This hosts the ability to compile and run JavaScript to implement
native functions. This is particularly useful for any native function
that is not a normal function, for example async functions such as
Array.fromAsync, which require yielding.
These functions are not allowed to observe anything from outside their
environment. Any global identifiers will instead be assumed to be a
reference to an abstract operation or a constant. The generator will
inject the appropriate bytecode if the name of the global identifier
matches a known name. Anything else will cause a code generation error.
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
- Create less GC pressure by making each `await` in async function skip
iteration result object allocation.
- Skip uncached `Object::get()` calls to extract `value` and `done` from
the iteration result object.
With this change, following function goes 30% faster on my computer:
```js
(async () => {
const resolved = Promise.resolve();
for (let i = 0; i < 5_000_000; i++) {
await resolved;
}
})();
```
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
