void SILGenFunction::emitInjectOptionalValueInto(SILLocation loc,
                                                 ArgumentSource &&value,
                                                 SILValue dest,
                                                 const TypeLowering &optTL) {
  SILType optType = optTL.getLoweredType();
  assert(dest->getType() == optType.getAddressType());
  auto loweredPayloadTy = optType.getAnyOptionalObjectType();
  assert(loweredPayloadTy);

  // Project out the payload area.
  auto someDecl = getASTContext().getOptionalSomeDecl();
  auto destPayload =
    B.createInitEnumDataAddr(loc, dest, someDecl,
                             loweredPayloadTy.getAddressType());
  
  // Emit the value into the payload area.
  TemporaryInitialization emitInto(destPayload, CleanupHandle::invalid());
  std::move(value).forwardInto(*this, &emitInto);
  
  // Inject the tag.
  B.createInjectEnumAddr(loc, dest, someDecl);
}

static void splitDestructure(SILBuilder &B, SILInstruction *I, SILValue Op) {
  assert((isa<DestructureStructInst>(I) || isa<DestructureTupleInst>(I)) &&
         "Only destructure operations can be passed to splitDestructure");

  SILModule &M = I->getModule();
  SILLocation Loc = I->getLoc();
  SILType OpType = Op->getType();

  llvm::SmallVector<Projection, 8> Projections;
  Projection::getFirstLevelProjections(OpType, M, Projections);
  assert(Projections.size() == I->getNumResults());

  llvm::SmallVector<SILValue, 8> NewValues;
  for (unsigned i : indices(Projections)) {
    const auto &Proj = Projections[i];
    NewValues.push_back(Proj.createObjectProjection(B, Loc, Op).get());
    assert(NewValues.back()->getType() == I->getResults()[i]->getType() &&
           "Expected created projections and results to be the same types");
  }

  I->replaceAllUsesPairwiseWith(NewValues);
  I->eraseFromParent();
}

void CallSiteDescriptor::extendArgumentLifetime(
    SILValue Arg, SILArgumentConvention ArgConvention) const {
  assert(!CInfo->LifetimeFrontier.empty() &&
         "Need a post-dominating release(s)");

  auto ArgTy = Arg->getType();

  // Extend the lifetime of a captured argument to cover the callee.
  SILBuilderWithScope Builder(getClosure());

  // Indirect non-inout arguments are not supported yet.
  assert(!isNonInoutIndirectSILArgument(Arg, ArgConvention));

  if (ArgTy.isObject()) {
    Builder.createRetainValue(getClosure()->getLoc(), Arg,
                              Builder.getDefaultAtomicity());
    for (auto *I : CInfo->LifetimeFrontier) {
      Builder.setInsertionPoint(I);
      Builder.createReleaseValue(getClosure()->getLoc(), Arg,
                                 Builder.getDefaultAtomicity());
    }
  }
}

/// Compute the subelement number indicated by the specified pointer (which is
/// derived from the root by a series of tuple/struct element addresses) by
/// treating the type as a linearized namespace with sequential elements.  For
/// example, given:
///
///   root = alloc { a: { c: i64, d: i64 }, b: (i64, i64) }
///   tmp1 = struct_element_addr root, 1
///   tmp2 = tuple_element_addr tmp1, 0
///
/// This will return a subelement number of 2.
///
/// If this pointer is to within a existential projection, it returns ~0U.
///
static unsigned computeSubelement(SILValue Pointer, SILInstruction *RootInst) {
  unsigned SubEltNumber = 0;
  SILModule &M = RootInst->getModule();
  
  while (1) {
    // If we got to the root, we're done.
    if (RootInst == Pointer.getDef())
      return SubEltNumber;
    
    auto *Inst = cast<SILInstruction>(Pointer);
    if (auto *TEAI = dyn_cast<TupleElementAddrInst>(Inst)) {
      SILType TT = TEAI->getOperand().getType();
      
      // Keep track of what subelement is being referenced.
      for (unsigned i = 0, e = TEAI->getFieldNo(); i != e; ++i) {
        SubEltNumber += getNumSubElements(TT.getTupleElementType(i), M);
      }
      Pointer = TEAI->getOperand();
    } else if (auto *SEAI = dyn_cast<StructElementAddrInst>(Inst)) {
      SILType ST = SEAI->getOperand().getType();
      
      // Keep track of what subelement is being referenced.
      StructDecl *SD = SEAI->getStructDecl();
      for (auto *D : SD->getStoredProperties()) {
        if (D == SEAI->getField()) break;
        SubEltNumber += getNumSubElements(ST.getFieldType(D, M), M);
      }
      
      Pointer = SEAI->getOperand();
    } else {
      assert((isa<InitExistentialAddrInst>(Inst) || isa<InjectEnumAddrInst>(Inst))&&
             "Unknown access path instruction");
      // Cannot promote loads and stores from within an existential projection.
      return ~0U;
    }
  }
}

