<html>
<head>
<base href="https://llvm.org/bugs/" />
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Incompatible with GCC abi on Linux AArch64 for zero-sized array GNU extension"
href="https://llvm.org/bugs/show_bug.cgi?id=26162">26162</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Incompatible with GCC abi on Linux AArch64 for zero-sized array GNU extension
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>3.7
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Frontend
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>yyc1992@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>The following code compiles differently in clang and GCC
```
struct large_ha {
struct {
double a[0];
};
double b;
double c;
double d;
};
struct large_ha bar(struct large_ha v)
{
return v;
}
```
Clang treats this as a homogeneous floating-point aggregate (HFA) and pass it
in the register for both the function argument and return value (in the same
register) and therfore the function body is,
```
bar: // @bar
// BB#0:
ret
```
GCC seems to treat this as non-HFA and therefore uses `sret` for the return
value and pass the argument by reference and the code generated is,
```
bar:
mov x1, x0
mov x0, x8
ldp x2, x3, [x1]
ldr x1, [x1, 16]
stp x2, x3, [x8]
str x1, [x8, 16]
ret
```
Giving the embedded struct a name makes no difference on either of them.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>