// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#include "vm/dart_entry.h"

#include "vm/class_finalizer.h"
#include "vm/compiler/jit/compiler.h"
#include "vm/debugger.h"
#include "vm/object_store.h"
#include "vm/resolver.h"
#include "vm/runtime_entry.h"
#include "vm/safepoint.h"
#include "vm/simulator.h"
#include "vm/stub_code.h"
#include "vm/symbols.h"

namespace dart {

// A cache of VM heap allocated arguments descriptors.
RawArray* ArgumentsDescriptor::cached_args_descriptors_[kCachedDescriptorCount];

RawObject* DartEntry::InvokeFunction(const Function& function,
                                     const Array& arguments) {
  ASSERT(Thread::Current()->IsMutatorThread());
  const int kTypeArgsLen = 0;  // No support to pass type args to generic func.
  const Array& arguments_descriptor =
      Array::Handle(ArgumentsDescriptor::New(kTypeArgsLen, arguments.Length()));
  return InvokeFunction(function, arguments, arguments_descriptor);
}

class ScopedIsolateStackLimits : public ValueObject {
 public:
  explicit ScopedIsolateStackLimits(Thread* thread, uword current_sp)
      : thread_(thread), saved_stack_limit_(0) {
    ASSERT(thread != NULL);
    // Set the thread's stack_base based on the current
    // stack pointer, we keep refining this value as we
    // see higher stack pointers (Note: we assume the stack
    // grows from high to low addresses).
    OSThread* os_thread = thread->os_thread();
    ASSERT(os_thread != NULL);
    if (current_sp > os_thread->stack_base()) {
      os_thread->set_stack_base(current_sp);
    }
    // Save the Thread's current stack limit and adjust the stack
    // limit based on the thread's stack_base.
    ASSERT(thread->isolate() == Isolate::Current());
    saved_stack_limit_ = thread->saved_stack_limit();
    thread->SetStackLimitFromStackBase(os_thread->stack_base());
  }

  ~ScopedIsolateStackLimits() {
    ASSERT(thread_->isolate() == Isolate::Current());
    // Since we started with a stack limit of 0 we should be getting back
    // to a stack limit of 0 when all nested invocations are done and
    // we have bottomed out.
    thread_->SetStackLimit(saved_stack_limit_);
  }

 private:
  Thread* thread_;
  uword saved_stack_limit_;
};

// Clears/restores Thread::long_jump_base on construction/destruction.
// Ensures that we do not attempt to long jump across Dart frames.
class SuspendLongJumpScope : public StackResource {
 public:
  explicit SuspendLongJumpScope(Thread* thread)
      : StackResource(thread), saved_long_jump_base_(thread->long_jump_base()) {
    thread->set_long_jump_base(NULL);
  }

  ~SuspendLongJumpScope() {
    ASSERT(thread()->long_jump_base() == NULL);
    thread()->set_long_jump_base(saved_long_jump_base_);
  }

 private:
  LongJumpScope* saved_long_jump_base_;
};

RawObject* DartEntry::InvokeFunction(const Function& function,
                                     const Array& arguments,
                                     const Array& arguments_descriptor,
                                     uword current_sp) {
  // Get the entrypoint corresponding to the function specified, this
  // will result in a compilation of the function if it is not already
  // compiled.
  Thread* thread = Thread::Current();
  Zone* zone = thread->zone();
  ASSERT(thread->IsMutatorThread());
  ScopedIsolateStackLimits stack_limit(thread, current_sp);
  if (ArgumentsDescriptor(arguments_descriptor).TypeArgsLen() > 0) {
    const String& message = String::Handle(String::New(
        "Unsupported invocation of Dart generic function with type arguments"));
    return ApiError::New(message);
  }
  if (!function.HasCode()) {
    const Object& result =
        Object::Handle(zone, Compiler::CompileFunction(thread, function));
    if (result.IsError()) {
      return Error::Cast(result).raw();
    }
  }
// Now Call the invoke stub which will invoke the dart function.
#if !defined(TARGET_ARCH_DBC)
  invokestub entrypoint = reinterpret_cast<invokestub>(
      StubCode::InvokeDartCode_entry()->EntryPoint());
#endif
  const Code& code = Code::Handle(zone, function.CurrentCode());
  ASSERT(!code.IsNull());
  ASSERT(thread->no_callback_scope_depth() == 0);
  SuspendLongJumpScope suspend_long_jump_scope(thread);
  TransitionToGenerated transition(thread);
#if defined(TARGET_ARCH_DBC)
  return Simulator::Current()->Call(code, arguments_descriptor, arguments,
                                    thread);
#elif defined(USING_SIMULATOR)
  return bit_copy<RawObject*, int64_t>(Simulator::Current()->Call(
      reinterpret_cast<intptr_t>(entrypoint), reinterpret_cast<intptr_t>(&code),
      reinterpret_cast<intptr_t>(&arguments_descriptor),
      reinterpret_cast<intptr_t>(&arguments),
      reinterpret_cast<intptr_t>(thread)));
#else
  return entrypoint(code, arguments_descriptor, arguments, thread);
#endif
}

