[AST] Add OriginalDC argument to ExternalASTSource::FindExternalVisibleDeclsByName (#123152)

Part for relanding https://github.com/llvm/llvm-project/pull/122887.

I split this to test where the performance regession comes from if
modules are not used.

clang/include/clang/AST/DeclBase.h

@@ -2722,6 +2722,9 @@ public:
                    bool Deserialize = false) const;
 
 private:
+  lookup_result lookupImpl(DeclarationName Name,
+                           const DeclContext *OriginalLookupDC) const;
+
   /// Whether this declaration context has had externally visible
   /// storage added since the last lookup. In this case, \c LookupPtr's
   /// invariant may not hold and needs to be fixed before we perform

clang/include/clang/AST/ExternalASTMerger.h

@@ -141,7 +141,8 @@ public:
 
   /// Implementation of the ExternalASTSource API.
   bool FindExternalVisibleDeclsByName(const DeclContext *DC,
-                                      DeclarationName Name) override;
+                                      DeclarationName Name,
+                                      const DeclContext *OriginalDC) override;
 
   /// Implementation of the ExternalASTSource API.
   void

clang/include/clang/AST/ExternalASTSource.h

@@ -145,12 +145,20 @@ public:
   /// Find all declarations with the given name in the given context,
   /// and add them to the context by calling SetExternalVisibleDeclsForName
   /// or SetNoExternalVisibleDeclsForName.
+  /// \param DC The context for lookup in. \c DC should be a primary context.
+  /// \param Name The name to look for.
+  /// \param OriginalDC The original context for lookup.  \c OriginalDC can
+  /// provide more information than \c DC. e.g., The same namespace can appear
+  /// in multiple module units. So we need the \c OriginalDC to tell us what
+  /// the module the lookup come from.
+  ///
   /// \return \c true if any declarations might have been found, \c false if
   /// we definitely have no declarations with tbis name.
   ///
   /// The default implementation of this method is a no-op returning \c false.
-  virtual bool
-  FindExternalVisibleDeclsByName(const DeclContext *DC, DeclarationName Name);
+  virtual bool FindExternalVisibleDeclsByName(const DeclContext *DC,
+                                              DeclarationName Name,
+                                              const DeclContext *OriginalDC);
 
   /// Load all the external specializations for the Decl \param D if \param
   /// OnlyPartial is false. Otherwise, load all the external **partial**

clang/include/clang/Sema/MultiplexExternalSemaSource.h

@@ -95,7 +95,8 @@ public:
   /// Find all declarations with the given name in the
   /// given context.
   bool FindExternalVisibleDeclsByName(const DeclContext *DC,
-                                      DeclarationName Name) override;
+                                      DeclarationName Name,
+                                      const DeclContext *OriginalDC) override;
 
   bool LoadExternalSpecializations(const Decl *D, bool OnlyPartial) override;
 

clang/include/clang/Serialization/ASTReader.h

@@ -2119,7 +2119,8 @@ public:
   /// The current implementation of this method just loads the entire
   /// lookup table as unmaterialized references.
   bool FindExternalVisibleDeclsByName(const DeclContext *DC,
-                                      DeclarationName Name) override;
+                                      DeclarationName Name,
+                                      const DeclContext *OriginalDC) override;
 
   /// Read all of the declarations lexically stored in a
   /// declaration context.

clang/lib/AST/DeclBase.cpp

@@ -1856,9 +1856,16 @@ DeclContext::lookup(DeclarationName Name) const {
   if (getDeclKind() == Decl::LinkageSpec || getDeclKind() == Decl::Export)
     return getParent()->lookup(Name);
 
-  const DeclContext *PrimaryContext = getPrimaryContext();
-  if (PrimaryContext != this)
-    return PrimaryContext->lookup(Name);
+  return getPrimaryContext()->lookupImpl(Name, this);
+}
+
+DeclContext::lookup_result
+DeclContext::lookupImpl(DeclarationName Name,
+                        const DeclContext *OriginalLookupDC) const {
+  assert(this == getPrimaryContext() &&
+         "lookupImpl should only be called with primary DC!");
+  assert(getDeclKind() != Decl::LinkageSpec && getDeclKind() != Decl::Export &&
+         "We shouldn't lookup in transparent DC.");
 
