xref: /external/clang/lib/Serialization/ASTWriter.cpp

//===--- ASTWriter.cpp - AST File Writer ----------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This file defines the ASTWriter class, which writes AST files.
//
//===----------------------------------------------------------------------===//

#include "clang/Serialization/ASTWriter.h"
#include "ASTCommon.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclContextInternals.h"
#include "clang/AST/DeclFriend.h"
#include "clang/AST/DeclLookups.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/Type.h"
#include "clang/AST/TypeLocVisitor.h"
#include "clang/Basic/DiagnosticOptions.h"
#include "clang/Basic/FileManager.h"
#include "clang/Basic/FileSystemStatCache.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/SourceManagerInternals.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Basic/TargetOptions.h"
#include "clang/Basic/Version.h"
#include "clang/Basic/VersionTuple.h"
#include "clang/Lex/HeaderSearch.h"
#include "clang/Lex/HeaderSearchOptions.h"
#include "clang/Lex/MacroInfo.h"
#include "clang/Lex/PreprocessingRecord.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Lex/PreprocessorOptions.h"
#include "clang/Sema/IdentifierResolver.h"
#include "clang/Sema/Sema.h"
#include "clang/Serialization/ASTReader.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Bitcode/BitstreamWriter.h"
#include "llvm/Support/EndianStream.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/OnDiskHashTable.h"
#include "llvm/Support/Path.h"
#include <algorithm>
#include <cstdio>
#include <string.h>
#include <utility>
using namespace clang;
using namespace clang::serialization;

template <typename T, typename Allocator>
static StringRef data(const std::vector<T, Allocator> &v) {
  if (v.empty()) return StringRef();
  return StringRef(reinterpret_cast<const char*>(&v[0]),
                         sizeof(T) * v.size());
}

template <typename T>
static StringRef data(const SmallVectorImpl<T> &v) {
  return StringRef(reinterpret_cast<const char*>(v.data()),
                         sizeof(T) * v.size());
}

//===----------------------------------------------------------------------===//
// Type serialization
//===----------------------------------------------------------------------===//

namespace {
  class ASTTypeWriter {
    ASTWriter &Writer;
    ASTWriter::RecordDataImpl &Record;

  public:
    /// \brief Type code that corresponds to the record generated.
    TypeCode Code;

    ASTTypeWriter(ASTWriter &Writer, ASTWriter::RecordDataImpl &Record)
      : Writer(Writer), Record(Record), Code(TYPE_EXT_QUAL) { }

    void VisitArrayType(const ArrayType *T);
    void VisitFunctionType(const FunctionType *T);
    void VisitTagType(const TagType *T);

#define TYPE(Class, Base) void Visit##Class##Type(const Class##Type *T);
#define ABSTRACT_TYPE(Class, Base)
#include "clang/AST/TypeNodes.def"
  };
}

void ASTTypeWriter::VisitBuiltinType(const BuiltinType *T) {
  llvm_unreachable("Built-in types are never serialized");
}

void ASTTypeWriter::VisitComplexType(const ComplexType *T) {
  Writer.AddTypeRef(T->getElementType(), Record);
  Code = TYPE_COMPLEX;
}

void ASTTypeWriter::VisitPointerType(const PointerType *T) {
  Writer.AddTypeRef(T->getPointeeType(), Record);
  Code = TYPE_POINTER;
}

void ASTTypeWriter::VisitDecayedType(const DecayedType *T) {
  Writer.AddTypeRef(T->getOriginalType(), Record);
  Code = TYPE_DECAYED;
}

void ASTTypeWriter::VisitAdjustedType(const AdjustedType *T) {
  Writer.AddTypeRef(T->getOriginalType(), Record);
  Writer.AddTypeRef(T->getAdjustedType(), Record);
  Code = TYPE_ADJUSTED;
}

void ASTTypeWriter::VisitBlockPointerType(const BlockPointerType *T) {
  Writer.AddTypeRef(T->getPointeeType(), Record);
  Code = TYPE_BLOCK_POINTER;
}

void ASTTypeWriter::VisitLValueReferenceType(const LValueReferenceType *T) {
  Writer.AddTypeRef(T->getPointeeTypeAsWritten(), Record);
  Record.push_back(T->isSpelledAsLValue());
  Code = TYPE_LVALUE_REFERENCE;
}

void ASTTypeWriter::VisitRValueReferenceType(const RValueReferenceType *T) {
  Writer.AddTypeRef(T->getPointeeTypeAsWritten(), Record);
  Code = TYPE_RVALUE_REFERENCE;
}

void ASTTypeWriter::VisitMemberPointerType(const MemberPointerType *T) {
  Writer.AddTypeRef(T->getPointeeType(), Record);
  Writer.AddTypeRef(QualType(T->getClass(), 0), Record);
  Code = TYPE_MEMBER_POINTER;
}

void ASTTypeWriter::VisitArrayType(const ArrayType *T) {
  Writer.AddTypeRef(T->getElementType(), Record);
  Record.push_back(T->getSizeModifier()); // FIXME: stable values
  Record.push_back(T->getIndexTypeCVRQualifiers()); // FIXME: stable values
}

void ASTTypeWriter::VisitConstantArrayType(const ConstantArrayType *T) {
  VisitArrayType(T);
  Writer.AddAPInt(T->getSize(), Record);
  Code = TYPE_CONSTANT_ARRAY;
}

void ASTTypeWriter::VisitIncompleteArrayType(const IncompleteArrayType *T) {
  VisitArrayType(T);
  Code = TYPE_INCOMPLETE_ARRAY;
}

void ASTTypeWriter::VisitVariableArrayType(const VariableArrayType *T) {
  VisitArrayType(T);
  Writer.AddSourceLocation(T->getLBracketLoc(), Record);
  Writer.AddSourceLocation(T->getRBracketLoc(), Record);
  Writer.AddStmt(T->getSizeExpr());
  Code = TYPE_VARIABLE_ARRAY;
}

void ASTTypeWriter::VisitVectorType(const VectorType *T) {
  Writer.AddTypeRef(T->getElementType(), Record);
  Record.push_back(T->getNumElements());
  Record.push_back(T->getVectorKind());
  Code = TYPE_VECTOR;
}

void ASTTypeWriter::VisitExtVectorType(const ExtVectorType *T) {
  VisitVectorType(T);
  Code = TYPE_EXT_VECTOR;
}

void ASTTypeWriter::VisitFunctionType(const FunctionType *T) {
  Writer.AddTypeRef(T->getReturnType(), Record);
  FunctionType::ExtInfo C = T->getExtInfo();
  Record.push_back(C.getNoReturn());
  Record.push_back(C.getHasRegParm());
  Record.push_back(C.getRegParm());
  // FIXME: need to stabilize encoding of calling convention...
  Record.push_back(C.getCC());
  Record.push_back(C.getProducesResult());
}

