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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - MergeFunctions::removeUsers should guard against repeated values"
href="http://llvm.org/bugs/show_bug.cgi?id=19580">19580</a>
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<th>Summary</th>
<td>MergeFunctions::removeUsers should guard against repeated values
</td>
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<th>Product</th>
<td>libraries
</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>Windows NT
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Interprocedural Optimizations
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>ryan@rfk.id.au
</td>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>When using -mergefunc on a large project, I found it would hang forever and
slowly chew up all my RAM (up to several tens of GB of it). The issue appears
to be a reference loop encountered while running the
MergeFunctions::removeUsers method, meaning that its worklist grows without
bound.
I haven't managed to figure out exactly what causes the loop or to produce a
testcase, but adding a simple "previously seen values" check seems to be fix
the issue for me. I'm attaching the patch in case it's useful to others, or if
it's obviously correct even without understanding the cause of the bug.</pre>
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