W3C home > Mailing lists > Public > public-gpu@w3.org > November 2018

Re: Binary vs Text

From: Dzmitry Malyshau <dmalyshau@mozilla.com>
Date: Wed, 7 Nov 2018 12:26:17 -0500
To: public-gpu@w3.org
Message-ID: <3cbaf49b-8a16-8f0b-1a38-78436126104f@mozilla.com>

On 11/7/18 10:29 AM, Filip Pizlo wrote:
> It seems like that’s not what anyone is proposing here. Instead, 
> browsers will have to emit MSL, HLSL, or SPIR-V. That’s regardless of 
> whether the input to the browser is SPIR-V or WHLSL.

I'd like to expand on that (in a similar direction that Florian 
mentioned, but expressed differently). It appears that all modern 
driver-digested shading languages are binary:

   - on Dx12 you compile HLSL -> DXBC/DXIL and that is fed to the driver

   - on Apple you compile MSL -> MTL library, which is what Metal gets 
the function pointers from

   - on Vulkan you provide SPIR-V generated from anything you like

So in the end we'd need a binary format, and it seems to me that going 
from WebSPIR-V  -> DXBC/DXIL/MTL/VkSPIR-V is easier than going from 
WebHLSL. In particular:

   - WebSPIR-V to VkSPIR-V conversion may mostly involve a pass-through 
copying of chunks, with occasional inserting of bounds checks and other 
safe guards. Perhaps, we can define WebSPIR-V in such a way that no work 
is needed at all? This isn't an option with WebHLSL.

   - there is prior art for SPIR-V to anything (SPIRV-Cross) as well as 
incentive to join forces with Khronos VkPortability in writing and 
maintaining one. It doesn't have to be SPIRV-Cross in particular, the 
point is that we'd have the same goals here: we can share the resource 
binding layouts of produced shaders, test suites, ideas, etc.

   - parsing and validating SPIR-V may be easier, since the format is 
very simple (and there isn't any syntactic sugar to care about). Since 
Apple is dedicated to writing WebHLSL converters and validation, I think 
we'll soon have the evidence to see how the code complexity and 
performance fares against one based on WebSPIR-V

   - finally, digesting WebSPIR-V would allow WebHLSL to evolve quicker, 
adopt new programming paradigms, syntax, etc, without waiting for the 
browsers to be updated.

Note: unfortunately, there isn't currently a way to generate MTL library 
without going through MSL. Is this something we can potentially ask 
Apple for in future updates?

Received on Wednesday, 7 November 2018 17:26:41 UTC

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