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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Loop Vectorizer on ARM - why is the relative speedup so much worse?"
href="https://llvm.org/bugs/show_bug.cgi?id=26106">26106</a>
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<th>Summary</th>
<td>Loop Vectorizer on ARM - why is the relative speedup so much worse?
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>3.6
</td>
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<th>Hardware</th>
<td>Other
</td>
</tr>
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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>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Loop Optimizer
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>tulipawn@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=15600" name="attach_15600" title="armv7 LLVM-IR output">attachment 15600</a> <a href="attachment.cgi?id=15600&action=edit" title="armv7 LLVM-IR output">[details]</a></span>
armv7 LLVM-IR output
Hi,
It's my first issue here (I only use llvm via rust) so I might be mistaken in
my understanding but here's the problem. The code snippet from this rust issue:
<a href="https://github.com/rust-lang/rust/issues/30805">https://github.com/rust-lang/rust/issues/30805</a>
is being successfully optimized on x86_64 and posts a 20x speedup using SSE2
whereas on ARM it's a meagre 3x speedup using NEON.
The relative difference seems a little high - is there a problem somewhere on
ARM?
I'm attaching armv7 LLVM-IR in case there is.
Thanks.</pre>
</div>
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