Is JavaScript code executed now by CPU instead of Interpreter?

Question

Before the Sparkplug compiler, JS code was first converted into byte code and executed, all done by the Ignition Interpreter. The Sparkplug compiler nowadays will take the byte code generated by Ignition Interpreter and turn it into machine code. Great. What executes code, though?

Does the Ignition Interpreter still execute it or maybe the CPU executes it now (machine code generated by Sparkplug)?

EDIT: There is also another JIT compiler called Maglev. So it adds even more confusion now

The question, "What executes code?", is confusing; what exactly do you mean? Of course in all cases some real CPU is running everything. — Pointy
– Pointy, Commented Dec 26, 2024 at 13:59

jmrk · Accepted Answer · 2024-12-26 13:51:47Z

2

Ignition still executes bytecode as the first execution tier.

Machine code is executed by the CPU directly; that's what the term "machine code" means. V8 currently has three JavaScript compilers that generate machine code, in an increasingly optimized fashion for increasingly hot functions: Sparkplug, Maglev, and Turbofan.

answered Dec 26, 2024 at 13:51

jmrk

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2 Comments

Sebastian Dec 26, 2024 at 13:55

Thank you very much for your answer, to be honest I was waiting for an actual V8 developer to come here, I really appreciate it! So, just to confirm. When the code is "slightly hot" it will be taken by a Sparkplug and turned into machine code. When it's "pretty hot" it will be taken by Maglev. When it's "hell-like hot" it will be taken by Turbofan. Correct?

jmrk Dec 26, 2024 at 14:20

@Sebastian Yes, that's the idea.

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