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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Bad optimization of reverse-initialization of 128-bit vector with 64-bit vectors"
href="https://bugs.llvm.org/show_bug.cgi?id=45748">45748</a>
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<th>Summary</th>
<td>Bad optimization of reverse-initialization of 128-bit vector with 64-bit vectors
</td>
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<th>Product</th>
<td>libraries
</td>
</tr>
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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>Backend: X86
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>gabravier@gmail.com
</td>
</tr>
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<th>CC</th>
<td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, spatel+llvm@rotateright.com
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<p>
<div>
<pre>typedef int32_t v2si __attribute__((vector_size(8)));
typedef int64_t v2di __attribute__((vector_size(16)));
v2di setr_epi64(v2si q0, v2si q1)
{
return v2di{(int64_t)q0, (int64_t)q1};
}
GCC -O3 produces :
setr_epi64(int __vector(2), int __vector(2)):
punpcklqdq xmm0, xmm1
ret
LLVM produces :
setr_epi64(int __vector(2), int __vector(2)): # @setr_epi64(int __vector(2),
int __vector(2))
movq rax, xmm0
movq rcx, xmm1
movq xmm1, rcx
movq xmm0, rax
punpcklqdq xmm0, xmm1 # xmm0 = xmm0[0],xmm1[0]
ret
The code here cannot be further minimized, from what I've been able to see with
my tests.
See also <a href="https://godbolt.org/z/ZC-SWs">https://godbolt.org/z/ZC-SWs</a></pre>
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