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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 - Optimization for a * 10 == b * 10"
href="https://bugs.llvm.org/show_bug.cgi?id=47432">47432</a>
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</tr>
<tr>
<th>Summary</th>
<td>Optimization for a * 10 == b * 10
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<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>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<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>bool f(int a, int b)
{
return a * 9 == b * 9;
}
bool g(int a, int b)
{
return a * 10 == b * 10;
}
bool h(int a, int b)
{
return a * 11 == b * 11;
}
Clang:
f(int, int): # @f(int, int)
cmp edi, esi
sete al
ret
g(int, int): # @g(int, int)
xor edi, esi
test edi, 2147483647
sete al
ret
h(int, int): # @h(int, int)
cmp edi, esi
sete al
ret
Why 10 is so special here?
<a href="https://godbolt.org/z/jdPhf5">https://godbolt.org/z/jdPhf5</a></pre>
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