[CMake] Add broader support for cross-compiling the portions of the compiler that are written in Swift to non-Darwin Unix

Add cross-compilation flags for the newly added Swift source in `lib/ASTGen/`,
similar to how `SwiftCompilerSources/` is already cross-compiled for other
platforms. Make sure the Swift source in the compiler builds and links against
`SWIFTLIB_DIR` in this cross-compilation build directory, not the one that comes
with the native host compiler.

This requires changing the dependency chain in `CROSSCOMPILE` mode, as normally
the Swift compiler is built first when building natively for the host, then it's
used to build the stdlib. However, when cross-compiling the toolchain, the stdlib
must be cross-compiled first by the host compiler, then the portions of the
Swift compiler written in Swift must be cross-compiled with that new stdlib. All
these dependency changes simply change that compilation order when cross-compiling,
including removing the dependency that the Swift compiler is built before the
stdlib when cross-compiling the Swift compiler.

All changes in this pull are gated on the `CROSSCOMPILE` mode, so they will
not affect any of the existing CI or build presets.

Author: finagolfin

SwiftCompilerSources/CMakeLists.txt

@@ -148,10 +148,9 @@ function(add_swift_compiler_modules_library name)
       list(APPEND sdk_option "-resource-dir" "${swift_exec_bin_dir}/../bootstrapping0/lib/swift")
     endif()
   elseif(BOOTSTRAPPING_MODE STREQUAL "CROSSCOMPILE")
-    get_filename_component(swift_exec_bin_dir ${ALS_SWIFT_EXEC} DIRECTORY)
     # NOTE: prepending allows SWIFT_COMPILER_SOURCES_SDK_FLAGS to override the
     # resource directory if needed.
-    list(PREPEND sdk_option "-resource-dir" "${swift_exec_bin_dir}/../lib/swift")
+    list(PREPEND sdk_option "-resource-dir" "${SWIFTLIB_DIR}")
   endif()
   get_versioned_target_triple(target ${SWIFT_HOST_VARIANT_SDK}
       ${SWIFT_HOST_VARIANT_ARCH} "${deployment_version}")
@@ -225,6 +224,9 @@ function(add_swift_compiler_modules_library name)
         importedHeaderDependencies
       COMMENT "Building swift module ${module}")
 
+    if(BOOTSTRAPPING_MODE STREQUAL "CROSSCOMPILE")
+      add_dependencies(${dep_target} swift-stdlib-${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}-${SWIFT_HOST_VARIANT_ARCH})
+    endif()
     set("${module}_dep_target" ${dep_target})
     set(all_module_targets ${all_module_targets} ${dep_target})
   endforeach()

cmake/modules/AddPureSwift.cmake

@@ -60,6 +60,16 @@ function(_add_host_swift_compile_options name)
     $<$<COMPILE_LANGUAGE:Swift>:none>)
 
   target_compile_options(${name} PRIVATE $<$<COMPILE_LANGUAGE:Swift>:-target;${SWIFT_HOST_TRIPLE}>)
+  if(BOOTSTRAPPING_MODE STREQUAL "CROSSCOMPILE")
+    add_dependencies(${name} swift-stdlib-${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}-${SWIFT_HOST_VARIANT_ARCH})
+    target_compile_options(${name} PRIVATE
+      $<$<COMPILE_LANGUAGE:Swift>:-sdk;${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_ARCH_${SWIFT_HOST_VARIANT_ARCH}_PATH};>
+      $<$<COMPILE_LANGUAGE:Swift>:-resource-dir;${SWIFTLIB_DIR};>)
+    if(SWIFT_HOST_VARIANT_SDK STREQUAL "ANDROID" AND NOT "${SWIFT_ANDROID_NDK_PATH}" STREQUAL "")
+      swift_android_tools_path(${SWIFT_HOST_VARIANT_ARCH} tools_path)
+      target_compile_options(${name} PRIVATE $<$<COMPILE_LANGUAGE:Swift>:-tools-directory;${tools_path};>)
+    endif()
+  endif()
   _add_host_variant_swift_sanitizer_flags(${name})
 
