//===--- Mangle.cpp - Mangle C++ Names --------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Implements C++ name mangling according to the Itanium C++ ABI,
// which is used in GCC 3.2 and newer (and many compilers that are
// ABI-compatible with GCC):
//
//   http://www.codesourcery.com/public/cxx-abi/abi.html
//
//===----------------------------------------------------------------------===//
#include "Mangle.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/ExprCXX.h"
#include "clang/Basic/SourceManager.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/ErrorHandling.h"
using namespace clang;

namespace {
  class VISIBILITY_HIDDEN CXXNameMangler {
    ASTContext &Context;
    llvm::raw_ostream &Out;

    const CXXMethodDecl *Structor;
    unsigned StructorType;
    CXXCtorType CtorType;

    llvm::DenseMap<uintptr_t, unsigned> Substitutions;
    
  public:
    CXXNameMangler(ASTContext &C, llvm::raw_ostream &os)
      : Context(C), Out(os), Structor(0), StructorType(0) { }

    bool mangle(const NamedDecl *D);
    void mangleCalloffset(int64_t nv, int64_t v);
    void mangleThunk(const FunctionDecl *FD, int64_t nv, int64_t v);
    void mangleCovariantThunk(const FunctionDecl *FD,
                              int64_t nv_t, int64_t v_t,
                              int64_t nv_r, int64_t v_r);
    void mangleGuardVariable(const VarDecl *D);

    void mangleCXXVtable(QualType Type);
    void mangleCXXRtti(QualType Type);
    void mangleCXXCtor(const CXXConstructorDecl *D, CXXCtorType Type);
    void mangleCXXDtor(const CXXDestructorDecl *D, CXXDtorType Type);

  private:
    bool mangleSubstitution(const NamedDecl *ND);
    bool mangleSubstitution(QualType T);
    bool mangleSubstitution(uintptr_t Ptr);
    
    bool mangleStandardSubstitution(const NamedDecl *ND);
    
    void addSubstitution(const NamedDecl *ND) {
      addSubstitution(reinterpret_cast<uintptr_t>(ND));
    }
    void addSubstitution(QualType T);
    void addSubstitution(uintptr_t Ptr);
    
    bool mangleFunctionDecl(const FunctionDecl *FD);

    void mangleFunctionEncoding(const FunctionDecl *FD);
    void mangleName(const NamedDecl *ND);
    void mangleName(const TemplateDecl *TD, 
                    const TemplateArgument *TemplateArgs,
                    unsigned NumTemplateArgs);
    void mangleUnqualifiedName(const NamedDecl *ND);
    void mangleUnscopedName(const NamedDecl *ND);
    void mangleUnscopedTemplateName(const TemplateDecl *ND);
    void mangleSourceName(const IdentifierInfo *II);
    void mangleLocalName(const NamedDecl *ND);
    void mangleNestedName(const NamedDecl *ND);
    void mangleNestedName(const TemplateDecl *TD, 
                          const TemplateArgument *TemplateArgs,
                          unsigned NumTemplateArgs);
    void manglePrefix(const DeclContext *DC);
    void mangleTemplatePrefix(const TemplateDecl *ND);
    void mangleOperatorName(OverloadedOperatorKind OO, unsigned Arity);
    void mangleQualifiers(Qualifiers Quals);
    void mangleType(QualType T);

    // Declare manglers for every type class.
#define ABSTRACT_TYPE(CLASS, PARENT)
#define NON_CANONICAL_TYPE(CLASS, PARENT)
#define TYPE(CLASS, PARENT) void mangleType(const CLASS##Type *T);
#include "clang/AST/TypeNodes.def"

    void mangleType(const TagType*);
    void mangleBareFunctionType(const FunctionType *T,
                                bool MangleReturnType);
    void mangleExpression(const Expr *E);
    void mangleCXXCtorType(CXXCtorType T);
    void mangleCXXDtorType(CXXDtorType T);

    void mangleTemplateArgs(const TemplateArgument *TemplateArgs,
                            unsigned NumTemplateArgs);
    void mangleTemplateArgumentList(const TemplateArgumentList &L);
    void mangleTemplateArgument(const TemplateArgument &A);
    
    void mangleTemplateParameter(unsigned Index);
  };
}

static bool isInCLinkageSpecification(const Decl *D) {
  for (const DeclContext *DC = D->getDeclContext();
       !DC->isTranslationUnit(); DC = DC->getParent()) {
    if (const LinkageSpecDecl *Linkage = dyn_cast<LinkageSpecDecl>(DC))
      return Linkage->getLanguage() == LinkageSpecDecl::lang_c;
  }

  return false;
}

bool CXXNameMangler::mangleFunctionDecl(const FunctionDecl *FD) {
  // Clang's "overloadable" attribute extension to C/C++ implies name mangling
  // (always).
  if (!FD->hasAttr<OverloadableAttr>()) {
    // C functions are not mangled, and "main" is never mangled.
    if (!Context.getLangOptions().CPlusPlus || FD->isMain())
      return false;

    // No mangling in an "implicit extern C" header.
    if (FD->getLocation().isValid() &&
        Context.getSourceManager().isInExternCSystemHeader(FD->getLocation()))
      return false;

    // No name mangling in a C linkage specification.
    if (!isa<CXXMethodDecl>(FD) && isInCLinkageSpecification(FD))
      return false;
  }

  // If we get here, mangle the decl name!
  Out << "_Z";
  mangleFunctionEncoding(FD);
  return true;
}

bool CXXNameMangler::mangle(const NamedDecl *D) {
  // Any decl can be declared with __asm("foo") on it, and this takes precedence
  // over all other naming in the .o file.
  if (const AsmLabelAttr *ALA = D->getAttr<AsmLabelAttr>()) {
    // If we have an asm name, then we use it as the mangling.
    Out << '\01';  // LLVM IR Marker for __asm("foo")
    Out << ALA->getLabel();
    return true;
  }

  // <mangled-name> ::= _Z <encoding>
  //            ::= <data name>
  //            ::= <special-name>

  // FIXME: Actually use a visitor to decode these?
  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D))
    return mangleFunctionDecl(FD);

  if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
    if (!Context.getLangOptions().CPlusPlus ||
        isInCLinkageSpecification(D) ||
        D->getDeclContext()->isTranslationUnit())
      return false;

