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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Nier:Automata - "if" in fragment shader incorrectly evaluated, causes artifacts"
href="https://bugs.freedesktop.org/show_bug.cgi?id=103743">103743</a>
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<th>Summary</th>
<td>Nier:Automata - "if" in fragment shader incorrectly evaluated, causes artifacts
</td>
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<th>Product</th>
<td>Mesa
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<th>Version</th>
<td>git
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<th>Hardware</th>
<td>x86-64 (AMD64)
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<th>OS</th>
<td>Linux (All)
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>medium
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<th>Component</th>
<td>Drivers/Gallium/radeonsi
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<th>Assignee</th>
<td>dri-devel@lists.freedesktop.org
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<th>Reporter</th>
<td>philip.rebohle@tu-dortmund.de
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<th>QA Contact</th>
<td>dri-devel@lists.freedesktop.org
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</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=135457" name="attach_135457" title="Fragment shader with workaround">attachment 135457</a> <a href="attachment.cgi?id=135457&action=edit" title="Fragment shader with workaround">[details]</a></span>
Fragment shader with workaround
When compiling Mesa against LLVM >= 5.0, Nier:Automata shows lighting artifacts
that are caused by a misbehaving 'if' in a fragment shader.
Apitrace that shows the issue (2.5G, bz2-compressed):
<a href="https://mega.nz/#!JaBD0IoT!yBekRb7ZmvsSY60mo0E7N6uwaYfp_KfRDlnQWL0-QOo">https://mega.nz/#!JaBD0IoT!yBekRb7ZmvsSY60mo0E7N6uwaYfp_KfRDlnQWL0-QOo</a>
I attached a copy of the fragment shader that causes the problem, but also
includes a workaround. The file name for MESA_SHADER_READ_PATH is
FS_feba74122c9590d1522b92bbec52d662ecd99012.glsl.
The offending code is located at line 135:
R1.x = uintBitsToFloat(floatBitsToUint(R0).y >= 0x4u ? 0xffffffffu : 0u);
if (bool(floatBitsToUint(R1).x))
The artifacts go away when changing the original 'if' condition to the
following:
if (floatBitsToUint(R0).y >= 0x4u)
This happens with both Mesa 17.2 and latest Mesa-git when compiling against
LLVM 5.0 or later. This does *not* happen with LLVM 4.0.1. My GPU is an RX 480.</pre>
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