lib/Analysis/DebugInfo.cpp

//===--- DebugInfo.cpp - Debug Information Helper Classes -----------------===//
//
//                     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 helper classes used to build and interpret debug
// information in LLVM IR form.
//
//===----------------------------------------------------------------------===//

#include "llvm/Analysis/DebugInfo.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Intrinsics.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Instructions.h"
#include "llvm/Module.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/Streams.h"

using namespace llvm;
using namespace llvm::dwarf;

//===----------------------------------------------------------------------===//
// DIDescriptor
//===----------------------------------------------------------------------===//

/// ValidDebugInfo - Return true if V represents valid debug info value.
bool DIDescriptor::ValidDebugInfo(Value *V, CodeGenOpt::Level OptLevel) {
  if (!V)
    return false;

  GlobalVariable *GV = dyn_cast<GlobalVariable>(V->stripPointerCasts());
  if (!GV)
    return false;

  if (!GV->hasInternalLinkage () && !GV->hasLinkOnceLinkage())
    return false;

  DIDescriptor DI(GV);

  // Check current version. Allow Version6 for now.
  unsigned Version = DI.getVersion();
  if (Version != LLVMDebugVersion && Version != LLVMDebugVersion6)
    return false;

  unsigned Tag = DI.getTag();
  switch (Tag) {
  case DW_TAG_variable:
    assert(DIVariable(GV).Verify() && "Invalid DebugInfo value");
    break;
  case DW_TAG_compile_unit:
    assert(DICompileUnit(GV).Verify() && "Invalid DebugInfo value");
    break;
  case DW_TAG_subprogram:
    assert(DISubprogram(GV).Verify() && "Invalid DebugInfo value");
    break;
  case DW_TAG_lexical_block:
    // FIXME: This interfers with the quality of generated code during
    // optimization.
    if (OptLevel != CodeGenOpt::None)
      return false;
    // FALLTHROUGH
  default:
    break;
  }

  return true;
}

DIDescriptor::DIDescriptor(GlobalVariable *GV, unsigned RequiredTag) {
  DbgGV = GV;
  
  // If this is non-null, check to see if the Tag matches. If not, set to null.
  if (GV && getTag() != RequiredTag)
    DbgGV = 0;
}

const std::string &
DIDescriptor::getStringField(unsigned Elt, std::string &Result) const {
  if (DbgGV == 0) {
    Result.clear();
    return Result;
  }

  Constant *C = DbgGV->getInitializer();
  if (C == 0 || Elt >= C->getNumOperands()) {
    Result.clear();
    return Result;
  }

  // Fills in the string if it succeeds
  if (!GetConstantStringInfo(C->getOperand(Elt), Result))
    Result.clear();

  return Result;
}

uint64_t DIDescriptor::getUInt64Field(unsigned Elt) const {
  if (DbgGV == 0) return 0;

  Constant *C = DbgGV->getInitializer();
  if (C == 0 || Elt >= C->getNumOperands())
    return 0;

  if (ConstantInt *CI = dyn_cast<ConstantInt>(C->getOperand(Elt)))
    return CI->getZExtValue();
  return 0;
}

DIDescriptor DIDescriptor::getDescriptorField(unsigned Elt) const {
  if (DbgGV == 0) return DIDescriptor();

  Constant *C = DbgGV->getInitializer();
  if (C == 0 || Elt >= C->getNumOperands())
    return DIDescriptor();

  C = C->getOperand(Elt);
  return DIDescriptor(dyn_cast<GlobalVariable>(C->stripPointerCasts()));
}

GlobalVariable *DIDescriptor::getGlobalVariableField(unsigned Elt) const {
  if (DbgGV == 0) return 0;

  Constant *C = DbgGV->getInitializer();
  if (C == 0 || Elt >= C->getNumOperands())
    return 0;

  C = C->getOperand(Elt);
  return dyn_cast<GlobalVariable>(C->stripPointerCasts());
}

//===----------------------------------------------------------------------===//
// Simple Descriptor Constructors and other Methods
//===----------------------------------------------------------------------===//

// Needed by DIVariable::getType().
DIType::DIType(GlobalVariable *GV) : DIDescriptor(GV) {
  if (!GV) return;
  unsigned tag = getTag();
  if (tag != dwarf::DW_TAG_base_type && !DIDerivedType::isDerivedType(tag) &&
      !DICompositeType::isCompositeType(tag))
    DbgGV = 0;
}

/// isDerivedType - Return true if the specified tag is legal for
/// DIDerivedType.
bool DIType::isDerivedType(unsigned Tag) {
  switch (Tag) {
  case dwarf::DW_TAG_typedef:
  case dwarf::DW_TAG_pointer_type:
  case dwarf::DW_TAG_reference_type:
  case dwarf::DW_TAG_const_type:
  case dwarf::DW_TAG_volatile_type:
  case dwarf::DW_TAG_restrict_type:
  case dwarf::DW_TAG_member:
  case dwarf::DW_TAG_inheritance:
    return true;
  default:
    // FIXME: Even though it doesn't make sense, CompositeTypes are current
    // modelled as DerivedTypes, this should return true for them as well.
    return false;
  }
}

