Comment by mbrock
16 days ago
Oh yeah, continuation pointers also have their own array like every other field kind, which should have similar benefits as list traversal but for continuation copying... It's a really interesting design area, I think. Zig makes it easy!
Yeah, I'm quite envious of the MultiArrayList or whatever it was that Zig has: If only Rust had that sort of a type built-in <3
That's how I got interested in this kind of memory layout in the first place. I wanted a nice Lisp for WebAssembly and had recently gotten into Zig. When I started defining the word structure I remembered Andy Kelley's talk about using data-oriented design to make the Zig compiler fast, so I thought I'd try it, and the more I thought about it the more reasonable it seemed.
There are like a dozen object types with different growing multiarrays. Words are 32 bit with 1 for GC state and 27 for index and the rest are the type tag. Ints are 28 bits. Byte arrays have their own heap too, as well as general 32 bit vectors.