demangle: Update to llvm/llvm-project@ecbc812e0cca

externals/demangle/ItaniumDemangle.cpp

@@ -20,9 +20,7 @@
 #include <cstdlib>
 #include <cstring>
 #include <functional>
-#include <numeric>
 #include <utility>
-#include <vector>
 
 using namespace llvm;
 using namespace llvm::itanium_demangle;
@@ -81,8 +79,8 @@ struct DumpVisitor {
   }
 
   void printStr(const char *S) { fprintf(stderr, "%s", S); }
-  void print(StringView SV) {
-    fprintf(stderr, "\"%.*s\"", (int)SV.size(), SV.begin());
+  void print(std::string_view SV) {
+    fprintf(stderr, "\"%.*s\"", (int)SV.size(), SV.data());
   }
   void print(const Node *N) {
     if (N)
@@ -90,14 +88,6 @@ struct DumpVisitor {
     else
       printStr("<null>");
   }
-  void print(NodeOrString NS) {
-    if (NS.isNode())
-      print(NS.asNode());
-    else if (NS.isString())
-      print(NS.asString());
-    else
-      printStr("NodeOrString()");
-  }
   void print(NodeArray A) {
     ++Depth;
     printStr("{");
@@ -116,13 +106,11 @@ struct DumpVisitor {
   // Overload used when T is exactly 'bool', not merely convertible to 'bool'.
   void print(bool B) { printStr(B ? "true" : "false"); }
 
-  template <class T>
-  typename std::enable_if<std::is_unsigned<T>::value>::type print(T N) {
+  template <class T> std::enable_if_t<std::is_unsigned<T>::value> print(T N) {
     fprintf(stderr, "%llu", (unsigned long long)N);
   }
 
-  template <class T>
-  typename std::enable_if<std::is_signed<T>::value>::type print(T N) {
+  template <class T> std::enable_if_t<std::is_signed<T>::value> print(T N) {
     fprintf(stderr, "%lld", (long long)N);
   }
 
@@ -185,6 +173,50 @@ struct DumpVisitor {
       return printStr("TemplateParamKind::Template");
     }
   }
+  void print(Node::Prec P) {
+    switch (P) {
+    case Node::Prec::Primary:
+      return printStr("Node::Prec::Primary");
+    case Node::Prec::Postfix:
+      return printStr("Node::Prec::Postfix");
+    case Node::Prec::Unary:
+      return printStr("Node::Prec::Unary");
+    case Node::Prec::Cast:
+      return printStr("Node::Prec::Cast");
+    case Node::Prec::PtrMem:
+      return printStr("Node::Prec::PtrMem");
+    case Node::Prec::Multiplicative:
+      return printStr("Node::Prec::Multiplicative");
+    case Node::Prec::Additive:
+      return printStr("Node::Prec::Additive");
+    case Node::Prec::Shift:
+      return printStr("Node::Prec::Shift");
+    case Node::Prec::Spaceship:
+      return printStr("Node::Prec::Spaceship");
+    case Node::Prec::Relational:
+      return printStr("Node::Prec::Relational");
+    case Node::Prec::Equality:
+      return printStr("Node::Prec::Equality");
+    case Node::Prec::And:
+      return printStr("Node::Prec::And");
+    case Node::Prec::Xor:
+      return printStr("Node::Prec::Xor");
+    case Node::Prec::Ior:
+      return printStr("Node::Prec::Ior");
+    case Node::Prec::AndIf:
+      return printStr("Node::Prec::AndIf");
+    case Node::Prec::OrIf:
+      return printStr("Node::Prec::OrIf");
+    case Node::Prec::Conditional:
+      return printStr("Node::Prec::Conditional");
+    case Node::Prec::Assign:
+      return printStr("Node::Prec::Assign");
+    case Node::Prec::Comma:
+      return printStr("Node::Prec::Comma");
+    case Node::Prec::Default:
+      return printStr("Node::Prec::Default");
+    }
+  }
 
   void newLine() {
     printStr("\n");
@@ -334,36 +366,21 @@ public:
 
 using Demangler = itanium_demangle::ManglingParser<DefaultAllocator>;
 
