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+//===- llvm/Support/YAMLTraits.h --------------------------------*- C++ -*-===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_YAMLTRAITS_H
+#define LLVM_SUPPORT_YAMLTRAITS_H
+
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/Twine.h"
+#include "llvm/Support/AlignOf.h"
+#include "llvm/Support/Allocator.h"
+#include "llvm/Support/Endian.h"
+#include "llvm/Support/Regex.h"
+#include "llvm/Support/SourceMgr.h"
+#include "llvm/Support/YAMLParser.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <cctype>
+#include <cstddef>
+#include <cstdint>
+#include <map>
+#include <memory>
+#include <new>
+#include <string>
+#include <system_error>
+#include <type_traits>
+#include <vector>
+
+namespace llvm {
+namespace yaml {
+
+struct EmptyContext {};
+
+/// This class should be specialized by any type that needs to be converted
+/// to/from a YAML mapping.  For example:
+///
+///     struct MappingTraits<MyStruct> {
+///       static void mapping(IO &io, MyStruct &s) {
+///         io.mapRequired("name", s.name);
+///         io.mapRequired("size", s.size);
+///         io.mapOptional("age",  s.age);
+///       }
+///     };
+template<class T>
+struct MappingTraits {
+  // Must provide:
+  // static void mapping(IO &io, T &fields);
+  // Optionally may provide:
+  // static StringRef validate(IO &io, T &fields);
+  //
+  // The optional flow flag will cause generated YAML to use a flow mapping
+  // (e.g. { a: 0, b: 1 }):
+  // static const bool flow = true;
+};
+
+/// This class is similar to MappingTraits<T> but allows you to pass in
+/// additional context for each map operation.  For example:
+///
+///     struct MappingContextTraits<MyStruct, MyContext> {
+///       static void mapping(IO &io, MyStruct &s, MyContext &c) {
+///         io.mapRequired("name", s.name);
+///         io.mapRequired("size", s.size);
+///         io.mapOptional("age",  s.age);
+///         ++c.TimesMapped;
+///       }
+///     };
+template <class T, class Context> struct MappingContextTraits {
+  // Must provide:
+  // static void mapping(IO &io, T &fields, Context &Ctx);
+  // Optionally may provide:
+  // static StringRef validate(IO &io, T &fields, Context &Ctx);
+  //
+  // The optional flow flag will cause generated YAML to use a flow mapping
+  // (e.g. { a: 0, b: 1 }):
+  // static const bool flow = true;
+};
+
+/// This class should be specialized by any integral type that converts
+/// to/from a YAML scalar where there is a one-to-one mapping between
+/// in-memory values and a string in YAML.  For example:
+///
+///     struct ScalarEnumerationTraits<Colors> {
+///         static void enumeration(IO &io, Colors &value) {
+///           io.enumCase(value, "red",   cRed);
+///           io.enumCase(value, "blue",  cBlue);
+///           io.enumCase(value, "green", cGreen);
+///         }
+///       };
+template<typename T>
+struct ScalarEnumerationTraits {
+  // Must provide:
+  // static void enumeration(IO &io, T &value);
+};
+
+/// This class should be specialized by any integer type that is a union
+/// of bit values and the YAML representation is a flow sequence of
+/// strings.  For example:
+///
+///      struct ScalarBitSetTraits<MyFlags> {
+///        static void bitset(IO &io, MyFlags &value) {
+///          io.bitSetCase(value, "big",   flagBig);
+///          io.bitSetCase(value, "flat",  flagFlat);
+///          io.bitSetCase(value, "round", flagRound);
+///        }
+///      };
+template<typename T>
+struct ScalarBitSetTraits {
+  // Must provide:
+  // static void bitset(IO &io, T &value);
+};
+
+/// Describe which type of quotes should be used when quoting is necessary.
+/// Some non-printable characters need to be double-quoted, while some others
+/// are fine with simple-quoting, and some don't need any quoting.
+enum class QuotingType { None, Single, Double };
+
+/// This class should be specialized by type that requires custom conversion
+/// to/from a yaml scalar.  For example:
+///
+///    template<>
+///    struct ScalarTraits<MyType> {
+///      static void output(const MyType &val, void*, llvm::raw_ostream &out) {
+///        // stream out custom formatting
+///        out << llvm::format("%x", val);
+///      }
+///      static StringRef input(StringRef scalar, void*, MyType &value) {
+///        // parse scalar and set `value`
+///        // return empty string on success, or error string
+///        return StringRef();
+///      }
+///      static QuotingType mustQuote(StringRef) { return QuotingType::Single; }
+///    };
+template<typename T>
+struct ScalarTraits {
+  // Must provide:
+  //
+  // Function to write the value as a string:
+  //static void output(const T &value, void *ctxt, llvm::raw_ostream &out);
+  //
+  // Function to convert a string to a value.  Returns the empty
+  // StringRef on success or an error string if string is malformed:
+  //static StringRef input(StringRef scalar, void *ctxt, T &value);
+  //
+  // Function to determine if the value should be quoted.
+  //static QuotingType mustQuote(StringRef);
+};
+
+/// This class should be specialized by type that requires custom conversion
+/// to/from a YAML literal block scalar. For example:
+///
+///    template <>
+///    struct BlockScalarTraits<MyType> {
+///      static void output(const MyType &Value, void*, llvm::raw_ostream &Out)
+///      {
+///        // stream out custom formatting
+///        Out << Val;
+///      }
+///      static StringRef input(StringRef Scalar, void*, MyType &Value) {
+///        // parse scalar and set `value`
+///        // return empty string on success, or error string
+///        return StringRef();
+///      }
+///    };
+template <typename T>
+struct BlockScalarTraits {
+  // Must provide:
+  //
+  // Function to write the value as a string:
+  // static void output(const T &Value, void *ctx, llvm::raw_ostream &Out);
+  //
+  // Function to convert a string to a value.  Returns the empty
+  // StringRef on success or an error string if string is malformed:
+  // static StringRef input(StringRef Scalar, void *ctxt, T &Value);
+};
+
+/// This class should be specialized by any type that needs to be converted
+/// to/from a YAML sequence.  For example:
+///
+///    template<>
+///    struct SequenceTraits<MyContainer> {
+///      static size_t size(IO &io, MyContainer &seq) {
+///        return seq.size();
+///      }
+///      static MyType& element(IO &, MyContainer &seq, size_t index) {
+///        if ( index >= seq.size() )
+///          seq.resize(index+1);
+///        return seq[index];
+///      }
+///    };
+template<typename T, typename EnableIf = void>
+struct SequenceTraits {
+  // Must provide:
+  // static size_t size(IO &io, T &seq);
+  // static T::value_type& element(IO &io, T &seq, size_t index);
+  //
+  // The following is option and will cause generated YAML to use
+  // a flow sequence (e.g. [a,b,c]).
+  // static const bool flow = true;
+};
+
+/// This class should be specialized by any type for which vectors of that
+/// type need to be converted to/from a YAML sequence.
+template<typename T, typename EnableIf = void>
+struct SequenceElementTraits {
+  // Must provide:
+  // static const bool flow;
+};
+
+/// This class should be specialized by any type that needs to be converted
+/// to/from a list of YAML documents.
+template<typename T>
+struct DocumentListTraits {
+  // Must provide:
+  // static size_t size(IO &io, T &seq);
+  // static T::value_type& element(IO &io, T &seq, size_t index);
+};
+
+/// This class should be specialized by any type that needs to be converted
+/// to/from a YAML mapping in the case where the names of the keys are not known
+/// in advance, e.g. a string map.
+template <typename T>
+struct CustomMappingTraits {
+  // static void inputOne(IO &io, StringRef key, T &elem);
+  // static void output(IO &io, T &elem);
+};
+
+// Only used for better diagnostics of missing traits
+template <typename T>
+struct MissingTrait;
+
+// Test if ScalarEnumerationTraits<T> is defined on type T.