   // If we have an external source, ensure that any later redeclarations of this
   // context have been loaded, since they may add names to the result of this
@@ -1889,7 +1896,8 @@ DeclContext::lookup(DeclarationName Name) const {
     if (!R.second && !R.first->second.hasExternalDecls())
       return R.first->second.getLookupResult();
 
-    if (Source->FindExternalVisibleDeclsByName(this, Name) || !R.second) {
+    if (Source->FindExternalVisibleDeclsByName(this, Name, OriginalLookupDC) ||
+        !R.second) {
       if (StoredDeclsMap *Map = LookupPtr) {
         StoredDeclsMap::iterator I = Map->find(Name);
         if (I != Map->end())
@@ -2115,7 +2123,8 @@ void DeclContext::makeDeclVisibleInContextImpl(NamedDecl *D, bool Internal) {
     if (ExternalASTSource *Source = getParentASTContext().getExternalSource())
       if (hasExternalVisibleStorage() &&
           Map->find(D->getDeclName()) == Map->end())
-        Source->FindExternalVisibleDeclsByName(this, D->getDeclName());
+        Source->FindExternalVisibleDeclsByName(this, D->getDeclName(),
+                                               D->getDeclContext());
 
   // Insert this declaration into the map.
   StoredDeclsList &DeclNameEntries = (*Map)[D->getDeclName()];

clang/lib/AST/ExternalASTMerger.cpp

@@ -471,8 +471,9 @@ static bool importSpecializationsIfNeeded(Decl *D, ASTImporter *Importer) {
   return false;
 }
 
-bool ExternalASTMerger::FindExternalVisibleDeclsByName(const DeclContext *DC,
-                                                       DeclarationName Name) {
+bool ExternalASTMerger::FindExternalVisibleDeclsByName(
+    const DeclContext *DC, DeclarationName Name,
+    const DeclContext *OriginalDC) {
   llvm::SmallVector<NamedDecl *, 1> Decls;
   llvm::SmallVector<Candidate, 4> Candidates;
 

clang/lib/AST/ExternalASTSource.cpp

@@ -90,9 +90,9 @@ ExternalASTSource::GetExternalCXXBaseSpecifiers(uint64_t Offset) {
   return nullptr;
 }
 
-bool
-ExternalASTSource::FindExternalVisibleDeclsByName(const DeclContext *DC,
-                                                  DeclarationName Name) {
+bool ExternalASTSource::FindExternalVisibleDeclsByName(
+    const DeclContext *DC, DeclarationName Name,
+    const DeclContext *OriginalDC) {
   return false;
 }
 

clang/lib/Interpreter/CodeCompletion.cpp

@@ -228,7 +228,8 @@ public:
   ExternalSource(ASTContext &ChildASTCtxt, FileManager &ChildFM,
                  ASTContext &ParentASTCtxt, FileManager &ParentFM);
   bool FindExternalVisibleDeclsByName(const DeclContext *DC,
-                                      DeclarationName Name) override;
+                                      DeclarationName Name,
+                                      const DeclContext *OriginalDC) override;
   void
   completeVisibleDeclsMap(const clang::DeclContext *childDeclContext) override;
 };
@@ -270,8 +271,9 @@ ExternalSource::ExternalSource(ASTContext &ChildASTCtxt, FileManager &ChildFM,
   Importer.reset(importer);
 }
 
-bool ExternalSource::FindExternalVisibleDeclsByName(const DeclContext *DC,
-                                                    DeclarationName Name) {
+bool ExternalSource::FindExternalVisibleDeclsByName(
+    const DeclContext *DC, DeclarationName Name,
+    const DeclContext *OriginalDC) {
 
