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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Ring hang with geometry shaders on SNB"
href="https://bugs.freedesktop.org/show_bug.cgi?id=84104#c3">Comment # 3</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Ring hang with geometry shaders on SNB"
href="https://bugs.freedesktop.org/show_bug.cgi?id=84104">bug 84104</a>
from <span class="vcard"><a class="email" href="mailto:itoral@igalia.com" title="Iago Toral <itoral@igalia.com>"> <span class="fn">Iago Toral</span></a>
</span></b>
<pre>(In reply to <a href="show_bug.cgi?id=84104#c1">comment #1</a>)
<span class="quote">> Our use of "Dual OWord Block" messages appears to be confusing the
> simulator; the second offset is not set to a proper value, so it usually
> ends up being out-of-range and tripping assertions. We may want to use a
> different kind of message.</span >
Right. For the record, the docs say that the hardware checks for out-of-range
writes and does not execute them.
<span class="quote">> But, that doesn't appear to be the real problem. Tentatively, it looks like
> the clipper is hitting an assertion about an unknown primitive topology
> exiting the GS.</span >
mmm... that's interesting.
<span class="quote">> On Gen6, it appears that we have to set the output topology in the GS URB
> Write message header. I am not convinced that we're doing that correctly in
> all cases. I noticed we zero out the input topology field in g0 right away
> - which should be fine, because we have the output topology as
> prog_data->output_topology. We attempt to set that properly, but I'm not
> sure if we set it on every vertex - it looks like we may only set it on the
> first one. Perhaps someone can sanity check this.</span >
Sure, let me have a look and I'll update here.
<span class="quote">> That said, I'm also seeing utterly bizarre values for topology in the
> simulator dump output - in the "primitive-id-restart
> GL_TRIANGLE_STRIP_ADJACENCY" test, it sure looks like we're getting
> 3DPRIM_QUADSTRIP going from the VS->GS, and again going from GS->CL (which
> is unsupported, and will trigger an assert).</span >
>
<span class="quote">> Maybe my analysis is wrong; I can't imagine how that could be.</span ></pre>
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