void ASTTypeWriter::VisitFunctionNoProtoType(const FunctionNoProtoType *T) {
  VisitFunctionType(T);
  Code = TYPE_FUNCTION_NO_PROTO;
}

static void addExceptionSpec(ASTWriter &Writer, const FunctionProtoType *T,
                             ASTWriter::RecordDataImpl &Record) {
  Record.push_back(T->getExceptionSpecType());
  if (T->getExceptionSpecType() == EST_Dynamic) {
    Record.push_back(T->getNumExceptions());
    for (unsigned I = 0, N = T->getNumExceptions(); I != N; ++I)
      Writer.AddTypeRef(T->getExceptionType(I), Record);
  } else if (T->getExceptionSpecType() == EST_ComputedNoexcept) {
    Writer.AddStmt(T->getNoexceptExpr());
  } else if (T->getExceptionSpecType() == EST_Uninstantiated) {
    Writer.AddDeclRef(T->getExceptionSpecDecl(), Record);
    Writer.AddDeclRef(T->getExceptionSpecTemplate(), Record);
  } else if (T->getExceptionSpecType() == EST_Unevaluated) {
    Writer.AddDeclRef(T->getExceptionSpecDecl(), Record);
  }
}

void ASTTypeWriter::VisitFunctionProtoType(const FunctionProtoType *T) {
  VisitFunctionType(T);
  Record.push_back(T->getNumParams());
  for (unsigned I = 0, N = T->getNumParams(); I != N; ++I)
    Writer.AddTypeRef(T->getParamType(I), Record);
  Record.push_back(T->isVariadic());
  Record.push_back(T->hasTrailingReturn());
  Record.push_back(T->getTypeQuals());
  Record.push_back(static_cast<unsigned>(T->getRefQualifier()));
  addExceptionSpec(Writer, T, Record);
  Code = TYPE_FUNCTION_PROTO;
}

void ASTTypeWriter::VisitUnresolvedUsingType(const UnresolvedUsingType *T) {
  Writer.AddDeclRef(T->getDecl(), Record);
  Code = TYPE_UNRESOLVED_USING;
}

void ASTTypeWriter::VisitTypedefType(const TypedefType *T) {
  Writer.AddDeclRef(T->getDecl(), Record);
  assert(!T->isCanonicalUnqualified() && "Invalid typedef ?");
  Writer.AddTypeRef(T->getCanonicalTypeInternal(), Record);
  Code = TYPE_TYPEDEF;
}

void ASTTypeWriter::VisitTypeOfExprType(const TypeOfExprType *T) {
  Writer.AddStmt(T->getUnderlyingExpr());
  Code = TYPE_TYPEOF_EXPR;
}

void ASTTypeWriter::VisitTypeOfType(const TypeOfType *T) {
  Writer.AddTypeRef(T->getUnderlyingType(), Record);
  Code = TYPE_TYPEOF;
}

void ASTTypeWriter::VisitDecltypeType(const DecltypeType *T) {
  Writer.AddTypeRef(T->getUnderlyingType(), Record);
  Writer.AddStmt(T->getUnderlyingExpr());
  Code = TYPE_DECLTYPE;
}

void ASTTypeWriter::VisitUnaryTransformType(const UnaryTransformType *T) {
  Writer.AddTypeRef(T->getBaseType(), Record);
  Writer.AddTypeRef(T->getUnderlyingType(), Record);
  Record.push_back(T->getUTTKind());
  Code = TYPE_UNARY_TRANSFORM;
}

void ASTTypeWriter::VisitAutoType(const AutoType *T) {
  Writer.AddTypeRef(T->getDeducedType(), Record);
  Record.push_back(T->isDecltypeAuto());
  if (T->getDeducedType().isNull())
    Record.push_back(T->isDependentType());
  Code = TYPE_AUTO;
}

void ASTTypeWriter::VisitTagType(const TagType *T) {
  Record.push_back(T->isDependentType());
  Writer.AddDeclRef(T->getDecl()->getCanonicalDecl(), Record);
  assert(!T->isBeingDefined() &&
         "Cannot serialize in the middle of a type definition");
}

void ASTTypeWriter::VisitRecordType(const RecordType *T) {
  VisitTagType(T);
  Code = TYPE_RECORD;
}

void ASTTypeWriter::VisitEnumType(const EnumType *T) {
  VisitTagType(T);
  Code = TYPE_ENUM;
}

void ASTTypeWriter::VisitAttributedType(const AttributedType *T) {
  Writer.AddTypeRef(T->getModifiedType(), Record);
  Writer.AddTypeRef(T->getEquivalentType(), Record);
  Record.push_back(T->getAttrKind());
  Code = TYPE_ATTRIBUTED;
}

void
ASTTypeWriter::VisitSubstTemplateTypeParmType(
                                        const SubstTemplateTypeParmType *T) {
  Writer.AddTypeRef(QualType(T->getReplacedParameter(), 0), Record);
  Writer.AddTypeRef(T->getReplacementType(), Record);
  Code = TYPE_SUBST_TEMPLATE_TYPE_PARM;
}

void
ASTTypeWriter::VisitSubstTemplateTypeParmPackType(
                                      const SubstTemplateTypeParmPackType *T) {
  Writer.AddTypeRef(QualType(T->getReplacedParameter(), 0), Record);
  Writer.AddTemplateArgument(T->getArgumentPack(), Record);
  Code = TYPE_SUBST_TEMPLATE_TYPE_PARM_PACK;
}

void
ASTTypeWriter::VisitTemplateSpecializationType(
                                       const TemplateSpecializationType *T) {
  Record.push_back(T->isDependentType());
  Writer.AddTemplateName(T->getTemplateName(), Record);
  Record.push_back(T->getNumArgs());
  for (TemplateSpecializationType::iterator ArgI = T->begin(), ArgE = T->end();
         ArgI != ArgE; ++ArgI)
    Writer.AddTemplateArgument(*ArgI, Record);
  Writer.AddTypeRef(T->isTypeAlias() ? T->getAliasedType() :
                    T->isCanonicalUnqualified() ? QualType()
                                                : T->getCanonicalTypeInternal(),
                    Record);
  Code = TYPE_TEMPLATE_SPECIALIZATION;
}

void
ASTTypeWriter::VisitDependentSizedArrayType(const DependentSizedArrayType *T) {
  VisitArrayType(T);
  Writer.AddStmt(T->getSizeExpr());
  Writer.AddSourceRange(T->getBracketsRange(), Record);
  Code = TYPE_DEPENDENT_SIZED_ARRAY;
}

void
ASTTypeWriter::VisitDependentSizedExtVectorType(
                                        const DependentSizedExtVectorType *T) {
  // FIXME: Serialize this type (C++ only)
  llvm_unreachable("Cannot serialize dependent sized extended vector types");
}