    Out << "_Z";
    mangleName(VD);
    return true;
  }

  return false;
}

void CXXNameMangler::mangleCXXCtor(const CXXConstructorDecl *D,
                                   CXXCtorType Type) {
  assert(!Structor && "Structor already set!");
  Structor = D;
  StructorType = Type;

  mangle(D);
}

void CXXNameMangler::mangleCXXDtor(const CXXDestructorDecl *D,
                                   CXXDtorType Type) {
  assert(!Structor && "Structor already set!");
  Structor = D;
  StructorType = Type;

  mangle(D);
}

void CXXNameMangler::mangleCXXVtable(QualType T) {
  // <special-name> ::= TV <type>  # virtual table
  Out << "_ZTV";
  mangleType(T);
}

void CXXNameMangler::mangleCXXRtti(QualType T) {
  // <special-name> ::= TI <type>  # typeinfo structure
  Out << "_ZTI";
  mangleType(T);
}

void CXXNameMangler::mangleGuardVariable(const VarDecl *D) {
  //  <special-name> ::= GV <object name>       # Guard variable for one-time
  //                                            # initialization

  Out << "_ZGV";
  mangleName(D);
}

void CXXNameMangler::mangleFunctionEncoding(const FunctionDecl *FD) {
  // <encoding> ::= <function name> <bare-function-type>
  mangleName(FD);

  // Whether the mangling of a function type includes the return type depends on
  // the context and the nature of the function. The rules for deciding whether
  // the return type is included are:
  //
  //   1. Template functions (names or types) have return types encoded, with
  //   the exceptions listed below.
  //   2. Function types not appearing as part of a function name mangling,
  //   e.g. parameters, pointer types, etc., have return type encoded, with the
  //   exceptions listed below.
  //   3. Non-template function names do not have return types encoded.
  //
  // The exceptions mentioned in (1) and (2) above, for which the return type is
  // never included, are
  //   1. Constructors.
  //   2. Destructors.
  //   3. Conversion operator functions, e.g. operator int.
  bool MangleReturnType = false;
  if (FunctionTemplateDecl *PrimaryTemplate = FD->getPrimaryTemplate()) {
    if (!(isa<CXXConstructorDecl>(FD) || isa<CXXDestructorDecl>(FD) ||
          isa<CXXConversionDecl>(FD)))
      MangleReturnType = true;
    
    // Mangle the type of the primary template.
    FD = PrimaryTemplate->getTemplatedDecl();
  }

  mangleBareFunctionType(FD->getType()->getAs<FunctionType>(), MangleReturnType);
}

static bool isStdNamespace(const DeclContext *DC) {
  if (!DC->isNamespace() || !DC->getParent()->isTranslationUnit())
    return false;

  const NamespaceDecl *NS = cast<NamespaceDecl>(DC);
  const IdentifierInfo *II = NS->getOriginalNamespace()->getIdentifier();
  return II && II->isStr("std");
}

static const TemplateDecl *
isTemplate(const NamedDecl *ND, const TemplateArgumentList *&TemplateArgs) {
  // Check if we have a function template.
  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND)){
    if (const TemplateDecl *TD = FD->getPrimaryTemplate()) {
      TemplateArgs = FD->getTemplateSpecializationArgs();
      return TD;
    }
  }

  // Check if we have a class template.
  if (const ClassTemplateSpecializationDecl *Spec =
        dyn_cast<ClassTemplateSpecializationDecl>(ND)) {
    TemplateArgs = &Spec->getTemplateArgs();
    return Spec->getSpecializedTemplate();
  }
    
  return 0;
}

void CXXNameMangler::mangleName(const NamedDecl *ND) {
  //  <name> ::= <nested-name>
  //         ::= <unscoped-name>
  //         ::= <unscoped-template-name> <template-args>
  //         ::= <local-name>
  //
  const DeclContext *DC = ND->getDeclContext();
  while (isa<LinkageSpecDecl>(DC))
    DC = DC->getParent();
  
  if (DC->isTranslationUnit() || isStdNamespace(DC)) {
    // Check if we have a template.
    const TemplateArgumentList *TemplateArgs = 0;
    if (const TemplateDecl *TD = isTemplate(ND, TemplateArgs)) {
      mangleUnscopedTemplateName(TD);
      mangleTemplateArgumentList(*TemplateArgs);
      return;
    }

    mangleUnscopedName(ND);
    return;
  }
  
  if (isa<FunctionDecl>(DC)) {
    mangleLocalName(ND);
    return;
  }
  
  mangleNestedName(ND);
}
void CXXNameMangler::mangleName(const TemplateDecl *TD, 
                                const TemplateArgument *TemplateArgs,
                                unsigned NumTemplateArgs) {
  const DeclContext *DC = TD->getDeclContext();
  while (isa<LinkageSpecDecl>(DC)) {
    assert(cast<LinkageSpecDecl>(DC)->getLanguage() == 
           LinkageSpecDecl::lang_cxx && "Unexpected linkage decl!");
    DC = DC->getParent();
  }
 
  if (DC->isTranslationUnit() || isStdNamespace(DC)) {
    mangleUnscopedTemplateName(TD);
    mangleTemplateArgs(TemplateArgs, NumTemplateArgs);
  } else {
    mangleNestedName(TD, TemplateArgs, NumTemplateArgs);
  }
}

void CXXNameMangler::mangleUnscopedName(const NamedDecl *ND) {
  //  <unscoped-name> ::= <unqualified-name>
  //                  ::= St <unqualified-name>   # ::std::
  if (isStdNamespace(ND->getDeclContext()))
    Out << "St";
  
  mangleUnqualifiedName(ND);
}

void CXXNameMangler::mangleUnscopedTemplateName(const TemplateDecl *ND) {
  //     <unscoped-template-name> ::= <unscoped-name>
  //                              ::= <substitution>
  if (mangleSubstitution(ND))
    return;
  