-char *llvm::itaniumDemangle(const char *MangledName, char *Buf,
-                            size_t *N, int *Status) {
-  if (MangledName == nullptr || (Buf != nullptr && N == nullptr)) {
-    if (Status)
-      *Status = demangle_invalid_args;
+char *llvm::itaniumDemangle(std::string_view MangledName) {
+  if (MangledName.empty())
     return nullptr;
-  }
-
-  int InternalStatus = demangle_success;
-  Demangler Parser(MangledName, MangledName + std::strlen(MangledName));
-  OutputStream S;
 
+  Demangler Parser(MangledName.data(),
+                   MangledName.data() + MangledName.length());
   Node *AST = Parser.parse();
+  if (!AST)
+    return nullptr;
 
-  if (AST == nullptr)
-    InternalStatus = demangle_invalid_mangled_name;
-  else if (!initializeOutputStream(Buf, N, S, 1024))
-    InternalStatus = demangle_memory_alloc_failure;
-  else {
-    assert(Parser.ForwardTemplateRefs.empty());
-    AST->print(S);
-    S += '\0';
-    if (N != nullptr)
-      *N = S.getCurrentPosition();
-    Buf = S.getBuffer();
-  }
-
-  if (Status)
-    *Status = InternalStatus;
-  return InternalStatus == demangle_success ? Buf : nullptr;
+  OutputBuffer OB;
+  assert(Parser.ForwardTemplateRefs.empty());
+  AST->print(OB);
+  OB += '\0';
+  return OB.getBuffer();
 }
 
 ItaniumPartialDemangler::ItaniumPartialDemangler()
@@ -396,14 +413,12 @@ bool ItaniumPartialDemangler::partialDemangle(const char *MangledName) {
 }
 
 static char *printNode(const Node *RootNode, char *Buf, size_t *N) {
-  OutputStream S;
-  if (!initializeOutputStream(Buf, N, S, 128))
-    return nullptr;
-  RootNode->print(S);
-  S += '\0';
+  OutputBuffer OB(Buf, N);
+  RootNode->print(OB);
+  OB += '\0';
   if (N != nullptr)
-    *N = S.getCurrentPosition();
-  return S.getBuffer();
+    *N = OB.getCurrentPosition();
+  return OB.getBuffer();
 }
 
 char *ItaniumPartialDemangler::getFunctionBaseName(char *Buf, size_t *N) const {
@@ -417,8 +432,8 @@ char *ItaniumPartialDemangler::getFunctionBaseName(char *Buf, size_t *N) const {
     case Node::KAbiTagAttr:
       Name = static_cast<const AbiTagAttr *>(Name)->Base;
       continue;
-    case Node::KStdQualifiedName:
-      Name = static_cast<const StdQualifiedName *>(Name)->Child;
+    case Node::KModuleEntity:
+      Name = static_cast<const ModuleEntity *>(Name)->Name;
       continue;
     case Node::KNestedName:
       Name = static_cast<const NestedName *>(Name)->Name;
@@ -441,9 +456,7 @@ char *ItaniumPartialDemangler::getFunctionDeclContextName(char *Buf,
     return nullptr;
   const Node *Name = static_cast<const FunctionEncoding *>(RootNode)->getName();
 
-  OutputStream S;
-  if (!initializeOutputStream(Buf, N, S, 128))
-    return nullptr;
+  OutputBuffer OB(Buf, N);
 
  KeepGoingLocalFunction:
   while (true) {
@@ -458,27 +471,27 @@ char *ItaniumPartialDemangler::getFunctionDeclContextName(char *Buf,
     break;
   }
 
