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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Code explosion when LoopVectorize vectorizes a loop with a stride of 8 floats"
href="https://llvm.org/bugs/show_bug.cgi?id=27826">27826</a>
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<th>Summary</th>
<td>Code explosion when LoopVectorize vectorizes a loop with a stride of 8 floats
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Loop Optimizer
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>filcab@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>davide@freebsd.org, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk
</td>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>The following code (compile with -O3 -Wall -std=c++11 -ffast-math -march=btver2
):
typedef float T;
T foo(T *a, T *b, int n) {
if (n % 8 != 0)
__builtin_unreachable();
T s = 0;
for (int i=0; i<n; i+=8) {
s += (a[i]+b[i]);
}
return s;
}
Currently expands to a huge blob of code which shuffles around values like
crazy.</pre>
</div>
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