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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 - Failed to combine popcount(x) + popcount(x >> 32) to popcountl(x)"
href="https://bugs.llvm.org/show_bug.cgi?id=50218">50218</a>
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<th>Summary</th>
<td>Failed to combine popcount(x) + popcount(x >> 32) to popcountl(x)
</td>
</tr>
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<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>
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<th>OS</th>
<td>Linux
</td>
</tr>
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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>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<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>int test(unsigned long x) {
return __builtin_popcount(x) + __builtin_popcount(x >> 32);
}
----------------------------------------
define i32 @src(i64 %0) {
%1:
%2 = trunc i64 %0 to i32
%3 = ctpop i32 %2
%4 = lshr i64 %0, 32
%5 = trunc i64 %4 to i32
%6 = ctpop i32 %5
%7 = add i32 %6, %3
ret i32 %7
}
=>
define i32 @tgt(i64 %0) {
%1:
%2 = ctpop i64 %0
%3 = trunc i64 %2 to i32
ret i32 %3
}
Transformation seems to be correct!
alive: <a href="https://alive2.llvm.org/ce/z/XYSuCb">https://alive2.llvm.org/ce/z/XYSuCb</a>
codegen: <a href="https://godbolt.org/z/josqoYEed">https://godbolt.org/z/josqoYEed</a></pre>
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