/// isCompositeType - Return true if the specified tag is legal for
/// DICompositeType.
bool DIType::isCompositeType(unsigned TAG) {
  switch (TAG) {
  case dwarf::DW_TAG_array_type:
  case dwarf::DW_TAG_structure_type:
  case dwarf::DW_TAG_union_type:
  case dwarf::DW_TAG_enumeration_type:
  case dwarf::DW_TAG_vector_type:
  case dwarf::DW_TAG_subroutine_type:
  case dwarf::DW_TAG_class_type:
    return true;
  default:
    return false;
  }
}

/// isVariable - Return true if the specified tag is legal for DIVariable.
bool DIVariable::isVariable(unsigned Tag) {
  switch (Tag) {
  case dwarf::DW_TAG_auto_variable:
  case dwarf::DW_TAG_arg_variable:
  case dwarf::DW_TAG_return_variable:
    return true;
  default:
    return false;
  }
}

unsigned DIArray::getNumElements() const {
  assert (DbgGV && "Invalid DIArray");
  Constant *C = DbgGV->getInitializer();
  assert (C && "Invalid DIArray initializer");
  return C->getNumOperands();
}

/// Verify - Verify that a compile unit is well formed.
bool DICompileUnit::Verify() const {
  if (isNull()) 
    return false;
  std::string Res;
  if (getFilename(Res).empty()) 
    return false;
  // It is possible that directory and produce string is empty.
  return true;
}

/// Verify - Verify that a type descriptor is well formed.
bool DIType::Verify() const {
  if (isNull()) 
    return false;
  if (getContext().isNull()) 
    return false;

  DICompileUnit CU = getCompileUnit();
  if (!CU.isNull() && !CU.Verify()) 
    return false;
  return true;
}

/// Verify - Verify that a composite type descriptor is well formed.
bool DICompositeType::Verify() const {
  if (isNull()) 
    return false;
  if (getContext().isNull()) 
    return false;

  DICompileUnit CU = getCompileUnit();
  if (!CU.isNull() && !CU.Verify()) 
    return false;
  return true;
}

/// Verify - Verify that a subprogram descriptor is well formed.
bool DISubprogram::Verify() const {
  if (isNull())
    return false;
  
  if (getContext().isNull())
    return false;

  DICompileUnit CU = getCompileUnit();
  if (!CU.Verify()) 
    return false;

  DICompositeType Ty = getType();
  if (!Ty.isNull() && !Ty.Verify())
    return false;
  return true;
}

/// Verify - Verify that a global variable descriptor is well formed.
bool DIGlobalVariable::Verify() const {
  if (isNull())
    return false;
  
  if (getContext().isNull())
    return false;

  DICompileUnit CU = getCompileUnit();
  if (!CU.isNull() && !CU.Verify()) 
    return false;

  DIType Ty = getType();
  if (!Ty.Verify())
    return false;

  if (!getGlobal())
    return false;

  return true;
}

/// Verify - Verify that a variable descriptor is well formed.
bool DIVariable::Verify() const {
  if (isNull())
    return false;
  
  if (getContext().isNull())
    return false;

  DIType Ty = getType();
  if (!Ty.Verify())
    return false;

  return true;
}

/// getOriginalTypeSize - If this type is derived from a base type then
/// return base type size.
uint64_t DIDerivedType::getOriginalTypeSize() const {
  if (getTag() != dwarf::DW_TAG_member)
    return getSizeInBits();
  DIType BT = getTypeDerivedFrom();
  if (BT.getTag() != dwarf::DW_TAG_base_type)
    return getSizeInBits();
  return BT.getSizeInBits();
}

/// describes - Return true if this subprogram provides debugging
/// information for the function F.
bool DISubprogram::describes(const Function *F) {
  assert (F && "Invalid function");
  std::string Name;
  getLinkageName(Name);
  if (Name.empty())
    getName(Name);
  if (!Name.empty() && (strcmp(Name.c_str(), F->getNameStart()) == false))
    return true;
  return false;
}

//===----------------------------------------------------------------------===//
// DIFactory: Basic Helpers
//===----------------------------------------------------------------------===//

DIFactory::DIFactory(Module &m)
  : M(m), StopPointFn(0), FuncStartFn(0), RegionStartFn(0), RegionEndFn(0),
    DeclareFn(0) {
  EmptyStructPtr = PointerType::getUnqual(StructType::get(NULL, NULL));
}

/// getCastToEmpty - Return this descriptor as a Constant* with type '{}*'.
/// This is only valid when the descriptor is non-null.
Constant *DIFactory::getCastToEmpty(DIDescriptor D) {
  if (D.isNull()) return Constant::getNullValue(EmptyStructPtr);
  return ConstantExpr::getBitCast(D.getGV(), EmptyStructPtr);
}