AccessedStorage::Kind AccessedStorage::classify(SILValue base) {
  switch (base->getKind()) {
  // An AllocBox is a fully identified memory location.
  case ValueKind::AllocBoxInst:
    return Box;
  // An AllocStack is a fully identified memory location, which may occur
  // after inlining code already subjected to stack promotion.
  case ValueKind::AllocStackInst:
    return Stack;
  case ValueKind::GlobalAddrInst:
    return Global;
  case ValueKind::ApplyInst: {
    FullApplySite apply(cast<ApplyInst>(base));
    if (auto *funcRef = apply.getReferencedFunction()) {
      if (getVariableOfGlobalInit(funcRef))
        return Global;
    }
    return Unidentified;
  }
  case ValueKind::RefElementAddrInst:
    return Class;
  // A yield is effectively a nested access, enforced independently in
  // the caller and callee.
  case ValueKind::BeginApplyResult:
    return Yield;
  // A function argument is effectively a nested access, enforced
  // independently in the caller and callee.
  case ValueKind::SILFunctionArgument:
    return Argument;
  // View the outer begin_access as a separate location because nested
  // accesses do not conflict with each other.
  case ValueKind::BeginAccessInst:
    return Nested;
  default:
    return Unidentified;
  }
}

static void mapOperands(SILInstruction *I,
                        const llvm::DenseMap<ValueBase *, SILValue> &ValueMap) {
  for (auto &Opd : I->getAllOperands()) {
    SILValue OrigVal = Opd.get();
    ValueBase *OrigDef = OrigVal.getDef();
    auto Found = ValueMap.find(OrigDef);
    if (Found != ValueMap.end()) {
      SILValue MappedVal = Found->second;
      unsigned ResultIdx = OrigVal.getResultNumber();
      // All mapped instructions have their result number set to zero. Except
      // for arguments that we followed along one edge to their incoming value
      // on that edge.
      if (isa<SILArgument>(OrigDef))
        ResultIdx = MappedVal.getResultNumber();
      Opd.set(SILValue(MappedVal.getDef(), ResultIdx));
    }
  }
}

NullablePtr<SILInstruction>
Projection::
createValueProjection(SILBuilder &B, SILLocation Loc, SILValue Base) const {
    // Grab Base's type.
    SILType BaseTy = Base.getType();

    // If BaseTy is not an object type, bail.
    if (!BaseTy.isObject())
        return nullptr;

    // If this projection is associated with an address type, convert its type to
    // an object type.
    //
    // We explicitly do not convert Type to be an object if it is a local storage
    // type since we want it to fail.
    SILType Ty = Type.isAddress()? Type.getObjectType() : Type;

    if (!Ty.isObject())
        return nullptr;

    // Ok, we now know that the type of Base and the type represented by the base
    // of this projection match and that this projection can be represented as
    // value. Create the instruction if we can. Otherwise, return nullptr.
    switch (getKind()) {
    case ProjectionKind::Struct:
        return B.createStructExtract(Loc, Base, cast<VarDecl>(getDecl()));
    case ProjectionKind::Tuple:
        return B.createTupleExtract(Loc, Base, getIndex());
    case ProjectionKind::Index:
        return nullptr;
    case ProjectionKind::Enum:
        return B.createUncheckedEnumData(Loc, Base,
                                         cast<EnumElementDecl>(getDecl()));
    case ProjectionKind::Class:
        return nullptr;
    }
}

void MemoryToRegisters::removeSingleBlockAllocation(AllocStackInst *ASI) {
  DEBUG(llvm::dbgs() << "*** Promoting in-block: " << *ASI);

  SILBasicBlock *BB = ASI->getParent();

  // The default value of the AllocStack is NULL because we don't have
  // uninitialized variables in Swift.
  SILValue RunningVal = SILValue();

  // For all instructions in the block.
  for (auto BBI = BB->begin(), E = BB->end(); BBI != E;) {
    SILInstruction *Inst = &*BBI;
    ++BBI;

    // Remove instructions that we are loading from. Replace the loaded value
    // with our running value.
    if (isLoadFromStack(Inst, ASI)) {
      if (!RunningVal) {
        assert(ASI->getElementType().isVoid() &&
               "Expected initialization of non-void type!");
        RunningVal = SILUndef::get(ASI->getElementType(), ASI->getModule());
      }
      replaceLoad(cast<LoadInst>(Inst), RunningVal, ASI);
      NumInstRemoved++;
      continue;
    }

    // Remove stores and record the value that we are saving as the running
    // value.
    if (auto *SI = dyn_cast<StoreInst>(Inst)) {
      if (SI->getDest() == ASI) {
        RunningVal = SI->getSrc();
        Inst->eraseFromParent();
        NumInstRemoved++;
        continue;
      }
    }

    // Replace debug_value_addr with debug_value of the promoted value.
    if (auto *DVAI = dyn_cast<DebugValueAddrInst>(Inst)) {
      if (DVAI->getOperand() == ASI) {
        if (RunningVal) {
          promoteDebugValueAddr(DVAI, RunningVal, B);
        } else {
          // Drop debug_value_addr of uninitialized void values.
          assert(ASI->getElementType().isVoid() &&
                 "Expected initialization of non-void type!");
          DVAI->eraseFromParent();
        }
      }
      continue;
    }

