Remove the -enable-ossa-modules option.

OSSA modules are enabled by default.
The compiler still accepts this option but it has no effect.

Author: eeckstein

Runtimes/Core/CMakeLists.txt

@@ -194,7 +194,6 @@ add_compile_options(
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -disable-implicit-string-processing-module-import>"
   "$<$<COMPILE_LANGUAGE:Swift>:-no-link-objc-runtime>"
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -enforce-exclusivity=unchecked>"
-  "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -enable-ossa-modules>"
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -empty-abi-descriptor>"
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -target-min-inlining-version -Xfrontend min>"
   "$<$<AND:$<NOT:$<BOOL:${SwiftCore_ENABLE_OBJC_INTEROP}>>,$<COMPILE_LANGUAGE:Swift>>:SHELL:-Xfrontend -disable-objc-interop>"

Runtimes/Overlay/CMakeLists.txt

@@ -71,7 +71,6 @@ add_compile_options(
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -disable-implicit-concurrency-module-import>"
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -disable-implicit-string-processing-module-import>"
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -enforce-exclusivity=unchecked>"
-  "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -enable-ossa-modules>"
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -target-min-inlining-version -Xfrontend min>"
   "$<$<AND:$<BOOL:${${PROJECT_NAME}_ENABLE_LIBRARY_EVOLUTION}>,$<COMPILE_LANGUAGE:Swift>>:-enable-library-evolution>"
   "$<$<AND:$<BOOL:${${PROJECT_NAME}_ENABLE_PRESPECIALIZATION}>,$<COMPILE_LANGUAGE:Swift>>:SHELL:-Xfrontend -prespecialize-generic-metadata>")

Runtimes/Supplemental/Observation/CMakeLists.txt

@@ -81,7 +81,6 @@ add_compile_options(
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-enable-experimental-feature Macros>"
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-enable-experimental-feature ExtensionMacros>"
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -enable-lexical-lifetimes=false>"
-  "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -enable-ossa-modules>"
   "$<$<COMPILE_LANGUAGE:Swift>:-warn-implicit-overrides>"
   "$<$<AND:$<BOOL:${${PROJECT_NAME}_ENABLE_LIBRARY_EVOLUTION}>,$<COMPILE_LANGUAGE:Swift>>:-enable-library-evolution>"
   "$<$<AND:$<BOOL:${${PROJECT_NAME}_ENABLE_PRESPECIALIZATION}>,$<COMPILE_LANGUAGE:Swift>>:SHELL:-Xfrontend -prespecialize-generic-metadata>")

include/swift/AST/SILOptions.h

@@ -45,13 +45,12 @@ enum class CopyPropagationOption : uint8_t {
   // Do not add any copy propagation passes.
   Off = 0,
 
-  // Only add the copy propagation passes requested by other flags, currently
-  // just -enable-ossa-modules.
+  // Only add the copy propagation passes requested by other flags.
   RequestedPassesOnly,
 
   // Run copy propagation during optimized builds only.
   //
-  // If a setting, e.g. -enable-ossa-modules, requests to add copy propagation
+  // If a setting, requests to add copy propagation
   // to the performance pipeline, do so.
   Optimizing,
 
@@ -189,11 +188,6 @@ class SILOptions {
   /// and go from OSSA to non-ownership SIL.
   bool StopOptimizationBeforeLoweringOwnership = false;
 
-  /// Do we always serialize SIL in OSSA form?
-  ///
-  /// If this is disabled we do not serialize in OSSA form when optimizing.
-  bool EnableOSSAModules = true;
-
   /// Allow recompilation of a non-OSSA module to an OSSA module when imported
   /// from another OSSA module.
   bool EnableRecompilationToOSSAModule = false;

include/swift/Frontend/ModuleInterfaceLoader.h

@@ -478,49 +478,27 @@ class ModuleInterfaceLoaderOptions {
   ModuleInterfaceLoaderOptions() = default;
 };
 