void
ASTTypeWriter::VisitTemplateTypeParmType(const TemplateTypeParmType *T) {
  Record.push_back(T->getDepth());
  Record.push_back(T->getIndex());
  Record.push_back(T->isParameterPack());
  Writer.AddDeclRef(T->getDecl(), Record);
  Code = TYPE_TEMPLATE_TYPE_PARM;
}

void
ASTTypeWriter::VisitDependentNameType(const DependentNameType *T) {
  Record.push_back(T->getKeyword());
  Writer.AddNestedNameSpecifier(T->getQualifier(), Record);
  Writer.AddIdentifierRef(T->getIdentifier(), Record);
  Writer.AddTypeRef(T->isCanonicalUnqualified() ? QualType()
                                                : T->getCanonicalTypeInternal(),
                    Record);
  Code = TYPE_DEPENDENT_NAME;
}

void
ASTTypeWriter::VisitDependentTemplateSpecializationType(
                                const DependentTemplateSpecializationType *T) {
  Record.push_back(T->getKeyword());
  Writer.AddNestedNameSpecifier(T->getQualifier(), Record);
  Writer.AddIdentifierRef(T->getIdentifier(), Record);
  Record.push_back(T->getNumArgs());
  for (DependentTemplateSpecializationType::iterator
         I = T->begin(), E = T->end(); I != E; ++I)
    Writer.AddTemplateArgument(*I, Record);
  Code = TYPE_DEPENDENT_TEMPLATE_SPECIALIZATION;
}

void ASTTypeWriter::VisitPackExpansionType(const PackExpansionType *T) {
  Writer.AddTypeRef(T->getPattern(), Record);
  if (Optional<unsigned> NumExpansions = T->getNumExpansions())
    Record.push_back(*NumExpansions + 1);
  else
    Record.push_back(0);
  Code = TYPE_PACK_EXPANSION;
}

void ASTTypeWriter::VisitParenType(const ParenType *T) {
  Writer.AddTypeRef(T->getInnerType(), Record);
  Code = TYPE_PAREN;
}

void ASTTypeWriter::VisitElaboratedType(const ElaboratedType *T) {
  Record.push_back(T->getKeyword());
  Writer.AddNestedNameSpecifier(T->getQualifier(), Record);
  Writer.AddTypeRef(T->getNamedType(), Record);
  Code = TYPE_ELABORATED;
}

void ASTTypeWriter::VisitInjectedClassNameType(const InjectedClassNameType *T) {
  Writer.AddDeclRef(T->getDecl()->getCanonicalDecl(), Record);
  Writer.AddTypeRef(T->getInjectedSpecializationType(), Record);
  Code = TYPE_INJECTED_CLASS_NAME;
}

void ASTTypeWriter::VisitObjCInterfaceType(const ObjCInterfaceType *T) {
  Writer.AddDeclRef(T->getDecl()->getCanonicalDecl(), Record);
  Code = TYPE_OBJC_INTERFACE;
}

void ASTTypeWriter::VisitObjCObjectType(const ObjCObjectType *T) {
  Writer.AddTypeRef(T->getBaseType(), Record);
  Record.push_back(T->getNumProtocols());
  for (const auto *I : T->quals())
    Writer.AddDeclRef(I, Record);
  Code = TYPE_OBJC_OBJECT;
}

void
ASTTypeWriter::VisitObjCObjectPointerType(const ObjCObjectPointerType *T) {
  Writer.AddTypeRef(T->getPointeeType(), Record);
  Code = TYPE_OBJC_OBJECT_POINTER;
}

void
ASTTypeWriter::VisitAtomicType(const AtomicType *T) {
  Writer.AddTypeRef(T->getValueType(), Record);
  Code = TYPE_ATOMIC;
}

namespace {

class TypeLocWriter : public TypeLocVisitor<TypeLocWriter> {
  ASTWriter &Writer;
  ASTWriter::RecordDataImpl &Record;

public:
  TypeLocWriter(ASTWriter &Writer, ASTWriter::RecordDataImpl &Record)
    : Writer(Writer), Record(Record) { }

#define ABSTRACT_TYPELOC(CLASS, PARENT)
#define TYPELOC(CLASS, PARENT) \
    void Visit##CLASS##TypeLoc(CLASS##TypeLoc TyLoc);
#include "clang/AST/TypeLocNodes.def"

  void VisitArrayTypeLoc(ArrayTypeLoc TyLoc);
  void VisitFunctionTypeLoc(FunctionTypeLoc TyLoc);
};