+template <class T>
+struct has_ScalarEnumerationTraits
+{
+  using Signature_enumeration = void (*)(class IO&, T&);
+
+  template <typename U>
+  static char test(SameType<Signature_enumeration, &U::enumeration>*);
+
+  template <typename U>
+  static double test(...);
+
+public:
+  static bool const value =
+    (sizeof(test<ScalarEnumerationTraits<T>>(nullptr)) == 1);
+};
+
+// Test if ScalarBitSetTraits<T> is defined on type T.
+template <class T>
+struct has_ScalarBitSetTraits
+{
+  using Signature_bitset = void (*)(class IO&, T&);
+
+  template <typename U>
+  static char test(SameType<Signature_bitset, &U::bitset>*);
+
+  template <typename U>
+  static double test(...);
+
+public:
+  static bool const value = (sizeof(test<ScalarBitSetTraits<T>>(nullptr)) == 1);
+};
+
+// Test if ScalarTraits<T> is defined on type T.
+template <class T>
+struct has_ScalarTraits
+{
+  using Signature_input = StringRef (*)(StringRef, void*, T&);
+  using Signature_output = void (*)(const T&, void*, raw_ostream&);
+  using Signature_mustQuote = QuotingType (*)(StringRef);
+
+  template <typename U>
+  static char test(SameType<Signature_input, &U::input> *,
+                   SameType<Signature_output, &U::output> *,
+                   SameType<Signature_mustQuote, &U::mustQuote> *);
+
+  template <typename U>
+  static double test(...);
+
+public:
+  static bool const value =
+      (sizeof(test<ScalarTraits<T>>(nullptr, nullptr, nullptr)) == 1);
+};
+
+// Test if BlockScalarTraits<T> is defined on type T.
+template <class T>
+struct has_BlockScalarTraits
+{
+  using Signature_input = StringRef (*)(StringRef, void *, T &);
+  using Signature_output = void (*)(const T &, void *, raw_ostream &);
+
+  template <typename U>
+  static char test(SameType<Signature_input, &U::input> *,
+                   SameType<Signature_output, &U::output> *);
+
+  template <typename U>
+  static double test(...);
+
+public:
+  static bool const value =
+      (sizeof(test<BlockScalarTraits<T>>(nullptr, nullptr)) == 1);
+};
+
+// Test if MappingContextTraits<T> is defined on type T.
+template <class T, class Context> struct has_MappingTraits {
+  using Signature_mapping = void (*)(class IO &, T &, Context &);
+
+  template <typename U>
+  static char test(SameType<Signature_mapping, &U::mapping>*);
+
+  template <typename U>
+  static double test(...);
+
+public:
+  static bool const value =
+      (sizeof(test<MappingContextTraits<T, Context>>(nullptr)) == 1);
+};
+
+// Test if MappingTraits<T> is defined on type T.
+template <class T> struct has_MappingTraits<T, EmptyContext> {
+  using Signature_mapping = void (*)(class IO &, T &);
+
+  template <typename U>
+  static char test(SameType<Signature_mapping, &U::mapping> *);
+
+  template <typename U> static double test(...);
+
+public:
+  static bool const value = (sizeof(test<MappingTraits<T>>(nullptr)) == 1);
+};
+
+// Test if MappingContextTraits<T>::validate() is defined on type T.
+template <class T, class Context> struct has_MappingValidateTraits {
+  using Signature_validate = StringRef (*)(class IO &, T &, Context &);
+
+  template <typename U>
+  static char test(SameType<Signature_validate, &U::validate>*);
+
+  template <typename U>
+  static double test(...);
+
+public:
+  static bool const value =
+      (sizeof(test<MappingContextTraits<T, Context>>(nullptr)) == 1);
+};
+
+// Test if MappingTraits<T>::validate() is defined on type T.
+template <class T> struct has_MappingValidateTraits<T, EmptyContext> {
+  using Signature_validate = StringRef (*)(class IO &, T &);
+
+  template <typename U>
+  static char test(SameType<Signature_validate, &U::validate> *);
+
+  template <typename U> static double test(...);
+
+public:
+  static bool const value = (sizeof(test<MappingTraits<T>>(nullptr)) == 1);
+};
+
+// Test if SequenceTraits<T> is defined on type T.
+template <class T>
+struct has_SequenceMethodTraits
+{
+  using Signature_size = size_t (*)(class IO&, T&);
+
+  template <typename U>
+  static char test(SameType<Signature_size, &U::size>*);
+
+  template <typename U>
+  static double test(...);
+
+public:
+  static bool const value =  (sizeof(test<SequenceTraits<T>>(nullptr)) == 1);
+};
+
+// Test if CustomMappingTraits<T> is defined on type T.
+template <class T>
+struct has_CustomMappingTraits
+{
+  using Signature_input = void (*)(IO &io, StringRef key, T &v);
+
+  template <typename U>
+  static char test(SameType<Signature_input, &U::inputOne>*);
+
+  template <typename U>
+  static double test(...);
+
+public:
+  static bool const value =
+      (sizeof(test<CustomMappingTraits<T>>(nullptr)) == 1);
+};
+
+// has_FlowTraits<int> will cause an error with some compilers because
+// it subclasses int.  Using this wrapper only instantiates the
+// real has_FlowTraits only if the template type is a class.
+template <typename T, bool Enabled = std::is_class<T>::value>
+class has_FlowTraits
+{
+public:
+   static const bool value = false;
+};
+
+// Some older gcc compilers don't support straight forward tests
+// for members, so test for ambiguity cause by the base and derived
+// classes both defining the member.
+template <class T>
+struct has_FlowTraits<T, true>
+{
+  struct Fallback { bool flow; };
+  struct Derived : T, Fallback { };
+
+  template<typename C>
+  static char (&f(SameType<bool Fallback::*, &C::flow>*))[1];
+
+  template<typename C>
+  static char (&f(...))[2];
+
+public:
+  static bool const value = sizeof(f<Derived>(nullptr)) == 2;
+};
+
+// Test if SequenceTraits<T> is defined on type T
+template<typename T>
+struct has_SequenceTraits : public std::integral_constant<bool,
+                                      has_SequenceMethodTraits<T>::value > { };
+
+// Test if DocumentListTraits<T> is defined on type T
+template <class T>
+struct has_DocumentListTraits
+{
+  using Signature_size = size_t (*)(class IO &, T &);
+
+  template <typename U>
+  static char test(SameType<Signature_size, &U::size>*);
+
+  template <typename U>
+  static double test(...);
+
+public:
+  static bool const value = (sizeof(test<DocumentListTraits<T>>(nullptr))==1);
+};
+
+inline bool isNumber(StringRef S) {
+  static const char OctalChars[] = "01234567";
+  if (S.startswith("0") &&
+      S.drop_front().find_first_not_of(OctalChars) == StringRef::npos)
+    return true;
+
+  if (S.startswith("0o") &&
+      S.drop_front(2).find_first_not_of(OctalChars) == StringRef::npos)
+    return true;
+
+  static const char HexChars[] = "0123456789abcdefABCDEF";
+  if (S.startswith("0x") &&
+      S.drop_front(2).find_first_not_of(HexChars) == StringRef::npos)
+    return true;
+
+  static const char DecChars[] = "0123456789";
+  if (S.find_first_not_of(DecChars) == StringRef::npos)
+    return true;
+
+  if (S.equals(".inf") || S.equals(".Inf") || S.equals(".INF"))
+    return true;
+
+  Regex FloatMatcher("^(\\.[0-9]+|[0-9]+(\\.[0-9]*)?)([eE][-+]?[0-9]+)?$");
+  if (FloatMatcher.match(S))
+    return true;
+
+  return false;
+}
+
+inline bool isNumeric(StringRef S) {
+  if ((S.front() == '-' || S.front() == '+') && isNumber(S.drop_front()))
+    return true;
+
+  if (isNumber(S))
+    return true;
+
+  if (S.equals(".nan") || S.equals(".NaN") || S.equals(".NAN"))
+    return true;
+
+  return false;
+}
+
+inline bool isNull(StringRef S) {
+  return S.equals("null") || S.equals("Null") || S.equals("NULL") ||
+         S.equals("~");
+}
+
+inline bool isBool(StringRef S) {
+  return S.equals("true") || S.equals("True") || S.equals("TRUE") ||
+         S.equals("false") || S.equals("False") || S.equals("FALSE");
+}
+
+// 5.1. Character Set
+// The allowed character range explicitly excludes the C0 control block #x0-#x1F
+// (except for TAB #x9, LF #xA, and CR #xD which are allowed), DEL #x7F, the C1
+// control block #x80-#x9F (except for NEL #x85 which is allowed), the surrogate
+// block #xD800-#xDFFF, #xFFFE, and #xFFFF.