    // Replace destroys with a release of the value.
    if (auto *DAI = dyn_cast<DestroyAddrInst>(Inst)) {
      if (DAI->getOperand() == ASI) {
        replaceDestroy(DAI, RunningVal);
      }
      continue;
    }

    // Remove deallocation.
    if (auto *DSI = dyn_cast<DeallocStackInst>(Inst)) {
      if (DSI->getOperand() == ASI) {
        Inst->eraseFromParent();
        NumInstRemoved++;
        // No need to continue scanning after deallocation.
        break;
      }
    }

    SILValue InstVal = Inst;
    
    // Remove dead address instructions that may be uses of the allocation.
    while (InstVal->use_empty() && (isa<StructElementAddrInst>(InstVal) ||
                                    isa<TupleElementAddrInst>(InstVal))) {
      SILInstruction *I = cast<SILInstruction>(InstVal);
      InstVal = I->getOperand(0);
      I->eraseFromParent();
      NumInstRemoved++;
    }
  }
}

/// \brief Returns the callee SILFunction called at a call site, in the case
/// that the call is transparent (as in, both that the call is marked
/// with the transparent flag and that callee function is actually transparently
/// determinable from the SIL) or nullptr otherwise. This assumes that the SIL
/// is already in SSA form.
///
/// In the case that a non-null value is returned, FullArgs contains effective
/// argument operands for the callee function.
static SILFunction *
getCalleeFunction(FullApplySite AI, bool &IsThick,
                  SmallVectorImpl<SILValue>& CaptureArgs,
                  SmallVectorImpl<SILValue>& FullArgs,
                  PartialApplyInst *&PartialApply,
                  SILModule::LinkingMode Mode) {
  IsThick = false;
  PartialApply = nullptr;
  CaptureArgs.clear();
  FullArgs.clear();

  for (const auto &Arg : AI.getArguments())
    FullArgs.push_back(Arg);
  SILValue CalleeValue = AI.getCallee();

  if (LoadInst *LI = dyn_cast<LoadInst>(CalleeValue)) {
    assert(CalleeValue.getResultNumber() == 0);
    // Conservatively only see through alloc_box; we assume this pass is run
    // immediately after SILGen
    SILInstruction *ABI = dyn_cast<AllocBoxInst>(LI->getOperand());
    if (!ABI)
      return nullptr;
    assert(LI->getOperand().getResultNumber() == 1);

    // Scan forward from the alloc box to find the first store, which
    // (conservatively) must be in the same basic block as the alloc box
    StoreInst *SI = nullptr;
    for (auto I = SILBasicBlock::iterator(ABI), E = I->getParent()->end();
         I != E; ++I) {
      // If we find the load instruction first, then the load is loading from
      // a non-initialized alloc; this shouldn't really happen but I'm not
      // making any assumptions
      if (static_cast<SILInstruction*>(I) == LI)
        return nullptr;
      if ((SI = dyn_cast<StoreInst>(I)) && SI->getDest().getDef() == ABI) {
        // We found a store that we know dominates the load; now ensure there
        // are no other uses of the alloc other than loads, retains, releases
        // and dealloc stacks
        for (auto UI = ABI->use_begin(), UE = ABI->use_end(); UI != UE;
             ++UI)
          if (UI.getUser() != SI && !isa<LoadInst>(UI.getUser()) &&
              !isa<StrongRetainInst>(UI.getUser()) &&
              !isa<StrongReleaseInst>(UI.getUser()))
            return nullptr;
        // We can conservatively see through the store
        break;
      }
    }
    if (!SI)
      return nullptr;
    CalleeValue = SI->getSrc();
  }

  // We are allowed to see through exactly one "partial apply" instruction or
  // one "thin to thick function" instructions, since those are the patterns
  // generated when using auto closures.
  if (PartialApplyInst *PAI =
        dyn_cast<PartialApplyInst>(CalleeValue)) {
    assert(CalleeValue.getResultNumber() == 0);

    for (const auto &Arg : PAI->getArguments()) {
      CaptureArgs.push_back(Arg);
      FullArgs.push_back(Arg);
    }

    CalleeValue = PAI->getCallee();
    IsThick = true;
    PartialApply = PAI;
  } else if (ThinToThickFunctionInst *TTTFI =
               dyn_cast<ThinToThickFunctionInst>(CalleeValue)) {
    assert(CalleeValue.getResultNumber() == 0);
    CalleeValue = TTTFI->getOperand();
    IsThick = true;
  }

  FunctionRefInst *FRI = dyn_cast<FunctionRefInst>(CalleeValue);

  if (!FRI)
    return nullptr;

  SILFunction *CalleeFunction = FRI->getReferencedFunction();

  switch (CalleeFunction->getRepresentation()) {
  case SILFunctionTypeRepresentation::Thick:
  case SILFunctionTypeRepresentation::Thin:
  case SILFunctionTypeRepresentation::Method:
  case SILFunctionTypeRepresentation::WitnessMethod:
    break;
    
  case SILFunctionTypeRepresentation::CFunctionPointer:
  case SILFunctionTypeRepresentation::ObjCMethod:
  case SILFunctionTypeRepresentation::Block:
//.........这里部分代码省略.........

