diff --git a/docs/Modules.rst b/docs/Modules.rst
index ed6f817..af42461 100644
--- a/docs/Modules.rst
+++ b/docs/Modules.rst
@@ -317,11 +317,12 @@
 
 .. parsed-literal::
 
-  ``config_macros`` ``export``     ``private``
+  ``config_macros`` ``export_as``  ``private``
   ``conflict``      ``framework``  ``requires``
   ``exclude``       ``header``     ``textual``
   ``explicit``      ``link``       ``umbrella``
   ``extern``        ``module``     ``use``
+  ``export``
 
 Module map file
 ---------------
@@ -381,6 +382,7 @@
     *umbrella-dir-declaration*
     *submodule-declaration*
     *export-declaration*
+    *export-as-declaration*
     *use-declaration*
     *link-declaration*
     *config-macros-declaration*
@@ -660,6 +662,30 @@
   compatibility for programs that rely on transitive inclusion (i.e.,
   all of them).
 
+Re-export Declaration
+~~~~~~~~~~~~~~~~~~
+An *export-as-declaration* specifies that the current module will have
+its interface re-exported by the named module.
+
+.. parsed-literal::
+
+  *export-as-declaration*:
+    ``export_as`` *identifier*
+
+The *export-as-declaration* names the module that the current
+module will be re-exported through. Only top-level modules
+can be re-exported, and any given module may only be re-exported
+through a single module.
+
+**Example:** In the following example, the module ``MyFrameworkCore``
+will be re-exported via the module ``MyFramework``:
+
+.. parsed-literal::
+
+  module MyFrameworkCore {
+    export_as MyFramework
+  }
+
 Use declaration
 ~~~~~~~~~~~~~~~
 A *use-declaration* specifies another module that the current top-level module
diff --git a/include/clang/Basic/DiagnosticLexKinds.td b/include/clang/Basic/DiagnosticLexKinds.td
index 706881b..2f52005 100644
--- a/include/clang/Basic/DiagnosticLexKinds.td
+++ b/include/clang/Basic/DiagnosticLexKinds.td
@@ -674,6 +674,13 @@
   "expected integer literal as value for header attribute '%0'">;
 def err_mmap_expected_header_attribute : Error<
   "expected a header attribute name ('size' or 'mtime')">;
+def err_mmap_conflicting_export_as : Error<
+  "conflicting re-export of module '%0' as '%1' or '%2'">;
+def warn_mmap_redundant_export_as : Warning<
+  "module '%0' already re-exported as '%1'">,
+  InGroup<PrivateModule>;
+def err_mmap_submodule_export_as : Error<
+  "only top-level modules can be re-exported as public">;
 
 def warn_auto_module_import : Warning<
   "treating #%select{include|import|include_next|__include_macros}0 as an "
diff --git a/include/clang/Basic/Module.h b/include/clang/Basic/Module.h
index c13617b..453b062 100644
--- a/include/clang/Basic/Module.h
+++ b/include/clang/Basic/Module.h
@@ -95,6 +95,10 @@
 
   /// \brief The name of the umbrella entry, as written in the module map.
   std::string UmbrellaAsWritten;
+
+  /// \brief The module through which entities defined in this module will
+  /// eventually be exposed, for use in "private" modules.
+  std::string ExportAsModule;
   
 private:
   /// \brief The submodules of this module, indexed by name.
diff --git a/include/clang/Serialization/ASTBitCodes.h b/include/clang/Serialization/ASTBitCodes.h
index 9227b33..f0f17c9 100644
--- a/include/clang/Serialization/ASTBitCodes.h
+++ b/include/clang/Serialization/ASTBitCodes.h
@@ -716,6 +716,9 @@
       /// \brief Specifies some declarations with initializers that must be
       /// emitted to initialize the module.
       SUBMODULE_INITIALIZERS = 16,
+      /// \brief Specifies the name of the module that will eventually
+      /// re-export the entities in this module.
