YQ Connector: support managed ClickHouse

Со стороны dqrun можно обратиться к инстансу коннектора, который работает на streaming стенде, и извлечь данные из облачного CH.

1 files changed, 2368 insertions, 0 deletions

diff --git a/contrib/libs/llvm16/lib/Demangle/MicrosoftDemangle.cpp b/contrib/libs/llvm16/lib/Demangle/MicrosoftDemangle.cpp
new file mode 100644
index 0000000000..c21b0a3010
--- /dev/null
+++ b/contrib/libs/llvm16/lib/Demangle/MicrosoftDemangle.cpp
@@ -0,0 +1,2368 @@
+//===- MicrosoftDemangle.cpp ----------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a demangler for MSVC-style mangled symbols.
+//
+// This file has no dependencies on the rest of LLVM so that it can be
+// easily reused in other programs such as libcxxabi.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Demangle/MicrosoftDemangle.h"
+#include "llvm/Demangle/Demangle.h"
+#include "llvm/Demangle/MicrosoftDemangleNodes.h"
+
+#include "llvm/Demangle/DemangleConfig.h"
+#include "llvm/Demangle/StringView.h"
+#include "llvm/Demangle/Utility.h"
+
+#include <array>
+#include <cctype>
+#include <cstdio>
+#include <tuple>
+
+using namespace llvm;
+using namespace ms_demangle;
+
+static bool startsWithDigit(StringView S) {
+  return !S.empty() && std::isdigit(S.front());
+}
+
+
+struct NodeList {
+  Node *N = nullptr;
+  NodeList *Next = nullptr;
+};
+
+static bool isMemberPointer(StringView MangledName, bool &Error) {
+  Error = false;
+  switch (MangledName.popFront()) {
+  case '$':
+    // This is probably an rvalue reference (e.g. $$Q), and you cannot have an
+    // rvalue reference to a member.
+    return false;
+  case 'A':
+    // 'A' indicates a reference, and you cannot have a reference to a member
+    // function or member.
+    return false;
+  case 'P':
+  case 'Q':
+  case 'R':
+  case 'S':
+    // These 4 values indicate some kind of pointer, but we still don't know
+    // what.
+    break;
+  default:
+    // isMemberPointer() is called only if isPointerType() returns true,
+    // and it rejects other prefixes.
+    DEMANGLE_UNREACHABLE;
+  }
+
+  // If it starts with a number, then 6 indicates a non-member function
+  // pointer, and 8 indicates a member function pointer.
+  if (startsWithDigit(MangledName)) {
+    if (MangledName[0] != '6' && MangledName[0] != '8') {
+      Error = true;
+      return false;
+    }
+    return (MangledName[0] == '8');
+  }
+
+  // Remove ext qualifiers since those can appear on either type and are
+  // therefore not indicative.
+  MangledName.consumeFront('E'); // 64-bit
+  MangledName.consumeFront('I'); // restrict
+  MangledName.consumeFront('F'); // unaligned
+
+  if (MangledName.empty()) {
+    Error = true;
+    return false;
+  }
+
+  // The next value should be either ABCD (non-member) or QRST (member).
+  switch (MangledName.front()) {
+  case 'A':
+  case 'B':
+  case 'C':
+  case 'D':
+    return false;
+  case 'Q':
+  case 'R':
+  case 'S':
+  case 'T':
+    return true;
+  default:
+    Error = true;
+    return false;
+  }
+}
+
+static SpecialIntrinsicKind
+consumeSpecialIntrinsicKind(StringView &MangledName) {
+  if (MangledName.consumeFront("?_7"))
+    return SpecialIntrinsicKind::Vftable;
+  if (MangledName.consumeFront("?_8"))
+    return SpecialIntrinsicKind::Vbtable;
+  if (MangledName.consumeFront("?_9"))
+    return SpecialIntrinsicKind::VcallThunk;
+  if (MangledName.consumeFront("?_A"))
+    return SpecialIntrinsicKind::Typeof;
+  if (MangledName.consumeFront("?_B"))
+    return SpecialIntrinsicKind::LocalStaticGuard;
+  if (MangledName.consumeFront("?_C"))
+    return SpecialIntrinsicKind::StringLiteralSymbol;
+  if (MangledName.consumeFront("?_P"))
+    return SpecialIntrinsicKind::UdtReturning;
+  if (MangledName.consumeFront("?_R0"))
+    return SpecialIntrinsicKind::RttiTypeDescriptor;
+  if (MangledName.consumeFront("?_R1"))
+    return SpecialIntrinsicKind::RttiBaseClassDescriptor;
+  if (MangledName.consumeFront("?_R2"))
+    return SpecialIntrinsicKind::RttiBaseClassArray;
+  if (MangledName.consumeFront("?_R3"))
+    return SpecialIntrinsicKind::RttiClassHierarchyDescriptor;
+  if (MangledName.consumeFront("?_R4"))
+    return SpecialIntrinsicKind::RttiCompleteObjLocator;
+  if (MangledName.consumeFront("?_S"))
+    return SpecialIntrinsicKind::LocalVftable;
+  if (MangledName.consumeFront("?__E"))
+    return SpecialIntrinsicKind::DynamicInitializer;
+  if (MangledName.consumeFront("?__F"))
+    return SpecialIntrinsicKind::DynamicAtexitDestructor;
+  if (MangledName.consumeFront("?__J"))
+    return SpecialIntrinsicKind::LocalStaticThreadGuard;
+  return SpecialIntrinsicKind::None;
+}
+
+static bool startsWithLocalScopePattern(StringView S) {
+  if (!S.consumeFront('?'))
+    return false;
+
+  size_t End = S.find('?');
+  if (End == StringView::npos)
+    return false;
+  StringView Candidate = S.substr(0, End);
+  if (Candidate.empty())
+    return false;
+
+  // \?[0-9]\?
+  // ?@? is the discriminator 0.
+  if (Candidate.size() == 1)
+    return Candidate[0] == '@' || (Candidate[0] >= '0' && Candidate[0] <= '9');
+
+  // If it's not 0-9, then it's an encoded number terminated with an @
+  if (Candidate.back() != '@')
+    return false;
+  Candidate = Candidate.dropBack();
+
+  // An encoded number starts with B-P and all subsequent digits are in A-P.
+  // Note that the reason the first digit cannot be A is two fold.  First, it
+  // would create an ambiguity with ?A which delimits the beginning of an
+  // anonymous namespace.  Second, A represents 0, and you don't start a multi
+  // digit number with a leading 0.  Presumably the anonymous namespace
+  // ambiguity is also why single digit encoded numbers use 0-9 rather than A-J.
+  if (Candidate[0] < 'B' || Candidate[0] > 'P')
+    return false;
+  Candidate = Candidate.dropFront();
+  while (!Candidate.empty()) {
+    if (Candidate[0] < 'A' || Candidate[0] > 'P')
+      return false;
+    Candidate = Candidate.dropFront();
+  }
+
+  return true;
+}
+
+static bool isTagType(StringView S) {
+  switch (S.front()) {
+  case 'T': // union
+  case 'U': // struct
+  case 'V': // class
+  case 'W': // enum
+    return true;
+  }
+  return false;
+}
+
+static bool isCustomType(StringView S) { return S[0] == '?'; }
+
+static bool isPointerType(StringView S) {
+  if (S.startsWith("$$Q")) // foo &&
+    return true;
+
+  switch (S.front()) {
+  case 'A': // foo &
+  case 'P': // foo *
+  case 'Q': // foo *const
+  case 'R': // foo *volatile
+  case 'S': // foo *const volatile
+    return true;
+  }
+  return false;
+}
+
+static bool isArrayType(StringView S) { return S[0] == 'Y'; }
+
+static bool isFunctionType(StringView S) {
+  return S.startsWith("$$A8@@") || S.startsWith("$$A6");
+}
+
+static FunctionRefQualifier
+demangleFunctionRefQualifier(StringView &MangledName) {
+  if (MangledName.consumeFront('G'))
+    return FunctionRefQualifier::Reference;
+  else if (MangledName.consumeFront('H'))
+    return FunctionRefQualifier::RValueReference;
+  return FunctionRefQualifier::None;
+}
+
+static std::pair<Qualifiers, PointerAffinity>
+demanglePointerCVQualifiers(StringView &MangledName) {
+  if (MangledName.consumeFront("$$Q"))
+    return std::make_pair(Q_None, PointerAffinity::RValueReference);
+
+  switch (MangledName.popFront()) {
+  case 'A':
+    return std::make_pair(Q_None, PointerAffinity::Reference);
+  case 'P':
+    return std::make_pair(Q_None, PointerAffinity::Pointer);
+  case 'Q':
+    return std::make_pair(Q_Const, PointerAffinity::Pointer);
+  case 'R':
+    return std::make_pair(Q_Volatile, PointerAffinity::Pointer);
+  case 'S':
+    return std::make_pair(Qualifiers(Q_Const | Q_Volatile),
+                          PointerAffinity::Pointer);
+  }
+  // This function is only called if isPointerType() returns true,
+  // and it only returns true for the six cases listed above.
+  DEMANGLE_UNREACHABLE;
+}
+
+StringView Demangler::copyString(StringView Borrowed) {
+  char *Stable = Arena.allocUnalignedBuffer(Borrowed.size());
+  // This is not a micro-optimization, it avoids UB, should Borrowed be an null
+  // buffer.
