Revert "[C++20] [Modules] Support module level lookup (#122887)"

This reverts commit 7201cae.

Author: ChuanqiXu9

clang/docs/ReleaseNotes.rst

@@ -316,8 +316,6 @@ C++23 Feature Support
 C++20 Feature Support
 ^^^^^^^^^^^^^^^^^^^^^
 
-- Implemented module level lookup for C++20 modules. (#GH90154)
-
 
 Resolutions to C++ Defect Reports
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

clang/include/clang/AST/DeclBase.h

@@ -836,10 +836,6 @@ class alignas(8) Decl {
     return isFromASTFile() ? getImportedOwningModule() : getLocalOwningModule();
   }
 
-  /// Get the top level owning named module that owns this declaration if any.
-  /// \returns nullptr if the declaration is not owned by a named module.
-  Module *getTopLevelOwningNamedModule() const;
-
   /// Get the module that owns this declaration for linkage purposes.
   /// There only ever is such a standard C++ module.
   Module *getOwningModuleForLinkage() const;
@@ -2726,12 +2722,6 @@ class DeclContext {
                    bool Deserialize = false) const;
 
 private:
-  /// Lookup all external visible declarations and the external declarations
-  /// within the same module specified by \c NamedModule. We can't
-  /// get it from \c this since the same declaration may be declared in
-  /// multiple modules. e.g., namespace.
-  lookup_result lookupImpl(DeclarationName Name, Module *NamedModule) 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

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

clang/include/clang/AST/ExternalASTSource.h

@@ -51,7 +51,6 @@ class RecordDecl;
 class Selector;
 class Stmt;
 class TagDecl;
-class Module;
 
 /// Abstract interface for external sources of AST nodes.
 ///
@@ -146,20 +145,12 @@ 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.
-  /// \param Name the name of the declarations to find.
-  /// \param NamedModule find declarations visible to the given module
-  /// \c NamedModule . This may be different from owning module of \c DC since
-  /// there are declarations (e.g., namespace declaration) can appear in
-  /// multiple modules.
-  ///
-  /// \return \c true if any declarations might have been found, and \c false
-  /// if we definitely have no declarations with this name.
+  /// \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,
-                                              Module *NamedModule);
+  virtual bool
+  FindExternalVisibleDeclsByName(const DeclContext *DC, DeclarationName Name);
 
   /// 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

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

clang/include/clang/Serialization/ASTBitCodes.h

@@ -738,8 +738,6 @@ enum ASTRecordTypes {
   CXX_ADDED_TEMPLATE_SPECIALIZATION = 74,
 
   CXX_ADDED_TEMPLATE_PARTIAL_SPECIALIZATION = 75,
-
-  UPDATE_MODULE_LOCAL_VISIBLE = 76,
 };
 
 /// Record types used within a source manager block.
@@ -1336,10 +1334,6 @@ enum DeclCode {
   /// into a DeclContext via DeclContext::lookup.
   DECL_CONTEXT_VISIBLE,
 
-  /// A record containing the set of declarations that are
-  /// only visible from DeclContext in the same module.
-  DECL_CONTEXT_MODULE_LOCAL_VISIBLE,
-
   /// A LabelDecl record.
   DECL_LABEL,
 

clang/include/clang/Serialization/ASTReader.h

@@ -353,7 +353,6 @@ class ASTIdentifierLookupTrait;
 
 /// The on-disk hash table(s) used for DeclContext name lookup.
 struct DeclContextLookupTable;
-struct ModuleLocalLookupTable;
 
 /// The on-disk hash table(s) used for specialization decls.
 struct LazySpecializationInfoLookupTable;
@@ -524,14 +523,9 @@ class ASTReader
   /// in the chain.
   DeclUpdateOffsetsMap DeclUpdateOffsets;
 
-  struct LookupBlockOffsets {
-    uint64_t LexicalOffset;
-    uint64_t VisibleOffset;
-    uint64_t ModuleLocalOffset;
-  };
-
   using DelayedNamespaceOffsetMapTy =
-      llvm::DenseMap<GlobalDeclID, LookupBlockOffsets>;
+      llvm::DenseMap<GlobalDeclID, std::pair</*LexicalOffset*/ uint64_t,
+                                             /*VisibleOffset*/ uint64_t>>;
 