Constant *DIFactory::GetTagConstant(unsigned TAG) {
  assert((TAG & LLVMDebugVersionMask) == 0 &&
         "Tag too large for debug encoding!");
  return ConstantInt::get(Type::Int32Ty, TAG | LLVMDebugVersion);
}

Constant *DIFactory::GetStringConstant(const std::string &String) {
  // Check string cache for previous edition.
  Constant *&Slot = StringCache[String];
  
  // Return Constant if previously defined.
  if (Slot) return Slot;
  
  const PointerType *DestTy = PointerType::getUnqual(Type::Int8Ty);
  
  // If empty string then use a i8* null instead.
  if (String.empty())
    return Slot = ConstantPointerNull::get(DestTy);

  // Construct string as an llvm constant.
  Constant *ConstStr = ConstantArray::get(String);
    
  // Otherwise create and return a new string global.
  GlobalVariable *StrGV = new GlobalVariable(ConstStr->getType(), true,
                                             GlobalVariable::InternalLinkage,
                                             ConstStr, ".str", &M);
  StrGV->setSection("llvm.metadata");
  return Slot = ConstantExpr::getBitCast(StrGV, DestTy);
}

/// GetOrCreateAnchor - Look up an anchor for the specified tag and name.  If it
/// already exists, return it.  If not, create a new one and return it.
DIAnchor DIFactory::GetOrCreateAnchor(unsigned TAG, const char *Name) {
  const Type *EltTy = StructType::get(Type::Int32Ty, Type::Int32Ty, NULL);
  
  // Otherwise, create the global or return it if already in the module.
  Constant *C = M.getOrInsertGlobal(Name, EltTy);
  assert(isa<GlobalVariable>(C) && "Incorrectly typed anchor?");
  GlobalVariable *GV = cast<GlobalVariable>(C);
  
  // If it has an initializer, it is already in the module.
  if (GV->hasInitializer()) 
    return SubProgramAnchor = DIAnchor(GV);
  
  GV->setLinkage(GlobalValue::LinkOnceAnyLinkage);
  GV->setSection("llvm.metadata");
  GV->setConstant(true);
  M.addTypeName("llvm.dbg.anchor.type", EltTy);
  
  // Otherwise, set the initializer.
  Constant *Elts[] = {
    GetTagConstant(dwarf::DW_TAG_anchor),
    ConstantInt::get(Type::Int32Ty, TAG)
  };
  
  GV->setInitializer(ConstantStruct::get(Elts, 2));
  return DIAnchor(GV);
}



//===----------------------------------------------------------------------===//
// DIFactory: Primary Constructors
//===----------------------------------------------------------------------===//

/// GetOrCreateCompileUnitAnchor - Return the anchor for compile units,
/// creating a new one if there isn't already one in the module.
DIAnchor DIFactory::GetOrCreateCompileUnitAnchor() {
  // If we already created one, just return it.
  if (!CompileUnitAnchor.isNull())
    return CompileUnitAnchor;
  return CompileUnitAnchor = GetOrCreateAnchor(dwarf::DW_TAG_compile_unit,
                                               "llvm.dbg.compile_units");
}

/// GetOrCreateSubprogramAnchor - Return the anchor for subprograms,
/// creating a new one if there isn't already one in the module.
DIAnchor DIFactory::GetOrCreateSubprogramAnchor() {
  // If we already created one, just return it.
  if (!SubProgramAnchor.isNull())
    return SubProgramAnchor;
  return SubProgramAnchor = GetOrCreateAnchor(dwarf::DW_TAG_subprogram,
                                              "llvm.dbg.subprograms");
}

/// GetOrCreateGlobalVariableAnchor - Return the anchor for globals,
/// creating a new one if there isn't already one in the module.
DIAnchor DIFactory::GetOrCreateGlobalVariableAnchor() {
  // If we already created one, just return it.
  if (!GlobalVariableAnchor.isNull())
    return GlobalVariableAnchor;
  return GlobalVariableAnchor = GetOrCreateAnchor(dwarf::DW_TAG_variable,
                                                  "llvm.dbg.global_variables");
}

/// GetOrCreateArray - Create an descriptor for an array of descriptors. 
/// This implicitly uniques the arrays created.
DIArray DIFactory::GetOrCreateArray(DIDescriptor *Tys, unsigned NumTys) {
  SmallVector<Constant*, 16> Elts;
  
  for (unsigned i = 0; i != NumTys; ++i)
    Elts.push_back(getCastToEmpty(Tys[i]));
  
  Constant *Init = ConstantArray::get(ArrayType::get(EmptyStructPtr,
                                                     Elts.size()),
                                      Elts.data(), Elts.size());
  // If we already have this array, just return the uniqued version.
  DIDescriptor &Entry = SimpleConstantCache[Init];
  if (!Entry.isNull()) return DIArray(Entry.getGV());
  