-/// Strongly typed enum that represents if we require all SILModules to have
-/// OSSA modules emitted. This is implemented by incorporating this bit into the
-/// module cache hash.
-struct RequireOSSAModules_t {
-  enum ValueTy {
-    No = 0,
-    Yes = 1,
-  };
-
-  ValueTy value;
-
-  RequireOSSAModules_t(const SILOptions &opts)
-      : value(opts.EnableOSSAModules ? RequireOSSAModules_t::Yes
-                                     : RequireOSSAModules_t::No) {}
-
-  operator ValueTy() const { return value; }
-  explicit operator bool() const { return bool(value); }
-};
-
 class ModuleInterfaceCheckerImpl: public ModuleInterfaceChecker {
   friend class ModuleInterfaceLoader;
   ASTContext &Ctx;
   std::string CacheDir;
   std::string PrebuiltCacheDir;
   std::string BackupInterfaceDir;
   ModuleInterfaceLoaderOptions Opts;
-  RequireOSSAModules_t RequiresOSSAModules;
 
 public:
   explicit ModuleInterfaceCheckerImpl(ASTContext &Ctx, StringRef cacheDir,
                                 StringRef prebuiltCacheDir,
                                 StringRef BackupInterfaceDir,
-                                ModuleInterfaceLoaderOptions opts,
-                                RequireOSSAModules_t requiresOSSAModules)
+                                ModuleInterfaceLoaderOptions opts)
       : Ctx(Ctx), CacheDir(cacheDir), PrebuiltCacheDir(prebuiltCacheDir),
         BackupInterfaceDir(BackupInterfaceDir),
-        Opts(opts), RequiresOSSAModules(requiresOSSAModules) {}
+        Opts(opts) {}
   explicit ModuleInterfaceCheckerImpl(ASTContext &Ctx, StringRef cacheDir,
                                 StringRef prebuiltCacheDir,
-                                ModuleInterfaceLoaderOptions opts,
-                                RequireOSSAModules_t requiresOSSAModules):
+                                ModuleInterfaceLoaderOptions opts):
     ModuleInterfaceCheckerImpl(Ctx, cacheDir, prebuiltCacheDir, StringRef(),
-                               opts, requiresOSSAModules) {}
+                               opts) {}
   std::vector<std::string>
   getCompiledModuleCandidatesForInterface(StringRef moduleName,
                                           StringRef interfacePath) override;
@@ -596,7 +574,6 @@ class ModuleInterfaceLoader : public SerializedModuleLoaderBase {
       ArrayRef<std::pair<std::string, std::string>> replayPrefixMap,
       bool SerializeDependencyHashes, bool TrackSystemDependencies,
       ModuleInterfaceLoaderOptions Opts,
-      RequireOSSAModules_t RequireOSSAModules,
       bool silenceInterfaceDiagnostics);
 
   /// Unconditionally build \p InPath (a swiftinterface file) to \p OutPath (as
@@ -666,8 +643,7 @@ struct InterfaceSubContextDelegateImpl : InterfaceSubContextDelegate {
                                      const LangOptions &LangOpts,
                                      const ClangImporterOptions &clangImporterOpts,
                                      const CASOptions &casOpts,
-                                     bool suppressRemarks,
-                                     RequireOSSAModules_t requireOSSAModules);
+                                     bool suppressRemarks);
   bool extractSwiftInterfaceVersionAndArgs(CompilerInvocation &subInvocation,
                                            DiagnosticEngine &subInstanceDiags,
                                            SwiftInterfaceInfo &interfaceInfo,
@@ -684,7 +660,7 @@ struct InterfaceSubContextDelegateImpl : InterfaceSubContextDelegate {
       StringRef backupModuleInterfaceDir,
       ArrayRef<std::pair<std::string, std::string>> replayPrefixMap,
       bool serializeDependencyHashes,
-      bool trackSystemDependencies, RequireOSSAModules_t requireOSSAModules);
+      bool trackSystemDependencies);
 