+  if (Name->getKind() == Node::KModuleEntity)
+    Name = static_cast<const ModuleEntity *>(Name)->Name;
+
   switch (Name->getKind()) {
-  case Node::KStdQualifiedName:
-    S += "std";
-    break;
   case Node::KNestedName:
-    static_cast<const NestedName *>(Name)->Qual->print(S);
+    static_cast<const NestedName *>(Name)->Qual->print(OB);
     break;
   case Node::KLocalName: {
     auto *LN = static_cast<const LocalName *>(Name);
-    LN->Encoding->print(S);
-    S += "::";
+    LN->Encoding->print(OB);
+    OB += "::";
     Name = LN->Entity;
     goto KeepGoingLocalFunction;
   }
   default:
     break;
   }
-  S += '\0';
+  OB += '\0';
   if (N != nullptr)
-    *N = S.getCurrentPosition();
-  return S.getBuffer();
+    *N = OB.getCurrentPosition();
+  return OB.getBuffer();
 }
 
 char *ItaniumPartialDemangler::getFunctionName(char *Buf, size_t *N) const {
@@ -494,17 +507,15 @@ char *ItaniumPartialDemangler::getFunctionParameters(char *Buf,
     return nullptr;
   NodeArray Params = static_cast<FunctionEncoding *>(RootNode)->getParams();
 
-  OutputStream S;
-  if (!initializeOutputStream(Buf, N, S, 128))
-    return nullptr;
+  OutputBuffer OB(Buf, N);
 
-  S += '(';
-  Params.printWithComma(S);
-  S += ')';
-  S += '\0';
+  OB += '(';
+  Params.printWithComma(OB);
+  OB += ')';
+  OB += '\0';
   if (N != nullptr)
-    *N = S.getCurrentPosition();
-  return S.getBuffer();
+    *N = OB.getCurrentPosition();
+  return OB.getBuffer();
 }
 
 char *ItaniumPartialDemangler::getFunctionReturnType(
@@ -512,18 +523,16 @@ char *ItaniumPartialDemangler::getFunctionReturnType(
   if (!isFunction())
     return nullptr;
 
-  OutputStream S;
-  if (!initializeOutputStream(Buf, N, S, 128))
-    return nullptr;
+  OutputBuffer OB(Buf, N);
 
   if (const Node *Ret =
           static_cast<const FunctionEncoding *>(RootNode)->getReturnType())
-    Ret->print(S);
+    Ret->print(OB);
 
-  S += '\0';
+  OB += '\0';
   if (N != nullptr)
-    *N = S.getCurrentPosition();
-  return S.getBuffer();
+    *N = OB.getCurrentPosition();
+  return OB.getBuffer();
 }
 
 char *ItaniumPartialDemangler::finishDemangle(char *Buf, size_t *N) const {
@@ -563,8 +572,8 @@ bool ItaniumPartialDemangler::isCtorOrDtor() const {
     case Node::KNestedName:
       N = static_cast<const NestedName *>(N)->Name;
       break;
-    case Node::KStdQualifiedName:
-      N = static_cast<const StdQualifiedName *>(N)->Child;
+    case Node::KModuleEntity:
+      N = static_cast<const ModuleEntity *>(N)->Name;
       break;
     }
   }

externals/demangle/llvm/Demangle/Demangle.h

@@ -12,6 +12,7 @@
 
 #include <cstddef>
 #include <string>
+#include <string_view>
 
 namespace llvm {
 /// This is a llvm local version of __cxa_demangle. Other than the name and
@@ -29,9 +30,10 @@ enum : int {
   demangle_success = 0,
 };
 
-char *itaniumDemangle(const char *mangled_name, char *buf, size_t *n,
-                      int *status);
-
+/// Returns a non-NULL pointer to a NUL-terminated C style string
+/// that should be explicitly freed, if successful. Otherwise, may return
+/// nullptr if mangled_name is not a valid mangling or is nullptr.
+char *itaniumDemangle(std::string_view mangled_name);
 
 enum MSDemangleFlags {
   MSDF_None = 0,
@@ -40,10 +42,34 @@ enum MSDemangleFlags {
   MSDF_NoCallingConvention = 1 << 2,
   MSDF_NoReturnType = 1 << 3,
   MSDF_NoMemberType = 1 << 4,
+  MSDF_NoVariableType = 1 << 5,
 };
-char *microsoftDemangle(const char *mangled_name, char *buf, size_t *n,
+
+/// Demangles the Microsoft symbol pointed at by mangled_name and returns it.
+/// Returns a pointer to the start of a null-terminated demangled string on
+/// success, or nullptr on error.
+/// If n_read is non-null and demangling was successful, it receives how many
+/// bytes of the input string were consumed.
+/// status receives one of the demangle_ enum entries above if it's not nullptr.
+/// Flags controls various details of the demangled representation.
+char *microsoftDemangle(std::string_view mangled_name, size_t *n_read,
                         int *status, MSDemangleFlags Flags = MSDF_None);
 