  GlobalVariable *GV = new GlobalVariable(Init->getType(), true,
                                          GlobalValue::InternalLinkage,
                                          Init, "llvm.dbg.array", &M);
  GV->setSection("llvm.metadata");
  Entry = DIDescriptor(GV);
  return DIArray(GV);
}

/// GetOrCreateSubrange - Create a descriptor for a value range.  This
/// implicitly uniques the values returned.
DISubrange DIFactory::GetOrCreateSubrange(int64_t Lo, int64_t Hi) {
  Constant *Elts[] = {
    GetTagConstant(dwarf::DW_TAG_subrange_type),
    ConstantInt::get(Type::Int64Ty, Lo),
    ConstantInt::get(Type::Int64Ty, Hi)
  };
  
  Constant *Init = ConstantStruct::get(Elts, sizeof(Elts)/sizeof(Elts[0]));

  // If we already have this range, just return the uniqued version.
  DIDescriptor &Entry = SimpleConstantCache[Init];
  if (!Entry.isNull()) return DISubrange(Entry.getGV());
  
  M.addTypeName("llvm.dbg.subrange.type", Init->getType());

  GlobalVariable *GV = new GlobalVariable(Init->getType(), true,
                                          GlobalValue::InternalLinkage,
                                          Init, "llvm.dbg.subrange", &M);
  GV->setSection("llvm.metadata");
  Entry = DIDescriptor(GV);
  return DISubrange(GV);
}



/// CreateCompileUnit - Create a new descriptor for the specified compile
/// unit.  Note that this does not unique compile units within the module.
DICompileUnit DIFactory::CreateCompileUnit(unsigned LangID,
                                           const std::string &Filename,
                                           const std::string &Directory,
                                           const std::string &Producer,
                                           bool isMain,
                                           bool isOptimized,
                                           const char *Flags,
                                           unsigned RunTimeVer) {
  Constant *Elts[] = {
    GetTagConstant(dwarf::DW_TAG_compile_unit),
    getCastToEmpty(GetOrCreateCompileUnitAnchor()),
    ConstantInt::get(Type::Int32Ty, LangID),
    GetStringConstant(Filename),
    GetStringConstant(Directory),
    GetStringConstant(Producer),
    ConstantInt::get(Type::Int1Ty, isMain),
    ConstantInt::get(Type::Int1Ty, isOptimized),
    GetStringConstant(Flags),
    ConstantInt::get(Type::Int32Ty, RunTimeVer)
  };
  
  Constant *Init = ConstantStruct::get(Elts, sizeof(Elts)/sizeof(Elts[0]));
  
  M.addTypeName("llvm.dbg.compile_unit.type", Init->getType());
  GlobalVariable *GV = new GlobalVariable(Init->getType(), true,
                                          GlobalValue::InternalLinkage,
                                          Init, "llvm.dbg.compile_unit", &M);
  GV->setSection("llvm.metadata");
  return DICompileUnit(GV);
}

/// CreateEnumerator - Create a single enumerator value.
DIEnumerator DIFactory::CreateEnumerator(const std::string &Name, uint64_t Val){
  Constant *Elts[] = {
    GetTagConstant(dwarf::DW_TAG_enumerator),
    GetStringConstant(Name),
    ConstantInt::get(Type::Int64Ty, Val)
  };
  
  Constant *Init = ConstantStruct::get(Elts, sizeof(Elts)/sizeof(Elts[0]));
  
  M.addTypeName("llvm.dbg.enumerator.type", Init->getType());
  GlobalVariable *GV = new GlobalVariable(Init->getType(), true,
                                          GlobalValue::InternalLinkage,
                                          Init, "llvm.dbg.enumerator", &M);
  GV->setSection("llvm.metadata");
  return DIEnumerator(GV);
}


/// CreateBasicType - Create a basic type like int, float, etc.
DIBasicType DIFactory::CreateBasicType(DIDescriptor Context,
                                      const std::string &Name,
                                       DICompileUnit CompileUnit,
                                       unsigned LineNumber,
                                       uint64_t SizeInBits,
                                       uint64_t AlignInBits,
                                       uint64_t OffsetInBits, unsigned Flags,
                                       unsigned Encoding) {
  Constant *Elts[] = {
    GetTagConstant(dwarf::DW_TAG_base_type),
    getCastToEmpty(Context),
    GetStringConstant(Name),
    getCastToEmpty(CompileUnit),
    ConstantInt::get(Type::Int32Ty, LineNumber),
    ConstantInt::get(Type::Int64Ty, SizeInBits),
    ConstantInt::get(Type::Int64Ty, AlignInBits),
    ConstantInt::get(Type::Int64Ty, OffsetInBits),
    ConstantInt::get(Type::Int32Ty, Flags),
    ConstantInt::get(Type::Int32Ty, Encoding)
  };
  
  Constant *Init = ConstantStruct::get(Elts, sizeof(Elts)/sizeof(Elts[0]));
  
