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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Accumulator operations drop to SIMD8 on GEN7"
href="https://bugs.freedesktop.org/show_bug.cgi?id=86822">86822</a>
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<th>Summary</th>
<td>Accumulator operations drop to SIMD8 on GEN7
</td>
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<th>Product</th>
<td>Mesa
</td>
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<th>Version</th>
<td>git
</td>
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<th>Hardware</th>
<td>Other
</td>
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<th>OS</th>
<td>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
</td>
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<th>Component</th>
<td>Drivers/DRI/i965
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<th>Assignee</th>
<td>idr@freedesktop.org
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<th>Reporter</th>
<td>eero.t.tamminen@intel.com
</td>
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<th>QA Contact</th>
<td>intel-3d-bugs@lists.freedesktop.org
</td>
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<th>CC</th>
<td>petri.latvala@intel.com
</td>
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<th>Blocks</th>
<td>77547
</td>
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<pre>There are few games [1], which give with INTEL_DEBUG=perf following output:
SIMD16 shader unsupported, falling back to SIMD8 at a 10-20% performance cost:
SIMD16 explicit accumulator operands unsupported
This SIMD16 issue is GEN7 HW specific. This could be worked around with
additional instructions, which can be skipped if shader falls back to SIMD8 for
some other reason.
[1] This happens at least with Planetary Annihilation & Bastion. And it
happened also with older Mesa & older version of Crusader Kings II version (not
with latest anymore though).</pre>
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