/// Generate a new apply of a function_ref to replace an apply of a
/// witness_method when we've determined the actual function we'll end
/// up calling.
static ApplySite devirtualizeWitnessMethod(ApplySite AI, SILFunction *F,
                                           ArrayRef<Substitution> Subs) {
  // We know the witness thunk and the corresponding set of substitutions
  // required to invoke the protocol method at this point.
  auto &Module = AI.getModule();

  // Collect all the required substitutions.
  //
  // The complete set of substitutions may be different, e.g. because the found
  // witness thunk F may have been created by a  specialization pass and have
  // additional generic parameters.
  SmallVector<Substitution, 16> NewSubstList(Subs.begin(), Subs.end());

  // Add the non-self-derived substitutions from the original application.
  ArrayRef<Substitution>  SubstList;
  SubstList = AI.getSubstitutionsWithoutSelfSubstitution();

  for (auto &origSub : SubstList)
    if (!origSub.getArchetype()->isSelfDerived())
      NewSubstList.push_back(origSub);

  // Figure out the exact bound type of the function to be called by
  // applying all substitutions.
  auto CalleeCanType = F->getLoweredFunctionType();
  auto SubstCalleeCanType = CalleeCanType->substGenericArgs(
    Module, Module.getSwiftModule(), NewSubstList);

  // Collect arguments from the apply instruction.
  auto Arguments = SmallVector<SILValue, 4>();

  auto ParamTypes = SubstCalleeCanType->getParameterSILTypes();

  // Iterate over the non self arguments and add them to the
  // new argument list, upcasting when required.
  SILBuilderWithScope B(AI.getInstruction());
  for (unsigned ArgN = 0, ArgE = AI.getNumArguments(); ArgN != ArgE; ++ArgN) {
    SILValue A = AI.getArgument(ArgN);
    auto ParamType = ParamTypes[ParamTypes.size() - AI.getNumArguments() + ArgN];
    if (A.getType() != ParamType)
      A = B.createUpcast(AI.getLoc(), A, ParamType);

    Arguments.push_back(A);
  }

  // Replace old apply instruction by a new apply instruction that invokes
  // the witness thunk.
  SILBuilderWithScope Builder(AI.getInstruction());
  SILLocation Loc = AI.getLoc();
  FunctionRefInst *FRI = Builder.createFunctionRef(Loc, F);

  auto SubstCalleeSILType = SILType::getPrimitiveObjectType(SubstCalleeCanType);
  auto ResultSILType = SubstCalleeCanType->getSILResult();
  ApplySite SAI;

  if (auto *A = dyn_cast<ApplyInst>(AI))
    SAI = Builder.createApply(Loc, FRI, SubstCalleeSILType,
                              ResultSILType, NewSubstList, Arguments,
                              A->isNonThrowing());
  if (auto *TAI = dyn_cast<TryApplyInst>(AI))
    SAI = Builder.createTryApply(Loc, FRI, SubstCalleeSILType,
                                 NewSubstList, Arguments,
                                 TAI->getNormalBB(), TAI->getErrorBB());
  if (auto *PAI = dyn_cast<PartialApplyInst>(AI))
    SAI = Builder.createPartialApply(Loc, FRI, SubstCalleeSILType,
                                     NewSubstList, Arguments, PAI->getType());

  NumWitnessDevirt++;
  return SAI;
}

/// \brief Devirtualize an apply of a class method.
///
/// \p AI is the apply to devirtualize.
/// \p ClassOrMetatype is a class value or metatype value that is the
///    self argument of the apply we will devirtualize.
/// return the result value of the new ApplyInst if created one or null.
DevirtualizationResult swift::devirtualizeClassMethod(FullApplySite AI,
                                                     SILValue ClassOrMetatype) {
  DEBUG(llvm::dbgs() << "    Trying to devirtualize : " << *AI.getInstruction());

  SILModule &Mod = AI.getModule();
  auto *CMI = cast<ClassMethodInst>(AI.getCallee());
  auto ClassOrMetatypeType = ClassOrMetatype.getType();
  auto *F = getTargetClassMethod(Mod, ClassOrMetatypeType, CMI->getMember());

  CanSILFunctionType GenCalleeType = F->getLoweredFunctionType();

  auto Subs = getSubstitutionsForCallee(Mod, GenCalleeType,
                                        ClassOrMetatypeType, AI);
  CanSILFunctionType SubstCalleeType = GenCalleeType;
  if (GenCalleeType->isPolymorphic())
    SubstCalleeType = GenCalleeType->substGenericArgs(Mod, Mod.getSwiftModule(), Subs);

  SILBuilderWithScope B(AI.getInstruction());
  FunctionRefInst *FRI = B.createFunctionRef(AI.getLoc(), F);

  // Create the argument list for the new apply, casting when needed
  // in order to handle covariant indirect return types and
  // contravariant argument types.
  llvm::SmallVector<SILValue, 8> NewArgs;
  auto Args = AI.getArguments();
  auto ParamTypes = SubstCalleeType->getParameterSILTypes();

  for (unsigned i = 0, e = Args.size() - 1; i != e; ++i)
    NewArgs.push_back(castValueToABICompatibleType(&B, AI.getLoc(), Args[i],
                                                   Args[i].getType(),
                                                   ParamTypes[i]).getValue());

