CMake: Add support for building with clang-cl

qmake had support for building with clang-cl as the win32-clang-msvc mkspec.

Task-number: QTBUG-89642
Task-number: QTBUG-88081
Change-Id: I0709c289f90fedb121620d1e67ef841602219816
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

cmake/QtBuild.cmake

@@ -285,7 +285,9 @@ if(WIN32)
         list(APPEND QT_DEFAULT_PLATFORM_DEFINITIONS WIN64 _WIN64)
     endif()
     if(MSVC)
-        if(CMAKE_SYSTEM_PROCESSOR STREQUAL "arm64")
+        if (CLANG)
+            set(QT_DEFAULT_MKSPEC win32-clang-msvc)
+        elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL "arm64")
             set(QT_DEFAULT_MKSPEC win32-arm64-msvc)
         else()
             set(QT_DEFAULT_MKSPEC win32-msvc)

cmake/QtFlagHandlingHelpers.cmake

@@ -235,7 +235,7 @@ endfunction()
 function(qt_set_msvc_cplusplus_options target visibility)
     # For MSVC we need to explicitly pass -Zc:__cplusplus to get correct __cplusplus.
     # Check qt_config_compile_test for more info.
-    if(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC" AND MSVC_VERSION GREATER_EQUAL 1913)
+    if(MSVC AND MSVC_VERSION GREATER_EQUAL 1913)
         target_compile_options("${target}" ${visibility} "-Zc:__cplusplus" "-permissive-")
     endif()
 endfunction()

src/corelib/CMakeLists.txt

@@ -271,6 +271,26 @@ qt_internal_add_module(Core
     # special case end
 )
 
+if (MSVC AND CLANG)
+    foreach(subarch sse4_1 rdrnd rdseed)
+        if (TEST_subarch_${subarch})
+            qt_internal_add_simd_part(Core SIMD ${subarch}
+                SOURCES
+                    global/qsimd.cpp
+            )
+        endif()
+    endforeach()
+
+    foreach(subarch sse4_1 aesni)
+        if (TEST_subarch_${subarch})
+            qt_internal_add_simd_part(Core SIMD ${subarch}
+                SOURCES
+                    tools/qhash.cpp
+            )
+        endif()
+    endforeach()
+endif()
+
 qt_update_ignore_pch_source(Core kernel/qmetatype.cpp )
 
 # special case begin

src/corelib/global/qt_pch.h

@@ -62,19 +62,24 @@
 # define _POSIX_
 # include <limits.h>
 # undef _POSIX_
-#endif
-#include <qcoreapplication.h>
-#include <qcoreevent.h>
-#include <qiodevice.h>
-#include <qlist.h>
-#include <qvariant.h>  /* All moc genereated code has this include */
-#include <qobject.h>
-#if QT_CONFIG(regularexpression)
-#    include <qregularexpression.h>
-#endif
-#include <qscopedpointer.h>
-#include <qshareddata.h>
-#include <qstring.h>
-#include <qstringlist.h>
-#include <qtimer.h>
+#        if defined(Q_CC_CLANG) && defined(Q_CC_MSVC)
+// See https://bugs.llvm.org/show_bug.cgi?id=41226
+#            include <wchar.h>
+__declspec(selectany) auto *__wmemchr_symbol_loader_value = wmemchr(L"", L'0', 0);
+#        endif
+#    endif
+#    include <qcoreapplication.h>
+#    include <qcoreevent.h>
+#    include <qiodevice.h>
+#    include <qlist.h>
+#    include <qvariant.h> /* All moc genereated code has this include */
+#    include <qobject.h>
+#    if QT_CONFIG(regularexpression)
+#        include <qregularexpression.h>
+#    endif
+#    include <qscopedpointer.h>
+#    include <qshareddata.h>
+#    include <qstring.h>
+#    include <qstringlist.h>
+#    include <qtimer.h>
 #endif

src/gui/CMakeLists.txt

@@ -577,6 +577,15 @@ if(NOT ANDROID)
         )
     endif()
 
+    if (MSVC AND CLANG AND TEST_subarch_sse4_1)
+        qt_internal_add_simd_part(Gui SIMD sse4_1
+            SOURCES
+                painting/qdrawhelper.cpp
+                painting/qdrawhelper_sse2.cpp
+                painting/qdrawhelper_ssse3.cpp
+        )
+    endif()
+
     qt_internal_add_simd_part(Gui SIMD ssse3
         SOURCES
             image/qimage_ssse3.cpp