C++ ProtocolConformanceRef::getConcrete方法代码示例

/// Compute substitutions for making a direct call to a SIL function with
/// @convention(witness_method) convention.
///
/// Such functions have a substituted generic signature where the
/// abstract `Self` parameter from the original type of the protocol
/// requirement is replaced by a concrete type.
///
/// Thus, the original substitutions of the apply instruction that
/// are written in terms of the requirement's generic signature need
/// to be remapped to substitutions suitable for the witness signature.
///
/// Supported remappings are:
///
/// - (Concrete witness thunk) Original substitutions:
///   [Self := ConcreteType, R0 := X0, R1 := X1, ...]
/// - Requirement generic signature:
///   <Self : P, R0, R1, ...>
/// - Witness thunk generic signature:
///   <W0, W1, ...>
/// - Remapped substitutions:
///   [W0 := X0, W1 := X1, ...]
///
/// - (Class witness thunk) Original substitutions:
///   [Self := C<A0, A1>, T0 := X0, T1 := X1, ...]
/// - Requirement generic signature:
///   <Self : P, R0, R1, ...>
/// - Witness thunk generic signature:
///   <Self : C<B0, B1>, B0, B1, W0, W1, ...>
/// - Remapped substitutions:
///   [Self := C<B0, B1>, B0 := A0, B1 := A1, W0 := X0, W1 := X1]
///
/// - (Default witness thunk) Original substitutions:
///   [Self := ConcreteType, R0 := X0, R1 := X1, ...]
/// - Requirement generic signature:
///   <Self : P, R0, R1, ...>
/// - Witness thunk generic signature:
///   <Self : P, W0, W1, ...>
/// - Remapped substitutions:
///   [Self := ConcreteType, W0 := X0, W1 := X1, ...]
///
/// \param conformanceRef The (possibly-specialized) conformance
/// \param requirementSig The generic signature of the requirement
/// \param witnessThunkSig The generic signature of the witness method
/// \param origSubMap The substitutions from the call instruction
/// \param isDefaultWitness True if this is a default witness method
/// \param classWitness The ClassDecl if this is a class witness method
static SubstitutionMap
getWitnessMethodSubstitutions(
    ModuleDecl *mod,
    ProtocolConformanceRef conformanceRef,
    GenericSignature *requirementSig,
    GenericSignature *witnessThunkSig,
    SubstitutionMap origSubMap,
    bool isDefaultWitness,
    ClassDecl *classWitness) {

  if (witnessThunkSig == nullptr)
    return SubstitutionMap();

  if (isDefaultWitness)
    return origSubMap;

  assert(!conformanceRef.isAbstract());
  auto conformance = conformanceRef.getConcrete();

  // If `Self` maps to a bound generic type, this gives us the
  // substitutions for the concrete type's generic parameters.
  auto baseSubMap = conformance->getSubstitutions(mod);

  unsigned baseDepth = 0;
  auto *rootConformance = conformance->getRootNormalConformance();
  if (auto *witnessSig = rootConformance->getGenericSignature())
    baseDepth = witnessSig->getGenericParams().back()->getDepth() + 1;

  // If the witness has a class-constrained 'Self' generic parameter,
  // we have to build a new substitution map that shifts all generic
  // parameters down by one.
  if (classWitness != nullptr) {
    auto *proto = conformance->getProtocol();
    auto selfType = proto->getSelfInterfaceType();

    auto selfSubMap = SubstitutionMap::getProtocolSubstitutions(
        proto, selfType.subst(origSubMap), conformanceRef);
    if (baseSubMap.empty()) {
      assert(baseDepth == 0);
      baseSubMap = selfSubMap;
    } else {
      baseSubMap = SubstitutionMap::combineSubstitutionMaps(
          selfSubMap,
          baseSubMap,
          CombineSubstitutionMaps::AtDepth,
          /*firstDepth=*/1,
          /*secondDepth=*/0,
          witnessThunkSig);
    }
    baseDepth += 1;
  }

  return SubstitutionMap::combineSubstitutionMaps(
      baseSubMap,
//.........这里部分代码省略.........