  mangleUnscopedName(ND->getTemplatedDecl());
  addSubstitution(ND);
}

void CXXNameMangler::mangleCalloffset(int64_t nv, int64_t v) {
  //  <call-offset>  ::= h <nv-offset> _
  //                 ::= v <v-offset> _
  //  <nv-offset>    ::= <offset number>        # non-virtual base override
  //  <v-offset>     ::= <offset nubmer> _ <virtual offset number>
  //                      # virtual base override, with vcall offset
  if (v == 0) {
    Out << "h";
    if (nv < 0) {
      Out << "n";
      nv = -nv;
    }
    Out << nv;
  } else {
    Out << "v";
    if (nv < 0) {
      Out << "n";
      nv = -nv;
    }
    Out << nv;
    Out << "_";
    if (v < 0) {
      Out << "n";
      v = -v;
    }
    Out << v;
  }
  Out << "_";
}

void CXXNameMangler::mangleThunk(const FunctionDecl *FD, int64_t nv,
                                 int64_t v) {
  //  <special-name> ::= T <call-offset> <base encoding>
  //                      # base is the nominal target function of thunk
  Out << "_ZT";
  mangleCalloffset(nv, v);
  mangleFunctionEncoding(FD);
}

  void CXXNameMangler::mangleCovariantThunk(const FunctionDecl *FD,
                                            int64_t nv_t, int64_t v_t,
                                            int64_t nv_r, int64_t v_r) {
  //  <special-name> ::= Tc <call-offset> <call-offset> <base encoding>
  //                      # base is the nominal target function of thunk
  //                      # first call-offset is 'this' adjustment
  //                      # second call-offset is result adjustment
  Out << "_ZTc";
  mangleCalloffset(nv_t, v_t);
  mangleCalloffset(nv_r, v_r);
  mangleFunctionEncoding(FD);
}

void CXXNameMangler::mangleUnqualifiedName(const NamedDecl *ND) {
  //  <unqualified-name> ::= <operator-name>
  //                     ::= <ctor-dtor-name>
  //                     ::= <source-name>
  DeclarationName Name = ND->getDeclName();
  switch (Name.getNameKind()) {
  case DeclarationName::Identifier:
    if (const NamespaceDecl *NS = dyn_cast<NamespaceDecl>(ND))
      if (NS->isAnonymousNamespace()) {
        // This is how gcc mangles these names.  It's apparently
        // always '1', no matter how many different anonymous
        // namespaces appear in a context.
        Out << "12_GLOBAL__N_1";
        break;
      }
    mangleSourceName(Name.getAsIdentifierInfo());
    break;

  case DeclarationName::ObjCZeroArgSelector:
  case DeclarationName::ObjCOneArgSelector:
  case DeclarationName::ObjCMultiArgSelector:
    assert(false && "Can't mangle Objective-C selector names here!");
    break;

  case DeclarationName::CXXConstructorName:
    if (ND == Structor)
      // If the named decl is the C++ constructor we're mangling, use the type
      // we were given.
      mangleCXXCtorType(static_cast<CXXCtorType>(StructorType));
    else
      // Otherwise, use the complete constructor name. This is relevant if a
      // class with a constructor is declared within a constructor.
      mangleCXXCtorType(Ctor_Complete);
    break;

  case DeclarationName::CXXDestructorName:
    if (ND == Structor)
      // If the named decl is the C++ destructor we're mangling, use the type we
      // were given.
      mangleCXXDtorType(static_cast<CXXDtorType>(StructorType));
    else
      // Otherwise, use the complete destructor name. This is relevant if a
      // class with a destructor is declared within a destructor.
      mangleCXXDtorType(Dtor_Complete);
    break;

  case DeclarationName::CXXConversionFunctionName:
    // <operator-name> ::= cv <type>    # (cast)
    Out << "cv";
    mangleType(Context.getCanonicalType(Name.getCXXNameType()));
    break;

  case DeclarationName::CXXOperatorName:
    mangleOperatorName(Name.getCXXOverloadedOperator(),
                       cast<FunctionDecl>(ND)->getNumParams());
    break;

  case DeclarationName::CXXUsingDirective:
    assert(false && "Can't mangle a using directive name!");
    break;
  }
}

void CXXNameMangler::mangleSourceName(const IdentifierInfo *II) {
  // <source-name> ::= <positive length number> <identifier>
  // <number> ::= [n] <non-negative decimal integer>
  // <identifier> ::= <unqualified source code identifier>
  Out << II->getLength() << II->getName();
}

void CXXNameMangler::mangleNestedName(const NamedDecl *ND) {
  // <nested-name> ::= N [<CV-qualifiers>] <prefix> <unqualified-name> E
  //               ::= N [<CV-qualifiers>] <template-prefix> <template-args> E

  Out << 'N';
  if (const CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(ND))
    mangleQualifiers(Qualifiers::fromCVRMask(Method->getTypeQualifiers()));
  
  // Check if we have a template.
  const TemplateArgumentList *TemplateArgs = 0;
  if (const TemplateDecl *TD = isTemplate(ND, TemplateArgs)) { 
    mangleTemplatePrefix(TD);
    mangleTemplateArgumentList(*TemplateArgs);
  } else {
    manglePrefix(ND->getDeclContext());
    mangleUnqualifiedName(ND);
  }
  
  Out << 'E';
}
void CXXNameMangler::mangleNestedName(const TemplateDecl *TD, 
                                      const TemplateArgument *TemplateArgs,
                                      unsigned NumTemplateArgs) {
  // <nested-name> ::= N [<CV-qualifiers>] <template-prefix> <template-args> E

  Out << 'N';
  
  mangleTemplatePrefix(TD);
  mangleTemplateArgs(TemplateArgs, NumTemplateArgs);
  
  Out << 'E';
}

void CXXNameMangler::mangleLocalName(const NamedDecl *ND) {
  // <local-name> := Z <function encoding> E <entity name> [<discriminator>]
  //              := Z <function encoding> E s [<discriminator>]
  // <discriminator> := _ <non-negative number>
  Out << 'Z';
  mangleFunctionEncoding(cast<FunctionDecl>(ND->getDeclContext()));
  Out << 'E';
  mangleSourceName(ND->getIdentifier());
}

void CXXNameMangler::manglePrefix(const DeclContext *DC) {
  //  <prefix> ::= <prefix> <unqualified-name>
  //           ::= <template-prefix> <template-args>
  //           ::= <template-param>
  //           ::= # empty
  //           ::= <substitution>
  // FIXME: We only handle mangling of namespaces and classes at the moment.

