Re: The design of WebAssembly

Thanks for these references.  I've read through the Semantics.md and the
Rationale.md and have just started the PLDI paper.

WebAssembly looks well thought-out.  A couple of initial thoughts:
- You're trying to support more capable programs than traditionally run on
GPU.   That's fair given that it's supposed to support "main thread" kinds
of apps.
- The docs talk about how nondeterminism will creep in once threads are
supported.  It's good to acknowledge.  This is a big issue: concurrency is
pervasive in GPU shaders.  :-)
- WebAssembly supports recursion, so it uses a general purpose stack to
support it.  That motivates a lot of the design, and parts of the soundness
proofs.
  Shader languages typically ban recursion, so no general stack is
required. That simplifies a lot.
- WebAssembly supports indirect calls (e.g. function pointers).
  Shader languages I know of ban function pointers.  Again, this simplifies
a lot.
- For safety, WebAssembly segregates various things like local variables,
code, tables, and general purpose memory (memories).   A reference to one
thing can't accidentally alias to a reference to another.   I'll have to
write down the argument for it, but SPIR-V with Logical Addressing is
intended to provide veriy similar separate-by-construction guarantees.


While I'm at it:    *Fil: Please post those URLs to the work you cited.*


Thanks
david


On Thu, Aug 24, 2017 at 12:31 AM JF Bastien <w3c@jfbastien.com> wrote:

> In the call today Ken asked about what other projects had tackled problems
> similar to what WebGPU is trying to do, and asked folks to provide
> references.
>
> Here's a paper a few of us wrote about WebAssembly:
>
> https://github.com/WebAssembly/spec/blob/master/papers/pldi2017.pdf
>
>
> Of course it's not all relevant to WebGPU, but it's a good starting point
> to try to break down how we approached the design space, and what
> considerations were taken. I'm happy to answer any questions this raises.
>
> There's also a non-comprehensive rationale document:
>
> https://github.com/WebAssembly/design/blob/master/Rationale.md
>
> It would be cool if WebGPU did a better job that WebAssembly and kept
> better documentation.
>
> Fil said he'd provide references for other projects too, I'll let him do
> that :)
>