[CMake] Cope with the lack of CMAKE_Swift_COMPILER_TARGET on Windows

Author: DougGregor

CMakeLists.txt

@@ -44,6 +44,17 @@ if (NOT SWIFT_SUPPORTS_DISABLE_IMPLICIT_STRING_PROCESSING_MODULE_IMPORT)
     $<$<COMPILE_LANGUAGE:Swift>:-disable-implicit-string-processing-module-import>)
 endif()
 
+# Determine the module triple.
+# FIXME: This is a hack. It's all a hack.
+if(CMAKE_Swift_COMPILER_TARGET)
+  string(REGEX REPLACE "macosx[0-9]+([.][0-9]+)?" "macos" SWIFT_MODULE_TRIPLE
+    ${CMAKE_Swift_COMPILER_TARGET})
+elseif("${CMAKE_SYSTEM_NAME}" STREQUAL "Windows")
+  set(SWIFT_MODULE_TRIPLE "${CMAKE_SYSTEM_PROCESSOR}-unknown-windows-msvc")
+endif()
+
+message(STATUS "Module triple: ${SWIFT_MODULE_TRIPLE}")
+
 # Force single-threaded-only syntax trees to eliminate the Darwin
 # dependency in the compiler.
 add_compile_definitions(

cmake/modules/AddSwiftHostLibrary.cmake

@@ -16,17 +16,12 @@ function(add_swift_host_library name)
   # Add this to the list of exported targets.
   set_property(GLOBAL APPEND PROPERTY SWIFTSYNTAX_EXPORTS ${name})
 
-  # Determine the module triple based on the target triple.
-  # FIXME: We would prefer to have build-script tell us.
-  string(REGEX REPLACE "macosx[0-9]+([.][0-9]+)?" "macos" module_triple
-    ${CMAKE_Swift_COMPILER_TARGET})
-
   # Determine where Swift modules will be built and installed.
   set(module_dir ${CMAKE_LIBRARY_OUTPUT_DIRECTORY})
   set(module_base "${module_dir}/${name}.swiftmodule")
-  set(module_file "${module_base}/${module_triple}.swiftmodule")
-  set(module_interface_file "${module_base}/${module_triple}.swiftinterface")
-  set(module_sourceinfo_file "${module_base}/${module_triple}.swiftsourceinfo")
+  set(module_file "${module_base}/${SWIFT_MODULE_TRIPLE}.swiftmodule")
+  set(module_interface_file "${module_base}/${SWIFT_MODULE_TRIPLE}.swiftinterface")
+  set(module_sourceinfo_file "${module_base}/${SWIFT_MODULE_TRIPLE}.swiftsourceinfo")
 
   # Add a custom target to create the module directory.
   add_custom_command(