   IdentifierTable &ParentIdTable = ParentASTCtxt.Idents;
 

clang/lib/Sema/MultiplexExternalSemaSource.cpp

@@ -107,11 +107,13 @@ MultiplexExternalSemaSource::hasExternalDefinitions(const Decl *D) {
   return EK_ReplyHazy;
 }
 
-bool MultiplexExternalSemaSource::
-FindExternalVisibleDeclsByName(const DeclContext *DC, DeclarationName Name) {
+bool MultiplexExternalSemaSource::FindExternalVisibleDeclsByName(
+    const DeclContext *DC, DeclarationName Name,
+    const DeclContext *OriginalDC) {
   bool AnyDeclsFound = false;
   for (size_t i = 0; i < Sources.size(); ++i)
-    AnyDeclsFound |= Sources[i]->FindExternalVisibleDeclsByName(DC, Name);
+    AnyDeclsFound |=
+        Sources[i]->FindExternalVisibleDeclsByName(DC, Name, OriginalDC);
   return AnyDeclsFound;
 }
 

clang/lib/Serialization/ASTReader.cpp

@@ -8366,9 +8366,9 @@ void ASTReader::FindFileRegionDecls(FileID File,
         *DInfo.Mod, LocalDeclID::get(*this, *DInfo.Mod, *DIt))));
 }
 
-bool
-ASTReader::FindExternalVisibleDeclsByName(const DeclContext *DC,
-                                          DeclarationName Name) {
+bool ASTReader::FindExternalVisibleDeclsByName(const DeclContext *DC,
+                                               DeclarationName Name,
+                                               const DeclContext *OriginalDC) {
   assert(DC->hasExternalVisibleStorage() && DC == DC->getPrimaryContext() &&
          "DeclContext has no visible decls in storage");
   if (!Name)

clang/unittests/AST/ExternalASTSourceTest.cpp

@@ -67,8 +67,9 @@ TEST(ExternalASTSourceTest, FailedLookupOccursOnce) {
   struct TestSource : ExternalASTSource {
     TestSource(unsigned &Calls) : Calls(Calls) {}
 
-    bool FindExternalVisibleDeclsByName(const DeclContext *,
-                                        DeclarationName Name) override {
+    bool
+    FindExternalVisibleDeclsByName(const DeclContext *, DeclarationName Name,
+                                   const DeclContext *OriginalDC) override {
       if (Name.getAsString() == "j")
         ++Calls;
       return false;

lldb/source/Plugins/ExpressionParser/Clang/ASTUtils.h

@@ -70,9 +70,10 @@ public:
     m_Source->updateOutOfDateIdentifier(II);
   }
 
-  bool FindExternalVisibleDeclsByName(const clang::DeclContext *DC,
-                                      clang::DeclarationName Name) override {
-    return m_Source->FindExternalVisibleDeclsByName(DC, Name);
+  bool FindExternalVisibleDeclsByName(
+      const clang::DeclContext *DC, clang::DeclarationName Name,
+      const clang::DeclContext *OriginalDC) override {
+    return m_Source->FindExternalVisibleDeclsByName(DC, Name, OriginalDC);
   }
 
   bool LoadExternalSpecializations(const clang::Decl *D,
@@ -387,10 +388,11 @@ public:
     return EK_ReplyHazy;
   }
 
-  bool FindExternalVisibleDeclsByName(const clang::DeclContext *DC,
-                                      clang::DeclarationName Name) override {
+  bool FindExternalVisibleDeclsByName(
+      const clang::DeclContext *DC, clang::DeclarationName Name,
+      const clang::DeclContext *OriginalDC) override {
     for (size_t i = 0; i < Sources.size(); ++i)
-      if (Sources[i]->FindExternalVisibleDeclsByName(DC, Name))
+      if (Sources[i]->FindExternalVisibleDeclsByName(DC, Name, OriginalDC))
         return true;
     return false;
   }

lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp

@@ -99,7 +99,8 @@ void ClangASTSource::StartTranslationUnit(ASTConsumer *Consumer) {
 
