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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - please consider using a 128 bit fast build-id"
href="https://bugs.llvm.org/show_bug.cgi?id=44138">44138</a>
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<th>Summary</th>
<td>please consider using a 128 bit fast build-id
</td>
</tr>
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<th>Product</th>
<td>lld
</td>
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<th>Version</th>
<td>unspecified
</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>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>ELF
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>rafael@espindo.la
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, peter.smith@linaro.org
</td>
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<p>
<div>
<pre>lld defaults to a fast build-id hash (which is currently xxhash). That produces
a 64 bit hash.
The other hash options are md5 and sha1, which are probably a bit too slow to
be the default. Linking a release version of scylla with split dwarf I get:
none 2.022252056 seconds
fast 2.061659922 seconds
md5 2.740843349 seconds
sha1 2.318114449 seconds
One issue with fast producing a 64 bit hash is that rpm considers it too small.
I initially reported it as a problem in rpm
(<a href="https://github.com/rpm-software-management/rpm/issues/950">https://github.com/rpm-software-management/rpm/issues/950</a>), but there is an
argument why given the birthday problem and the desire to have a small
probability of a collision on an entire distro 64 bits might not be enough.
I wonder if there is 128 bit hash that would be fast enough to be the default.
Farmhash comes to mind.</pre>
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