Rename SWIFT_ENABLE_COMPATIBILITY_OVERRIDES -> SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT and avoid building more back-deployment stdlib parts when not set

stdlib/CMakeLists.txt

@@ -89,8 +89,8 @@ option(SWIFT_ENABLE_MODULE_INTERFACES
        "Generate .swiftinterface files alongside .swiftmodule files"
        "${SWIFT_STDLIB_STABLE_ABI}")
 
-option(SWIFT_ENABLE_COMPATIBILITY_OVERRIDES
-       "Support back-deploying compatibility fixes for newer apps running on older runtimes."
+option(SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT
+       "Support back-deployment of built binaries to older OS versions."
        TRUE)
 
 option(SWIFT_STDLIB_HAS_DLADDR

stdlib/cmake/modules/AddSwiftStdlib.cmake

@@ -310,8 +310,8 @@ function(_add_target_variant_c_compile_flags)
     list(APPEND result "-DSWIFT_LIBRARY_EVOLUTION=0")
   endif()
 
-  if(NOT SWIFT_ENABLE_COMPATIBILITY_OVERRIDES)
-    list(APPEND result "-DSWIFT_RUNTIME_NO_COMPATIBILITY_OVERRIDES")
+  if(SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT)
+    list(APPEND result "-DSWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT")
   endif()
 
   if(SWIFT_ENABLE_REFLECTION)

stdlib/cmake/modules/SwiftSource.cmake

@@ -846,7 +846,7 @@ function(_compile_swift_files
   #
   # See stdlib/CMakeLists.txt and TypeConverter::TypeConverter() in
   # lib/IRGen/GenType.cpp.
-  if(SWIFTFILE_IS_STDLIB_CORE)
+  if(SWIFTFILE_IS_STDLIB_CORE AND SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT)
     set(SWIFTFILE_PLATFORM "${SWIFT_SDK_${SWIFTFILE_SDK}_LIB_SUBDIR}")
     set(copy_legacy_layouts_dep
         "copy-legacy-layouts-${SWIFTFILE_PLATFORM}-${SWIFTFILE_ARCHITECTURE}${target_suffix}")

stdlib/linker-support/magic-symbols-for-install-name.c

@@ -17,7 +17,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if defined(__APPLE__) && defined(__MACH__)
+#if defined(__APPLE__) && defined(__MACH__) && SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT
 
 #include <Availability.h>
 #include <TargetConditionals.h>

stdlib/public/CompatibilityOverride/CompatibilityOverride.cpp

@@ -16,7 +16,7 @@
 
 #include "CompatibilityOverride.h"
 
-#ifndef SWIFT_RUNTIME_NO_COMPATIBILITY_OVERRIDES
+#ifdef SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT
 
 #include "../runtime/ImageInspection.h"
 #include "swift/Runtime/Once.h"
@@ -91,4 +91,4 @@ static OverrideSection *getOverrideSectionPtr() {
   }
 #include COMPATIBILITY_OVERRIDE_INCLUDE_PATH
 
-#endif // #ifndef SWIFT_RUNTIME_NO_COMPATIBILITY_OVERRIDES
+#endif // #ifdef SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT

stdlib/public/CompatibilityOverride/CompatibilityOverride.h

@@ -68,13 +68,13 @@ namespace swift {
                        SWIFT_TARGET_LIBRARY_NAME)
 
 // Compatibility overrides are only supported on Darwin.
-#ifndef SWIFT_RUNTIME_NO_COMPATIBILITY_OVERRIDES
+#ifdef SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT
 #if !(defined(__APPLE__) && defined(__MACH__))
-#define SWIFT_RUNTIME_NO_COMPATIBILITY_OVERRIDES
+#undef SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT
 #endif
 #endif
 
-#ifdef SWIFT_RUNTIME_NO_COMPATIBILITY_OVERRIDES
+#ifndef SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT
 
 // Call directly through to the original implementation when we don't support
 // overrides.
@@ -84,7 +84,7 @@ namespace swift {
     return swift_##name##Impl COMPATIBILITY_PAREN(namedArgs);                  \
   }
 
-#else // #ifdef SWIFT_RUNTIME_NO_COMPATIBILITY_OVERRIDES
+#else // #ifndef SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT
 
 // Override section name computation. `COMPATIBILITY_OVERRIDE_SECTION_NAME` will
 // resolve to string literal containing the appropriate section name for the
@@ -129,7 +129,7 @@ namespace swift {
     return swift_##name##Impl COMPATIBILITY_PAREN(namedArgs);                  \
   }
 
-#endif // #else SWIFT_RUNTIME_NO_COMPATIBILITY_OVERRIDES
+#endif // #else SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT
 
 } /* end namespace swift */
 

stdlib/toolchain/CMakeLists.txt

@@ -50,8 +50,10 @@ set(COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_IOS "7.0")
 set(COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_TVOS "9.0")
 set(COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_WATCHOS "2.0")
 