}

void TypeLocWriter::VisitQualifiedTypeLoc(QualifiedTypeLoc TL) {
  // nothing to do
}
void TypeLocWriter::VisitBuiltinTypeLoc(BuiltinTypeLoc TL) {
  Writer.AddSourceLocation(TL.getBuiltinLoc(), Record);
  if (TL.needsExtraLocalData()) {
    Record.push_back(TL.getWrittenTypeSpec());
    Record.push_back(TL.getWrittenSignSpec());
    Record.push_back(TL.getWrittenWidthSpec());
    Record.push_back(TL.hasModeAttr());
  }
}
void TypeLocWriter::VisitComplexTypeLoc(ComplexTypeLoc TL) {
  Writer.AddSourceLocation(TL.getNameLoc(), Record);
}
void TypeLocWriter::VisitPointerTypeLoc(PointerTypeLoc TL) {
  Writer.AddSourceLocation(TL.getStarLoc(), Record);
}
void TypeLocWriter::VisitDecayedTypeLoc(DecayedTypeLoc TL) {
  // nothing to do
}
void TypeLocWriter::VisitAdjustedTypeLoc(AdjustedTypeLoc TL) {
  // nothing to do
}
void TypeLocWriter::VisitBlockPointerTypeLoc(BlockPointerTypeLoc TL) {
  Writer.AddSourceLocation(TL.getCaretLoc(), Record);
}
void TypeLocWriter::VisitLValueReferenceTypeLoc(LValueReferenceTypeLoc TL) {
  Writer.AddSourceLocation(TL.getAmpLoc(), Record);
}
void TypeLocWriter::VisitRValueReferenceTypeLoc(RValueReferenceTypeLoc TL) {
  Writer.AddSourceLocation(TL.getAmpAmpLoc(), Record);
}
void TypeLocWriter::VisitMemberPointerTypeLoc(MemberPointerTypeLoc TL) {
  Writer.AddSourceLocation(TL.getStarLoc(), Record);
  Writer.AddTypeSourceInfo(TL.getClassTInfo(), Record);
}
void TypeLocWriter::VisitArrayTypeLoc(ArrayTypeLoc TL) {
  Writer.AddSourceLocation(TL.getLBracketLoc(), Record);
  Writer.AddSourceLocation(TL.getRBracketLoc(), Record);
  Record.push_back(TL.getSizeExpr() ? 1 : 0);
  if (TL.getSizeExpr())
    Writer.AddStmt(TL.getSizeExpr());
}
void TypeLocWriter::VisitConstantArrayTypeLoc(ConstantArrayTypeLoc TL) {
  VisitArrayTypeLoc(TL);
}
void TypeLocWriter::VisitIncompleteArrayTypeLoc(IncompleteArrayTypeLoc TL) {
  VisitArrayTypeLoc(TL);
}
void TypeLocWriter::VisitVariableArrayTypeLoc(VariableArrayTypeLoc TL) {
  VisitArrayTypeLoc(TL);
}
void TypeLocWriter::VisitDependentSizedArrayTypeLoc(
                                            DependentSizedArrayTypeLoc TL) {
  VisitArrayTypeLoc(TL);
}
void TypeLocWriter::VisitDependentSizedExtVectorTypeLoc(
                                        DependentSizedExtVectorTypeLoc TL) {
  Writer.AddSourceLocation(TL.getNameLoc(), Record);
}
void TypeLocWriter::VisitVectorTypeLoc(VectorTypeLoc TL) {
  Writer.AddSourceLocation(TL.getNameLoc(), Record);
}
void TypeLocWriter::VisitExtVectorTypeLoc(ExtVectorTypeLoc TL) {
  Writer.AddSourceLocation(TL.getNameLoc(), Record);
}
void TypeLocWriter::VisitFunctionTypeLoc(FunctionTypeLoc TL) {
  Writer.AddSourceLocation(TL.getLocalRangeBegin(), Record);
  Writer.AddSourceLocation(TL.getLParenLoc(), Record);
  Writer.AddSourceLocation(TL.getRParenLoc(), Record);
  Writer.AddSourceLocation(TL.getLocalRangeEnd(), Record);
  for (unsigned i = 0, e = TL.getNumParams(); i != e; ++i)
    Writer.AddDeclRef(TL.getParam(i), Record);
}
void TypeLocWriter::VisitFunctionProtoTypeLoc(FunctionProtoTypeLoc TL) {
  VisitFunctionTypeLoc(TL);
}
void TypeLocWriter::VisitFunctionNoProtoTypeLoc(FunctionNoProtoTypeLoc TL) {
  VisitFunctionTypeLoc(TL);
}
void TypeLocWriter::VisitUnresolvedUsingTypeLoc(UnresolvedUsingTypeLoc TL) {
  Writer.AddSourceLocation(TL.getNameLoc(), Record);
}
void TypeLocWriter::VisitTypedefTypeLoc(TypedefTypeLoc TL) {
  Writer.AddSourceLocation(TL.getNameLoc(), Record);
}
void TypeLocWriter::VisitTypeOfExprTypeLoc(TypeOfExprTypeLoc TL) {
  Writer.AddSourceLocation(TL.getTypeofLoc(), Record);
  Writer.AddSourceLocation(TL.getLParenLoc(), Record);
  Writer.AddSourceLocation(TL.getRParenLoc(), Record);
}
void TypeLocWriter::VisitTypeOfTypeLoc(TypeOfTypeLoc TL) {
  Writer.AddSourceLocation(TL.getTypeofLoc(), Record);
  Writer.AddSourceLocation(TL.getLParenLoc(), Record);
  Writer.AddSourceLocation(TL.getRParenLoc(), Record);
  Writer.AddTypeSourceInfo(TL.getUnderlyingTInfo(), Record);
}
void TypeLocWriter::VisitDecltypeTypeLoc(DecltypeTypeLoc TL) {
  Writer.AddSourceLocation(TL.getNameLoc(), Record);
}
void TypeLocWriter::VisitUnaryTransformTypeLoc(UnaryTransformTypeLoc TL) {
  Writer.AddSourceLocation(TL.getKWLoc(), Record);
  Writer.AddSourceLocation(TL.getLParenLoc(), Record);
  Writer.AddSourceLocation(TL.getRParenLoc(), Record);
  Writer.AddTypeSourceInfo(TL.getUnderlyingTInfo(), Record);
}
void TypeLocWriter::VisitAutoTypeLoc(AutoTypeLoc TL) {