+inline QuotingType needsQuotes(StringRef S) {
+  if (S.empty())
+    return QuotingType::Single;
+  if (isspace(S.front()) || isspace(S.back()))
+    return QuotingType::Single;
+  if (isNull(S))
+    return QuotingType::Single;
+  if (isBool(S))
+    return QuotingType::Single;
+  if (isNumeric(S))
+    return QuotingType::Single;
+
+  // 7.3.3 Plain Style
+  // Plain scalars must not begin with most indicators, as this would cause
+  // ambiguity with other YAML constructs.
+  static constexpr char Indicators[] = R"(-?:\,[]{}#&*!|>'"%@`)";
+  if (S.find_first_of(Indicators) == 0)
+    return QuotingType::Single;
+
+  QuotingType MaxQuotingNeeded = QuotingType::None;
+  for (unsigned char C : S) {
+    // Alphanum is safe.
+    if (isAlnum(C))
+      continue;
+
+    switch (C) {
+    // Safe scalar characters.
+    case '_':
+    case '-':
+    case '/':
+    case '^':
+    case '.':
+    case ',':
+    case ' ':
+    // TAB (0x9), LF (0xA), CR (0xD) and NEL (0x85) are allowed.
+    case 0x9:
+    case 0xA:
+    case 0xD:
+    case 0x85:
+      continue;
+    // DEL (0x7F) are excluded from the allowed character range.
+    case 0x7F:
+      return QuotingType::Double;
+    default: {
+      // C0 control block (0x0 - 0x1F) is excluded from the allowed character
+      // range.
+      if (C <= 0x1F)
+        return QuotingType::Double;
+
+      // Always double quote UTF-8.
+      if ((C & 0x80) != 0)
+        return QuotingType::Double;
+
+      // The character is not safe, at least simple quoting needed.
+      MaxQuotingNeeded = QuotingType::Single;
+    }
+    }
+  }
+
+  return MaxQuotingNeeded;
+}
+
+template <typename T, typename Context>
+struct missingTraits
+    : public std::integral_constant<bool,
+                                    !has_ScalarEnumerationTraits<T>::value &&
+                                        !has_ScalarBitSetTraits<T>::value &&
+                                        !has_ScalarTraits<T>::value &&
+                                        !has_BlockScalarTraits<T>::value &&
+                                        !has_MappingTraits<T, Context>::value &&
+                                        !has_SequenceTraits<T>::value &&
+                                        !has_CustomMappingTraits<T>::value &&
+                                        !has_DocumentListTraits<T>::value> {};
+
+template <typename T, typename Context>
+struct validatedMappingTraits
+    : public std::integral_constant<
+          bool, has_MappingTraits<T, Context>::value &&
+                    has_MappingValidateTraits<T, Context>::value> {};
+
+template <typename T, typename Context>
+struct unvalidatedMappingTraits
+    : public std::integral_constant<
+          bool, has_MappingTraits<T, Context>::value &&
+                    !has_MappingValidateTraits<T, Context>::value> {};
+
+// Base class for Input and Output.
+class IO {
+public:
+  IO(void *Ctxt = nullptr);
+  virtual ~IO();
+
+  virtual bool outputting() = 0;
+
+  virtual unsigned beginSequence() = 0;
+  virtual bool preflightElement(unsigned, void *&) = 0;
+  virtual void postflightElement(void*) = 0;
+  virtual void endSequence() = 0;
+  virtual bool canElideEmptySequence() = 0;
+
+  virtual unsigned beginFlowSequence() = 0;
+  virtual bool preflightFlowElement(unsigned, void *&) = 0;
+  virtual void postflightFlowElement(void*) = 0;
+  virtual void endFlowSequence() = 0;
+
+  virtual bool mapTag(StringRef Tag, bool Default=false) = 0;
+  virtual void beginMapping() = 0;
+  virtual void endMapping() = 0;
+  virtual bool preflightKey(const char*, bool, bool, bool &, void *&) = 0;
+  virtual void postflightKey(void*) = 0;
+  virtual std::vector<StringRef> keys() = 0;
+
+  virtual void beginFlowMapping() = 0;
+  virtual void endFlowMapping() = 0;
+
+  virtual void beginEnumScalar() = 0;
+  virtual bool matchEnumScalar(const char*, bool) = 0;
+  virtual bool matchEnumFallback() = 0;
+  virtual void endEnumScalar() = 0;
+
+  virtual bool beginBitSetScalar(bool &) = 0;
+  virtual bool bitSetMatch(const char*, bool) = 0;
+  virtual void endBitSetScalar() = 0;
+
+  virtual void scalarString(StringRef &, QuotingType) = 0;
+  virtual void blockScalarString(StringRef &) = 0;
+
+  virtual void setError(const Twine &) = 0;
+
+  template <typename T>
+  void enumCase(T &Val, const char* Str, const T ConstVal) {
+    if ( matchEnumScalar(Str, outputting() && Val == ConstVal) ) {
+      Val = ConstVal;
+    }
+  }
+
+  // allow anonymous enum values to be used with LLVM_YAML_STRONG_TYPEDEF
+  template <typename T>
+  void enumCase(T &Val, const char* Str, const uint32_t ConstVal) {
+    if ( matchEnumScalar(Str, outputting() && Val == static_cast<T>(ConstVal)) ) {
+      Val = ConstVal;
+    }
+  }
+
+  template <typename FBT, typename T>
+  void enumFallback(T &Val) {
+    if (matchEnumFallback()) {
+      EmptyContext Context;
+      // FIXME: Force integral conversion to allow strong typedefs to convert.
