C++ ApplySite类代码示例

static void getWitnessMethodSubstitutions(ApplySite AI, SILFunction *F,
                                          ArrayRef<Substitution> Subs,
                                          SmallVectorImpl<Substitution> &NewSubs) {
  auto &Module = AI.getModule();

  auto CalleeCanType = F->getLoweredFunctionType();

  ProtocolDecl *proto = nullptr;
  if (CalleeCanType->getRepresentation() ==
      SILFunctionTypeRepresentation::WitnessMethod) {
    proto = CalleeCanType->getDefaultWitnessMethodProtocol(
        *Module.getSwiftModule());
  }

  ArrayRef<Substitution> origSubs = AI.getSubstitutions();

  if (proto != nullptr) {
    // If the callee is a default witness method thunk, preserve substitutions
    // from the call site.
    NewSubs.append(origSubs.begin(), origSubs.end());
    return;
  }

  // If the callee is a concrete witness method thunk, apply substitutions
  // from the conformance, and drop any substitutions derived from the Self
  // type.
  NewSubs.append(Subs.begin(), Subs.end());

  if (auto generics = AI.getOrigCalleeType()->getGenericSignature()) {
    for (auto genericParam : generics->getAllDependentTypes()) {
      auto origSub = origSubs.front();
      origSubs = origSubs.slice(1);

      // If the callee is a concrete witness method thunk, we ignore
      // generic parameters derived from 'self', the generic parameter at
      // depth 0, index 0.
      auto type = genericParam->getCanonicalType();
      while (auto memberType = dyn_cast<DependentMemberType>(type)) {
        type = memberType.getBase();
      }
      auto paramType = cast<GenericTypeParamType>(type);
      if (paramType->getDepth() == 0) {
        // There shouldn't be any other parameters at this depth.
        assert(paramType->getIndex() == 0);
        continue;
      }

      // Okay, remember this substitution.
      NewSubs.push_back(origSub);
    }
  }

  assert(origSubs.empty() && "subs not parallel to dependent types");
}

/// In the cases where we can statically determine the function that
/// we'll call to, replace an apply of a witness_method with an apply
/// of a function_ref, returning the new apply.
ApplySite
swift::tryDevirtualizeWitnessMethod(ApplySite AI, OptRemark::Emitter *ORE) {
  if (!canDevirtualizeWitnessMethod(AI))
    return ApplySite();

  SILFunction *F;
  SILWitnessTable *WT;

  auto *WMI = cast<WitnessMethodInst>(AI.getCallee());

  std::tie(F, WT) =
    AI.getModule().lookUpFunctionInWitnessTable(WMI->getConformance(),
                                                WMI->getMember());

  return devirtualizeWitnessMethod(AI, F, WMI->getConformance(), ORE);
}

/// In the cases where we can statically determine the function that
/// we'll call to, replace an apply of a witness_method with an apply
/// of a function_ref, returning the new apply.
DevirtualizationResult swift::tryDevirtualizeWitnessMethod(ApplySite AI) {
  if (!canDevirtualizeWitnessMethod(AI))
    return std::make_pair(nullptr, FullApplySite());

  SILFunction *F;
  SILWitnessTable *WT;

  auto *WMI = cast<WitnessMethodInst>(AI.getCallee());

  std::tie(F, WT) =
    AI.getModule().lookUpFunctionInWitnessTable(WMI->getConformance(),
                                                WMI->getMember());

  auto Result = devirtualizeWitnessMethod(AI, F, WMI->getConformance());
  return std::make_pair(Result.getInstruction(), Result);
}

/// Find the concrete type of the existential argument. Wrapper
/// for findInitExistential in Local.h/cpp. In future, this code
/// can move to Local.h/cpp.
static bool findConcreteType(ApplySite AI, int ArgIdx, CanType &ConcreteType) {
  bool isCopied = false;
  auto Arg = AI.getArgument(ArgIdx);

  /// Ignore any unconditional cast instructions. Is it Safe? Do we need to
  /// also add UnconditionalCheckedCastAddrInst? TODO.
  if (auto *Instance = dyn_cast<UnconditionalCheckedCastInst>(Arg)) {
    Arg = Instance->getOperand();
  }

  /// Return init_existential if the Arg is global_addr.
  if (auto *GAI = dyn_cast<GlobalAddrInst>(Arg)) {
    SILValue InitExistential =
        findInitExistentialFromGlobalAddrAndApply(GAI, AI, ArgIdx);
    /// If the Arg is already init_existential, return the concrete type.
    if (InitExistential &&
        findConcreteTypeFromInitExistential(InitExistential, ConcreteType)) {
      return true;
    }
  }

