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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Failure to recognize bswap.i64 pattern"
href="https://bugs.llvm.org/show_bug.cgi?id=45715">45715</a>
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<th>Summary</th>
<td>Failure to recognize bswap.i64 pattern
</td>
</tr>
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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>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>Scalar Optimizations
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>gabravier@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>uint64_t swap64(uint64_t x)
{
return __builtin_bswap32(x >> 32) | ((uint64_t)__builtin_bswap32(x) << 32);
}
This is equivalent to `__builtin_bswap64(x)`. GCC does this transformation, but
only if `__builtin_bswap32` is replaced by a function equivalent to it (i.e.
that is recognized by GCC as equivalent to `__builtin_bswap32`). It would be
nice if LLVM could recognize this as equivalent to `__builtin_bswap64`
Comparison here : <a href="https://godbolt.org/z/gtJQdM">https://godbolt.org/z/gtJQdM</a></pre>
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