  Writer.AddSourceLocation(TL.getNameLoc(), Record);
}
void TypeLocWriter::VisitRecordTypeLoc(RecordTypeLoc TL) {
  Writer.AddSourceLocation(TL.getNameLoc(), Record);
}
void TypeLocWriter::VisitEnumTypeLoc(EnumTypeLoc TL) {
  Writer.AddSourceLocation(TL.getNameLoc(), Record);
}
void TypeLocWriter::VisitAttributedTypeLoc(AttributedTypeLoc TL) {
  Writer.AddSourceLocation(TL.getAttrNameLoc(), Record);
  if (TL.hasAttrOperand()) {
    SourceRange range = TL.getAttrOperandParensRange();
    Writer.AddSourceLocation(range.getBegin(), Record);
    Writer.AddSourceLocation(range.getEnd(), Record);
  }
  if (TL.hasAttrExprOperand()) {
    Expr *operand = TL.getAttrExprOperand();
    Record.push_back(operand ? 1 : 0);
    if (operand) Writer.AddStmt(operand);
  } else if (TL.hasAttrEnumOperand()) {
    Writer.AddSourceLocation(TL.getAttrEnumOperandLoc(), Record);
  }
}
void TypeLocWriter::VisitTemplateTypeParmTypeLoc(TemplateTypeParmTypeLoc TL) {
  Writer.AddSourceLocation(TL.getNameLoc(), Record);
}
void TypeLocWriter::VisitSubstTemplateTypeParmTypeLoc(
                                            SubstTemplateTypeParmTypeLoc TL) {
  Writer.AddSourceLocation(TL.getNameLoc(), Record);
}
void TypeLocWriter::VisitSubstTemplateTypeParmPackTypeLoc(
                                          SubstTemplateTypeParmPackTypeLoc TL) {
  Writer.AddSourceLocation(TL.getNameLoc(), Record);
}
void TypeLocWriter::VisitTemplateSpecializationTypeLoc(
                                           TemplateSpecializationTypeLoc TL) {
  Writer.AddSourceLocation(TL.getTemplateKeywordLoc(), Record);
  Writer.AddSourceLocation(TL.getTemplateNameLoc(), Record);
  Writer.AddSourceLocation(TL.getLAngleLoc(), Record);
  Writer.AddSourceLocation(TL.getRAngleLoc(), Record);
  for (unsigned i = 0, e = TL.getNumArgs(); i != e; ++i)
    Writer.AddTemplateArgumentLocInfo(TL.getArgLoc(i).getArgument().getKind(),
                                      TL.getArgLoc(i).getLocInfo(), Record);
}
void TypeLocWriter::VisitParenTypeLoc(ParenTypeLoc TL) {
  Writer.AddSourceLocation(TL.getLParenLoc(), Record);
  Writer.AddSourceLocation(TL.getRParenLoc(), Record);
}
void TypeLocWriter::VisitElaboratedTypeLoc(ElaboratedTypeLoc TL) {
  Writer.AddSourceLocation(TL.getElaboratedKeywordLoc(), Record);
  Writer.AddNestedNameSpecifierLoc(TL.getQualifierLoc(), Record);
}
void TypeLocWriter::VisitInjectedClassNameTypeLoc(InjectedClassNameTypeLoc TL) {
  Writer.AddSourceLocation(TL.getNameLoc(), Record);
}
void TypeLocWriter::VisitDependentNameTypeLoc(DependentNameTypeLoc TL) {
  Writer.AddSourceLocation(TL.getElaboratedKeywordLoc(), Record);
  Writer.AddNestedNameSpecifierLoc(TL.getQualifierLoc(), Record);
  Writer.AddSourceLocation(TL.getNameLoc(), Record);
}
void TypeLocWriter::VisitDependentTemplateSpecializationTypeLoc(
       DependentTemplateSpecializationTypeLoc TL) {
  Writer.AddSourceLocation(TL.getElaboratedKeywordLoc(), Record);
  Writer.AddNestedNameSpecifierLoc(TL.getQualifierLoc(), Record);
  Writer.AddSourceLocation(TL.getTemplateKeywordLoc(), Record);
  Writer.AddSourceLocation(TL.getTemplateNameLoc(), Record);
  Writer.AddSourceLocation(TL.getLAngleLoc(), Record);
  Writer.AddSourceLocation(TL.getRAngleLoc(), Record);
  for (unsigned I = 0, E = TL.getNumArgs(); I != E; ++I)
    Writer.AddTemplateArgumentLocInfo(TL.getArgLoc(I).getArgument().getKind(),
                                      TL.getArgLoc(I).getLocInfo(), Record);
}
void TypeLocWriter::VisitPackExpansionTypeLoc(PackExpansionTypeLoc TL) {
  Writer.AddSourceLocation(TL.getEllipsisLoc(), Record);
}
void TypeLocWriter::VisitObjCInterfaceTypeLoc(ObjCInterfaceTypeLoc TL) {
  Writer.AddSourceLocation(TL.getNameLoc(), Record);
}
void TypeLocWriter::VisitObjCObjectTypeLoc(ObjCObjectTypeLoc TL) {
  Record.push_back(TL.hasBaseTypeAsWritten());
  Writer.AddSourceLocation(TL.getLAngleLoc(), Record);
  Writer.AddSourceLocation(TL.getRAngleLoc(), Record);
  for (unsigned i = 0, e = TL.getNumProtocols(); i != e; ++i)
    Writer.AddSourceLocation(TL.getProtocolLoc(i), Record);
}
void TypeLocWriter::VisitObjCObjectPointerTypeLoc(ObjCObjectPointerTypeLoc TL) {
  Writer.AddSourceLocation(TL.getStarLoc(), Record);
}
void TypeLocWriter::VisitAtomicTypeLoc(AtomicTypeLoc TL) {
  Writer.AddSourceLocation(TL.getKWLoc(), Record);
  Writer.AddSourceLocation(TL.getLParenLoc(), Record);
  Writer.AddSourceLocation(TL.getRParenLoc(), Record);
}

