llvm/lib/IR/DIBuilder.cpp

//===--- DIBuilder.cpp - Debug Information Builder ------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the DIBuilder.
//
//===----------------------------------------------------------------------===//

#include "llvm/IR/DIBuilder.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Dwarf.h"

using namespace llvm;
using namespace llvm::dwarf;

static Constant *GetTagConstant(LLVMContext &VMContext, unsigned Tag) {
  assert((Tag & LLVMDebugVersionMask) == 0 &&
         "Tag too large for debug encoding!");
  return ConstantInt::get(Type::getInt32Ty(VMContext), Tag | LLVMDebugVersion);
}

DIBuilder::DIBuilder(Module &m)
    : M(m), VMContext(M.getContext()), TempEnumTypes(nullptr),
      TempRetainTypes(nullptr), TempSubprograms(nullptr), TempGVs(nullptr),
      DeclareFn(nullptr), ValueFn(nullptr) {}

/// finalize - Construct any deferred debug info descriptors.
void DIBuilder::finalize() {
  DIArray Enums = getOrCreateArray(AllEnumTypes);
  DIType(TempEnumTypes).replaceAllUsesWith(Enums);

  SmallVector<Value *, 16> RetainValues;
  // Declarations and definitions of the same type may be retained. Some
  // clients RAUW these pairs, leaving duplicates in the retained types
  // list. Use a set to remove the duplicates while we transform the
  // TrackingVHs back into Values.
  SmallPtrSet<Value *, 16> RetainSet;
  for (unsigned I = 0, E = AllRetainTypes.size(); I < E; I++)
    if (RetainSet.insert(AllRetainTypes[I]))
      RetainValues.push_back(AllRetainTypes[I]);
  DIArray RetainTypes = getOrCreateArray(RetainValues);
  DIType(TempRetainTypes).replaceAllUsesWith(RetainTypes);

  DIArray SPs = getOrCreateArray(AllSubprograms);
  DIType(TempSubprograms).replaceAllUsesWith(SPs);
  for (unsigned i = 0, e = SPs.getNumElements(); i != e; ++i) {
    DISubprogram SP(SPs.getElement(i));
    SmallVector<Value *, 4> Variables;
    if (NamedMDNode *NMD = getFnSpecificMDNode(M, SP)) {
      for (unsigned ii = 0, ee = NMD->getNumOperands(); ii != ee; ++ii)
        Variables.push_back(NMD->getOperand(ii));
      NMD->eraseFromParent();
    }
    if (MDNode *Temp = SP.getVariablesNodes()) {
      DIArray AV = getOrCreateArray(Variables);
      DIType(Temp).replaceAllUsesWith(AV);
    }
  }

  DIArray GVs = getOrCreateArray(AllGVs);
  DIType(TempGVs).replaceAllUsesWith(GVs);

  SmallVector<Value *, 16> RetainValuesI;
  for (unsigned I = 0, E = AllImportedModules.size(); I < E; I++)
    RetainValuesI.push_back(AllImportedModules[I]);
  DIArray IMs = getOrCreateArray(RetainValuesI);
  DIType(TempImportedModules).replaceAllUsesWith(IMs);
}

/// getNonCompileUnitScope - If N is compile unit return NULL otherwise return
/// N.
static MDNode *getNonCompileUnitScope(MDNode *N) {
  if (DIDescriptor(N).isCompileUnit())
    return nullptr;
  return N;
}

static MDNode *createFilePathPair(LLVMContext &VMContext, StringRef Filename,
                                  StringRef Directory) {
  assert(!Filename.empty() && "Unable to create file without name");
  Value *Pair[] = {
    MDString::get(VMContext, Filename),
    MDString::get(VMContext, Directory)
  };
  return MDNode::get(VMContext, Pair);
}

/// createCompileUnit - A CompileUnit provides an anchor for all debugging
/// information generated during this instance of compilation.
DICompileUnit DIBuilder::createCompileUnit(unsigned Lang, StringRef Filename,
                                           StringRef Directory,
                                           StringRef Producer, bool isOptimized,
                                           StringRef Flags, unsigned RunTimeVer,
                                           StringRef SplitName,
                                           DebugEmissionKind Kind,
                                           bool EmitDebugInfo) {

  assert(((Lang <= dwarf::DW_LANG_OCaml && Lang >= dwarf::DW_LANG_C89) ||
          (Lang <= dwarf::DW_LANG_hi_user && Lang >= dwarf::DW_LANG_lo_user)) &&
         "Invalid Language tag");
  assert(!Filename.empty() &&
         "Unable to create compile unit without filename");
  Value *TElts[] = { GetTagConstant(VMContext, DW_TAG_base_type) };
  TempEnumTypes = MDNode::getTemporary(VMContext, TElts);

  TempRetainTypes = MDNode::getTemporary(VMContext, TElts);

  TempSubprograms = MDNode::getTemporary(VMContext, TElts);

  TempGVs = MDNode::getTemporary(VMContext, TElts);

  TempImportedModules = MDNode::getTemporary(VMContext, TElts);

  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_compile_unit),
    createFilePathPair(VMContext, Filename, Directory),
    ConstantInt::get(Type::getInt32Ty(VMContext), Lang),
    MDString::get(VMContext, Producer),
    ConstantInt::get(Type::getInt1Ty(VMContext), isOptimized),
    MDString::get(VMContext, Flags),
    ConstantInt::get(Type::getInt32Ty(VMContext), RunTimeVer),
    TempEnumTypes,
    TempRetainTypes,
    TempSubprograms,
    TempGVs,
    TempImportedModules,
    MDString::get(VMContext, SplitName),
    ConstantInt::get(Type::getInt32Ty(VMContext), Kind)
  };

  MDNode *CUNode = MDNode::get(VMContext, Elts);

  // Create a named metadata so that it is easier to find cu in a module.
  // Note that we only generate this when the caller wants to actually
  // emit debug information. When we are only interested in tracking
  // source line locations throughout the backend, we prevent codegen from
  // emitting debug info in the final output by not generating llvm.dbg.cu.
  if (EmitDebugInfo) {
    NamedMDNode *NMD = M.getOrInsertNamedMetadata("llvm.dbg.cu");
    NMD->addOperand(CUNode);
  }

  return DICompileUnit(CUNode);
}

static DIImportedEntity
createImportedModule(LLVMContext &C, dwarf::Tag Tag, DIScope Context,
                     Value *NS, unsigned Line, StringRef Name,
                     SmallVectorImpl<TrackingVH<MDNode>> &AllImportedModules) {
  const MDNode *R;
  if (Name.empty()) {
    Value *Elts[] = {
      GetTagConstant(C, Tag),
      Context,
      NS,
      ConstantInt::get(Type::getInt32Ty(C), Line),
    };
    R = MDNode::get(C, Elts);
  } else {
    Value *Elts[] = {
      GetTagConstant(C, Tag),
      Context,
      NS,
      ConstantInt::get(Type::getInt32Ty(C), Line),
      MDString::get(C, Name)
    };
    R = MDNode::get(C, Elts);
  }
  DIImportedEntity M(R);
  assert(M.Verify() && "Imported module should be valid");
  AllImportedModules.push_back(TrackingVH<MDNode>(M));
  return M;
}