+// Demangles a Rust v0 mangled symbol.
+char *rustDemangle(std::string_view MangledName);
+
+// Demangles a D mangled symbol.
+char *dlangDemangle(std::string_view MangledName);
+
+/// Attempt to demangle a string using different demangling schemes.
+/// The function uses heuristics to determine which demangling scheme to use.
+/// \param MangledName - reference to string to demangle.
+/// \returns - the demangled string, or a copy of the input string if no
+/// demangling occurred.
+std::string demangle(std::string_view MangledName);
+
+bool nonMicrosoftDemangle(std::string_view MangledName, std::string &Result);
+
 /// "Partial" demangler. This supports demangling a string into an AST
 /// (typically an intermediate stage in itaniumDemangle) and querying certain
 /// properties or partially printing the demangled name.
@@ -59,7 +85,7 @@ struct ItaniumPartialDemangler {
   bool partialDemangle(const char *MangledName);
 
   /// Just print the entire mangled name into Buf. Buf and N behave like the
-  /// second and third parameters to itaniumDemangle.
+  /// second and third parameters to __cxa_demangle.
   char *finishDemangle(char *Buf, size_t *N) const;
 
   /// Get the base name of a function. This doesn't include trailing template
@@ -95,6 +121,7 @@ struct ItaniumPartialDemangler {
   bool isSpecialName() const;
 
   ~ItaniumPartialDemangler();
+
 private:
   void *RootNode;
   void *Context;

externals/demangle/llvm/Demangle/DemangleConfig.h

@@ -13,8 +13,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_DEMANGLE_COMPILER_H
-#define LLVM_DEMANGLE_COMPILER_H
+#ifndef LLVM_DEMANGLE_DEMANGLECONFIG_H
+#define LLVM_DEMANGLE_DEMANGLECONFIG_H
 
 #ifndef __has_feature
 #define __has_feature(x) 0

externals/demangle/llvm/Demangle/ItaniumNodes.def

@@ -0,0 +1,96 @@
+//===--- ItaniumNodes.def ------------*- mode:c++;eval:(read-only-mode) -*-===//
+//       Do not edit! See README.txt.
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-FileCopyrightText: Part of the LLVM Project
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Define the demangler's node names
+
+#ifndef NODE
+#error Define NODE to handle nodes
+#endif
+
+NODE(NodeArrayNode)
+NODE(DotSuffix)
+NODE(VendorExtQualType)
+NODE(QualType)
+NODE(ConversionOperatorType)
+NODE(PostfixQualifiedType)
+NODE(ElaboratedTypeSpefType)
+NODE(NameType)
+NODE(AbiTagAttr)
+NODE(EnableIfAttr)
+NODE(ObjCProtoName)
+NODE(PointerType)
+NODE(ReferenceType)
+NODE(PointerToMemberType)
+NODE(ArrayType)
+NODE(FunctionType)
+NODE(NoexceptSpec)
+NODE(DynamicExceptionSpec)
+NODE(FunctionEncoding)
+NODE(LiteralOperator)
+NODE(SpecialName)
+NODE(CtorVtableSpecialName)
+NODE(QualifiedName)
+NODE(NestedName)
+NODE(LocalName)
+NODE(ModuleName)
+NODE(ModuleEntity)
+NODE(VectorType)
+NODE(PixelVectorType)
+NODE(BinaryFPType)
+NODE(BitIntType)
+NODE(SyntheticTemplateParamName)
+NODE(TypeTemplateParamDecl)
+NODE(NonTypeTemplateParamDecl)
+NODE(TemplateTemplateParamDecl)
+NODE(TemplateParamPackDecl)
+NODE(ParameterPack)
+NODE(TemplateArgumentPack)
+NODE(ParameterPackExpansion)
+NODE(TemplateArgs)
+NODE(ForwardTemplateReference)
+NODE(NameWithTemplateArgs)
+NODE(GlobalQualifiedName)
+NODE(ExpandedSpecialSubstitution)
+NODE(SpecialSubstitution)
+NODE(CtorDtorName)
+NODE(DtorName)
+NODE(UnnamedTypeName)
+NODE(ClosureTypeName)
+NODE(StructuredBindingName)
+NODE(BinaryExpr)
+NODE(ArraySubscriptExpr)
+NODE(PostfixExpr)
+NODE(ConditionalExpr)
+NODE(MemberExpr)
+NODE(SubobjectExpr)
+NODE(EnclosingExpr)
+NODE(CastExpr)
+NODE(SizeofParamPackExpr)
+NODE(CallExpr)
+NODE(NewExpr)
+NODE(DeleteExpr)
+NODE(PrefixExpr)
+NODE(FunctionParam)
+NODE(ConversionExpr)
+NODE(PointerToMemberConversionExpr)
+NODE(InitListExpr)
+NODE(FoldExpr)
+NODE(ThrowExpr)
+NODE(BoolExpr)
+NODE(StringLiteral)
+NODE(LambdaExpr)
+NODE(EnumLiteral)
+NODE(IntegerLiteral)
+NODE(FloatLiteral)
+NODE(DoubleLiteral)
+NODE(LongDoubleLiteral)
+NODE(BracedExpr)
+NODE(BracedRangeExpr)
+
+#undef NODE

