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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Use ROL to swap scalars"
href="https://bugs.llvm.org/show_bug.cgi?id=44895">44895</a>
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<th>Summary</th>
<td>Use ROL to swap scalars
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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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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<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Backend: X86
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>david.bolvansky@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, spatel+llvm@rotateright.com
</td>
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<p>
<div>
<pre>#include <utility>
void swap (std::pair<int, int> &x)
{
int y[2], t;
__builtin_memcpy (y, &x, sizeof x);
t = y[0]; y[0] = y[1]; y[1] = t;
__builtin_memcpy (&x, y, sizeof x);
}
Clang -Oz/O3:
movl (%rdi), %eax
movl 4(%rdi), %ecx
movl %ecx, (%rdi)
movl %eax, 4(%rdi)
retq
GCC 9.2:
rol QWORD PTR [rdi], 32</pre>
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