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

Part for relanding #122887.

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

Author: ChuanqiXu9

clang/include/clang/AST/DeclBase.h

@@ -2722,6 +2722,9 @@ class DeclContext {
                    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 @@ class ExternalASTMerger : public ExternalASTSource {
 
   /// 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 @@ class ExternalASTSource : public RefCountedBase<ExternalASTSource> {
   /// 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 @@ class MultiplexExternalSemaSource : public ExternalSemaSource {
   /// 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 @@ class ASTReader
   /// 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 @@ class ExternalSource : public clang::ExternalASTSource {
   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;
 }