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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Support constexpr with builtins (Enhancement)"
href="http://llvm.org/bugs/show_bug.cgi?id=16953">16953</a>
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<th>Summary</th>
<td>Support constexpr with builtins (Enhancement)
</td>
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<th>Product</th>
<td>clang
</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
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++11
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>npl@chello.at
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<th>CC</th>
<td>dgregor@apple.com, llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>Hi,
I have somme annoying issues with using builtins for generating compile-time
constants. It works beautiful with gcc but clang apparently doesnt have
"constexpr builtins". Most of them should easily be able to work at compile
time, amongst them: __builtin_ffs, __builtin_clz, __builtin_ctz,
__builtin_popcount, __builtin_bswap32, __builtin_bswap64
For testing, compile the following with -std=c++11:
inline constexpr int popCount(const unsigned long uVal)
{
return __builtin_popcountll(uVal);
}
int main()
{
return popCount(45);
]</pre>
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