  while (isa<LinkageSpecDecl>(DC))
    DC = DC->getParent();
  
  if (DC->isTranslationUnit())
    return;
  
  if (mangleSubstitution(cast<NamedDecl>(DC)))
    return;

  // Check if we have a template.
  const TemplateArgumentList *TemplateArgs = 0;
  if (const TemplateDecl *TD = isTemplate(cast<NamedDecl>(DC), TemplateArgs)) { 
    mangleTemplatePrefix(TD);
    mangleTemplateArgumentList(*TemplateArgs);
  } else {
    manglePrefix(DC->getParent());
    mangleUnqualifiedName(cast<NamedDecl>(DC));
  }
  
  addSubstitution(cast<NamedDecl>(DC));
}

void CXXNameMangler::mangleTemplatePrefix(const TemplateDecl *ND) {
  // <template-prefix> ::= <prefix> <template unqualified-name>
  //                   ::= <template-param>
  //                   ::= <substitution>

  if (mangleSubstitution(ND))
    return;
  
  // FIXME: <template-param>
  
  manglePrefix(ND->getDeclContext());
  mangleUnqualifiedName(ND->getTemplatedDecl());
  
  addSubstitution(ND);
}

void
CXXNameMangler::mangleOperatorName(OverloadedOperatorKind OO, unsigned Arity) {
  switch (OO) {
  // <operator-name> ::= nw     # new
  case OO_New: Out << "nw"; break;
  //              ::= na        # new[]
  case OO_Array_New: Out << "na"; break;
  //              ::= dl        # delete
  case OO_Delete: Out << "dl"; break;
  //              ::= da        # delete[]
  case OO_Array_Delete: Out << "da"; break;
  //              ::= ps        # + (unary)
  //              ::= pl        # +
  case OO_Plus: Out << (Arity == 1? "ps" : "pl"); break;
  //              ::= ng        # - (unary)
  //              ::= mi        # -
  case OO_Minus: Out << (Arity == 1? "ng" : "mi"); break;
  //              ::= ad        # & (unary)
  //              ::= an        # &
  case OO_Amp: Out << (Arity == 1? "ad" : "an"); break;
  //              ::= de        # * (unary)
  //              ::= ml        # *
  case OO_Star: Out << (Arity == 1? "de" : "ml"); break;
  //              ::= co        # ~
  case OO_Tilde: Out << "co"; break;
  //              ::= dv        # /
  case OO_Slash: Out << "dv"; break;
  //              ::= rm        # %
  case OO_Percent: Out << "rm"; break;
  //              ::= or        # |
  case OO_Pipe: Out << "or"; break;
  //              ::= eo        # ^
  case OO_Caret: Out << "eo"; break;
  //              ::= aS        # =
  case OO_Equal: Out << "aS"; break;
  //              ::= pL        # +=
  case OO_PlusEqual: Out << "pL"; break;
  //              ::= mI        # -=
  case OO_MinusEqual: Out << "mI"; break;
  //              ::= mL        # *=
  case OO_StarEqual: Out << "mL"; break;
  //              ::= dV        # /=
  case OO_SlashEqual: Out << "dV"; break;
  //              ::= rM        # %=
  case OO_PercentEqual: Out << "rM"; break;
  //              ::= aN        # &=
  case OO_AmpEqual: Out << "aN"; break;
  //              ::= oR        # |=
  case OO_PipeEqual: Out << "oR"; break;
  //              ::= eO        # ^=
  case OO_CaretEqual: Out << "eO"; break;
  //              ::= ls        # <<
  case OO_LessLess: Out << "ls"; break;
  //              ::= rs        # >>
  case OO_GreaterGreater: Out << "rs"; break;
  //              ::= lS        # <<=
  case OO_LessLessEqual: Out << "lS"; break;
  //              ::= rS        # >>=
  case OO_GreaterGreaterEqual: Out << "rS"; break;
  //              ::= eq        # ==
  case OO_EqualEqual: Out << "eq"; break;
  //              ::= ne        # !=
  case OO_ExclaimEqual: Out << "ne"; break;
  //              ::= lt        # <
  case OO_Less: Out << "lt"; break;
  //              ::= gt        # >
  case OO_Greater: Out << "gt"; break;
  //              ::= le        # <=
  case OO_LessEqual: Out << "le"; break;
  //              ::= ge        # >=
  case OO_GreaterEqual: Out << "ge"; break;
  //              ::= nt        # !
  case OO_Exclaim: Out << "nt"; break;
  //              ::= aa        # &&
  case OO_AmpAmp: Out << "aa"; break;
  //              ::= oo        # ||
  case OO_PipePipe: Out << "oo"; break;
  //              ::= pp        # ++
  case OO_PlusPlus: Out << "pp"; break;
  //              ::= mm        # --
  case OO_MinusMinus: Out << "mm"; break;
  //              ::= cm        # ,
  case OO_Comma: Out << "cm"; break;
  //              ::= pm        # ->*
  case OO_ArrowStar: Out << "pm"; break;
  //              ::= pt        # ->
  case OO_Arrow: Out << "pt"; break;
  //              ::= cl        # ()
  case OO_Call: Out << "cl"; break;
  //              ::= ix        # []
  case OO_Subscript: Out << "ix"; break;
  // UNSUPPORTED: ::= qu        # ?

  case OO_None:
  case OO_Conditional:
  case NUM_OVERLOADED_OPERATORS:
    assert(false && "Not an overloaded operator");
    break;
  }
}

void CXXNameMangler::mangleQualifiers(Qualifiers Quals) {
  // <CV-qualifiers> ::= [r] [V] [K]    # restrict (C99), volatile, const
  if (Quals.hasRestrict())
    Out << 'r';
  if (Quals.hasVolatile())
    Out << 'V';
  if (Quals.hasConst())
    Out << 'K';

