Record parseable interface imports in the debug info.

When a Swift module built with debug info imports a library without
debug info from a textual interface, the textual interface is
necessary to reconstruct types defined in the library's interface.  By
recording the Swift interface files in DWARF dsymutil can collect them
and LLDB can find them.

rdar://problem/49751363

Author: adrian-prantl

include/swift/AST/Module.h

@@ -827,6 +827,10 @@ class FileUnit : public DeclContext {
     return getParentModule()->getName().str();
   }
 
+  /// If this is a module imported from a parseable interface, return the path
+  /// to the interface file, otherwise an empty StringRef.
+  virtual StringRef getParseableInterface() const { return {}; }
+
   /// Traverse the decls within this file.
   ///
   /// \returns true if traversal was aborted, false if it completed

include/swift/Serialization/ModuleFormat.h

@@ -643,7 +643,8 @@ namespace input_block {
     IMPORTED_HEADER_CONTENTS,
     MODULE_FLAGS, // [unused]
     SEARCH_PATH,
-    FILE_DEPENDENCY
+    FILE_DEPENDENCY,
+    PARSEABLE_INTERFACE_PATH
   };
 
   using ImportedModuleLayout = BCRecordLayout<
@@ -690,6 +691,12 @@ namespace input_block {
     BCFixed<1>,                    // SDK-relative?
     BCBlob                         // path
   >;
+
+  using ParseableInterfaceLayout = BCRecordLayout<
+    PARSEABLE_INTERFACE_PATH,
+    BCBlob // file path
+  >;
+
 }
 
 /// The record types within the "decls-and-types" block.

include/swift/Serialization/SerializationOptions.h

@@ -33,6 +33,7 @@ namespace swift {
     StringRef GroupInfoPath;
     StringRef ImportedHeader;
     StringRef ModuleLinkName;
+    StringRef ParseableInterface;
     ArrayRef<std::string> ExtraClangOptions;
 
     /// Describes a single-file dependency for this module, along with the

include/swift/Serialization/SerializedModuleLoader.h

@@ -186,6 +186,11 @@ class SerializedASTFile final : public LoadedFile {
   friend class ModuleFile;
 
   ModuleFile &File;
+
+  /// The parseable interface this module was generated from if any.
+  /// Used for debug info.
+  std::string ParseableInterface;
+
   bool IsSIB;
 
   ~SerializedASTFile() = default;
@@ -277,6 +282,13 @@ class SerializedASTFile final : public LoadedFile {
 
   virtual const clang::Module *getUnderlyingClangModule() const override;
 
+  /// If this is a module imported from a parseable interface, return the path
+  /// to the interface file, otherwise an empty StringRef.
+  virtual StringRef getParseableInterface() const override {
+    return ParseableInterface;
+  }
+  void setParseableInterface(StringRef PI) { ParseableInterface = PI; }
+  
   virtual bool getAllGenericSignatures(
                    SmallVectorImpl<GenericSignature*> &genericSignatures)
                 override;

include/swift/Serialization/Validation.h

@@ -92,6 +92,7 @@ struct ValidationInfo {
 class ExtendedValidationInfo {
   SmallVector<StringRef, 4> ExtraClangImporterOpts;
   StringRef SDKPath;
+  StringRef ParseableInterface;
   struct {
     unsigned ArePrivateImportsEnabled : 1;
     unsigned IsSIB : 1;
@@ -113,6 +114,8 @@ class ExtendedValidationInfo {
   void addExtraClangImporterOption(StringRef option) {
     ExtraClangImporterOpts.push_back(option);
   }
+  StringRef getParseableInterface() const { return ParseableInterface; }
+  void setParseableInterface(StringRef PI) { ParseableInterface = PI; }
 
   bool isSIB() const { return Bits.IsSIB; }
   void setIsSIB(bool val) {

lib/AST/Module.cpp

@@ -1134,6 +1134,10 @@ StringRef ModuleDecl::getModuleFilename() const {
   // per-file names. Modules can consist of more than one file.
   StringRef Result;
   for (auto F : getFiles()) {
+    Result = F->getParseableInterface();
+    if (!Result.empty())
+      return Result;
+
     if (auto SF = dyn_cast<SourceFile>(F)) {
       if (!Result.empty())
         return StringRef();

lib/Frontend/Frontend.cpp

@@ -124,9 +124,8 @@ CompilerInvocation::getParseableInterfaceOutputPathForWholeModule() const {
       .SupplementaryOutputs.ParseableInterfaceOutputPath;
 }
 
-SerializationOptions
-CompilerInvocation::computeSerializationOptions(const SupplementaryOutputPaths &outs,
-                                                bool moduleIsPublic) {
+SerializationOptions CompilerInvocation::computeSerializationOptions(
+    const SupplementaryOutputPaths &outs, bool moduleIsPublic) {
   const FrontendOptions &opts = getFrontendOptions();
 
   SerializationOptions serializationOpts;

lib/Frontend/ParseableInterfaceModuleLoader.cpp

@@ -582,6 +582,12 @@ class swift::ParseableInterfaceBuilder {
       std::string OutPathStr = OutPath;
       SerializationOpts.OutputPath = OutPathStr.c_str();
       SerializationOpts.ModuleLinkName = FEOpts.ModuleLinkName;
+
+      // Record any non-SDK parseable interface files for the debug info.
+      StringRef SDKPath = SubInstance.getASTContext().SearchPathOpts.SDKPath;
+      if (!getRelativeDepPath(InPath, SDKPath))
+        SerializationOpts.ParseableInterface = InPath;
+
       SmallVector<FileDependency, 16> Deps;
       if (collectDepsForSerialization(SubInstance, Deps,
             FEOpts.SerializeParseableModuleInterfaceDependencyHashes)) {

lib/IRGen/IRGenDebugInfo.cpp

@@ -191,14 +191,13 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
 
 private:
   static StringRef getFilenameFromDC(const DeclContext *DC) {
-    if (auto LF = dyn_cast<LoadedFile>(DC))
+    if (auto *LF = dyn_cast<LoadedFile>(DC))
       return LF->getFilename();
-    if (auto SF = dyn_cast<SourceFile>(DC))
+    if (auto *SF = dyn_cast<SourceFile>(DC))
       return SF->getFilename();
-    else if (auto M = dyn_cast<ModuleDecl>(DC))
+    if (auto *M = dyn_cast<ModuleDecl>(DC))
       return M->getModuleFilename();
-    else
-      return StringRef();
+    return {};
   }
 
   using DebugLoc = SILLocation::DebugLoc;
@@ -717,7 +716,6 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
     ModuleDecl *M = IM.second;
     if (Optional<ASTSourceDescriptor> ModuleDesc = getClangModule(*M))
       return getOrCreateModule(*ModuleDesc, ModuleDesc->getModuleOrNull());
-
     StringRef Path = getFilenameFromDC(M);
     StringRef Name = M->getName().str();
     return getOrCreateModule(M, TheCU, Name, Path);

lib/Serialization/ModuleFile.cpp

@@ -1332,6 +1332,11 @@ ModuleFile::ModuleFile(
           SearchPaths.push_back({blobData, isFramework, isSystem});
           break;
         }
+        case input_block::PARSEABLE_INTERFACE_PATH: {
+          if (extInfo)
+            extInfo->setParseableInterface(blobData);
+          break;
+        }
         default:
           // Unknown input kind, possibly for use by a future version of the
           // module format.