  /// Handle AllocStack instruction separately.
  if (auto *Instance = dyn_cast<AllocStackInst>(Arg)) {
    if (SILValue Src =
            getAddressOfStackInit(Instance, AI.getInstruction(), isCopied)) {
      Arg = Src;
    }
  }

  /// If the Arg is already init_existential after getAddressofStackInit
  /// call, return the concrete type.
  if (findConcreteTypeFromInitExistential(Arg, ConcreteType)) {
    return true;
  }

  /// Call findInitExistential and determine the init_existential.
  ArchetypeType *OpenedArchetype = nullptr;
  SILValue OpenedArchetypeDef;
  auto FAS = FullApplySite::isa(AI.getInstruction());
  if (!FAS)
    return false;
  SILInstruction *InitExistential =
      findInitExistential(FAS.getArgumentOperands()[ArgIdx], OpenedArchetype,
                          OpenedArchetypeDef, isCopied);
  if (!InitExistential) {
    LLVM_DEBUG(llvm::dbgs() << "ExistentialSpecializer Pass: Bail! Due to "
                               "findInitExistential\n";);

ApplySite SILPerformanceInliner::specializeGeneric(
    ApplySite Apply, llvm::SmallVectorImpl<ApplySite> &NewApplies) {
  assert(NewApplies.empty() && "Expected out parameter for new applies!");

  if (!Apply.hasSubstitutions())
    return ApplySite();

  auto *Callee = Apply.getCalleeFunction();

  if (!Callee || Callee->isExternalDeclaration())
    return ApplySite();

  auto Filter = [](SILInstruction *I) -> bool {
    return ApplySite::isa(I) != ApplySite();
  };

  CloneCollector Collector(Filter);

  SILFunction *SpecializedFunction;
  auto Specialized = trySpecializeApplyOfGeneric(Apply,
                                                 SpecializedFunction,
                                                 Collector);

  if (!Specialized)
    return ApplySite();

  // Track the new applies from the specialization.
  for (auto NewCallSite : Collector.getInstructionPairs())
    NewApplies.push_back(ApplySite(NewCallSite.first));

  auto FullApply = FullApplySite::isa(Apply.getInstruction());

  if (!FullApply) {
    assert(!FullApplySite::isa(Specialized.getInstruction()) &&
           "Unexpected full apply generated!");

    // Replace the old apply with the new and delete the old.
    replaceDeadApply(Apply, Specialized.getInstruction());

    return ApplySite(Specialized);
  }

  // Replace the old apply with the new and delete the old.
  replaceDeadApply(Apply, Specialized.getInstruction());

  return Specialized;
}

/// 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,
                          ProtocolConformanceRef C, OptRemark::Emitter *ORE) {
  // 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.
  auto SubMap = getWitnessMethodSubstitutions(Module, AI, F, C);

  // 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, SubMap);

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

  // Iterate over the non self arguments and add them to the
  // new argument list, upcasting when required.
  SILBuilderWithScope B(AI.getInstruction());
  SILFunctionConventions substConv(SubstCalleeCanType, Module);
  unsigned substArgIdx = AI.getCalleeArgIndexOfFirstAppliedArg();
  for (auto arg : AI.getArguments()) {
    auto paramType = substConv.getSILArgumentType(substArgIdx++);
    if (arg->getType() != paramType)
      arg = castValueToABICompatibleType(&B, AI.getLoc(), arg,
                                         arg->getType(), paramType);
    Arguments.push_back(arg);
  }
  assert(substArgIdx == substConv.getNumSILArguments());

  // 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);

  ApplySite SAI = replaceApplySite(Builder, Loc, AI, FRI, SubMap, Arguments,
                                   substConv);

  if (ORE)
    ORE->emit([&]() {
        using namespace OptRemark;
        return RemarkPassed("WitnessMethodDevirtualized", *AI.getInstruction())
               << "Devirtualized call to " << NV("Method", F);
      });
  NumWitnessDevirt++;
  return SAI;
}

/// Recursively check for conflicts with in-progress accesses at the given
/// apply.
///
/// Any captured variable accessed by a noescape closure is considered to be
/// accessed at the point that the closure is fully applied. This includes
/// variables captured by address by the noescape closure being applied or by
/// any other noescape closure that is itself passed as an argument to that
/// closure.
///
/// (1) Use AccessSummaryAnalysis to check each argument for statically
/// enforced accesses nested within the callee.
///
/// (2) If an applied argument is itself a function type, recursively check for
/// violations on the closure being passed as an argument.
///
/// (3) Walk up the chain of partial applies to recursively visit all arguments.
///
/// Note: This handles closures that are called immediately:
///  var i = 7
///  ({ (p: inout Int) in i = 8})(&i) // Overlapping access to 'i'
///
/// Note: This handles chains of partial applies:
///   pa1 = partial_apply f(c) : $(a, b, c)
///   pa2 = partial_apply pa1(b) : $(a, b)
///   apply pa2(a)
static void checkForViolationAtApply(ApplySite Apply, AccessState &State) {
  // First, check access to variables immediately captured at this apply site.
  checkCaptureAccess(Apply, State);

