[mraleph]

Dart VM is written primarily in C++.

There is bytecode, but the story here is kinda complicated - there are actually 2 different versions: one is called DBC and is used during development of Flutter applications on iOS, there is another called KBC - that one is more like a classical bytecode, it is currently in development.

> And is there a place where more details are available?

You can get some high level information at https://mrale.ph/dartvm

Let me know if you want to know something special.

[markdog12]

> there is another called KBC - that one is more like a classical bytecode, it is currently in development

I haven't heard of this. Why another bytecode version? Increased performance?

[mraleph]

DBC is an interesting beast, the way it was implemented in Dart VM was not like a normal interpreter (e.g. you interpret and then you tier up into JIT which generates native code), but kinda like a pseudoarchitecture. DBC tiers up into... itself. An optimizing JIT in DBC mode would generate optimized DBC bytecodes, not native code. This all kinda makes sense in the environment for which DBC was created - iOS, where you can't JIT. However in environment where you can generate native code this makes no sense - and even prevents you from reaching peak performance.

KBC is an experiment in this space where you have a more classical interpreter which tiers up into native JIT. In KBC mode bytecodes are also given to VM rather than generated internally inside the VM like DBC does.

Theoretically KBC should have better startup latency than just JIT (because you can start executing code immediately, rather than spending time to generate native code) and peak performance that matches JITs - because it tiers up into JIT.

[markdog12]

Interesting, thx. I assume K = Kernel?