//===----------------------------------------------------------------------===//
// ASTWriter Implementation
//===----------------------------------------------------------------------===//

static void EmitBlockID(unsigned ID, const char *Name,
                        llvm::BitstreamWriter &Stream,
                        ASTWriter::RecordDataImpl &Record) {
  Record.clear();
  Record.push_back(ID);
  Stream.EmitRecord(llvm::bitc::BLOCKINFO_CODE_SETBID, Record);

  // Emit the block name if present.
  if (!Name || Name[0] == 0)
    return;
  Record.clear();
  while (*Name)
    Record.push_back(*Name++);
  Stream.EmitRecord(llvm::bitc::BLOCKINFO_CODE_BLOCKNAME, Record);
}

static void EmitRecordID(unsigned ID, const char *Name,
                         llvm::BitstreamWriter &Stream,
                         ASTWriter::RecordDataImpl &Record) {
  Record.clear();
  Record.push_back(ID);
  while (*Name)
    Record.push_back(*Name++);
  Stream.EmitRecord(llvm::bitc::BLOCKINFO_CODE_SETRECORDNAME, Record);
}

static void AddStmtsExprs(llvm::BitstreamWriter &Stream,
                          ASTWriter::RecordDataImpl &Record) {
#define RECORD(X) EmitRecordID(X, #X, Stream, Record)
  RECORD(STMT_STOP);
  RECORD(STMT_NULL_PTR);
  RECORD(STMT_NULL);
  RECORD(STMT_COMPOUND);
  RECORD(STMT_CASE);
  RECORD(STMT_DEFAULT);
  RECORD(STMT_LABEL);
  RECORD(STMT_ATTRIBUTED);
  RECORD(STMT_IF);
  RECORD(STMT_SWITCH);
  RECORD(STMT_WHILE);
  RECORD(STMT_DO);
  RECORD(STMT_FOR);
  RECORD(STMT_GOTO);
  RECORD(STMT_INDIRECT_GOTO);
  RECORD(STMT_CONTINUE);
  RECORD(STMT_BREAK);
  RECORD(STMT_RETURN);
  RECORD(STMT_DECL);
  RECORD(STMT_GCCASM);
  RECORD(STMT_MSASM);
  RECORD(EXPR_PREDEFINED);
  RECORD(EXPR_DECL_REF);
  RECORD(EXPR_INTEGER_LITERAL);
  RECORD(EXPR_FLOATING_LITERAL);
  RECORD(EXPR_IMAGINARY_LITERAL);
  RECORD(EXPR_STRING_LITERAL);
  RECORD(EXPR_CHARACTER_LITERAL);
  RECORD(EXPR_PAREN);
  RECORD(EXPR_UNARY_OPERATOR);
  RECORD(EXPR_SIZEOF_ALIGN_OF);
  RECORD(EXPR_ARRAY_SUBSCRIPT);
  RECORD(EXPR_CALL);
  RECORD(EXPR_MEMBER);
  RECORD(EXPR_BINARY_OPERATOR);
  RECORD(EXPR_COMPOUND_ASSIGN_OPERATOR);
  RECORD(EXPR_CONDITIONAL_OPERATOR);
  RECORD(EXPR_IMPLICIT_CAST);
  RECORD(EXPR_CSTYLE_CAST);
  RECORD(EXPR_COMPOUND_LITERAL);
  RECORD(EXPR_EXT_VECTOR_ELEMENT);
  RECORD(EXPR_INIT_LIST);
  RECORD(EXPR_DESIGNATED_INIT);
  RECORD(EXPR_IMPLICIT_VALUE_INIT);
  RECORD(EXPR_VA_ARG);
  RECORD(EXPR_ADDR_LABEL);
  RECORD(EXPR_STMT);
  RECORD(EXPR_CHOOSE);
  RECORD(EXPR_GNU_NULL);
  RECORD(EXPR_SHUFFLE_VECTOR);
  RECORD(EXPR_BLOCK);
  RECORD(EXPR_GENERIC_SELECTION);
  RECORD(EXPR_OBJC_STRING_LITERAL);
  RECORD(EXPR_OBJC_BOXED_EXPRESSION);
  RECORD(EXPR_OBJC_ARRAY_LITERAL);
  RECORD(EXPR_OBJC_DICTIONARY_LITERAL);
  RECORD(EXPR_OBJC_ENCODE);
  RECORD(EXPR_OBJC_SELECTOR_EXPR);
  RECORD(EXPR_OBJC_PROTOCOL_EXPR);
  RECORD(EXPR_OBJC_IVAR_REF_EXPR);
  RECORD(EXPR_OBJC_PROPERTY_REF_EXPR);
  RECORD(EXPR_OBJC_KVC_REF_EXPR);
  RECORD(EXPR_OBJC_MESSAGE_EXPR);
  RECORD(STMT_OBJC_FOR_COLLECTION);
  RECORD(STMT_OBJC_CATCH);
  RECORD(STMT_OBJC_FINALLY);
  RECORD(STMT_OBJC_AT_TRY);
  RECORD(STMT_OBJC_AT_SYNCHRONIZED);
  RECORD(STMT_OBJC_AT_THROW);
  RECORD(EXPR_OBJC_BOOL_LITERAL);
  RECORD(EXPR_CXX_OPERATOR_CALL);
  RECORD(EXPR_CXX_CONSTRUCT);
  RECORD(EXPR_CXX_STATIC_CAST);
  RECORD(EXPR_CXX_DYNAMIC_CAST);
  RECORD(EXPR_CXX_REINTERPRET_CAST);
  RECORD(EXPR_CXX_CONST_CAST);
  RECORD(EXPR_CXX_FUNCTIONAL_CAST);
  RECORD(EXPR_USER_DEFINED_LITERAL);
  RECORD(EXPR_CXX_STD_INITIALIZER_LIST);
  RECORD(EXPR_CXX_BOOL_LITERAL);
  RECORD(EXPR_CXX_NULL_PTR_LITERAL);
  RECORD(EXPR_CXX_TYPEID_EXPR);
  RECORD(EXPR_CXX_TYPEID_TYPE);
  RECORD(EXPR_CXX_UUIDOF_EXPR);
  RECORD(EXPR_CXX_UUIDOF_TYPE);
  RECORD(EXPR_CXX_THIS);
  RECORD(EXPR_CXX_THROW);
  RECORD(EXPR_CXX_DEFAULT_ARG);
  RECORD(EXPR_CXX_BIND_TEMPORARY);
  RECORD(EXPR_CXX_SCALAR_VALUE_INIT);
  RECORD(EXPR_CXX_NEW);
  RECORD(EXPR_CXX_DELETE);
  RECORD(EXPR_CXX_PSEUDO_DESTRUCTOR);
  RECORD(EXPR_EXPR_WITH_CLEANUPS);
  RECORD(EXPR_CXX_DEPENDENT_SCOPE_MEMBER);
  RECORD(EXPR_CXX_DEPENDENT_SCOPE_DECL_REF);
  RECORD(EXPR_CXX_UNRESOLVED_CONSTRUCT);
  RECORD(EXPR_CXX_UNRESOLVED_MEMBER);
  RECORD(EXPR_CXX_UNRESOLVED_LOOKUP);
  RECORD(EXPR_CXX_NOEXCEPT);
  RECORD(EXPR_OPAQUE_VALUE);
  RECORD(EXPR_PACK_EXPANSION);
  RECORD(EXPR_SIZEOF_PACK);
  RECORD(EXPR_SUBST_NON_TYPE_TEMPLATE_PARM_PACK);
  RECORD(EXPR_CUDA_KERNEL_CALL);
#undef RECORD
}

void ASTWriter::WriteBlockInfoBlock() {
  RecordData Record;
  Stream.EnterSubblock(llvm::bitc::BLOCKINFO_BLOCK_ID, 3);

#define BLOCK(X) EmitBlockID(X ## _ID, #X, Stream, Record)
#define RECORD(X) EmitRecordID(X, #X, Stream, Record)

  // Control Block.
  BLOCK(CONTROL_BLOCK);
  RECORD(METADATA);
  RECORD(MODULE_NAME);
  RECORD(MODULE_MAP_FILE);
  RECORD(IMPORTS);
  RECORD(LANGUAGE_OPTIONS);
  RECORD(TARGET_OPTIONS);
  RECORD(ORIGINAL_FILE);
  RECORD(ORIGINAL_PCH_DIR);
  RECORD(ORIGINAL_FILE_ID);
  RECORD(INPUT_FILE_OFFSETS);
  RECORD(DIAGNOSTIC_OPTIONS);
  RECORD(FILE_SYSTEM_OPTIONS);
  RECORD(HEADER_SEARCH_OPTIONS);
  RECORD(PREPROCESSOR_OPTIONS);

  BLOCK(INPUT_FILES_BLOCK);
  RECORD(INPUT_FILE);