  // FIXME: For now, just drop all extension qualifiers on the floor.
}

void CXXNameMangler::mangleType(QualType T) {
  // Only operate on the canonical type!
  T = Context.getCanonicalType(T);

  bool IsSubstitutable = !isa<BuiltinType>(T);
  if (IsSubstitutable && mangleSubstitution(T))
    return;

  if (Qualifiers Quals = T.getQualifiers()) {
    mangleQualifiers(Quals);
    // Recurse:  even if the qualified type isn't yet substitutable,
    // the unqualified type might be.
    mangleType(T.getUnqualifiedType());
  } else {
    switch (T->getTypeClass()) {
#define ABSTRACT_TYPE(CLASS, PARENT)
#define NON_CANONICAL_TYPE(CLASS, PARENT) \
    case Type::CLASS: \
      llvm::llvm_unreachable("can't mangle non-canonical type " #CLASS "Type"); \
      return;
#define TYPE(CLASS, PARENT) \
    case Type::CLASS: \
      mangleType(static_cast<const CLASS##Type*>(T.getTypePtr())); \
      break;
#include "clang/AST/TypeNodes.def"
    }
  }

  // Add the substitution.
  if (IsSubstitutable)
    addSubstitution(T);
}

void CXXNameMangler::mangleType(const BuiltinType *T) {
  //  <type>         ::= <builtin-type>
  //  <builtin-type> ::= v  # void
  //                 ::= w  # wchar_t
  //                 ::= b  # bool
  //                 ::= c  # char
  //                 ::= a  # signed char
  //                 ::= h  # unsigned char
  //                 ::= s  # short
  //                 ::= t  # unsigned short
  //                 ::= i  # int
  //                 ::= j  # unsigned int
  //                 ::= l  # long
  //                 ::= m  # unsigned long
  //                 ::= x  # long long, __int64
  //                 ::= y  # unsigned long long, __int64
  //                 ::= n  # __int128
  // UNSUPPORTED:    ::= o  # unsigned __int128
  //                 ::= f  # float
  //                 ::= d  # double
  //                 ::= e  # long double, __float80
  // UNSUPPORTED:    ::= g  # __float128
  // UNSUPPORTED:    ::= Dd # IEEE 754r decimal floating point (64 bits)
  // UNSUPPORTED:    ::= De # IEEE 754r decimal floating point (128 bits)
  // UNSUPPORTED:    ::= Df # IEEE 754r decimal floating point (32 bits)
  // UNSUPPORTED:    ::= Dh # IEEE 754r half-precision floating point (16 bits)
  //                 ::= Di # char32_t
  //                 ::= Ds # char16_t
  //                 ::= u <source-name>    # vendor extended type
  // From our point of view, std::nullptr_t is a builtin, but as far as mangling
  // is concerned, it's a type called std::nullptr_t.
  switch (T->getKind()) {
  case BuiltinType::Void: Out << 'v'; break;
  case BuiltinType::Bool: Out << 'b'; break;
  case BuiltinType::Char_U: case BuiltinType::Char_S: Out << 'c'; break;
  case BuiltinType::UChar: Out << 'h'; break;
  case BuiltinType::UShort: Out << 't'; break;
  case BuiltinType::UInt: Out << 'j'; break;
  case BuiltinType::ULong: Out << 'm'; break;
  case BuiltinType::ULongLong: Out << 'y'; break;
  case BuiltinType::UInt128: Out << 'o'; break;
  case BuiltinType::SChar: Out << 'a'; break;
  case BuiltinType::WChar: Out << 'w'; break;
  case BuiltinType::Char16: Out << "Ds"; break;
  case BuiltinType::Char32: Out << "Di"; break;
  case BuiltinType::Short: Out << 's'; break;
  case BuiltinType::Int: Out << 'i'; break;
  case BuiltinType::Long: Out << 'l'; break;
  case BuiltinType::LongLong: Out << 'x'; break;
  case BuiltinType::Int128: Out << 'n'; break;
  case BuiltinType::Float: Out << 'f'; break;
  case BuiltinType::Double: Out << 'd'; break;
  case BuiltinType::LongDouble: Out << 'e'; break;
  case BuiltinType::NullPtr: Out << "St9nullptr_t"; break;

  case BuiltinType::Overload:
  case BuiltinType::Dependent:
    assert(false &&
           "Overloaded and dependent types shouldn't get to name mangling");
    break;
  case BuiltinType::UndeducedAuto:
    assert(0 && "Should not see undeduced auto here");
    break;
  case BuiltinType::ObjCId: Out << "11objc_object"; break;
  case BuiltinType::ObjCClass: Out << "10objc_class"; break;
  }
}

// <type>          ::= <function-type>
// <function-type> ::= F [Y] <bare-function-type> E
void CXXNameMangler::mangleType(const FunctionProtoType *T) {
  Out << 'F';
  // FIXME: We don't have enough information in the AST to produce the 'Y'
  // encoding for extern "C" function types.
  mangleBareFunctionType(T, /*MangleReturnType=*/true);
  Out << 'E';
}
void CXXNameMangler::mangleType(const FunctionNoProtoType *T) {
  llvm::llvm_unreachable("Can't mangle K&R function prototypes");
}
void CXXNameMangler::mangleBareFunctionType(const FunctionType *T,
                                            bool MangleReturnType) {
  // We should never be mangling something without a prototype.
  const FunctionProtoType *Proto = cast<FunctionProtoType>(T);

  // <bare-function-type> ::= <signature type>+
  if (MangleReturnType)
    mangleType(Proto->getResultType());

  if (Proto->getNumArgs() == 0) {
    Out << 'v';
    return;
  }

  for (FunctionProtoType::arg_type_iterator Arg = Proto->arg_type_begin(),
                                         ArgEnd = Proto->arg_type_end();
       Arg != ArgEnd; ++Arg)
    mangleType(*Arg);

  // <builtin-type>      ::= z  # ellipsis
  if (Proto->isVariadic())
    Out << 'z';
}

// <type>            ::= <class-enum-type>
// <class-enum-type> ::= <name>
void CXXNameMangler::mangleType(const EnumType *T) {
  mangleType(static_cast<const TagType*>(T));
}
void CXXNameMangler::mangleType(const RecordType *T) {
  mangleType(static_cast<const TagType*>(T));
}
void CXXNameMangler::mangleType(const TagType *T) {
  if (!T->getDecl()->getIdentifier())
    mangleName(T->getDecl()->getTypedefForAnonDecl());
  else
    mangleName(T->getDecl());
}