DIImportedEntity DIBuilder::createImportedModule(DIScope Context,
                                                 DINameSpace NS,
                                                 unsigned Line) {
  return ::createImportedModule(VMContext, dwarf::DW_TAG_imported_module,
                                Context, NS, Line, StringRef(), AllImportedModules);
}

DIImportedEntity DIBuilder::createImportedModule(DIScope Context,
                                                 DIImportedEntity NS,
                                                 unsigned Line) {
  return ::createImportedModule(VMContext, dwarf::DW_TAG_imported_module,
                                Context, NS, Line, StringRef(), AllImportedModules);
}

DIImportedEntity DIBuilder::createImportedDeclaration(DIScope Context,
                                                      DIScope Decl,
                                                      unsigned Line, StringRef Name) {
  return ::createImportedModule(VMContext, dwarf::DW_TAG_imported_declaration,
                                Context, Decl.getRef(), Line, Name,
                                AllImportedModules);
}

DIImportedEntity DIBuilder::createImportedDeclaration(DIScope Context,
                                                      DIImportedEntity Imp,
                                                      unsigned Line, StringRef Name) {
  return ::createImportedModule(VMContext, dwarf::DW_TAG_imported_declaration,
                                Context, Imp, Line, Name, AllImportedModules);
}

/// createFile - Create a file descriptor to hold debugging information
/// for a file.
DIFile DIBuilder::createFile(StringRef Filename, StringRef Directory) {
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_file_type),
    createFilePathPair(VMContext, Filename, Directory)
  };
  return DIFile(MDNode::get(VMContext, Elts));
}

/// createEnumerator - Create a single enumerator value.
DIEnumerator DIBuilder::createEnumerator(StringRef Name, int64_t Val) {
  assert(!Name.empty() && "Unable to create enumerator without name");
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_enumerator),
    MDString::get(VMContext, Name),
    ConstantInt::get(Type::getInt64Ty(VMContext), Val)
  };
  return DIEnumerator(MDNode::get(VMContext, Elts));
}

/// \brief Create a DWARF unspecified type.
DIBasicType DIBuilder::createUnspecifiedType(StringRef Name) {
  assert(!Name.empty() && "Unable to create type without name");
  // Unspecified types are encoded in DIBasicType format. Line number, filename,
  // size, alignment, offset and flags are always empty here.
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_unspecified_type),
    nullptr, // Filename
    nullptr, // Unused
    MDString::get(VMContext, Name),
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Line
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Size
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Align
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Offset
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Flags;
    ConstantInt::get(Type::getInt32Ty(VMContext), 0)  // Encoding
  };
  return DIBasicType(MDNode::get(VMContext, Elts));
}

/// \brief Create C++11 nullptr type.
DIBasicType DIBuilder::createNullPtrType() {
  return createUnspecifiedType("decltype(nullptr)");
}

/// createBasicType - Create debugging information entry for a basic
/// type, e.g 'char'.
DIBasicType
DIBuilder::createBasicType(StringRef Name, uint64_t SizeInBits,
                           uint64_t AlignInBits, unsigned Encoding) {
  assert(!Name.empty() && "Unable to create type without name");
  // Basic types are encoded in DIBasicType format. Line number, filename,
  // offset and flags are always empty here.
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_base_type),
    nullptr, // File/directory name
    nullptr, // Unused
    MDString::get(VMContext, Name),
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Line
    ConstantInt::get(Type::getInt64Ty(VMContext), SizeInBits),
    ConstantInt::get(Type::getInt64Ty(VMContext), AlignInBits),
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Offset
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Flags;
    ConstantInt::get(Type::getInt32Ty(VMContext), Encoding)
  };
  return DIBasicType(MDNode::get(VMContext, Elts));
}

/// createQualifiedType - Create debugging information entry for a qualified
/// type, e.g. 'const int'.
DIDerivedType DIBuilder::createQualifiedType(unsigned Tag, DIType FromTy) {
  // Qualified types are encoded in DIDerivedType format.
  Value *Elts[] = {
    GetTagConstant(VMContext, Tag),
    nullptr, // Filename
    nullptr, // Unused
    MDString::get(VMContext, StringRef()), // Empty name.
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Line
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Size
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Align
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Offset
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Flags
    FromTy.getRef()
  };
  return DIDerivedType(MDNode::get(VMContext, Elts));
}

/// createPointerType - Create debugging information entry for a pointer.
DIDerivedType
DIBuilder::createPointerType(DIType PointeeTy, uint64_t SizeInBits,
                             uint64_t AlignInBits, StringRef Name) {
  // Pointer types are encoded in DIDerivedType format.
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_pointer_type),
    nullptr, // Filename
    nullptr, // Unused
    MDString::get(VMContext, Name),
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Line
    ConstantInt::get(Type::getInt64Ty(VMContext), SizeInBits),
    ConstantInt::get(Type::getInt64Ty(VMContext), AlignInBits),
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Offset
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Flags
    PointeeTy.getRef()
  };
  return DIDerivedType(MDNode::get(VMContext, Elts));
}

DIDerivedType DIBuilder::createMemberPointerType(DIType PointeeTy,
                                                 DIType Base) {
  // Pointer types are encoded in DIDerivedType format.
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_ptr_to_member_type),
    nullptr, // Filename
    nullptr, // Unused
    nullptr,
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Line
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Size
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Align
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Offset
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Flags
    PointeeTy.getRef(),
    Base.getRef()
  };
  return DIDerivedType(MDNode::get(VMContext, Elts));
}

/// createReferenceType - Create debugging information entry for a reference
/// type.
DIDerivedType DIBuilder::createReferenceType(unsigned Tag, DIType RTy) {
  assert(RTy.isType() && "Unable to create reference type");
  // References are encoded in DIDerivedType format.
  Value *Elts[] = {
    GetTagConstant(VMContext, Tag),
    nullptr, // Filename
    nullptr, // TheCU,
    nullptr, // Name
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Line
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Size
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Align
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Offset
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Flags
    RTy.getRef()
  };
  return DIDerivedType(MDNode::get(VMContext, Elts));
}

/// createTypedef - Create debugging information entry for a typedef.
DIDerivedType DIBuilder::createTypedef(DIType Ty, StringRef Name, DIFile File,
                                       unsigned LineNo, DIDescriptor Context) {
  // typedefs are encoded in DIDerivedType format.
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_typedef),
    File.getFileNode(),
    DIScope(getNonCompileUnitScope(Context)).getRef(),
    MDString::get(VMContext, Name),
    ConstantInt::get(Type::getInt32Ty(VMContext), LineNo),
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Size
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Align
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Offset
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Flags
    Ty.getRef()
  };
  return DIDerivedType(MDNode::get(VMContext, Elts));
}