  // Add the self argument, upcasting if required because we're
  // calling a base class's method.
  auto SelfParamTy = SubstCalleeType->getSelfParameter().getSILType();
  NewArgs.push_back(castValueToABICompatibleType(&B, AI.getLoc(),
                                                 ClassOrMetatype,
                                                 ClassOrMetatypeType,
                                                 SelfParamTy).getValue());

  // If we have a direct return type, make sure we use the subst callee return
  // type. If we have an indirect return type, AI's return type of the empty
  // tuple should be ok.
  SILType ResultTy = AI.getType();
  if (!SubstCalleeType->hasIndirectResult()) {
    ResultTy = SubstCalleeType->getSILResult();
  }

  SILType SubstCalleeSILType =
    SILType::getPrimitiveObjectType(SubstCalleeType);
  FullApplySite NewAI;

  SILBasicBlock *ResultBB = nullptr;
  SILBasicBlock *NormalBB = nullptr;
  SILValue ResultValue;
  bool ResultCastRequired = false;
  SmallVector<Operand *, 4> OriginalResultUses;

  if (!isa<TryApplyInst>(AI)) {
    NewAI = B.createApply(AI.getLoc(), FRI, SubstCalleeSILType, ResultTy,
                          Subs, NewArgs, cast<ApplyInst>(AI)->isNonThrowing());
    ResultValue = SILValue(NewAI.getInstruction(), 0);
  } else {
    auto *TAI = cast<TryApplyInst>(AI);
    // Create new normal and error BBs only if:
    // - re-using a BB would create a critical edge
    // - or, the result of the new apply would be of different
    //   type than the argument of the original normal BB.
    if (TAI->getNormalBB()->getSinglePredecessor())
      ResultBB = TAI->getNormalBB();
    else {
      ResultBB = B.getFunction().createBasicBlock();
      ResultBB->createBBArg(ResultTy);
    }

    NormalBB = TAI->getNormalBB();

    SILBasicBlock *ErrorBB = nullptr;
    if (TAI->getErrorBB()->getSinglePredecessor())
      ErrorBB = TAI->getErrorBB();
    else {
      ErrorBB = B.getFunction().createBasicBlock();
      ErrorBB->createBBArg(TAI->getErrorBB()->getBBArg(0)->getType());
    }

    NewAI = B.createTryApply(AI.getLoc(), FRI, SubstCalleeSILType,
                             Subs, NewArgs,
                             ResultBB, ErrorBB);
    if (ErrorBB != TAI->getErrorBB()) {
      B.setInsertionPoint(ErrorBB);
      B.createBranch(TAI->getLoc(), TAI->getErrorBB(),
                     {ErrorBB->getBBArg(0)});
    }

//.........这里部分代码省略.........

ManagedValue SILGenFunction::emitExistentialErasure(
                            SILLocation loc,
                            CanType concreteFormalType,
                            const TypeLowering &concreteTL,
                            const TypeLowering &existentialTL,
                            const ArrayRef<ProtocolConformance *> &conformances,
                            SGFContext C,
                            llvm::function_ref<ManagedValue (SGFContext)> F) {
  // Mark the needed conformances as used.
  for (auto *conformance : conformances)
    SGM.useConformance(conformance);

  switch (existentialTL.getLoweredType().getObjectType()
            .getPreferredExistentialRepresentation(SGM.M, concreteFormalType)) {
  case ExistentialRepresentation::None:
    llvm_unreachable("not an existential type");
  case ExistentialRepresentation::Metatype: {
    assert(existentialTL.isLoadable());

    SILValue metatype = F(SGFContext()).getUnmanagedValue();
    assert(metatype.getType().castTo<AnyMetatypeType>()->getRepresentation()
             == MetatypeRepresentation::Thick);

    auto upcast =
      B.createInitExistentialMetatype(loc, metatype,
                                      existentialTL.getLoweredType(),
                                      conformances);
    return ManagedValue::forUnmanaged(upcast);
  }
  case ExistentialRepresentation::Class: {
    assert(existentialTL.isLoadable());

    ManagedValue sub = F(SGFContext());
    SILValue v = B.createInitExistentialRef(loc,
                                            existentialTL.getLoweredType(),
                                            concreteFormalType,
                                            sub.getValue(),
                                            conformances);
    return ManagedValue(v, sub.getCleanup());
  }
  case ExistentialRepresentation::Boxed: {
    // Allocate the existential.
    auto box = B.createAllocExistentialBox(loc,
                                           existentialTL.getLoweredType(),
                                           concreteFormalType,
                                           concreteTL.getLoweredType(),
                                           conformances);
    auto existential = box->getExistentialResult();
    auto valueAddr = box->getValueAddressResult();

    // Initialize the concrete value in-place.
    InitializationPtr init(
        new ExistentialInitialization(existential, valueAddr, concreteFormalType,
                                      ExistentialRepresentation::Boxed,
                                      *this));
    ManagedValue mv = F(SGFContext(init.get()));
    if (!mv.isInContext()) {
      mv.forwardInto(*this, loc, init->getAddress());
      init->finishInitialization(*this);
    }
    
    return emitManagedRValueWithCleanup(existential);
  }
  case ExistentialRepresentation::Opaque: {
    // Allocate the existential.
    SILValue existential =
      getBufferForExprResult(loc, existentialTL.getLoweredType(), C);

