3 files changed, 21 insertions, 1 deletions
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index efacc35d149..675b5eb07c5 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -2224,8 +2224,12 @@ llvm::DIModule *CGDebugInfo::getParentModuleOrNull(const Decl *D) {
     // option.
     FullSourceLoc Loc(D->getLocation(), CGM.getContext().getSourceManager());
     if (Module *M = ClangModuleMap->inferModuleFromLocation(Loc)) {
+      // This is a (sub-)module.
       auto Info = ExternalASTSource::ASTSourceDescriptor(*M);
       return getOrCreateModuleRef(Info, /*SkeletonCU=*/false);
+    } else {
+      // This the precompiled header being built.
+      return getOrCreateModuleRef(PCHDescriptor, /*SkeletonCU=*/false);
     }
   }
 
diff --git a/clang/lib/CodeGen/CGDebugInfo.h b/clang/lib/CodeGen/CGDebugInfo.h
index a68dd33fa5f..55d813834e8 100644
--- a/clang/lib/CodeGen/CGDebugInfo.h
+++ b/clang/lib/CodeGen/CGDebugInfo.h
@@ -16,6 +16,7 @@
 
 #include "CGBuilder.h"
 #include "clang/AST/Expr.h"
+#include "clang/AST/ExternalASTSource.h"
 #include "clang/AST/Type.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Frontend/CodeGenOptions.h"
@@ -57,6 +58,7 @@ class CGDebugInfo {
   llvm::DIBuilder DBuilder;
   llvm::DICompileUnit *TheCU = nullptr;
   ModuleMap *ClangModuleMap = nullptr;
+  ExternalASTSource::ASTSourceDescriptor PCHDescriptor;
   SourceLocation CurLoc;
   llvm::DIType *VTablePtrType = nullptr;
   llvm::DIType *ClassTy = nullptr;
@@ -275,6 +277,8 @@ public:
 
   void finalize();
 
+  /// Module debugging: Support for building PCMs.
+  /// @{
   /// Set the main CU's DwoId field to \p Signature.
   void setDwoId(uint64_t Signature);
 
@@ -283,6 +287,14 @@ public:
   /// the module of origin of each Decl.
   void setModuleMap(ModuleMap &MMap) { ClangModuleMap = &MMap; }
 
+  /// When generating debug information for a clang module or
+  /// precompiled header, this module map will be used to determine
+  /// the module of origin of each Decl.
+  void setPCHDescriptor(ExternalASTSource::ASTSourceDescriptor PCH) {
+    PCHDescriptor = PCH;
+  }
+  /// @}
+
   /// Update the current source location. If \arg loc is invalid it is
   /// ignored.
   void setLocation(SourceLocation Loc);
diff --git a/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp b/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp
index 0e3aa61314e..406b433c95c 100644
--- a/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp
+++ b/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp
@@ -42,6 +42,7 @@ namespace {
 class PCHContainerGenerator : public ASTConsumer {
   DiagnosticsEngine &Diags;
   const std::string MainFileName;
+  const std::string OutputFileName;
   ASTContext *Ctx;
   ModuleMap &MMap;
   const HeaderSearchOptions &HeaderSearchOpts;
@@ -137,7 +138,8 @@ public:
                         const std::string &OutputFileName,
                         raw_pwrite_stream *OS,
                         std::shared_ptr<PCHBuffer> Buffer)
-      : Diags(CI.getDiagnostics()), Ctx(nullptr),
+      : Diags(CI.getDiagnostics()), MainFileName(MainFileName),
+        OutputFileName(OutputFileName), Ctx(nullptr),
         MMap(CI.getPreprocessor().getHeaderSearchInfo().getModuleMap()),
         HeaderSearchOpts(CI.getHeaderSearchOpts()),
         PreprocessorOpts(CI.getPreprocessorOpts()),
@@ -163,6 +165,8 @@ public:
     Builder.reset(new CodeGen::CodeGenModule(
         *Ctx, HeaderSearchOpts, PreprocessorOpts, CodeGenOpts, *M, Diags));
     Builder->getModuleDebugInfo()->setModuleMap(MMap);
+    Builder->getModuleDebugInfo()->setPCHDescriptor(
+        {MainFileName, "", OutputFileName, ~1ULL});
   }
 
   bool HandleTopLevelDecl(DeclGroupRef D) override {