+  if (Borrowed.size())
+    std::memcpy(Stable, Borrowed.begin(), Borrowed.size());
+
+  return {Stable, Borrowed.size()};
+}
+
+SpecialTableSymbolNode *
+Demangler::demangleSpecialTableSymbolNode(StringView &MangledName,
+                                          SpecialIntrinsicKind K) {
+  NamedIdentifierNode *NI = Arena.alloc<NamedIdentifierNode>();
+  switch (K) {
+  case SpecialIntrinsicKind::Vftable:
+    NI->Name = "`vftable'";
+    break;
+  case SpecialIntrinsicKind::Vbtable:
+    NI->Name = "`vbtable'";
+    break;
+  case SpecialIntrinsicKind::LocalVftable:
+    NI->Name = "`local vftable'";
+    break;
+  case SpecialIntrinsicKind::RttiCompleteObjLocator:
+    NI->Name = "`RTTI Complete Object Locator'";
+    break;
+  default:
+    DEMANGLE_UNREACHABLE;
+  }
+  QualifiedNameNode *QN = demangleNameScopeChain(MangledName, NI);
+  SpecialTableSymbolNode *STSN = Arena.alloc<SpecialTableSymbolNode>();
+  STSN->Name = QN;
+  bool IsMember = false;
+  if (MangledName.empty()) {
+    Error = true;
+    return nullptr;
+  }
+  char Front = MangledName.popFront();
+  if (Front != '6' && Front != '7') {
+    Error = true;
+    return nullptr;
+  }
+
+  std::tie(STSN->Quals, IsMember) = demangleQualifiers(MangledName);
+  if (!MangledName.consumeFront('@'))
+    STSN->TargetName = demangleFullyQualifiedTypeName(MangledName);
+  return STSN;
+}
+
+LocalStaticGuardVariableNode *
+Demangler::demangleLocalStaticGuard(StringView &MangledName, bool IsThread) {
+  LocalStaticGuardIdentifierNode *LSGI =
+      Arena.alloc<LocalStaticGuardIdentifierNode>();
+  LSGI->IsThread = IsThread;
+  QualifiedNameNode *QN = demangleNameScopeChain(MangledName, LSGI);
+  LocalStaticGuardVariableNode *LSGVN =
+      Arena.alloc<LocalStaticGuardVariableNode>();
+  LSGVN->Name = QN;
+
+  if (MangledName.consumeFront("4IA"))
+    LSGVN->IsVisible = false;
+  else if (MangledName.consumeFront("5"))
+    LSGVN->IsVisible = true;
+  else {
+    Error = true;
+    return nullptr;
+  }
+
+  if (!MangledName.empty())
+    LSGI->ScopeIndex = demangleUnsigned(MangledName);
+  return LSGVN;
+}
+
+static NamedIdentifierNode *synthesizeNamedIdentifier(ArenaAllocator &Arena,
+                                                      StringView Name) {
+  NamedIdentifierNode *Id = Arena.alloc<NamedIdentifierNode>();
+  Id->Name = Name;
+  return Id;
+}
+
+static QualifiedNameNode *synthesizeQualifiedName(ArenaAllocator &Arena,
+                                                  IdentifierNode *Identifier) {
+  QualifiedNameNode *QN = Arena.alloc<QualifiedNameNode>();
+  QN->Components = Arena.alloc<NodeArrayNode>();
+  QN->Components->Count = 1;
+  QN->Components->Nodes = Arena.allocArray<Node *>(1);
+  QN->Components->Nodes[0] = Identifier;
+  return QN;
+}
+
+static QualifiedNameNode *synthesizeQualifiedName(ArenaAllocator &Arena,
+                                                  StringView Name) {
+  NamedIdentifierNode *Id = synthesizeNamedIdentifier(Arena, Name);
+  return synthesizeQualifiedName(Arena, Id);
+}
+
+static VariableSymbolNode *synthesizeVariable(ArenaAllocator &Arena,
+                                              TypeNode *Type,
+                                              StringView VariableName) {
+  VariableSymbolNode *VSN = Arena.alloc<VariableSymbolNode>();
+  VSN->Type = Type;
+  VSN->Name = synthesizeQualifiedName(Arena, VariableName);
+  return VSN;
+}
+
+VariableSymbolNode *Demangler::demangleUntypedVariable(
+    ArenaAllocator &Arena, StringView &MangledName, StringView VariableName) {
+  NamedIdentifierNode *NI = synthesizeNamedIdentifier(Arena, VariableName);
+  QualifiedNameNode *QN = demangleNameScopeChain(MangledName, NI);
+  VariableSymbolNode *VSN = Arena.alloc<VariableSymbolNode>();
+  VSN->Name = QN;
+  if (MangledName.consumeFront("8"))
+    return VSN;
+
+  Error = true;
+  return nullptr;
+}
+
+VariableSymbolNode *
+Demangler::demangleRttiBaseClassDescriptorNode(ArenaAllocator &Arena,
+                                               StringView &MangledName) {
+  RttiBaseClassDescriptorNode *RBCDN =
+      Arena.alloc<RttiBaseClassDescriptorNode>();
+  RBCDN->NVOffset = demangleUnsigned(MangledName);
+  RBCDN->VBPtrOffset = demangleSigned(MangledName);
+  RBCDN->VBTableOffset = demangleUnsigned(MangledName);
+  RBCDN->Flags = demangleUnsigned(MangledName);
+  if (Error)
+    return nullptr;
+
+  VariableSymbolNode *VSN = Arena.alloc<VariableSymbolNode>();
+  VSN->Name = demangleNameScopeChain(MangledName, RBCDN);
+  MangledName.consumeFront('8');
+  return VSN;
+}
+
+FunctionSymbolNode *Demangler::demangleInitFiniStub(StringView &MangledName,
+                                                    bool IsDestructor) {
+  DynamicStructorIdentifierNode *DSIN =
+      Arena.alloc<DynamicStructorIdentifierNode>();
+  DSIN->IsDestructor = IsDestructor;
+
+  bool IsKnownStaticDataMember = false;
+  if (MangledName.consumeFront('?'))
+    IsKnownStaticDataMember = true;
+
+  SymbolNode *Symbol = demangleDeclarator(MangledName);
+  if (Error)
+    return nullptr;
+
+  FunctionSymbolNode *FSN = nullptr;
+
+  if (Symbol->kind() == NodeKind::VariableSymbol) {
+    DSIN->Variable = static_cast<VariableSymbolNode *>(Symbol);
+
+    // Older versions of clang mangled this type of symbol incorrectly.  They
+    // would omit the leading ? and they would only emit a single @ at the end.
+    // The correct mangling is a leading ? and 2 trailing @ signs.  Handle
+    // both cases.
+    int AtCount = IsKnownStaticDataMember ? 2 : 1;
+    for (int I = 0; I < AtCount; ++I) {
+      if (MangledName.consumeFront('@'))
+        continue;
+      Error = true;
+      return nullptr;
+    }
+
+    FSN = demangleFunctionEncoding(MangledName);
+    if (FSN)
+      FSN->Name = synthesizeQualifiedName(Arena, DSIN);
+  } else {
+    if (IsKnownStaticDataMember) {
+      // This was supposed to be a static data member, but we got a function.
+      Error = true;
+      return nullptr;
+    }
+
+    FSN = static_cast<FunctionSymbolNode *>(Symbol);
+    DSIN->Name = Symbol->Name;
+    FSN->Name = synthesizeQualifiedName(Arena, DSIN);
+  }
+
+  return FSN;
+}
+
+SymbolNode *Demangler::demangleSpecialIntrinsic(StringView &MangledName) {
+  SpecialIntrinsicKind SIK = consumeSpecialIntrinsicKind(MangledName);
+
+  switch (SIK) {
+  case SpecialIntrinsicKind::None:
+    return nullptr;
+  case SpecialIntrinsicKind::StringLiteralSymbol:
+    return demangleStringLiteral(MangledName);
+  case SpecialIntrinsicKind::Vftable:
+  case SpecialIntrinsicKind::Vbtable:
+  case SpecialIntrinsicKind::LocalVftable:
+  case SpecialIntrinsicKind::RttiCompleteObjLocator:
+    return demangleSpecialTableSymbolNode(MangledName, SIK);
+  case SpecialIntrinsicKind::VcallThunk:
+    return demangleVcallThunkNode(MangledName);
+  case SpecialIntrinsicKind::LocalStaticGuard:
+    return demangleLocalStaticGuard(MangledName, /*IsThread=*/false);
+  case SpecialIntrinsicKind::LocalStaticThreadGuard:
+    return demangleLocalStaticGuard(MangledName, /*IsThread=*/true);
+  case SpecialIntrinsicKind::RttiTypeDescriptor: {
+    TypeNode *T = demangleType(MangledName, QualifierMangleMode::Result);
+    if (Error)
+      break;
+    if (!MangledName.consumeFront("@8"))
+      break;
+    if (!MangledName.empty())
+      break;
+    return synthesizeVariable(Arena, T, "`RTTI Type Descriptor'");
+  }
+  case SpecialIntrinsicKind::RttiBaseClassArray:
+    return demangleUntypedVariable(Arena, MangledName,
+                                   "`RTTI Base Class Array'");
+  case SpecialIntrinsicKind::RttiClassHierarchyDescriptor:
+    return demangleUntypedVariable(Arena, MangledName,
+                                   "`RTTI Class Hierarchy Descriptor'");
+  case SpecialIntrinsicKind::RttiBaseClassDescriptor:
+    return demangleRttiBaseClassDescriptorNode(Arena, MangledName);
+  case SpecialIntrinsicKind::DynamicInitializer:
+    return demangleInitFiniStub(MangledName, /*IsDestructor=*/false);
+  case SpecialIntrinsicKind::DynamicAtexitDestructor:
+    return demangleInitFiniStub(MangledName, /*IsDestructor=*/true);
+  case SpecialIntrinsicKind::Typeof:
+  case SpecialIntrinsicKind::UdtReturning:
+    // It's unclear which tools produces these manglings, so demangling
+    // support is not (yet?) implemented.
+    break;
+  case SpecialIntrinsicKind::Unknown:
+    DEMANGLE_UNREACHABLE; // Never returned by consumeSpecialIntrinsicKind.
+  }
+  Error = true;
+  return nullptr;
+}
+
+IdentifierNode *
+Demangler::demangleFunctionIdentifierCode(StringView &MangledName) {
+  assert(MangledName.startsWith('?'));
+  MangledName = MangledName.dropFront();
+  if (MangledName.empty()) {
+    Error = true;
+    return nullptr;
+  }
+
+  if (MangledName.consumeFront("__"))
+    return demangleFunctionIdentifierCode(
+        MangledName, FunctionIdentifierCodeGroup::DoubleUnder);
+  if (MangledName.consumeFront("_"))
+    return demangleFunctionIdentifierCode(MangledName,
+                                          FunctionIdentifierCodeGroup::Under);
+  return demangleFunctionIdentifierCode(MangledName,
+                                        FunctionIdentifierCodeGroup::Basic);
+}
+
+StructorIdentifierNode *
+Demangler::demangleStructorIdentifier(StringView &MangledName,
+                                      bool IsDestructor) {
+  StructorIdentifierNode *N = Arena.alloc<StructorIdentifierNode>();
+  N->IsDestructor = IsDestructor;
+  return N;
+}
+
+ConversionOperatorIdentifierNode *
+Demangler::demangleConversionOperatorIdentifier(StringView &MangledName) {
+  ConversionOperatorIdentifierNode *N =
+      Arena.alloc<ConversionOperatorIdentifierNode>();
+  return N;
+}
+
+LiteralOperatorIdentifierNode *
+Demangler::demangleLiteralOperatorIdentifier(StringView &MangledName) {
+  LiteralOperatorIdentifierNode *N =
+      Arena.alloc<LiteralOperatorIdentifierNode>();
+  N->Name = demangleSimpleString(MangledName, /*Memorize=*/false);
+  return N;
+}
+
+IntrinsicFunctionKind
+Demangler::translateIntrinsicFunctionCode(char CH,
+                                          FunctionIdentifierCodeGroup Group) {
+  using IFK = IntrinsicFunctionKind;
+  if (!(CH >= '0' && CH <= '9') && !(CH >= 'A' && CH <= 'Z')) {
+    Error = true;
+    return IFK::None;
+  }
+
+  // Not all ? identifiers are intrinsics *functions*.  This function only maps
+  // operator codes for the special functions, all others are handled elsewhere,
+  // hence the IFK::None entries in the table.
+  static IFK Basic[36] = {
+      IFK::None,             // ?0 # Foo::Foo()
+      IFK::None,             // ?1 # Foo::~Foo()
+      IFK::New,              // ?2 # operator new
+      IFK::Delete,           // ?3 # operator delete
+      IFK::Assign,           // ?4 # operator=
+      IFK::RightShift,       // ?5 # operator>>
+      IFK::LeftShift,        // ?6 # operator<<
+      IFK::LogicalNot,       // ?7 # operator!
