diff --git a/include/clang/Serialization/ASTReader.h b/include/clang/Serialization/ASTReader.h
index bbcead0..04da346 100644
--- a/include/clang/Serialization/ASTReader.h
+++ b/include/clang/Serialization/ASTReader.h
@@ -384,7 +384,8 @@
   GlobalSubmoduleMapType GlobalSubmoduleMap;
 
   /// \brief A set of hidden declarations.
-  typedef llvm::SmallVector<Decl *, 2> HiddenNames;
+  typedef llvm::SmallVector<llvm::PointerUnion<Decl *, IdentifierInfo *>, 2>
+    HiddenNames;
   
   typedef llvm::DenseMap<Module *, HiddenNames> HiddenNamesMapType;
 
@@ -1343,8 +1344,17 @@
 
   /// \brief Note that the identifier is a macro whose record will be loaded
   /// from the given AST file at the given (file-local) offset.
-  void SetIdentifierIsMacro(IdentifierInfo *II, ModuleFile &F,
-                            uint64_t Offset);
+  ///
+  /// \param II The name of the macro.
+  ///
+  /// \param F The module file from which the macro definition was deserialized.
+  ///
+  /// \param Offset The offset into the module file at which the macro 
+  /// definition is located.
+  ///
+  /// \param Visible Whether the macro should be made visible.
+  void setIdentifierIsMacro(IdentifierInfo *II, ModuleFile &F,
+                            uint64_t Offset, bool Visible);
 
   /// \brief Read the set of macros defined by this external macro source.
   virtual void ReadDefinedMacros();
diff --git a/include/clang/Serialization/ASTWriter.h b/include/clang/Serialization/ASTWriter.h
index 27dccb0..1abce18 100644
--- a/include/clang/Serialization/ASTWriter.h
+++ b/include/clang/Serialization/ASTWriter.h
@@ -388,11 +388,7 @@
   void WriteHeaderSearch(const HeaderSearch &HS, StringRef isysroot);
   void WritePreprocessorDetail(PreprocessingRecord &PPRec);
   void WriteSubmodules(Module *WritingModule);
-                    
-  /// \brief Infer the submodule ID that contains an entity at the given
-  /// source location.
-  serialization::SubmoduleID inferSubmoduleIDFromLocation(SourceLocation Loc);
-                    
+                                        
   void WritePragmaDiagnosticMappings(const DiagnosticsEngine &Diag);
   void WriteCXXBaseSpecifiersOffsets();
   void WriteType(QualType T);
@@ -607,6 +603,10 @@
     return DeclsToRewrite.count(D);
   }
 
+  /// \brief Infer the submodule ID that contains an entity at the given
+  /// source location.
+  serialization::SubmoduleID inferSubmoduleIDFromLocation(SourceLocation Loc);
+
   /// \brief Note that the identifier II occurs at the given offset
   /// within the identifier table.
   void SetIdentifierOffset(const IdentifierInfo *II, uint32_t Offset);
diff --git a/lib/Serialization/ASTReader.cpp b/lib/Serialization/ASTReader.cpp
index a083e24..4594a39 100644
--- a/lib/Serialization/ASTReader.cpp
+++ b/lib/Serialization/ASTReader.cpp
@@ -562,8 +562,28 @@
   if (hasMacroDefinition) {
     // FIXME: Check for conflicts?
     uint32_t Offset = ReadUnalignedLE32(d);
-    Reader.SetIdentifierIsMacro(II, F, Offset);
-    DataLen -= 4;
+    unsigned LocalSubmoduleID = ReadUnalignedLE32(d);
+    
+    // Determine whether this macro definition should be visible now, or
+    // whether it is in a hidden submodule.
+    bool Visible = true;
+    if (SubmoduleID GlobalSubmoduleID
+          = Reader.getGlobalSubmoduleID(F, LocalSubmoduleID)) {
+      if (Module *Owner = Reader.getSubmodule(GlobalSubmoduleID)) {
+        if (Owner->NameVisibility == Module::Hidden) {
+          // The owning module is not visible, and this macro definition should
+          // not be, either.
+          Visible = false;
+          
+          // Note that this macro definition was hidden because its owning 
+          // module is not yet visible.
+          Reader.HiddenNamesMap[Owner].push_back(II);
+        }
+      } 
+    }
+    
+    Reader.setIdentifierIsMacro(II, F, Offset, Visible);
+    DataLen -= 8;
   }
 
   Reader.SetIdentifierInfo(ID, II);
@@ -1454,10 +1474,12 @@
   return HFI;
 }
 
-void ASTReader::SetIdentifierIsMacro(IdentifierInfo *II, ModuleFile &F,
-                                     uint64_t LocalOffset) {
-  // Note that this identifier has a macro definition.
-  II->setHasMacroDefinition(true);
+void ASTReader::setIdentifierIsMacro(IdentifierInfo *II, ModuleFile &F,
+                                     uint64_t LocalOffset, bool Visible) {
+  if (Visible) {
+    // Note that this identifier has a macro definition.
+    II->setHasMacroDefinition(true);
+  }
   
