//===------- MicrosoftCXXABI.cpp - AST support for the Microsoft 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 Microsoft Visual C++

// ABI.

//

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

#include "CXXABI.h"

#include "clang/AST/ASTContext.h"

#include "clang/AST/Attr.h"

#include "clang/AST/CXXInheritance.h"

#include "clang/AST/DeclCXX.h"

#include "clang/AST/MangleNumberingContext.h"

#include "clang/AST/RecordLayout.h"

#include "clang/AST/Type.h"

#include "clang/Basic/TargetInfo.h"

using namespace clang;

namespace {

/// Numbers things which need to correspond across multiple TUs.

/// Typically these are things like static locals, lambdas, or blocks.

class MicrosoftNumberingContext : public MangleNumberingContext {

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

  unsigned LambdaManglingNumber;

  unsigned StaticLocalNumber;

  unsigned StaticThreadlocalNumber;

public:

  MicrosoftNumberingContext()

      : MangleNumberingContext(), LambdaManglingNumber(0),

        StaticLocalNumber(0), StaticThreadlocalNumber(0) {}

  unsigned getManglingNumber(const CXXMethodDecl *CallOperator) override {

    return ++LambdaManglingNumber;

  }

  unsigned getManglingNumber(const BlockDecl *BD) override {

    const Type *Ty = nullptr;

    return ++ManglingNumbers[Ty];

  }

  unsigned getStaticLocalNumber(const VarDecl *VD) override {

    if (VD->getTLSKind())

      return ++StaticThreadlocalNumber;

    return ++StaticLocalNumber;

  }

  unsigned getManglingNumber(const VarDecl *VD,

                             unsigned MSLocalManglingNumber) override {

    return MSLocalManglingNumber;

  }

  unsigned getManglingNumber(const TagDecl *TD,

                             unsigned MSLocalManglingNumber) override {

    return MSLocalManglingNumber;

  }

};

class MicrosoftCXXABI : public CXXABI {

  ASTContext &Context;

  llvm::SmallDenseMap<CXXRecordDecl *, CXXConstructorDecl *> RecordToCopyCtor;

  llvm::SmallDenseMap<TagDecl *, DeclaratorDecl *>

      UnnamedTagDeclToDeclaratorDecl;

  llvm::SmallDenseMap<TagDecl *, TypedefNameDecl *>

      UnnamedTagDeclToTypedefNameDecl;

public:

  MicrosoftCXXABI(ASTContext &Ctx) : Context(Ctx) { }

  MemberPointerInfo

  getMemberPointerInfo(const MemberPointerType *MPT) const override;

  CallingConv getDefaultMethodCallConv(bool isVariadic) const override {

    if (!isVariadic &&

        Context.getTargetInfo().getTriple().getArch() == llvm::Triple::x86)

      return CC_X86ThisCall;

    return Context.getTargetInfo().getDefaultCallingConv();

  }

  bool isNearlyEmpty(const CXXRecordDecl *RD) const override {

    llvm_unreachable("unapplicable to the MS ABI");

  }

  const CXXConstructorDecl *

  getCopyConstructorForExceptionObject(CXXRecordDecl *RD) override {

    return RecordToCopyCtor[RD];

  }

  void

  addCopyConstructorForExceptionObject(CXXRecordDecl *RD,

                                       CXXConstructorDecl *CD) override {

    assert(CD != nullptr);

    assert(RecordToCopyCtor[RD] == nullptr || RecordToCopyCtor[RD] == CD);

    RecordToCopyCtor[RD] = CD;

  }

  void addTypedefNameForUnnamedTagDecl(TagDecl *TD,

                                       TypedefNameDecl *DD) override {

    TD = TD->getCanonicalDecl();

    DD = DD->getCanonicalDecl();

    TypedefNameDecl *&I = UnnamedTagDeclToTypedefNameDecl[TD];

    if (!I)

      I = DD;

  }

  TypedefNameDecl *getTypedefNameForUnnamedTagDecl(const TagDecl *TD) override {

    return UnnamedTagDeclToTypedefNameDecl.lookup(

        const_cast<TagDecl *>(TD->getCanonicalDecl()));

  }

  void addDeclaratorForUnnamedTagDecl(TagDecl *TD,

                                      DeclaratorDecl *DD) override {

    TD = TD->getCanonicalDecl();

    DD = cast<DeclaratorDecl>(DD->getCanonicalDecl());

    DeclaratorDecl *&I = UnnamedTagDeclToDeclaratorDecl[TD];

    if (!I)

      I = DD;

  }

  DeclaratorDecl *getDeclaratorForUnnamedTagDecl(const TagDecl *TD) override {

    return UnnamedTagDeclToDeclaratorDecl.lookup(

        const_cast<TagDecl *>(TD->getCanonicalDecl()));

  }

  std::unique_ptr<MangleNumberingContext>

  createMangleNumberingContext() const override {

    return std::make_unique<MicrosoftNumberingContext>();

  }

};

}

// getNumBases() seems to only give us the number of direct bases, and not the

// total.  This function tells us if we inherit from anybody that uses MI, or if

// we have a non-primary base class, which uses the multiple inheritance model.