/// createFriend - Create debugging information entry for a 'friend'.
DIDerivedType DIBuilder::createFriend(DIType Ty, DIType FriendTy) {
  // typedefs are encoded in DIDerivedType format.
  assert(Ty.isType() && "Invalid type!");
  assert(FriendTy.isType() && "Invalid friend type!");
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_friend),
    nullptr,
    Ty.getRef(),
    nullptr, // Name
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Line
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Size
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Align
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Offset
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Flags
    FriendTy.getRef()
  };
  return DIDerivedType(MDNode::get(VMContext, Elts));
}

/// createInheritance - Create debugging information entry to establish
/// inheritance relationship between two types.
DIDerivedType DIBuilder::createInheritance(DIType Ty, DIType BaseTy,
                                           uint64_t BaseOffset,
                                           unsigned Flags) {
  assert(Ty.isType() && "Unable to create inheritance");
  // TAG_inheritance is encoded in DIDerivedType format.
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_inheritance),
    nullptr,
    Ty.getRef(),
    nullptr, // Name
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Line
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Size
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Align
    ConstantInt::get(Type::getInt64Ty(VMContext), BaseOffset),
    ConstantInt::get(Type::getInt32Ty(VMContext), Flags),
    BaseTy.getRef()
  };
  return DIDerivedType(MDNode::get(VMContext, Elts));
}

/// createMemberType - Create debugging information entry for a member.
DIDerivedType DIBuilder::createMemberType(DIDescriptor Scope, StringRef Name,
                                          DIFile File, unsigned LineNumber,
                                          uint64_t SizeInBits,
                                          uint64_t AlignInBits,
                                          uint64_t OffsetInBits, unsigned Flags,
                                          DIType Ty) {
  // TAG_member is encoded in DIDerivedType format.
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_member),
    File.getFileNode(),
    DIScope(getNonCompileUnitScope(Scope)).getRef(),
    MDString::get(VMContext, Name),
    ConstantInt::get(Type::getInt32Ty(VMContext), LineNumber),
    ConstantInt::get(Type::getInt64Ty(VMContext), SizeInBits),
    ConstantInt::get(Type::getInt64Ty(VMContext), AlignInBits),
    ConstantInt::get(Type::getInt64Ty(VMContext), OffsetInBits),
    ConstantInt::get(Type::getInt32Ty(VMContext), Flags),
    Ty.getRef()
  };
  return DIDerivedType(MDNode::get(VMContext, Elts));
}

/// createStaticMemberType - Create debugging information entry for a
/// C++ static data member.
DIDerivedType
DIBuilder::createStaticMemberType(DIDescriptor Scope, StringRef Name,
                                  DIFile File, unsigned LineNumber,
                                  DIType Ty, unsigned Flags,
                                  llvm::Value *Val) {
  // TAG_member is encoded in DIDerivedType format.
  Flags |= DIDescriptor::FlagStaticMember;
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_member),
    File.getFileNode(),
    DIScope(getNonCompileUnitScope(Scope)).getRef(),
    MDString::get(VMContext, Name),
    ConstantInt::get(Type::getInt32Ty(VMContext), LineNumber),
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Size
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Align
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Offset
    ConstantInt::get(Type::getInt32Ty(VMContext), Flags),
    Ty.getRef(),
    Val
  };
  return DIDerivedType(MDNode::get(VMContext, Elts));
}

/// createObjCIVar - Create debugging information entry for Objective-C
/// instance variable.
DIDerivedType DIBuilder::createObjCIVar(StringRef Name, DIFile File,
                                        unsigned LineNumber,
                                        uint64_t SizeInBits,
                                        uint64_t AlignInBits,
                                        uint64_t OffsetInBits, unsigned Flags,
                                        DIType Ty, MDNode *PropertyNode) {
  // TAG_member is encoded in DIDerivedType format.
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_member),
    File.getFileNode(),
    getNonCompileUnitScope(File),
    MDString::get(VMContext, Name),
    ConstantInt::get(Type::getInt32Ty(VMContext), LineNumber),
    ConstantInt::get(Type::getInt64Ty(VMContext), SizeInBits),
    ConstantInt::get(Type::getInt64Ty(VMContext), AlignInBits),
    ConstantInt::get(Type::getInt64Ty(VMContext), OffsetInBits),
    ConstantInt::get(Type::getInt32Ty(VMContext), Flags),
    Ty,
    PropertyNode
  };
  return DIDerivedType(MDNode::get(VMContext, Elts));
}

/// createObjCProperty - Create debugging information entry for Objective-C
/// property.
DIObjCProperty
DIBuilder::createObjCProperty(StringRef Name, DIFile File, unsigned LineNumber,
                              StringRef GetterName, StringRef SetterName,
                              unsigned PropertyAttributes, DIType Ty) {
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_APPLE_property),
    MDString::get(VMContext, Name),
    File,
    ConstantInt::get(Type::getInt32Ty(VMContext), LineNumber),
    MDString::get(VMContext, GetterName),
    MDString::get(VMContext, SetterName),
    ConstantInt::get(Type::getInt32Ty(VMContext), PropertyAttributes),
    Ty
  };
  return DIObjCProperty(MDNode::get(VMContext, Elts));
}

/// createTemplateTypeParameter - Create debugging information for template
/// type parameter.
DITemplateTypeParameter
DIBuilder::createTemplateTypeParameter(DIDescriptor Context, StringRef Name,
                                       DIType Ty, MDNode *File, unsigned LineNo,
                                       unsigned ColumnNo) {
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_template_type_parameter),
    DIScope(getNonCompileUnitScope(Context)).getRef(),
    MDString::get(VMContext, Name),
    Ty.getRef(),
    File,
    ConstantInt::get(Type::getInt32Ty(VMContext), LineNo),
    ConstantInt::get(Type::getInt32Ty(VMContext), ColumnNo)
  };
  return DITemplateTypeParameter(MDNode::get(VMContext, Elts));
}

DITemplateValueParameter
DIBuilder::createTemplateValueParameter(unsigned Tag, DIDescriptor Context,
                                        StringRef Name, DIType Ty,
                                        Value *Val, MDNode *File,
                                        unsigned LineNo,
                                        unsigned ColumnNo) {
  Value *Elts[] = {
    GetTagConstant(VMContext, Tag),
    DIScope(getNonCompileUnitScope(Context)).getRef(),
    MDString::get(VMContext, Name),
    Ty.getRef(),
    Val,
    File,
    ConstantInt::get(Type::getInt32Ty(VMContext), LineNo),
    ConstantInt::get(Type::getInt32Ty(VMContext), ColumnNo)
  };
  return DITemplateValueParameter(MDNode::get(VMContext, Elts));
}

/// createTemplateValueParameter - Create debugging information for template
/// value parameter.
DITemplateValueParameter
DIBuilder::createTemplateValueParameter(DIDescriptor Context, StringRef Name,
                                        DIType Ty, Value *Val,
                                        MDNode *File, unsigned LineNo,
                                        unsigned ColumnNo) {
  return createTemplateValueParameter(dwarf::DW_TAG_template_value_parameter,
                                      Context, Name, Ty, Val, File, LineNo,
                                      ColumnNo);
}