RawObject* DartEntry::InvokeClosure(const Array& arguments) {
  const int kTypeArgsLen = 0;  // No support to pass type args to generic func.
  const Array& arguments_descriptor =
      Array::Handle(ArgumentsDescriptor::New(kTypeArgsLen, arguments.Length()));
  return InvokeClosure(arguments, arguments_descriptor);
}

RawObject* DartEntry::InvokeClosure(const Array& arguments,
                                    const Array& arguments_descriptor) {
  Thread* thread = Thread::Current();
  Zone* zone = thread->zone();
  const ArgumentsDescriptor args_desc(arguments_descriptor);
  Instance& instance = Instance::Handle(zone);
  instance ^= arguments.At(args_desc.FirstArgIndex());
  // Get the entrypoint corresponding to the closure function or to the call
  // method of the instance. This will result in a compilation of the function
  // if it is not already compiled.
  Function& function = Function::Handle(zone);
  if (instance.IsCallable(&function)) {
    // Only invoke the function if its arguments are compatible.
    if (function.AreValidArgumentCounts(args_desc.TypeArgsLen(),
                                        args_desc.Count(),
                                        args_desc.NamedCount(), NULL)) {
      // The closure or non-closure object (receiver) is passed as implicit
      // first argument. It is already included in the arguments array.
      return InvokeFunction(function, arguments, arguments_descriptor);
    }
  }

  // There is no compatible 'call' method, see if there's a getter.
  if (instance.IsClosure()) {
    // Special case: closures are implemented with a call getter instead of a
    // call method. If the arguments didn't match, go to noSuchMethod instead
    // of infinitely recursing on the getter.
  } else {
    const String& getter_name = Symbols::GetCall();
    Class& cls = Class::Handle(zone, instance.clazz());
    while (!cls.IsNull()) {
      function ^= cls.LookupDynamicFunction(getter_name);
      if (!function.IsNull()) {
        Isolate* isolate = thread->isolate();
        volatile uword c_stack_pos = Thread::GetCurrentStackPointer();
        volatile uword c_stack_limit = OSThread::Current()->stack_base() -
                                       OSThread::GetSpecifiedStackSize();
#if !defined(USING_SIMULATOR)
        ASSERT(c_stack_limit == thread->saved_stack_limit());
#endif

        if (c_stack_pos < c_stack_limit) {
          const Instance& exception =
              Instance::Handle(zone, isolate->object_store()->stack_overflow());
          return UnhandledException::New(exception, StackTrace::Handle(zone));
        }

        const Array& getter_arguments = Array::Handle(zone, Array::New(1));
        getter_arguments.SetAt(0, instance);
        const Object& getter_result = Object::Handle(
            zone, DartEntry::InvokeFunction(function, getter_arguments));
        if (getter_result.IsError()) {
          return getter_result.raw();
        }
        ASSERT(getter_result.IsNull() || getter_result.IsInstance());

        arguments.SetAt(0, getter_result);
        // This otherwise unnecessary handle is used to prevent clang from
        // doing tail call elimination, which would make the stack overflow
        // check above ineffective.
        Object& result = Object::Handle(
            zone, InvokeClosure(arguments, arguments_descriptor));
        return result.raw();
      }
      cls = cls.SuperClass();
    }
  }

  // No compatible method or getter so invoke noSuchMethod.
  return InvokeNoSuchMethod(instance, Symbols::Call(), arguments,
                            arguments_descriptor);
}

RawObject* DartEntry::InvokeNoSuchMethod(const Instance& receiver,
                                         const String& target_name,
                                         const Array& arguments,
                                         const Array& arguments_descriptor) {
  const ArgumentsDescriptor args_desc(arguments_descriptor);
  ASSERT(receiver.raw() == arguments.At(args_desc.FirstArgIndex()));
  // Allocate an Invocation object.
  const Library& core_lib = Library::Handle(Library::CoreLibrary());