  M.addTypeName("llvm.dbg.basictype.type", Init->getType());
  GlobalVariable *GV = new GlobalVariable(Init->getType(), true,
                                          GlobalValue::InternalLinkage,
                                          Init, "llvm.dbg.basictype", &M);
  GV->setSection("llvm.metadata");
  return DIBasicType(GV);
}

/// CreateDerivedType - Create a derived type like const qualified type,
/// pointer, typedef, etc.
DIDerivedType DIFactory::CreateDerivedType(unsigned Tag,
                                           DIDescriptor Context,
                                           const std::string &Name,
                                           DICompileUnit CompileUnit,
                                           unsigned LineNumber,
                                           uint64_t SizeInBits,
                                           uint64_t AlignInBits,
                                           uint64_t OffsetInBits,
                                           unsigned Flags,
                                           DIType DerivedFrom) {
  Constant *Elts[] = {
    GetTagConstant(Tag),
    getCastToEmpty(Context),
    GetStringConstant(Name),
    getCastToEmpty(CompileUnit),
    ConstantInt::get(Type::Int32Ty, LineNumber),
    ConstantInt::get(Type::Int64Ty, SizeInBits),
    ConstantInt::get(Type::Int64Ty, AlignInBits),
    ConstantInt::get(Type::Int64Ty, OffsetInBits),
    ConstantInt::get(Type::Int32Ty, Flags),
    getCastToEmpty(DerivedFrom)
  };
  
  Constant *Init = ConstantStruct::get(Elts, sizeof(Elts)/sizeof(Elts[0]));
  
  M.addTypeName("llvm.dbg.derivedtype.type", Init->getType());
  GlobalVariable *GV = new GlobalVariable(Init->getType(), true,
                                          GlobalValue::InternalLinkage,
                                          Init, "llvm.dbg.derivedtype", &M);
  GV->setSection("llvm.metadata");
  return DIDerivedType(GV);
}

/// CreateCompositeType - Create a composite type like array, struct, etc.
DICompositeType DIFactory::CreateCompositeType(unsigned Tag,
                                               DIDescriptor Context,
                                               const std::string &Name,
                                               DICompileUnit CompileUnit,
                                               unsigned LineNumber,
                                               uint64_t SizeInBits,
                                               uint64_t AlignInBits,
                                               uint64_t OffsetInBits,
                                               unsigned Flags,
                                               DIType DerivedFrom,
                                               DIArray Elements,
                                               unsigned RuntimeLang) {

  Constant *Elts[] = {
    GetTagConstant(Tag),
    getCastToEmpty(Context),
    GetStringConstant(Name),
    getCastToEmpty(CompileUnit),
    ConstantInt::get(Type::Int32Ty, LineNumber),
    ConstantInt::get(Type::Int64Ty, SizeInBits),
    ConstantInt::get(Type::Int64Ty, AlignInBits),
    ConstantInt::get(Type::Int64Ty, OffsetInBits),
    ConstantInt::get(Type::Int32Ty, Flags),
    getCastToEmpty(DerivedFrom),
    getCastToEmpty(Elements),
    ConstantInt::get(Type::Int32Ty, RuntimeLang)
  };
  
  Constant *Init = ConstantStruct::get(Elts, sizeof(Elts)/sizeof(Elts[0]));
  
  M.addTypeName("llvm.dbg.composite.type", Init->getType());
  GlobalVariable *GV = new GlobalVariable(Init->getType(), true,
                                          GlobalValue::InternalLinkage,
                                          Init, "llvm.dbg.composite", &M);
  GV->setSection("llvm.metadata");
  return DICompositeType(GV);
}


/// CreateSubprogram - Create a new descriptor for the specified subprogram.
/// See comments in DISubprogram for descriptions of these fields.  This
/// method does not unique the generated descriptors.
DISubprogram DIFactory::CreateSubprogram(DIDescriptor Context, 
                                         const std::string &Name,
                                         const std::string &DisplayName,
                                         const std::string &LinkageName,
                                         DICompileUnit CompileUnit,
                                         unsigned LineNo, DIType Type,
                                         bool isLocalToUnit,
                                         bool isDefinition) {

  Constant *Elts[] = {
    GetTagConstant(dwarf::DW_TAG_subprogram),
    getCastToEmpty(GetOrCreateSubprogramAnchor()),
    getCastToEmpty(Context),
    GetStringConstant(Name),
    GetStringConstant(DisplayName),
    GetStringConstant(LinkageName),
    getCastToEmpty(CompileUnit),
    ConstantInt::get(Type::Int32Ty, LineNo),
    getCastToEmpty(Type),
    ConstantInt::get(Type::Int1Ty, isLocalToUnit),
    ConstantInt::get(Type::Int1Ty, isDefinition)
  };
  
  Constant *Init = ConstantStruct::get(Elts, sizeof(Elts)/sizeof(Elts[0]));
  
