//===------- ItaniumCXXABI.cpp - AST support for the Itanium C++ ABI ------===//

//

// 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 provides C++ AST support targeting the Itanium C++ ABI, which is

// documented at:

//  http://www.codesourcery.com/public/cxx-abi/abi.html

//  http://www.codesourcery.com/public/cxx-abi/abi-eh.html

//

// It also supports the closely-related ARM C++ ABI, documented at:

// http://infocenter.arm.com/help/topic/com.arm.doc.ihi0041c/IHI0041C_cppabi.pdf

//

//===----------------------------------------------------------------------===//

#include "CXXABI.h"

#include "clang/AST/ASTContext.h"

#include "clang/AST/DeclCXX.h"

#include "clang/AST/Mangle.h"

#include "clang/AST/MangleNumberingContext.h"

#include "clang/AST/RecordLayout.h"

#include "clang/AST/Type.h"

#include "clang/Basic/TargetInfo.h"

#include "llvm/ADT/FoldingSet.h"

#include "llvm/ADT/iterator.h"

#include <optional>

using namespace clang;

namespace {

/// According to Itanium C++ ABI 5.1.2:

/// the name of an anonymous union is considered to be

/// the name of the first named data member found by a pre-order,

/// depth-first, declaration-order walk of the data members of

/// the anonymous union.

/// If there is no such data member (i.e., if all of the data members

/// in the union are unnamed), then there is no way for a program to

/// refer to the anonymous union, and there is therefore no need to mangle its name.

///

/// Returns the name of anonymous union VarDecl or nullptr if it is not found.

static const IdentifierInfo *findAnonymousUnionVarDeclName(const VarDecl& VD) {

  const RecordType *RT = VD.getType()->getAs<RecordType>();

  assert(RT && "type of VarDecl is expected to be RecordType.");

  assert(RT->getDecl()->isUnion() && "RecordType is expected to be a union.");

  if (const FieldDecl *FD = RT->getDecl()->findFirstNamedDataMember()) {

    return FD->getIdentifier();

  }

  return nullptr;

}

/// The name of a decomposition declaration.

struct DecompositionDeclName {

  using BindingArray = ArrayRef<const BindingDecl*>;

  /// Representative example of a set of bindings with these names.

  BindingArray Bindings;

  /// Iterators over the sequence of identifiers in the name.

  struct Iterator

      : llvm::iterator_adaptor_base<Iterator, BindingArray::const_iterator,

                                    std::random_access_iterator_tag,

                                    const IdentifierInfo *> {

    Iterator(BindingArray::const_iterator It) : iterator_adaptor_base(It) {}

    const IdentifierInfo *operator*() const {

      return (*this->I)->getIdentifier();

    }

  };

  Iterator begin() const { return Iterator(Bindings.begin()); }

  Iterator end() const { return Iterator(Bindings.end()); }

};

}

namespace llvm {

template<typename T> bool isDenseMapKeyEmpty(T V) {

  return llvm::DenseMapInfo<T>::isEqual(

      V, llvm::DenseMapInfo<T>::getEmptyKey());

}

template<typename T> bool isDenseMapKeyTombstone(T V) {

  return llvm::DenseMapInfo<T>::isEqual(

      V, llvm::DenseMapInfo<T>::getTombstoneKey());

}

template <typename T>

std::optional<bool> areDenseMapKeysEqualSpecialValues(T LHS, T RHS) {

  bool LHSEmpty = isDenseMapKeyEmpty(LHS);

  bool RHSEmpty = isDenseMapKeyEmpty(RHS);

  if (LHSEmpty || RHSEmpty)

    return LHSEmpty && RHSEmpty;

  bool LHSTombstone = isDenseMapKeyTombstone(LHS);

  bool RHSTombstone = isDenseMapKeyTombstone(RHS);

  if (LHSTombstone || RHSTombstone)

    return LHSTombstone && RHSTombstone;

  return std::nullopt;

