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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 - Missing transformation rotate(X,Z) == rotate(Y,Z) ---> X == Y"
href="https://bugs.llvm.org/show_bug.cgi?id=51565">51565</a>
</td>
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<th>Summary</th>
<td>Missing transformation rotate(X,Z) == rotate(Y,Z) ---> X == Y
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<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>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>david.bolvansky@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>// Rotate(X,Z) == Rotate(Y,Z) ---> X == Y
// Rotate(X,Z) != Rotate(Y,Z) ---> X != Y
bool test(unsigned long long x, unsigned long long y) {
unsigned long long rx = (x << 32) | (x >> 32);
unsigned long long ry = (y << 32) | (y >> 32);
return rx != ry;
}
Trunk -O2:
test(unsigned long long, unsigned long long): #
@test(unsigned long long, unsigned long long)
rol rdi, 32
rol rsi, 32
cmp rdi, rsi
setne al
ret
<a href="https://godbolt.org/z/Kb6zr8Wa3">https://godbolt.org/z/Kb6zr8Wa3</a>
Alive:
<a href="https://alive2.llvm.org/ce/z/HuEvjC">https://alive2.llvm.org/ce/z/HuEvjC</a></pre>
</div>
</p>
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