+      FBT Res = static_cast<typename FBT::BaseType>(Val);
+      yamlize(*this, Res, true, Context);
+      Val = static_cast<T>(static_cast<typename FBT::BaseType>(Res));
+    }
+  }
+
+  template <typename T>
+  void bitSetCase(T &Val, const char* Str, const T ConstVal) {
+    if ( bitSetMatch(Str, outputting() && (Val & ConstVal) == ConstVal) ) {
+      Val = static_cast<T>(Val | ConstVal);
+    }
+  }
+
+  // allow anonymous enum values to be used with LLVM_YAML_STRONG_TYPEDEF
+  template <typename T>
+  void bitSetCase(T &Val, const char* Str, const uint32_t ConstVal) {
+    if ( bitSetMatch(Str, outputting() && (Val & ConstVal) == ConstVal) ) {
+      Val = static_cast<T>(Val | ConstVal);
+    }
+  }
+
+  template <typename T>
+  void maskedBitSetCase(T &Val, const char *Str, T ConstVal, T Mask) {
+    if (bitSetMatch(Str, outputting() && (Val & Mask) == ConstVal))
+      Val = Val | ConstVal;
+  }
+
+  template <typename T>
+  void maskedBitSetCase(T &Val, const char *Str, uint32_t ConstVal,
+                        uint32_t Mask) {
+    if (bitSetMatch(Str, outputting() && (Val & Mask) == ConstVal))
+      Val = Val | ConstVal;
+  }
+
+  void *getContext();
+  void setContext(void *);
+
+  template <typename T> void mapRequired(const char *Key, T &Val) {
+    EmptyContext Ctx;
+    this->processKey(Key, Val, true, Ctx);
+  }
+
+  template <typename T, typename Context>
+  void mapRequired(const char *Key, T &Val, Context &Ctx) {
+    this->processKey(Key, Val, true, Ctx);
+  }
+
+  template <typename T> void mapOptional(const char *Key, T &Val) {
+    EmptyContext Ctx;
+    mapOptionalWithContext(Key, Val, Ctx);
+  }
+
+  template <typename T>
+  void mapOptional(const char *Key, T &Val, const T &Default) {
+    EmptyContext Ctx;
+    mapOptionalWithContext(Key, Val, Default, Ctx);
+  }
+
+  template <typename T, typename Context>
+  typename std::enable_if<has_SequenceTraits<T>::value, void>::type
+  mapOptionalWithContext(const char *Key, T &Val, Context &Ctx) {
+    // omit key/value instead of outputting empty sequence
+    if (this->canElideEmptySequence() && !(Val.begin() != Val.end()))
+      return;
+    this->processKey(Key, Val, false, Ctx);
+  }
+
+  template <typename T, typename Context>
+  void mapOptionalWithContext(const char *Key, Optional<T> &Val, Context &Ctx) {
+    this->processKeyWithDefault(Key, Val, Optional<T>(), /*Required=*/false,
+                                Ctx);
+  }
+
+  template <typename T, typename Context>
+  typename std::enable_if<!has_SequenceTraits<T>::value, void>::type
+  mapOptionalWithContext(const char *Key, T &Val, Context &Ctx) {
+    this->processKey(Key, Val, false, Ctx);
+  }
+
+  template <typename T, typename Context>
+  void mapOptionalWithContext(const char *Key, T &Val, const T &Default,
+                              Context &Ctx) {
+    this->processKeyWithDefault(Key, Val, Default, false, Ctx);
+  }
+
+private:
+  template <typename T, typename Context>
+  void processKeyWithDefault(const char *Key, Optional<T> &Val,
+                             const Optional<T> &DefaultValue, bool Required,
+                             Context &Ctx) {
+    assert(DefaultValue.hasValue() == false &&
+           "Optional<T> shouldn't have a value!");
+    void *SaveInfo;
+    bool UseDefault = true;
+    const bool sameAsDefault = outputting() && !Val.hasValue();
+    if (!outputting() && !Val.hasValue())
+      Val = T();
+    if (Val.hasValue() &&
+        this->preflightKey(Key, Required, sameAsDefault, UseDefault,
+                           SaveInfo)) {
+      yamlize(*this, Val.getValue(), Required, Ctx);
+      this->postflightKey(SaveInfo);
+    } else {
+      if (UseDefault)
+        Val = DefaultValue;
+    }
+  }
+
+  template <typename T, typename Context>
+  void processKeyWithDefault(const char *Key, T &Val, const T &DefaultValue,
+                             bool Required, Context &Ctx) {
+    void *SaveInfo;
+    bool UseDefault;
+    const bool sameAsDefault = outputting() && Val == DefaultValue;
+    if ( this->preflightKey(Key, Required, sameAsDefault, UseDefault,
+                                                                  SaveInfo) ) {
+      yamlize(*this, Val, Required, Ctx);
+      this->postflightKey(SaveInfo);
+    }
+    else {
+      if ( UseDefault )
+        Val = DefaultValue;
+    }
+  }
+
+  template <typename T, typename Context>
+  void processKey(const char *Key, T &Val, bool Required, Context &Ctx) {
+    void *SaveInfo;
+    bool UseDefault;
+    if ( this->preflightKey(Key, Required, false, UseDefault, SaveInfo) ) {
+      yamlize(*this, Val, Required, Ctx);
+      this->postflightKey(SaveInfo);
+    }
+  }
+
+private:
+  void *Ctxt;
+};
+
+namespace detail {
+
+template <typename T, typename Context>
+void doMapping(IO &io, T &Val, Context &Ctx) {
+  MappingContextTraits<T, Context>::mapping(io, Val, Ctx);
+}
+
+template <typename T> void doMapping(IO &io, T &Val, EmptyContext &Ctx) {
+  MappingTraits<T>::mapping(io, Val);
+}
+
+} // end namespace detail
+
+template <typename T>
+typename std::enable_if<has_ScalarEnumerationTraits<T>::value, void>::type
+yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
+  io.beginEnumScalar();
+  ScalarEnumerationTraits<T>::enumeration(io, Val);
+  io.endEnumScalar();
+}
+
+template <typename T>
+typename std::enable_if<has_ScalarBitSetTraits<T>::value, void>::type
+yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
+  bool DoClear;
+  if ( io.beginBitSetScalar(DoClear) ) {
+    if ( DoClear )
+      Val = static_cast<T>(0);
+    ScalarBitSetTraits<T>::bitset(io, Val);
+    io.endBitSetScalar();
+  }
+}
+
+template <typename T>
+typename std::enable_if<has_ScalarTraits<T>::value, void>::type
+yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
+  if ( io.outputting() ) {
+    std::string Storage;
+    raw_string_ostream Buffer(Storage);
+    ScalarTraits<T>::output(Val, io.getContext(), Buffer);
+    StringRef Str = Buffer.str();
+    io.scalarString(Str, ScalarTraits<T>::mustQuote(Str));
+  }
+  else {
+    StringRef Str;
+    io.scalarString(Str, ScalarTraits<T>::mustQuote(Str));
+    StringRef Result = ScalarTraits<T>::input(Str, io.getContext(), Val);
+    if ( !Result.empty() ) {
+      io.setError(Twine(Result));
+    }
+  }
+}
+
+template <typename T>
+typename std::enable_if<has_BlockScalarTraits<T>::value, void>::type
+yamlize(IO &YamlIO, T &Val, bool, EmptyContext &Ctx) {
+  if (YamlIO.outputting()) {
+    std::string Storage;
+    raw_string_ostream Buffer(Storage);
+    BlockScalarTraits<T>::output(Val, YamlIO.getContext(), Buffer);
+    StringRef Str = Buffer.str();
+    YamlIO.blockScalarString(Str);
+  } else {
+    StringRef Str;
+    YamlIO.blockScalarString(Str);
+    StringRef Result =
+        BlockScalarTraits<T>::input(Str, YamlIO.getContext(), Val);
+    if (!Result.empty())
+      YamlIO.setError(Twine(Result));
+  }
+}
+
+template <typename T, typename Context>
+typename std::enable_if<validatedMappingTraits<T, Context>::value, void>::type
+yamlize(IO &io, T &Val, bool, Context &Ctx) {
+  if (has_FlowTraits<MappingTraits<T>>::value)
+    io.beginFlowMapping();
+  else
+    io.beginMapping();
+  if (io.outputting()) {
+    StringRef Err = MappingTraits<T>::validate(io, Val);
+    if (!Err.empty()) {
+      errs() << Err << "\n";