  // Next, recursively check any noescape closures passed as arguments at this
  // apply site.
  TinyPtrVector<PartialApplyInst *> partialApplies;
  for (SILValue Argument : Apply.getArguments()) {
    auto FnType = getSILFunctionTypeForValue(Argument);
    if (!FnType || !FnType->isNoEscape())
      continue;

    findClosuresForFunctionValue(Argument, partialApplies);
  }
  // Continue recursively walking up the chain of applies if necessary.
  findClosuresForFunctionValue(Apply.getCallee(), partialApplies);

  for (auto *PAI : partialApplies)
    checkForViolationAtApply(ApplySite(PAI), State);
}

static void getWitnessMethodSubstitutions(ApplySite AI, SILFunction *F,
                                          ProtocolConformanceRef CRef,
                                          SmallVectorImpl<Substitution> &NewSubs) {
  auto &Module = AI.getModule();

  auto requirementSig = AI.getOrigCalleeType()->getGenericSignature();
  auto witnessThunkSig = F->getLoweredFunctionType()->getGenericSignature();

  SubstitutionList origSubs = AI.getSubstitutions();

  bool isDefaultWitness =
    F->getLoweredFunctionType()->getRepresentation()
      == SILFunctionTypeRepresentation::WitnessMethod &&
    F->getLoweredFunctionType()->getDefaultWitnessMethodProtocol(
                                                     *Module.getSwiftModule())
      == CRef.getRequirement();

  getWitnessMethodSubstitutions(Module, CRef, requirementSig, witnessThunkSig,
                                origSubs, isDefaultWitness, NewSubs);
}

/// Check if we can pass/convert all arguments of the original apply
/// as required by the found devirtualized method.
static bool
canPassOrConvertAllArguments(ApplySite AI,
                             CanSILFunctionType SubstCalleeCanType) {
  for (unsigned ArgN = 0, ArgE = AI.getNumArguments(); ArgN != ArgE; ++ArgN) {
    SILValue A = AI.getArgument(ArgN);
    auto ParamType = SubstCalleeCanType->getSILArgumentType(
      SubstCalleeCanType->getNumSILArguments() - AI.getNumArguments() + ArgN);
    // Check if we can cast the provided argument into the required
    // parameter type.
    auto FromTy = A->getType();
    auto ToTy = ParamType;
    // If types are the same, no conversion will be required.
    if (FromTy == ToTy)
      continue;
    // Otherwise, it should be possible to upcast the arguments.
    if (!isLegalUpcast(FromTy, ToTy))
      return false;
  }
  return true;
}

/// For each argument in the range of the callee arguments being applied at the
/// given apply site, use the summary analysis to determine whether the
/// arguments will be accessed in a way that conflicts with any currently in
/// progress accesses. If so, diagnose.
static void checkCaptureAccess(ApplySite Apply, AccessState &State) {
  SILFunction *Callee = Apply.getCalleeFunction();
  if (!Callee || Callee->empty())
    return;

  const AccessSummaryAnalysis::FunctionSummary &FS =
      State.ASA->getOrCreateSummary(Callee);

  for (unsigned ArgumentIndex : range(Apply.getNumArguments())) {

    unsigned CalleeIndex =
        Apply.getCalleeArgIndexOfFirstAppliedArg() + ArgumentIndex;

    const AccessSummaryAnalysis::ArgumentSummary &AS =
        FS.getAccessForArgument(CalleeIndex);

    const auto &SubAccesses = AS.getSubAccesses();

    // Is the capture accessed in the callee?
    if (SubAccesses.empty())
      continue;

    SILValue Argument = Apply.getArgument(ArgumentIndex);
    assert(Argument->getType().isAddress());

    // A valid AccessedStorage should alway sbe found because Unsafe accesses
    // are not tracked by AccessSummaryAnalysis.
    const AccessedStorage &Storage = findValidAccessedStorage(Argument);
    auto AccessIt = State.Accesses->find(Storage);