  M.addTypeName("llvm.dbg.subprogram.type", Init->getType());
  GlobalVariable *GV = new GlobalVariable(Init->getType(), true,
                                          GlobalValue::InternalLinkage,
                                          Init, "llvm.dbg.subprogram", &M);
  GV->setSection("llvm.metadata");
  return DISubprogram(GV);
}

/// CreateGlobalVariable - Create a new descriptor for the specified global.
DIGlobalVariable
DIFactory::CreateGlobalVariable(DIDescriptor Context, const std::string &Name,
                                const std::string &DisplayName,
                                const std::string &LinkageName,
                                DICompileUnit CompileUnit,
                                unsigned LineNo, DIType Type,bool isLocalToUnit,
                                bool isDefinition, llvm::GlobalVariable *Val) {
  Constant *Elts[] = {
    GetTagConstant(dwarf::DW_TAG_variable),
    getCastToEmpty(GetOrCreateGlobalVariableAnchor()),
    getCastToEmpty(Context),
    GetStringConstant(Name),
    GetStringConstant(DisplayName),
    GetStringConstant(LinkageName),
    getCastToEmpty(CompileUnit),
    ConstantInt::get(Type::Int32Ty, LineNo),
    getCastToEmpty(Type),
    ConstantInt::get(Type::Int1Ty, isLocalToUnit),
    ConstantInt::get(Type::Int1Ty, isDefinition),
    ConstantExpr::getBitCast(Val, EmptyStructPtr)
  };
  
  Constant *Init = ConstantStruct::get(Elts, sizeof(Elts)/sizeof(Elts[0]));
  
  M.addTypeName("llvm.dbg.global_variable.type", Init->getType());
  GlobalVariable *GV = new GlobalVariable(Init->getType(), true,
                                          GlobalValue::InternalLinkage,
                                          Init, "llvm.dbg.global_variable", &M);
  GV->setSection("llvm.metadata");
  return DIGlobalVariable(GV);
}


/// CreateVariable - Create a new descriptor for the specified variable.
DIVariable DIFactory::CreateVariable(unsigned Tag, DIDescriptor Context,
                                     const std::string &Name,
                                     DICompileUnit CompileUnit, unsigned LineNo,
                                     DIType Type) {
  Constant *Elts[] = {
    GetTagConstant(Tag),
    getCastToEmpty(Context),
    GetStringConstant(Name),
    getCastToEmpty(CompileUnit),
    ConstantInt::get(Type::Int32Ty, LineNo),
    getCastToEmpty(Type)
  };
  
  Constant *Init = ConstantStruct::get(Elts, sizeof(Elts)/sizeof(Elts[0]));
  
  M.addTypeName("llvm.dbg.variable.type", Init->getType());
  GlobalVariable *GV = new GlobalVariable(Init->getType(), true,
                                          GlobalValue::InternalLinkage,
                                          Init, "llvm.dbg.variable", &M);
  GV->setSection("llvm.metadata");
  return DIVariable(GV);
}


/// CreateBlock - This creates a descriptor for a lexical block with the
/// specified parent context.
DIBlock DIFactory::CreateBlock(DIDescriptor Context) {
  Constant *Elts[] = {
    GetTagConstant(dwarf::DW_TAG_lexical_block),
    getCastToEmpty(Context)
  };
  
  Constant *Init = ConstantStruct::get(Elts, sizeof(Elts)/sizeof(Elts[0]));
  
  M.addTypeName("llvm.dbg.block.type", Init->getType());
  GlobalVariable *GV = new GlobalVariable(Init->getType(), true,
                                          GlobalValue::InternalLinkage,
                                          Init, "llvm.dbg.block", &M);
  GV->setSection("llvm.metadata");
  return DIBlock(GV);
}


//===----------------------------------------------------------------------===//
// DIFactory: Routines for inserting code into a function
//===----------------------------------------------------------------------===//

/// InsertStopPoint - Create a new llvm.dbg.stoppoint intrinsic invocation,
/// inserting it at the end of the specified basic block.
void DIFactory::InsertStopPoint(DICompileUnit CU, unsigned LineNo,
                                unsigned ColNo, BasicBlock *BB) {
  
  // Lazily construct llvm.dbg.stoppoint function.
  if (!StopPointFn)
    StopPointFn = llvm::Intrinsic::getDeclaration(&M, 
                                              llvm::Intrinsic::dbg_stoppoint);
  
  // Invoke llvm.dbg.stoppoint
  Value *Args[] = {
    llvm::ConstantInt::get(llvm::Type::Int32Ty, LineNo),
    llvm::ConstantInt::get(llvm::Type::Int32Ty, ColNo),
    getCastToEmpty(CU)
  };
  CallInst::Create(StopPointFn, Args, Args+3, "", BB);
}

