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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - LLVM trunk generates AVX512BW instructions on KNL architecture"
href="https://bugs.llvm.org/show_bug.cgi?id=36254">36254</a>
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<th>Summary</th>
<td>LLVM trunk generates AVX512BW instructions on KNL architecture
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Backend: X86
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>wenzel.jakob@epfl.ch
</td>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<pre>After upgrading to the latest trunk, I've noticed that LLVM sometimes generates
instructions AVX512BW instructions for the -march=knl target. These naturally
cause the application to fail. See e.g. the following LLDB trace, where a
"kmovd" instruction appears. This instruction should never be emitted, as it is
not part of AVX512F/ER/CD.
Process 161252 launched: '/home/wjakob/mitsuba2/dist/mitsuba2' (x86_64)
Process 161252 stopped
* thread #1, name = 'mitsuba', stop reason = signal SIGILL: illegal instruction
operand
frame #0: 0x0000000041b1a5f6
libmitsuba-core.so`mitsuba::RadicalInverse::eval_scrambled(unsigned long,
enoki::Packet<unsigned long, 16ul, false, (enoki::RoundingMode)4>) const + 182
libmitsuba-core.so`mitsuba::RadicalInverse::eval_scrambled:
-> 0x41b1a5f6 <+182>: kmovd dword ptr [rsp + 0x24], k1
0x41b1a5fd <+189>: vptestmq k1, zmm3, zmm3
0x41b1a603 <+195>: kmovd dword ptr [rsp + 0x20], k1
0x41b1a60a <+202>: vpbroadcastq zmm1, rcx
The application that causes this is unfortunately very large, so I hope that
this trace is helpful enough to look for a potential cause.</pre>
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