Use a SetVector when looking up the SPI attributes on imports

Using a SetVector fixes an issue where many source files imported the
same SPI group from the same module, the emitted private textual
interfaces superfluously repeated the `@_spi` attribute on the import.

rdar://problem/63681845

Author: xymus

include/swift/AST/FileUnit.h

@@ -107,8 +107,8 @@ class FileUnit : public DeclContext {
   /// Find all SPI names imported from \p importedModule by this module,
   /// collecting the identifiers in \p spiGroups.
   virtual void lookupImportedSPIGroups(
-                               const ModuleDecl *importedModule,
-                               SmallVectorImpl<Identifier> &spiGroups) const {};
+                            const ModuleDecl *importedModule,
+                            SmallSetVector<Identifier, 4> &spiGroups) const {};
 
 protected:
   /// Look up an operator declaration. Do not call directly, use

include/swift/AST/Module.h

@@ -575,8 +575,9 @@ class ModuleDecl : public DeclContext, public TypeDecl {
 
   /// Find all SPI names imported from \p importedModule by this module,
   /// collecting the identifiers in \p spiGroups.
-  void lookupImportedSPIGroups(const ModuleDecl *importedModule,
-                          SmallVectorImpl<Identifier> &spiGroups) const;
+  void lookupImportedSPIGroups(
+                         const ModuleDecl *importedModule,
+                         llvm::SmallSetVector<Identifier, 4> &spiGroups) const;
 
   /// \sa getImportedModules
   enum class ImportFilterKind {

include/swift/AST/SourceFile.h

@@ -365,8 +365,9 @@ class SourceFile final : public FileUnit {
   /// Find all SPI names imported from \p importedModule by this file,
   /// collecting the identifiers in \p spiGroups.
   virtual void
-  lookupImportedSPIGroups(const ModuleDecl *importedModule,
-                         SmallVectorImpl<Identifier> &spiGroups) const override;
+  lookupImportedSPIGroups(
+                const ModuleDecl *importedModule,
+                llvm::SmallSetVector<Identifier, 4> &spiGroups) const override;
 
   // Is \p targetDecl accessible as an explictly imported SPI from this file?
   bool isImportedAsSPI(const ValueDecl *targetDecl) const;

include/swift/Serialization/SerializedModuleLoader.h

@@ -359,8 +359,9 @@ class SerializedASTFile final : public LoadedFile {
          SmallVectorImpl<AbstractFunctionDecl *> &results) const override;
 
   virtual void
-  lookupImportedSPIGroups(const ModuleDecl *importedModule,
-                         SmallVectorImpl<Identifier> &spiGroups) const override;
+  lookupImportedSPIGroups(
+                const ModuleDecl *importedModule,
+                llvm::SmallSetVector<Identifier, 4> &spiGroups) const override;
 
   Optional<CommentInfo> getCommentForDecl(const Decl *D) const override;
 

lib/AST/Module.cpp

@@ -639,8 +639,9 @@ void ModuleDecl::lookupObjCMethods(
   FORWARD(lookupObjCMethods, (selector, results));
 }
 
-void ModuleDecl::lookupImportedSPIGroups(const ModuleDecl *importedModule,
-                                    SmallVectorImpl<Identifier> &spiGroups) const {
+void ModuleDecl::lookupImportedSPIGroups(
+                        const ModuleDecl *importedModule,
+                        llvm::SmallSetVector<Identifier, 4> &spiGroups) const {
   FORWARD(lookupImportedSPIGroups, (importedModule, spiGroups));
 }
 
@@ -2190,31 +2191,29 @@ bool SourceFile::isImportedImplementationOnly(const ModuleDecl *module) const {
   return !imports.isImportedBy(module, getParentModule());
 }
 
