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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Support cmpxchg of pointer type"
href="https://llvm.org/bugs/show_bug.cgi?id=26668">26668</a>
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<th>Summary</th>
<td>Support cmpxchg of pointer type
</td>
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<tr>
<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>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>
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<th>Component</th>
<td>Core LLVM classes
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>listmail@philipreames.com
</td>
</tr>
<tr>
<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>Today, we do not allow cmpxchg operations with pointer arguments. We require
the frontend to insert ptrtoint casts and do the cmpxchg in integers. While
correct, this is problematic from a couple of perspectives:
1) It makes the IR harder to analyse (for instance, it breaks capture tracking)
2) It pushes work onto the frontend authors for no real gain
The simplest implementation would be to introduce a lowering rule in
AtomicExpand that converts a cmpxchg of pointer type back to the inttoptr type
version the backends already understand. Over time, we could migrate each
backend to natively selecting the pointer type.</pre>
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