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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 - Failure to optimize __builtin___memcpy_chk optimally"
href="https://bugs.llvm.org/show_bug.cgi?id=46734">46734</a>
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<th>Summary</th>
<td>Failure to optimize __builtin___memcpy_chk optimally
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
</tr>
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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
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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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
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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>void *f(void *d, const void *s, size_t l)
{
return __builtin___memcpy_chk(d, s, l, __builtin_object_size(d, 0));
}
With -O3, GCC outputs this :
f(void*, void const*, unsigned long):
jmp memcpy
LLVM outputs this :
f(void*, void const*, unsigned long):
push rbx
mov rbx, rdi
call memcpy
mov rax, rbx
pop rbx
ret
The same bad code generation can be seen with the same code, but using
`__builtin___memmove_chk` instead of `__builtin___memcpy_chk`.</pre>
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