+      IFK::Equals,           // ?8 # operator==
+      IFK::NotEquals,        // ?9 # operator!=
+      IFK::ArraySubscript,   // ?A # operator[]
+      IFK::None,             // ?B # Foo::operator <type>()
+      IFK::Pointer,          // ?C # operator->
+      IFK::Dereference,      // ?D # operator*
+      IFK::Increment,        // ?E # operator++
+      IFK::Decrement,        // ?F # operator--
+      IFK::Minus,            // ?G # operator-
+      IFK::Plus,             // ?H # operator+
+      IFK::BitwiseAnd,       // ?I # operator&
+      IFK::MemberPointer,    // ?J # operator->*
+      IFK::Divide,           // ?K # operator/
+      IFK::Modulus,          // ?L # operator%
+      IFK::LessThan,         // ?M operator<
+      IFK::LessThanEqual,    // ?N operator<=
+      IFK::GreaterThan,      // ?O operator>
+      IFK::GreaterThanEqual, // ?P operator>=
+      IFK::Comma,            // ?Q operator,
+      IFK::Parens,           // ?R operator()
+      IFK::BitwiseNot,       // ?S operator~
+      IFK::BitwiseXor,       // ?T operator^
+      IFK::BitwiseOr,        // ?U operator|
+      IFK::LogicalAnd,       // ?V operator&&
+      IFK::LogicalOr,        // ?W operator||
+      IFK::TimesEqual,       // ?X operator*=
+      IFK::PlusEqual,        // ?Y operator+=
+      IFK::MinusEqual,       // ?Z operator-=
+  };
+  static IFK Under[36] = {
+      IFK::DivEqual,           // ?_0 operator/=
+      IFK::ModEqual,           // ?_1 operator%=
+      IFK::RshEqual,           // ?_2 operator>>=
+      IFK::LshEqual,           // ?_3 operator<<=
+      IFK::BitwiseAndEqual,    // ?_4 operator&=
+      IFK::BitwiseOrEqual,     // ?_5 operator|=
+      IFK::BitwiseXorEqual,    // ?_6 operator^=
+      IFK::None,               // ?_7 # vftable
+      IFK::None,               // ?_8 # vbtable
+      IFK::None,               // ?_9 # vcall
+      IFK::None,               // ?_A # typeof
+      IFK::None,               // ?_B # local static guard
+      IFK::None,               // ?_C # string literal
+      IFK::VbaseDtor,          // ?_D # vbase destructor
+      IFK::VecDelDtor,         // ?_E # vector deleting destructor
+      IFK::DefaultCtorClosure, // ?_F # default constructor closure
+      IFK::ScalarDelDtor,      // ?_G # scalar deleting destructor
+      IFK::VecCtorIter,        // ?_H # vector constructor iterator
+      IFK::VecDtorIter,        // ?_I # vector destructor iterator
+      IFK::VecVbaseCtorIter,   // ?_J # vector vbase constructor iterator
+      IFK::VdispMap,           // ?_K # virtual displacement map
+      IFK::EHVecCtorIter,      // ?_L # eh vector constructor iterator
+      IFK::EHVecDtorIter,      // ?_M # eh vector destructor iterator
+      IFK::EHVecVbaseCtorIter, // ?_N # eh vector vbase constructor iterator
+      IFK::CopyCtorClosure,    // ?_O # copy constructor closure
+      IFK::None,               // ?_P<name> # udt returning <name>
+      IFK::None,               // ?_Q # <unknown>
+      IFK::None,               // ?_R0 - ?_R4 # RTTI Codes
+      IFK::None,               // ?_S # local vftable
+      IFK::LocalVftableCtorClosure, // ?_T # local vftable constructor closure
+      IFK::ArrayNew,                // ?_U operator new[]
+      IFK::ArrayDelete,             // ?_V operator delete[]
+      IFK::None,                    // ?_W <unused>
+      IFK::None,                    // ?_X <unused>
+      IFK::None,                    // ?_Y <unused>
+      IFK::None,                    // ?_Z <unused>
+  };
+  static IFK DoubleUnder[36] = {
+      IFK::None,                       // ?__0 <unused>
+      IFK::None,                       // ?__1 <unused>
+      IFK::None,                       // ?__2 <unused>
+      IFK::None,                       // ?__3 <unused>
+      IFK::None,                       // ?__4 <unused>
+      IFK::None,                       // ?__5 <unused>
+      IFK::None,                       // ?__6 <unused>
+      IFK::None,                       // ?__7 <unused>
+      IFK::None,                       // ?__8 <unused>
+      IFK::None,                       // ?__9 <unused>
+      IFK::ManVectorCtorIter,          // ?__A managed vector ctor iterator
+      IFK::ManVectorDtorIter,          // ?__B managed vector dtor iterator
+      IFK::EHVectorCopyCtorIter,       // ?__C EH vector copy ctor iterator
+      IFK::EHVectorVbaseCopyCtorIter,  // ?__D EH vector vbase copy ctor iter
+      IFK::None,                       // ?__E dynamic initializer for `T'
+      IFK::None,                       // ?__F dynamic atexit destructor for `T'
+      IFK::VectorCopyCtorIter,         // ?__G vector copy constructor iter
+      IFK::VectorVbaseCopyCtorIter,    // ?__H vector vbase copy ctor iter
+      IFK::ManVectorVbaseCopyCtorIter, // ?__I managed vector vbase copy ctor
+                                       // iter
+      IFK::None,                       // ?__J local static thread guard
+      IFK::None,                       // ?__K operator ""_name
+      IFK::CoAwait,                    // ?__L operator co_await
+      IFK::Spaceship,                  // ?__M operator<=>
+      IFK::None,                       // ?__N <unused>
+      IFK::None,                       // ?__O <unused>
+      IFK::None,                       // ?__P <unused>
+      IFK::None,                       // ?__Q <unused>
+      IFK::None,                       // ?__R <unused>
+      IFK::None,                       // ?__S <unused>
+      IFK::None,                       // ?__T <unused>
+      IFK::None,                       // ?__U <unused>
+      IFK::None,                       // ?__V <unused>
+      IFK::None,                       // ?__W <unused>
+      IFK::None,                       // ?__X <unused>
+      IFK::None,                       // ?__Y <unused>
+      IFK::None,                       // ?__Z <unused>
+  };
+
+  int Index = (CH >= '0' && CH <= '9') ? (CH - '0') : (CH - 'A' + 10);
+  switch (Group) {
+  case FunctionIdentifierCodeGroup::Basic:
+    return Basic[Index];
+  case FunctionIdentifierCodeGroup::Under:
+    return Under[Index];
+  case FunctionIdentifierCodeGroup::DoubleUnder:
+    return DoubleUnder[Index];
+  }
+  DEMANGLE_UNREACHABLE;
+}
+
+IdentifierNode *
+Demangler::demangleFunctionIdentifierCode(StringView &MangledName,
+                                          FunctionIdentifierCodeGroup Group) {
+  if (MangledName.empty()) {
+    Error = true;
+    return nullptr;
+  }
+  switch (Group) {
+  case FunctionIdentifierCodeGroup::Basic:
+    switch (char CH = MangledName.popFront()) {
+    case '0':
+    case '1':
+      return demangleStructorIdentifier(MangledName, CH == '1');
+    case 'B':
+      return demangleConversionOperatorIdentifier(MangledName);
+    default:
+      return Arena.alloc<IntrinsicFunctionIdentifierNode>(
+          translateIntrinsicFunctionCode(CH, Group));
+    }
+  case FunctionIdentifierCodeGroup::Under:
+    return Arena.alloc<IntrinsicFunctionIdentifierNode>(
+        translateIntrinsicFunctionCode(MangledName.popFront(), Group));
+  case FunctionIdentifierCodeGroup::DoubleUnder:
+    switch (char CH = MangledName.popFront()) {
+    case 'K':
+      return demangleLiteralOperatorIdentifier(MangledName);
+    default:
+      return Arena.alloc<IntrinsicFunctionIdentifierNode>(
+          translateIntrinsicFunctionCode(CH, Group));
+    }
+  }
+
+  DEMANGLE_UNREACHABLE;
+}
+
+SymbolNode *Demangler::demangleEncodedSymbol(StringView &MangledName,
+                                             QualifiedNameNode *Name) {
+  if (MangledName.empty()) {
+    Error = true;
+    return nullptr;
+  }
+
+  // Read a variable.
+  switch (MangledName.front()) {
+  case '0':
+  case '1':
+  case '2':
+  case '3':
+  case '4': {
+    StorageClass SC = demangleVariableStorageClass(MangledName);
+    return demangleVariableEncoding(MangledName, SC);
+  }
+  }
+  FunctionSymbolNode *FSN = demangleFunctionEncoding(MangledName);
+
+  IdentifierNode *UQN = Name->getUnqualifiedIdentifier();
+  if (UQN->kind() == NodeKind::ConversionOperatorIdentifier) {
+    ConversionOperatorIdentifierNode *COIN =
+        static_cast<ConversionOperatorIdentifierNode *>(UQN);
+    if (FSN)
+      COIN->TargetType = FSN->Signature->ReturnType;
+  }
+  return FSN;
+}
+
+SymbolNode *Demangler::demangleDeclarator(StringView &MangledName) {
+  // What follows is a main symbol name. This may include namespaces or class
+  // back references.
+  QualifiedNameNode *QN = demangleFullyQualifiedSymbolName(MangledName);
+  if (Error)
+    return nullptr;
+
+  SymbolNode *Symbol = demangleEncodedSymbol(MangledName, QN);
+  if (Error)
+    return nullptr;
+  Symbol->Name = QN;
+
+  IdentifierNode *UQN = QN->getUnqualifiedIdentifier();
+  if (UQN->kind() == NodeKind::ConversionOperatorIdentifier) {
+    ConversionOperatorIdentifierNode *COIN =
+        static_cast<ConversionOperatorIdentifierNode *>(UQN);
+    if (!COIN->TargetType) {
+      Error = true;
+      return nullptr;
+    }
+  }
+  return Symbol;
+}
+
+SymbolNode *Demangler::demangleMD5Name(StringView &MangledName) {
+  assert(MangledName.startsWith("??@"));
+  // This is an MD5 mangled name.  We can't demangle it, just return the
+  // mangled name.
+  // An MD5 mangled name is ??@ followed by 32 characters and a terminating @.
+  size_t MD5Last = MangledName.find('@', strlen("??@"));
+  if (MD5Last == StringView::npos) {
+    Error = true;
+    return nullptr;
+  }
+  const char *Start = MangledName.begin();
+  MangledName = MangledName.dropFront(MD5Last + 1);
+
+  // There are two additional special cases for MD5 names:
+  // 1. For complete object locators where the object name is long enough
+  //    for the object to have an MD5 name, the complete object locator is
+  //    called ??@...@??_R4@ (with a trailing "??_R4@" instead of the usual
+  //    leading "??_R4". This is handled here.
+  // 2. For catchable types, in versions of MSVC before 2015 (<1900) or after
+  //    2017.2 (>= 1914), the catchable type mangling is _CT??@...@??@...@8
+  //    instead of_CT??@...@8 with just one MD5 name. Since we don't yet
+  //    demangle catchable types anywhere, this isn't handled for MD5 names
+  //    either.
+  MangledName.consumeFront("??_R4@");
+
+  StringView MD5(Start, MangledName.begin());
+  SymbolNode *S = Arena.alloc<SymbolNode>(NodeKind::Md5Symbol);
+  S->Name = synthesizeQualifiedName(Arena, MD5);
+
+  return S;
+}
+
+SymbolNode *Demangler::demangleTypeinfoName(StringView &MangledName) {
+  assert(MangledName.startsWith('.'));
+  MangledName.consumeFront('.');
+
+  TypeNode *T = demangleType(MangledName, QualifierMangleMode::Result);
+  if (Error || !MangledName.empty()) {
+    Error = true;
+    return nullptr;
+  }
+  return synthesizeVariable(Arena, T, "`RTTI Type Descriptor Name'");
+}
+
+// Parser entry point.
+SymbolNode *Demangler::parse(StringView &MangledName) {
+  // Typeinfo names are strings stored in RTTI data. They're not symbol names.
+  // It's still useful to demangle them. They're the only demangled entity
+  // that doesn't start with a "?" but a ".".
+  if (MangledName.startsWith('.'))
