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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Passing small struct by value - suboptimal codegen"
href="https://bugs.llvm.org/show_bug.cgi?id=52269">52269</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Passing small struct by value - suboptimal codegen
</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>
<tr>
<th>OS</th>
<td>Windows NT
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Backend: X86
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>david.bolvansky@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, pengfei.wang@intel.com, spatel+llvm@rotateright.com
</td>
</tr></table>
<p>
<div>
<pre>struct X
{
char mem0[32];
char mem1[32];
};
void bar (struct X);
void
foo1(struct X *x)
{
bar(*x);
}
LLVM -O3 or even -Oz:
foo1: # @foo1
sub rsp, 136
movups xmm0, xmmword ptr [rdi]
movups xmm1, xmmword ptr [rdi + 16]
movups xmm2, xmmword ptr [rdi + 32]
movups xmm3, xmmword ptr [rdi + 48]
movaps xmmword ptr [rsp + 112], xmm3
movaps xmmword ptr [rsp + 96], xmm2
movaps xmmword ptr [rsp + 80], xmm1
movaps xmmword ptr [rsp + 64], xmm0
movaps xmm0, xmmword ptr [rsp + 64]
movaps xmm1, xmmword ptr [rsp + 80]
movaps xmm2, xmmword ptr [rsp + 96]
movaps xmm3, xmmword ptr [rsp + 112]
movups xmmword ptr [rsp + 48], xmm3
movups xmmword ptr [rsp + 32], xmm2
movups xmmword ptr [rsp + 16], xmm1
movups xmmword ptr [rsp], xmm0
call bar
add rsp, 136
ret
GCC:
foo1:
sub rsp, 72
movdqu xmm0, XMMWORD PTR [rdi]
movdqu xmm1, XMMWORD PTR [rdi+16]
movdqu xmm2, XMMWORD PTR [rdi+32]
movdqu xmm3, XMMWORD PTR [rdi+48]
movups XMMWORD PTR [rsp], xmm0
movups XMMWORD PTR [rsp+16], xmm1
movups XMMWORD PTR [rsp+32], xmm2
movups XMMWORD PTR [rsp+48], xmm3
call bar
add rsp, 72
ret</pre>
</div>
</p>
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