}

template<>

struct DenseMapInfo<DecompositionDeclName> {

  using ArrayInfo = llvm::DenseMapInfo<ArrayRef<const BindingDecl*>>;

  static DecompositionDeclName getEmptyKey() {

    return {ArrayInfo::getEmptyKey()};

  }

  static DecompositionDeclName getTombstoneKey() {

    return {ArrayInfo::getTombstoneKey()};

  }

  static unsigned getHashValue(DecompositionDeclName Key) {

    assert(!isEqual(Key, getEmptyKey()) && !isEqual(Key, getTombstoneKey()));

    return llvm::hash_combine_range(Key.begin(), Key.end());

  }

  static bool isEqual(DecompositionDeclName LHS, DecompositionDeclName RHS) {

    if (std::optional<bool> Result =

            areDenseMapKeysEqualSpecialValues(LHS.Bindings, RHS.Bindings))

      return *Result;

    return LHS.Bindings.size() == RHS.Bindings.size() &&

           std::equal(LHS.begin(), LHS.end(), RHS.begin());

  }

};

}

namespace {

/// Keeps track of the mangled names of lambda expressions and block

/// literals within a particular context.

class ItaniumNumberingContext : public MangleNumberingContext {

  ItaniumMangleContext *Mangler;

  llvm::StringMap<unsigned> LambdaManglingNumbers;

  unsigned BlockManglingNumber = 0;

  llvm::DenseMap<const IdentifierInfo *, unsigned> VarManglingNumbers;

  llvm::DenseMap<const IdentifierInfo *, unsigned> TagManglingNumbers;

  llvm::DenseMap<DecompositionDeclName, unsigned>

      DecompsitionDeclManglingNumbers;

public:

  ItaniumNumberingContext(ItaniumMangleContext *Mangler) : Mangler(Mangler) {}

  unsigned getManglingNumber(const CXXMethodDecl *CallOperator) override {

    const CXXRecordDecl *Lambda = CallOperator->getParent();

    assert(Lambda->isLambda());

    // Computation of the <lambda-sig> is non-trivial and subtle. Rather than

    // duplicating it here, just mangle the <lambda-sig> directly.

    llvm::SmallString<128> LambdaSig;

    llvm::raw_svector_ostream Out(LambdaSig);

    Mangler->mangleLambdaSig(Lambda, Out);

    return ++LambdaManglingNumbers[LambdaSig];

  }

  unsigned getManglingNumber(const BlockDecl *BD) override {

    return ++BlockManglingNumber;

  }

  unsigned getStaticLocalNumber(const VarDecl *VD) override {

    return 0;

  }

  /// Variable decls are numbered by identifier.

  unsigned getManglingNumber(const VarDecl *VD, unsigned) override {

    if (auto *DD = dyn_cast<DecompositionDecl>(VD)) {

      DecompositionDeclName Name{DD->bindings()};

      return ++DecompsitionDeclManglingNumbers[Name];

    }

    const IdentifierInfo *Identifier = VD->getIdentifier();

    if (!Identifier) {

      // VarDecl without an identifier represents an anonymous union

      // declaration.

      Identifier = findAnonymousUnionVarDeclName(*VD);

    }

    return ++VarManglingNumbers[Identifier];

  }

  unsigned getManglingNumber(const TagDecl *TD, unsigned) override {

    return ++TagManglingNumbers[TD->getIdentifier()];

  }

};

// A version of this for SYCL that makes sure that 'device' mangling context

// matches the lambda mangling number, so that __builtin_sycl_unique_stable_name

// can be consistently generated between a MS and Itanium host by just referring

// to the device mangling number.

class ItaniumSYCLNumberingContext : public ItaniumNumberingContext {

  llvm::DenseMap<const CXXMethodDecl *, unsigned> ManglingNumbers;

  using ManglingItr = decltype(ManglingNumbers)::iterator;

public:

  ItaniumSYCLNumberingContext(ItaniumMangleContext *Mangler)