+    return demangleTypeinfoName(MangledName);
+
+  if (MangledName.startsWith("??@"))
+    return demangleMD5Name(MangledName);
+
+  // MSVC-style mangled symbols must start with '?'.
+  if (!MangledName.startsWith('?')) {
+    Error = true;
+    return nullptr;
+  }
+
+  MangledName.consumeFront('?');
+
+  // ?$ is a template instantiation, but all other names that start with ? are
+  // operators / special names.
+  if (SymbolNode *SI = demangleSpecialIntrinsic(MangledName))
+    return SI;
+
+  return demangleDeclarator(MangledName);
+}
+
+TagTypeNode *Demangler::parseTagUniqueName(StringView &MangledName) {
+  if (!MangledName.consumeFront(".?A")) {
+    Error = true;
+    return nullptr;
+  }
+  MangledName.consumeFront(".?A");
+  if (MangledName.empty()) {
+    Error = true;
+    return nullptr;
+  }
+
+  return demangleClassType(MangledName);
+}
+
+// <type-encoding> ::= <storage-class> <variable-type>
+// <storage-class> ::= 0  # private static member
+//                 ::= 1  # protected static member
+//                 ::= 2  # public static member
+//                 ::= 3  # global
+//                 ::= 4  # static local
+
+VariableSymbolNode *Demangler::demangleVariableEncoding(StringView &MangledName,
+                                                        StorageClass SC) {
+  VariableSymbolNode *VSN = Arena.alloc<VariableSymbolNode>();
+
+  VSN->Type = demangleType(MangledName, QualifierMangleMode::Drop);
+  VSN->SC = SC;
+
+  if (Error)
+    return nullptr;
+
+  // <variable-type> ::= <type> <cvr-qualifiers>
+  //                 ::= <type> <pointee-cvr-qualifiers> # pointers, references
+  switch (VSN->Type->kind()) {
+  case NodeKind::PointerType: {
+    PointerTypeNode *PTN = static_cast<PointerTypeNode *>(VSN->Type);
+
+    Qualifiers ExtraChildQuals = Q_None;
+    PTN->Quals = Qualifiers(VSN->Type->Quals |
+                            demanglePointerExtQualifiers(MangledName));
+
+    bool IsMember = false;
+    std::tie(ExtraChildQuals, IsMember) = demangleQualifiers(MangledName);
+
+    if (PTN->ClassParent) {
+      QualifiedNameNode *BackRefName =
+          demangleFullyQualifiedTypeName(MangledName);
+      (void)BackRefName;
+    }
+    PTN->Pointee->Quals = Qualifiers(PTN->Pointee->Quals | ExtraChildQuals);
+
+    break;
+  }
+  default:
+    VSN->Type->Quals = demangleQualifiers(MangledName).first;
+    break;
+  }
+
+  return VSN;
+}
+
+// Sometimes numbers are encoded in mangled symbols. For example,
+// "int (*x)[20]" is a valid C type (x is a pointer to an array of
+// length 20), so we need some way to embed numbers as part of symbols.
+// This function parses it.
+//
+// <number>               ::= [?] <non-negative integer>
+//
+// <non-negative integer> ::= <decimal digit> # when 1 <= Number <= 10
+//                        ::= <hex digit>+ @  # when Number == 0 or >= 10
+//
+// <hex-digit>            ::= [A-P]           # A = 0, B = 1, ...
+std::pair<uint64_t, bool> Demangler::demangleNumber(StringView &MangledName) {
+  bool IsNegative = MangledName.consumeFront('?');
+
+  if (startsWithDigit(MangledName)) {
+    uint64_t Ret = MangledName[0] - '0' + 1;
+    MangledName = MangledName.dropFront(1);
+    return {Ret, IsNegative};
+  }
+
+  uint64_t Ret = 0;
+  for (size_t i = 0; i < MangledName.size(); ++i) {
+    char C = MangledName[i];
+    if (C == '@') {
+      MangledName = MangledName.dropFront(i + 1);
+      return {Ret, IsNegative};
+    }
+    if ('A' <= C && C <= 'P') {
+      Ret = (Ret << 4) + (C - 'A');
+      continue;
+    }
+    break;
+  }
+
+  Error = true;
+  return {0ULL, false};
+}
+
+uint64_t Demangler::demangleUnsigned(StringView &MangledName) {
+  bool IsNegative = false;
+  uint64_t Number = 0;
+  std::tie(Number, IsNegative) = demangleNumber(MangledName);
+  if (IsNegative)
+    Error = true;
+  return Number;
+}
+
+int64_t Demangler::demangleSigned(StringView &MangledName) {
+  bool IsNegative = false;
+  uint64_t Number = 0;
+  std::tie(Number, IsNegative) = demangleNumber(MangledName);
+  if (Number > INT64_MAX)
+    Error = true;
+  int64_t I = static_cast<int64_t>(Number);
+  return IsNegative ? -I : I;
+}
+
+// First 10 strings can be referenced by special BackReferences ?0, ?1, ..., ?9.
+// Memorize it.
+void Demangler::memorizeString(StringView S) {
+  if (Backrefs.NamesCount >= BackrefContext::Max)
+    return;
+  for (size_t i = 0; i < Backrefs.NamesCount; ++i)
+    if (S == Backrefs.Names[i]->Name)
+      return;
+  NamedIdentifierNode *N = Arena.alloc<NamedIdentifierNode>();
+  N->Name = S;
+  Backrefs.Names[Backrefs.NamesCount++] = N;
+}
+
+NamedIdentifierNode *Demangler::demangleBackRefName(StringView &MangledName) {
+  assert(startsWithDigit(MangledName));
+
+  size_t I = MangledName[0] - '0';
+  if (I >= Backrefs.NamesCount) {
+    Error = true;
+    return nullptr;
+  }
+
+  MangledName = MangledName.dropFront();
+  return Backrefs.Names[I];
+}
+
+void Demangler::memorizeIdentifier(IdentifierNode *Identifier) {
+  // Render this class template name into a string buffer so that we can
+  // memorize it for the purpose of back-referencing.
+  OutputBuffer OB;
+  Identifier->output(OB, OF_Default);
+  StringView Owned = copyString(OB);
+  memorizeString(Owned);
+  std::free(OB.getBuffer());
+}
+
+IdentifierNode *
+Demangler::demangleTemplateInstantiationName(StringView &MangledName,
+                                             NameBackrefBehavior NBB) {
+  assert(MangledName.startsWith("?$"));
+  MangledName.consumeFront("?$");
+
+  BackrefContext OuterContext;
+  std::swap(OuterContext, Backrefs);
+
+  IdentifierNode *Identifier =
+      demangleUnqualifiedSymbolName(MangledName, NBB_Simple);
+  if (!Error)
+    Identifier->TemplateParams = demangleTemplateParameterList(MangledName);
+
+  std::swap(OuterContext, Backrefs);
+  if (Error)
+    return nullptr;
+
+  if (NBB & NBB_Template) {
+    // NBB_Template is only set for types and non-leaf names ("a::" in "a::b").
+    // Structors and conversion operators only makes sense in a leaf name, so
+    // reject them in NBB_Template contexts.
+    if (Identifier->kind() == NodeKind::ConversionOperatorIdentifier ||
+        Identifier->kind() == NodeKind::StructorIdentifier) {
+      Error = true;
+      return nullptr;
+    }
+
+    memorizeIdentifier(Identifier);
+  }
+
+  return Identifier;
+}
+
+NamedIdentifierNode *Demangler::demangleSimpleName(StringView &MangledName,
+                                                   bool Memorize) {
+  StringView S = demangleSimpleString(MangledName, Memorize);
+  if (Error)
+    return nullptr;
+
+  NamedIdentifierNode *Name = Arena.alloc<NamedIdentifierNode>();
+  Name->Name = S;
+  return Name;
+}
+
+static bool isRebasedHexDigit(char C) { return (C >= 'A' && C <= 'P'); }
+
+static uint8_t rebasedHexDigitToNumber(char C) {
+  assert(isRebasedHexDigit(C));
+  return (C <= 'J') ? (C - 'A') : (10 + C - 'K');
+}
+
+uint8_t Demangler::demangleCharLiteral(StringView &MangledName) {
+  assert(!MangledName.empty());
+  if (!MangledName.startsWith('?'))
+    return MangledName.popFront();
+
+  MangledName = MangledName.dropFront();
+  if (MangledName.empty())
+    goto CharLiteralError;
+
+  if (MangledName.consumeFront('$')) {
+    // Two hex digits
+    if (MangledName.size() < 2)
+      goto CharLiteralError;
+    StringView Nibbles = MangledName.substr(0, 2);
+    if (!isRebasedHexDigit(Nibbles[0]) || !isRebasedHexDigit(Nibbles[1]))
+      goto CharLiteralError;
+    // Don't append the null terminator.
+    uint8_t C1 = rebasedHexDigitToNumber(Nibbles[0]);
+    uint8_t C2 = rebasedHexDigitToNumber(Nibbles[1]);
+    MangledName = MangledName.dropFront(2);
+    return (C1 << 4) | C2;
+  }
+
+  if (startsWithDigit(MangledName)) {
+    const char *Lookup = ",/\\:. \n\t'-";
+    char C = Lookup[MangledName[0] - '0'];
+    MangledName = MangledName.dropFront();
+    return C;
+  }
+
+  if (MangledName[0] >= 'a' && MangledName[0] <= 'z') {
+    char Lookup[26] = {'\xE1', '\xE2', '\xE3', '\xE4', '\xE5', '\xE6', '\xE7',
+                       '\xE8', '\xE9', '\xEA', '\xEB', '\xEC', '\xED', '\xEE',
+                       '\xEF', '\xF0', '\xF1', '\xF2', '\xF3', '\xF4', '\xF5',
+                       '\xF6', '\xF7', '\xF8', '\xF9', '\xFA'};
+    char C = Lookup[MangledName[0] - 'a'];
+    MangledName = MangledName.dropFront();
+    return C;
+  }
+
+  if (MangledName[0] >= 'A' && MangledName[0] <= 'Z') {
+    char Lookup[26] = {'\xC1', '\xC2', '\xC3', '\xC4', '\xC5', '\xC6', '\xC7',
+                       '\xC8', '\xC9', '\xCA', '\xCB', '\xCC', '\xCD', '\xCE',
+                       '\xCF', '\xD0', '\xD1', '\xD2', '\xD3', '\xD4', '\xD5',
+                       '\xD6', '\xD7', '\xD8', '\xD9', '\xDA'};
+    char C = Lookup[MangledName[0] - 'A'];
+    MangledName = MangledName.dropFront();
+    return C;
+  }
+
+CharLiteralError:
+  Error = true;
+  return '\0';
+}
+
+wchar_t Demangler::demangleWcharLiteral(StringView &MangledName) {
+  uint8_t C1, C2;
+
+  C1 = demangleCharLiteral(MangledName);
+  if (Error || MangledName.empty())
+    goto WCharLiteralError;
+  C2 = demangleCharLiteral(MangledName);
+  if (Error)
+    goto WCharLiteralError;
+
+  return ((wchar_t)C1 << 8) | (wchar_t)C2;
+
+WCharLiteralError:
+  Error = true;
+  return L'\0';
+}
+
+static void writeHexDigit(char *Buffer, uint8_t Digit) {
+  assert(Digit <= 15);
+  *Buffer = (Digit < 10) ? ('0' + Digit) : ('A' + Digit - 10);
+}
+
+static void outputHex(OutputBuffer &OB, unsigned C) {
+  assert (C != 0);
+
+  // It's easier to do the math if we can work from right to left, but we need
+  // to print the numbers from left to right.  So render this into a temporary
+  // buffer first, then output the temporary buffer.  Each byte is of the form
+  // \xAB, which means that each byte needs 4 characters.  Since there are at
+  // most 4 bytes, we need a 4*4+1 = 17 character temporary buffer.
