Add a function to ExternalASTSource that returns a descriptor that

abstracts the commonalities between modules and PCH files that are
needed to emit debug info for a module or precompiled header.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@241083 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/AST/ExternalASTSource.h

@@ -156,6 +156,20 @@ public:
   /// \brief Retrieve the module that corresponds to the given module ID.
   virtual Module *getModule(unsigned ID) { return nullptr; }
 
+  /// \brief Holds everything needed to generate debug info for an
+  /// imported module or precompiled header file.
+  struct ASTSourceDescriptor {
+    std::string ModuleName;
+    std::string Path;
+    std::string ASTFile;
+    uint64_t Signature;
+  };
+
+  /// \brief Return a descriptor for the corresponding module, if one exists.
+  virtual llvm::Optional<ASTSourceDescriptor> getSourceDescriptor(unsigned ID);
+  /// \brief Return a descriptor for the module.
+  virtual ASTSourceDescriptor getSourceDescriptor(const Module &M);
+
   /// \brief Finds all declarations lexically contained within the given
   /// DeclContext, after applying an optional filter predicate.
   ///

include/clang/Basic/Module.h

@@ -66,6 +66,9 @@ public:
   /// \brief The umbrella header or directory.
   llvm::PointerUnion<const DirectoryEntry *, const FileEntry *> Umbrella;
 
+  /// \brief The module signature.
+  uint64_t Signature;
+
   /// \brief The name of the umbrella entry, as written in the module map.
   std::string UmbrellaAsWritten;
   

include/clang/Serialization/ASTReader.h

@@ -1846,6 +1846,11 @@ public:
   /// Note: overrides method in ExternalASTSource
   Module *getModule(unsigned ID) override;
 
+  /// \brief Return a descriptor for the corresponding module.
+  llvm::Optional<ASTSourceDescriptor> getSourceDescriptor(unsigned ID) override;
+  /// \brief Return a descriptor for the module.
+  ASTSourceDescriptor getSourceDescriptor(const Module &M) override;
+
   /// \brief Retrieve a selector from the given module with its local ID
   /// number.
   Selector getLocalSelector(ModuleFile &M, unsigned LocalID);

lib/AST/ExternalASTSource.cpp

@@ -22,6 +22,16 @@ using namespace clang;
 
 ExternalASTSource::~ExternalASTSource() { }
 
+llvm::Optional<ExternalASTSource::ASTSourceDescriptor>
+ExternalASTSource::getSourceDescriptor(unsigned ID) {
+  return None;
+}
+
+ExternalASTSource::ASTSourceDescriptor
+ExternalASTSource::getSourceDescriptor(const Module &M) {
+  return ASTSourceDescriptor();
+}
+
 void ExternalASTSource::FindFileRegionDecls(FileID File, unsigned Offset,
                                             unsigned Length,
                                             SmallVectorImpl<Decl *> &Decls) {}

lib/Basic/Module.cpp

@@ -27,7 +27,7 @@ using namespace clang;
 Module::Module(StringRef Name, SourceLocation DefinitionLoc, Module *Parent,
                bool IsFramework, bool IsExplicit, unsigned VisibilityID)
     : Name(Name), DefinitionLoc(DefinitionLoc), Parent(Parent), Directory(),
-      Umbrella(), ASTFile(nullptr), VisibilityID(VisibilityID),
+      Umbrella(), Signature(0), ASTFile(nullptr), VisibilityID(VisibilityID),
       IsMissingRequirement(false), IsAvailable(true), IsFromModuleFile(false),
       IsFramework(IsFramework), IsExplicit(IsExplicit), IsSystem(false),
       IsExternC(false), IsInferred(false), InferSubmodules(false),

lib/Serialization/ASTReader.cpp

@@ -4269,6 +4269,7 @@ ASTReader::ReadSubmoduleBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
         CurrentModule->setASTFile(F.File);
       }
 
+      CurrentModule->Signature = F.Signature;
       CurrentModule->IsFromModuleFile = true;
       CurrentModule->IsSystem = IsSystem || CurrentModule->IsSystem;
       CurrentModule->IsExternC = IsExternC;
@@ -7366,6 +7367,37 @@ Module *ASTReader::getModule(unsigned ID) {
   return getSubmodule(ID);
 }
 
+ExternalASTSource::ASTSourceDescriptor
+ASTReader::getSourceDescriptor(const Module &M) {
+  StringRef Dir, Filename;
+  if (M.Directory)
+    Dir = M.Directory->getName();
+  if (auto *File = M.getASTFile())
+    Filename = File->getName();
+  return ASTReader::ASTSourceDescriptor{
+             M.getFullModuleName(), Dir, Filename,
+             M.Signature
+         };
+}
+
+llvm::Optional<ExternalASTSource::ASTSourceDescriptor>
+ASTReader::getSourceDescriptor(unsigned ID) {
+  if (const Module *M = getSubmodule(ID))
+    return getSourceDescriptor(*M);
+
+  // If there is only a single PCH, return it instead.
+  // Chained PCH are not suported.
+  if (ModuleMgr.size() == 1) {
+    ModuleFile &MF = ModuleMgr.getPrimaryModule();
+    return ASTReader::ASTSourceDescriptor{
+      MF.OriginalSourceFileName, MF.OriginalDir,
+      MF.FileName,
+      MF.Signature
+    };
+  }
+  return None;
+}
+
 Selector ASTReader::getLocalSelector(ModuleFile &M, unsigned LocalID) {
   return DecodeSelector(getGlobalSelectorID(M, LocalID));
 }