DITemplateValueParameter
DIBuilder::createTemplateTemplateParameter(DIDescriptor Context, StringRef Name,
                                           DIType Ty, StringRef Val,
                                           MDNode *File, unsigned LineNo,
                                           unsigned ColumnNo) {
  return createTemplateValueParameter(
      dwarf::DW_TAG_GNU_template_template_param, Context, Name, Ty,
      MDString::get(VMContext, Val), File, LineNo, ColumnNo);
}

DITemplateValueParameter
DIBuilder::createTemplateParameterPack(DIDescriptor Context, StringRef Name,
                                       DIType Ty, DIArray Val,
                                       MDNode *File, unsigned LineNo,
                                       unsigned ColumnNo) {
  return createTemplateValueParameter(dwarf::DW_TAG_GNU_template_parameter_pack,
                                      Context, Name, Ty, Val, File, LineNo,
                                      ColumnNo);
}

/// createClassType - Create debugging information entry for a class.
DICompositeType DIBuilder::createClassType(DIDescriptor Context, StringRef Name,
                                           DIFile File, unsigned LineNumber,
                                           uint64_t SizeInBits,
                                           uint64_t AlignInBits,
                                           uint64_t OffsetInBits,
                                           unsigned Flags, DIType DerivedFrom,
                                           DIArray Elements,
                                           DIType VTableHolder,
                                           MDNode *TemplateParams,
                                           StringRef UniqueIdentifier) {
  assert((!Context || Context.isScope() || Context.isType()) &&
         "createClassType should be called with a valid Context");
  // TAG_class_type is encoded in DICompositeType format.
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_class_type),
    File.getFileNode(),
    DIScope(getNonCompileUnitScope(Context)).getRef(),
    MDString::get(VMContext, Name),
    ConstantInt::get(Type::getInt32Ty(VMContext), LineNumber),
    ConstantInt::get(Type::getInt64Ty(VMContext), SizeInBits),
    ConstantInt::get(Type::getInt64Ty(VMContext), AlignInBits),
    ConstantInt::get(Type::getInt32Ty(VMContext), OffsetInBits),
    ConstantInt::get(Type::getInt32Ty(VMContext), Flags),
    DerivedFrom.getRef(),
    Elements,
    ConstantInt::get(Type::getInt32Ty(VMContext), 0),
    VTableHolder.getRef(),
    TemplateParams,
    UniqueIdentifier.empty() ? nullptr
                             : MDString::get(VMContext, UniqueIdentifier)
  };
  DICompositeType R(MDNode::get(VMContext, Elts));
  assert(R.isCompositeType() &&
         "createClassType should return a DICompositeType");
  if (!UniqueIdentifier.empty())
    retainType(R);
  return R;
}

/// createStructType - Create debugging information entry for a struct.
DICompositeType DIBuilder::createStructType(DIDescriptor Context,
                                            StringRef Name, DIFile File,
                                            unsigned LineNumber,
                                            uint64_t SizeInBits,
                                            uint64_t AlignInBits,
                                            unsigned Flags, DIType DerivedFrom,
                                            DIArray Elements,
                                            unsigned RunTimeLang,
                                            DIType VTableHolder,
                                            StringRef UniqueIdentifier) {
 // TAG_structure_type is encoded in DICompositeType format.
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_structure_type),
    File.getFileNode(),
    DIScope(getNonCompileUnitScope(Context)).getRef(),
    MDString::get(VMContext, Name),
    ConstantInt::get(Type::getInt32Ty(VMContext), LineNumber),
    ConstantInt::get(Type::getInt64Ty(VMContext), SizeInBits),
    ConstantInt::get(Type::getInt64Ty(VMContext), AlignInBits),
    ConstantInt::get(Type::getInt32Ty(VMContext), 0),
    ConstantInt::get(Type::getInt32Ty(VMContext), Flags),
    DerivedFrom.getRef(),
    Elements,
    ConstantInt::get(Type::getInt32Ty(VMContext), RunTimeLang),
    VTableHolder.getRef(),
    nullptr,
    UniqueIdentifier.empty() ? nullptr
                             : MDString::get(VMContext, UniqueIdentifier)
  };
  DICompositeType R(MDNode::get(VMContext, Elts));
  assert(R.isCompositeType() &&
         "createStructType should return a DICompositeType");
  if (!UniqueIdentifier.empty())
    retainType(R);
  return R;
}

/// createUnionType - Create debugging information entry for an union.
DICompositeType DIBuilder::createUnionType(DIDescriptor Scope, StringRef Name,
                                           DIFile File, unsigned LineNumber,
                                           uint64_t SizeInBits,
                                           uint64_t AlignInBits, unsigned Flags,
                                           DIArray Elements,
                                           unsigned RunTimeLang,
                                           StringRef UniqueIdentifier) {
  // TAG_union_type is encoded in DICompositeType format.
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_union_type),
    File.getFileNode(),
    DIScope(getNonCompileUnitScope(Scope)).getRef(),
    MDString::get(VMContext, Name),
    ConstantInt::get(Type::getInt32Ty(VMContext), LineNumber),
    ConstantInt::get(Type::getInt64Ty(VMContext), SizeInBits),
    ConstantInt::get(Type::getInt64Ty(VMContext), AlignInBits),
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Offset
    ConstantInt::get(Type::getInt32Ty(VMContext), Flags),
    nullptr,
    Elements,
    ConstantInt::get(Type::getInt32Ty(VMContext), RunTimeLang),
    nullptr,
    nullptr,
    UniqueIdentifier.empty() ? nullptr
                             : MDString::get(VMContext, UniqueIdentifier)
  };
  DICompositeType R(MDNode::get(VMContext, Elts));
  if (!UniqueIdentifier.empty())
    retainType(R);
  return R;
}

/// createSubroutineType - Create subroutine type.
DISubroutineType DIBuilder::createSubroutineType(DIFile File,
                                                 DITypeArray ParameterTypes,
                                                 unsigned Flags) {
  // TAG_subroutine_type is encoded in DICompositeType format.
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_subroutine_type),
    Constant::getNullValue(Type::getInt32Ty(VMContext)),
    nullptr,
    MDString::get(VMContext, ""),
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Line
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Size
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Align
    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Offset
    ConstantInt::get(Type::getInt32Ty(VMContext), Flags), // Flags
    nullptr,
    ParameterTypes,
    ConstantInt::get(Type::getInt32Ty(VMContext), 0),
    nullptr,
    nullptr,
    nullptr  // Type Identifer
  };
  return DISubroutineType(MDNode::get(VMContext, Elts));
}

