//===- ComparisonCategories.cpp - Three Way Comparison Data -----*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

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

//

//  This file defines the Comparison Category enum and data types, which

//  store the types and expressions needed to support operator<=>

//

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

#include "clang/AST/ComparisonCategories.h"

#include "clang/AST/ASTContext.h"

#include "clang/AST/Decl.h"

#include "clang/AST/DeclCXX.h"

#include "clang/AST/Type.h"

#include "llvm/ADT/SmallVector.h"

using namespace clang;

Optional<ComparisonCategoryType>

clang::getComparisonCategoryForBuiltinCmp(QualType T) {

  using CCT = ComparisonCategoryType;

  if (T->isIntegralOrEnumerationType())

    return CCT::StrongOrdering;

  if (T->isRealFloatingType())

    return CCT::PartialOrdering;

  // C++2a [expr.spaceship]p8: If the composite pointer type is an object

  // pointer type, p <=> q is of type std::strong_ordering.

  // Note: this assumes neither operand is a null pointer constant.

  if (T->isObjectPointerType())

    return CCT::StrongOrdering;

  // TODO: Extend support for operator<=> to ObjC types.

  return llvm::None;

}

bool ComparisonCategoryInfo::ValueInfo::hasValidIntValue() const {

  assert(VD && "must have var decl");

  if (!VD->checkInitIsICE())

    return false;

  // Before we attempt to get the value of the first field, ensure that we

  // actually have one (and only one) field.

  auto *Record = VD->getType()->getAsCXXRecordDecl();

  if (std::distance(Record->field_begin(), Record->field_end()) != 1 ||

      !Record->field_begin()->getType()->isIntegralOrEnumerationType())

    return false;

  return true;

}

/// Attempt to determine the integer value used to represent the comparison

/// category result by evaluating the initializer for the specified VarDecl as

/// a constant expression and retreiving the value of the class's first

/// (and only) field.

///

/// Note: The STL types are expected to have the form:

///    struct X { T value; };

/// where T is an integral or enumeration type.

llvm::APSInt ComparisonCategoryInfo::ValueInfo::getIntValue() const {

  assert(hasValidIntValue() && "must have a valid value");

  return VD->evaluateValue()->getStructField(0).getInt();

}

ComparisonCategoryInfo::ValueInfo *ComparisonCategoryInfo::lookupValueInfo(

    ComparisonCategoryResult ValueKind) const {

  // Check if we already have a cache entry for this value.

  auto It = llvm::find_if(

      Objects, [&](ValueInfo const &Info) { return Info.Kind == ValueKind; });

  if (It != Objects.end())

    return &(*It);

  // We don't have a cached result. Lookup the variable declaration and create

  // a new entry representing it.

  DeclContextLookupResult Lookup = Record->getCanonicalDecl()->lookup(

      &Ctx.Idents.get(ComparisonCategories::getResultString(ValueKind)));

  if (Lookup.empty() || 
!isa<VarDecl>(Lookup.front())103
)

    return nullptr;

  Objects.emplace_back(ValueKind, cast<VarDecl>(Lookup.front()));

  return &Objects.back();

}

static const NamespaceDecl *lookupStdNamespace(const ASTContext &Ctx,

                                               NamespaceDecl *&StdNS) {

  if (!StdNS) {

    DeclContextLookupResult Lookup =

        Ctx.getTranslationUnitDecl()->lookup(&Ctx.Idents.get("std"));

    if (!Lookup.empty())

      StdNS = dyn_cast<NamespaceDecl>(Lookup.front());

  }

  return StdNS;

}

static CXXRecordDecl *lookupCXXRecordDecl(const ASTContext &Ctx,

                                          const NamespaceDecl *StdNS,

                                          ComparisonCategoryType Kind) {

  StringRef Name = ComparisonCategories::getCategoryString(Kind);

