VS: ARM64 as default toolset architecture for ARM64 host

Visual Studio 2022 17 Preview introduced a native ARM64 toolchain.

Help/variable/CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE.rst

@@ -9,4 +9,4 @@ The :ref:`Visual Studio Generators` for VS 2013 and above support using
 either the 32-bit or 64-bit host toolchains by specifying a ``host=x86``
 or ``host=x64`` value in the :variable:`CMAKE_GENERATOR_TOOLSET` option.
 CMake provides the selected toolchain architecture preference in this
-variable (``x86``, ``x64``, or empty).
+variable (``x86``, ``x64``, ``ARM64`` or empty).

Source/cmGlobalVisualStudio12Generator.cxx

@@ -138,7 +138,8 @@ bool cmGlobalVisualStudio12Generator::MatchesGeneratorName(
 bool cmGlobalVisualStudio12Generator::ProcessGeneratorToolsetField(
   std::string const& key, std::string const& value)
 {
-  if (key == "host" && (value == "x64" || value == "x86")) {
+  if (key == "host" &&
+      (value == "x64" || value == "x86" || value == "ARM64")) {
     this->GeneratorToolsetHostArchitecture = value;
     return true;
   }

Source/cmGlobalVisualStudioVersionedGenerator.cxx

@@ -27,16 +27,17 @@
 
 #if defined(_M_ARM64)
 #  define HOST_PLATFORM_NAME "ARM64"
-#  define HOST_TOOLS_ARCH ""
+#  define HOST_TOOLS_ARCH(v)                                                  \
+    (v >= cmGlobalVisualStudioGenerator::VSVersion::VS17) ? "ARM64" : ""
 #elif defined(_M_ARM)
 #  define HOST_PLATFORM_NAME "ARM"
-#  define HOST_TOOLS_ARCH ""
+#  define HOST_TOOLS_ARCH(v) ""
 #elif defined(_M_IA64)
 #  define HOST_PLATFORM_NAME "Itanium"
-#  define HOST_TOOLS_ARCH ""
+#  define HOST_TOOLS_ARCH(v) ""
 #elif defined(_WIN64)
 #  define HOST_PLATFORM_NAME "x64"
-#  define HOST_TOOLS_ARCH "x64"
+#  define HOST_TOOLS_ARCH(v) "x64"
 #else
 static bool VSIsWow64()
 {
@@ -58,10 +59,12 @@ static std::string VSHostPlatformName()
 #endif
 }
 
-static std::string VSHostArchitecture()
+static std::string VSHostArchitecture(
+  cmGlobalVisualStudioGenerator::VSVersion v)
 {
+  static_cast<void>(v);
 #ifdef HOST_TOOLS_ARCH
-  return HOST_TOOLS_ARCH;
+  return HOST_TOOLS_ARCH(v);
 #else
   if (VSIsWow64()) {
     return "x64";
@@ -433,7 +436,8 @@ cmGlobalVisualStudioVersionedGenerator::cmGlobalVisualStudioVersionedGenerator(
   this->DefaultLinkFlagTableName = VSVersionToToolset(this->Version);
   if (this->Version >= cmGlobalVisualStudioGenerator::VSVersion::VS16) {
     this->DefaultPlatformName = VSHostPlatformName();
-    this->DefaultPlatformToolsetHostArchitecture = VSHostArchitecture();
+    this->DefaultPlatformToolsetHostArchitecture =
+      VSHostArchitecture(this->Version);
   }
   if (this->Version >= cmGlobalVisualStudioGenerator::VSVersion::VS17) {
     // FIXME: Search for an existing framework?  Under '%ProgramFiles(x86)%',

Tests/RunCMake/GeneratorToolset/TestToolsetHostArchNone.cmake

@@ -6,8 +6,14 @@ if(CMAKE_GENERATOR MATCHES "Visual Studio 1[67]")
   cmake_host_system_information(RESULT is_64_bit QUERY IS_64BIT)
   if(is_64_bit)
     if("${CMAKE_HOST_SYSTEM_PROCESSOR}" STREQUAL "ARM64")
-      if(NOT "${CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE}" STREQUAL "")
-        message(FATAL_ERROR "CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE is not empty as expected.")
+      if(CMAKE_GENERATOR STREQUAL "Visual Studio 17 2022")
+        if(NOT "${CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE}" STREQUAL "ARM64")
+          message(FATAL_ERROR "CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE is not 'ARM64' as expected.")
+        endif()
+      else()
+        if(NOT "${CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE}" STREQUAL "")
+          message(FATAL_ERROR "CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE is not empty as expected.")
+        endif()
       endif()
     elseif(NOT "${CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE}" STREQUAL "x64")
       message(FATAL_ERROR "CMAKE_VS_PLATFORM_TOOLSET_HOST_ARCHITECTURE is not 'x64' as expected.")