId and cache
PutById setter accesses in the prototype chain as well.
1.74x speedup on MicroBench/setter-in-prototype-chain.js
Instead of letting every [[Call]] implementation allocate an
ExecutionContext, we now make that a responsibility of the caller.
The main point of this exercise is to allow the Call instruction
to write function arguments directly into the callee ExecutionContext
instead of copying them later.
This makes function calls significantly faster:
- 10-20% faster on micro-benchmarks (depending on argument count)
- 4% speedup on Kraken
- 2% speedup on Octane
- 5% speedup on JetStream
This allows us to remove the BoundFunction::m_name field, which we
were initializing with a formatted FlyString on every function binding,
despite never using it for anything.
Resulting in a massive rename across almost everywhere! Alongside the
namespace change, we now have the following names:
* JS::NonnullGCPtr -> GC::Ref
* JS::GCPtr -> GC::Ptr
* JS::HeapFunction -> GC::Function
* JS::CellImpl -> GC::Cell
* JS::Handle -> GC::Root
To allow implementing the DOM class hierarchy in JS bindings, this
patch adds an inherits() function that can be used to ask an Object
if it inherits from a specific C++ class (by name).
The necessary overrides are baked into each Object subclass by the
new JS_OBJECT macro, which works similarly to C_OBJECT in LibCore.
Thanks to @Dexesttp for suggesting this approach. :^)
Includes all traps except the following: [[Call]], [[Construct]],
[[OwnPropertyKeys]].
An important implication of this commit is that any call to any virtual
Object method has the potential to throw an exception. These methods
were not checked in this commit -- a future commit will have to protect
these various method calls throughout the codebase.
