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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Inefficient routines in altivec.h"
href="https://llvm.org/bugs/show_bug.cgi?id=30753">30753</a>
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<th>Summary</th>
<td>Inefficient routines in altivec.h
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
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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>
</tr>
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<th>Status</th>
<td>NEW
</td>
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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>-New Bugs
</td>
</tr>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>echristo@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Code like:
static __inline__ vector signed char __ATTRS_o_ai
vec_mergel(vector signed char __a, vector signed char __b) {
return vec_perm(__a, __b,
(vector unsigned char)(0x08, 0x18, 0x09, 0x19, 0x0A, 0x1A,
0x0B, 0x1B, 0x0C, 0x1C, 0x0D, 0x1D,
0x0E, 0x1E, 0x0F, 0x1F));
}
which is using vec_perm isn't lowered very efficiently versus being lowered to
vmrglb. We should lower as many permutations to shuffles as possible and see
what we can do in the backend for more efficient code rather than hard coding
them though.</pre>
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