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This is exciting.
I think WASM is an example of a thin waist [1] with its garbage collector and N+M rather than N×M. (N languages + M virtual machines + G garbage collectors). That's a mature garbage collector in V8.
I was curious if there was a WASM to JVM and it seems there is one on GitHub, I haven't used it I was just curious because the JVM is a parallel garbage collector.
Now I'm excited for WASM Threads for true parallelism and not just IO parallelism.
1: https://www.oilshell.org/blog/2022/02/diagrams.html
2: https://github.com/cretz/asmble
It may take some time for WasmGC to be usable by .NET. Based on the discussions the first version of WasmGC does not have a good way to handle a few .NET specific scenarios, and said scenarios are "post-post-mvp". [0]
My concern, of course, is that there is not much incentive for those features to be added if .NET is the only platform that needs them... at that point having a form of 'include' (to where a specific GC version can just be cached and loaded by another WASM assembly) would be more useful, despite the pain it would create.
[0] - https://github.com/WebAssembly/gc/issues/77
Interesting article, thanks!
Notes on the issues mentioned there:
* The need for a manual shadow stack: This is fixed in WasmGC (in the same way it works in JS, as the link mentions).
* Lack of try-catch: This is fixed by the Wasm exception handling proposal, which has already shipped in browsers, https://github.com/WebAssembly/exception-handling/blob/main/...
* Null checks: Mostly fixed by WasmGC. The spec defines non-nullable local types, and VMs can use the techniques the article mentions to optimize them using signals (Wizard does, for example).
* Class initialization: This is a difficult problem, as the article says. J2Wasm and Binaryen are working to optimize it through static analysis at the toolchain level. Here is a recent PR I wrote that makes progress there: https://github.com/WebAssembly/binaryen/pull/6061
* The vtable overhead issue the article mentions may be a problem. I'm not aware of good measurements on it, through. There are some ideas on post-MVP solutions for method dispatch that might help, but nothing concrete yet.
* Checks for null and trapping: There has been discussion of variants on the GC instructions that throw instead of trap. Measurements, however, have not shown it to be a big problem atm, so it is low priority.
The author is right that stack walking, signals, and memory control are important areas that could help here.
Overall with WasmGC and exceptions we are in a pretty good place for Java as emitted by J2Wasm today: it is usually faster than J2CL which compiles Java to JavaScript. But there is definitely room for improvement.
Hi,
This is off-topic, but we're always looking for compiler people at PRQL (https://prql-lang.org/) to help us build a query language for the next 50 years.
Come and take a look if that's something that floats your boat: https://github.com/prql/prql
AFAIK GC is irrelevant for "direct DOM access", you would rather want to hop into the following rabbit hole:
- reference types: https://github.com/WebAssembly/reference-types/blob/master/p...
- interface types (inactive): https://github.com/WebAssembly/interface-types/blob/main/pro...
- component model: https://github.com/WebAssembly/component-model
If this looks like a mess, that's because it is. Compared to that, the current solution to go through a Javascript shim doesn't look too bad IMHO.
AFAIK GC is irrelevant for "direct DOM access", you would rather want to hop into the following rabbit hole:
- reference types: https://github.com/WebAssembly/reference-types/blob/master/p...
- interface types (inactive): https://github.com/WebAssembly/interface-types/blob/main/pro...
- component model: https://github.com/WebAssembly/component-model
If this looks like a mess, that's because it is. Compared to that, the current solution to go through a Javascript shim doesn't look too bad IMHO.
AFAIK GC is irrelevant for "direct DOM access", you would rather want to hop into the following rabbit hole:
- reference types: https://github.com/WebAssembly/reference-types/blob/master/p...
- interface types (inactive): https://github.com/WebAssembly/interface-types/blob/main/pro...
- component model: https://github.com/WebAssembly/component-model
If this looks like a mess, that's because it is. Compared to that, the current solution to go through a Javascript shim doesn't look too bad IMHO.
Definitely not "literally impossible", just a great deal of work. https://github.com/SerenityOS/serenity/tree/master/Ladybird
LLVM isn't a virtual machine, but WASM is.
That's obviously a common misconception given the name -- LLVM was meant to be a VM early in its life, but never was, and isn't now. It's clarified in the first sentence of a home page - https://llvm.org/
It's basically a bunch of C++ libraries that implements an IR that changes over time, which help you write compilers.
Curiously, I think a decade or more ago there was a project at Google targeting the same space as WASM which made this mistake. They thought LLVM was a virtual machine! That was PNaCl or something.
I guess it's a little like LuaJIT freezing Lua at Lua 5.1 -- Lua was never a standard, but for the purposes of re-implementation, a specific version of it can be frozen. (But there are obvious problems with that approach, namely that the re-implementers don't know about all the bugs they're also freezing in time.)
---
I have raised some eyebrows at the "compromises" of WASM, but the once thing that you can't doubt is that it is in fact a virtual machine !!!
I watched a talk on the WASM GC, and the creators were up front about the compromises (e.g. you will need runtime casts at first, with the measured overhead being reasonable), which gives me more confidence in it:
https://old.reddit.com/r/ProgrammingLanguages/comments/17crk...
A number of concerns with the viability of the current WASM GC are covered here (Google translation to English):
https://habr-com.translate.goog/ru/articles/757182/?_x_tr_sl...
and the original article:
https://habr.com/ru/articles/757182/
This is from the author of TeaVM, who has 10 years of experience getting Java and JVM code to run efficiently in the browser. https://teavm.org/
TeaVM's existing transpilation of Java to JavaScript performs well (using the browsers JS GC). It will be interesting to see if WASM GC matures to the point where it is even faster.
Interesting article, thanks!
Notes on the issues mentioned there:
* The need for a manual shadow stack: This is fixed in WasmGC (in the same way it works in JS, as the link mentions).
* Lack of try-catch: This is fixed by the Wasm exception handling proposal, which has already shipped in browsers, https://github.com/WebAssembly/exception-handling/blob/main/...
* Null checks: Mostly fixed by WasmGC. The spec defines non-nullable local types, and VMs can use the techniques the article mentions to optimize them using signals (Wizard does, for example).
* Class initialization: This is a difficult problem, as the article says. J2Wasm and Binaryen are working to optimize it through static analysis at the toolchain level. Here is a recent PR I wrote that makes progress there: https://github.com/WebAssembly/binaryen/pull/6061
* The vtable overhead issue the article mentions may be a problem. I'm not aware of good measurements on it, through. There are some ideas on post-MVP solutions for method dispatch that might help, but nothing concrete yet.
* Checks for null and trapping: There has been discussion of variants on the GC instructions that throw instead of trap. Measurements, however, have not shown it to be a big problem atm, so it is low priority.
The author is right that stack walking, signals, and memory control are important areas that could help here.
Overall with WasmGC and exceptions we are in a pretty good place for Java as emitted by J2Wasm today: it is usually faster than J2CL which compiles Java to JavaScript. But there is definitely room for improvement.
Thanks for the mention to Wasmer.
I'll put here a link in case is useful for future readers: https://wasmer.io/