/// InsertSubprogramStart - Create a new llvm.dbg.func.start intrinsic to
/// mark the start of the specified subprogram.
void DIFactory::InsertSubprogramStart(DISubprogram SP, BasicBlock *BB) {
  // Lazily construct llvm.dbg.func.start.
  if (!FuncStartFn)
    FuncStartFn = Intrinsic::getDeclaration(&M, Intrinsic::dbg_func_start);
  
  // Call llvm.dbg.func.start which also implicitly sets a stoppoint.
  CallInst::Create(FuncStartFn, getCastToEmpty(SP), "", BB);
}

/// InsertRegionStart - Insert a new llvm.dbg.region.start intrinsic call to
/// mark the start of a region for the specified scoping descriptor.
void DIFactory::InsertRegionStart(DIDescriptor D, BasicBlock *BB) {
  // Lazily construct llvm.dbg.region.start function.
  if (!RegionStartFn)
    RegionStartFn = Intrinsic::getDeclaration(&M, Intrinsic::dbg_region_start);

  // Call llvm.dbg.func.start.
  CallInst::Create(RegionStartFn, getCastToEmpty(D), "", BB);
}

/// InsertRegionEnd - Insert a new llvm.dbg.region.end intrinsic call to
/// mark the end of a region for the specified scoping descriptor.
void DIFactory::InsertRegionEnd(DIDescriptor D, BasicBlock *BB) {
  // Lazily construct llvm.dbg.region.end function.
  if (!RegionEndFn)
    RegionEndFn = Intrinsic::getDeclaration(&M, Intrinsic::dbg_region_end);

  // Call llvm.dbg.region.end.
  CallInst::Create(RegionEndFn, getCastToEmpty(D), "", BB);
}

/// InsertDeclare - Insert a new llvm.dbg.declare intrinsic call.
void DIFactory::InsertDeclare(Value *Storage, DIVariable D, BasicBlock *BB) {
  // Cast the storage to a {}* for the call to llvm.dbg.declare.
  Storage = new BitCastInst(Storage, EmptyStructPtr, "", BB);
  
  if (!DeclareFn)
    DeclareFn = Intrinsic::getDeclaration(&M, Intrinsic::dbg_declare);

  Value *Args[] = { Storage, getCastToEmpty(D) };
  CallInst::Create(DeclareFn, Args, Args+2, "", BB);
}

namespace llvm {
  /// findStopPoint - Find the stoppoint coressponding to this instruction, that
  /// is the stoppoint that dominates this instruction.
  const DbgStopPointInst *findStopPoint(const Instruction *Inst) {
    if (const DbgStopPointInst *DSI = dyn_cast<DbgStopPointInst>(Inst))
      return DSI;

    const BasicBlock *BB = Inst->getParent();
    BasicBlock::const_iterator I = Inst, B;
    while (BB) {
      B = BB->begin();

      // A BB consisting only of a terminator can't have a stoppoint.
      while (I != B) {
        --I;
        if (const DbgStopPointInst *DSI = dyn_cast<DbgStopPointInst>(I))
          return DSI;
      }

      // This BB didn't have a stoppoint: if there is only one predecessor, look
      // for a stoppoint there. We could use getIDom(), but that would require
      // dominator info.
      BB = I->getParent()->getUniquePredecessor();
      if (BB)
        I = BB->getTerminator();
    }

    return 0;
  }

  /// findBBStopPoint - Find the stoppoint corresponding to first real
  /// (non-debug intrinsic) instruction in this Basic Block, and return the
  /// stoppoint for it.
  const DbgStopPointInst *findBBStopPoint(const BasicBlock *BB) {
    for(BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I)
      if (const DbgStopPointInst *DSI = dyn_cast<DbgStopPointInst>(I))
        return DSI;

    // Fallback to looking for stoppoint of unique predecessor. Useful if this
    // BB contains no stoppoints, but unique predecessor does.
    BB = BB->getUniquePredecessor();
    if (BB)
      return findStopPoint(BB->getTerminator());

    return 0;
  }

  Value *findDbgGlobalDeclare(GlobalVariable *V) {
    const Module *M = V->getParent();
    const Type *Ty = M->getTypeByName("llvm.dbg.global_variable.type");
    if (!Ty) return 0;

    Ty = PointerType::get(Ty, 0);

    Value *Val = V->stripPointerCasts();
    for (Value::use_iterator I = Val->use_begin(), E = Val->use_end();
         I != E; ++I) {
      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(I)) {
        if (CE->getOpcode() == Instruction::BitCast) {
          Value *VV = CE;

          while (VV->hasOneUse())
            VV = *VV->use_begin();

          if (VV->getType() == Ty)
            return VV;
        }
      }
    }
    
    if (Val->getType() == Ty)
      return Val;

    return 0;
  }

  /// Finds the llvm.dbg.declare intrinsic corresponding to this value if any.
  /// It looks through pointer casts too.
  const DbgDeclareInst *findDbgDeclare(const Value *V, bool stripCasts) {
    if (stripCasts) {
      V = V->stripPointerCasts();

