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Re: draft execution environment for WebGPU, including WebGPU env spec for SPIR-V

From: Filip Pizlo <fpizlo@apple.com>
Date: Wed, 14 Nov 2018 11:36:08 -0800
Cc: mjs@apple.com, Corentin Wallez <cwallez@google.com>, David Neto <dneto@google.com>, public-gpu@w3.org
Message-id: <AB4097A0-CAD9-4A21-9C65-68A58DAF511E@apple.com>
To: Dan Sinclair <dsinclair@google.com>
It’s not great that to figure these things out, one must read multiple specs instead of one. 

-Filip

> On Nov 14, 2018, at 11:29 AM, Dan Sinclair <dsinclair@google.com> wrote:
> 
>> On Wed, Nov 14, 2018 at 1:52 PM Maciej Stachowiak <mjs@apple.com> wrote:
>> Consider OpUndef. The whole purpose of this instruction is to invoke an undefined behavior for the sake of performance (since initializing may  be costly when it’s not necessary). Does any shader program containing OpUndef get rejected? Does it trap and halt? Does it return an arbitrary value that is uninitialized and therefore may lead to reading stale data ? Does it initialize to a specific known value (e.g. zero)?
>> 
> 
> The env spec states:
>    OpUndef is not allowed.
> 
> So, the shader would be rejected as invalid.
>  
> dan
> 

Received on Wednesday, 14 November 2018 19:36:38 UTC

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