[SwiftCompilerSources][build] Use CMAKE_Swift_COMPILER instead of SWIFT_EXEC_FOR_SWIFT_MODULES

The build process should only use one Swift compiler, and using CMake's built-in `CMAKE_Swift_COMPILER` variable allows using built-in version detection logic (`CMAKE_Swift_COMPILER_VERSION`).

Author: egorzhdan

CMakeLists.txt

@@ -632,12 +632,13 @@ set(SWIFT_RUNTIME_OUTPUT_INTDIR "${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/bin")
 set(SWIFT_LIBRARY_OUTPUT_INTDIR "${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib")
 if("${SWIFT_NATIVE_SWIFT_TOOLS_PATH}" STREQUAL "")
   set(SWIFT_NATIVE_SWIFT_TOOLS_PATH "${SWIFT_RUNTIME_OUTPUT_INTDIR}")
-  set(SWIFT_EXEC_FOR_SWIFT_MODULES "${CMAKE_Swift_COMPILER}")
 elseif(BOOTSTRAPPING_MODE MATCHES "BOOTSTRAPPING.*")
   # If cross-compiling, we don't have to bootstrap. We can just use the previously
   # built native swiftc to build the swift compiler modules.
   message(STATUS "Building swift modules with previously built tools instead of bootstrapping")
-  set(SWIFT_EXEC_FOR_SWIFT_MODULES "${SWIFT_NATIVE_SWIFT_TOOLS_PATH}/swiftc")
+  if(NOT "${SWIFT_NATIVE_SWIFT_TOOLS_PATH}/swiftc" STREQUAL "${CMAKE_Swift_COMPILER}")
+    message(FATAL_ERROR "The Swift compiler (${CMAKE_Swift_COMPILER}) differs from the Swift compiler in SWIFT_NATIVE_SWIFT_TOOLS_PATH (${SWIFT_NATIVE_SWIFT_TOOLS_PATH}/swiftc).")
+  endif()
   if(BOOTSTRAPPING_MODE STREQUAL "BOOTSTRAPPING-WITH-HOSTLIBS")
     set(BOOTSTRAPPING_MODE "CROSSCOMPILE-WITH-HOSTLIBS")
   elseif(BOOTSTRAPPING_MODE STREQUAL "BOOTSTRAPPING")

SwiftCompilerSources/CMakeLists.txt

@@ -200,12 +200,12 @@ else()
 
   if(${BOOTSTRAPPING_MODE} MATCHES "HOSTTOOLS|CROSSCOMPILE")
 
-    if (NOT SWIFT_EXEC_FOR_SWIFT_MODULES)
+    if (NOT CMAKE_Swift_COMPILER)
       message(FATAL_ERROR "Need a swift toolchain building swift compiler sources")
     endif()
 
     add_swift_compiler_modules_library(swiftCompilerModules
-      SWIFT_EXEC "${SWIFT_EXEC_FOR_SWIFT_MODULES}")
+      SWIFT_EXEC "${CMAKE_Swift_COMPILER}")
 
   elseif(${BOOTSTRAPPING_MODE} MATCHES "BOOTSTRAPPING.*")
 

cmake/modules/AddSwift.cmake

@@ -707,7 +707,7 @@ function(add_swift_host_tool executable)
 
       if(BOOTSTRAPPING_MODE STREQUAL "HOSTTOOLS")
         # Add in the toolchain directory so we can grab compatibility libraries
-        get_filename_component(TOOLCHAIN_BIN_DIR ${SWIFT_EXEC_FOR_SWIFT_MODULES} DIRECTORY)
+        get_filename_component(TOOLCHAIN_BIN_DIR ${CMAKE_Swift_COMPILER} DIRECTORY)
         get_filename_component(TOOLCHAIN_LIB_DIR "${TOOLCHAIN_BIN_DIR}/../lib/swift/${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}" ABSOLUTE)
         target_link_directories(${executable} PUBLIC ${TOOLCHAIN_LIB_DIR})
 
@@ -788,7 +788,7 @@ function(add_swift_host_tool executable)
     if(${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_bin_dir ${CMAKE_Swift_COMPILER} 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}")
 

tools/SourceKit/cmake/modules/AddSwiftSourceKit.cmake

@@ -35,7 +35,7 @@ function(add_sourcekitd_swifrt_linking target path HAS_SWIFT_MODULES)
 
       if(BOOTSTRAPPING_MODE STREQUAL "HOSTTOOLS")
         # Add in the toolchain directory so we can grab compatibility libraries
-        get_filename_component(TOOLCHAIN_BIN_DIR ${SWIFT_EXEC_FOR_SWIFT_MODULES} DIRECTORY)
+        get_filename_component(TOOLCHAIN_BIN_DIR ${CMAKE_Swift_COMPILER} DIRECTORY)
         get_filename_component(TOOLCHAIN_LIB_DIR "${TOOLCHAIN_BIN_DIR}/../lib/swift/macosx" ABSOLUTE)
         target_link_directories(${target} PUBLIC ${TOOLCHAIN_LIB_DIR})
 
@@ -113,7 +113,7 @@ function(add_sourcekitd_swifrt_linking target path HAS_SWIFT_MODULES)
     if(${BOOTSTRAPPING_MODE} MATCHES "HOSTTOOLS|CROSSCOMPILE")
       # At build time and 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_bin_dir ${CMAKE_Swift_COMPILER} 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}")