+      assert(Err.empty() && "invalid struct trying to be written as yaml");
+    }
+  }
+  detail::doMapping(io, Val, Ctx);
+  if (!io.outputting()) {
+    StringRef Err = MappingTraits<T>::validate(io, Val);
+    if (!Err.empty())
+      io.setError(Err);
+  }
+  if (has_FlowTraits<MappingTraits<T>>::value)
+    io.endFlowMapping();
+  else
+    io.endMapping();
+}
+
+template <typename T, typename Context>
+typename std::enable_if<unvalidatedMappingTraits<T, Context>::value, void>::type
+yamlize(IO &io, T &Val, bool, Context &Ctx) {
+  if (has_FlowTraits<MappingTraits<T>>::value) {
+    io.beginFlowMapping();
+    detail::doMapping(io, Val, Ctx);
+    io.endFlowMapping();
+  } else {
+    io.beginMapping();
+    detail::doMapping(io, Val, Ctx);
+    io.endMapping();
+  }
+}
+
+template <typename T>
+typename std::enable_if<has_CustomMappingTraits<T>::value, void>::type
+yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
+  if ( io.outputting() ) {
+    io.beginMapping();
+    CustomMappingTraits<T>::output(io, Val);
+    io.endMapping();
+  } else {
+    io.beginMapping();
+    for (StringRef key : io.keys())
+      CustomMappingTraits<T>::inputOne(io, key, Val);
+    io.endMapping();
+  }
+}
+
+template <typename T>
+typename std::enable_if<missingTraits<T, EmptyContext>::value, void>::type
+yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
+  char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
+}
+
+template <typename T, typename Context>
+typename std::enable_if<has_SequenceTraits<T>::value, void>::type
+yamlize(IO &io, T &Seq, bool, Context &Ctx) {
+  if ( has_FlowTraits< SequenceTraits<T>>::value ) {
+    unsigned incnt = io.beginFlowSequence();
+    unsigned count = io.outputting() ? SequenceTraits<T>::size(io, Seq) : incnt;
+    for(unsigned i=0; i < count; ++i) {
+      void *SaveInfo;
+      if ( io.preflightFlowElement(i, SaveInfo) ) {
+        yamlize(io, SequenceTraits<T>::element(io, Seq, i), true, Ctx);
+        io.postflightFlowElement(SaveInfo);
+      }
+    }
+    io.endFlowSequence();
+  }
+  else {
+    unsigned incnt = io.beginSequence();
+    unsigned count = io.outputting() ? SequenceTraits<T>::size(io, Seq) : incnt;
+    for(unsigned i=0; i < count; ++i) {
+      void *SaveInfo;
+      if ( io.preflightElement(i, SaveInfo) ) {
+        yamlize(io, SequenceTraits<T>::element(io, Seq, i), true, Ctx);
+        io.postflightElement(SaveInfo);
+      }
+    }
+    io.endSequence();
+  }
+}
+
+template<>
+struct ScalarTraits<bool> {
+  static void output(const bool &, void* , raw_ostream &);
+  static StringRef input(StringRef, void *, bool &);
+  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
+};
+
+template<>
+struct ScalarTraits<StringRef> {
+  static void output(const StringRef &, void *, raw_ostream &);
+  static StringRef input(StringRef, void *, StringRef &);
+  static QuotingType mustQuote(StringRef S) { return needsQuotes(S); }
+};
+
+template<>
+struct ScalarTraits<std::string> {
+  static void output(const std::string &, void *, raw_ostream &);
+  static StringRef input(StringRef, void *, std::string &);
+  static QuotingType mustQuote(StringRef S) { return needsQuotes(S); }
+};
+
+template<>
+struct ScalarTraits<uint8_t> {
+  static void output(const uint8_t &, void *, raw_ostream &);
+  static StringRef input(StringRef, void *, uint8_t &);
+  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
+};
+
+template<>
+struct ScalarTraits<uint16_t> {
+  static void output(const uint16_t &, void *, raw_ostream &);
+  static StringRef input(StringRef, void *, uint16_t &);
+  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
+};
+
+template<>
+struct ScalarTraits<uint32_t> {
+  static void output(const uint32_t &, void *, raw_ostream &);
+  static StringRef input(StringRef, void *, uint32_t &);
+  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
+};
+
+template<>
+struct ScalarTraits<uint64_t> {
+  static void output(const uint64_t &, void *, raw_ostream &);
+  static StringRef input(StringRef, void *, uint64_t &);
+  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
+};
+
+template<>
+struct ScalarTraits<int8_t> {
+  static void output(const int8_t &, void *, raw_ostream &);
+  static StringRef input(StringRef, void *, int8_t &);
+  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
+};
+
+template<>
+struct ScalarTraits<int16_t> {
+  static void output(const int16_t &, void *, raw_ostream &);
+  static StringRef input(StringRef, void *, int16_t &);
+  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
+};
+
+template<>
+struct ScalarTraits<int32_t> {
+  static void output(const int32_t &, void *, raw_ostream &);
+  static StringRef input(StringRef, void *, int32_t &);
+  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
+};
+
+template<>
+struct ScalarTraits<int64_t> {
+  static void output(const int64_t &, void *, raw_ostream &);
+  static StringRef input(StringRef, void *, int64_t &);
+  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
+};
+
+template<>
+struct ScalarTraits<float> {
+  static void output(const float &, void *, raw_ostream &);
+  static StringRef input(StringRef, void *, float &);
+  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
+};
+
+template<>
+struct ScalarTraits<double> {
+  static void output(const double &, void *, raw_ostream &);
+  static StringRef input(StringRef, void *, double &);
+  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
+};
+
+// For endian types, we just use the existing ScalarTraits for the underlying
+// type.  This way endian aware types are supported whenever a ScalarTraits
+// is defined for the underlying type.
+template <typename value_type, support::endianness endian, size_t alignment>
+struct ScalarTraits<support::detail::packed_endian_specific_integral<
+    value_type, endian, alignment>> {
+  using endian_type =
+      support::detail::packed_endian_specific_integral<value_type, endian,
+                                                       alignment>;
+
+  static void output(const endian_type &E, void *Ctx, raw_ostream &Stream) {
+    ScalarTraits<value_type>::output(static_cast<value_type>(E), Ctx, Stream);
+  }
+
+  static StringRef input(StringRef Str, void *Ctx, endian_type &E) {
+    value_type V;
+    auto R = ScalarTraits<value_type>::input(Str, Ctx, V);
+    E = static_cast<endian_type>(V);
+    return R;
+  }
+
+  static QuotingType mustQuote(StringRef Str) {
+    return ScalarTraits<value_type>::mustQuote(Str);
+  }
+};
+
+// Utility for use within MappingTraits<>::mapping() method
+// to [de]normalize an object for use with YAML conversion.
+template <typename TNorm, typename TFinal>
+struct MappingNormalization {
+  MappingNormalization(IO &i_o, TFinal &Obj)
+      : io(i_o), BufPtr(nullptr), Result(Obj) {
+    if ( io.outputting() ) {
+      BufPtr = new (&Buffer) TNorm(io, Obj);
+    }
+    else {
+      BufPtr = new (&Buffer) TNorm(io);
+    }
+  }
+
+  ~MappingNormalization() {
+    if ( ! io.outputting() ) {
+      Result = BufPtr->denormalize(io);
+    }
+    BufPtr->~TNorm();
+  }
+
+  TNorm* operator->() { return BufPtr; }
+
+private:
+  using Storage = AlignedCharArrayUnion<TNorm>;
+
+  Storage       Buffer;
+  IO           &io;
+  TNorm        *BufPtr;
+  TFinal       &Result;
+};
+
+// Utility for use within MappingTraits<>::mapping() method
+// to [de]normalize an object for use with YAML conversion.