+      SUBMODULE_EXPORT_AS = 17,
     };
 
     /// \brief Record types used within a comments block.
diff --git a/lib/Basic/Module.cpp b/lib/Basic/Module.cpp
index 671fec6..3ac9679 100644
--- a/lib/Basic/Module.cpp
+++ b/lib/Basic/Module.cpp
@@ -448,6 +448,11 @@
     }
   }
 
+  if (!ExportAsModule.empty()) {
+    OS.indent(Indent + 2);
+    OS << "export_as" << ExportAsModule << "\n";
+  }
+  
   for (submodule_const_iterator MI = submodule_begin(), MIEnd = submodule_end();
        MI != MIEnd; ++MI)
     // Print inferred subframework modules so that we don't need to re-infer
diff --git a/lib/Frontend/InitHeaderSearch.cpp b/lib/Frontend/InitHeaderSearch.cpp
index 1d7c8a0..4bde9d0 100644
--- a/lib/Frontend/InitHeaderSearch.cpp
+++ b/lib/Frontend/InitHeaderSearch.cpp
@@ -485,6 +485,7 @@
     if (triple.isOSDarwin()) {
       AddPath("/System/Library/Frameworks", System, true);
       AddPath("/Library/Frameworks", System, true);
+      AddPath("/System/Library/PrivateFrameworks", System, true);
     }
   }
 }
diff --git a/lib/Lex/ModuleMap.cpp b/lib/Lex/ModuleMap.cpp
index 0e8fe95..8c0da2c 100644
--- a/lib/Lex/ModuleMap.cpp
+++ b/lib/Lex/ModuleMap.cpp
@@ -1203,6 +1203,7 @@
       ExcludeKeyword,
       ExplicitKeyword,
       ExportKeyword,
+      ExportAsKeyword,
       ExternKeyword,
       FrameworkKeyword,
       LinkKeyword,
@@ -1314,6 +1315,7 @@
                          SourceLocation LeadingLoc);
     void parseUmbrellaDirDecl(SourceLocation UmbrellaLoc);
     void parseExportDecl();
+    void parseExportAsDecl();
     void parseUseDecl();
     void parseLinkDecl();
     void parseConfigMacros();
@@ -1365,6 +1367,7 @@
                  .Case("exclude", MMToken::ExcludeKeyword)
                  .Case("explicit", MMToken::ExplicitKeyword)
                  .Case("export", MMToken::ExportKeyword)
+                 .Case("export_as", MMToken::ExportAsKeyword)
                  .Case("extern", MMToken::ExternKeyword)
                  .Case("framework", MMToken::FrameworkKeyword)
                  .Case("header", MMToken::HeaderKeyword)
@@ -1594,6 +1597,7 @@
 ///     header-declaration
 ///     submodule-declaration
 ///     export-declaration
+///     export-as-declaration
 ///     link-declaration
 ///
 ///   submodule-declaration:
@@ -1841,6 +1845,10 @@
       parseExportDecl();
       break;
 
+    case MMToken::ExportAsKeyword:
+      parseExportAsDecl();
+      break;
+
     case MMToken::UseKeyword:
       parseUseDecl();
       break;
@@ -2301,6 +2309,41 @@
   ActiveModule->UnresolvedExports.push_back(Unresolved);
 }
 
+/// \brief Parse a module export_as declaration.
+///
+///   export-as-declaration:
+///     'export_as' identifier
+void ModuleMapParser::parseExportAsDecl() {
+  assert(Tok.is(MMToken::ExportAsKeyword));
+  consumeToken();
+
+  if (!Tok.is(MMToken::Identifier)) {
+    Diags.Report(Tok.getLocation(), diag::err_mmap_module_id);
+    HadError = true;
+    return;
+  }
+
+  if (ActiveModule->Parent) {
+    Diags.Report(Tok.getLocation(), diag::err_mmap_submodule_export_as);
+    consumeToken();
+    return;
+  }
+  
+  if (!ActiveModule->ExportAsModule.empty()) {
+    if (ActiveModule->ExportAsModule == Tok.getString()) {
+      Diags.Report(Tok.getLocation(), diag::warn_mmap_redundant_export_as)
+        << ActiveModule->Name << Tok.getString();
+    } else {
+      Diags.Report(Tok.getLocation(), diag::err_mmap_conflicting_export_as)
+        << ActiveModule->Name << ActiveModule->ExportAsModule
+        << Tok.getString();
+    }
+  }
+  
+  ActiveModule->ExportAsModule = Tok.getString();
+  consumeToken();
+}
+
 /// \brief Parse a module use declaration.