Type
ProtocolConformanceRef::getTypeWitnessByName(Type type,
                                             ProtocolConformanceRef conformance,
                                             Identifier name,
                                             LazyResolver *resolver) {
  // For an archetype, retrieve the nested type with the appropriate
  // name. There are no conformance tables.
  if (auto archetype = type->getAs<ArchetypeType>()) {
    return archetype->getNestedType(name);
  }

  // Find the named requirement.
  AssociatedTypeDecl *assocType = nullptr;
  auto members = conformance.getRequirement()->lookupDirect(name);
  for (auto member : members) {
    assocType = dyn_cast<AssociatedTypeDecl>(member);
    if (assocType)
      break;
  }

  // FIXME: Shouldn't this be a hard error?
  if (!assocType)
    return nullptr;

  if (conformance.isAbstract())
    return DependentMemberType::get(type, assocType);

  auto concrete = conformance.getConcrete();
  if (!concrete->hasTypeWitness(assocType, resolver)) {
    return nullptr;
  }
  return concrete->getTypeWitness(assocType, resolver);
}

// Eagerly visiting all used conformances leads to a large blowup
// in the amount of SIL we read in. For optimization purposes we can defer
// reading in most conformances until we need them for devirtualization.
// However, we *must* pull in shared clang-importer-derived conformances
// we potentially use, since we may not otherwise have a local definition.
static bool mustDeserializeProtocolConformance(SILModule &M,
                                               ProtocolConformanceRef c) {
  if (!c.isConcrete())
    return false;
  auto conformance = c.getConcrete()->getRootNormalConformance();
  return M.Types.protocolRequiresWitnessTable(conformance->getProtocol())
    && isa<ClangModuleUnit>(conformance->getDeclContext()
                                       ->getModuleScopeContext());
}

std::pair<SILWitnessTable *, ArrayRef<Substitution>>
SILModule::
lookUpWitnessTable(ProtocolConformanceRef C, bool deserializeLazily) {
  // If we have an abstract conformance passed in (a legal value), just return
  // nullptr.
  if (!C.isConcrete())
    return {nullptr, {}};

  return lookUpWitnessTable(C.getConcrete());
}

Type TypeChecker::getWitnessType(Type type, ProtocolDecl *protocol,
                                 ProtocolConformanceRef conformance,
                                 Identifier name,
                                 Diag<> brokenProtocolDiag) {
  Type ty = ProtocolConformance::getTypeWitnessByName(type, conformance,
                                                      name, this);
  if (!ty &&
      !(conformance.isConcrete() && conformance.getConcrete()->isInvalid()))
    diagnose(protocol->getLoc(), brokenProtocolDiag);

  return ty;
}

bool SILLinkerVisitor::visitProtocolConformance(
    ProtocolConformanceRef ref, const Optional<SILDeclRef> &Member) {
  // If an abstract protocol conformance was passed in, just return false.
  if (ref.isAbstract())
    return false;

  // Otherwise try and lookup a witness table for C.
  auto C = ref.getConcrete();
  SILWitnessTable *WT = Mod.lookUpWitnessTable(C).first;

  // If we don't find any witness table for the conformance, bail and return
  // false.
  if (!WT) {
    Mod.createWitnessTableDeclaration(
        C, TypeConverter::getLinkageForProtocolConformance(
               C->getRootNormalConformance(), NotForDefinition));
    return false;
  }

  // If the looked up witness table is a declaration, there is nothing we can
  // do here. Just bail and return false.
  if (WT->isDeclaration())
    return false;

  bool performFuncDeserialization = false;
  // For each entry in the witness table...
  for (auto &E : WT->getEntries()) {
    // If the entry is a witness method...
    if (E.getKind() == SILWitnessTable::WitnessKind::Method) {
      // And we are only interested in deserializing a specific requirement
      // and don't have that requirement, don't deserialize this method.
      if (Member.hasValue() && E.getMethodWitness().Requirement != *Member)
        continue;

      // The witness could be removed by dead function elimination.
      if (!E.getMethodWitness().Witness)
        continue;

      // Otherwise if it is the requirement we are looking for or we just want
      // to deserialize everything, add the function to the list of functions
      // to deserialize.
      performFuncDeserialization = true;
      addFunctionToWorklist(E.getMethodWitness().Witness);
    }
  }

  return performFuncDeserialization;
}

/// Compute substitutions for making a direct call to a SIL function with
/// @convention(witness_method) convention.
///
/// Such functions have a substituted generic signature where the
/// abstract `Self` parameter from the original type of the protocol
/// requirement is replaced by a concrete type.
///
/// Thus, the original substitutions of the apply instruction that
/// are written in terms of the requirement's generic signature need
/// to be remapped to substitutions suitable for the witness signature.
///
/// \param conformanceRef The (possibly-specialized) conformance
/// \param requirementSig The generic signature of the requirement
/// \param witnessThunkSig The generic signature of the witness method
/// \param origSubs The substitutions from the call instruction
/// \param newSubs New substitutions are stored here
static void getWitnessMethodSubstitutions(
    SILModule &M,
    ProtocolConformanceRef conformanceRef,
    GenericSignature *requirementSig,
    GenericSignature *witnessThunkSig,
    SubstitutionList origSubs,
    bool isDefaultWitness,
    SmallVectorImpl<Substitution> &newSubs) {

  if (witnessThunkSig == nullptr)
    return;

  if (isDefaultWitness) {
    newSubs.append(origSubs.begin(), origSubs.end());
    return;
  }

  assert(!conformanceRef.isAbstract());
  auto conformance = conformanceRef.getConcrete();