+template <typename TNorm, typename TFinal>
+struct MappingNormalizationHeap {
+  MappingNormalizationHeap(IO &i_o, TFinal &Obj, BumpPtrAllocator *allocator)
+    : io(i_o), Result(Obj) {
+    if ( io.outputting() ) {
+      BufPtr = new (&Buffer) TNorm(io, Obj);
+    }
+    else if (allocator) {
+      BufPtr = allocator->Allocate<TNorm>();
+      new (BufPtr) TNorm(io);
+    } else {
+      BufPtr = new TNorm(io);
+    }
+  }
+
+  ~MappingNormalizationHeap() {
+    if ( io.outputting() ) {
+      BufPtr->~TNorm();
+    }
+    else {
+      Result = BufPtr->denormalize(io);
+    }
+  }
+
+  TNorm* operator->() { return BufPtr; }
+
+private:
+  using Storage = AlignedCharArrayUnion<TNorm>;
+
+  Storage       Buffer;
+  IO           &io;
+  TNorm        *BufPtr = nullptr;
+  TFinal       &Result;
+};
+
+///
+/// The Input class is used to parse a yaml document into in-memory structs
+/// and vectors.
+///
+/// It works by using YAMLParser to do a syntax parse of the entire yaml
+/// document, then the Input class builds a graph of HNodes which wraps
+/// each yaml Node.  The extra layer is buffering.  The low level yaml
+/// parser only lets you look at each node once.  The buffering layer lets
+/// you search and interate multiple times.  This is necessary because
+/// the mapRequired() method calls may not be in the same order
+/// as the keys in the document.
+///
+class Input : public IO {
+public:
+  // Construct a yaml Input object from a StringRef and optional
+  // user-data. The DiagHandler can be specified to provide
+  // alternative error reporting.
+  Input(StringRef InputContent,
+        void *Ctxt = nullptr,
+        SourceMgr::DiagHandlerTy DiagHandler = nullptr,
+        void *DiagHandlerCtxt = nullptr);
+  Input(MemoryBufferRef Input,
+        void *Ctxt = nullptr,
+        SourceMgr::DiagHandlerTy DiagHandler = nullptr,
+        void *DiagHandlerCtxt = nullptr);
+  ~Input() override;
+
+  // Check if there was an syntax or semantic error during parsing.
+  std::error_code error();
+
+private:
+  bool outputting() override;
+  bool mapTag(StringRef, bool) override;
+  void beginMapping() override;
+  void endMapping() override;
+  bool preflightKey(const char *, bool, bool, bool &, void *&) override;
+  void postflightKey(void *) override;
+  std::vector<StringRef> keys() override;
+  void beginFlowMapping() override;
+  void endFlowMapping() override;
+  unsigned beginSequence() override;
+  void endSequence() override;
+  bool preflightElement(unsigned index, void *&) override;
+  void postflightElement(void *) override;
+  unsigned beginFlowSequence() override;
+  bool preflightFlowElement(unsigned , void *&) override;
+  void postflightFlowElement(void *) override;
+  void endFlowSequence() override;
+  void beginEnumScalar() override;
+  bool matchEnumScalar(const char*, bool) override;
+  bool matchEnumFallback() override;
+  void endEnumScalar() override;
+  bool beginBitSetScalar(bool &) override;
+  bool bitSetMatch(const char *, bool ) override;
+  void endBitSetScalar() override;
+  void scalarString(StringRef &, QuotingType) override;
+  void blockScalarString(StringRef &) override;
+  void setError(const Twine &message) override;
+  bool canElideEmptySequence() override;
+
+  class HNode {
+    virtual void anchor();
+
+  public:
+    HNode(Node *n) : _node(n) { }
+    virtual ~HNode() = default;
+
+    static bool classof(const HNode *) { return true; }
+
+    Node *_node;
+  };
+
+  class EmptyHNode : public HNode {
+    void anchor() override;
+
+  public:
+    EmptyHNode(Node *n) : HNode(n) { }
+
+    static bool classof(const HNode *n) { return NullNode::classof(n->_node); }
+
+    static bool classof(const EmptyHNode *) { return true; }
+  };
+
+  class ScalarHNode : public HNode {
+    void anchor() override;
+
+  public:
+    ScalarHNode(Node *n, StringRef s) : HNode(n), _value(s) { }
+
+    StringRef value() const { return _value; }
+
+    static bool classof(const HNode *n) {
+      return ScalarNode::classof(n->_node) ||
+             BlockScalarNode::classof(n->_node);
+    }
+
+    static bool classof(const ScalarHNode *) { return true; }
+
+  protected:
+    StringRef _value;
+  };
+
+  class MapHNode : public HNode {
+    void anchor() override;
+
+  public:
+    MapHNode(Node *n) : HNode(n) { }
+
+    static bool classof(const HNode *n) {
+      return MappingNode::classof(n->_node);
+    }
+
+    static bool classof(const MapHNode *) { return true; }
+
+    using NameToNode = StringMap<std::unique_ptr<HNode>>;
+
+    NameToNode Mapping;
+    SmallVector<std::string, 6> ValidKeys;
+  };
+
+  class SequenceHNode : public HNode {
+    void anchor() override;
+
+  public:
+    SequenceHNode(Node *n) : HNode(n) { }
+
+    static bool classof(const HNode *n) {
+      return SequenceNode::classof(n->_node);
+    }
+
+    static bool classof(const SequenceHNode *) { return true; }
+
+    std::vector<std::unique_ptr<HNode>> Entries;
+  };
+
+  std::unique_ptr<Input::HNode> createHNodes(Node *node);
+  void setError(HNode *hnode, const Twine &message);
+  void setError(Node *node, const Twine &message);
+
+public:
+  // These are only used by operator>>. They could be private
+  // if those templated things could be made friends.
+  bool setCurrentDocument();
+  bool nextDocument();
+
+  /// Returns the current node that's being parsed by the YAML Parser.
+  const Node *getCurrentNode() const;
+
+private:
+  SourceMgr                           SrcMgr; // must be before Strm
+  std::unique_ptr<llvm::yaml::Stream> Strm;
+  std::unique_ptr<HNode>              TopNode;
+  std::error_code                     EC;
+  BumpPtrAllocator                    StringAllocator;
+  document_iterator                   DocIterator;
+  std::vector<bool>                   BitValuesUsed;
+  HNode *CurrentNode = nullptr;
+  bool                                ScalarMatchFound;
+};
+
+///
+/// The Output class is used to generate a yaml document from in-memory structs
+/// and vectors.
+///
+class Output : public IO {
+public:
+  Output(raw_ostream &, void *Ctxt = nullptr, int WrapColumn = 70);
+  ~Output() override;
+
+  /// \brief Set whether or not to output optional values which are equal
+  /// to the default value.  By default, when outputting if you attempt
+  /// to write a value that is equal to the default, the value gets ignored.
+  /// Sometimes, it is useful to be able to see these in the resulting YAML
+  /// anyway.
+  void setWriteDefaultValues(bool Write) { WriteDefaultValues = Write; }
+
+  bool outputting() override;
+  bool mapTag(StringRef, bool) override;
+  void beginMapping() override;
+  void endMapping() override;
+  bool preflightKey(const char *key, bool, bool, bool &, void *&) override;
+  void postflightKey(void *) override;
+  std::vector<StringRef> keys() override;
+  void beginFlowMapping() override;
+  void endFlowMapping() override;
+  unsigned beginSequence() override;
+  void endSequence() override;
+  bool preflightElement(unsigned, void *&) override;
+  void postflightElement(void *) override;
+  unsigned beginFlowSequence() override;
+  bool preflightFlowElement(unsigned, void *&) override;
+  void postflightFlowElement(void *) override;
+  void endFlowSequence() override;
+  void beginEnumScalar() override;
+  bool matchEnumScalar(const char*, bool) override;
+  bool matchEnumFallback() override;
+  void endEnumScalar() override;
+  bool beginBitSetScalar(bool &) override;
+  bool bitSetMatch(const char *, bool ) override;
+  void endBitSetScalar() override;
+  void scalarString(StringRef &, QuotingType) override;
+  void blockScalarString(StringRef &) override;
+  void setError(const Twine &message) override;
+  bool canElideEmptySequence() override;
+
+  // These are only used by operator<<. They could be private
+  // if that templated operator could be made a friend.