    // Allocate the concrete value inside the container.
    SILValue valueAddr = B.createInitExistentialAddr(
                            loc, existential,
                            concreteFormalType,
                            concreteTL.getLoweredType(),
                            conformances);
    // Initialize the concrete value in-place.
    InitializationPtr init(
        new ExistentialInitialization(existential, valueAddr, concreteFormalType,
                                      ExistentialRepresentation::Opaque,
                                      *this));
    ManagedValue mv = F(SGFContext(init.get()));
    if (!mv.isInContext()) {
      mv.forwardInto(*this, loc, init->getAddress());
      init->finishInitialization(*this);
    }

    return manageBufferForExprResult(existential, existentialTL, C);
  }
  }
}

static bool isNonInoutIndirectSILArgument(SILValue Arg,
                                          SILArgumentConvention ArgConvention) {
  return !Arg->getType().isObject() && ArgConvention.isIndirectConvention() &&
         ArgConvention != SILArgumentConvention::Indirect_Inout &&
         ArgConvention != SILArgumentConvention::Indirect_InoutAliasable;
}

// Attempt to remove the array allocated at NewAddrValue and release its
// refcounted elements.
//
// This is tightly coupled with the implementation of array.uninitialized.
// The call to allocate an uninitialized array returns two values:
// (Array<E> ArrayBase, UnsafeMutable<E> ArrayElementStorage)
//
// TODO: This relies on the lowest level array.uninitialized not being
// inlined. To do better we could either run this pass before semantic inlining,
// or we could also handle calls to array.init.
static bool removeAndReleaseArray(SILValue NewArrayValue) {
  TupleExtractInst *ArrayDef = nullptr;
  TupleExtractInst *StorageAddress = nullptr;
  for (auto *Op : NewArrayValue->getUses()) {
    auto *TupleElt = dyn_cast<TupleExtractInst>(Op->getUser());
    if (!TupleElt)
      return false;
    switch (TupleElt->getFieldNo()) {
    default:
      return false;
    case 0:
      ArrayDef = TupleElt;
      break;
    case 1:
      StorageAddress = TupleElt;
      break;
    }
  }
  if (!ArrayDef)
    return false; // No Array object to delete.

  assert(!ArrayDef->getType().isTrivial(ArrayDef->getModule()) &&
         "Array initialization should produce the proper tuple type.");

  // Analyze the array object uses.
  DeadObjectAnalysis DeadArray(ArrayDef);
  if (!DeadArray.analyze())
    return false;

  // Require all stores to be into the array storage not the array object,
  // otherwise bail.
  bool HasStores = false;
  DeadArray.visitStoreLocations([&](ArrayRef<StoreInst*>){ HasStores = true; });
  if (HasStores)
    return false;

  // Remove references to empty arrays.
  if (!StorageAddress) {
    removeInstructions(DeadArray.getAllUsers());
    return true;
  }
  assert(StorageAddress->getType().isTrivial(ArrayDef->getModule()) &&
         "Array initialization should produce the proper tuple type.");

  // Analyze the array storage uses.
  DeadObjectAnalysis DeadStorage(StorageAddress);
  if (!DeadStorage.analyze())
    return false;

  // Find array object lifetime.
  ValueLifetimeAnalysis VLA(ArrayDef);
  ValueLifetime Lifetime = VLA.computeFromUserList(DeadArray.getAllUsers());

  // Check that all storage users are in the Array's live blocks and never the
  // last user.
  for (auto *User : DeadStorage.getAllUsers()) {
    auto *BB = User->getParent();
    if (!VLA.successorHasLiveIn(BB)
        && VLA.findLastSpecifiedUseInBlock(BB) == User) {
        return false;
    }
  }
  // For each store location, insert releases.
  // This makes a strong assumption that the allocated object is released on all
  // paths in which some object initialization occurs.
  SILSSAUpdater SSAUp;
  DeadStorage.visitStoreLocations([&] (ArrayRef<StoreInst*> Stores) {
      insertReleases(Stores, Lifetime.getLastUsers(), SSAUp);
    });

  // Delete all uses of the dead array and its storage address.
  removeInstructions(DeadArray.getAllUsers());
  removeInstructions(DeadStorage.getAllUsers());

  return true;
}

/// Find all closures that may be propagated into the given function-type value.
///
/// Searches the use-def chain from the given value upward until a partial_apply
/// is reached. Populates `results` with the set of partial_apply instructions.
///
/// `funcVal` may be either a function type or an Optional function type. This
/// might be called on a directly applied value or on a call argument, which may
/// in turn be applied within the callee.
void swift::findClosuresForFunctionValue(
    SILValue funcVal, TinyPtrVector<PartialApplyInst *> &results) {

  SILType funcTy = funcVal->getType();
  // Handle `Optional<@convention(block) @noescape (_)->(_)>`
  if (auto optionalObjTy = funcTy.getOptionalObjectType())
    funcTy = optionalObjTy;
  assert(funcTy.is<SILFunctionType>());

