[Stdlib][Frontend][CMake] Remove SWIFT_DARWIN_ENABLE_STABLE_ABI_BIT option, make it permanently on.

Author: mikeash

Diff for: CMakeLists.txt

@@ -250,10 +250,6 @@ option(SWIFT_RUNTIME_CRASH_REPORTER_CLIENT
     "Whether to enable CrashReporter integration"
     FALSE)
 
-option(SWIFT_DARWIN_ENABLE_STABLE_ABI_BIT
-    "Enable the Swift stable ABI's class marker bit for new deployment targets"
-    TRUE)
-
 set(SWIFT_DARWIN_XCRUN_TOOLCHAIN "XcodeDefault" CACHE STRING
     "The name of the toolchain to pass to 'xcrun'")
 

Diff for: include/swift/AST/KnownIdentifiers.def

@@ -101,12 +101,7 @@ IDENTIFIER(stringValue)
 IDENTIFIER(super)
 IDENTIFIER(superDecoder)
 IDENTIFIER(superEncoder)
-#if SWIFT_DARWIN_ENABLE_STABLE_ABI_BIT
 IDENTIFIER_WITH_NAME(SwiftObject, "_TtCs12_SwiftObject")
-#else
-// Pre-stable ABI uses un-mangled name for SwiftObject.
-IDENTIFIER(SwiftObject)
-#endif
 IDENTIFIER(to)
 IDENTIFIER(toRaw)
 IDENTIFIER(Type)

Diff for: include/swift/Basic/LangOptions.h

@@ -137,8 +137,10 @@ namespace swift {
     bool EnableObjCInterop = true;
 
     /// On Darwin platforms, use the pre-stable ABI's mark bit for Swift
-    /// classes instead of the stable ABI's bit.
-    bool UseDarwinPreStableABIBit = !bool(SWIFT_DARWIN_ENABLE_STABLE_ABI_BIT);
+    /// classes instead of the stable ABI's bit. This is needed when
+    /// targeting OSes prior to macOS 10.14.4 and iOS 12.2, where
+    /// libobjc does not support the stable ABI's marker bit.
+    bool UseDarwinPreStableABIBit = false;
 
     /// Enables checking that uses of @objc require importing
     /// the Foundation module.

Diff for: include/swift/Config.h.in

@@ -12,6 +12,4 @@
 
 #cmakedefine HAVE_PROC_PID_RUSAGE 1
 
-#cmakedefine01 SWIFT_DARWIN_ENABLE_STABLE_ABI_BIT
-
 #endif // SWIFT_CONFIG_H

Diff for: include/swift/Runtime/CMakeConfig.h.in

@@ -4,7 +4,6 @@
 #ifndef SWIFT_RUNTIME_CMAKECONFIG_H
 #define SWIFT_RUNTIME_CMAKECONFIG_H
 
-#cmakedefine01 SWIFT_DARWIN_ENABLE_STABLE_ABI_BIT
 #cmakedefine01 SWIFT_BNI_OS_BUILD
 #cmakedefine01 SWIFT_BNI_XCODE_BUILD
 

Diff for: lib/Frontend/CompilerInvocation.cpp

@@ -428,15 +428,11 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
                    Target.isOSDarwin());
   Opts.EnableSILOpaqueValues |= Args.hasArg(OPT_enable_sil_opaque_values);
 
-#if SWIFT_DARWIN_ENABLE_STABLE_ABI_BIT
   Opts.UseDarwinPreStableABIBit =
     (Target.isMacOSX() && Target.isMacOSXVersionLT(10, 14, 4)) ||
     (Target.isiOS() && Target.isOSVersionLT(12, 2)) ||
     (Target.isTvOS() && Target.isOSVersionLT(12, 2)) ||
     (Target.isWatchOS() && Target.isOSVersionLT(5, 2));
-#else
-  Opts.UseDarwinPreStableABIBit = true;
-#endif
 
   Opts.DisableConstraintSolverPerformanceHacks |=
       Args.hasArg(OPT_disable_constraint_solver_performance_hacks);

Diff for: lib/IRGen/GenMeta.cpp

@@ -2411,12 +2411,6 @@ static void emitFieldOffsetGlobals(IRGenModule &IGM,
 static ClassFlags getClassFlags(ClassDecl *classDecl) {
   auto flags = ClassFlags();
 
-#if !SWIFT_DARWIN_ENABLE_STABLE_ABI_BIT
-  // FIXME: Remove this after enabling stable ABI.
-  // This bit is NOT conditioned on UseDarwinPreStableABIBit.
-  flags |= ClassFlags::IsSwiftPreStableABI;
-#endif
-
   // Set a flag if the class uses Swift refcounting.
   auto type = classDecl->getDeclaredType()->getCanonicalType();
   if (type->getReferenceCounting() == ReferenceCounting::Native) {

Diff for: stdlib/public/runtime/SwiftObject.h

@@ -30,13 +30,9 @@
 
 #if SWIFT_OBJC_INTEROP
 
-#if SWIFT_DARWIN_ENABLE_STABLE_ABI_BIT
 // Source code: "SwiftObject"
 // Real class name: mangled "Swift._SwiftObject"
 #define SwiftObject _TtCs12_SwiftObject
-#else
-// Pre-stable ABI uses un-mangled name for SwiftObject
-#endif
 
 #if __has_attribute(objc_root_class)
 __attribute__((__objc_root_class__))

Diff for: test/Interpreter/SDK/Inputs/OldABI/OldABI.mm

@@ -158,8 +158,8 @@ static void initialize(void) {
 
 bool CanTestOldABI() {
   // These tests don't work until the stable ABI is using its designed bit.
-  // This check can be removed after SWIFT_DARWIN_ENABLE_STABLE_ABI_BIT
-  // is set everywhere.
+  // This check can be removed after SWIFT_CLASS_IS_SWIFT_MASK is made
+  // static everywhere.
   Class cls = objc_getClass("_TtCs19__EmptyArrayStorage");
   if (!cls) abort();
   uintptr_t *words = (uintptr_t *)cls;

Diff for: test/stdlib/Inputs/SwiftObjectNSObject/SwiftObjectNSObject.m

@@ -74,12 +74,6 @@ void HackSwiftObject()
 {
     SwiftObjectDemangledName = "Swift._SwiftObject";
     Class cls = objc_getClass(SwiftObjectDemangledName);
-    // FIXME: Remove this fallback after we enable
-    // SWIFT_DARWIN_ENABLE_STABLE_ABI_BIT everywhere.
-    if (!cls) {
-        SwiftObjectDemangledName = "SwiftObject";
-        cls = objc_getClass(SwiftObjectDemangledName);
-    }
 
     class_addMethod(cls, @selector(perform0), (IMP)Perform0, "@@:");
     class_addMethod(cls, @selector(perform1:), (IMP)Perform1, "@@:@");