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by yellowapple 2646 days ago
"The JVM and CLR seem like they're language platforms first and VMs second"

Ding ding ding ding ding.

There are lots of extant application VMs out there, but effectively all of them were implemented specifically to be able to run a specific language (Java → JVM, C# → CLR, Perl 6 → Parrot/NQP/whatever, Erlang → EVM/BEAM, etc.). Other languages have been implemented on top of those VMs, but they have to adopt the semantics of the actually-targeted language; you'd have a hard time taking a pure C codebase and compiling/running it on the JVM or CLR or BEAM.

WebAssembly is not that much different, technically; its actually-targeted languages are C, C++, and Rust, and you can reasonably think of it as a VM for those languages. However, it seems to be making an effort to not get caught up in the semantics of any specific language, much like how machine code tends to not really care about whether the instructions it's executing were compiled from C or Rust or Java or Ruby or COBOL or Brainfuck.
2 comments
b2gills 2639 days ago
Some points of note:

Parrot was intended as a more universal VM, and was started before the Perl6 design solidified. So in the end it didn't actually fit that well with Perl6.

NQP is a small subset of Perl6 that is used for bootstrapping Perl6, and provides an isolation layer from the vagaries of the various VMs it targets. It used to target Parrot, and now targets MoarVM, the JVM, and JavaScript. (NQP is an acronym for Not Quite Perl6.)

MoarVM (Metamodel On A Runtime) was built specifically for Perl6, but its design is minimal. Most of the Perl6 specific features are built using Perl6 and NQP.

For example, MoarVM only provides only enough of an object/type system to bootstrap the full object system. That is MoarVM gets taught how Perl6 objects work every time it loads the Perl6 runtime.

MoarVM also has a pluggable optimizer where you write the plugins in a higher level language. It could be any language that compiles down to MoarVM bytecode. The Perl6 ones are written in NQP.

I think this dynamism makes MoarVM an interesting target for other languages.

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usrusr 2646 days ago
Makes me wonder: is there any language implemented on the JVM that works around the JVM GC the way asm.js works around the js GC? Would it even be possible, could it be performant?
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