+  char TempBuffer[17];
+
+  ::memset(TempBuffer, 0, sizeof(TempBuffer));
+  constexpr int MaxPos = sizeof(TempBuffer) - 1;
+
+  int Pos = MaxPos - 1; // TempBuffer[MaxPos] is the terminating \0.
+  while (C != 0) {
+    for (int I = 0; I < 2; ++I) {
+      writeHexDigit(&TempBuffer[Pos--], C % 16);
+      C /= 16;
+    }
+  }
+  TempBuffer[Pos--] = 'x';
+  assert(Pos >= 0);
+  TempBuffer[Pos--] = '\\';
+  OB << StringView(&TempBuffer[Pos + 1]);
+}
+
+static void outputEscapedChar(OutputBuffer &OB, unsigned C) {
+  switch (C) {
+  case '\0': // nul
+    OB << "\\0";
+    return;
+  case '\'': // single quote
+    OB << "\\\'";
+    return;
+  case '\"': // double quote
+    OB << "\\\"";
+    return;
+  case '\\': // backslash
+    OB << "\\\\";
+    return;
+  case '\a': // bell
+    OB << "\\a";
+    return;
+  case '\b': // backspace
+    OB << "\\b";
+    return;
+  case '\f': // form feed
+    OB << "\\f";
+    return;
+  case '\n': // new line
+    OB << "\\n";
+    return;
+  case '\r': // carriage return
+    OB << "\\r";
+    return;
+  case '\t': // tab
+    OB << "\\t";
+    return;
+  case '\v': // vertical tab
+    OB << "\\v";
+    return;
+  default:
+    break;
+  }
+
+  if (C > 0x1F && C < 0x7F) {
+    // Standard ascii char.
+    OB << (char)C;
+    return;
+  }
+
+  outputHex(OB, C);
+}
+
+static unsigned countTrailingNullBytes(const uint8_t *StringBytes, int Length) {
+  const uint8_t *End = StringBytes + Length - 1;
+  unsigned Count = 0;
+  while (Length > 0 && *End == 0) {
+    --Length;
+    --End;
+    ++Count;
+  }
+  return Count;
+}
+
+static unsigned countEmbeddedNulls(const uint8_t *StringBytes,
+                                   unsigned Length) {
+  unsigned Result = 0;
+  for (unsigned I = 0; I < Length; ++I) {
+    if (*StringBytes++ == 0)
+      ++Result;
+  }
+  return Result;
+}
+
+// A mangled (non-wide) string literal stores the total length of the string it
+// refers to (passed in NumBytes), and it contains up to 32 bytes of actual text
+// (passed in StringBytes, NumChars).
+static unsigned guessCharByteSize(const uint8_t *StringBytes, unsigned NumChars,
+                                  uint64_t NumBytes) {
+  assert(NumBytes > 0);
+
+  // If the number of bytes is odd, this is guaranteed to be a char string.
+  if (NumBytes % 2 == 1)
+    return 1;
+
+  // All strings can encode at most 32 bytes of data.  If it's less than that,
+  // then we encoded the entire string.  In this case we check for a 1-byte,
+  // 2-byte, or 4-byte null terminator.
+  if (NumBytes < 32) {
+    unsigned TrailingNulls = countTrailingNullBytes(StringBytes, NumChars);
+    if (TrailingNulls >= 4 && NumBytes % 4 == 0)
+      return 4;
+    if (TrailingNulls >= 2)
+      return 2;
+    return 1;
+  }
+
+  // The whole string was not able to be encoded.  Try to look at embedded null
+  // terminators to guess.  The heuristic is that we count all embedded null
+  // terminators.  If more than 2/3 are null, it's a char32.  If more than 1/3
+  // are null, it's a char16.  Otherwise it's a char8.  This obviously isn't
+  // perfect and is biased towards languages that have ascii alphabets, but this
+  // was always going to be best effort since the encoding is lossy.
+  unsigned Nulls = countEmbeddedNulls(StringBytes, NumChars);
+  if (Nulls >= 2 * NumChars / 3 && NumBytes % 4 == 0)
+    return 4;
+  if (Nulls >= NumChars / 3)
+    return 2;
+  return 1;
+}
+
+static unsigned decodeMultiByteChar(const uint8_t *StringBytes,
+                                    unsigned CharIndex, unsigned CharBytes) {
+  assert(CharBytes == 1 || CharBytes == 2 || CharBytes == 4);
+  unsigned Offset = CharIndex * CharBytes;
+  unsigned Result = 0;
+  StringBytes = StringBytes + Offset;
+  for (unsigned I = 0; I < CharBytes; ++I) {
+    unsigned C = static_cast<unsigned>(StringBytes[I]);
+    Result |= C << (8 * I);
+  }
+  return Result;
+}
+
+FunctionSymbolNode *Demangler::demangleVcallThunkNode(StringView &MangledName) {
+  FunctionSymbolNode *FSN = Arena.alloc<FunctionSymbolNode>();
+  VcallThunkIdentifierNode *VTIN = Arena.alloc<VcallThunkIdentifierNode>();
+  FSN->Signature = Arena.alloc<ThunkSignatureNode>();
+  FSN->Signature->FunctionClass = FC_NoParameterList;
+
+  FSN->Name = demangleNameScopeChain(MangledName, VTIN);
+  if (!Error)
+    Error = !MangledName.consumeFront("$B");
+  if (!Error)
+    VTIN->OffsetInVTable = demangleUnsigned(MangledName);
+  if (!Error)
+    Error = !MangledName.consumeFront('A');
+  if (!Error)
+    FSN->Signature->CallConvention = demangleCallingConvention(MangledName);
+  return (Error) ? nullptr : FSN;
+}
+
+EncodedStringLiteralNode *
+Demangler::demangleStringLiteral(StringView &MangledName) {
+  // This function uses goto, so declare all variables up front.
+  OutputBuffer OB;
+  StringView CRC;
+  uint64_t StringByteSize;
+  bool IsWcharT = false;
+  bool IsNegative = false;
+  size_t CrcEndPos = 0;
+
+  EncodedStringLiteralNode *Result = Arena.alloc<EncodedStringLiteralNode>();
+
+  // Prefix indicating the beginning of a string literal
+  if (!MangledName.consumeFront("@_"))
+    goto StringLiteralError;
+  if (MangledName.empty())
+    goto StringLiteralError;
+
+  // Char Type (regular or wchar_t)
+  switch (MangledName.popFront()) {
+  case '1':
+    IsWcharT = true;
+    DEMANGLE_FALLTHROUGH;
+  case '0':
+    break;
+  default:
+    goto StringLiteralError;
+  }
+
+  // Encoded Length
+  std::tie(StringByteSize, IsNegative) = demangleNumber(MangledName);
+  if (Error || IsNegative || StringByteSize < (IsWcharT ? 2 : 1))
+    goto StringLiteralError;
+
+  // CRC 32 (always 8 characters plus a terminator)
+  CrcEndPos = MangledName.find('@');
+  if (CrcEndPos == StringView::npos)
+    goto StringLiteralError;
+  CRC = MangledName.substr(0, CrcEndPos);
+  MangledName = MangledName.dropFront(CrcEndPos + 1);
+  if (MangledName.empty())
+    goto StringLiteralError;
+
+  if (IsWcharT) {
+    Result->Char = CharKind::Wchar;
+    if (StringByteSize > 64)
+      Result->IsTruncated = true;
+
+    while (!MangledName.consumeFront('@')) {
+      if (MangledName.size() < 2)
+        goto StringLiteralError;
+      wchar_t W = demangleWcharLiteral(MangledName);
+      if (StringByteSize != 2 || Result->IsTruncated)
+        outputEscapedChar(OB, W);
+      StringByteSize -= 2;
+      if (Error)
+        goto StringLiteralError;
+    }
+  } else {
+    // The max byte length is actually 32, but some compilers mangled strings
+    // incorrectly, so we have to assume it can go higher.
+    constexpr unsigned MaxStringByteLength = 32 * 4;
+    uint8_t StringBytes[MaxStringByteLength];
+
+    unsigned BytesDecoded = 0;
+    while (!MangledName.consumeFront('@')) {
+      if (MangledName.size() < 1 || BytesDecoded >= MaxStringByteLength)
+        goto StringLiteralError;
+      StringBytes[BytesDecoded++] = demangleCharLiteral(MangledName);
+    }
+
+    if (StringByteSize > BytesDecoded)
+      Result->IsTruncated = true;
+
+    unsigned CharBytes =
+        guessCharByteSize(StringBytes, BytesDecoded, StringByteSize);
+    assert(StringByteSize % CharBytes == 0);
+    switch (CharBytes) {
+    case 1:
+      Result->Char = CharKind::Char;
+      break;
+    case 2:
+      Result->Char = CharKind::Char16;
+      break;
+    case 4:
+      Result->Char = CharKind::Char32;
+      break;
+    default:
+      DEMANGLE_UNREACHABLE;
+    }
+    const unsigned NumChars = BytesDecoded / CharBytes;
+    for (unsigned CharIndex = 0; CharIndex < NumChars; ++CharIndex) {
+      unsigned NextChar =
+          decodeMultiByteChar(StringBytes, CharIndex, CharBytes);
+      if (CharIndex + 1 < NumChars || Result->IsTruncated)
+        outputEscapedChar(OB, NextChar);
+    }
+  }
+
+  Result->DecodedString = copyString(OB);
+  std::free(OB.getBuffer());
+  return Result;
+
+StringLiteralError:
+  Error = true;
+  std::free(OB.getBuffer());
+  return nullptr;
+}
+
+// Returns MangledName's prefix before the first '@', or an error if
+// MangledName contains no '@' or the prefix has length 0.
+StringView Demangler::demangleSimpleString(StringView &MangledName,
+                                           bool Memorize) {
+  StringView S;
+  for (size_t i = 0; i < MangledName.size(); ++i) {
+    if (MangledName[i] != '@')
+      continue;
+    if (i == 0)
+      break;
+    S = MangledName.substr(0, i);
+    MangledName = MangledName.dropFront(i + 1);
+
+    if (Memorize)
+      memorizeString(S);
+    return S;
+  }
+
+  Error = true;
+  return {};
+}
+
+NamedIdentifierNode *
+Demangler::demangleAnonymousNamespaceName(StringView &MangledName) {
+  assert(MangledName.startsWith("?A"));
+  MangledName.consumeFront("?A");
+
+  NamedIdentifierNode *Node = Arena.alloc<NamedIdentifierNode>();
+  Node->Name = "`anonymous namespace'";
+  size_t EndPos = MangledName.find('@');
+  if (EndPos == StringView::npos) {
+    Error = true;
+    return nullptr;
+  }
+  StringView NamespaceKey = MangledName.substr(0, EndPos);
+  memorizeString(NamespaceKey);
+  MangledName = MangledName.substr(EndPos + 1);
+  return Node;
+}
+
+NamedIdentifierNode *
+Demangler::demangleLocallyScopedNamePiece(StringView &MangledName) {
+  assert(startsWithLocalScopePattern(MangledName));
+
+  NamedIdentifierNode *Identifier = Arena.alloc<NamedIdentifierNode>();
+  MangledName.consumeFront('?');
+  uint64_t Number = 0;
+  bool IsNegative = false;
+  std::tie(Number, IsNegative) = demangleNumber(MangledName);
+  assert(!IsNegative);
+
+  // One ? to terminate the number
+  MangledName.consumeFront('?');
+
+  assert(!Error);
+  Node *Scope = parse(MangledName);
+  if (Error)
+    return nullptr;
+
+  // Render the parent symbol's name into a buffer.