// <type>       ::= <array-type>
// <array-type> ::= A <positive dimension number> _ <element type>
//              ::= A [<dimension expression>] _ <element type>
void CXXNameMangler::mangleType(const ConstantArrayType *T) {
  Out << 'A' << T->getSize() << '_';
  mangleType(T->getElementType());
}
void CXXNameMangler::mangleType(const VariableArrayType *T) {
  Out << 'A';
  mangleExpression(T->getSizeExpr());
  Out << '_';
  mangleType(T->getElementType());
}
void CXXNameMangler::mangleType(const DependentSizedArrayType *T) {
  Out << 'A';
  mangleExpression(T->getSizeExpr());
  Out << '_';
  mangleType(T->getElementType());
}
void CXXNameMangler::mangleType(const IncompleteArrayType *T) {
  Out << 'A' << '_';
  mangleType(T->getElementType());
}

// <type>                   ::= <pointer-to-member-type>
// <pointer-to-member-type> ::= M <class type> <member type>
void CXXNameMangler::mangleType(const MemberPointerType *T) {
  Out << 'M';
  mangleType(QualType(T->getClass(), 0));
  QualType PointeeType = T->getPointeeType();
  if (const FunctionProtoType *FPT = dyn_cast<FunctionProtoType>(PointeeType)) {
    mangleQualifiers(Qualifiers::fromCVRMask(FPT->getTypeQuals()));
    mangleType(FPT);
  } else
    mangleType(PointeeType);
}

// <type>           ::= <template-param>
void CXXNameMangler::mangleType(const TemplateTypeParmType *T) {
  mangleTemplateParameter(T->getIndex());
}

// FIXME: <type> ::= <template-template-param> <template-args>

// <type> ::= P <type>   # pointer-to
void CXXNameMangler::mangleType(const PointerType *T) {
  Out << 'P';
  mangleType(T->getPointeeType());
}
void CXXNameMangler::mangleType(const ObjCObjectPointerType *T) {
  Out << 'P';
  mangleType(T->getPointeeType());
}

// <type> ::= R <type>   # reference-to
void CXXNameMangler::mangleType(const LValueReferenceType *T) {
  Out << 'R';
  mangleType(T->getPointeeType());
}

// <type> ::= O <type>   # rvalue reference-to (C++0x)
void CXXNameMangler::mangleType(const RValueReferenceType *T) {
  Out << 'O';
  mangleType(T->getPointeeType());
}

// <type> ::= C <type>   # complex pair (C 2000)
void CXXNameMangler::mangleType(const ComplexType *T) {
  Out << 'C';
  mangleType(T->getElementType());
}

// GNU extension: vector types
void CXXNameMangler::mangleType(const VectorType *T) {
  Out << "U8__vector";
  mangleType(T->getElementType());
}
void CXXNameMangler::mangleType(const ExtVectorType *T) {
  mangleType(static_cast<const VectorType*>(T));
}
void CXXNameMangler::mangleType(const DependentSizedExtVectorType *T) {
  Out << "U8__vector";
  mangleType(T->getElementType());
}

void CXXNameMangler::mangleType(const ObjCInterfaceType *T) {
  mangleSourceName(T->getDecl()->getIdentifier());
}

void CXXNameMangler::mangleType(const BlockPointerType *T) {
  assert(false && "can't mangle block pointer types yet");
}

void CXXNameMangler::mangleType(const FixedWidthIntType *T) {
  assert(false && "can't mangle arbitary-precision integer type yet");
}

void CXXNameMangler::mangleType(const TemplateSpecializationType *T) {
  TemplateDecl *TD = T->getTemplateName().getAsTemplateDecl();
  assert(TD && "FIXME: Support dependent template names!");
  
  mangleName(TD, T->getArgs(), T->getNumArgs());
}

void CXXNameMangler::mangleType(const TypenameType *T) {
  // Typename types are always nested
  Out << 'N';

  const Type *QTy = T->getQualifier()->getAsType();
  if (const TemplateSpecializationType *TST = 
        dyn_cast<TemplateSpecializationType>(QTy)) {
    if (!mangleSubstitution(QualType(TST, 0))) {
      TemplateDecl *TD = TST->getTemplateName().getAsTemplateDecl();

      mangleTemplatePrefix(TD);
      mangleTemplateArgs(TST->getArgs(), TST->getNumArgs());
      addSubstitution(QualType(TST, 0));
    }
  } else if (const TemplateTypeParmType *TTPT = 
              dyn_cast<TemplateTypeParmType>(QTy)) {
    // We use the QualType mangle type variant here because it handles
    // substitutions.
    mangleType(QualType(TTPT, 0));
  } else
    assert(false && "Unhandled type!");

  mangleSourceName(T->getIdentifier());
  
  Out << 'E';
}

void CXXNameMangler::mangleExpression(const Expr *E) {
  // <expression> ::= <unary operator-name> <expression>
	//              ::= <binary operator-name> <expression> <expression>
	//              ::= <trinary operator-name> <expression> <expression> <expression>
  //              ::= cl <expression>* E	        # call
  //              ::= cv <type> expression           # conversion with one argument
  //              ::= cv <type> _ <expression>* E # conversion with a different number of arguments
  //              ::= st <type>		        # sizeof (a type)
  //              ::= at <type>                      # alignof (a type)
  //              ::= <template-param>
  //              ::= <function-param>
  //              ::= sr <type> <unqualified-name>                   # dependent name
  //              ::= sr <type> <unqualified-name> <template-args>   # dependent template-id
  //              ::= sZ <template-param>                            # size of a parameter pack
	//              ::= <expr-primary>
  switch (E->getStmtClass()) {
  default: assert(false && "Unhandled expression kind!");
  case Expr::DeclRefExprClass: {
    const Decl *D = cast<DeclRefExpr>(E)->getDecl();
    
    switch (D->getKind()) {
    default: assert(false && "Unhandled decl kind!");
    case Decl::NonTypeTemplateParm: {
      const NonTypeTemplateParmDecl *PD = cast<NonTypeTemplateParmDecl>(D);
      mangleTemplateParameter(PD->getIndex());
      break;
    }

    }
    
    break;
  }
  
  case Expr::UnresolvedDeclRefExprClass: {
    const UnresolvedDeclRefExpr *DRE = cast<UnresolvedDeclRefExpr>(E);
    const Type *QTy = DRE->getQualifier()->getAsType();
    assert(QTy && "Qualifier was not type!");

