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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [ms] wrong calling convention for member functions returning simd types in 64-bit"
href="https://bugs.llvm.org/show_bug.cgi?id=45176">45176</a>
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<th>Summary</th>
<td>[ms] wrong calling convention for member functions returning simd types in 64-bit
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>unspecified
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Windows NT
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
</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>nicolasweber@gmx.de
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>Callee side:
<a href="https://godbolt.org/z/5uyPBD">https://godbolt.org/z/5uyPBD</a>
Looks like rdx contains the address of the return buffer before the call, and
rax contains the address of where the data was written after the call.
Calling side:
<a href="https://godbolt.org/z/_FMkTv">https://godbolt.org/z/_FMkTv</a>
Both f and g tailcall in clang, but only g does in MSVC -- f copies off the
stack first.
(reported here: <a href="https://twitter.com/_xalri/status/1237690440050249733">https://twitter.com/_xalri/status/1237690440050249733</a> ; I
tweaked the flags a bit to pass an msvc --target)
See also
<a href="https://docs.microsoft.com/en-us/cpp/build/x64-calling-convention?view=vs-2019">https://docs.microsoft.com/en-us/cpp/build/x64-calling-convention?view=vs-2019</a>
(ctrl-f __m128)</pre>
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