+  OutputBuffer OB;
+  OB << '`';
+  Scope->output(OB, OF_Default);
+  OB << '\'';
+  OB << "::`" << Number << "'";
+
+  Identifier->Name = copyString(OB);
+  std::free(OB.getBuffer());
+  return Identifier;
+}
+
+// Parses a type name in the form of A@B@C@@ which represents C::B::A.
+QualifiedNameNode *
+Demangler::demangleFullyQualifiedTypeName(StringView &MangledName) {
+  IdentifierNode *Identifier =
+      demangleUnqualifiedTypeName(MangledName, /*Memorize=*/true);
+  if (Error)
+    return nullptr;
+  assert(Identifier);
+
+  QualifiedNameNode *QN = demangleNameScopeChain(MangledName, Identifier);
+  if (Error)
+    return nullptr;
+  assert(QN);
+  return QN;
+}
+
+// Parses a symbol name in the form of A@B@C@@ which represents C::B::A.
+// Symbol names have slightly different rules regarding what can appear
+// so we separate out the implementations for flexibility.
+QualifiedNameNode *
+Demangler::demangleFullyQualifiedSymbolName(StringView &MangledName) {
+  // This is the final component of a symbol name (i.e. the leftmost component
+  // of a mangled name.  Since the only possible template instantiation that
+  // can appear in this context is a function template, and since those are
+  // not saved for the purposes of name backreferences, only backref simple
+  // names.
+  IdentifierNode *Identifier =
+      demangleUnqualifiedSymbolName(MangledName, NBB_Simple);
+  if (Error)
+    return nullptr;
+
+  QualifiedNameNode *QN = demangleNameScopeChain(MangledName, Identifier);
+  if (Error)
+    return nullptr;
+
+  if (Identifier->kind() == NodeKind::StructorIdentifier) {
+    if (QN->Components->Count < 2) {
+      Error = true;
+      return nullptr;
+    }
+    StructorIdentifierNode *SIN =
+        static_cast<StructorIdentifierNode *>(Identifier);
+    Node *ClassNode = QN->Components->Nodes[QN->Components->Count - 2];
+    SIN->Class = static_cast<IdentifierNode *>(ClassNode);
+  }
+  assert(QN);
+  return QN;
+}
+
+IdentifierNode *Demangler::demangleUnqualifiedTypeName(StringView &MangledName,
+                                                       bool Memorize) {
+  // An inner-most name can be a back-reference, because a fully-qualified name
+  // (e.g. Scope + Inner) can contain other fully qualified names inside of
+  // them (for example template parameters), and these nested parameters can
+  // refer to previously mangled types.
+  if (startsWithDigit(MangledName))
+    return demangleBackRefName(MangledName);
+
+  if (MangledName.startsWith("?$"))
+    return demangleTemplateInstantiationName(MangledName, NBB_Template);
+
+  return demangleSimpleName(MangledName, Memorize);
+}
+
+IdentifierNode *
+Demangler::demangleUnqualifiedSymbolName(StringView &MangledName,
+                                         NameBackrefBehavior NBB) {
+  if (startsWithDigit(MangledName))
+    return demangleBackRefName(MangledName);
+  if (MangledName.startsWith("?$"))
+    return demangleTemplateInstantiationName(MangledName, NBB);
+  if (MangledName.startsWith('?'))
+    return demangleFunctionIdentifierCode(MangledName);
+  return demangleSimpleName(MangledName, /*Memorize=*/(NBB & NBB_Simple) != 0);
+}
+
+IdentifierNode *Demangler::demangleNameScopePiece(StringView &MangledName) {
+  if (startsWithDigit(MangledName))
+    return demangleBackRefName(MangledName);
+
+  if (MangledName.startsWith("?$"))
+    return demangleTemplateInstantiationName(MangledName, NBB_Template);
+
+  if (MangledName.startsWith("?A"))
+    return demangleAnonymousNamespaceName(MangledName);
+
+  if (startsWithLocalScopePattern(MangledName))
+    return demangleLocallyScopedNamePiece(MangledName);
+
+  return demangleSimpleName(MangledName, /*Memorize=*/true);
+}
+
+static NodeArrayNode *nodeListToNodeArray(ArenaAllocator &Arena, NodeList *Head,
+                                          size_t Count) {
+  NodeArrayNode *N = Arena.alloc<NodeArrayNode>();
+  N->Count = Count;
+  N->Nodes = Arena.allocArray<Node *>(Count);
+  for (size_t I = 0; I < Count; ++I) {
+    N->Nodes[I] = Head->N;
+    Head = Head->Next;
+  }
+  return N;
+}
+
+QualifiedNameNode *
+Demangler::demangleNameScopeChain(StringView &MangledName,
+                                  IdentifierNode *UnqualifiedName) {
+  NodeList *Head = Arena.alloc<NodeList>();
+
+  Head->N = UnqualifiedName;
+
+  size_t Count = 1;
+  while (!MangledName.consumeFront("@")) {
+    ++Count;
+    NodeList *NewHead = Arena.alloc<NodeList>();
+    NewHead->Next = Head;
+    Head = NewHead;
+
+    if (MangledName.empty()) {
+      Error = true;
+      return nullptr;
+    }
+
+    assert(!Error);
+    IdentifierNode *Elem = demangleNameScopePiece(MangledName);
+    if (Error)
+      return nullptr;
+
+    Head->N = Elem;
+  }
+
+  QualifiedNameNode *QN = Arena.alloc<QualifiedNameNode>();
+  QN->Components = nodeListToNodeArray(Arena, Head, Count);
+  return QN;
+}
+
+FuncClass Demangler::demangleFunctionClass(StringView &MangledName) {
+  switch (MangledName.popFront()) {
+  case '9':
+    return FuncClass(FC_ExternC | FC_NoParameterList);
+  case 'A':
+    return FC_Private;
+  case 'B':
+    return FuncClass(FC_Private | FC_Far);
+  case 'C':
+    return FuncClass(FC_Private | FC_Static);
+  case 'D':
+    return FuncClass(FC_Private | FC_Static | FC_Far);
+  case 'E':
+    return FuncClass(FC_Private | FC_Virtual);
+  case 'F':
+    return FuncClass(FC_Private | FC_Virtual | FC_Far);
+  case 'G':
+    return FuncClass(FC_Private | FC_StaticThisAdjust);
+  case 'H':
+    return FuncClass(FC_Private | FC_StaticThisAdjust | FC_Far);
+  case 'I':
+    return FuncClass(FC_Protected);
+  case 'J':
+    return FuncClass(FC_Protected | FC_Far);
+  case 'K':
+    return FuncClass(FC_Protected | FC_Static);
+  case 'L':
+    return FuncClass(FC_Protected | FC_Static | FC_Far);
+  case 'M':
+    return FuncClass(FC_Protected | FC_Virtual);
+  case 'N':
+    return FuncClass(FC_Protected | FC_Virtual | FC_Far);
+  case 'O':
+    return FuncClass(FC_Protected | FC_Virtual | FC_StaticThisAdjust);
+  case 'P':
+    return FuncClass(FC_Protected | FC_Virtual | FC_StaticThisAdjust | FC_Far);
+  case 'Q':
+    return FuncClass(FC_Public);
+  case 'R':
+    return FuncClass(FC_Public | FC_Far);
+  case 'S':
+    return FuncClass(FC_Public | FC_Static);
+  case 'T':
+    return FuncClass(FC_Public | FC_Static | FC_Far);
+  case 'U':
+    return FuncClass(FC_Public | FC_Virtual);
+  case 'V':
+    return FuncClass(FC_Public | FC_Virtual | FC_Far);
+  case 'W':
+    return FuncClass(FC_Public | FC_Virtual | FC_StaticThisAdjust);
+  case 'X':
+    return FuncClass(FC_Public | FC_Virtual | FC_StaticThisAdjust | FC_Far);
+  case 'Y':
+    return FuncClass(FC_Global);
+  case 'Z':
+    return FuncClass(FC_Global | FC_Far);
+  case '$': {
+    FuncClass VFlag = FC_VirtualThisAdjust;
+    if (MangledName.consumeFront('R'))
+      VFlag = FuncClass(VFlag | FC_VirtualThisAdjustEx);
+    if (MangledName.empty())
+      break;
+    switch (MangledName.popFront()) {
+    case '0':
+      return FuncClass(FC_Private | FC_Virtual | VFlag);
+    case '1':
+      return FuncClass(FC_Private | FC_Virtual | VFlag | FC_Far);
+    case '2':
+      return FuncClass(FC_Protected | FC_Virtual | VFlag);
+    case '3':
+      return FuncClass(FC_Protected | FC_Virtual | VFlag | FC_Far);
+    case '4':
+      return FuncClass(FC_Public | FC_Virtual | VFlag);
+    case '5':
+      return FuncClass(FC_Public | FC_Virtual | VFlag | FC_Far);
+    }
+  }
+  }
+
+  Error = true;
+  return FC_Public;
+}
+
+CallingConv Demangler::demangleCallingConvention(StringView &MangledName) {
+  if (MangledName.empty()) {
+    Error = true;
+    return CallingConv::None;
+  }
+
+  switch (MangledName.popFront()) {
+  case 'A':
+  case 'B':
+    return CallingConv::Cdecl;
+  case 'C':
+  case 'D':
+    return CallingConv::Pascal;
+  case 'E':
+  case 'F':
+    return CallingConv::Thiscall;
+  case 'G':
+  case 'H':
+    return CallingConv::Stdcall;
+  case 'I':
+  case 'J':
+    return CallingConv::Fastcall;
+  case 'M':
+  case 'N':
+    return CallingConv::Clrcall;
+  case 'O':
+  case 'P':
+    return CallingConv::Eabi;
+  case 'Q':
+    return CallingConv::Vectorcall;
+  case 'S':
+    return CallingConv::Swift;
+  case 'W':
+    return CallingConv::SwiftAsync;
+  }
+
+  return CallingConv::None;
+}
+
+StorageClass Demangler::demangleVariableStorageClass(StringView &MangledName) {
+  assert(MangledName.front() >= '0' && MangledName.front() <= '4');
+
+  switch (MangledName.popFront()) {
+  case '0':
+    return StorageClass::PrivateStatic;
+  case '1':
+    return StorageClass::ProtectedStatic;
+  case '2':
+    return StorageClass::PublicStatic;
+  case '3':
+    return StorageClass::Global;
+  case '4':
+    return StorageClass::FunctionLocalStatic;
+  }
+  DEMANGLE_UNREACHABLE;
+}
+
+std::pair<Qualifiers, bool>
+Demangler::demangleQualifiers(StringView &MangledName) {
+  if (MangledName.empty()) {
+    Error = true;
+    return std::make_pair(Q_None, false);
+  }
+
+  switch (MangledName.popFront()) {
+  // Member qualifiers
+  case 'Q':
+    return std::make_pair(Q_None, true);
+  case 'R':
+    return std::make_pair(Q_Const, true);
+  case 'S':
+    return std::make_pair(Q_Volatile, true);
+  case 'T':
+    return std::make_pair(Qualifiers(Q_Const | Q_Volatile), true);
+  // Non-Member qualifiers
+  case 'A':
+    return std::make_pair(Q_None, false);
+  case 'B':
+    return std::make_pair(Q_Const, false);
+  case 'C':
+    return std::make_pair(Q_Volatile, false);
+  case 'D':
+    return std::make_pair(Qualifiers(Q_Const | Q_Volatile), false);
+  }
+  Error = true;
+  return std::make_pair(Q_None, false);
+}
+
+// <variable-type> ::= <type> <cvr-qualifiers>
+//                 ::= <type> <pointee-cvr-qualifiers> # pointers, references
+TypeNode *Demangler::demangleType(StringView &MangledName,
+                                  QualifierMangleMode QMM) {
+  Qualifiers Quals = Q_None;
+  bool IsMember = false;
+  if (QMM == QualifierMangleMode::Mangle) {
+    std::tie(Quals, IsMember) = demangleQualifiers(MangledName);
+  } else if (QMM == QualifierMangleMode::Result) {
+    if (MangledName.consumeFront('?'))