  // If `Self` maps to a bound generic type, this gives us the
  // substitutions for the concrete type's generic parameters.
  auto baseSubMap = getSubstitutionsForProtocolConformance(conformanceRef);

  unsigned baseDepth = 0;
  auto *rootConformance = conformance->getRootNormalConformance();
  if (auto *witnessSig = rootConformance->getGenericSignature())
    baseDepth = witnessSig->getGenericParams().back()->getDepth() + 1;

  auto origDepth = 1;
  auto origSubMap = requirementSig->getSubstitutionMap(origSubs);

  auto subMap =
    SubstitutionMap::combineSubstitutionMaps(baseSubMap,
                                             origSubMap, 
                                             CombineSubstitutionMaps::AtDepth,
                                             baseDepth,
                                             origDepth,
                                             witnessThunkSig);

  witnessThunkSig->getSubstitutions(subMap, newSubs);
}

static ArrayRef<Substitution>
getSubstitutionsForProtocolConformance(ProtocolConformanceRef CRef) {
  if (CRef.isAbstract())
    return {};
  
  auto C = CRef.getConcrete();

  // Walk down to the base NormalProtocolConformance.
  ArrayRef<Substitution> Subs;
  const ProtocolConformance *ParentC = C;
  while (!isa<NormalProtocolConformance>(ParentC)) {
    switch (ParentC->getKind()) {
    case ProtocolConformanceKind::Normal:
      llvm_unreachable("should have exited the loop?!");
    case ProtocolConformanceKind::Inherited:
      ParentC = cast<InheritedProtocolConformance>(ParentC)
        ->getInheritedConformance();
      break;
    case ProtocolConformanceKind::Specialized: {
      auto SC = cast<SpecializedProtocolConformance>(ParentC);
      ParentC = SC->getGenericConformance();
      assert(Subs.empty() && "multiple conformance specializations?!");
      Subs = SC->getGenericSubstitutions();
      break;
    }
    }
  }
  const NormalProtocolConformance *NormalC
    = cast<NormalProtocolConformance>(ParentC);

  // If the normal conformance is for a generic type, and we didn't hit a
  // specialized conformance, collect the substitutions from the generic type.
  // FIXME: The AST should do this for us.
  if (NormalC->getType()->isSpecialized() && Subs.empty()) {
    Subs = NormalC->getType()
      ->gatherAllSubstitutions(NormalC->getDeclContext()->getParentModule(),
                               nullptr);
  }
  
  return Subs;
}

void SILLinkerVisitor::visitProtocolConformance(
    ProtocolConformanceRef ref, const Optional<SILDeclRef> &Member) {
  // If an abstract protocol conformance was passed in, do nothing.
  if (ref.isAbstract())
    return;
  
  bool mustDeserialize = mustDeserializeProtocolConformance(Mod, ref);

  // Otherwise try and lookup a witness table for C.
  auto C = ref.getConcrete();
  
  if (!VisitedConformances.insert(C).second)
    return;

  auto *WT = Mod.lookUpWitnessTable(C, mustDeserialize);

  // If the looked up witness table is a declaration, there is nothing we can
  // do here.
  if (WT == nullptr || WT->isDeclaration()) {
    assert(!mustDeserialize &&
           "unable to deserialize witness table when we must?!");
    return;
  }

  auto maybeVisitRelatedConformance = [&](ProtocolConformanceRef c) {
    // Formally all conformances referenced by a used conformance are used.
    // However, eagerly visiting them all at this point leads to a large blowup
    // in the amount of SIL we read in. For optimization purposes we can defer
    // reading in most conformances until we need them for devirtualization.
    // However, we *must* pull in shared clang-importer-derived conformances
    // we potentially use, since we may not otherwise have a local definition.
    if (mustDeserializeProtocolConformance(Mod, c))
      visitProtocolConformance(c, None);
  };
  
  // For each entry in the witness table...
  for (auto &E : WT->getEntries()) {
    switch (E.getKind()) {
    // If the entry is a witness method...
    case SILWitnessTable::WitnessKind::Method: {
      // And we are only interested in deserializing a specific requirement
      // and don't have that requirement, don't deserialize this method.
      if (Member.hasValue() && E.getMethodWitness().Requirement != *Member)
        continue;

      // The witness could be removed by dead function elimination.
      if (!E.getMethodWitness().Witness)
        continue;

      // Otherwise, deserialize the witness if it has shared linkage, or if
      // we were asked to deserialize everything.
      maybeAddFunctionToWorklist(E.getMethodWitness().Witness);
      break;
    }
    