   /// Mapping from global declaration IDs to the lexical and visible block
   /// offset for delayed namespace in reduced BMI.
@@ -637,9 +631,6 @@ class ASTReader
   /// Map from a DeclContext to its lookup tables.
   llvm::DenseMap<const DeclContext *,
                  serialization::reader::DeclContextLookupTable> Lookups;
-  llvm::DenseMap<const DeclContext *,
-                 serialization::reader::ModuleLocalLookupTable>
-      ModuleLocalLookups;
 
   using SpecLookupTableTy =
       llvm::DenseMap<const Decl *,
@@ -668,8 +659,6 @@ class ASTReader
   /// Updates to the visible declarations of declaration contexts that
   /// haven't been loaded yet.
   llvm::DenseMap<GlobalDeclID, DeclContextVisibleUpdates> PendingVisibleUpdates;
-  llvm::DenseMap<GlobalDeclID, DeclContextVisibleUpdates>
-      PendingModuleLocalVisibleUpdates;
 
   using SpecializationsUpdate = SmallVector<UpdateData, 1>;
   using SpecializationsUpdateMap =
@@ -707,8 +696,7 @@ class ASTReader
   /// Read the record that describes the visible contents of a DC.
   bool ReadVisibleDeclContextStorage(ModuleFile &M,
                                      llvm::BitstreamCursor &Cursor,
-                                     uint64_t Offset, GlobalDeclID ID,
-                                     bool IsModuleLocal);
+                                     uint64_t Offset, GlobalDeclID ID);
 
   bool ReadSpecializations(ModuleFile &M, llvm::BitstreamCursor &Cursor,
                            uint64_t Offset, Decl *D, bool IsPartial);
@@ -1144,10 +1132,6 @@ class ASTReader
   /// Number of visible decl contexts read/total.
   unsigned NumVisibleDeclContextsRead = 0, TotalVisibleDeclContexts = 0;
 
-  /// Number of module local visible decl contexts read/total.
-  unsigned NumModuleLocalVisibleDeclContexts = 0,
-           TotalModuleLocalVisibleDeclContexts = 0;
-
   /// Total size of modules, in bits, currently loaded
   uint64_t TotalModulesSizeInBits = 0;
 
@@ -1460,9 +1444,6 @@ class ASTReader
   const serialization::reader::DeclContextLookupTable *
   getLoadedLookupTables(DeclContext *Primary) const;
 
-  const serialization::reader::ModuleLocalLookupTable *
-  getModuleLocalLookupTables(DeclContext *Primary) const;
-
   /// Get the loaded specializations lookup tables for \p D,
   /// if any.
   serialization::reader::LazySpecializationInfoLookupTable *
@@ -2138,8 +2119,7 @@ class ASTReader
   /// The current implementation of this method just loads the entire
   /// lookup table as unmaterialized references.
   bool FindExternalVisibleDeclsByName(const DeclContext *DC,
-                                      DeclarationName Name,
-                                      Module *NamedModule) override;
+                                      DeclarationName Name) override;
 
   /// Read all of the declarations lexically stored in a
   /// declaration context.
@@ -2627,10 +2607,6 @@ inline bool shouldSkipCheckingODR(const Decl *D) {
          (D->isFromGlobalModule() || D->isFromHeaderUnit());
 }
 
-/// Calculate a hash value for the primary module name of the given module.
-/// \returns std::nullopt if M is not a C++ standard module.
-std::optional<unsigned> getPrimaryModuleHash(const Module *M);
-
 } // namespace clang
 
 #endif // LLVM_CLANG_SERIALIZATION_ASTREADER_H

clang/include/clang/Serialization/ASTWriter.h

@@ -492,10 +492,6 @@ class ASTWriter : public ASTDeserializationListener,
   /// file.
   unsigned NumVisibleDeclContexts = 0;
 
