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Hi, <br>
<br>
Thank you for the directions!<br>
<br>
<div class="moz-cite-prefix">On 9/12/18 6:13 PM, Jason Ekstrand
wrote:<br>
</div>
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<div>Danylo,</div>
<div><br>
</div>
<div>You're free to implement anything not already implemented.
Here are some other (probably simpler) extensions that I think
can be reasonably implemented on Intel HW:</div>
</div>
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<div><br>
</div>
<div> - VK_EXT_conservative_rasterization</div>
<div> - VK_EXT_conditional_render</div>
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Didn't see them, will take closer look later.<br>
<blockquote type="cite"
cite="mid:CAOFGe96Bb2NxnQfP=UN_NfDbLFSH1pmfm2mFz+TrWsJVb7SH=w@mail.gmail.com">
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<div><br>
</div>
<div>As far as VK_KHR_draw_indirect_count go, I haven't
implemented it yet because the "proper" implementation is
actually kind-of painful though not impossible. In general,
there are two ways it can be done:</div>
<div><br>
</div>
<div>## 1. The cheap and easy way</div>
<div><br>
</div>
<div>The spec explicitly allows for the cheap and easy way by
requiring the caller to pass in a maxDrawCount. The idea here
would be to emit maxDrawCount draw calls only have each one of
them predicated on draw_id < draw_count_from_buffer. This
one probably wouldn't take much to wire up but it does mean
doing maxDrawCount 3DPRIMITIVE commands no matter how many of
them are actually needed.</div>
</div>
</blockquote>
I saw such implementation for i965, looked straightforward and I
thought it will easily translate into Vulkan implementation. Didn't
know that it's possible to do it other way on Intel.<br>
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<div><br>
</div>
<div>## 2. The hard but maybe more correct way</div>
<div><br>
</div>
<div>The Intel command streamer does have the ability, if used
carefully, to loop. The difficulty here isn't in looping;
that can be done fairly easily on gen8+ by emitting a
predicated MI_BATCH_BUFFER_START that's predicated off of the
looping condition which jumps to the top of the loop. The
real difficult bit is taking your loop counter and using it to
indirectly access the array of draw information. In order to
do this, you have to have a self-modifying batch buffer. In
short, you would emit MI commands which read the draw
information into registers and also emit MI commands (which
would probably come before the first set) which write the
actual address into the location in the batch where the first
set of MI commands has their address to read from. This would
be a painful to debug mess of GPU hangs but could actually be
kind-of fun to implement.</div>
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</blockquote>
The correct way looks interesting, I'll need some time to understand
details.<br>
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<div><br>
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<div>I hope I haven't scarred you away from working on anv; I
just wanted to make it clear what you're getting yourself
into. Both ways are totally implementable and I think you'd
pretty much have to do the first method on gen7 if we really
care about supporting it there. The second is totally doable,
it'll just involve some headaches when it's broken. If you
want to continue with this project after reading my scarry
e-mail, I recommend starting with method 1 to get your feet
wet and then we can look into method 2 once you have that
working.</div>
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</blockquote>
I'll follow your recommendation and will start from the first
method.<br>
<br>
- Danil<br>
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<div>--Jason<br>
</div>
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<br>
<div class="gmail_quote">
<div dir="ltr">On Wed, Sep 12, 2018 at 6:36 AM Danylo Piliaiev
<<a href="mailto:danylo.piliaiev@gmail.com" target="_blank"
moz-do-not-send="true">danylo.piliaiev@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">Hello
everyone,<br>
<br>
I would like to try to implement one of the Vulkan extensions
- <br>
VK_KHR_draw_indirect_count for anv,<br>
unless someone is already working on it.<br>
<br>
It's a relatively minor extension and I saw that the same
functionality <br>
is already implemented<br>
for ARB_indirect_parameters in i965.<br>
<br>
Also I would appreciate any tips if there are any known
possible tricky <br>
parts.<br>
<br>
- Danil<br>
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</blockquote>
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