+      std::tie(Quals, IsMember) = demangleQualifiers(MangledName);
+  }
+
+  if (MangledName.empty()) {
+    Error = true;
+    return nullptr;
+  }
+
+  TypeNode *Ty = nullptr;
+  if (isTagType(MangledName))
+    Ty = demangleClassType(MangledName);
+  else if (isPointerType(MangledName)) {
+    if (isMemberPointer(MangledName, Error))
+      Ty = demangleMemberPointerType(MangledName);
+    else if (!Error)
+      Ty = demanglePointerType(MangledName);
+    else
+      return nullptr;
+  } else if (isArrayType(MangledName))
+    Ty = demangleArrayType(MangledName);
+  else if (isFunctionType(MangledName)) {
+    if (MangledName.consumeFront("$$A8@@"))
+      Ty = demangleFunctionType(MangledName, true);
+    else {
+      assert(MangledName.startsWith("$$A6"));
+      MangledName.consumeFront("$$A6");
+      Ty = demangleFunctionType(MangledName, false);
+    }
+  } else if (isCustomType(MangledName)) {
+    Ty = demangleCustomType(MangledName);
+  } else {
+    Ty = demanglePrimitiveType(MangledName);
+  }
+
+  if (!Ty || Error)
+    return Ty;
+  Ty->Quals = Qualifiers(Ty->Quals | Quals);
+  return Ty;
+}
+
+bool Demangler::demangleThrowSpecification(StringView &MangledName) {
+  if (MangledName.consumeFront("_E"))
+    return true;
+  if (MangledName.consumeFront('Z'))
+    return false;
+
+  Error = true;
+  return false;
+}
+
+FunctionSignatureNode *Demangler::demangleFunctionType(StringView &MangledName,
+                                                       bool HasThisQuals) {
+  FunctionSignatureNode *FTy = Arena.alloc<FunctionSignatureNode>();
+
+  if (HasThisQuals) {
+    FTy->Quals = demanglePointerExtQualifiers(MangledName);
+    FTy->RefQualifier = demangleFunctionRefQualifier(MangledName);
+    FTy->Quals = Qualifiers(FTy->Quals | demangleQualifiers(MangledName).first);
+  }
+
+  // Fields that appear on both member and non-member functions.
+  FTy->CallConvention = demangleCallingConvention(MangledName);
+
+  // <return-type> ::= <type>
+  //               ::= @ # structors (they have no declared return type)
+  bool IsStructor = MangledName.consumeFront('@');
+  if (!IsStructor)
+    FTy->ReturnType = demangleType(MangledName, QualifierMangleMode::Result);
+
+  FTy->Params = demangleFunctionParameterList(MangledName, FTy->IsVariadic);
+
+  FTy->IsNoexcept = demangleThrowSpecification(MangledName);
+
+  return FTy;
+}
+
+FunctionSymbolNode *
+Demangler::demangleFunctionEncoding(StringView &MangledName) {
+  FuncClass ExtraFlags = FC_None;
+  if (MangledName.consumeFront("$$J0"))
+    ExtraFlags = FC_ExternC;
+
+  if (MangledName.empty()) {
+    Error = true;
+    return nullptr;
+  }
+
+  FuncClass FC = demangleFunctionClass(MangledName);
+  FC = FuncClass(ExtraFlags | FC);
+
+  FunctionSignatureNode *FSN = nullptr;
+  ThunkSignatureNode *TTN = nullptr;
+  if (FC & FC_StaticThisAdjust) {
+    TTN = Arena.alloc<ThunkSignatureNode>();
+    TTN->ThisAdjust.StaticOffset = demangleSigned(MangledName);
+  } else if (FC & FC_VirtualThisAdjust) {
+    TTN = Arena.alloc<ThunkSignatureNode>();
+    if (FC & FC_VirtualThisAdjustEx) {
+      TTN->ThisAdjust.VBPtrOffset = demangleSigned(MangledName);
+      TTN->ThisAdjust.VBOffsetOffset = demangleSigned(MangledName);
+    }
+    TTN->ThisAdjust.VtordispOffset = demangleSigned(MangledName);
+    TTN->ThisAdjust.StaticOffset = demangleSigned(MangledName);
+  }
+
+  if (FC & FC_NoParameterList) {
+    // This is an extern "C" function whose full signature hasn't been mangled.
+    // This happens when we need to mangle a local symbol inside of an extern
+    // "C" function.
+    FSN = Arena.alloc<FunctionSignatureNode>();
+  } else {
+    bool HasThisQuals = !(FC & (FC_Global | FC_Static));
+    FSN = demangleFunctionType(MangledName, HasThisQuals);
+  }
+
+  if (Error)
+    return nullptr;
+
+  if (TTN) {
+    *static_cast<FunctionSignatureNode *>(TTN) = *FSN;
+    FSN = TTN;
+  }
+  FSN->FunctionClass = FC;
+
+  FunctionSymbolNode *Symbol = Arena.alloc<FunctionSymbolNode>();
+  Symbol->Signature = FSN;
+  return Symbol;
+}
+
+CustomTypeNode *Demangler::demangleCustomType(StringView &MangledName) {
+  assert(MangledName.startsWith('?'));
+  MangledName.popFront();
+
+  CustomTypeNode *CTN = Arena.alloc<CustomTypeNode>();
+  CTN->Identifier = demangleUnqualifiedTypeName(MangledName, /*Memorize=*/true);
+  if (!MangledName.consumeFront('@'))
+    Error = true;
+  if (Error)
+    return nullptr;
+  return CTN;
+}
+
+// Reads a primitive type.
+PrimitiveTypeNode *Demangler::demanglePrimitiveType(StringView &MangledName) {
+  if (MangledName.consumeFront("$$T"))
+    return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Nullptr);
+
+  switch (MangledName.popFront()) {
+  case 'X':
+    return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Void);
+  case 'D':
+    return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Char);
+  case 'C':
+    return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Schar);
+  case 'E':
+    return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Uchar);
+  case 'F':
+    return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Short);
+  case 'G':
+    return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Ushort);
+  case 'H':
+    return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Int);
+  case 'I':
+    return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Uint);
+  case 'J':
+    return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Long);
+  case 'K':
+    return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Ulong);
+  case 'M':
+    return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Float);
+  case 'N':
+    return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Double);
+  case 'O':
+    return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Ldouble);
+  case '_': {
+    if (MangledName.empty()) {
+      Error = true;
+      return nullptr;
+    }
+    switch (MangledName.popFront()) {
+    case 'N':
+      return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Bool);
+    case 'J':
+      return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Int64);
+    case 'K':
+      return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Uint64);
+    case 'W':
+      return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Wchar);
+    case 'Q':
+      return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Char8);
+    case 'S':
+      return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Char16);
+    case 'U':
+      return Arena.alloc<PrimitiveTypeNode>(PrimitiveKind::Char32);
+    }
+    break;
+  }
+  }
+  Error = true;
+  return nullptr;
+}
+
+TagTypeNode *Demangler::demangleClassType(StringView &MangledName) {
+  TagTypeNode *TT = nullptr;
+
+  switch (MangledName.popFront()) {
+  case 'T':
+    TT = Arena.alloc<TagTypeNode>(TagKind::Union);
+    break;
+  case 'U':
+    TT = Arena.alloc<TagTypeNode>(TagKind::Struct);
+    break;
+  case 'V':
+    TT = Arena.alloc<TagTypeNode>(TagKind::Class);
+    break;
+  case 'W':
+    if (!MangledName.consumeFront('4')) {
+      Error = true;
+      return nullptr;
+    }
+    TT = Arena.alloc<TagTypeNode>(TagKind::Enum);
+    break;
+  default:
+    assert(false);
+  }
+
+  TT->QualifiedName = demangleFullyQualifiedTypeName(MangledName);
+  return TT;
+}
+
+// <pointer-type> ::= E? <pointer-cvr-qualifiers> <ext-qualifiers> <type>
+//                       # the E is required for 64-bit non-static pointers
+PointerTypeNode *Demangler::demanglePointerType(StringView &MangledName) {
+  PointerTypeNode *Pointer = Arena.alloc<PointerTypeNode>();
+
+  std::tie(Pointer->Quals, Pointer->Affinity) =
+      demanglePointerCVQualifiers(MangledName);
+
+  if (MangledName.consumeFront("6")) {
+    Pointer->Pointee = demangleFunctionType(MangledName, false);
+    return Pointer;
+  }
+
+  Qualifiers ExtQuals = demanglePointerExtQualifiers(MangledName);
+  Pointer->Quals = Qualifiers(Pointer->Quals | ExtQuals);
+
+  Pointer->Pointee = demangleType(MangledName, QualifierMangleMode::Mangle);
+  return Pointer;
+}
+
+PointerTypeNode *Demangler::demangleMemberPointerType(StringView &MangledName) {
+  PointerTypeNode *Pointer = Arena.alloc<PointerTypeNode>();
+
+  std::tie(Pointer->Quals, Pointer->Affinity) =
+      demanglePointerCVQualifiers(MangledName);
+  assert(Pointer->Affinity == PointerAffinity::Pointer);
+
+  Qualifiers ExtQuals = demanglePointerExtQualifiers(MangledName);
+  Pointer->Quals = Qualifiers(Pointer->Quals | ExtQuals);
+
+  // isMemberPointer() only returns true if there is at least one character
+  // after the qualifiers.
+  if (MangledName.consumeFront("8")) {
+    Pointer->ClassParent = demangleFullyQualifiedTypeName(MangledName);
+    Pointer->Pointee = demangleFunctionType(MangledName, true);
+  } else {
+    Qualifiers PointeeQuals = Q_None;
+    bool IsMember = false;
+    std::tie(PointeeQuals, IsMember) = demangleQualifiers(MangledName);
+    assert(IsMember || Error);
+    Pointer->ClassParent = demangleFullyQualifiedTypeName(MangledName);
+
+    Pointer->Pointee = demangleType(MangledName, QualifierMangleMode::Drop);
+    if (Pointer->Pointee)
+      Pointer->Pointee->Quals = PointeeQuals;
+  }
+
+  return Pointer;
+}
+
+Qualifiers Demangler::demanglePointerExtQualifiers(StringView &MangledName) {
+  Qualifiers Quals = Q_None;
+  if (MangledName.consumeFront('E'))
+    Quals = Qualifiers(Quals | Q_Pointer64);
+  if (MangledName.consumeFront('I'))
+    Quals = Qualifiers(Quals | Q_Restrict);
+  if (MangledName.consumeFront('F'))
+    Quals = Qualifiers(Quals | Q_Unaligned);
+
+  return Quals;
+}
+
+ArrayTypeNode *Demangler::demangleArrayType(StringView &MangledName) {
+  assert(MangledName.front() == 'Y');
+  MangledName.popFront();
+
+  uint64_t Rank = 0;
+  bool IsNegative = false;
+  std::tie(Rank, IsNegative) = demangleNumber(MangledName);
+  if (IsNegative || Rank == 0) {
+    Error = true;
+    return nullptr;
+  }
+
+  ArrayTypeNode *ATy = Arena.alloc<ArrayTypeNode>();
+  NodeList *Head = Arena.alloc<NodeList>();
+  NodeList *Tail = Head;
+
+  for (uint64_t I = 0; I < Rank; ++I) {
+    uint64_t D = 0;
+    std::tie(D, IsNegative) = demangleNumber(MangledName);
+    if (Error || IsNegative) {
+      Error = true;
+      return nullptr;
+    }
+    Tail->N = Arena.alloc<IntegerLiteralNode>(D, IsNegative);
+    if (I + 1 < Rank) {
+      Tail->Next = Arena.alloc<NodeList>();
+      Tail = Tail->Next;
+    }
+  }
+  ATy->Dimensions = nodeListToNodeArray(Arena, Head, Rank);
+
+  if (MangledName.consumeFront("$$C")) {
+    bool IsMember = false;
+    std::tie(ATy->Quals, IsMember) = demangleQualifiers(MangledName);
+    if (IsMember) {
+      Error = true;
+      return nullptr;
+    }
+  }
+
+  ATy->ElementType = demangleType(MangledName, QualifierMangleMode::Drop);
+  return ATy;
+}
+
+// Reads a function's parameters.