  // AST Top-Level Block.
  BLOCK(AST_BLOCK);
  RECORD(TYPE_OFFSET);
  RECORD(DECL_OFFSET);
  RECORD(IDENTIFIER_OFFSET);
  RECORD(IDENTIFIER_TABLE);
  RECORD(EAGERLY_DESERIALIZED_DECLS);
  RECORD(SPECIAL_TYPES);
  RECORD(STATISTICS);
  RECORD(TENTATIVE_DEFINITIONS);
  RECORD(UNUSED_FILESCOPED_DECLS);
  RECORD(LOCALLY_SCOPED_EXTERN_C_DECLS);
  RECORD(SELECTOR_OFFSETS);
  RECORD(METHOD_POOL);
  RECORD(PP_COUNTER_VALUE);
  RECORD(SOURCE_LOCATION_OFFSETS);
  RECORD(SOURCE_LOCATION_PRELOADS);
  RECORD(EXT_VECTOR_DECLS);
  RECORD(PPD_ENTITIES_OFFSETS);
  RECORD(REFERENCED_SELECTOR_POOL);
  RECORD(TU_UPDATE_LEXICAL);
  RECORD(LOCAL_REDECLARATIONS_MAP);
  RECORD(SEMA_DECL_REFS);
  RECORD(WEAK_UNDECLARED_IDENTIFIERS);
  RECORD(PENDING_IMPLICIT_INSTANTIATIONS);
  RECORD(DECL_REPLACEMENTS);
  RECORD(UPDATE_VISIBLE);
  RECORD(DECL_UPDATE_OFFSETS);
  RECORD(DECL_UPDATES);
  RECORD(CXX_BASE_SPECIFIER_OFFSETS);
  RECORD(DIAG_PRAGMA_MAPPINGS);
  RECORD(CUDA_SPECIAL_DECL_REFS);
  RECORD(HEADER_SEARCH_TABLE);
  RECORD(FP_PRAGMA_OPTIONS);
  RECORD(OPENCL_EXTENSIONS);
  RECORD(DELEGATING_CTORS);
  RECORD(KNOWN_NAMESPACES);
  RECORD(UNDEFINED_BUT_USED);
  RECORD(MODULE_OFFSET_MAP);
  RECORD(SOURCE_MANAGER_LINE_TABLE);
  RECORD(OBJC_CATEGORIES_MAP);
  RECORD(FILE_SORTED_DECLS);
  RECORD(IMPORTED_MODULES);
  RECORD(MERGED_DECLARATIONS);
  RECORD(LOCAL_REDECLARATIONS);
  RECORD(OBJC_CATEGORIES);
  RECORD(MACRO_OFFSET);
  RECORD(MACRO_TABLE);
  RECORD(LATE_PARSED_TEMPLATE);
  RECORD(OPTIMIZE_PRAGMA_OPTIONS);

  // SourceManager Block.
  BLOCK(SOURCE_MANAGER_BLOCK);
  RECORD(SM_SLOC_FILE_ENTRY);
  RECORD(SM_SLOC_BUFFER_ENTRY);
  RECORD(SM_SLOC_BUFFER_BLOB);
  RECORD(SM_SLOC_EXPANSION_ENTRY);

  // Preprocessor Block.
  BLOCK(PREPROCESSOR_BLOCK);
  RECORD(PP_MACRO_OBJECT_LIKE);
  RECORD(PP_MACRO_FUNCTION_LIKE);
  RECORD(PP_TOKEN);

  // Decls and Types block.
  BLOCK(DECLTYPES_BLOCK);
  RECORD(TYPE_EXT_QUAL);
  RECORD(TYPE_COMPLEX);
  RECORD(TYPE_POINTER);
  RECORD(TYPE_BLOCK_POINTER);
  RECORD(TYPE_LVALUE_REFERENCE);
  RECORD(TYPE_RVALUE_REFERENCE);
  RECORD(TYPE_MEMBER_POINTER);
  RECORD(TYPE_CONSTANT_ARRAY);
  RECORD(TYPE_INCOMPLETE_ARRAY);
  RECORD(TYPE_VARIABLE_ARRAY);
  RECORD(TYPE_VECTOR);
  RECORD(TYPE_EXT_VECTOR);
  RECORD(TYPE_FUNCTION_PROTO);
  RECORD(TYPE_FUNCTION_NO_PROTO);
  RECORD(TYPE_TYPEDEF);
  RECORD(TYPE_TYPEOF_EXPR);
  RECORD(TYPE_TYPEOF);
  RECORD(TYPE_RECORD);
  RECORD(TYPE_ENUM);
  RECORD(TYPE_OBJC_INTERFACE);
  RECORD(TYPE_OBJC_OBJECT);
  RECORD(TYPE_OBJC_OBJECT_POINTER);
  RECORD(TYPE_DECLTYPE);
  RECORD(TYPE_ELABORATED);
  RECORD(TYPE_SUBST_TEMPLATE_TYPE_PARM);
  RECORD(TYPE_UNRESOLVED_USING);
  RECORD(TYPE_INJECTED_CLASS_NAME);
  RECORD(TYPE_OBJC_OBJECT);
  RECORD(TYPE_TEMPLATE_TYPE_PARM);
  RECORD(TYPE_TEMPLATE_SPECIALIZATION);
  RECORD(TYPE_DEPENDENT_NAME);
  RECORD(TYPE_DEPENDENT_TEMPLATE_SPECIALIZATION);
  RECORD(TYPE_DEPENDENT_SIZED_ARRAY);
  RECORD(TYPE_PAREN);
  RECORD(TYPE_PACK_EXPANSION);
  RECORD(TYPE_ATTRIBUTED);
  RECORD(TYPE_SUBST_TEMPLATE_TYPE_PARM_PACK);
  RECORD(TYPE_ATOMIC);
  RECORD(DECL_TYPEDEF);
  RECORD(DECL_ENUM);
  RECORD(DECL_RECORD);
  RECORD(DECL_ENUM_CONSTANT);
  RECORD(DECL_FUNCTION);
  RECORD(DECL_OBJC_METHOD);
  RECORD(DECL_OBJC_INTERFACE);
  RECORD(DECL_OBJC_PROTOCOL);
  RECORD(DECL_OBJC_IVAR);
  RECORD(DECL_OBJC_AT_DEFS_FIELD);
  RECORD(DECL_OBJC_CATEGORY);
  RECORD(DECL_OBJC_CATEGORY_IMPL);
  RECORD(DECL_OBJC_IMPLEMENTATION);
  RECORD(DECL_OBJC_COMPATIBLE_ALIAS);
  RECORD(DECL_OBJC_PROPERTY);
  RECORD(DECL_OBJC_PROPERTY_IMPL);
  RECORD(DECL_FIELD);
  RECORD(DECL_MS_PROPERTY);
  RECORD(DECL_VAR);
  RECORD(DECL_IMPLICIT_PARAM);
  RECORD(DECL_PARM_VAR);
  RECORD(DECL_FILE_SCOPE_ASM);
  RECORD(DECL_BLOCK);
  RECORD(DECL_CONTEXT_LEXICAL);
  RECORD(DECL_CONTEXT_VISIBLE);
  RECORD(DECL_NAMESPACE);
  RECORD(DECL_NAMESPACE_ALIAS);
  RECORD(DECL_USING);
  RECORD(DECL_USING_SHADOW);
  RECORD(DECL_USING_DIRECTIVE);
  RECORD(DECL_UNRESOLVED_USING_VALUE);
  RECORD(DECL_UNRESOLVED_USING_TYPENAME);
  RECORD(DECL_LINKAGE_SPEC);
  RECORD(DECL_CXX_RECORD);
  RECORD(DECL_CXX_METHOD);
  RECORD(DECL_CXX_CONSTRUCTOR);
  RECORD(DECL_CXX_DESTRUCTOR);
  RECORD(DECL_CXX_CONVERSION);
  RECORD(DECL_ACCESS_SPEC);
  RECORD(DECL_FRIEND);
  RECORD(DECL_FRIEND_TEMPLATE);
  RECORD(DECL_CLASS_TEMPLATE);
  RECORD(DECL_CLASS_TEMPLATE_SPECIALIZATION);
  RECORD(DECL_CLASS_TEMPLATE_PARTIAL_SPECIALIZATION);
  RECORD(DECL_VAR_TEMPLATE);
  RECORD(DECL_VAR_TEMPLATE_SPECIALIZATION);
  RECORD(DECL_VAR_TEMPLATE_PARTIAL_SPECIALIZATION);
  RECORD(DECL_FUNCTION_TEMPLATE);
  RECORD(DECL_TEMPLATE_TYPE_PARM);
  RECORD(DECL_NON_TYPE_TEMPLATE_PARM);
  RECORD(DECL_TEMPLATE_TEMPLATE_PARM);
  RECORD(DECL_STATIC_ASSERT);
  RECORD(DECL_CXX_BASE_SPECIFIERS);
  RECORD(DECL_INDIRECTFIELD);
  RECORD(DECL_EXPANDED_NON_TYPE_TEMPLATE_PARM_PACK);