+  void beginDocuments();
+  bool preflightDocument(unsigned);
+  void postflightDocument();
+  void endDocuments();
+
+private:
+  void output(StringRef s);
+  void outputUpToEndOfLine(StringRef s);
+  void newLineCheck();
+  void outputNewLine();
+  void paddedKey(StringRef key);
+  void flowKey(StringRef Key);
+
+  enum InState {
+    inSeq,
+    inFlowSeq,
+    inMapFirstKey,
+    inMapOtherKey,
+    inFlowMapFirstKey,
+    inFlowMapOtherKey
+  };
+
+  raw_ostream &Out;
+  int WrapColumn;
+  SmallVector<InState, 8> StateStack;
+  int Column = 0;
+  int ColumnAtFlowStart = 0;
+  int ColumnAtMapFlowStart = 0;
+  bool NeedBitValueComma = false;
+  bool NeedFlowSequenceComma = false;
+  bool EnumerationMatchFound = false;
+  bool NeedsNewLine = false;
+  bool WriteDefaultValues = false;
+};
+
+/// YAML I/O does conversion based on types. But often native data types
+/// are just a typedef of built in intergral types (e.g. int).  But the C++
+/// type matching system sees through the typedef and all the typedefed types
+/// look like a built in type. This will cause the generic YAML I/O conversion
+/// to be used. To provide better control over the YAML conversion, you can
+/// use this macro instead of typedef.  It will create a class with one field
+/// and automatic conversion operators to and from the base type.
+/// Based on BOOST_STRONG_TYPEDEF
+#define LLVM_YAML_STRONG_TYPEDEF(_base, _type)                                 \
+    struct _type {                                                             \
+        _type() = default;                                                     \
+        _type(const _base v) : value(v) {}                                     \
+        _type(const _type &v) = default;                                       \
+        _type &operator=(const _type &rhs) = default;                          \
+        _type &operator=(const _base &rhs) { value = rhs; return *this; }      \
+        operator const _base & () const { return value; }                      \
+        bool operator==(const _type &rhs) const { return value == rhs.value; } \
+        bool operator==(const _base &rhs) const { return value == rhs; }       \
+        bool operator<(const _type &rhs) const { return value < rhs.value; }   \
+        _base value;                                                           \
+        using BaseType = _base;                                                \
+    };
+
+///
+/// Use these types instead of uintXX_t in any mapping to have
+/// its yaml output formatted as hexadecimal.
+///
+LLVM_YAML_STRONG_TYPEDEF(uint8_t, Hex8)
+LLVM_YAML_STRONG_TYPEDEF(uint16_t, Hex16)
+LLVM_YAML_STRONG_TYPEDEF(uint32_t, Hex32)
+LLVM_YAML_STRONG_TYPEDEF(uint64_t, Hex64)
+
+template<>
+struct ScalarTraits<Hex8> {
+  static void output(const Hex8 &, void *, raw_ostream &);
+  static StringRef input(StringRef, void *, Hex8 &);
+  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
+};
+
+template<>
+struct ScalarTraits<Hex16> {
+  static void output(const Hex16 &, void *, raw_ostream &);
+  static StringRef input(StringRef, void *, Hex16 &);
+  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
+};
+
+template<>
+struct ScalarTraits<Hex32> {
+  static void output(const Hex32 &, void *, raw_ostream &);
+  static StringRef input(StringRef, void *, Hex32 &);
+  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
+};
+
+template<>
+struct ScalarTraits<Hex64> {
+  static void output(const Hex64 &, void *, raw_ostream &);
+  static StringRef input(StringRef, void *, Hex64 &);
+  static QuotingType mustQuote(StringRef) { return QuotingType::None; }
+};
+
+// Define non-member operator>> so that Input can stream in a document list.
+template <typename T>
+inline
+typename std::enable_if<has_DocumentListTraits<T>::value, Input &>::type
+operator>>(Input &yin, T &docList) {
+  int i = 0;
+  EmptyContext Ctx;
+  while ( yin.setCurrentDocument() ) {
+    yamlize(yin, DocumentListTraits<T>::element(yin, docList, i), true, Ctx);
+    if ( yin.error() )
+      return yin;
+    yin.nextDocument();
+    ++i;
+  }
+  return yin;
+}
+
+// Define non-member operator>> so that Input can stream in a map as a document.
+template <typename T>
+inline typename std::enable_if<has_MappingTraits<T, EmptyContext>::value,
+                               Input &>::type
+operator>>(Input &yin, T &docMap) {
+  EmptyContext Ctx;
+  yin.setCurrentDocument();
+  yamlize(yin, docMap, true, Ctx);
+  return yin;
+}
+
+// Define non-member operator>> so that Input can stream in a sequence as
+// a document.
+template <typename T>
+inline
+typename std::enable_if<has_SequenceTraits<T>::value, Input &>::type
+operator>>(Input &yin, T &docSeq) {
+  EmptyContext Ctx;
+  if (yin.setCurrentDocument())
+    yamlize(yin, docSeq, true, Ctx);
+  return yin;
+}
+
+// Define non-member operator>> so that Input can stream in a block scalar.
+template <typename T>
+inline
+typename std::enable_if<has_BlockScalarTraits<T>::value, Input &>::type
+operator>>(Input &In, T &Val) {
+  EmptyContext Ctx;
+  if (In.setCurrentDocument())
+    yamlize(In, Val, true, Ctx);
+  return In;
+}
+
+// Define non-member operator>> so that Input can stream in a string map.
+template <typename T>
+inline
+typename std::enable_if<has_CustomMappingTraits<T>::value, Input &>::type
+operator>>(Input &In, T &Val) {
+  EmptyContext Ctx;
+  if (In.setCurrentDocument())
+    yamlize(In, Val, true, Ctx);
+  return In;
+}
+
+// Provide better error message about types missing a trait specialization
+template <typename T>
+inline typename std::enable_if<missingTraits<T, EmptyContext>::value,
+                               Input &>::type
+operator>>(Input &yin, T &docSeq) {
+  char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
+  return yin;
+}
+
+// Define non-member operator<< so that Output can stream out document list.
+template <typename T>
+inline
+typename std::enable_if<has_DocumentListTraits<T>::value, Output &>::type
+operator<<(Output &yout, T &docList) {
+  EmptyContext Ctx;
+  yout.beginDocuments();
+  const size_t count = DocumentListTraits<T>::size(yout, docList);
+  for(size_t i=0; i < count; ++i) {
+    if ( yout.preflightDocument(i) ) {
+      yamlize(yout, DocumentListTraits<T>::element(yout, docList, i), true,
+              Ctx);
+      yout.postflightDocument();
+    }
+  }
+  yout.endDocuments();
+  return yout;
+}
+
+// Define non-member operator<< so that Output can stream out a map.
+template <typename T>
+inline typename std::enable_if<has_MappingTraits<T, EmptyContext>::value,
+                               Output &>::type
+operator<<(Output &yout, T &map) {
+  EmptyContext Ctx;
+  yout.beginDocuments();
+  if ( yout.preflightDocument(0) ) {
+    yamlize(yout, map, true, Ctx);
+    yout.postflightDocument();
+  }
+  yout.endDocuments();
+  return yout;
+}
+
+// Define non-member operator<< so that Output can stream out a sequence.
+template <typename T>
+inline
+typename std::enable_if<has_SequenceTraits<T>::value, Output &>::type
+operator<<(Output &yout, T &seq) {
+  EmptyContext Ctx;
+  yout.beginDocuments();
+  if ( yout.preflightDocument(0) ) {
+    yamlize(yout, seq, true, Ctx);
+    yout.postflightDocument();
+  }
+  yout.endDocuments();
+  return yout;
+}
+
+// Define non-member operator<< so that Output can stream out a block scalar.
