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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - clang-cl --target=arm64-pc-windows-msvc doesn't support __umulh needed by WinSDK 10.0.20348.0"
href="https://bugs.llvm.org/show_bug.cgi?id=51128">51128</a>
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<th>Summary</th>
<td>clang-cl --target=arm64-pc-windows-msvc doesn't support __umulh needed by WinSDK 10.0.20348.0
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>12.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</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>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>sfinae@hotmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Here's how I reproed this (there may be a simpler way). Install VS 2022 17.0
Preview 2. After choosing the "Desktop development with C++" workload,
customize it:
* Select the "C++ Clang tools for Windows" (containing Clang 12)
* Select the "MSVC v142 - VS 2019 C++ ARM64 build tools (Latest)" (slightly
misnamed; this is the VS 2022 compiler)
* Unselect the default WinSDK 10.0.19041.0
* Select the latest "Windows 10 SDK (10.0.20348.0)"
This setup (Clang 12 + latest WinSDK) works for x86, x64, and ARM (32-bit) in
the microsoft/STL test suite; however, we encountered an incompatibility on
ARM64 due to the new WinSDK attempting to use the __umulh intrinsic, which
works for MSVC but not Clang 12. Self-contained test case, starting from a
clean command prompt:
C:\Temp>"C:\Program Files\Microsoft Visual
Studio\2022\Preview\VC\Auxiliary\Build\vcvarsall.bat" x64_arm64
**********************************************************************
** Visual Studio 2022 Developer Command Prompt v17.0.0-pre.2.0
** Copyright (c) 2021 Microsoft Corporation
**********************************************************************
[vcvarsall.bat] Environment initialized for: 'x64_arm64'
C:\Temp>type meow.cpp
#include <Windows.h>
C:\Temp>cl
Microsoft (R) C/C++ Optimizing Compiler Version 19.30.30401 for ARM64
Copyright (C) Microsoft Corporation. All rights reserved.
usage: cl [ option... ] filename... [ /link linkoption... ]
C:\Temp>cl /EHsc /nologo /W4 /c meow.cpp
meow.cpp
C:\Temp>clang-cl --target=arm64-pc-windows-msvc --version
clang version 12.0.0
Target: arm64-pc-windows-msvc
Thread model: posix
InstalledDir: C:\Program Files\Microsoft Visual
Studio\2022\Preview\VC\Tools\Llvm\x64\bin
C:\Temp>clang-cl --target=arm64-pc-windows-msvc /EHsc /nologo /W4 /c meow.cpp
In file included from meow.cpp:1:
In file included from C:\Program Files (x86)\Windows
Kits\10\\include\10.0.20348.0\\um\Windows.h:171:
In file included from C:\Program Files (x86)\Windows
Kits\10\\include\10.0.20348.0\\shared\windef.h:24:
In file included from C:\Program Files (x86)\Windows
Kits\10\\include\10.0.20348.0\\shared\minwindef.h:182:
C:\Program Files (x86)\Windows
Kits\10\\include\10.0.20348.0\\um\winnt.h(6370,20): error: use of undeclared
identifier
'__umulh'
*HighProduct = UnsignedMultiplyHigh(Multiplier, Multiplicand);
^
C:\Program Files (x86)\Windows
Kits\10\\include\10.0.20348.0\\um\winnt.h(6236,30): note: expanded from macro
'UnsignedMultiplyHigh'
#define UnsignedMultiplyHigh __umulh
^
1 error generated.</pre>
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