  SmallVector<SILValue, 4> worklist;
  // Avoid exponential path exploration and prevent duplicate results.
  llvm::SmallDenseSet<SILValue, 8> visited;
  auto worklistInsert = [&](SILValue V) {
    if (visited.insert(V).second)
      worklist.push_back(V);
  };
  worklistInsert(funcVal);

  while (!worklist.empty()) {
    SILValue V = worklist.pop_back_val();

    if (auto *I = V->getDefiningInstruction()) {
      // Look through copies, borrows, and conversions.
      //
      // Handle copy_block and copy_block_without_actually_escaping before
      // calling findClosureStoredIntoBlock.
      if (SingleValueInstruction *SVI = getSingleValueCopyOrCast(I)) {
        worklistInsert(SVI->getOperand(0));
        continue;
      }
    }
    // Look through Optionals.
    if (V->getType().getOptionalObjectType()) {
      auto *EI = dyn_cast<EnumInst>(V);
      if (EI && EI->hasOperand()) {
        worklistInsert(EI->getOperand());
      }
      // Ignore the .None case.
      continue;
    }
    // Look through Phis.
    //
    // This should be done before calling findClosureStoredIntoBlock.
    if (auto *arg = dyn_cast<SILPhiArgument>(V)) {
      SmallVector<std::pair<SILBasicBlock *, SILValue>, 2> blockArgs;
      arg->getIncomingPhiValues(blockArgs);
      for (auto &blockAndArg : blockArgs)
        worklistInsert(blockAndArg.second);

      continue;
    }
    // Look through ObjC closures.
    auto fnType = V->getType().getAs<SILFunctionType>();
    if (fnType
        && fnType->getRepresentation() == SILFunctionTypeRepresentation::Block) {
      if (SILValue storedClosure = findClosureStoredIntoBlock(V))
        worklistInsert(storedClosure);

      continue;
    }
    if (auto *PAI = dyn_cast<PartialApplyInst>(V)) {
      SILValue thunkArg = isPartialApplyOfReabstractionThunk(PAI);
      if (thunkArg) {
        // Handle reabstraction thunks recursively. This may reabstract over
        // @convention(block).
        worklistInsert(thunkArg);
        continue;
      }
      results.push_back(PAI);
      continue;
    }
    // Ignore other unrecognized values that feed this applied argument.
  }
}

void SILGenFunction::emitValueConstructor(ConstructorDecl *ctor) {
  MagicFunctionName = SILGenModule::getMagicFunctionName(ctor);

  if (ctor->isMemberwiseInitializer())
    return emitImplicitValueConstructor(*this, ctor);

  // True if this constructor delegates to a peer constructor with self.init().
  bool isDelegating = ctor->getDelegatingOrChainedInitKind(nullptr) ==
    ConstructorDecl::BodyInitKind::Delegating;

  // Get the 'self' decl and type.
  VarDecl *selfDecl = ctor->getImplicitSelfDecl();
  auto &lowering = getTypeLowering(selfDecl->getType()->getInOutObjectType());
  SILType selfTy = lowering.getLoweredType();
  (void)selfTy;
  assert(!selfTy.getClassOrBoundGenericClass()
         && "can't emit a class ctor here");

  // Allocate the local variable for 'self'.
  emitLocalVariableWithCleanup(selfDecl, false)->finishInitialization(*this);
  
  // Mark self as being uninitialized so that DI knows where it is and how to
  // check for it.
  SILValue selfLV;
  {
    auto &SelfVarLoc = VarLocs[selfDecl];
    auto MUIKind =  isDelegating ? MarkUninitializedInst::DelegatingSelf
                                 : MarkUninitializedInst::RootSelf;
    selfLV = B.createMarkUninitialized(selfDecl, SelfVarLoc.value, MUIKind);
    SelfVarLoc.value = selfLV;
  }
  
  // Emit the prolog.
  emitProlog(ctor->getParameterList(1), ctor->getResultType(), ctor,
             ctor->hasThrows());
  emitConstructorMetatypeArg(*this, ctor);

  // Create a basic block to jump to for the implicit 'self' return.
  // We won't emit this until after we've emitted the body.
  // The epilog takes a void return because the return of 'self' is implicit.
  prepareEpilog(Type(), ctor->hasThrows(), CleanupLocation(ctor));

  // If the constructor can fail, set up an alternative epilog for constructor
  // failure.
  SILBasicBlock *failureExitBB = nullptr;
  SILArgument *failureExitArg = nullptr;
  auto &resultLowering = getTypeLowering(ctor->getResultType());

  if (ctor->getFailability() != OTK_None) {
    SILBasicBlock *failureBB = createBasicBlock(FunctionSection::Postmatter);

    // On failure, we'll clean up everything (except self, which should have
    // been cleaned up before jumping here) and return nil instead.
    SavedInsertionPoint savedIP(*this, failureBB, FunctionSection::Postmatter);
    failureExitBB = createBasicBlock();
    Cleanups.emitCleanupsForReturn(ctor);
    // Return nil.
    if (lowering.isAddressOnly()) {
      // Inject 'nil' into the indirect return.
      assert(F.getIndirectResults().size() == 1);
      B.createInjectEnumAddr(ctor, F.getIndirectResults()[0],
                             getASTContext().getOptionalNoneDecl());
      B.createBranch(ctor, failureExitBB);

