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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 - Missing trunc(ctpop(zext(x))) -> ctpop(x) fold"
href="https://bugs.llvm.org/show_bug.cgi?id=50141">50141</a>
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<th>Summary</th>
<td>Missing trunc(ctpop(zext(x))) -> ctpop(x) fold
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<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<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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</tr>
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<th>Reporter</th>
<td>llvm-dev@redking.me.uk
</td>
</tr>
<tr>
<th>CC</th>
<td>david.bolvansky@gmail.com, lebedev.ri@gmail.com, llvm-bugs@lists.llvm.org, nikita.ppv@gmail.com, spatel+llvm@rotateright.com
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<div>
<pre><a href="https://simd.godbolt.org/z/EcP4en5KG">https://simd.godbolt.org/z/EcP4en5KG</a>
#include <x86intrin.h>
__v8hu ctpop_int(__v8hu x) {
return (__v8hu) {
(unsigned short)__builtin_popcount( x[0] ),
(unsigned short)__builtin_popcount( x[1] ),
(unsigned short)__builtin_popcount( x[2] ),
(unsigned short)__builtin_popcount( x[3] ),
(unsigned short)__builtin_popcount( x[4] ),
(unsigned short)__builtin_popcount( x[5] ),
(unsigned short)__builtin_popcount( x[6] ),
(unsigned short)__builtin_popcount( x[7] )
};
}
define <8 x i16> @ctpop_int(<8 x i16> %0){
%2 = zext <8 x i16> %0 to <8 x i32>
%3 = call <8 x i32> @llvm.ctpop.v8i32(<8 x i32> %2)
%4 = trunc <8 x i32> %3 to <8 x i16>
ret <8 x i16> %4
}
declare <8 x i32> @llvm.ctpop.v8i32(<8 x i32>)
We should be able to just use a @llvm.ctpop.v8i16 call
Not sure if the trunc is vital, or whether we should also allow the fold:
ctpop(zext(x)) -> zext(ctpop(x))</pre>
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