3 files changed, 66 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index a139ce0e073..8daf8af4e18 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -27,6 +27,8 @@
 #include "clang/Basic/SourceManager.h"
 #include "clang/Basic/Version.h"
 #include "clang/Frontend/CodeGenOptions.h"
+#include "clang/Lex/HeaderSearchOptions.h"
+#include "clang/Lex/PreprocessorOptions.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/IR/Constants.h"
@@ -1661,6 +1663,49 @@ llvm::DIType *CGDebugInfo::CreateType(const ObjCInterfaceType *Ty,
   return CreateTypeDefinition(Ty, Unit);
 }
 
+llvm::DIModule *
+CGDebugInfo::getOrCreateModuleRef(ExternalASTSource::ASTSourceDescriptor Mod) {
+  llvm::DIModule *ModuleRef = nullptr;
+  auto it = ModuleRefCache.find(Mod.Signature);
+  if (it != ModuleRefCache.end())
+    ModuleRef = it->second;
+  else {
+    // Macro definitions that were defined with "-D" on the command line.
+    SmallString<128> ConfigMacros;
+    {
+      llvm::raw_svector_ostream OS(ConfigMacros);
+      const auto &PPOpts = CGM.getPreprocessorOpts();
+      unsigned I = 0;
+      // Translate the macro definitions back into a commmand line.
+      for (auto &M : PPOpts.Macros) {
+        if (++I > 1)
+          OS << " ";
+        const std::string &Macro = M.first;
+        bool Undef = M.second;
+        OS << "\"-" << (Undef ? 'U' : 'D');
+        for (char c : Macro)
+          switch (c) {
+          case '\\' : OS << "\\\\"; break;
+          case '"'  : OS << "\\\""; break;
+          default: OS << c;
+          }
+        OS << '\"';
+      }
+    }
+    llvm::DIBuilder DIB(CGM.getModule());
+    auto *CU = DIB.createCompileUnit(
+        TheCU->getSourceLanguage(), internString(Mod.ModuleName),
+        internString(Mod.Path), TheCU->getProducer(), true, StringRef(), 0,
+        internString(Mod.ASTFile), llvm::DIBuilder::FullDebug, Mod.Signature);
+    ModuleRef = DIB.createModule(
+        CU, Mod.ModuleName, ConfigMacros, internString(Mod.Path),
+        internString(CGM.getHeaderSearchOpts().Sysroot));
+    DIB.finalize();
+    ModuleRefCache.insert(std::make_pair(Mod.Signature, ModuleRef));
+  }
+  return ModuleRef;
+}
+
 llvm::DIType *CGDebugInfo::CreateTypeDefinition(const ObjCInterfaceType *Ty,
                                                 llvm::DIFile *Unit) {
   ObjCInterfaceDecl *ID = Ty->getDecl();
@@ -3304,6 +3349,15 @@ void CGDebugInfo::EmitUsingDecl(const UsingDecl &UD) {
         getLineNumber(USD.getLocation()));
 }
 
+void CGDebugInfo::EmitImportDecl(const ImportDecl &ID) {
+  auto *Reader = CGM.getContext().getExternalSource();
+  auto Info = Reader->getSourceDescriptor(*ID.getImportedModule());
+  DBuilder.createImportedDeclaration(
+    getCurrentContextDescriptor(cast<Decl>(ID.getDeclContext())),
+                                getOrCreateModuleRef(Info),
+                                getLineNumber(ID.getLocation()));
+}
+
 llvm::DIImportedEntity *
 CGDebugInfo::EmitNamespaceAlias(const NamespaceAliasDecl &NA) {
   if (CGM.getCodeGenOpts().getDebugInfo() < CodeGenOptions::LimitedDebugInfo)
diff --git a/clang/lib/CodeGen/CGDebugInfo.h b/clang/lib/CodeGen/CGDebugInfo.h
index 8509e0770db..10d3b0d9ab0 100644
--- a/clang/lib/CodeGen/CGDebugInfo.h
+++ b/clang/lib/CodeGen/CGDebugInfo.h
@@ -83,6 +83,9 @@ class CGDebugInfo {
   /// which may change.
   llvm::SmallVector<ObjCInterfaceCacheEntry, 32> ObjCInterfaceCache;
 
+  /// \brief Cache of references to AST files such as PCHs or modules.
+  llvm::DenseMap<uint64_t, llvm::DIModule *> ModuleRefCache;
+
   /// \brief list of interfaces we want to keep even if orphaned.
   std::vector<void *> RetainedTypes;
 
@@ -289,6 +292,9 @@ public:
   /// \brief Emit C++ using declaration.
   void EmitUsingDecl(const UsingDecl &UD);
 
+  /// \brief Emit an @import declaration.
+  void EmitImportDecl(const ImportDecl &ID);
+
   /// \brief Emit C++ namespace alias.
   llvm::DIImportedEntity *EmitNamespaceAlias(const NamespaceAliasDecl &NA);
 
@@ -344,6 +350,10 @@ private:
   /// necessary.
   llvm::DIType *getOrCreateType(QualType Ty, llvm::DIFile *Fg);
 
+  /// \brief Get a reference to a clang module.
+  llvm::DIModule *
+  getOrCreateModuleRef(ExternalASTSource::ASTSourceDescriptor Mod);
+
   /// \brief Get the type from the cache or create a new
   /// partial type if necessary.
   llvm::DIType *getOrCreateLimitedType(const RecordType *Ty, llvm::DIFile *F);
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index ea09ba8d4fb..b905bd2b36b 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -3362,6 +3362,8 @@ void CodeGenModule::EmitTopLevelDecl(Decl *D) {
           Owner->getTopLevelModule()->Name == getLangOpts().CurrentModule)
         break;
     }
+    if (CGDebugInfo *DI = getModuleDebugInfo())
+      DI->EmitImportDecl(*Import);
 
     ImportedModules.insert(Import->getImportedModule());
     break;