+NodeArrayNode *Demangler::demangleFunctionParameterList(StringView &MangledName,
+                                                        bool &IsVariadic) {
+  // Empty parameter list.
+  if (MangledName.consumeFront('X'))
+    return nullptr;
+
+  NodeList *Head = Arena.alloc<NodeList>();
+  NodeList **Current = &Head;
+  size_t Count = 0;
+  while (!Error && !MangledName.startsWith('@') &&
+         !MangledName.startsWith('Z')) {
+    ++Count;
+
+    if (startsWithDigit(MangledName)) {
+      size_t N = MangledName[0] - '0';
+      if (N >= Backrefs.FunctionParamCount) {
+        Error = true;
+        return nullptr;
+      }
+      MangledName = MangledName.dropFront();
+
+      *Current = Arena.alloc<NodeList>();
+      (*Current)->N = Backrefs.FunctionParams[N];
+      Current = &(*Current)->Next;
+      continue;
+    }
+
+    size_t OldSize = MangledName.size();
+
+    *Current = Arena.alloc<NodeList>();
+    TypeNode *TN = demangleType(MangledName, QualifierMangleMode::Drop);
+    if (!TN || Error)
+      return nullptr;
+
+    (*Current)->N = TN;
+
+    size_t CharsConsumed = OldSize - MangledName.size();
+    assert(CharsConsumed != 0);
+
+    // Single-letter types are ignored for backreferences because memorizing
+    // them doesn't save anything.
+    if (Backrefs.FunctionParamCount <= 9 && CharsConsumed > 1)
+      Backrefs.FunctionParams[Backrefs.FunctionParamCount++] = TN;
+
+    Current = &(*Current)->Next;
+  }
+
+  if (Error)
+    return nullptr;
+
+  NodeArrayNode *NA = nodeListToNodeArray(Arena, Head, Count);
+  // A non-empty parameter list is terminated by either 'Z' (variadic) parameter
+  // list or '@' (non variadic).  Careful not to consume "@Z", as in that case
+  // the following Z could be a throw specifier.
+  if (MangledName.consumeFront('@'))
+    return NA;
+
+  if (MangledName.consumeFront('Z')) {
+    IsVariadic = true;
+    return NA;
+  }
+
+  DEMANGLE_UNREACHABLE;
+}
+
+NodeArrayNode *
+Demangler::demangleTemplateParameterList(StringView &MangledName) {
+  NodeList *Head = nullptr;
+  NodeList **Current = &Head;
+  size_t Count = 0;
+
+  while (!MangledName.startsWith('@')) {
+    if (MangledName.consumeFront("$S") || MangledName.consumeFront("$$V") ||
+        MangledName.consumeFront("$$$V") || MangledName.consumeFront("$$Z")) {
+      // parameter pack separator
+      continue;
+    }
+
+    ++Count;
+
+    // Template parameter lists don't participate in back-referencing.
+    *Current = Arena.alloc<NodeList>();
+
+    NodeList &TP = **Current;
+
+    TemplateParameterReferenceNode *TPRN = nullptr;
+    if (MangledName.consumeFront("$$Y")) {
+      // Template alias
+      TP.N = demangleFullyQualifiedTypeName(MangledName);
+    } else if (MangledName.consumeFront("$$B")) {
+      // Array
+      TP.N = demangleType(MangledName, QualifierMangleMode::Drop);
+    } else if (MangledName.consumeFront("$$C")) {
+      // Type has qualifiers.
+      TP.N = demangleType(MangledName, QualifierMangleMode::Mangle);
+    } else if (MangledName.startsWith("$1") || MangledName.startsWith("$H") ||
+               MangledName.startsWith("$I") || MangledName.startsWith("$J")) {
+      // Pointer to member
+      TP.N = TPRN = Arena.alloc<TemplateParameterReferenceNode>();
+      TPRN->IsMemberPointer = true;
+
+      MangledName = MangledName.dropFront();
+      // 1 - single inheritance       <name>
+      // H - multiple inheritance     <name> <number>
+      // I - virtual inheritance      <name> <number> <number>
+      // J - unspecified inheritance  <name> <number> <number> <number>
+      char InheritanceSpecifier = MangledName.popFront();
+      SymbolNode *S = nullptr;
+      if (MangledName.startsWith('?')) {
+        S = parse(MangledName);
+        if (Error || !S->Name) {
+          Error = true;
+          return nullptr;
+        }
+        memorizeIdentifier(S->Name->getUnqualifiedIdentifier());
+      }
+
+      switch (InheritanceSpecifier) {
+      case 'J':
+        TPRN->ThunkOffsets[TPRN->ThunkOffsetCount++] =
+            demangleSigned(MangledName);
+        DEMANGLE_FALLTHROUGH;
+      case 'I':
+        TPRN->ThunkOffsets[TPRN->ThunkOffsetCount++] =
+            demangleSigned(MangledName);
+        DEMANGLE_FALLTHROUGH;
+      case 'H':
+        TPRN->ThunkOffsets[TPRN->ThunkOffsetCount++] =
+            demangleSigned(MangledName);
+        DEMANGLE_FALLTHROUGH;
+      case '1':
+        break;
+      default:
+        DEMANGLE_UNREACHABLE;
+      }
+      TPRN->Affinity = PointerAffinity::Pointer;
+      TPRN->Symbol = S;
+    } else if (MangledName.startsWith("$E?")) {
+      MangledName.consumeFront("$E");
+      // Reference to symbol
+      TP.N = TPRN = Arena.alloc<TemplateParameterReferenceNode>();
+      TPRN->Symbol = parse(MangledName);
+      TPRN->Affinity = PointerAffinity::Reference;
+    } else if (MangledName.startsWith("$F") || MangledName.startsWith("$G")) {
+      TP.N = TPRN = Arena.alloc<TemplateParameterReferenceNode>();
+
+      // Data member pointer.
+      MangledName = MangledName.dropFront();
+      char InheritanceSpecifier = MangledName.popFront();
+
+      switch (InheritanceSpecifier) {
+      case 'G':
+        TPRN->ThunkOffsets[TPRN->ThunkOffsetCount++] =
+            demangleSigned(MangledName);
+        DEMANGLE_FALLTHROUGH;
+      case 'F':
+        TPRN->ThunkOffsets[TPRN->ThunkOffsetCount++] =
+            demangleSigned(MangledName);
+        TPRN->ThunkOffsets[TPRN->ThunkOffsetCount++] =
+            demangleSigned(MangledName);
+        break;
+      default:
+        DEMANGLE_UNREACHABLE;
+      }
+      TPRN->IsMemberPointer = true;
+
+    } else if (MangledName.consumeFront("$0")) {
+      // Integral non-type template parameter
+      bool IsNegative = false;
+      uint64_t Value = 0;
+      std::tie(Value, IsNegative) = demangleNumber(MangledName);
+
+      TP.N = Arena.alloc<IntegerLiteralNode>(Value, IsNegative);
+    } else {
+      TP.N = demangleType(MangledName, QualifierMangleMode::Drop);
+    }
+    if (Error)
+      return nullptr;
+
+    Current = &TP.Next;
+  }
+
+  // The loop above returns nullptr on Error.
+  assert(!Error);
+
+  // Template parameter lists cannot be variadic, so it can only be terminated
+  // by @ (as opposed to 'Z' in the function parameter case).
+  assert(MangledName.startsWith('@')); // The above loop exits only on '@'.
+  MangledName.consumeFront('@');
+  return nodeListToNodeArray(Arena, Head, Count);
+}
+
+void Demangler::dumpBackReferences() {
+  std::printf("%d function parameter backreferences\n",
+              (int)Backrefs.FunctionParamCount);
+
+  // Create an output stream so we can render each type.
+  OutputBuffer OB;
+  for (size_t I = 0; I < Backrefs.FunctionParamCount; ++I) {
+    OB.setCurrentPosition(0);
+
+    TypeNode *T = Backrefs.FunctionParams[I];
+    T->output(OB, OF_Default);
+
+    StringView B = OB;
+    std::printf("  [%d] - %.*s\n", (int)I, (int)B.size(), B.begin());
+  }
+  std::free(OB.getBuffer());
+
+  if (Backrefs.FunctionParamCount > 0)
+    std::printf("\n");
+  std::printf("%d name backreferences\n", (int)Backrefs.NamesCount);
+  for (size_t I = 0; I < Backrefs.NamesCount; ++I) {
+    std::printf("  [%d] - %.*s\n", (int)I, (int)Backrefs.Names[I]->Name.size(),
+                Backrefs.Names[I]->Name.begin());
+  }
+  if (Backrefs.NamesCount > 0)
+    std::printf("\n");
+}
+
+char *llvm::microsoftDemangle(const char *MangledName, size_t *NMangled,
+                              char *Buf, size_t *N,
+                              int *Status, MSDemangleFlags Flags) {
+  Demangler D;
+
+  StringView Name{MangledName};
+  SymbolNode *AST = D.parse(Name);
+  if (!D.Error && NMangled)
+    *NMangled = Name.begin() - MangledName;
+
+  if (Flags & MSDF_DumpBackrefs)
+    D.dumpBackReferences();
+
+  OutputFlags OF = OF_Default;
+  if (Flags & MSDF_NoCallingConvention)
+    OF = OutputFlags(OF | OF_NoCallingConvention);
+  if (Flags & MSDF_NoAccessSpecifier)
+    OF = OutputFlags(OF | OF_NoAccessSpecifier);
+  if (Flags & MSDF_NoReturnType)
+    OF = OutputFlags(OF | OF_NoReturnType);
+  if (Flags & MSDF_NoMemberType)
+    OF = OutputFlags(OF | OF_NoMemberType);
+  if (Flags & MSDF_NoVariableType)
+    OF = OutputFlags(OF | OF_NoVariableType);
+
+  int InternalStatus = demangle_success;
+  if (D.Error)
+    InternalStatus = demangle_invalid_mangled_name;
+  else {
+    OutputBuffer OB(Buf, N);
+    AST->output(OB, OF);
+    OB += '\0';
+    if (N != nullptr)
+      *N = OB.getCurrentPosition();
+    Buf = OB.getBuffer();
+  }
+
+  if (Status)
+    *Status = InternalStatus;
+  return InternalStatus == demangle_success ? Buf : nullptr;
+}