/// createEnumerationType - Create debugging information entry for an
/// enumeration.
DICompositeType DIBuilder::createEnumerationType(
    DIDescriptor Scope, StringRef Name, DIFile File, unsigned LineNumber,
    uint64_t SizeInBits, uint64_t AlignInBits, DIArray Elements,
    DIType UnderlyingType, StringRef UniqueIdentifier) {
  // TAG_enumeration_type is encoded in DICompositeType format.
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_enumeration_type),
    File.getFileNode(),
    DIScope(getNonCompileUnitScope(Scope)).getRef(),
    MDString::get(VMContext, Name),
    ConstantInt::get(Type::getInt32Ty(VMContext), LineNumber),
    ConstantInt::get(Type::getInt64Ty(VMContext), SizeInBits),
    ConstantInt::get(Type::getInt64Ty(VMContext), AlignInBits),
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Offset
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Flags
    UnderlyingType.getRef(),
    Elements,
    ConstantInt::get(Type::getInt32Ty(VMContext), 0),
    nullptr,
    nullptr,
    UniqueIdentifier.empty() ? nullptr
                             : MDString::get(VMContext, UniqueIdentifier)
  };
  DICompositeType CTy(MDNode::get(VMContext, Elts));
  AllEnumTypes.push_back(CTy);
  if (!UniqueIdentifier.empty())
    retainType(CTy);
  return CTy;
}

/// createArrayType - Create debugging information entry for an array.
DICompositeType DIBuilder::createArrayType(uint64_t Size, uint64_t AlignInBits,
                                           DIType Ty, DIArray Subscripts) {
  // TAG_array_type is encoded in DICompositeType format.
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_array_type),
    nullptr, // Filename/Directory,
    nullptr, // Unused
    MDString::get(VMContext, ""),
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Line
    ConstantInt::get(Type::getInt64Ty(VMContext), Size),
    ConstantInt::get(Type::getInt64Ty(VMContext), AlignInBits),
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Offset
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Flags
    Ty.getRef(),
    Subscripts,
    ConstantInt::get(Type::getInt32Ty(VMContext), 0),
    nullptr,
    nullptr,
    nullptr  // Type Identifer
  };
  return DICompositeType(MDNode::get(VMContext, Elts));
}

/// createVectorType - Create debugging information entry for a vector.
DICompositeType DIBuilder::createVectorType(uint64_t Size, uint64_t AlignInBits,
                                            DIType Ty, DIArray Subscripts) {
  // A vector is an array type with the FlagVector flag applied.
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_array_type),
    nullptr, // Filename/Directory,
    nullptr, // Unused
    MDString::get(VMContext, ""),
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Line
    ConstantInt::get(Type::getInt64Ty(VMContext), Size),
    ConstantInt::get(Type::getInt64Ty(VMContext), AlignInBits),
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Offset
    ConstantInt::get(Type::getInt32Ty(VMContext), DIType::FlagVector),
    Ty.getRef(),
    Subscripts,
    ConstantInt::get(Type::getInt32Ty(VMContext), 0),
    nullptr,
    nullptr,
    nullptr  // Type Identifer
  };
  return DICompositeType(MDNode::get(VMContext, Elts));
}

/// createArtificialType - Create a new DIType with "artificial" flag set.
DIType DIBuilder::createArtificialType(DIType Ty) {
  if (Ty.isArtificial())
    return Ty;

  SmallVector<Value *, 9> Elts;
  MDNode *N = Ty;
  assert (N && "Unexpected input DIType!");
  for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i)
    Elts.push_back(N->getOperand(i));

  unsigned CurFlags = Ty.getFlags();
  CurFlags = CurFlags | DIType::FlagArtificial;

  // Flags are stored at this slot.
  // FIXME: Add an enum for this magic value.
  Elts[8] =  ConstantInt::get(Type::getInt32Ty(VMContext), CurFlags);

  return DIType(MDNode::get(VMContext, Elts));
}

/// createObjectPointerType - Create a new type with both the object pointer
/// and artificial flags set.
DIType DIBuilder::createObjectPointerType(DIType Ty) {
  if (Ty.isObjectPointer())
    return Ty;

  SmallVector<Value *, 9> Elts;
  MDNode *N = Ty;
  assert (N && "Unexpected input DIType!");
  for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i)
    Elts.push_back(N->getOperand(i));

  unsigned CurFlags = Ty.getFlags();
  CurFlags = CurFlags | (DIType::FlagObjectPointer | DIType::FlagArtificial);

  // Flags are stored at this slot.
  // FIXME: Add an enum for this magic value.
  Elts[8] = ConstantInt::get(Type::getInt32Ty(VMContext), CurFlags);

  return DIType(MDNode::get(VMContext, Elts));
}

/// retainType - Retain DIType in a module even if it is not referenced
/// through debug info anchors.
void DIBuilder::retainType(DIType T) {
  AllRetainTypes.push_back(TrackingVH<MDNode>(T));
}

/// createUnspecifiedParameter - Create unspeicified type descriptor
/// for the subroutine type.
DIBasicType DIBuilder::createUnspecifiedParameter() {
  return DIBasicType();
}

/// createForwardDecl - Create a permanent forward-declared type.
DICompositeType
DIBuilder::createForwardDecl(unsigned Tag, StringRef Name, DIDescriptor Scope,
                             DIFile F, unsigned Line, unsigned RuntimeLang,
                             uint64_t SizeInBits, uint64_t AlignInBits,
                             StringRef UniqueIdentifier) {
  // Create a temporary MDNode.
  Value *Elts[] = {
    GetTagConstant(VMContext, Tag),
    F.getFileNode(),
    DIScope(getNonCompileUnitScope(Scope)).getRef(),
    MDString::get(VMContext, Name),
    ConstantInt::get(Type::getInt32Ty(VMContext), Line),
    ConstantInt::get(Type::getInt64Ty(VMContext), SizeInBits),
    ConstantInt::get(Type::getInt64Ty(VMContext), AlignInBits),
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Offset
    ConstantInt::get(Type::getInt32Ty(VMContext), DIDescriptor::FlagFwdDecl),
    nullptr,
    DIArray(),
    ConstantInt::get(Type::getInt32Ty(VMContext), RuntimeLang),
    nullptr,
    nullptr, //TemplateParams
    UniqueIdentifier.empty() ? nullptr
                             : MDString::get(VMContext, UniqueIdentifier)
  };
  MDNode *Node = MDNode::get(VMContext, Elts);
  DICompositeType RetTy(Node);
  assert(RetTy.isCompositeType() &&
         "createForwardDecl result should be a DIType");
  if (!UniqueIdentifier.empty())
    retainType(RetTy);
  return RetTy;
}

