[Webkit-unassigned] [Bug 166480] WebAssembly: test compile / instantiate in a Worker

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=166480

--- Comment #9 from JF Bastien <jfbastien at apple.com> ---
(In reply to comment #8)
> (In reply to comment #7)
> > (In reply to comment #6)
> > > (In reply to comment #5)
> > > > (In reply to comment #4)
> > > > > (In reply to comment #3)
> > > > > > (In reply to comment #2)
> > > > > > > (In reply to comment #1)
> > > > > > > > (In reply to comment #0)
> > > > > > > > > I've heard from someone trying out WebAssembly that they current use compile
> > > > > > > > > / instantiate in a worker because some implementations aren't asynchronous.
> > > > > > > > > They want to do work on the main thread while compiling, so a Worker makes
> > > > > > > > > sense. They then transfer the Module / Instance back to the main thread.
> > > > > > > > > 
> > > > > > > > > We should have a test that this works well.
> > > > > > > > > 
> > > > > > > > > Related:
> > > > > > > > >  - WebAssembly: Make WebAssembly.compile truly asynchronous
> > > > > > > > > https://bugs.webkit.org/show_bug.cgi?id=166016
> > > > > > > > >  - WebAssembly: Implement the WebAssembly.instantiate API
> > > > > > > > > https://bugs.webkit.org/show_bug.cgi?id=165982
> > > > > > > > 
> > > > > > > > I think this should work as expected regardless of the compile API being
> > > > > > > > asynchronous internally.
> > > > > > > 
> > > > > > > Also, I agree we should have a test for this.
> > > > > > 
> > > > > > Right, I want to make sure postMessage-ing Module / Instance / Memory /
> > > > > > Table all work as expected.
> > > > > 
> > > > > Interesting. Is that the expected behavior? This is unlike anything we do
> > > > > elsewhere. We don't postMessage heap cells since each worker is in a
> > > > > different VM
> > > > 
> > > > I don't know what's expected :-D
> > > 
> > > We won't be able to compile a Module then ship over the module across
> > > workers. We will be able to have workers that have their own
> > > Modules/Instances/etc that can run independently. We need to think about
> > > what happens when we try to ship over an ArrayBuffer for Memory. This should
> > > probably not be allowed since it's backed by Wasm::Memory mmaped memory.
> > 
> > IIUC they serialize WebAssembly.Module, and transfer it from Worker to main
> > thread. Apparently this works in Chrome / FF. Should we file an issue on
> > this in the design repo?
> We should probably support the same serialization. I'm interested to know
> what happens to the underlying Memory/etc in the worker that created them
> after they're transferred. Also, what happens to the underlying memory? Is
> there a spec for this serialization? A better API than using workers would
> be we should just make the asynchronous APIs truly asynchronous. I don't
> think that should be too difficult

I believe that only Module is expected to be postMessage-able correctly, and that the details are tied to IndexDB support:
  https://bugs.webkit.org/show_bug.cgi?id=166481

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