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Comment by an-unknown | Hacker News Reader

> and in fact the VM pretty much has to be written in C

What makes you think that you need C/C++ for this? Compilers were and still are written in many languages, and you can always come up with a compiler written in an "arbitrary" language which outputs e.g. an executable ELF file containing your VM runtime code.

There are a few examples of this in the wild btw, look at e.g. the GraalVM and its SubstrateVM sub-project.

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I'm not familiar with the way GraalVM is implemented but I do know that at some point it has to have access to raw memory and registers in order to do JIT. There's no getting around that (and you can't do that with just java).

A compiler is different from a JIT engine since yeah you can just write whatever binary you want to disk, hell you could write an x86 compiler in javascript. but if you want to emit instructions to memory and send the CPU there to consume them, you need a smidge of native code.

Yes you can, that is what compiler intrisics are for.

https://chrisseaton.com/truffleruby/jokerconf17/

and how, pray tell, are intrinsics implemented?

The JIT compiler reckognizes them and give special meaning, see linked article.

i was being rhetorical, the intrinsics are implemented in native code

From Java code AOT compiled into native code, better learn about compilers instead of being rhetorical.

We're literally saying the same thing. Java compiled into a native code library for each target with intrinsics that give access to things like CPU registers is just another way of implementing intrinsics in native code

And native code is not C or C++? How do you think the very first C compiler were written? Spoiler, it was bootstrapped with assembly which was bootstrapped with machine code.

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