-  /// The number of module local visible declcontexts written to the AST
-  /// file.
-  unsigned NumModuleLocalDeclContexts = 0;
-
   /// A mapping from each known submodule to its ID number, which will
   /// be a positive integer.
   llvm::DenseMap<const Module *, unsigned> SubmoduleIDs;
@@ -591,15 +587,11 @@ class ASTWriter : public ASTDeserializationListener,
   uint64_t WriteSpecializationInfoLookupTable(
       const NamedDecl *D, llvm::SmallVectorImpl<const Decl *> &Specializations,
       bool IsPartial);
-  void
-  GenerateNameLookupTable(ASTContext &Context, const DeclContext *DC,
-                          llvm::SmallVectorImpl<char> &LookupTable,
-                          llvm::SmallVectorImpl<char> &ModuleLocalLookupTable);
+  void GenerateNameLookupTable(ASTContext &Context, const DeclContext *DC,
+                               llvm::SmallVectorImpl<char> &LookupTable);
   uint64_t WriteDeclContextLexicalBlock(ASTContext &Context,
                                         const DeclContext *DC);
-  void WriteDeclContextVisibleBlock(ASTContext &Context, DeclContext *DC,
-                                    uint64_t &VisibleBlockOffset,
-                                    uint64_t &ModuleLocalBlockOffset);
+  uint64_t WriteDeclContextVisibleBlock(ASTContext &Context, DeclContext *DC);
   void WriteTypeDeclOffsets();
   void WriteFileDeclIDsMap();
   void WriteComments(ASTContext &Context);
@@ -632,9 +624,7 @@ class ASTWriter : public ASTDeserializationListener,
   unsigned DeclParmVarAbbrev = 0;
   unsigned DeclContextLexicalAbbrev = 0;
   unsigned DeclContextVisibleLookupAbbrev = 0;
-  unsigned DeclModuleLocalVisibleLookupAbbrev = 0;
   unsigned UpdateVisibleAbbrev = 0;
-  unsigned ModuleLocalUpdateVisibleAbbrev = 0;
   unsigned DeclRecordAbbrev = 0;
   unsigned DeclTypedefAbbrev = 0;
   unsigned DeclVarAbbrev = 0;

clang/lib/AST/DeclBase.cpp

@@ -1850,28 +1850,15 @@ void DeclContext::buildLookupImpl(DeclContext *DCtx, bool Internal) {
   }
 }
 
-Module *Decl::getTopLevelOwningNamedModule() const {
-  if (getOwningModule() &&
-      getOwningModule()->getTopLevelModule()->isNamedModule())
-    return getOwningModule()->getTopLevelModule();
-
-  return nullptr;
-}
-
 DeclContext::lookup_result
 DeclContext::lookup(DeclarationName Name) const {
-  return lookupImpl(Name, cast<Decl>(this)->getTopLevelOwningNamedModule());
-}
-
-DeclContext::lookup_result DeclContext::lookupImpl(DeclarationName Name,
-                                                   Module *NamedModule) const {
   // For transparent DeclContext, we should lookup in their enclosing context.
   if (getDeclKind() == Decl::LinkageSpec || getDeclKind() == Decl::Export)
-    return getParent()->lookupImpl(Name, NamedModule);
+    return getParent()->lookup(Name);
 
   const DeclContext *PrimaryContext = getPrimaryContext();
   if (PrimaryContext != this)
-    return PrimaryContext->lookupImpl(Name, NamedModule);
+    return PrimaryContext->lookup(Name);
 
   // 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
@@ -1902,8 +1889,7 @@ DeclContext::lookup_result DeclContext::lookupImpl(DeclarationName Name,
     if (!R.second && !R.first->second.hasExternalDecls())
       return R.first->second.getLookupResult();
 
-    if (Source->FindExternalVisibleDeclsByName(this, Name, NamedModule) ||
-        !R.second) {
+    if (Source->FindExternalVisibleDeclsByName(this, Name) || !R.second) {
       if (StoredDeclsMap *Map = LookupPtr) {
         StoredDeclsMap::iterator I = Map->find(Name);
         if (I != Map->end())
@@ -2129,8 +2115,7 @@ 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(), D->getTopLevelOwningNamedModule());
+        Source->FindExternalVisibleDeclsByName(this, D->getDeclName());
 
   // Insert this declaration into the map.
   StoredDeclsList &DeclNameEntries = (*Map)[D->getDeclName()];

clang/lib/AST/ExternalASTMerger.cpp

@@ -472,8 +472,7 @@ static bool importSpecializationsIfNeeded(Decl *D, ASTImporter *Importer) {
 }
 
 bool ExternalASTMerger::FindExternalVisibleDeclsByName(const DeclContext *DC,
-                                                       DeclarationName Name,
-                                                       Module *NamedModule) {
+                                                       DeclarationName Name) {
   llvm::SmallVector<NamedDecl *, 1> Decls;
   llvm::SmallVector<Candidate, 4> Candidates;