[6.0][SwiftSyntax] Enable Package CMO if possible

CMakeLists.txt

@@ -93,13 +93,18 @@ include(CheckSymbolExists)
 include(CMakeDependentOption)
 include(CheckLanguage)
 include(GNUInstallDirs)
-include(SwiftImplicitImport)
+include(SwiftCompilerCapability)
 include(FetchContent)
 
 # Enable Swift for the host compiler build if we have the language. It is
 # optional until we have a bootstrap story.
 check_language(Swift)
 if(CMAKE_Swift_COMPILER)
+  # we are not interested in logging any Swift module used
+  # when configuring the build system -- those are not useful
+  # since they will not contribute to the build of the compiler itself
+  unset(ENV{SWIFT_LOADED_MODULE_TRACE_FILE})
+
   enable_language(Swift)
   set(DEFAULT_SWIFT_MIN_RUNTIME_VERSION "${CMAKE_Swift_COMPILER_VERSION}")
 else()
@@ -845,6 +850,10 @@ if (CMAKE_Swift_COMPILER)
   swift_supports_implicit_module("backtracing"
     SWIFT_SUPPORTS_DISABLE_IMPLICIT_BACKTRACING_MODULE_IMPORT)
   message(STATUS "  Implicit 'backtracing' import: ${SWIFT_SUPPORTS_DISABLE_IMPLICIT_BACKTRACING_MODULE_IMPORT}")
+
+  swift_get_package_cmo_support(
+    Swift_COMPILER_PACKAGE_CMO_SUPPORT)
+  message(STATUS "  Package CMO: ${Swift_COMPILER_PACKAGE_CMO_SUPPORT}")
 else()
   message(STATUS "Swift Compiler (None).")
 endif()

cmake/modules/SwiftCompilerCapability.cmake

@@ -0,0 +1,51 @@
+# Test if the Swift compiler returns success for supplied compiler arguments....
+function(swift_supports_compiler_arguments out_var)
+  file(WRITE "${CMAKE_BINARY_DIR}/tmp/dummy.swift" "")
+  execute_process(
+    COMMAND "${CMAKE_Swift_COMPILER}" -parse ${ARGN} -
+    INPUT_FILE "${CMAKE_BINARY_DIR}/tmp/dummy.swift"
+    OUTPUT_QUIET ERROR_QUIET
+    RESULT_VARIABLE result
+  )
+  if(NOT result)
+    set("${out_var}" "TRUE" PARENT_SCOPE)
+  else()
+    set("${out_var}" "FALSE" PARENT_SCOPE)
+  endif()
+endfunction()
+
+# Test if the Swift compiler supports -disable-implicit-<module>-module-import.
+macro(swift_supports_implicit_module module_name out_var)
+  swift_supports_compiler_arguments(${out_var}
+    -Xfrontend -disable-implicit-${module_name}-module-import
+  )
+endmacro()
+
+# Get "package cross-module-optimization" compiler arguments suitable for the compiler.
+function(swift_get_package_cmo_support out_var)
+  # > 6.0 : Fixed feature.
+  swift_supports_compiler_arguments(result
+    -package-name my-package
+    -Xfrontend -package-cmo
+    -Xfrontend -allow-non-resilient-access
+  )
+  if(result)
+    set(${out_var} IMPLEMENTED PARENT_SCOPE)
+    return()
+  endif()
+
+  # == 6.0 : Experimental.
+  swift_supports_compiler_arguments(result
+    -package-name my-package
+    -Xfrontend -experimental-package-cmo
+    -Xfrontend -experimental-allow-non-resilient-access
+    -Xfrontend -experimental-package-bypass-resilience
+  )
+  if(result)
+    set(${out_var} EXPERIMENTAL PARENT_SCOPE)
+    return()
+  endif()
+
+  # < 6.0 : Not supported.
+  set(${out_var} NO PARENT_SCOPE)
+endfunction()

lib/ASTGen/CMakeLists.txt

@@ -107,6 +107,12 @@ else()
   list(APPEND compile_options "-cxx-interoperability-mode=default")
 endif()
 
+# FXIME: Importing package-cmo enabled '.swiftmodule' causes compiler crash :(
+if(Swift_COMPILER_PACKAGE_CMO_SUPPORT)
+  list(APPEND compile_options
+    "SHELL:-Xfrontend -module-load-mode -Xfrontend prefer-interface")
+endif()
+
 if(SWIFT_BUILD_SWIFT_SYNTAX)
   foreach(target swiftASTGen swiftIDEUtilsBridging)
     target_compile_options(${target} PRIVATE ${compile_options})

lib/Macros/CMakeLists.txt

@@ -37,6 +37,12 @@ function(add_swift_macro_library name)
     return()
   endif()
 
+  # FXIME: Importing package-cmo enabled '.swiftmodule' causes compiler crash :(
+  if(Swift_COMPILER_PACKAGE_CMO_SUPPORT)
+    target_compile_options(${name} PRIVATE
+      "SHELL:-Xfrontend -module-load-mode -Xfrontend prefer-interface")
+  endif()
+
   # Add rpath to 'lib/{platform}'
   file(RELATIVE_PATH relpath_to_lib
     "${SWIFT_HOST_PLUGINS_DEST_DIR}"

stdlib/CMakeLists.txt

@@ -230,7 +230,7 @@ swift_create_stdlib_targets("swift-test-libexec" "" FALSE)
 
 # Check whether the Swift compiler we're using supports
 # -disable-implicit-backtracing-module-import
-include(SwiftImplicitImport)
+include(SwiftCompilerCapability)
 
 swift_supports_implicit_module("backtracing" SWIFT_COMPILER_SUPPORTS_BACKTRACING)
 

tools/swift-plugin-server/CMakeLists.txt

@@ -7,4 +7,10 @@ if (SWIFT_BUILD_SWIFT_SYNTAX)
       SwiftCompilerPluginMessageHandling
       SwiftLibraryPluginProvider
   )
+
+  # FXIME: Importing package-cmo enabled '.swiftmodule' causes compiler crash :(
+  if(Swift_COMPILER_PACKAGE_CMO_SUPPORT)
+    target_compile_options(swift-plugin-server PRIVATE
+      "SHELL:-Xfrontend -module-load-mode -Xfrontend prefer-interface")
+  endif()
 endif()