externals/demangle/llvm/Demangle/StringView.h

@@ -1,5 +1,5 @@
-//===--- StringView.h -------------------------------------------*- C++ -*-===//
-//
+//===--- StringView.h ----------------*- mode:c++;eval:(read-only-mode) -*-===//
+//       Do not edit! See README.txt.
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-FileCopyrightText: Part of the LLVM Project
@@ -8,6 +8,9 @@
 //===----------------------------------------------------------------------===//
 //
 // FIXME: Use std::string_view instead when we support C++17.
+// There are two copies of this file in the source tree.  The one under
+// libcxxabi is the original and the one under llvm is the copy.  Use
+// cp-to-llvm.sh to update the copy.  See README.txt for more details.
 //
 //===----------------------------------------------------------------------===//
 
@@ -15,7 +18,6 @@
 #define DEMANGLE_STRINGVIEW_H
 
 #include "DemangleConfig.h"
-#include <algorithm>
 #include <cassert>
 #include <cstring>
 
@@ -37,29 +39,23 @@ public:
   StringView(const char *Str) : First(Str), Last(Str + std::strlen(Str)) {}
   StringView() : First(nullptr), Last(nullptr) {}
 
-  StringView substr(size_t From) const {
-    return StringView(begin() + From, size() - From);
+  StringView substr(size_t Pos, size_t Len = npos) const {
+    assert(Pos <= size());
+    if (Len > size() - Pos)
+      Len = size() - Pos;
+    return StringView(begin() + Pos, Len);
   }
 
   size_t find(char C, size_t From = 0) const {
-    size_t FindBegin = std::min(From, size());
     // Avoid calling memchr with nullptr.
-    if (FindBegin < size()) {
+    if (From < size()) {
       // Just forward to memchr, which is faster than a hand-rolled loop.
-      if (const void *P = ::memchr(First + FindBegin, C, size() - FindBegin))
+      if (const void *P = ::memchr(First + From, C, size() - From))
         return size_t(static_cast<const char *>(P) - First);
     }
     return npos;
   }
 
-  StringView substr(size_t From, size_t To) const {
-    if (To >= size())
-      To = size() - 1;
-    if (From >= size())
-      From = size() - 1;
-    return StringView(First + From, First + To);
-  }
-
   StringView dropFront(size_t N = 1) const {
     if (N >= size())
       N = size();
@@ -106,7 +102,7 @@ public:
   bool startsWith(StringView Str) const {
     if (Str.size() > size())
       return false;
-    return std::equal(Str.begin(), Str.end(), begin());
+    return std::strncmp(Str.begin(), begin(), Str.size()) == 0;
   }
 
   const char &operator[](size_t Idx) const { return *(begin() + Idx); }
@@ -119,7 +115,7 @@ public:
 
 inline bool operator==(const StringView &LHS, const StringView &RHS) {
   return LHS.size() == RHS.size() &&
-         std::equal(LHS.begin(), LHS.end(), RHS.begin());
+         std::strncmp(LHS.begin(), RHS.begin(), LHS.size()) == 0;
 }
 
