<html>
<head>
<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 - Improve codegen for struct init"
href="https://bugs.llvm.org/show_bug.cgi?id=47574">47574</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Improve codegen for struct init
</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: WebAssembly
</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>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>#include <string.h>
#include <stdlib.h>
struct X
{
char mem0[10];
char mem1[10];
};
void bar (struct X);
void
foo1()
{
struct X x = { };
bar (x);
}
void
foo2 ()
{
struct X x;
memset (&x, 0, sizeof x);
bar (x);
}
void
foo3 ()
{
struct X *x = calloc (sizeof (struct X), 1);
bar (*x);
}
Clang -O3:
foo1: # @foo1
sub rsp, 56
xorps xmm0, xmm0
movaps xmmword ptr [rsp + 32], xmm0
mov dword ptr [rsp + 48], 0
mov eax, dword ptr [rsp + 48]
mov dword ptr [rsp + 16], eax
movaps xmm0, xmmword ptr [rsp + 32]
movups xmmword ptr [rsp], xmm0
call bar
add rsp, 56
ret
foo2: # @foo2
sub rsp, 56
xorps xmm0, xmm0
movaps xmmword ptr [rsp + 32], xmm0
mov dword ptr [rsp + 48], 0
mov eax, dword ptr [rsp + 48]
mov dword ptr [rsp + 16], eax
movaps xmm0, xmmword ptr [rsp + 32]
movups xmmword ptr [rsp], xmm0
call bar
add rsp, 56
ret
foo3: # @foo3
sub rsp, 56
mov edi, 20
mov esi, 1
call calloc
mov ecx, dword ptr [rax + 16]
mov dword ptr [rsp + 48], ecx
movups xmm0, xmmword ptr [rax]
movaps xmmword ptr [rsp + 32], xmm0
mov eax, dword ptr [rsp + 48]
mov dword ptr [rsp + 16], eax
movaps xmm0, xmmword ptr [rsp + 32]
movups xmmword ptr [rsp], xmm0
call bar
add rsp, 56
ret
GCC -O3:
foo1:
sub rsp, 72
pxor xmm0, xmm0
mov DWORD PTR [rsp+16], 0
movups XMMWORD PTR [rsp], xmm0
call bar
add rsp, 72
ret
foo2:
sub rsp, 72
pxor xmm0, xmm0
mov DWORD PTR [rsp+48], 0
mov DWORD PTR [rsp+16], 0
movaps XMMWORD PTR [rsp+32], xmm0
movups XMMWORD PTR [rsp], xmm0
call bar
add rsp, 72
ret
foo3:
sub rsp, 8
mov esi, 1
mov edi, 20
call calloc
sub rsp, 32
movdqu xmm0, XMMWORD PTR [rax]
movups XMMWORD PTR [rsp], xmm0
mov eax, DWORD PTR [rax+16]
mov DWORD PTR [rsp+16], eax
call bar
add rsp, 40
ret
<a href="https://godbolt.org/z/WEEdzs">https://godbolt.org/z/WEEdzs</a></pre>
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