+template <typename T>
+inline
+typename std::enable_if<has_BlockScalarTraits<T>::value, Output &>::type
+operator<<(Output &Out, T &Val) {
+  EmptyContext Ctx;
+  Out.beginDocuments();
+  if (Out.preflightDocument(0)) {
+    yamlize(Out, Val, true, Ctx);
+    Out.postflightDocument();
+  }
+  Out.endDocuments();
+  return Out;
+}
+
+// Define non-member operator<< so that Output can stream out a string map.
+template <typename T>
+inline
+typename std::enable_if<has_CustomMappingTraits<T>::value, Output &>::type
+operator<<(Output &Out, T &Val) {
+  EmptyContext Ctx;
+  Out.beginDocuments();
+  if (Out.preflightDocument(0)) {
+    yamlize(Out, Val, true, Ctx);
+    Out.postflightDocument();
+  }
+  Out.endDocuments();
+  return Out;
+}
+
+// Provide better error message about types missing a trait specialization
+template <typename T>
+inline typename std::enable_if<missingTraits<T, EmptyContext>::value,
+                               Output &>::type
+operator<<(Output &yout, T &seq) {
+  char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
+  return yout;
+}
+
+template <bool B> struct IsFlowSequenceBase {};
+template <> struct IsFlowSequenceBase<true> { static const bool flow = true; };
+
+template <typename T, bool Flow>
+struct SequenceTraitsImpl : IsFlowSequenceBase<Flow> {
+private:
+  using type = typename T::value_type;
+
+public:
+  static size_t size(IO &io, T &seq) { return seq.size(); }
+
+  static type &element(IO &io, T &seq, size_t index) {
+    if (index >= seq.size())
+      seq.resize(index + 1);
+    return seq[index];
+  }
+};
+
+// Simple helper to check an expression can be used as a bool-valued template
+// argument.
+template <bool> struct CheckIsBool { static const bool value = true; };
+
+// If T has SequenceElementTraits, then vector<T> and SmallVector<T, N> have
+// SequenceTraits that do the obvious thing.
+template <typename T>
+struct SequenceTraits<std::vector<T>,
+                      typename std::enable_if<CheckIsBool<
+                          SequenceElementTraits<T>::flow>::value>::type>
+    : SequenceTraitsImpl<std::vector<T>, SequenceElementTraits<T>::flow> {};
+template <typename T, unsigned N>
+struct SequenceTraits<SmallVector<T, N>,
+                      typename std::enable_if<CheckIsBool<
+                          SequenceElementTraits<T>::flow>::value>::type>
+    : SequenceTraitsImpl<SmallVector<T, N>, SequenceElementTraits<T>::flow> {};
+
+// Sequences of fundamental types use flow formatting.
+template <typename T>
+struct SequenceElementTraits<
+    T, typename std::enable_if<std::is_fundamental<T>::value>::type> {
+  static const bool flow = true;
+};
+
+// Sequences of strings use block formatting.
+template<> struct SequenceElementTraits<std::string> {
+  static const bool flow = false;
+};
+template<> struct SequenceElementTraits<StringRef> {
+  static const bool flow = false;
+};
+template<> struct SequenceElementTraits<std::pair<std::string, std::string>> {
+  static const bool flow = false;
+};
+
+/// Implementation of CustomMappingTraits for std::map<std::string, T>.
+template <typename T> struct StdMapStringCustomMappingTraitsImpl {
+  using map_type = std::map<std::string, T>;
+
+  static void inputOne(IO &io, StringRef key, map_type &v) {
+    io.mapRequired(key.str().c_str(), v[key]);
+  }
+
+  static void output(IO &io, map_type &v) {
+    for (auto &p : v)
+      io.mapRequired(p.first.c_str(), p.second);
+  }
+};
+
+} // end namespace yaml
+} // end namespace llvm
+
+#define LLVM_YAML_IS_SEQUENCE_VECTOR_IMPL(TYPE, FLOW)                          \
+  namespace llvm {                                                             \
+  namespace yaml {                                                             \
+  static_assert(                                                               \
+      !std::is_fundamental<TYPE>::value &&                                     \
+      !std::is_same<TYPE, std::string>::value &&                               \
+      !std::is_same<TYPE, llvm::StringRef>::value,                             \
+      "only use LLVM_YAML_IS_SEQUENCE_VECTOR for types you control");          \
+  template <> struct SequenceElementTraits<TYPE> {                             \
+    static const bool flow = FLOW;                                             \
+  };                                                                           \
+  }                                                                            \
+  }
+
+/// Utility for declaring that a std::vector of a particular type
+/// should be considered a YAML sequence.
+#define LLVM_YAML_IS_SEQUENCE_VECTOR(type)                                     \
+  LLVM_YAML_IS_SEQUENCE_VECTOR_IMPL(type, false)
+
+/// Utility for declaring that a std::vector of a particular type
+/// should be considered a YAML flow sequence.
+#define LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(type)                                \
+  LLVM_YAML_IS_SEQUENCE_VECTOR_IMPL(type, true)
+
+#define LLVM_YAML_DECLARE_MAPPING_TRAITS(Type)                                 \
+  namespace llvm {                                                             \
+  namespace yaml {                                                             \
+  template <> struct MappingTraits<Type> {                                     \
+    static void mapping(IO &IO, Type &Obj);                                    \
+  };                                                                           \
+  }                                                                            \
+  }
+
+#define LLVM_YAML_DECLARE_ENUM_TRAITS(Type)                                    \
+  namespace llvm {                                                             \
+  namespace yaml {                                                             \
+  template <> struct ScalarEnumerationTraits<Type> {                           \
+    static void enumeration(IO &io, Type &Value);                              \
+  };                                                                           \
+  }                                                                            \
+  }
+
+#define LLVM_YAML_DECLARE_BITSET_TRAITS(Type)                                  \
+  namespace llvm {                                                             \
+  namespace yaml {                                                             \
+  template <> struct ScalarBitSetTraits<Type> {                                \
+    static void bitset(IO &IO, Type &Options);                                 \
+  };                                                                           \
+  }                                                                            \
+  }
+
+#define LLVM_YAML_DECLARE_SCALAR_TRAITS(Type, MustQuote)                       \
+  namespace llvm {                                                             \
+  namespace yaml {                                                             \
+  template <> struct ScalarTraits<Type> {                                      \
+    static void output(const Type &Value, void *ctx, raw_ostream &Out);        \
+    static StringRef input(StringRef Scalar, void *ctxt, Type &Value);         \
+    static QuotingType mustQuote(StringRef) { return MustQuote; }              \
+  };                                                                           \
+  }                                                                            \
+  }
+
+/// Utility for declaring that a std::vector of a particular type
+/// should be considered a YAML document list.
+#define LLVM_YAML_IS_DOCUMENT_LIST_VECTOR(_type)                               \
+  namespace llvm {                                                             \
+  namespace yaml {                                                             \
+  template <unsigned N>                                                        \
+  struct DocumentListTraits<SmallVector<_type, N>>                             \
+      : public SequenceTraitsImpl<SmallVector<_type, N>, false> {};            \
+  template <>                                                                  \
+  struct DocumentListTraits<std::vector<_type>>                                \
+      : public SequenceTraitsImpl<std::vector<_type>, false> {};               \
+  }                                                                            \
+  }
+
+/// Utility for declaring that std::map<std::string, _type> should be considered
+/// a YAML map.
+#define LLVM_YAML_IS_STRING_MAP(_type)                                         \
+  namespace llvm {                                                             \
+  namespace yaml {                                                             \
+  template <>                                                                  \
+  struct CustomMappingTraits<std::map<std::string, _type>>                     \
+      : public StdMapStringCustomMappingTraitsImpl<_type> {};                  \
+  }                                                                            \
+  }
+
+#endif // LLVM_SUPPORT_YAMLTRAITS_H