   target_compile_options(${name} PRIVATE

cmake/modules/AddSwift.cmake

@@ -529,15 +529,19 @@ function(_add_swift_runtime_link_flags target relpath_to_lib_dir bootstrapping)
   elseif(SWIFT_HOST_VARIANT_SDK MATCHES "LINUX|ANDROID|OPENBSD|FREEBSD|WINDOWS")
     set(swiftrt "swiftImageRegistrationObject${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_OBJECT_FORMAT}-${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}-${SWIFT_HOST_VARIANT_ARCH}")
     if(ASRLF_BOOTSTRAPPING_MODE MATCHES "HOSTTOOLS|CROSSCOMPILE")
-      # At build time and run time, link against the swift libraries in the
-      # installed host toolchain.
-      if(SWIFT_PATH_TO_SWIFT_SDK)
-        set(swift_dir "${SWIFT_PATH_TO_SWIFT_SDK}/usr")
+      if(ASRLF_BOOTSTRAPPING_MODE STREQUAL "HOSTTOOLS")
+        # At build time and run time, link against the swift libraries in the
+        # installed host toolchain.
+        if(SWIFT_PATH_TO_SWIFT_SDK)
+          set(swift_dir "${SWIFT_PATH_TO_SWIFT_SDK}/usr")
+        else()
+          get_filename_component(swift_bin_dir ${SWIFT_EXEC_FOR_SWIFT_MODULES} DIRECTORY)
+          get_filename_component(swift_dir ${swift_bin_dir} DIRECTORY)
+        endif()
+        set(host_lib_dir "${swift_dir}/lib/swift/${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}")
       else()
-        get_filename_component(swift_bin_dir ${SWIFT_EXEC_FOR_SWIFT_MODULES} DIRECTORY)
-        get_filename_component(swift_dir ${swift_bin_dir} DIRECTORY)
+        set(host_lib_dir "${SWIFTLIB_DIR}/${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}")
       endif()
-      set(host_lib_dir "${swift_dir}/lib/swift/${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}")
       set(host_lib_arch_dir "${host_lib_dir}/${SWIFT_HOST_VARIANT_ARCH}")
 
       set(swiftrt "${host_lib_arch_dir}/swiftrt${CMAKE_C_OUTPUT_EXTENSION}")

lib/SwiftSyntax/CMakeLists.txt

@@ -71,6 +71,10 @@ endif()
 add_dependencies(swift-syntax-lib
   ${SWIFT_SYNTAX_MODULES})
 
+if(BOOTSTRAPPING_MODE STREQUAL "CROSSCOMPILE")
+    add_dependencies(swift-syntax-lib swift-stdlib-${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}-${SWIFT_HOST_VARIANT_ARCH})
+endif()
+
 # Install Swift module interface files.
 foreach(module ${SWIFT_SYNTAX_MODULES})
   set(module_dir "${module}.swiftmodule")

stdlib/cmake/modules/SwiftSource.cmake

@@ -836,8 +836,9 @@ function(_compile_swift_files
   endif()
 
   set(swift_compiler_tool_dep)
-  if(SWIFT_INCLUDE_TOOLS)
-    # Depend on the binary itself, in addition to the symlink.
+  if(SWIFT_INCLUDE_TOOLS AND NOT BOOTSTRAPPING_MODE STREQUAL "CROSSCOMPILE")
+    # Depend on the binary itself, in addition to the symlink, unless
+    # cross-compiling the compiler.
     set(swift_compiler_tool_dep "swift-frontend${target_suffix}")
   endif()
 

tools/SourceKit/cmake/modules/AddSwiftSourceKit.cmake

@@ -106,11 +106,15 @@ function(add_sourcekit_swift_runtime_link_flags target path HAS_SWIFT_MODULES)
   elseif(SWIFT_HOST_VARIANT_SDK MATCHES "LINUX|ANDROID|OPENBSD" AND HAS_SWIFT_MODULES AND ASKD_BOOTSTRAPPING_MODE)
     set(swiftrt "swiftImageRegistrationObject${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_OBJECT_FORMAT}-${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}-${SWIFT_HOST_VARIANT_ARCH}")
     if(ASKD_BOOTSTRAPPING_MODE MATCHES "HOSTTOOLS|CROSSCOMPILE")
-      # At build time and run time, link against the swift libraries in the
-      # installed host toolchain.
-      get_filename_component(swift_bin_dir ${SWIFT_EXEC_FOR_SWIFT_MODULES} DIRECTORY)
-      get_filename_component(swift_dir ${swift_bin_dir} DIRECTORY)
-      set(host_lib_dir "${swift_dir}/lib/swift/${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}")
+      if(ASKD_BOOTSTRAPPING_MODE MATCHES "HOSTTOOLS")
+        # At build time and run time, link against the swift libraries in the
+        # installed host toolchain.
+        get_filename_component(swift_bin_dir ${SWIFT_EXEC_FOR_SWIFT_MODULES} DIRECTORY)
+        get_filename_component(swift_dir ${swift_bin_dir} DIRECTORY)
+        set(host_lib_dir "${swift_dir}/lib/swift/${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}")
+      else()
+        set(host_lib_dir "${SWIFTLIB_DIR}/${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}")
+      endif()
 
       target_link_libraries(${target} PRIVATE ${swiftrt})
       target_link_libraries(${target} PRIVATE "swiftCore")