      : ItaniumNumberingContext(Mangler) {}

  unsigned getManglingNumber(const CXXMethodDecl *CallOperator) override {

    unsigned Number = ItaniumNumberingContext::getManglingNumber(CallOperator);

    std::pair<ManglingItr, bool> emplace_result =

        ManglingNumbers.try_emplace(CallOperator, Number);

    (void)emplace_result;

    assert(emplace_result.second && "Lambda number set multiple times?");

    return Number;

  }

  using ItaniumNumberingContext::getManglingNumber;

  unsigned getDeviceManglingNumber(const CXXMethodDecl *CallOperator) override {

    ManglingItr Itr = ManglingNumbers.find(CallOperator);

    assert(Itr != ManglingNumbers.end() && "Lambda not yet mangled?");

    return Itr->second;

  }

};

class ItaniumCXXABI : public CXXABI {

private:

  std::unique_ptr<MangleContext> Mangler;

protected:

  ASTContext &Context;

public:

  ItaniumCXXABI(ASTContext &Ctx)

      : Mangler(Ctx.createMangleContext()), Context(Ctx) {}

  MemberPointerInfo

  getMemberPointerInfo(const MemberPointerType *MPT) const override {

    const TargetInfo &Target = Context.getTargetInfo();

    TargetInfo::IntType PtrDiff = Target.getPtrDiffType(LangAS::Default);

    MemberPointerInfo MPI;

    MPI.Width = Target.getTypeWidth(PtrDiff);

    MPI.Align = Target.getTypeAlign(PtrDiff);

    MPI.HasPadding = false;

    if (MPT->isMemberFunctionPointer())

      MPI.Width *= 2;

    return MPI;

  }

  CallingConv getDefaultMethodCallConv(bool isVariadic) const override {

    const llvm::Triple &T = Context.getTargetInfo().getTriple();

    if (!isVariadic && T.isWindowsGNUEnvironment() &&

        T.getArch() == llvm::Triple::x86)

      return CC_X86ThisCall;

    return Context.getTargetInfo().getDefaultCallingConv();

  }

  // We cheat and just check that the class has a vtable pointer, and that it's

  // only big enough to have a vtable pointer and nothing more (or less).

  bool isNearlyEmpty(const CXXRecordDecl *RD) const override {

    // Check that the class has a vtable pointer.

    if (!RD->isDynamicClass())

      return false;

    const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);

    CharUnits PointerSize = Context.toCharUnitsFromBits(

        Context.getTargetInfo().getPointerWidth(LangAS::Default));

    return Layout.getNonVirtualSize() == PointerSize;

  }

  const CXXConstructorDecl *

  getCopyConstructorForExceptionObject(CXXRecordDecl *RD) override {

    return nullptr;

  }

  void addCopyConstructorForExceptionObject(CXXRecordDecl *RD,

                                            CXXConstructorDecl *CD) override {}

  void addTypedefNameForUnnamedTagDecl(TagDecl *TD,

                                       TypedefNameDecl *DD) override {}

  TypedefNameDecl *getTypedefNameForUnnamedTagDecl(const TagDecl *TD) override {

    return nullptr;

  }

  void addDeclaratorForUnnamedTagDecl(TagDecl *TD,

                                      DeclaratorDecl *DD) override {}

  DeclaratorDecl *getDeclaratorForUnnamedTagDecl(const TagDecl *TD) override {

    return nullptr;

  }

  std::unique_ptr<MangleNumberingContext>

  createMangleNumberingContext() const override {

    if (Context.getLangOpts().isSYCL())

      return std::make_unique<ItaniumSYCLNumberingContext>(

          cast<ItaniumMangleContext>(Mangler.get()));

    return std::make_unique<ItaniumNumberingContext>(

        cast<ItaniumMangleContext>(Mangler.get()));

  }

};

}

CXXABI *clang::CreateItaniumCXXABI(ASTContext &Ctx) {

  return new ItaniumCXXABI(Ctx);

}

std::unique_ptr<MangleNumberingContext>

clang::createItaniumNumberingContext(MangleContext *Mangler) {

  return std::make_unique<ItaniumNumberingContext>(

      cast<ItaniumMangleContext>(Mangler));

}