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Show HN: Nova JavaScript Engine

(github.com)
268 points aapoalas | 1 comments | 17 Nov 24 23:07 UTC | HN request time: 0.237s | source

We're building a different kind of JavaScript engine, based on data-oriented design and willingness to try something quite out of left field. This is most concretely visible in our major architectural choices:

1. All data allocated on the JavaScript heap is placed into a type-specific vector. Numbers go into the numbers vector, strings into the strings vector, and so on.

2. All heap references are type-discriminated indexes: A heap number is identified by its discriminant value and the index to which it points to in the numbers vector.

3. Objects are also split up into object kind -specific vectors. Ordinary objects go into one vector, Arrays go into another, DataViews into yet another, and so on.

4. Unordinary objects' heap data does not contain ordinary object data but instead they contain an optional index to the ordinary objects vector.

5. Objects are aggressively split into parts to avoid common use-cases having to reading parts that are known to be unused.

If this sounds interesting, I've written a few blog posts on the internals of Nova over in our blog, you can jump into that here: https://trynova.dev/blog/what-is-the-nova-javascript-engine

1. aapoalas ◴[18 Nov 24 10:49 UTC] No.42171298[source]▶
A short comparison to how V8 does these things:

1. All data in V8 is allocated into one of many heap parts: Usually new data goes into a nursery space, and if it does not get GC'd it moves to the old space. Relative position of data isn't really guaranteed at this point.

2. All heap references in V8 are true pointers or, if pointer compression is used, offsets from the heap base.

3. All objects in V8 include all the data needed for them to act as objects, and all of their data is stored in a single allocation (with the exception of properties, with some exceptions). The more specialised an object is, say an ArrayBuffer, Uint8Array, or a DataView, the bigger it has to be as the specialisation requires more data to be stored.