Implement support for module requirements, which indicate the language

features needed for a particular module to be available. This allows
mixed-language modules, where certain headers only work under some
language variants (e.g., in C++, std.tuple might only be available in
C++11 mode).

llvm-svn: 147387

1 files changed, 14 insertions, 0 deletions

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();