/// createReplaceableForwardDecl - Create a temporary forward-declared type that
/// can be RAUW'd if the full type is seen.
DICompositeType DIBuilder::createReplaceableForwardDecl(
    unsigned Tag, StringRef Name, DIDescriptor Scope, DIFile F, unsigned Line,
    unsigned RuntimeLang, uint64_t SizeInBits, uint64_t AlignInBits,
    StringRef UniqueIdentifier) {
  // Create a temporary MDNode.
  Value *Elts[] = {
    GetTagConstant(VMContext, Tag),
    F.getFileNode(),
    DIScope(getNonCompileUnitScope(Scope)).getRef(),
    MDString::get(VMContext, Name),
    ConstantInt::get(Type::getInt32Ty(VMContext), Line),
    ConstantInt::get(Type::getInt64Ty(VMContext), SizeInBits),
    ConstantInt::get(Type::getInt64Ty(VMContext), AlignInBits),
    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Offset
    ConstantInt::get(Type::getInt32Ty(VMContext), DIDescriptor::FlagFwdDecl),
    nullptr,
    DIArray(),
    ConstantInt::get(Type::getInt32Ty(VMContext), RuntimeLang),
    nullptr,
    nullptr, //TemplateParams
    UniqueIdentifier.empty() ? nullptr
                             : MDString::get(VMContext, UniqueIdentifier)
  };
  MDNode *Node = MDNode::getTemporary(VMContext, Elts);
  DICompositeType RetTy(Node);
  assert(RetTy.isCompositeType() &&
         "createReplaceableForwardDecl result should be a DIType");
  if (!UniqueIdentifier.empty())
    retainType(RetTy);
  return RetTy;
}

/// getOrCreateArray - Get a DIArray, create one if required.
DIArray DIBuilder::getOrCreateArray(ArrayRef<Value *> Elements) {
  return DIArray(MDNode::get(VMContext, Elements));
}

/// getOrCreateTypeArray - Get a DITypeArray, create one if required.
DITypeArray DIBuilder::getOrCreateTypeArray(ArrayRef<Value *> Elements) {
  SmallVector<llvm::Value *, 16> Elts; 
  for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
    if (Elements[i] && isa<MDNode>(Elements[i]))
      Elts.push_back(DIType(cast<MDNode>(Elements[i])).getRef());
    else
      Elts.push_back(Elements[i]);
  }
  return DITypeArray(MDNode::get(VMContext, Elts));
}

/// getOrCreateSubrange - Create a descriptor for a value range.  This
/// implicitly uniques the values returned.
DISubrange DIBuilder::getOrCreateSubrange(int64_t Lo, int64_t Count) {
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_subrange_type),
    ConstantInt::get(Type::getInt64Ty(VMContext), Lo),
    ConstantInt::get(Type::getInt64Ty(VMContext), Count)
  };

  return DISubrange(MDNode::get(VMContext, Elts));
}

static DIGlobalVariable
createGlobalVariableHelper(LLVMContext &VMContext, DIDescriptor Context,
                           StringRef Name, StringRef LinkageName, DIFile F,
                           unsigned LineNumber, DITypeRef Ty, bool isLocalToUnit,
                           Value *Val, MDNode *Decl, bool isDefinition,
                           std::function<MDNode *(ArrayRef<Value *>)> CreateFunc) {
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_variable),
    Constant::getNullValue(Type::getInt32Ty(VMContext)),
    getNonCompileUnitScope(Context),
    MDString::get(VMContext, Name),
    MDString::get(VMContext, Name),
    MDString::get(VMContext, LinkageName),
    F,
    ConstantInt::get(Type::getInt32Ty(VMContext), LineNumber),
    Ty,
    ConstantInt::get(Type::getInt32Ty(VMContext), isLocalToUnit),
    ConstantInt::get(Type::getInt32Ty(VMContext), isDefinition),
    Val,
    DIDescriptor(Decl)
  };

  return DIGlobalVariable(CreateFunc(Elts));
}

/// createGlobalVariable - Create a new descriptor for the specified
/// variable.
DIGlobalVariable DIBuilder::createGlobalVariable(DIDescriptor Context,
                                                 StringRef Name,
                                                 StringRef LinkageName,
                                                 DIFile F, unsigned LineNumber,
                                                 DITypeRef Ty,
                                                 bool isLocalToUnit,
                                                 Value *Val, MDNode *Decl) {
  return createGlobalVariableHelper(VMContext, Context, Name, LinkageName, F,
                                    LineNumber, Ty, isLocalToUnit, Val, Decl, true,
                                    [&] (ArrayRef<Value *> Elts) -> MDNode * {
                                      MDNode *Node = MDNode::get(VMContext, Elts);
                                      AllGVs.push_back(Node);
                                      return Node;
                                    });
}

/// createTempGlobalVariableFwdDecl - Create a new temporary descriptor for the
/// specified variable declarartion.
DIGlobalVariable
DIBuilder::createTempGlobalVariableFwdDecl(DIDescriptor Context,
                                           StringRef Name,
                                           StringRef LinkageName,
                                           DIFile F, unsigned LineNumber,
                                           DITypeRef Ty,
                                           bool isLocalToUnit,
                                           Value *Val, MDNode *Decl) {
  return createGlobalVariableHelper(VMContext, Context, Name, LinkageName, F,
                                    LineNumber, Ty, isLocalToUnit, Val, Decl, false,
                                    [&] (ArrayRef<Value *> Elts) {
                                      return MDNode::getTemporary(VMContext, Elts);
                                    });
}

/// createVariable - Create a new descriptor for the specified variable.
DIVariable DIBuilder::createLocalVariable(unsigned Tag, DIDescriptor Scope,
                                          StringRef Name, DIFile File,
                                          unsigned LineNo, DITypeRef Ty,
                                          bool AlwaysPreserve, unsigned Flags,
                                          unsigned ArgNo) {
  DIDescriptor Context(getNonCompileUnitScope(Scope));
  assert((!Context || Context.isScope()) &&
         "createLocalVariable should be called with a valid Context");
  Value *Elts[] = {
    GetTagConstant(VMContext, Tag),
    getNonCompileUnitScope(Scope),
    MDString::get(VMContext, Name),
    File,
    ConstantInt::get(Type::getInt32Ty(VMContext), (LineNo | (ArgNo << 24))),
    Ty,
    ConstantInt::get(Type::getInt32Ty(VMContext), Flags),
    Constant::getNullValue(Type::getInt32Ty(VMContext))
  };
  MDNode *Node = MDNode::get(VMContext, Elts);
  if (AlwaysPreserve) {
    // The optimizer may remove local variable. If there is an interest
    // to preserve variable info in such situation then stash it in a
    // named mdnode.
    DISubprogram Fn(getDISubprogram(Scope));
    NamedMDNode *FnLocals = getOrInsertFnSpecificMDNode(M, Fn);
    FnLocals->addOperand(Node);
  }
  DIVariable RetVar(Node);
  assert(RetVar.isVariable() &&
         "createLocalVariable should return a valid DIVariable");
  return RetVar;
}

/// createComplexVariable - Create a new descriptor for the specified variable
/// which has a complex address expression for its address.
DIVariable DIBuilder::createComplexVariable(unsigned Tag, DIDescriptor Scope,
                                            StringRef Name, DIFile F,
                                            unsigned LineNo,
                                            DITypeRef Ty,
                                            ArrayRef<Value *> Addr,
                                            unsigned ArgNo) {
  assert(Addr.size() > 0 && "complex address is empty");
  Value *Elts[] = {
    GetTagConstant(VMContext, Tag),
    getNonCompileUnitScope(Scope),
    MDString::get(VMContext, Name),
    F,
    ConstantInt::get(Type::getInt32Ty(VMContext),
                     (LineNo | (ArgNo << 24))),
    Ty,
    Constant::getNullValue(Type::getInt32Ty(VMContext)),
    Constant::getNullValue(Type::getInt32Ty(VMContext)),
    MDNode::get(VMContext, Addr)
  };
  return DIVariable(MDNode::get(VMContext, Elts));
}

