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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - va_arg in ms_abi variadic functions should expect large structs to be passed by reference"
href="https://llvm.org/bugs/show_bug.cgi?id=29143">29143</a>
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<th>Summary</th>
<td>va_arg in ms_abi variadic functions should expect large structs to be passed by reference
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>LLVM Codegen
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>rnk@google.com
</td>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>As we discovered in <a href="http://llvm.org/pr20569">http://llvm.org/pr20569</a>, MSVC passes structs larger than 8
bytes indirectly by reference. We now emit the correct code on Win64, but we
don't do the right thing for functions marked ms_abi because they use
__builtin_va_arg instead of __builtin_ms_va_arg.
We should do something so that ms_abi functions on a sys V system act more like
native win64 functions.</pre>
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