Raise the minimum Visual Studio version to VS2019

As raised here: https://lists.llvm.org/pipermail/llvm-dev/2021-November/153881.html

Now that VS2022 is on general release, LLVM is expected to build on VS2017, VS2019 and VS2022, which is proving hazardous to maintain due to changes in behaviour including preprocessor and constexpr changes. Plus of the few developers that work with VS, many have already moved to VS2019/22.

This patch proposes to raise the minimum supported version to VS2019 (16.x) - I've made the hard limit 16.0 or later, with the soft limit VS2019 16.7 - older versions of VS2019 are "allowed" (at your own risk) via the LLVM_FORCE_USE_OLD_TOOLCHAIN cmake flag.

Differential Revision: https://reviews.llvm.org/D114639

clang/docs/ClangFormatStyleOptions.rst

@@ -162,7 +162,7 @@ the configuration (without a prefix: ``Auto``).
     <https://www.webkit.org/coding/coding-style.html>`_
   * ``Microsoft``
     A style complying with `Microsoft's style guide
-    <https://docs.microsoft.com/en-us/visualstudio/ide/editorconfig-code-style-settings-reference?view=vs-2017>`_
+    <https://docs.microsoft.com/en-us/visualstudio/ide/editorconfig-code-style-settings-reference>`_
   * ``GNU``
     A style complying with the `GNU coding standards
     <https://www.gnu.org/prep/standards/standards.html>`_

clang/docs/UsersManual.rst

@@ -3657,7 +3657,7 @@ When using CMake and the Visual Studio generators, the toolset can be set with t
 
   ::
 
-    cmake -G"Visual Studio 15 2017" -T LLVM ..
+    cmake -G"Visual Studio 16 2019" -T LLVM ..
 
 When using CMake with the Ninja generator, set the ``CMAKE_C_COMPILER`` and
 ``CMAKE_CXX_COMPILER`` variables to clang-cl:

lldb/docs/resources/build.rst

@@ -86,7 +86,7 @@ LLDB must use debug python as well.
 Windows
 *******
 
-* Visual Studio 2017.
+* Visual Studio 2019.
 * The latest Windows SDK.
 * The Active Template Library (ATL).
 * `GnuWin32 <http://gnuwin32.sourceforge.net/>`_ for CoreUtils and Make.
@@ -121,8 +121,8 @@ process. They only need to be performed once.
 
 ::
 
-> regsvr32 "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\DIA SDK\bin\msdia140.dll"
-> regsvr32 "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\DIA SDK\bin\amd64\msdia140.dll"
+> regsvr32 "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\DIA SDK\bin\msdia140.dll"
+> regsvr32 "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\DIA SDK\bin\amd64\msdia140.dll"
 
 Any command prompt from which you build LLDB should have a valid Visual Studio
 environment setup. This means you should open an appropriate `Developer Command
@@ -300,7 +300,7 @@ project in another directory.
 
 ::
 
-  $ cmake -G "Visual Studio 15 2017 Win64" -Thost=x64 <cmake variables> <path to root of llvm source tree>
+  $ cmake -G "Visual Studio 16 2019" -A x64 -T host=x64 <cmake variables> <path to root of llvm source tree>
 
 Then you can open the .sln file in Visual Studio, set lldb as the startup
 project, and use F5 to run it. You need only edit the project settings to set

lldb/docs/resources/test.rst

@@ -599,7 +599,7 @@ A quick guide to getting started with PTVS is as follows:
     #. Right click the Project node in Solution Explorer.
     #. In the General tab, Make sure Python 3.5 Debug is the selected Interpreter.
     #. In Debug/Search Paths, enter the path to your ninja/lib/site-packages directory.
-    #. In Debug/Environment Variables, enter ``VCINSTALLDIR=C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\``.
+    #. In Debug/Environment Variables, enter ``VCINSTALLDIR=C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\``.
     #. If you want to enabled mixed mode debugging, check Enable native code debugging (this slows down debugging, so enable it only on an as-needed basis.)
 #. Set the command line for the test suite to run.
     #. Right click the project in solution explorer and choose the Debug tab.

llvm/cmake/modules/CheckCompilerVersion.cmake

@@ -12,9 +12,10 @@ set(APPLECLANG_MIN 6.0)
 set(APPLECLANG_SOFT_ERROR 6.0)
 
 # https://en.wikipedia.org/wiki/Microsoft_Visual_C#Internal_version_numbering
-# _MSC_VER == 1914 MSVC++ 14.14 (Visual Studio 2017 version 15.4)
-set(MSVC_MIN 19.14)
-set(MSVC_SOFT_ERROR 19.14)
+# _MSC_VER == 1920 MSVC++ 14.20 Visual Studio 2019 Version 16.0
+# _MSC_VER == 1927 MSVC++ 14.27 Visual Studio 2019 Version 16.7
+set(MSVC_MIN 19.20)
+set(MSVC_SOFT_ERROR 19.27)
 
 # Map the above GCC versions to dates: https://gcc.gnu.org/develop.html#timeline
 set(GCC_MIN_DATE 20150422)

llvm/docs/CMake.rst

@@ -469,9 +469,7 @@ enabled sub-projects. Nearly all of these variable names begin with
   creation of certain convenience build system targets, such as the various
   ``install-*`` and ``check-*`` targets, since IDEs don't always deal well with
   a large number of targets. This is usually autodetected, but it can be
-  configured manually to explicitly control the generation of those targets. One
-  scenario where a manual override may be desirable is when using Visual Studio
-  2017's CMake integration, which would not be detected as an IDE otherwise.
+  configured manually to explicitly control the generation of those targets.
 
