4 files changed, 68 insertions, 1 deletions

diff --git a/clang/lib/Basic/Module.cpp b/clang/lib/Basic/Module.cpp
index 1d96afd476e..621b1b23d70 100644
--- a/clang/lib/Basic/Module.cpp
+++ b/clang/lib/Basic/Module.cpp
@@ -440,6 +440,11 @@ void Module::print(raw_ostream &OS, unsigned Indent) const {
     }
   }
 
+  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/clang/lib/Lex/ModuleMap.cpp b/clang/lib/Lex/ModuleMap.cpp
index b01080e55a5..fc7fe138c5d 100644
--- a/clang/lib/Lex/ModuleMap.cpp
+++ b/clang/lib/Lex/ModuleMap.cpp
@@ -1201,6 +1201,7 @@ namespace clang {
       ExcludeKeyword,
       ExplicitKeyword,
       ExportKeyword,
+      ExportAsKeyword,
       ExternKeyword,
       FrameworkKeyword,
       LinkKeyword,
@@ -1312,6 +1313,7 @@ namespace clang {
                          SourceLocation LeadingLoc);
     void parseUmbrellaDirDecl(SourceLocation UmbrellaLoc);
     void parseExportDecl();
+    void parseExportAsDecl();
     void parseUseDecl();
     void parseLinkDecl();
     void parseConfigMacros();
@@ -1363,6 +1365,7 @@ retry:
                  .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)
@@ -1590,6 +1593,7 @@ namespace {
 ///     header-declaration
 ///     submodule-declaration
 ///     export-declaration
+///     export-as-declaration
 ///     link-declaration
 ///
 ///   submodule-declaration:
@@ -1824,6 +1828,10 @@ void ModuleMapParser::parseModuleDecl() {
       parseExportDecl();
       break;
 
+    case MMToken::ExportAsKeyword:
+      parseExportAsDecl();
+      break;
+
     case MMToken::UseKeyword:
       parseUseDecl();
       break;
@@ -2284,6 +2292,41 @@ void ModuleMapParser::parseExportDecl() {
   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:
@@ -2689,6 +2732,7 @@ bool ModuleMapParser::parseModuleMapFile() {
     case MMToken::Exclaim:
     case MMToken::ExcludeKeyword:
     case MMToken::ExportKeyword:
+    case MMToken::ExportAsKeyword:
     case MMToken::HeaderKeyword:
     case MMToken::Identifier:
     case MMToken::LBrace:
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 3dba2997905..46823030d30 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -5123,7 +5123,7 @@ ASTReader::ReadSubmoduleBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
       break;
     }
 
-    case SUBMODULE_INITIALIZERS:
+    case SUBMODULE_INITIALIZERS: {
       if (!ContextObj)
         break;
       SmallVector<uint32_t, 16> Inits;
@@ -5132,6 +5132,11 @@ ASTReader::ReadSubmoduleBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
       ContextObj->addLazyModuleInitializers(CurrentModule, Inits);
       break;
     }
+
+    case SUBMODULE_EXPORT_AS:
+      CurrentModule->ExportAsModule = Blob.str();
+      break;
+    }
   }
 }
 
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 8f4a908f540..063d6f46e34 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -1130,6 +1130,7 @@ void ASTWriter::WriteBlockInfoBlock() {
   RECORD(SUBMODULE_TEXTUAL_HEADER);
   RECORD(SUBMODULE_PRIVATE_TEXTUAL_HEADER);
   RECORD(SUBMODULE_INITIALIZERS);
+  RECORD(SUBMODULE_EXPORT_AS);
 
   // Comments Block.
   BLOCK(COMMENTS_BLOCK);
@@ -2791,6 +2792,12 @@ void ASTWriter::WriteSubmodules(Module *WritingModule) {
   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 +2932,12 @@ void ASTWriter::WriteSubmodules(Module *WritingModule) {
     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);