  DeclContextLookupResult Lookup = StdNS->lookup(&Ctx.Idents.get(Name));

  if (!Lookup.empty())

    if (CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(Lookup.front()))

      return RD;

  return nullptr;

}

const ComparisonCategoryInfo *

ComparisonCategories::lookupInfo(ComparisonCategoryType Kind) const {

  auto It = Data.find(static_cast<char>(Kind));

  if (It != Data.end())

    return &It->second;

  if (const NamespaceDecl *NS = lookupStdNamespace(Ctx, StdNS))

    if (CXXRecordDecl *RD = lookupCXXRecordDecl(Ctx, NS, Kind))

      return &Data.try_emplace((char)Kind, Ctx, RD, Kind).first->second;

  return nullptr;

}

const ComparisonCategoryInfo *

ComparisonCategories::lookupInfoForType(QualType Ty) const {

  assert(!Ty.isNull() && "type must be non-null");

  using CCT = ComparisonCategoryType;

  auto *RD = Ty->getAsCXXRecordDecl();

  if (!RD)

    return nullptr;

  // Check to see if we have information for the specified type cached.

  const auto *CanonRD = RD->getCanonicalDecl();

  for (auto &KV : Data) {

    const ComparisonCategoryInfo &Info = KV.second;

    if (CanonRD == Info.Record->getCanonicalDecl())

      return &Info;

  }

  if (!RD->getEnclosingNamespaceContext()->isStdNamespace())

    return nullptr;

  // If not, check to see if the decl names a type in namespace std with a name

  // matching one of the comparison category types.

  for (unsigned I = static_cast<unsigned>(CCT::First),

                End = static_cast<unsigned>(CCT::Last);

       I <= End; 
++I14
) {

    CCT Kind = static_cast<CCT>(I);

    // We've found the comparison category type. Build a new cache entry for

    // it.

    if (getCategoryString(Kind) == RD->getName())

      return &Data.try_emplace((char)Kind, Ctx, RD, Kind).first->second;

  }

  // We've found nothing. This isn't a comparison category type.

  return nullptr;

}

const ComparisonCategoryInfo &ComparisonCategories::getInfoForType(QualType Ty) const {

  const ComparisonCategoryInfo *Info = lookupInfoForType(Ty);

  assert(Info && "info for comparison category not found");

  return *Info;

}

QualType ComparisonCategoryInfo::getType() const {

  assert(Record);

  return QualType(Record->getTypeForDecl(), 0);

}

StringRef ComparisonCategories::getCategoryString(ComparisonCategoryType Kind) {

  using CCKT = ComparisonCategoryType;

  switch (Kind) {

  case CCKT::PartialOrdering:

    return "partial_ordering";

  case CCKT::WeakOrdering:

    return "weak_ordering";

  case CCKT::StrongOrdering:

    return "strong_ordering";

  }

  llvm_unreachable("unhandled cases in switch");

}

StringRef ComparisonCategories::getResultString(ComparisonCategoryResult Kind) {

  using CCVT = ComparisonCategoryResult;

  switch (Kind) {

  case CCVT::Equal:

    return "equal";

  case CCVT::Equivalent:

    return "equivalent";

  case CCVT::Less:

    return "less";

  case CCVT::Greater:

    return "greater";

  case CCVT::Unordered:

    return "unordered";

  }

  llvm_unreachable("unhandled case in switch");

}

std::vector<ComparisonCategoryResult>

ComparisonCategories::getPossibleResultsForType(ComparisonCategoryType Type) {

  using CCT = ComparisonCategoryType;

  using CCR = ComparisonCategoryResult;

  std::vector<CCR> Values;

  Values.reserve(4);

  bool IsStrong = Type == CCT::StrongOrdering;

  Values.push_back(IsStrong ? CCR::Equal : 
CCR::Equivalent8
);

  Values.push_back(CCR::Less);

  Values.push_back(CCR::Greater);

  if (Type == CCT::PartialOrdering)

    Values.push_back(CCR::Unordered);

  return Values;

}