  // Statements and Exprs can occur in the Decls and Types block.
  AddStmtsExprs(Stream, Record);

  BLOCK(PREPROCESSOR_DETAIL_BLOCK);
  RECORD(PPD_MACRO_EXPANSION);
  RECORD(PPD_MACRO_DEFINITION);
  RECORD(PPD_INCLUSION_DIRECTIVE);

#undef RECORD
#undef BLOCK
  Stream.ExitBlock();
}

/// \brief Adjusts the given filename to only write out the portion of the
/// filename that is not part of the system root directory.
///
/// \param Filename the file name to adjust.
///
/// \param isysroot When non-NULL, the PCH file is a relocatable PCH file and
/// the returned filename will be adjusted by this system root.
///
/// \returns either the original filename (if it needs no adjustment) or the
/// adjusted filename (which points into the @p Filename parameter).
static const char *
adjustFilenameForRelocatablePCH(const char *Filename, StringRef isysroot) {
  assert(Filename && "No file name to adjust?");

  if (isysroot.empty())
    return Filename;

  // Verify that the filename and the system root have the same prefix.
  unsigned Pos = 0;
  for (; Filename[Pos] && Pos < isysroot.size(); ++Pos)
    if (Filename[Pos] != isysroot[Pos])
      return Filename; // Prefixes don't match.

  // We hit the end of the filename before we hit the end of the system root.
  if (!Filename[Pos])
    return Filename;

  // If the file name has a '/' at the current position, skip over the '/'.
  // We distinguish sysroot-based includes from absolute includes by the
  // absence of '/' at the beginning of sysroot-based includes.
  if (Filename[Pos] == '/')
    ++Pos;

  return Filename + Pos;
}

/// \brief Write the control block.
void ASTWriter::WriteControlBlock(Preprocessor &PP, ASTContext &Context,
                                  StringRef isysroot,
                                  const std::string &OutputFile) {
  using namespace llvm;
  Stream.EnterSubblock(CONTROL_BLOCK_ID, 5);
  RecordData Record;

  // Metadata
  BitCodeAbbrev *MetadataAbbrev = new BitCodeAbbrev();
  MetadataAbbrev->Add(BitCodeAbbrevOp(METADATA));
  MetadataAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 16)); // Major
  MetadataAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 16)); // Minor
  MetadataAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 16)); // Clang maj.
  MetadataAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 16)); // Clang min.
  MetadataAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // Relocatable
  MetadataAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // Errors
  MetadataAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob)); // SVN branch/tag
  unsigned MetadataAbbrevCode = Stream.EmitAbbrev(MetadataAbbrev);
  Record.push_back(METADATA);
  Record.push_back(VERSION_MAJOR);
  Record.push_back(VERSION_MINOR);
  Record.push_back(CLANG_VERSION_MAJOR);
  Record.push_back(CLANG_VERSION_MINOR);
  Record.push_back(!isysroot.empty());
  Record.push_back(ASTHasCompilerErrors);
  Stream.EmitRecordWithBlob(MetadataAbbrevCode, Record,
                            getClangFullRepositoryVersion());

  // Module name
  if (WritingModule) {
    BitCodeAbbrev *Abbrev = new BitCodeAbbrev();
    Abbrev->Add(BitCodeAbbrevOp(MODULE_NAME));
    Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob)); // Name
    unsigned AbbrevCode = Stream.EmitAbbrev(Abbrev);
    RecordData Record;
    Record.push_back(MODULE_NAME);
    Stream.EmitRecordWithBlob(AbbrevCode, Record, WritingModule->Name);
  }

  // Module map file
  if (WritingModule) {
    BitCodeAbbrev *Abbrev = new BitCodeAbbrev();
    Abbrev->Add(BitCodeAbbrevOp(MODULE_MAP_FILE));
    Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob)); // Filename
    unsigned AbbrevCode = Stream.EmitAbbrev(Abbrev);

    assert(WritingModule->ModuleMap && "missing module map");
    SmallString<128> ModuleMap(WritingModule->ModuleMap->getName());
    llvm::sys::fs::make_absolute(ModuleMap);
    RecordData Record;
    Record.push_back(MODULE_MAP_FILE);
    Stream.EmitRecordWithBlob(AbbrevCode, Record, ModuleMap.str());
  }

  // Imports
  if (Chain) {
    serialization::ModuleManager &Mgr = Chain->getModuleManager();
    Record.clear();

    for (ModuleManager::ModuleIterator M = Mgr.begin(), MEnd = Mgr.end();
         M != MEnd; ++M) {
      // Skip modules that weren't directly imported.
      if (!(*M)->isDirectlyImported())
        continue;

      Record.push_back((unsigned)(*M)->Kind); // FIXME: Stable encoding
      AddSourceLocation((*M)->ImportLoc, Record);
      Record.push_back((*M)->File->getSize());
      Record.push_back((*M)->File->getModificationTime());
      const std::string &FileName = (*M)->FileName;
      Record.push_back(FileName.size());
      Record.append(FileName.begin(), FileName.end());
    }
    Stream.EmitRecord(IMPORTS, Record);
  }

  // Language options.
  Record.clear();
  const LangOptions &LangOpts = Context.getLangOpts();
#define LANGOPT(Name, Bits, Default, Description) \
  Record.push_back(LangOpts.Name);
#define ENUM_LANGOPT(Name, Type, Bits, Default, Description) \
  Record.push_back(static_cast<unsigned>(LangOpts.get##Name()));
#include "clang/Basic/LangOptions.def"
#define SANITIZER(NAME, ID) Record.push_back(LangOpts.Sanitize.ID);
#include "clang/Basic/Sanitizers.def"

  Record.push_back((unsigned) LangOpts.ObjCRuntime.getKind());
  AddVersionTuple(LangOpts.ObjCRuntime.getVersion(), Record);