Re: draft execution environment for WebGPU, including WebGPU env spec for SPIR-V from Dan Sinclair on 2018-11-14 (public-gpu@w3.org from November 2018)

From: Dan Sinclair <dsinclair@google.com>
Date: Wed, 14 Nov 2018 14:29:38 -0500
To: mjs@apple.com
Cc: Corentin Wallez <cwallez@google.com>, fpizlo@apple.com, David Neto <dneto@google.com>, public-gpu@w3.org
Message-ID: <CAMYH=OhE=GoQ41ryd8M+3XgxvHFDYwktyRNa-YmnMR9+ixKd7w@mail.gmail.com>

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 19:31:17 UTC