/// createVariablePiece - Create a descriptor to describe one part
/// of aggregate variable that is fragmented across multiple Values.
DIVariable DIBuilder::createVariablePiece(DIVariable Variable,
                                          unsigned OffsetInBytes,
                                          unsigned SizeInBytes) {
  assert(SizeInBytes > 0 && "zero-size piece");
  Value *Addr[] = {
    ConstantInt::get(Type::getInt32Ty(VMContext), OpPiece),
    ConstantInt::get(Type::getInt32Ty(VMContext), OffsetInBytes),
    ConstantInt::get(Type::getInt32Ty(VMContext), SizeInBytes)
  };

  assert((Variable->getNumOperands() == 8 || Variable.isVariablePiece()) &&
         "variable already has a complex address");
  SmallVector<Value *, 9> Elts;
  for (unsigned i = 0; i < 8; ++i)
    Elts.push_back(Variable->getOperand(i));

  Elts.push_back(MDNode::get(VMContext, Addr));
  return DIVariable(MDNode::get(VMContext, Elts));
}

/// createFunction - Create a new descriptor for the specified function.
/// FIXME: this is added for dragonegg. Once we update dragonegg
/// to call resolve function, this will be removed.
DISubprogram DIBuilder::createFunction(DIScopeRef Context, StringRef Name,
                                       StringRef LinkageName, DIFile File,
                                       unsigned LineNo, DICompositeType Ty,
                                       bool isLocalToUnit, bool isDefinition,
                                       unsigned ScopeLine, unsigned Flags,
                                       bool isOptimized, Function *Fn,
                                       MDNode *TParams, MDNode *Decl) {
  // dragonegg does not generate identifier for types, so using an empty map
  // to resolve the context should be fine.
  DITypeIdentifierMap EmptyMap;
  return createFunction(Context.resolve(EmptyMap), Name, LinkageName, File,
                        LineNo, Ty, isLocalToUnit, isDefinition, ScopeLine,
                        Flags, isOptimized, Fn, TParams, Decl);
}

static DISubprogram
createFunctionHelper(LLVMContext &VMContext, DIDescriptor Context, StringRef Name,
                     StringRef LinkageName, DIFile File, unsigned LineNo,
                     DICompositeType Ty, bool isLocalToUnit, bool isDefinition,
                     unsigned ScopeLine, unsigned Flags, bool isOptimized,
                     Function *Fn, MDNode *TParams, MDNode *Decl,
                     std::function<MDNode *(ArrayRef<Value *>)> CreateFunc) {
  assert(Ty.getTag() == dwarf::DW_TAG_subroutine_type &&
         "function types should be subroutines");
  Value *TElts[] = { GetTagConstant(VMContext, DW_TAG_base_type) };
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_subprogram),
    File.getFileNode(),
    DIScope(getNonCompileUnitScope(Context)).getRef(),
    MDString::get(VMContext, Name),
    MDString::get(VMContext, Name),
    MDString::get(VMContext, LinkageName),
    ConstantInt::get(Type::getInt32Ty(VMContext), LineNo),
    Ty,
    ConstantInt::get(Type::getInt1Ty(VMContext), isLocalToUnit),
    ConstantInt::get(Type::getInt1Ty(VMContext), isDefinition),
    ConstantInt::get(Type::getInt32Ty(VMContext), 0),
    ConstantInt::get(Type::getInt32Ty(VMContext), 0),
    nullptr,
    ConstantInt::get(Type::getInt32Ty(VMContext), Flags),
    ConstantInt::get(Type::getInt1Ty(VMContext), isOptimized),
    Fn,
    TParams,
    Decl,
    MDNode::getTemporary(VMContext, TElts),
    ConstantInt::get(Type::getInt32Ty(VMContext), ScopeLine)
  };

  DISubprogram S(CreateFunc(Elts));
  assert(S.isSubprogram() &&
         "createFunction should return a valid DISubprogram");
  return S;
}


/// createFunction - Create a new descriptor for the specified function.
DISubprogram DIBuilder::createFunction(DIDescriptor Context, StringRef Name,
                                       StringRef LinkageName, DIFile File,
                                       unsigned LineNo, DICompositeType Ty,
                                       bool isLocalToUnit, bool isDefinition,
                                       unsigned ScopeLine, unsigned Flags,
                                       bool isOptimized, Function *Fn,
                                       MDNode *TParams, MDNode *Decl) {
  return createFunctionHelper(VMContext, Context, Name, LinkageName, File,
                              LineNo, Ty, isLocalToUnit, isDefinition, ScopeLine,
                              Flags, isOptimized, Fn, TParams, Decl,
                              [&] (ArrayRef<Value *> Elts) -> MDNode *{
                                MDNode *Node = MDNode::get(VMContext, Elts);
                                // Create a named metadata so that we
                                // do not lose this mdnode.
                                if (isDefinition)
                                  AllSubprograms.push_back(Node);
                                return Node;
                              });
}

/// createTempFunctionFwdDecl - Create a new temporary descriptor for
/// the specified function declaration.
DISubprogram
DIBuilder::createTempFunctionFwdDecl(DIDescriptor Context, StringRef Name,
                                     StringRef LinkageName, DIFile File,
                                     unsigned LineNo, DICompositeType Ty,
                                     bool isLocalToUnit, bool isDefinition,
                                     unsigned ScopeLine, unsigned Flags,
                                     bool isOptimized, Function *Fn,
                                     MDNode *TParams, MDNode *Decl) {
  return createFunctionHelper(VMContext, Context, Name, LinkageName, File,
                              LineNo, Ty, isLocalToUnit, isDefinition, ScopeLine,
                              Flags, isOptimized, Fn, TParams, Decl,
                              [&] (ArrayRef<Value *> Elts) {
                                return MDNode::getTemporary(VMContext, Elts);
                              });
}