 // The core lookup interface.
 bool ClangASTSource::FindExternalVisibleDeclsByName(
-    const DeclContext *decl_ctx, DeclarationName clang_decl_name) {
+    const DeclContext *decl_ctx, DeclarationName clang_decl_name,
+    const clang::DeclContext *original_dc) {
   if (!m_ast_context) {
     SetNoExternalVisibleDeclsForName(decl_ctx, clang_decl_name);
     return false;

lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.h

@@ -83,8 +83,10 @@ public:
   ///
   /// \return
   ///     Whatever SetExternalVisibleDeclsForName returns.
-  bool FindExternalVisibleDeclsByName(const clang::DeclContext *DC,
-                                      clang::DeclarationName Name) override;
+  bool
+  FindExternalVisibleDeclsByName(const clang::DeclContext *DC,
+                                 clang::DeclarationName Name,
+                                 const clang::DeclContext *OriginalDC) override;
 
   /// Enumerate all Decls in a given lexical context.
   ///
@@ -211,9 +213,10 @@ public:
   public:
     ClangASTSourceProxy(ClangASTSource &original) : m_original(original) {}
 
-    bool FindExternalVisibleDeclsByName(const clang::DeclContext *DC,
-                                        clang::DeclarationName Name) override {
-      return m_original.FindExternalVisibleDeclsByName(DC, Name);
+    bool FindExternalVisibleDeclsByName(
+        const clang::DeclContext *DC, clang::DeclarationName Name,
+        const clang::DeclContext *OriginalDC) override {
+      return m_original.FindExternalVisibleDeclsByName(DC, Name, OriginalDC);
     }
 
     void FindExternalLexicalDecls(

lldb/source/Plugins/ExpressionParser/Clang/ClangExternalASTSourceCallbacks.cpp

@@ -50,7 +50,8 @@ void ClangExternalASTSourceCallbacks::FindExternalLexicalDecls(
 }
 
 bool ClangExternalASTSourceCallbacks::FindExternalVisibleDeclsByName(
-    const clang::DeclContext *DC, clang::DeclarationName Name) {
+    const clang::DeclContext *DC, clang::DeclarationName Name,
+    const clang::DeclContext *OriginalDC) {
   llvm::SmallVector<clang::NamedDecl *, 4> decls;
   // Objective-C methods are not added into the LookupPtr when they originate
   // from an external source. SetExternalVisibleDeclsForName() adds them.

lldb/source/Plugins/ExpressionParser/Clang/ClangExternalASTSourceCallbacks.h

@@ -37,8 +37,10 @@ public:
       llvm::function_ref<bool(clang::Decl::Kind)> IsKindWeWant,
       llvm::SmallVectorImpl<clang::Decl *> &Result) override;
 
-  bool FindExternalVisibleDeclsByName(const clang::DeclContext *DC,
-                                      clang::DeclarationName Name) override;
+  bool
+  FindExternalVisibleDeclsByName(const clang::DeclContext *DC,
+                                 clang::DeclarationName Name,
+                                 const clang::DeclContext *OriginalDC) override;
 
   void CompleteType(clang::TagDecl *tag_decl) override;
 

lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCDeclVendor.cpp

@@ -29,8 +29,9 @@ public:
   AppleObjCExternalASTSource(AppleObjCDeclVendor &decl_vendor)
       : m_decl_vendor(decl_vendor) {}
 
-  bool FindExternalVisibleDeclsByName(const clang::DeclContext *decl_ctx,
-                                      clang::DeclarationName name) override {
+  bool FindExternalVisibleDeclsByName(
+      const clang::DeclContext *decl_ctx, clang::DeclarationName name,
+      const clang::DeclContext *original_dc) override {
 
     Log *log(GetLog(
         LLDBLog::Expressions)); // FIXME - a more appropriate log channel?