 ///
 ///   use-declaration:
@@ -2711,6 +2754,7 @@
     case MMToken::Exclaim:
     case MMToken::ExcludeKeyword:
     case MMToken::ExportKeyword:
+    case MMToken::ExportAsKeyword:
     case MMToken::HeaderKeyword:
     case MMToken::Identifier:
     case MMToken::LBrace:
diff --git a/lib/Serialization/ASTReader.cpp b/lib/Serialization/ASTReader.cpp
index 9904dc8..a1c3272 100644
--- a/lib/Serialization/ASTReader.cpp
+++ b/lib/Serialization/ASTReader.cpp
@@ -5111,7 +5111,7 @@
       break;
     }
 
-    case SUBMODULE_INITIALIZERS:
+    case SUBMODULE_INITIALIZERS: {
       if (!ContextObj)
         break;
       SmallVector<uint32_t, 16> Inits;
@@ -5120,6 +5120,11 @@
       ContextObj->addLazyModuleInitializers(CurrentModule, Inits);
       break;
     }
+
+    case SUBMODULE_EXPORT_AS:
+      CurrentModule->ExportAsModule = Blob.str();
+      break;
+    }
   }
 }
 
diff --git a/lib/Serialization/ASTWriter.cpp b/lib/Serialization/ASTWriter.cpp
index 4dc6d48..ec03a87 100644
--- a/lib/Serialization/ASTWriter.cpp
+++ b/lib/Serialization/ASTWriter.cpp
@@ -1130,6 +1130,7 @@
   RECORD(SUBMODULE_TEXTUAL_HEADER);
   RECORD(SUBMODULE_PRIVATE_TEXTUAL_HEADER);
   RECORD(SUBMODULE_INITIALIZERS);
+  RECORD(SUBMODULE_EXPORT_AS);
 
   // Comments Block.
   BLOCK(COMMENTS_BLOCK);
@@ -2790,6 +2791,11 @@
   Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob));    // Message
   unsigned ConflictAbbrev = Stream.EmitAbbrev(std::move(Abbrev));
 
+  Abbrev = std::make_shared<BitCodeAbbrev>();
+  Abbrev->Add(BitCodeAbbrevOp(SUBMODULE_EXPORT_AS));
+  Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob));    // Macro name
+  unsigned ExportAsAbbrev = Stream.EmitAbbrev(std::move(Abbrev));
+
   // Write the submodule metadata block.
   RecordData::value_type Record[] = {
       getNumberOfModules(WritingModule),
@@ -2925,6 +2931,12 @@
     if (!Inits.empty())
       Stream.EmitRecord(SUBMODULE_INITIALIZERS, Inits);
 
+    // Emit the name of the re-exported module, if any.
+    if (!Mod->ExportAsModule.empty()) {
+      RecordData::value_type Record[] = {SUBMODULE_EXPORT_AS};
+      Stream.EmitRecordWithBlob(ExportAsAbbrev, Record, Mod->ExportAsModule);
+    }
+    
     // Queue up the submodules of this module.
     for (auto *M : Mod->submodules())
       Q.push(M);
diff --git a/test/Modules/Inputs/export_as_test.modulemap b/test/Modules/Inputs/export_as_test.modulemap
new file mode 100644
index 0000000..4aaec41
--- /dev/null
+++ b/test/Modules/Inputs/export_as_test.modulemap
@@ -0,0 +1,9 @@
+module PrivateFoo {
+  export_as Foo
+  export_as Bar
+  export_as Bar
+
+  module Sub {
+    export_as Wibble
+  }
+}
diff --git a/test/Modules/export_as_test.c b/test/Modules/export_as_test.c
new file mode 100644
index 0000000..a73d6bf
--- /dev/null
+++ b/test/Modules/export_as_test.c
@@ -0,0 +1,9 @@
+// RUN: rm -rf %t
+// RUN: not %clang_cc1 -fmodules -fmodules-cache-path=%t -fmodule-map-file=%S/Inputs/export_as_test.modulemap %s 2> %t.err
+// RUN: FileCheck %s < %t.err
+
+// CHECK: export_as_test.modulemap:3:13: error: conflicting re-export of module 'PrivateFoo' as 'Foo' or 'Bar'
+// CHECK: export_as_test.modulemap:4:13: warning: module 'PrivateFoo' already re-exported as 'Bar'
+// CHECK: export_as_test.modulemap:7:15: error: only top-level modules can be re-exported as public
+
+