   // Adjust the offset to a global offset.
   UnreadMacroRecordOffsets[II] = F.GlobalBitOffset + LocalOffset;
@@ -2440,8 +2462,12 @@
 }
 
 void ASTReader::makeNamesVisible(const HiddenNames &Names) {
-  for (unsigned I = 0, N = Names.size(); I != N; ++I)
-    Names[I]->ModulePrivate = false;    
+  for (unsigned I = 0, N = Names.size(); I != N; ++I) {
+    if (Decl *D = Names[I].dyn_cast<Decl *>())
+      D->ModulePrivate = false;
+    else
+      Names[I].get<IdentifierInfo *>()->setHasMacroDefinition(true);
+  }
 }
 
 void ASTReader::makeModuleVisible(Module *Mod, 
diff --git a/lib/Serialization/ASTWriter.cpp b/lib/Serialization/ASTWriter.cpp
index 1b554ef..5580f90 100644
--- a/lib/Serialization/ASTWriter.cpp
+++ b/lib/Serialization/ASTWriter.cpp
@@ -2423,7 +2423,7 @@
     if (isInterestingIdentifier(II, Macro)) {
       DataLen += 2; // 2 bytes for builtin ID, flags
       if (hasMacroDefinition(II, Macro))
-        DataLen += 4;
+        DataLen += 8;
       
       for (IdentifierResolver::iterator D = IdResolver.begin(II),
                                      DEnd = IdResolver.end();
@@ -2465,9 +2465,12 @@
     Bits = (Bits << 1) | unsigned(II->isCPlusPlusOperatorKeyword());
     clang::io::Emit16(Out, Bits);
 
-    if (HasMacroDefinition)
+    if (HasMacroDefinition) {
       clang::io::Emit32(Out, Writer.getMacroOffset(II));
-
+      clang::io::Emit32(Out, 
+        Writer.inferSubmoduleIDFromLocation(Macro->getDefinitionLoc()));
+    }
+    
     // Emit the declaration IDs in reverse order, because the
     // IdentifierResolver provides the declarations as they would be
     // visible (e.g., the function "stat" would come before the struct
diff --git a/test/Modules/Inputs/submodules/hash_map.h b/test/Modules/Inputs/submodules/hash_map.h
index 56f0749..ce85984 100644
--- a/test/Modules/Inputs/submodules/hash_map.h
+++ b/test/Modules/Inputs/submodules/hash_map.h
@@ -1 +1,4 @@
 template<typename Key, typename Data> class hash_map { };
+
+#define HAVE_HASH_MAP
+
diff --git a/test/Modules/Inputs/submodules/type_traits.h b/test/Modules/Inputs/submodules/type_traits.h
index 9ef9006..4dad090 100644
--- a/test/Modules/Inputs/submodules/type_traits.h
+++ b/test/Modules/Inputs/submodules/type_traits.h
@@ -7,3 +7,6 @@
 struct remove_reference<T&> {
   typedef T type;
 };
+
+#define HAVE_TYPE_TRAITS
+
diff --git a/test/Modules/Inputs/submodules/vector.h b/test/Modules/Inputs/submodules/vector.h
index 2dcf3e5..8e1cdc8 100644
--- a/test/Modules/Inputs/submodules/vector.h
+++ b/test/Modules/Inputs/submodules/vector.h
@@ -1 +1,3 @@
 template<typename T> class vector { };
+
+#define HAVE_VECTOR
diff --git a/test/Modules/submodules-preprocess.cpp b/test/Modules/submodules-preprocess.cpp
index 1f0f3775..ed51b45 100644
--- a/test/Modules/submodules-preprocess.cpp
+++ b/test/Modules/submodules-preprocess.cpp
@@ -3,12 +3,58 @@
 
 __import_module__ std.vector;
 
-vector<int> vi;
-remove_reference<int&>::type *int_ptr = 0;
+#ifndef HAVE_VECTOR
+#  error HAVE_VECTOR macro is not available (but should be)
+#endif
+
+#ifdef HAVE_TYPE_TRAITS
+#  error HAVE_TYPE_TRAITS_MAP macro is available (but shouldn't be)
+#endif
+
+#ifdef HAVE_HASH_MAP
+#  error HAVE_HASH_MAP macro is available (but shouldn't be)
+#endif
 
 __import_module__ std.typetraits; // expected-error{{no submodule named 'typetraits' in module 'std'; did you mean 'type_traits'?}}
 
-vector<float> vf;
-remove_reference<int&>::type *int_ptr2 = 0;
+#ifndef HAVE_VECTOR
+#  error HAVE_VECTOR macro is not available (but should be)
+#endif
+
+#ifndef HAVE_TYPE_TRAITS
+#  error HAVE_TYPE_TRAITS_MAP macro is not available (but should be)
+#endif
+
+#ifdef HAVE_HASH_MAP
+#  error HAVE_HASH_MAP macro is available (but shouldn't be)
+#endif
 
 __import_module__ std.vector.compare; // expected-error{{no submodule named 'compare' in module 'std.vector'}}
+
+__import_module__ std; // import everything in 'std'
+
+#ifndef HAVE_VECTOR
+#  error HAVE_VECTOR macro is not available (but should be)
+#endif
+
+#ifndef HAVE_TYPE_TRAITS
+#  error HAVE_TYPE_TRAITS_MAP macro is not available (but should be)
+#endif
+
+#ifdef HAVE_HASH_MAP
+#  error HAVE_HASH_MAP macro is available (but shouldn't be)
+#endif
+
+__import_module__ std.hash_map;
+
+#ifndef HAVE_VECTOR
+#  error HAVE_VECTOR macro is not available (but should be)
+#endif
+
+#ifndef HAVE_TYPE_TRAITS
+#  error HAVE_TYPE_TRAITS_MAP macro is not available (but should be)
+#endif
+
+#ifndef HAVE_HASH_MAP
+#  error HAVE_HASH_MAP macro is not available (but should be)
+#endif