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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - poor codegen for unaligned fixed-size memcpy/memmove"
href="http://llvm.org/bugs/show_bug.cgi?id=21541">21541</a>
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<th>Summary</th>
<td>poor codegen for unaligned fixed-size memcpy/memmove
</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>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Backend: X86
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>chisophugis@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>void copy32byte(void *pDst, const void *pSrc) {
__builtin_memmove(pDst, pSrc, 32);
}
clang++ -O3 -march=btver2 -c testcopy.cpp -o test.o
generates:
__Z10copy32bytePvPKv:
0000000000000000 pushq %rbp
0000000000000001 movq %rsp, %rbp
0000000000000004 movq (%rsi), %rax
0000000000000007 movq 0x8(%rsi), %rcx
000000000000000b movq 0x10(%rsi), %rdx
000000000000000f movq 0x18(%rsi), %rsi
0000000000000013 movq %rsi, 0x18(%rdi)
0000000000000017 movq %rdx, 0x10(%rdi)
000000000000001b movq %rcx, 0x8(%rdi)
000000000000001f movq %rax, (%rdi)
0000000000000022 popq %rbp
0000000000000023 retq</pre>
</div>
</p>
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