2 files changed, 32 insertions, 0 deletions

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 440474b587a..dd48b2dc564 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -2523,6 +2523,11 @@ void ASTReader::makeModuleVisible(Module *Mod,
       continue;
     }
     
+    if (!Mod->isAvailable()) {
+      // Modules that aren't available cannot be made visible.
+      continue;
+    }
+
     // Update the module's name visibility.
     Mod->NameVisibility = NameVisibility;
     
@@ -3247,6 +3252,19 @@ ASTReader::ASTReadResult ASTReader::ReadSubmoduleBlock(ModuleFile &F) {
       CurrentModule->UnresolvedExports.clear();
       break;
     }
+    case SUBMODULE_REQUIRES: {
+      if (First) {
+        Error("missing submodule metadata record at beginning of block");
+        return Failure;
+      }
+
+      if (!CurrentModule)
+        break;
+
+      CurrentModule->addRequirement(StringRef(BlobStart, BlobLen), 
+                                    Context.getLangOptions());
+      break;
+    }
     }
   }
 
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 1302d538f5a..cfc83f7bc0a 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -1916,6 +1916,11 @@ void ASTWriter::WriteSubmodules(Module *WritingModule) {
   Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob)); // Name
   unsigned UmbrellaDirAbbrev = Stream.EmitAbbrev(Abbrev);
 
+  Abbrev = new BitCodeAbbrev();
+  Abbrev->Add(BitCodeAbbrevOp(SUBMODULE_REQUIRES));
+  Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob)); // Feature
+  unsigned RequiresAbbrev = Stream.EmitAbbrev(Abbrev);
+
   // Write the submodule metadata block.
   RecordData Record;
   Record.push_back(getNumberOfModules(WritingModule));
@@ -1947,6 +1952,15 @@ void ASTWriter::WriteSubmodules(Module *WritingModule) {
     Record.push_back(Mod->InferExportWildcard);
     Stream.EmitRecordWithBlob(DefinitionAbbrev, Record, Mod->Name);
     
+    // Emit the requirements.
+    for (unsigned I = 0, N = Mod->Requires.size(); I != N; ++I) {
+      Record.clear();
+      Record.push_back(SUBMODULE_REQUIRES);
+      Stream.EmitRecordWithBlob(RequiresAbbrev, Record,
+                                Mod->Requires[I].data(),
+                                Mod->Requires[I].size());
+    }
+
     // Emit the umbrella header, if there is one.
     if (const FileEntry *UmbrellaHeader = Mod->getUmbrellaHeader()) {
       Record.clear();