    // ::= sr <type> <unqualified-name>                   # dependent name
    Out << "sr";
    mangleType(QualType(QTy, 0));
    
    assert(DRE->getDeclName().getNameKind() == DeclarationName::Identifier &&
           "Unhandled decl name kind!");
    mangleSourceName(DRE->getDeclName().getAsIdentifierInfo());
    
    break;
  }

  }
}

// FIXME: <type> ::= G <type>   # imaginary (C 2000)
// FIXME: <type> ::= U <source-name> <type>     # vendor extended type qualifier

void CXXNameMangler::mangleCXXCtorType(CXXCtorType T) {
  // <ctor-dtor-name> ::= C1  # complete object constructor
  //                  ::= C2  # base object constructor
  //                  ::= C3  # complete object allocating constructor
  //
  switch (T) {
  case Ctor_Complete:
    Out << "C1";
    break;
  case Ctor_Base:
    Out << "C2";
    break;
  case Ctor_CompleteAllocating:
    Out << "C3";
    break;
  }
}

void CXXNameMangler::mangleCXXDtorType(CXXDtorType T) {
  // <ctor-dtor-name> ::= D0  # deleting destructor
  //                  ::= D1  # complete object destructor
  //                  ::= D2  # base object destructor
  //
  switch (T) {
  case Dtor_Deleting:
    Out << "D0";
    break;
  case Dtor_Complete:
    Out << "D1";
    break;
  case Dtor_Base:
    Out << "D2";
    break;
  }
}

void CXXNameMangler::mangleTemplateArgumentList(const TemplateArgumentList &L) {
  // <template-args> ::= I <template-arg>+ E
  Out << "I";

  for (unsigned i = 0, e = L.size(); i != e; ++i) {
    const TemplateArgument &A = L[i];

    mangleTemplateArgument(A);
  }

  Out << "E";
}

void CXXNameMangler::mangleTemplateArgs(const TemplateArgument *TemplateArgs,
                                        unsigned NumTemplateArgs) {
  // <template-args> ::= I <template-arg>+ E
  Out << "I";
  
  for (unsigned i = 0; i != NumTemplateArgs; ++i) {
    mangleTemplateArgument(TemplateArgs[i]);
  }
  
  Out << "E";
}

void CXXNameMangler::mangleTemplateArgument(const TemplateArgument &A) {
  // <template-arg> ::= <type>              # type or template
  //                ::= X <expression> E    # expression
  //                ::= <expr-primary>      # simple expressions
  //                ::= I <template-arg>* E # argument pack
  //                ::= sp <expression>     # pack expansion of (C++0x)
  switch (A.getKind()) {
  default:
    assert(0 && "Unknown template argument kind!");
  case TemplateArgument::Type:
    mangleType(A.getAsType());
    break;
  case TemplateArgument::Expression:
    Out << 'X';
    mangleExpression(A.getAsExpr());
    Out << 'E';
    break;
  case TemplateArgument::Integral:
    //  <expr-primary> ::= L <type> <value number> E # integer literal

    Out << 'L';

    mangleType(A.getIntegralType());

    const llvm::APSInt *Integral = A.getAsIntegral();
    if (A.getIntegralType()->isBooleanType()) {
      // Boolean values are encoded as 0/1.
      Out << (Integral->getBoolValue() ? '1' : '0');
    } else {
      if (Integral->isNegative())
        Out << 'n';
      Integral->abs().print(Out, false);
    }

    Out << 'E';
    break;
  }
}

void CXXNameMangler::mangleTemplateParameter(unsigned Index) {
  // <template-param> ::= T_    # first template parameter
  //                  ::= T <parameter-2 non-negative number> _
  if (Index == 0)
    Out << "T_";
  else
    Out << 'T' << (Index - 1) << '_';
}

// <substitution> ::= S <seq-id> _
//                ::= S_
bool CXXNameMangler::mangleSubstitution(const NamedDecl *ND) {
  // Try one of the standard substitutions first.
  if (mangleStandardSubstitution(ND))
    return true;
  
  return mangleSubstitution(reinterpret_cast<uintptr_t>(ND));
}

bool CXXNameMangler::mangleSubstitution(QualType T) {
  if (!T.getCVRQualifiers()) {
    if (const RecordType *RT = T->getAs<RecordType>())
      return mangleSubstitution(RT->getDecl());
  }
  
  uintptr_t TypePtr = reinterpret_cast<uintptr_t>(T.getAsOpaquePtr());

  return mangleSubstitution(TypePtr);
}

bool CXXNameMangler::mangleSubstitution(uintptr_t Ptr) {
  llvm::DenseMap<uintptr_t, unsigned>::iterator I = 
    Substitutions.find(Ptr);
  if (I == Substitutions.end())
    return false;
  
  unsigned SeqID = I->second;
  if (SeqID == 0)
    Out << "S_";
  else {
    SeqID--;
    
    // <seq-id> is encoded in base-36, using digits and upper case letters.
    char Buffer[10];
    char *BufferPtr = Buffer + 9;
    
    *BufferPtr = 0;
    if (SeqID == 0) *--BufferPtr = '0';
    
    while (SeqID) {
      assert(BufferPtr > Buffer && "Buffer overflow!");
      
      unsigned char c = static_cast<unsigned char>(SeqID) % 36;
      
      *--BufferPtr =  (c < 10 ? '0' + c : 'A' + c - 10);
      SeqID /= 36;
    }
    
    Out << 'S' << BufferPtr << '_';
  }
  
  return true;
}

static bool isCharType(QualType T) {
  if (T.isNull())
    return false;
      
  return T->isSpecificBuiltinType(BuiltinType::Char_S) ||
    T->isSpecificBuiltinType(BuiltinType::Char_U);
}

/// isCharSpecialization - Returns whether a given type is a template 
/// specialization of a given name with a single argument of type char.
static bool isCharSpecialization(QualType T, const char *Name) {
  if (T.isNull())
    return false;
  
  const RecordType *RT = T->getAs<RecordType>();
  if (!RT)
    return false;
  
  const ClassTemplateSpecializationDecl *SD = 
    dyn_cast<ClassTemplateSpecializationDecl>(RT->getDecl());
  if (!SD)
    return false;

  if (!isStdNamespace(SD->getDeclContext()))
    return false;
  
  const TemplateArgumentList &TemplateArgs = SD->getTemplateArgs();
  if (TemplateArgs.size() != 1)
    return false;
  
  if (!isCharType(TemplateArgs[0].getAsType()))
    return false;
  
  if (strcmp(SD->getIdentifier()->getName(), Name) != 0)
    return false;

  return true;
}

bool CXXNameMangler::mangleStandardSubstitution(const NamedDecl *ND) {
  // <substitution> ::= St # ::std::
  if (const NamespaceDecl *NS = dyn_cast<NamespaceDecl>(ND)) {
    if (isStdNamespace(NS)) {
      Out << "St";
      return true;
    }
  }

  if (const ClassTemplateDecl *TD = dyn_cast<ClassTemplateDecl>(ND)) {
    if (!isStdNamespace(TD->getDeclContext()))
      return false;
    