      // Look for the bitcast.
      for (Value::use_const_iterator I = V->use_begin(), E =V->use_end();
            I != E; ++I)
        if (isa<BitCastInst>(I))
          return findDbgDeclare(*I, false);

      return 0;
    }

    // Find llvm.dbg.declare among uses of the instruction.
    for (Value::use_const_iterator I = V->use_begin(), E =V->use_end();
          I != E; ++I)
      if (const DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(I))
        return DDI;

    return 0;
  }

  bool getLocationInfo(const Value *V, std::string &DisplayName,
                       std::string &Type, unsigned &LineNo, std::string &File,
                       std::string &Dir) {
    DICompileUnit Unit;
    DIType TypeD;

    if (GlobalVariable *GV = dyn_cast<GlobalVariable>(const_cast<Value*>(V))) {
      Value *DIGV = findDbgGlobalDeclare(GV);
      if (!DIGV) return false;
      DIGlobalVariable Var(cast<GlobalVariable>(DIGV));

      Var.getDisplayName(DisplayName);
      LineNo = Var.getLineNumber();
      Unit = Var.getCompileUnit();
      TypeD = Var.getType();
    } else {
      const DbgDeclareInst *DDI = findDbgDeclare(V);
      if (!DDI) return false;
      DIVariable Var(cast<GlobalVariable>(DDI->getVariable()));

      Var.getName(DisplayName);
      LineNo = Var.getLineNumber();
      Unit = Var.getCompileUnit();
      TypeD = Var.getType();
    }

    TypeD.getName(Type);
    Unit.getFilename(File);
    Unit.getDirectory(Dir);
    return true;
  }
}

/// dump - Print descriptor.
void DIDescriptor::dump() const {
  cerr << "[" << dwarf::TagString(getTag()) << "] ";
  cerr << std::hex << "[GV:" << DbgGV << "]" << std::dec;
}

/// dump - Print compile unit.
void DICompileUnit::dump() const {
  if (getLanguage())
    cerr << " [" << dwarf::LanguageString(getLanguage()) << "] ";

  std::string Res1, Res2;
  cerr << " [" << getDirectory(Res1) << "/" << getFilename(Res2) << " ]";
}

/// dump - Print type.
void DIType::dump() const {
  if (isNull()) return;

  std::string Res;
  if (!getName(Res).empty())
    cerr << " [" << Res << "] ";

  unsigned Tag = getTag();
  cerr << " [" << dwarf::TagString(Tag) << "] ";

  // TODO : Print context
  getCompileUnit().dump();
  cerr << " [" 
       << getLineNumber() << ", " 
       << getSizeInBits() << ", "
       << getAlignInBits() << ", "
       << getOffsetInBits() 
       << "] ";

  if (isPrivate()) 
    cerr << " [private] ";
  else if (isProtected())
    cerr << " [protected] ";

  if (isForwardDecl())
    cerr << " [fwd] ";

  if (isBasicType(Tag))
    DIBasicType(DbgGV).dump();
  else if (isDerivedType(Tag))
    DIDerivedType(DbgGV).dump();
  else if (isCompositeType(Tag))
    DICompositeType(DbgGV).dump();
  else {
    cerr << "Invalid DIType\n";
    return;
  }

  cerr << "\n";
}

/// dump - Print basic type.
void DIBasicType::dump() const {
  cerr << " [" << dwarf::AttributeEncodingString(getEncoding()) << "] ";
}

/// dump - Print derived type.
void DIDerivedType::dump() const {
  cerr << "\n\t Derived From: "; getTypeDerivedFrom().dump();
}

/// dump - Print composite type.
void DICompositeType::dump() const {
  DIArray A = getTypeArray();
  if (A.isNull())
    return;
  cerr << " [" << A.getNumElements() << " elements]";
}

/// dump - Print global.
void DIGlobal::dump() const {
  std::string Res;
  if (!getName(Res).empty())
    cerr << " [" << Res << "] ";

  unsigned Tag = getTag();
  cerr << " [" << dwarf::TagString(Tag) << "] ";

  // TODO : Print context
  getCompileUnit().dump();
  cerr << " [" << getLineNumber() << "] ";

  if (isLocalToUnit())
    cerr << " [local] ";

  if (isDefinition())
    cerr << " [def] ";

  if (isGlobalVariable(Tag))
    DIGlobalVariable(DbgGV).dump();

  cerr << "\n";
}

/// dump - Print subprogram.
void DISubprogram::dump() const {
  DIGlobal::dump();
}

/// dump - Print global variable.
void DIGlobalVariable::dump() const {
  cerr << " ["; getGlobal()->dump(); cerr << "] ";
}

/// dump - Print variable.
void DIVariable::dump() const {
  std::string Res;
  if (!getName(Res).empty())
    cerr << " [" << Res << "] ";

  getCompileUnit().dump();
  cerr << " [" << getLineNumber() << "] ";
  getType().dump();
  cerr << "\n";
}