   template<typename ...ArgTypes>
   static InFlightDiagnostic diagnose(StringRef interfacePath,

include/swift/Option/FrontendOptions.td

@@ -1320,8 +1320,7 @@ def disable_ast_verifier : Flag<["-"], "disable-ast-verifier">,
 
 let Flags = [FrontendOption, NoDriverOption, HelpHidden, ModuleInterfaceOptionIgnorable] in {
   def enable_ossa_modules : Flag<["-"], "enable-ossa-modules">,
-    HelpText<"Always serialize SIL in ossa form. If this flag is not passed in, "
-            "when optimizing ownership will be lowered before serializing SIL">;
+    HelpText<"Obsolete. This option is ignored">;
 }
 
 def enable_recompilation_to_ossa_module : Flag<["-"], "enable-recompilation-to-ossa-module">,

include/swift/Serialization/SerializedModuleLoader.h

@@ -193,7 +193,6 @@ class SerializedModuleLoaderBase : public ModuleLoader {
   static llvm::ErrorOr<std::vector<ScannerImportStatementInfo>>
   getMatchingPackageOnlyImportsOfModule(Twine modulePath,
                                         bool isFramework,
-                                        bool isRequiredOSSAModules,
                                         StringRef SDKName,
                                         const llvm::Triple &target,
                                         StringRef packageName,
@@ -222,8 +221,6 @@ class SerializedModuleLoaderBase : public ModuleLoader {
           std::unique_ptr<llvm::MemoryBuffer> moduleSourceInfoInputBuffer,
           bool isFramework);
 
-  bool isRequiredOSSAModules() const;
-
   /// Check whether the module with a given name can be imported without
   /// importing it.
   ///

include/swift/Serialization/Validation.h

@@ -297,8 +297,6 @@ struct SearchPath {
 ///
 /// \param data A buffer containing the serialized AST. Result information
 /// refers directly into this buffer.
-/// \param requiresOSSAModules If true, necessitates the module to be
-/// compiled with -enable-ossa-modules.
 /// \param requiredSDK If not empty, only accept modules built with
 /// a compatible SDK. The StringRef represents the canonical SDK name.
 /// \param target The target triple of the current compilation for
@@ -309,7 +307,7 @@ struct SearchPath {
 /// \param[out] dependencies If present, will be populated with list of
 /// input files the module depends on, if present in INPUT_BLOCK.
 ValidationInfo validateSerializedAST(
-    StringRef data, bool requiresOSSAModules,
+    StringRef data,
     StringRef requiredSDK,
     ExtendedValidationInfo *extendedInfo = nullptr,
     SmallVectorImpl<SerializationOptions::FileDependency> *dependencies =

lib/ASTSectionImporter/ASTSectionImporter.cpp

@@ -58,7 +58,7 @@ swift::parseASTSection(MemoryBufferSerializedModuleLoader &Loader,
   // headers. Iterate over all AST modules.
   while (!buf.empty()) {
     auto info = serialization::validateSerializedAST(
-        buf, Loader.isRequiredOSSAModules(),
+        buf,
         /*requiredSDK*/StringRef());
 
     assert(info.name.size() < (2 << 10) && "name failed sanity check");

lib/DependencyScan/ModuleDependencyScanner.cpp

@@ -252,8 +252,8 @@ ModuleDependencyScanningWorker::ModuleDependencyScanningWorker(
       workerCompilerInvocation->getFrontendOptions()
           .SerializeModuleInterfaceDependencyHashes,
       workerCompilerInvocation->getFrontendOptions()
-          .shouldTrackSystemDependencies(),
-      RequireOSSAModules_t(SILOptions));
+          .shouldTrackSystemDependencies()
+      );
 
   auto loader = std::make_unique<PluginLoader>(
       *workerASTContext, /*DepTracker=*/nullptr,