/// createMethod - Create a new descriptor for the specified C++ method.
DISubprogram DIBuilder::createMethod(DIDescriptor Context, StringRef Name,
                                     StringRef LinkageName, DIFile F,
                                     unsigned LineNo, DICompositeType Ty,
                                     bool isLocalToUnit, bool isDefinition,
                                     unsigned VK, unsigned VIndex,
                                     DIType VTableHolder, unsigned Flags,
                                     bool isOptimized, Function *Fn,
                                     MDNode *TParam) {
  assert(Ty.getTag() == dwarf::DW_TAG_subroutine_type &&
         "function types should be subroutines");
  assert(getNonCompileUnitScope(Context) &&
         "Methods should have both a Context and a context that isn't "
         "the compile unit.");
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_subprogram),
    F.getFileNode(),
    DIScope(Context).getRef(),
    MDString::get(VMContext, Name),
    MDString::get(VMContext, Name),
    MDString::get(VMContext, LinkageName),
    ConstantInt::get(Type::getInt32Ty(VMContext), LineNo),
    Ty,
    ConstantInt::get(Type::getInt1Ty(VMContext), isLocalToUnit),
    ConstantInt::get(Type::getInt1Ty(VMContext), isDefinition),
    ConstantInt::get(Type::getInt32Ty(VMContext), VK),
    ConstantInt::get(Type::getInt32Ty(VMContext), VIndex),
    VTableHolder.getRef(),
    ConstantInt::get(Type::getInt32Ty(VMContext), Flags),
    ConstantInt::get(Type::getInt1Ty(VMContext), isOptimized),
    Fn,
    TParam,
    Constant::getNullValue(Type::getInt32Ty(VMContext)),
    nullptr,
    // FIXME: Do we want to use different scope/lines?
    ConstantInt::get(Type::getInt32Ty(VMContext), LineNo)
  };
  MDNode *Node = MDNode::get(VMContext, Elts);
  if (isDefinition)
    AllSubprograms.push_back(Node);
  DISubprogram S(Node);
  assert(S.isSubprogram() && "createMethod should return a valid DISubprogram");
  return S;
}

/// createNameSpace - This creates new descriptor for a namespace
/// with the specified parent scope.
DINameSpace DIBuilder::createNameSpace(DIDescriptor Scope, StringRef Name,
                                       DIFile File, unsigned LineNo) {
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_namespace),
    File.getFileNode(),
    getNonCompileUnitScope(Scope),
    MDString::get(VMContext, Name),
    ConstantInt::get(Type::getInt32Ty(VMContext), LineNo)
  };
  DINameSpace R(MDNode::get(VMContext, Elts));
  assert(R.Verify() &&
         "createNameSpace should return a verifiable DINameSpace");
  return R;
}

/// createLexicalBlockFile - This creates a new MDNode that encapsulates
/// an existing scope with a new filename.
DILexicalBlockFile DIBuilder::createLexicalBlockFile(DIDescriptor Scope,
                                                     DIFile File,
                                                     unsigned Discriminator) {
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_lexical_block),
    File.getFileNode(),
    Scope,
    ConstantInt::get(Type::getInt32Ty(VMContext), Discriminator),
  };
  DILexicalBlockFile R(MDNode::get(VMContext, Elts));
  assert(
      R.Verify() &&
      "createLexicalBlockFile should return a verifiable DILexicalBlockFile");
  return R;
}

DILexicalBlock DIBuilder::createLexicalBlock(DIDescriptor Scope, DIFile File,
                                             unsigned Line, unsigned Col) {
  // FIXME: This isn't thread safe nor the right way to defeat MDNode uniquing.
  // I believe the right way is to have a self-referential element in the node.
  // Also: why do we bother with line/column - they're not used and the
  // documentation (SourceLevelDebugging.rst) claims the line/col are necessary
  // for uniquing, yet then we have this other solution (because line/col were
  // inadequate) anyway. Remove all 3 and replace them with a self-reference.

  // Defeat MDNode uniquing for lexical blocks by using unique id.
  static unsigned int unique_id = 0;
  Value *Elts[] = {
    GetTagConstant(VMContext, dwarf::DW_TAG_lexical_block),
    File.getFileNode(),
    getNonCompileUnitScope(Scope),
    ConstantInt::get(Type::getInt32Ty(VMContext), Line),
    ConstantInt::get(Type::getInt32Ty(VMContext), Col),
    ConstantInt::get(Type::getInt32Ty(VMContext), unique_id++)
  };
  DILexicalBlock R(MDNode::get(VMContext, Elts));
  assert(R.Verify() &&
         "createLexicalBlock should return a verifiable DILexicalBlock");
  return R;
}

/// insertDeclare - Insert a new llvm.dbg.declare intrinsic call.
Instruction *DIBuilder::insertDeclare(Value *Storage, DIVariable VarInfo,
                                      Instruction *InsertBefore) {
  assert(Storage && "no storage passed to dbg.declare");
  assert(VarInfo.isVariable() &&
         "empty or invalid DIVariable passed to dbg.declare");
  if (!DeclareFn)
    DeclareFn = Intrinsic::getDeclaration(&M, Intrinsic::dbg_declare);

  Value *Args[] = { MDNode::get(Storage->getContext(), Storage), VarInfo };
  return CallInst::Create(DeclareFn, Args, "", InsertBefore);
}

/// insertDeclare - Insert a new llvm.dbg.declare intrinsic call.
Instruction *DIBuilder::insertDeclare(Value *Storage, DIVariable VarInfo,
                                      BasicBlock *InsertAtEnd) {
  assert(Storage && "no storage passed to dbg.declare");
  assert(VarInfo.isVariable() &&
         "empty or invalid DIVariable passed to dbg.declare");
  if (!DeclareFn)
    DeclareFn = Intrinsic::getDeclaration(&M, Intrinsic::dbg_declare);

  Value *Args[] = { MDNode::get(Storage->getContext(), Storage), VarInfo };

  // If this block already has a terminator then insert this intrinsic
  // before the terminator.
  if (TerminatorInst *T = InsertAtEnd->getTerminator())
    return CallInst::Create(DeclareFn, Args, "", T);
  else
    return CallInst::Create(DeclareFn, Args, "", InsertAtEnd);
}

/// insertDbgValueIntrinsic - Insert a new llvm.dbg.value intrinsic call.
Instruction *DIBuilder::insertDbgValueIntrinsic(Value *V, uint64_t Offset,
                                                DIVariable VarInfo,
                                                Instruction *InsertBefore) {
  assert(V && "no value passed to dbg.value");
  assert(VarInfo.isVariable() &&
         "empty or invalid DIVariable passed to dbg.value");
  if (!ValueFn)
    ValueFn = Intrinsic::getDeclaration(&M, Intrinsic::dbg_value);

  Value *Args[] = { MDNode::get(V->getContext(), V),
                    ConstantInt::get(Type::getInt64Ty(V->getContext()), Offset),
                    VarInfo };
  return CallInst::Create(ValueFn, Args, "", InsertBefore);
}

/// insertDbgValueIntrinsic - Insert a new llvm.dbg.value intrinsic call.
Instruction *DIBuilder::insertDbgValueIntrinsic(Value *V, uint64_t Offset,
                                                DIVariable VarInfo,
                                                BasicBlock *InsertAtEnd) {
  assert(V && "no value passed to dbg.value");
  assert(VarInfo.isVariable() &&
         "empty or invalid DIVariable passed to dbg.value");
  if (!ValueFn)
    ValueFn = Intrinsic::getDeclaration(&M, Intrinsic::dbg_value);

  Value *Args[] = { MDNode::get(V->getContext(), V),
                    ConstantInt::get(Type::getInt64Ty(V->getContext()), Offset),
                    VarInfo };
  return CallInst::Create(ValueFn, Args, "", InsertAtEnd);
}