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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 - Missed optimization on comparison after knowing __builtin_uadd_overflow didn't overflow"
href="https://bugs.llvm.org/show_bug.cgi?id=45688">45688</a>
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<th>Summary</th>
<td>Missed optimization on comparison after knowing __builtin_uadd_overflow didn't overflow
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
</tr>
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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>
</tr>
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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
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<p>
<div>
<pre>bool f(unsigned a, unsigned b)
{
unsigned result;
bool overflowed = __builtin_uadd_overflow(a, b, &result);
__builtin_assume(!overflowed);
return result >= b;
}
This can be optimized to `return 1;`. This transformation is done by GCC, but
not by LLVM.
Comparison here : <a href="https://godbolt.org/z/i44m2a">https://godbolt.org/z/i44m2a</a></pre>
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