 DEMANGLE_NAMESPACE_END

externals/demangle/llvm/Demangle/StringViewExtras.h

@@ -0,0 +1,39 @@
+//===--- StringViewExtras.h ----------*- mode:c++;eval:(read-only-mode) -*-===//
+//       Do not edit! See README.txt.
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-FileCopyrightText: Part of the LLVM Project
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// There are two copies of this file in the source tree.  The one under
+// libcxxabi is the original and the one under llvm is the copy.  Use
+// cp-to-llvm.sh to update the copy.  See README.txt for more details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef DEMANGLE_STRINGVIEW_H
+#define DEMANGLE_STRINGVIEW_H
+
+#include "DemangleConfig.h"
+
+#include <string_view>
+
+DEMANGLE_NAMESPACE_BEGIN
+
+inline bool starts_with(std::string_view self, char C) noexcept {
+  return !self.empty() && *self.begin() == C;
+}
+
+inline bool starts_with(std::string_view haystack,
+                        std::string_view needle) noexcept {
+  if (needle.size() > haystack.size())
+    return false;
+  haystack.remove_suffix(haystack.size() - needle.size());
+  return haystack == needle;
+}
+
+DEMANGLE_NAMESPACE_END
+
+#endif

externals/demangle/llvm/Demangle/Utility.h

@@ -1,5 +1,5 @@
-//===--- Utility.h ----------------------------------------------*- C++ -*-===//
-//
+//===--- Utility.h -------------------*- mode:c++;eval:(read-only-mode) -*-===//
+//       Do not edit! See README.txt.
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-FileCopyrightText: Part of the LLVM Project
@@ -7,70 +7,83 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// Provide some utility classes for use in the demangler(s).
+// Provide some utility classes for use in the demangler.
+// There are two copies of this file in the source tree.  The one in libcxxabi
+// is the original and the one in llvm is the copy.  Use cp-to-llvm.sh to update
+// the copy.  See README.txt for more details.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef DEMANGLE_UTILITY_H
 #define DEMANGLE_UTILITY_H
 
-#include "StringView.h"
+#include "DemangleConfig.h"
+
+#include <array>
+#include <cassert>
 #include <cstdint>
 #include <cstdlib>
 #include <cstring>
-#include <iterator>
+#include <exception>
 #include <limits>
+#include <string_view>
 
 DEMANGLE_NAMESPACE_BEGIN
 
 // Stream that AST nodes write their string representation into after the AST
 // has been parsed.
-class OutputStream {
-  char *Buffer;
-  size_t CurrentPosition;
-  size_t BufferCapacity;
+class OutputBuffer {
+  char *Buffer = nullptr;
+  size_t CurrentPosition = 0;
+  size_t BufferCapacity = 0;
 
-  // Ensure there is at least n more positions in buffer.
+  // Ensure there are at least N more positions in the buffer.
   void grow(size_t N) {
-    if (N + CurrentPosition >= BufferCapacity) {
+    size_t Need = N + CurrentPosition;
+    if (Need > BufferCapacity) {
+      // Reduce the number of reallocations, with a bit of hysteresis. The
+      // number here is chosen so the first allocation will more-than-likely not
+      // allocate more than 1K.
+      Need += 1024 - 32;
       BufferCapacity *= 2;
-      if (BufferCapacity < N + CurrentPosition)
-        BufferCapacity = N + CurrentPosition;
+      if (BufferCapacity < Need)
+        BufferCapacity = Need;
       Buffer = static_cast<char *>(std::realloc(Buffer, BufferCapacity));
       if (Buffer == nullptr)
         std::terminate();
     }
   }
 
-  void writeUnsigned(uint64_t N, bool isNeg = false) {
-    // Handle special case...
-    if (N == 0) {
-      *this << '0';
-      return;
-    }
-
-    char Temp[21];
-    char *TempPtr = std::end(Temp);
+  OutputBuffer &writeUnsigned(uint64_t N, bool isNeg = false) {
+    std::array<char, 21> Temp;
+    char *TempPtr = Temp.data() + Temp.size();
 