static bool usesMultipleInheritanceModel(const CXXRecordDecl *RD) {

  while (RD->getNumBases() > 0) {

    if (RD->getNumBases() > 1)

      return true;

    assert(RD->getNumBases() == 1);

    const CXXRecordDecl *Base =

        RD->bases_begin()->getType()->getAsCXXRecordDecl();

    if (RD->isPolymorphic() && 
!Base->isPolymorphic()15
)

      return true;

    RD = Base;

  }

  return false;

}

MSInheritanceModel CXXRecordDecl::calculateInheritanceModel() const {

  if (!hasDefinition() || 
isParsingBaseSpecifiers()560
)

    return MSInheritanceModel::Unspecified;

  if (getNumVBases() > 0)

    return MSInheritanceModel::Virtual;

  if (usesMultipleInheritanceModel(this))

    return MSInheritanceModel::Multiple;

  return MSInheritanceModel::Single;

}

MSInheritanceModel CXXRecordDecl::getMSInheritanceModel() const {

  MSInheritanceAttr *IA = getAttr<MSInheritanceAttr>();

  assert(IA && "Expected MSInheritanceAttr on the CXXRecordDecl!");

  return IA->getInheritanceModel();

}

bool CXXRecordDecl::nullFieldOffsetIsZero() const {

  return !inheritanceModelHasOnlyOneField(/*IsMemberFunction=*/false,

                                          getMSInheritanceModel()) ||

         (hasDefinition() && 
isPolymorphic()100
);

}

MSVtorDispMode CXXRecordDecl::getMSVtorDispMode() const {

  if (MSVtorDispAttr *VDA = getAttr<MSVtorDispAttr>())

    return VDA->getVtorDispMode();

  return getASTContext().getLangOpts().getVtorDispMode();

}

// Returns the number of pointer and integer slots used to represent a member

// pointer in the MS C++ ABI.

//

// Member function pointers have the following general form;  however, fields

// are dropped as permitted (under the MSVC interpretation) by the inheritance

// model of the actual class.

//

//   struct {

//     // A pointer to the member function to call.  If the member function is

//     // virtual, this will be a thunk that forwards to the appropriate vftable

//     // slot.

//     void *FunctionPointerOrVirtualThunk;

//

//     // An offset to add to the address of the vbtable pointer after

//     // (possibly) selecting the virtual base but before resolving and calling

//     // the function.

//     // Only needed if the class has any virtual bases or bases at a non-zero

//     // offset.

//     int NonVirtualBaseAdjustment;

//

//     // The offset of the vb-table pointer within the object.  Only needed for

//     // incomplete types.

//     int VBPtrOffset;

//

//     // An offset within the vb-table that selects the virtual base containing

//     // the member.  Loading from this offset produces a new offset that is

//     // added to the address of the vb-table pointer to produce the base.

//     int VirtualBaseAdjustmentOffset;

//   };

static std::pair<unsigned, unsigned>

getMSMemberPointerSlots(const MemberPointerType *MPT) {

  const CXXRecordDecl *RD = MPT->getMostRecentCXXRecordDecl();

  MSInheritanceModel Inheritance = RD->getMSInheritanceModel();

  unsigned Ptrs = 0;

  unsigned Ints = 0;

  if (MPT->isMemberFunctionPointer())

    Ptrs = 1;

  else

    Ints = 1;

  if (inheritanceModelHasNVOffsetField(MPT->isMemberFunctionPointer(),

                                          Inheritance))

    Ints++;

  if (inheritanceModelHasVBPtrOffsetField(Inheritance))

    Ints++;

  if (inheritanceModelHasVBTableOffsetField(Inheritance))

    Ints++;

  return std::make_pair(Ptrs, Ints);

}

CXXABI::MemberPointerInfo MicrosoftCXXABI::getMemberPointerInfo(

    const MemberPointerType *MPT) const {

  // The nominal struct is laid out with pointers followed by ints and aligned

  // to a pointer width if any are present and an int width otherwise.

  const TargetInfo &Target = Context.getTargetInfo();

  unsigned PtrSize = Target.getPointerWidth(0);

  unsigned IntSize = Target.getIntWidth();

  unsigned Ptrs, Ints;

  std::tie(Ptrs, Ints) = getMSMemberPointerSlots(MPT);

  MemberPointerInfo MPI;

  MPI.HasPadding = false;

  MPI.Width = Ptrs * PtrSize + Ints * IntSize;

  // When MSVC does x86_32 record layout, it aligns aggregate member pointers to

  // 8 bytes.  However, __alignof usually returns 4 for data memptrs and 8 for

  // function memptrs.

  if (Ptrs + Ints > 1 && 
Target.getTriple().isArch32Bit()230
)

    MPI.Align = 64;

  else if (Ptrs)

    MPI.Align = Target.getPointerAlign(0);

  else

    MPI.Align = Target.getIntAlign();

  if (Target.getTriple().isArch64Bit()) {

    MPI.Width = llvm::alignTo(MPI.Width, MPI.Align);

    MPI.HasPadding = MPI.Width != (Ptrs * PtrSize + Ints * IntSize);

  }

  return MPI;

}

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

  return new MicrosoftCXXABI(Ctx);

}