    // <substitution> ::= Sa # ::std::allocator
    if (TD->getIdentifier()->isStr("allocator")) {
      Out << "Sa";
      return true;
    }
    
    // <<substitution> ::= Sb # ::std::basic_string
    if (TD->getIdentifier()->isStr("basic_string")) {
      Out << "Sb";
      return true;
    }
  }
  
  if (const ClassTemplateSpecializationDecl *SD = 
        dyn_cast<ClassTemplateSpecializationDecl>(ND)) {
    //    <substitution> ::= Ss # ::std::basic_string<char,
    //                            ::std::char_traits<char>,
    //                            ::std::allocator<char> >
    if (SD->getIdentifier()->isStr("basic_string")) {
      const TemplateArgumentList &TemplateArgs = SD->getTemplateArgs();
      
      if (TemplateArgs.size() != 3)
        return false;
      
      if (!isCharType(TemplateArgs[0].getAsType()))
        return false;
      
      if (!isCharSpecialization(TemplateArgs[1].getAsType(), "char_traits"))
        return false;
      
      if (!isCharSpecialization(TemplateArgs[2].getAsType(), "allocator"))
        return false;

      Out << "Ss";
      return true;
    }
  }
  return false;
}

void CXXNameMangler::addSubstitution(QualType T) {
  if (!T.getCVRQualifiers()) {
    if (const RecordType *RT = T->getAs<RecordType>()) {
      addSubstitution(RT->getDecl());
      return;
    }
  }
  
  uintptr_t TypePtr = reinterpret_cast<uintptr_t>(T.getAsOpaquePtr());
  addSubstitution(TypePtr);
}

void CXXNameMangler::addSubstitution(uintptr_t Ptr) {
  unsigned SeqID = Substitutions.size();
  
  assert(!Substitutions.count(Ptr) && "Substitution already exists!");
  Substitutions[Ptr] = SeqID;  
}

namespace clang {
  /// \brief Mangles the name of the declaration D and emits that name to the
  /// given output stream.
  ///
  /// If the declaration D requires a mangled name, this routine will emit that
  /// mangled name to \p os and return true. Otherwise, \p os will be unchanged
  /// and this routine will return false. In this case, the caller should just
  /// emit the identifier of the declaration (\c D->getIdentifier()) as its
  /// name.
  bool mangleName(const NamedDecl *D, ASTContext &Context,
                  llvm::raw_ostream &os) {
    assert(!isa<CXXConstructorDecl>(D) &&
           "Use mangleCXXCtor for constructor decls!");
    assert(!isa<CXXDestructorDecl>(D) &&
           "Use mangleCXXDtor for destructor decls!");

    PrettyStackTraceDecl CrashInfo(const_cast<NamedDecl *>(D), SourceLocation(),
                                   Context.getSourceManager(),
                                   "Mangling declaration");
    
    CXXNameMangler Mangler(Context, os);
    if (!Mangler.mangle(D))
      return false;

    os.flush();
    return true;
  }

  /// \brief Mangles the a thunk with the offset n for the declaration D and
  /// emits that name to the given output stream.
  void mangleThunk(const FunctionDecl *FD, int64_t nv, int64_t v,
                   ASTContext &Context, llvm::raw_ostream &os) {
    // FIXME: Hum, we might have to thunk these, fix.
    assert(!isa<CXXDestructorDecl>(FD) &&
           "Use mangleCXXDtor for destructor decls!");

    CXXNameMangler Mangler(Context, os);
    Mangler.mangleThunk(FD, nv, v);
    os.flush();
  }

  /// \brief Mangles the a covariant thunk for the declaration D and emits that
  /// name to the given output stream.
  void mangleCovariantThunk(const FunctionDecl *FD, int64_t nv_t, int64_t v_t,
                            int64_t nv_r, int64_t v_r, ASTContext &Context,
                            llvm::raw_ostream &os) {
    // FIXME: Hum, we might have to thunk these, fix.
    assert(!isa<CXXDestructorDecl>(FD) &&
           "Use mangleCXXDtor for destructor decls!");

    CXXNameMangler Mangler(Context, os);
    Mangler.mangleCovariantThunk(FD, nv_t, v_t, nv_r, v_r);
    os.flush();
  }

  /// mangleGuardVariable - Returns the mangled name for a guard variable
  /// for the passed in VarDecl.
  void mangleGuardVariable(const VarDecl *D, ASTContext &Context,
                           llvm::raw_ostream &os) {
    CXXNameMangler Mangler(Context, os);
    Mangler.mangleGuardVariable(D);

    os.flush();
  }

  void mangleCXXCtor(const CXXConstructorDecl *D, CXXCtorType Type,
                     ASTContext &Context, llvm::raw_ostream &os) {
    CXXNameMangler Mangler(Context, os);
    Mangler.mangleCXXCtor(D, Type);

    os.flush();
  }

  void mangleCXXDtor(const CXXDestructorDecl *D, CXXDtorType Type,
                     ASTContext &Context, llvm::raw_ostream &os) {
    CXXNameMangler Mangler(Context, os);
    Mangler.mangleCXXDtor(D, Type);

    os.flush();
  }

  void mangleCXXVtable(QualType Type, ASTContext &Context,
                       llvm::raw_ostream &os) {
    CXXNameMangler Mangler(Context, os);
    Mangler.mangleCXXVtable(Type);

    os.flush();
  }

  void mangleCXXRtti(QualType Type, ASTContext &Context,
                     llvm::raw_ostream &os) {
    CXXNameMangler Mangler(Context, os);
    Mangler.mangleCXXRtti(Type);

    os.flush();
  }
}