      B.setInsertionPoint(failureExitBB);
      B.createReturn(ctor, emitEmptyTuple(ctor));
    } else {
      // Pass 'nil' as the return value to the exit BB.
      failureExitArg = new (F.getModule())
        SILArgument(failureExitBB, resultLowering.getLoweredType());
      SILValue nilResult =
        B.createEnum(ctor, {}, getASTContext().getOptionalNoneDecl(),
                     resultLowering.getLoweredType());
      B.createBranch(ctor, failureExitBB, nilResult);

      B.setInsertionPoint(failureExitBB);
      B.createReturn(ctor, failureExitArg);
    }

    FailDest = JumpDest(failureBB, Cleanups.getCleanupsDepth(), ctor);
  }

  // If this is not a delegating constructor, emit member initializers.
  if (!isDelegating) {
    auto *dc = ctor->getDeclContext();
    auto *nominal = dc->getAsNominalTypeOrNominalTypeExtensionContext();
    emitMemberInitializers(dc, selfDecl, nominal);
  }

  emitProfilerIncrement(ctor->getBody());
  // Emit the constructor body.
  emitStmt(ctor->getBody());

  
  // Build a custom epilog block, since the AST representation of the
  // constructor decl (which has no self in the return type) doesn't match the
  // SIL representation.
  SILValue selfValue;
  {
    SavedInsertionPoint savedIP(*this, ReturnDest.getBlock());
//.........这里部分代码省略.........

void SILGenFunction::emitClassConstructorAllocator(ConstructorDecl *ctor) {
  assert(!ctor->isFactoryInit() && "factories should not be emitted here");

  // Emit the prolog. Since we're just going to forward our args directly
  // to the initializer, don't allocate local variables for them.
  RegularLocation Loc(ctor);
  Loc.markAutoGenerated();

  // Forward the constructor arguments.
  // FIXME: Handle 'self' along with the other body patterns.
  SmallVector<SILValue, 8> args;
  bindParametersForForwarding(ctor->getParameterList(1), args);

  SILValue selfMetaValue = emitConstructorMetatypeArg(*this, ctor);

  // Allocate the "self" value.
  VarDecl *selfDecl = ctor->getImplicitSelfDecl();
  SILType selfTy = getLoweredType(selfDecl->getType());
  assert(selfTy.hasReferenceSemantics() &&
         "can't emit a value type ctor here");

  // Use alloc_ref to allocate the object.
  // TODO: allow custom allocation?
  // FIXME: should have a cleanup in case of exception
  auto selfClassDecl = ctor->getDeclContext()->getAsClassOrClassExtensionContext();

  SILValue selfValue;

  // Allocate the 'self' value.
  bool useObjCAllocation = usesObjCAllocator(selfClassDecl);

  if (ctor->isConvenienceInit() || ctor->hasClangNode()) {
    // For a convenience initializer or an initializer synthesized
    // for an Objective-C class, allocate using the metatype.
    SILValue allocArg = selfMetaValue;

    // When using Objective-C allocation, convert the metatype
    // argument to an Objective-C metatype.
    if (useObjCAllocation) {
      auto metaTy = allocArg->getType().castTo<MetatypeType>();
      metaTy = CanMetatypeType::get(metaTy.getInstanceType(),
                                    MetatypeRepresentation::ObjC);
      allocArg = B.createThickToObjCMetatype(Loc, allocArg,
                                             getLoweredType(metaTy));
    }

    selfValue = B.createAllocRefDynamic(Loc, allocArg, selfTy,
                                        useObjCAllocation, {}, {});
  } else {
    // For a designated initializer, we know that the static type being
    // allocated is the type of the class that defines the designated
    // initializer.
    selfValue = B.createAllocRef(Loc, selfTy, useObjCAllocation, false, {}, {});
  }
  args.push_back(selfValue);

  // Call the initializer. Always use the Swift entry point, which will be a
  // bridging thunk if we're calling ObjC.
  SILDeclRef initConstant =
    SILDeclRef(ctor,
               SILDeclRef::Kind::Initializer,
               SILDeclRef::ConstructAtBestResilienceExpansion,
               SILDeclRef::ConstructAtNaturalUncurryLevel,
               /*isObjC=*/false);

  ManagedValue initVal;
  SILType initTy;

  ArrayRef<Substitution> subs;
  // Call the initializer.
  ArrayRef<Substitution> forwardingSubs;
  if (auto *genericEnv = ctor->getGenericEnvironmentOfContext()) {
    auto *genericSig = ctor->getGenericSignatureOfContext();
    forwardingSubs = genericEnv->getForwardingSubstitutions(
        SGM.SwiftModule, genericSig);
  }
  std::tie(initVal, initTy, subs)
    = emitSiblingMethodRef(Loc, selfValue, initConstant, forwardingSubs);

  SILValue initedSelfValue = emitApplyWithRethrow(Loc, initVal.forward(*this),
                                                  initTy, subs, args);

  // Return the