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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - vzeroupper elimination"
href="https://bugs.llvm.org/show_bug.cgi?id=42538">42538</a>
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<th>Summary</th>
<td>vzeroupper elimination
</td>
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<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>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
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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
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<th>Reporter</th>
<td>david.bolvansky@gmail.com
</td>
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<th>CC</th>
<td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, spatel+llvm@rotateright.com
</td>
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<p>
<div>
<pre>#include <immintrin.h>
Since GCC 9+, GCC can eliminate vzeroupper in various cases, e.g.:
long long get_elem2(__m256i v) {
return v[2];
}
Clang -O3 -march=skylake-avx512
get_elem2:
vextracti128 xmm0, ymm0, 1
vmovq rax, xmm0
vzeroupper
ret
GCC -O3 -march=skylake-avx512
get_elem2:
vextracti64x2 xmm0, ymm0, 0x1
vmovq rax, xmm0
ret</pre>
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