-add_subdirectory(legacy_layouts)
-add_subdirectory(Compatibility50)
-add_subdirectory(Compatibility51)
-add_subdirectory(CompatibilityDynamicReplacements)
-add_subdirectory(CompatibilityConcurrency)
+if(SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT)
+  add_subdirectory(legacy_layouts)
+  add_subdirectory(Compatibility50)
+  add_subdirectory(Compatibility51)
+  add_subdirectory(CompatibilityDynamicReplacements)
+  add_subdirectory(CompatibilityConcurrency)
+endif()

test/lit.cfg

@@ -958,6 +958,10 @@ if run_vendor == 'apple':
             swift_execution_tests_extra_flags += \
                     ' -Xfrontend -disable-implicit-concurrency-module-import'
 
+        # Freestanding doesn't back deploy.
+        swift_execution_tests_extra_flags += \
+                ' -Xfrontend -disable-autolinking-runtime-compatibility-concurrency'
+
         # To have visible references from symbolic manglings
         swift_execution_tests_extra_flags += \
                 ' -Xfrontend -disable-standard-substitutions-in-reflection-mangling'

unittests/runtime/CMakeLists.txt

@@ -1,5 +1,5 @@
 # We can't currently build the runtime tests under ASAN
-# The problem is that we want to use the just-build compiler (just like the
+# The problem is that we want to use the just\build compiler (just like the
 # runtime) but ASAN will complain if we link against libgtest and LLVMSupport
 # libraries because they were compiled with the host compiler.
 if(("${SWIFT_HOST_VARIANT_SDK}" STREQUAL "${SWIFT_PRIMARY_VARIANT_SDK}") AND
@@ -133,6 +133,11 @@ if(("${SWIFT_HOST_VARIANT_SDK}" STREQUAL "${SWIFT_PRIMARY_VARIANT_SDK}") AND
                                swiftCore_EXPORTS
                                SWIFT_INLINE_NAMESPACE=__runtime)
 
+  if(SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT)
+    target_compile_definitions(SwiftRuntimeTests
+                               PRIVATE SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT)
+  endif()
+
   target_include_directories(SwiftRuntimeTests BEFORE PRIVATE
     ${SWIFT_SOURCE_DIR}/stdlib/include)
 

utils/build-presets.ini

@@ -2521,7 +2521,7 @@ build-swift-static-stdlib=1
 swift-objc-interop=0
 swift-enable-dispatch=0
 swift-implicit-concurrency-import=0
-swift-enable-compatibility-overrides=0
+swift-stdlib-support-back-deployment=0
 swift-enable-reflection=0
 swift-stdlib-stable-abi=0
 swift-stdlib-has-dladdr=0

utils/build-script-impl

@@ -205,7 +205,7 @@ KNOWN_SETTINGS=(
     swift-objc-interop                            ""                "whether to enable interoperability with Objective-C, default is 1 on Darwin platforms, 0 otherwise"
     swift-enable-dispatch                         "1"               "whether to enable use of libdispatch"
     swift-implicit-concurrency-import             "1"               "whether to implicitly import the Swift concurrency module"
-    swift-enable-compatibility-overrides          "1"               "whether to support back-deploying compatibility fixes for newer apps running on older runtimes"
+    swift-stdlib-support-back-deployment          "1"               "whether to support back-deployment of built binaries to older OS versions"
     swift-enable-reflection                       "1"               "whether to support reflection and mirrors"
     swift-stdlib-has-dladdr                       "1"               "whether to build stdlib assuming the runtime environment provides dladdr API"
     swift-stdlib-supports-backtrace-reporting     ""                "whether to build stdlib assuming the runtime environment provides the backtrace(3) API, if not set defaults to true on all platforms except for Cygwin, Haiku and wasm"
@@ -1997,7 +1997,7 @@ for host in "${ALL_HOSTS[@]}"; do
                     -DSWIFT_STDLIB_ASSERTIONS:BOOL=$(true_false "${SWIFT_STDLIB_ENABLE_ASSERTIONS}")
                     -DSWIFT_ENABLE_DISPATCH:BOOL=$(true_false "${SWIFT_ENABLE_DISPATCH}")
                     -DSWIFT_IMPLICIT_CONCURRENCY_IMPORT:BOOL=$(true_false "${SWIFT_IMPLICIT_CONCURRENCY_IMPORT}")
-                    -DSWIFT_ENABLE_COMPATIBILITY_OVERRIDES:BOOL=$(true_false "${SWIFT_ENABLE_COMPATIBILITY_OVERRIDES}")
+                    -DSWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT:BOOL=$(true_false "${SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT}")
                     -DSWIFT_STDLIB_SINGLE_THREADED_RUNTIME:BOOL=$(true_false "${SWIFT_STDLIB_SINGLE_THREADED_RUNTIME}")
                     -DSWIFT_ENABLE_RUNTIME_FUNCTION_COUNTERS:BOOL=$(true_false "${SWIFT_ENABLE_RUNTIME_FUNCTION_COUNTERS}")
                     -DSWIFT_STDLIB_HAS_DLADDR:BOOL=$(true_false "${SWIFT_STDLIB_HAS_DLADDR}")