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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 - Failure to optimize out check for (x * x) == 0 when (x < -1 || x > 1)"
href="https://bugs.llvm.org/show_bug.cgi?id=45864">45864</a>
</td>
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<tr>
<th>Summary</th>
<td>Failure to optimize out check for (x * x) == 0 when (x < -1 || x > 1)
</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>
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<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<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>gabravier@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>#ifdef __clang__
#define assume __builtin_assume
#else
inline void assume(bool b)
{
if (!b)
__builtin_unreachable();
}
#endif
bool f(int x, bool cond)
{
assume(x > 1 || x < -1);
if (cond)
return (x * x) == 0;
else
return false;
}
This can be optimized to `return false;`. GCC does this transformation, but
Clang does not.</pre>
</div>
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