-    while (N) {
-      *--TempPtr = '0' + char(N % 10);
+    // Output at least one character.
+    do {
+      *--TempPtr = char('0' + N % 10);
       N /= 10;
-    }
+    } while (N);
 
-    // Add negative sign...
+    // Add negative sign.
     if (isNeg)
       *--TempPtr = '-';
-    this->operator<<(StringView(TempPtr, std::end(Temp)));
+
+    return operator+=(
+        std::string_view(TempPtr, Temp.data() + Temp.size() - TempPtr));
   }
 
 public:
-  OutputStream(char *StartBuf, size_t Size)
-      : Buffer(StartBuf), CurrentPosition(0), BufferCapacity(Size) {}
-  OutputStream() = default;
-  void reset(char *Buffer_, size_t BufferCapacity_) {
-    CurrentPosition = 0;
-    Buffer = Buffer_;
-    BufferCapacity = BufferCapacity_;
+  OutputBuffer(char *StartBuf, size_t Size)
+      : Buffer(StartBuf), BufferCapacity(Size) {}
+  OutputBuffer(char *StartBuf, size_t *SizePtr)
+      : OutputBuffer(StartBuf, StartBuf ? *SizePtr : 0) {}
+  OutputBuffer() = default;
+  // Non-copyable
+  OutputBuffer(const OutputBuffer &) = delete;
+  OutputBuffer &operator=(const OutputBuffer &) = delete;
+
+  operator std::string_view() const {
+    return std::string_view(Buffer, CurrentPosition);
   }
 
   /// If a ParameterPackExpansion (or similar type) is encountered, the offset
@@ -78,115 +91,116 @@ public:
   unsigned CurrentPackIndex = std::numeric_limits<unsigned>::max();
   unsigned CurrentPackMax = std::numeric_limits<unsigned>::max();
 
-  OutputStream &operator+=(StringView R) {
-    size_t Size = R.size();
-    if (Size == 0)
-      return *this;
-    grow(Size);
-    std::memmove(Buffer + CurrentPosition, R.begin(), Size);
-    CurrentPosition += Size;
+  /// When zero, we're printing template args and '>' needs to be parenthesized.
+  /// Use a counter so we can simply increment inside parentheses.
+  unsigned GtIsGt = 1;
+
+  bool isGtInsideTemplateArgs() const { return GtIsGt == 0; }
+
+  void printOpen(char Open = '(') {
+    GtIsGt++;
+    *this += Open;
+  }
+  void printClose(char Close = ')') {
+    GtIsGt--;
+    *this += Close;
+  }
+
+  OutputBuffer &operator+=(std::string_view R) {
+    if (size_t Size = R.size()) {
+      grow(Size);
+      std::memcpy(Buffer + CurrentPosition, &*R.begin(), Size);
+      CurrentPosition += Size;
+    }
     return *this;
   }
 
-  OutputStream &operator+=(char C) {
+  OutputBuffer &operator+=(char C) {
     grow(1);
     Buffer[CurrentPosition++] = C;
     return *this;
   }
 
-  OutputStream &operator<<(StringView R) { return (*this += R); }
+  OutputBuffer &prepend(std::string_view R) {
+    size_t Size = R.size();
 
-  OutputStream &operator<<(char C) { return (*this += C); }
+    grow(Size);
+    std::memmove(Buffer + Size, Buffer, CurrentPosition);
+    std::memcpy(Buffer, &*R.begin(), Size);
+    CurrentPosition += Size;
 
-  OutputStream &operator<<(long long N) {
-    if (N < 0)
-      writeUnsigned(static_cast<unsigned long long>(-N), true);
-    else
-      writeUnsigned(static_cast<unsigned long long>(N));
     return *this;
   }
 
-  OutputStream &operator<<(unsigned long long N) {
-    writeUnsigned(N, false);
-    return *this;
+  OutputBuffer &operator<<(std::string_view R) { return (*this += R); }
+
+  OutputBuffer &operator<<(char C) { return (*this += C); }
+
+  OutputBuffer &operator<<(long long N) {
+    return writeUnsigned(static_cast<unsigned long long>(std::abs(N)), N < 0);
   }
 
