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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Vectorization generates unaligned moves for properly aligned data"
href="https://bugs.llvm.org/show_bug.cgi?id=39903">39903</a>
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<th>Summary</th>
<td>Vectorization generates unaligned moves for properly aligned data
</td>
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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
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>LLVM Codegen
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>jamesmatta@gmail.com
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<pre>Created <span class=""><a href="attachment.cgi?id=21198" name="attach_21198" title="Code that shows the problem in compiler explorer.">attachment 21198</a> <a href="attachment.cgi?id=21198&action=edit" title="Code that shows the problem in compiler explorer.">[details]</a></span>
Code that shows the problem in compiler explorer.
A simple FMA loop operating on data that is aligned with `alignas(64)` is
generating `vmovups` instructions when it could, and should, be generating
`vmovaps`.
Since the nehalem architecture the cost of a `vmovups` relative to `vmovaps` is
not as large as it once was, but it is noticeable and if the data is guaranteed
to be aligned, then `vmovaps` should be the instruction used.
<a href="https://www.godbolt.org/z/CCcjYu">https://www.godbolt.org/z/CCcjYu</a></pre>
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