-void SourceFile::lookupImportedSPIGroups(const ModuleDecl *importedModule,
-                                    SmallVectorImpl<Identifier> &spiGroups) const {
+void SourceFile::lookupImportedSPIGroups(
+                        const ModuleDecl *importedModule,
+                        llvm::SmallSetVector<Identifier, 4> &spiGroups) const {
   for (auto &import : Imports) {
     if (import.importOptions.contains(ImportFlags::SPIAccessControl) &&
         importedModule == std::get<ModuleDecl*>(import.module)) {
       auto importedSpis = import.spiGroups;
-      spiGroups.append(importedSpis.begin(), importedSpis.end());
+      spiGroups.insert(importedSpis.begin(), importedSpis.end());
     }
   }
 }
 
 bool SourceFile::isImportedAsSPI(const ValueDecl *targetDecl) const {
   auto targetModule = targetDecl->getModuleContext();
-  SmallVector<Identifier, 4> importedSPIGroups;
+  llvm::SmallSetVector<Identifier, 4> importedSPIGroups;
   lookupImportedSPIGroups(targetModule, importedSPIGroups);
   if (importedSPIGroups.empty()) return false;
 
   auto declSPIGroups = targetDecl->getSPIGroups();
 
-  // Note: If we reach a point where there are many SPI imports or SPI groups
-  // on decls we could optimize this further by using a set.
-  for (auto importedSPI : importedSPIGroups)
-    for (auto declSPI : declSPIGroups)
-      if (importedSPI == declSPI)
-        return true;
+  for (auto declSPI : declSPIGroups)
+    if (importedSPIGroups.count(declSPI))
+      return true;
 
   return false;
 }

lib/Frontend/ModuleInterfaceSupport.cpp

@@ -139,7 +139,7 @@ static void printImports(raw_ostream &out,
       continue;
     }
 
-    llvm::SmallVector<Identifier, 4> spis;
+    llvm::SmallSetVector<Identifier, 4> spis;
     M->lookupImportedSPIGroups(importedModule, spis);
 
     // Only print implementation-only imports which have an SPI import.

lib/Serialization/ModuleFile.cpp

@@ -2665,13 +2665,14 @@ void ModuleFile::lookupObjCMethods(
   }
 }
 
-void ModuleFile::lookupImportedSPIGroups(const ModuleDecl *importedModule,
-                                    SmallVectorImpl<Identifier> &spiGroups) const {
+void ModuleFile::lookupImportedSPIGroups(
+                        const ModuleDecl *importedModule,
+                        llvm::SmallSetVector<Identifier, 4> &spiGroups) const {
   for (auto &dep : Dependencies) {
     auto depSpis = dep.spiGroups;
     if (dep.Import.second == importedModule &&
         !depSpis.empty()) {
-      spiGroups.append(depSpis.begin(), depSpis.end());
+      spiGroups.insert(depSpis.begin(), depSpis.end());
     }
   }
 }

lib/Serialization/ModuleFile.h

@@ -816,8 +816,9 @@ class ModuleFile
 
   /// Find all SPI names imported from \p importedModule by this module,
   /// collecting the identifiers in \p spiGroups.
-  void lookupImportedSPIGroups(const ModuleDecl *importedModule,
-                              SmallVectorImpl<Identifier> &spiGroups) const;
+  void lookupImportedSPIGroups(
+                         const ModuleDecl *importedModule,
+                         llvm::SmallSetVector<Identifier, 4> &spiGroups) const;
 
   /// Reports all link-time dependencies.
   void collectLinkLibraries(ModuleDecl::LinkLibraryCallback callback) const;

lib/Serialization/Serialization.cpp

@@ -1085,7 +1085,7 @@ void Serializer::writeInputBlock(const SerializationOptions &options) {
     else
       stableImportControl = ImportControl::ImplementationOnly;
 
-    SmallVector<Identifier, 4> spis;
+    llvm::SmallSetVector<Identifier, 4> spis;
     M->lookupImportedSPIGroups(import.second, spis);
 
     ImportedModule.emit(ScratchRecord,

lib/Serialization/SerializedModuleLoader.cpp

@@ -1149,8 +1149,9 @@ void SerializedASTFile::lookupObjCMethods(
   File.lookupObjCMethods(selector, results);
 }
 
-void SerializedASTFile::lookupImportedSPIGroups(const ModuleDecl *importedModule,
-                                           SmallVectorImpl<Identifier> &spiGroups) const {
+void SerializedASTFile::lookupImportedSPIGroups(
+                        const ModuleDecl *importedModule,
+                        llvm::SmallSetVector<Identifier, 4> &spiGroups) const {
   File.lookupImportedSPIGroups(importedModule, spiGroups);
 }