-  OutputStream &operator<<(long N) {
+  OutputBuffer &operator<<(unsigned long long N) {
+    return writeUnsigned(N, false);
+  }
+
+  OutputBuffer &operator<<(long N) {
     return this->operator<<(static_cast<long long>(N));
   }
 
-  OutputStream &operator<<(unsigned long N) {
+  OutputBuffer &operator<<(unsigned long N) {
     return this->operator<<(static_cast<unsigned long long>(N));
   }
 
-  OutputStream &operator<<(int N) {
+  OutputBuffer &operator<<(int N) {
     return this->operator<<(static_cast<long long>(N));
   }
 
-  OutputStream &operator<<(unsigned int N) {
+  OutputBuffer &operator<<(unsigned int N) {
     return this->operator<<(static_cast<unsigned long long>(N));
   }
 
+  void insert(size_t Pos, const char *S, size_t N) {
+    assert(Pos <= CurrentPosition);
+    if (N == 0)
+      return;
+    grow(N);
+    std::memmove(Buffer + Pos + N, Buffer + Pos, CurrentPosition - Pos);
+    std::memcpy(Buffer + Pos, S, N);
+    CurrentPosition += N;
+  }
+
   size_t getCurrentPosition() const { return CurrentPosition; }
   void setCurrentPosition(size_t NewPos) { CurrentPosition = NewPos; }
 
   char back() const {
-    return CurrentPosition ? Buffer[CurrentPosition - 1] : '\0';
+    assert(CurrentPosition);
+    return Buffer[CurrentPosition - 1];
   }
 
   bool empty() const { return CurrentPosition == 0; }
 
   char *getBuffer() { return Buffer; }
   char *getBufferEnd() { return Buffer + CurrentPosition - 1; }
-  size_t getBufferCapacity() { return BufferCapacity; }
+  size_t getBufferCapacity() const { return BufferCapacity; }
 };
 
-template <class T> class SwapAndRestore {
-  T &Restore;
-  T OriginalValue;
-  bool ShouldRestore = true;
+template <class T> class ScopedOverride {
+  T &Loc;
+  T Original;
 
 public:
-  SwapAndRestore(T &Restore_) : SwapAndRestore(Restore_, Restore_) {}
-
-  SwapAndRestore(T &Restore_, T NewVal)
-      : Restore(Restore_), OriginalValue(Restore) {
-    Restore = std::move(NewVal);
-  }
-  ~SwapAndRestore() {
-    if (ShouldRestore)
-      Restore = std::move(OriginalValue);
-  }
+  ScopedOverride(T &Loc_) : ScopedOverride(Loc_, Loc_) {}
 
-  void shouldRestore(bool ShouldRestore_) { ShouldRestore = ShouldRestore_; }
-
-  void restoreNow(bool Force) {
-    if (!Force && !ShouldRestore)
-      return;
-
-    Restore = std::move(OriginalValue);
-    ShouldRestore = false;
+  ScopedOverride(T &Loc_, T NewVal) : Loc(Loc_), Original(Loc_) {
+    Loc_ = std::move(NewVal);
   }
+  ~ScopedOverride() { Loc = std::move(Original); }
 
-  SwapAndRestore(const SwapAndRestore &) = delete;
-  SwapAndRestore &operator=(const SwapAndRestore &) = delete;
+  ScopedOverride(const ScopedOverride &) = delete;
+  ScopedOverride &operator=(const ScopedOverride &) = delete;
 };
 
-inline bool initializeOutputStream(char *Buf, size_t *N, OutputStream &S,
-                                   size_t InitSize) {
-  size_t BufferSize;
-  if (Buf == nullptr) {
-    Buf = static_cast<char *>(std::malloc(InitSize));
-    if (Buf == nullptr)
-      return false;
-    BufferSize = InitSize;
-  } else
-    BufferSize = *N;
-
-  S.reset(Buf, BufferSize);
-  return true;
-}
-
 DEMANGLE_NAMESPACE_END
 
 #endif