    // If the entry is a related witness table, see whether we need to
    // eagerly deserialize it.
    case SILWitnessTable::WitnessKind::BaseProtocol: {
      auto baseConformance = E.getBaseProtocolWitness().Witness;
      maybeVisitRelatedConformance(ProtocolConformanceRef(baseConformance));
      break;
    }
    case SILWitnessTable::WitnessKind::AssociatedTypeProtocol: {
      auto assocConformance = E.getAssociatedTypeProtocolWitness().Witness;
      maybeVisitRelatedConformance(assocConformance);
      break;
    }
    
    case SILWitnessTable::WitnessKind::AssociatedType:
    case SILWitnessTable::WitnessKind::Invalid:
      break;
    }
  }
}

/// Compute substitutions for making a direct call to a SIL function with
/// @convention(witness_method) convention.
///
/// Such functions have a substituted generic signature where the
/// abstract `Self` parameter from the original type of the protocol
/// requirement is replaced by a concrete type.
///
/// Thus, the original substitutions of the apply instruction that
/// are written in terms of the requirement's generic signature need
/// to be remapped to substitutions suitable for the witness signature.
///
/// \param conformanceRef The (possibly-specialized) conformance
/// \param requirementSig The generic signature of the requirement
/// \param witnessThunkSig The generic signature of the witness method
/// \param origSubs The substitutions from the call instruction
/// \param newSubs New substitutions are stored here
static void getWitnessMethodSubstitutions(
    SILModule &M,
    ProtocolConformanceRef conformanceRef,
    GenericSignature *requirementSig,
    GenericSignature *witnessThunkSig,
    ArrayRef<Substitution> origSubs,
    bool isDefaultWitness,
    SmallVectorImpl<Substitution> &newSubs) {

  if (witnessThunkSig == nullptr)
    return;

  assert(!conformanceRef.isAbstract());

  auto conformance = conformanceRef.getConcrete();

  // Otherwise, we need to build new caller-side substitutions
  // written in terms of the witness thunk's generic signature,
  // mapping to the archetypes of the caller.
  SubstitutionMap subMap;

  // Take apart substitutions from the conforming type.
  ArrayRef<Substitution> witnessSubs;
  auto *rootConformance = conformance->getRootNormalConformance();
  auto *witnessSig = rootConformance->getGenericSignature();
  unsigned depth = 0;
  if (isDefaultWitness) {
    // For default witnesses, we substitute all of Self.
    auto gp = witnessThunkSig->getGenericParams().front()->getCanonicalType();
    subMap.addSubstitution(gp, origSubs.front().getReplacement());
    subMap.addConformances(gp, origSubs.front().getConformances());

    // For default witnesses, innermost generic parameters are always at
    // depth 1.
    depth = 1;
  } else {
    // If `Self` maps to a bound generic type, this gives us the
    // substitutions for the concrete type's generic parameters.
    witnessSubs = getSubstitutionsForProtocolConformance(conformanceRef);

    if (!witnessSubs.empty()) {
      witnessSig->getSubstitutionMap(witnessSubs, subMap);
      depth = witnessSig->getGenericParams().back()->getDepth() + 1;
    }
  }

  // Next, take apart caller-side substitutions.
  //
  // Note that the Self-derived dependent types appearing on the left
  // hand side of the map are dropped.
  // FIXME: This won't be correct if the requirement itself adds 'Self'
  // requirements. We should be working from the substitutions in the witness.
  //
  // Also note that we rebuild the generic parameters in the requirement
  // to provide them with the required depth for the thunk itself.
  if (requirementSig->getGenericParams().back()->getDepth() > 0) {
    // Local function to replace generic parameters within the requirement
    // signature with the generic parameter we want to use in the substitution
    // map:
    //   - If the generic parameter is 'Self', return a null type so we don't
    //     add any substitution.
    //   - Otherwise, reset the generic parameter's depth one level deeper than
    //     the deepest generic parameter in the conformance.
    //
    // This local function is meant to be used with Type::transform();
    auto replaceGenericParameter = [&](Type type) -> Type {
      if (auto gp = type->getAs<GenericTypeParamType>()) {
        if (gp->getDepth() == 0) return Type();
        return GenericTypeParamType::get(depth, gp->getIndex(),
                                         M.getASTContext());
      }

      return type;
    };

    // Walk through the substitutions and dependent types.
    ArrayRef<Substitution> subs = origSubs;
    for (auto origDepTy : requirementSig->getAllDependentTypes()) {
      // Grab the next substitution.
      auto sub = subs.front();
      subs = subs.slice(1);

      // Map the generic parameters in the dependent type into the witness
      // thunk's depth.
//.........这里部分代码省略.........