    // Are there any accesses in progress at the time of the call?
    if (AccessIt == State.Accesses->end())
      continue;

    const AccessInfo &Info = AccessIt->getSecond();
    if (auto Conflict = findConflictingArgumentAccess(AS, Storage, Info))
      State.ConflictingAccesses.push_back(*Conflict);
  }
}

static bool canDevirtualizeWitnessMethod(ApplySite AI) {
  SILFunction *F;
  SILWitnessTable *WT;

  auto *WMI = cast<WitnessMethodInst>(AI.getCallee());

  std::tie(F, WT) =
    AI.getModule().lookUpFunctionInWitnessTable(WMI->getConformance(),
                                                WMI->getMember());

  if (!F)
    return false;

  if (AI.getFunction()->isSerialized()) {
    // function_ref inside fragile function cannot reference a private or
    // hidden symbol.
    if (!F->hasValidLinkageForFragileRef())
      return false;
  }

  return true;
}

static SubstitutionMap
getWitnessMethodSubstitutions(SILModule &Module, ApplySite AI, SILFunction *F,
                              ProtocolConformanceRef CRef) {
  auto witnessFnTy = F->getLoweredFunctionType();
  assert(witnessFnTy->getRepresentation() ==
         SILFunctionTypeRepresentation::WitnessMethod);

  auto requirementSig = AI.getOrigCalleeType()->getGenericSignature();
  auto witnessThunkSig = witnessFnTy->getGenericSignature();

  SubstitutionMap origSubs = AI.getSubstitutionMap();

  auto *mod = Module.getSwiftModule();
  bool isDefaultWitness =
    (witnessFnTy->getDefaultWitnessMethodProtocol()
      == CRef.getRequirement());
  auto *classWitness = witnessFnTy->getWitnessMethodClass(*mod);

  return getWitnessMethodSubstitutions(
      mod, CRef, requirementSig, witnessThunkSig,
      origSubs, isDefaultWitness, classWitness);
}

/// In the cases where we can statically determine the function that
/// we'll call to, replace an apply of a witness_method with an apply
/// of a function_ref, returning the new apply.
DevirtualizationResult swift::tryDevirtualizeWitnessMethod(ApplySite AI) {
  SILFunction *F;
  SILWitnessTable *WT;

  auto *WMI = cast<WitnessMethodInst>(AI.getCallee());

  std::tie(F, WT) =
    AI.getModule().lookUpFunctionInWitnessTable(WMI->getConformance(),
                                                WMI->getMember());

  if (!F)
    return std::make_pair(nullptr, FullApplySite());

  if (AI.getFunction()->isFragile()) {
    // function_ref inside fragile function cannot reference a private or
    // hidden symbol.
    if (!F->hasValidLinkageForFragileRef())
      return std::make_pair(nullptr, FullApplySite());
  }

  auto Result = devirtualizeWitnessMethod(AI, F, WMI->getConformance());
  return std::make_pair(Result.getInstruction(), Result);
}

/// Helper for visitApplyAccesses that visits address-type call arguments,
/// including arguments to @noescape functions that are passed as closures to
/// the current call.
static void visitApplyAccesses(ApplySite apply,
                               llvm::function_ref<void(Operand *)> visitor) {
  for (Operand &oper : apply.getArgumentOperands()) {
    // Consider any address-type operand an access. Whether it is read or modify
    // depends on the argument convention.
    if (oper.get()->getType().isAddress()) {
      visitor(&oper);
      continue;
    }
    auto fnType = oper.get()->getType().getAs<SILFunctionType>();
    if (!fnType || !fnType->isNoEscape())
      continue;

    // When @noescape function closures are passed as arguments, their
    // arguments are considered accessed at the call site.
    TinyPtrVector<PartialApplyInst *> partialApplies;
    findClosuresForFunctionValue(oper.get(), partialApplies);
    // Recursively visit @noescape function closure arguments.
    for (auto *PAI : partialApplies)
      visitApplyAccesses(PAI, visitor);
  }
}

/// Helper for visitApplyAccesses that visits address-type call arguments,
/// including arguments to @noescape functions that are passed as closures to
/// the current call.
static void visitApplyAccesses(ApplySite apply,
                               llvm::function_ref<void(Operand *)> visitor) {
  for (Operand &oper : apply.getArgumentOperands()) {
    // Consider any address-type operand an access. Whether it is read or modify
    // depends on the argument convention.
    if (oper.get()->getType().isAddress()) {
      visitor(&oper);
      continue;
    }
    auto fnType = oper.get()->getType().getAs<SILFunctionType>();
    if (!fnType || !fnType->isNoEscape())
      continue;

    // When @noescape function closures are passed as arguments, their
    // arguments are considered accessed at the call site.
    FindClosureResult result = findClosureForAppliedArg(oper.get());
    if (!result.PAI)
      continue;

    // Recursively visit @noescape function closure arguments.
    visitApplyAccesses(result.PAI, visitor);
  }
}