 **LLVM_ENABLE_LIBCXX**:BOOL
   If the host compiler and linker supports the stdlib flag, -stdlib=libc++ is

llvm/docs/GettingStarted.rst

@@ -238,7 +238,7 @@ popular host toolchains for specific minimum versions in our build systems:
 * Clang 3.5
 * Apple Clang 6.0
 * GCC 5.1
-* Visual Studio 2017
+* Visual Studio 2019
 
 Anything older than these toolchains *may* work, but will require forcing the
 build system with a special option and is not really a supported host platform.
@@ -273,8 +273,8 @@ Getting a Modern Host C++ Toolchain
 This section mostly applies to Linux and older BSDs. On macOS, you should
 have a sufficiently modern Xcode, or you will likely need to upgrade until you
 do. Windows does not have a "system compiler", so you must install either Visual
-Studio 2017 or a recent version of mingw64. FreeBSD 10.0 and newer have a modern
-Clang as the system compiler.
+Studio 2019 (or later), or a recent version of mingw64. FreeBSD 10.0 and newer
+have a modern Clang as the system compiler.
 
 However, some Linux distributions and some other or older BSDs sometimes have
 extremely old versions of GCC. These steps attempt to help you upgrade you

llvm/docs/GettingStartedVS.rst

@@ -36,7 +36,7 @@ and software you will need.
 
 Hardware
 --------
-Any system that can adequately run Visual Studio 2017 is fine. The LLVM
+Any system that can adequately run Visual Studio 2019 is fine. The LLVM
 source tree including the git index consumes approximately 3GB.
 Object files, libraries and executables consume approximately 5GB in
 Release mode and much more in Debug mode. SSD drive and >16GB RAM are
@@ -45,13 +45,14 @@ recommended.
 
 Software
 --------
-You will need `Visual Studio <https://visualstudio.microsoft.com/>`_ 2017 or
-higher, with the latest Update installed. Visual Studio Community Edition
+You will need `Visual Studio <https://visualstudio.microsoft.com/>`_ 2019 or
+later, with the latest Update installed. Visual Studio Community Edition
 suffices.
 
 You will also need the `CMake <http://www.cmake.org/>`_ build system since it
 generates the project files you will use to build with. CMake is bundled with
-Visual Studio 2019 so separate installation is not required.
+Visual Studio 2019 so separate installation is not required. If you do install
+CMake separately, Visual Studio 2022 will require CMake Version 3.21 or later.
 
 If you would like to run the LLVM tests you will need `Python
 <http://www.python.org/>`_. Version 3.6 and newer are known to work. You can

llvm/docs/ReleaseNotes.rst

@@ -65,7 +65,7 @@ Changes to the LLVM IR
 Changes to building LLVM
 ------------------------
 
-* ...
+* Building LLVM with Visual Studio now requires version 2019 or later.
 
 Changes to TableGen
 -------------------

llvm/include/llvm/Support/Compiler.h

@@ -77,12 +77,21 @@
 /// * 1916: VS2017, version 15.9
 /// * 1920: VS2019, version 16.0
 /// * 1921: VS2019, version 16.1
+/// * 1922: VS2019, version 16.2
+/// * 1923: VS2019, version 16.3
+/// * 1924: VS2019, version 16.4
+/// * 1925: VS2019, version 16.5
+/// * 1926: VS2019, version 16.6
+/// * 1927: VS2019, version 16.7
+/// * 1928: VS2019, version 16.8 + 16.9
+/// * 1929: VS2019, version 16.10 + 16.11
+/// * 1930: VS2022, version 17.0
 #ifdef _MSC_VER
 #define LLVM_MSC_PREREQ(version) (_MSC_VER >= (version))
 
-// We require at least MSVC 2017.
-#if !LLVM_MSC_PREREQ(1910)
-#error LLVM requires at least MSVC 2017.
+// We require at least VS 2019.
+#if !LLVM_MSC_PREREQ(1920)
+#error LLVM requires at least VS 2019.
 #endif
 
 #else
@@ -94,12 +103,8 @@
 /// Sadly, this is separate from just rvalue reference support because GCC
 /// and MSVC implemented this later than everything else. This appears to be
 /// corrected in MSVC 2019 but not MSVC 2017.
-#if __has_feature(cxx_rvalue_references) || defined(__GNUC__) ||               \
-    LLVM_MSC_PREREQ(1920)
+/// FIXME: Remove LLVM_HAS_RVALUE_REFERENCE_THIS macro
 #define LLVM_HAS_RVALUE_REFERENCE_THIS 1
-#else
-#define LLVM_HAS_RVALUE_REFERENCE_THIS 0
-#endif
 
 /// Expands to '&' if ref-qualifiers for *this are supported.
 ///