  Class& invocation_mirror_class = Class::Handle(core_lib.LookupClass(
      String::Handle(core_lib.PrivateName(Symbols::InvocationMirror()))));
  ASSERT(!invocation_mirror_class.IsNull());
  const String& function_name =
      String::Handle(core_lib.PrivateName(Symbols::AllocateInvocationMirror()));
  const Function& allocation_function = Function::Handle(
      invocation_mirror_class.LookupStaticFunction(function_name));
  ASSERT(!allocation_function.IsNull());
  const int kNumAllocationArgs = 4;
  const Array& allocation_args = Array::Handle(Array::New(kNumAllocationArgs));
  allocation_args.SetAt(0, target_name);
  allocation_args.SetAt(1, arguments_descriptor);
  allocation_args.SetAt(2, arguments);
  allocation_args.SetAt(3, Bool::False());  // Not a super invocation.
  const Object& invocation_mirror =
      Object::Handle(InvokeFunction(allocation_function, allocation_args));
  if (invocation_mirror.IsError()) {
    Exceptions::PropagateError(Error::Cast(invocation_mirror));
    UNREACHABLE();
  }

  // Now use the invocation mirror object and invoke NoSuchMethod.
  const int kTypeArgsLen = 0;
  const int kNumArguments = 2;
  ArgumentsDescriptor nsm_args_desc(
      Array::Handle(ArgumentsDescriptor::New(kTypeArgsLen, kNumArguments)));
  Function& function = Function::Handle(Resolver::ResolveDynamic(
      receiver, Symbols::NoSuchMethod(), nsm_args_desc));
  if (function.IsNull()) {
    ASSERT(!FLAG_lazy_dispatchers);
    // If noSuchMethod(invocation) is not found, call Object::noSuchMethod.
    Thread* thread = Thread::Current();
    function ^= Resolver::ResolveDynamicForReceiverClass(
        Class::Handle(thread->zone(),
                      thread->isolate()->object_store()->object_class()),
        Symbols::NoSuchMethod(), nsm_args_desc);
  }
  ASSERT(!function.IsNull());
  const Array& args = Array::Handle(Array::New(kNumArguments));
  args.SetAt(0, receiver);
  args.SetAt(1, invocation_mirror);
  return InvokeFunction(function, args);
}

ArgumentsDescriptor::ArgumentsDescriptor(const Array& array) : array_(array) {}

intptr_t ArgumentsDescriptor::TypeArgsLen() const {
  return Smi::Cast(Object::Handle(array_.At(kTypeArgsLenIndex))).Value();
}

intptr_t ArgumentsDescriptor::Count() const {
  return Smi::Cast(Object::Handle(array_.At(kCountIndex))).Value();
}

intptr_t ArgumentsDescriptor::PositionalCount() const {
  return Smi::Cast(Object::Handle(array_.At(kPositionalCountIndex))).Value();
}

RawString* ArgumentsDescriptor::NameAt(intptr_t index) const {
  const intptr_t offset =
      kFirstNamedEntryIndex + (index * kNamedEntrySize) + kNameOffset;
  String& result = String::Handle();
  result ^= array_.At(offset);
  return result.raw();
}

intptr_t ArgumentsDescriptor::PositionAt(intptr_t index) const {
  const intptr_t offset =
      kFirstNamedEntryIndex + (index * kNamedEntrySize) + kPositionOffset;
  return Smi::Value(Smi::RawCast(array_.At(offset)));
}

bool ArgumentsDescriptor::MatchesNameAt(intptr_t index,
                                        const String& other) const {
  return NameAt(index) == other.raw();
}

intptr_t ArgumentsDescriptor::type_args_len_offset() {
  return Array::element_offset(kTypeArgsLenIndex);
}

intptr_t ArgumentsDescriptor::count_offset() {
  return Array::element_offset(kCountIndex);
}

intptr_t ArgumentsDescriptor::positional_count_offset() {
  return Array::element_offset(kPositionalCountIndex);
}

intptr_t ArgumentsDescriptor::first_named_entry_offset() {
  return Array::element_offset(kFirstNamedEntryIndex);
}

RawArray* ArgumentsDescriptor::New(intptr_t type_args_len,
                                   intptr_t num_arguments,
                                   const Array& optional_arguments_names) {
  const intptr_t num_named_args =
      optional_arguments_names.IsNull() ? 0 : optional_arguments_names.Length();
  if (num_named_args == 0) {
    return ArgumentsDescriptor::New(type_args_len, num_arguments);
  }
  ASSERT(type_args_len >= 0);
  ASSERT(num_arguments >= 0);
  const intptr_t num_pos_args = num_arguments - num_named_args;

  // Build the arguments descriptor array, which consists of the the type
  // argument vector length (0 if none); total argument count; the positional
  // argument count; a sequence of (name, position) pairs, sorted by name, for
  // each named optional argument; and a terminating null to simplify iterating
  // in generated code.
  Thread* thread = Thread::Current();
  Zone* zone = thread->zone();
  const intptr_t descriptor_len = LengthFor(num_named_args);
  Array& descriptor =
      Array::Handle(zone, Array::New(descriptor_len, Heap::kOld));

  // Set length of type argument vector.
  descriptor.SetAt(kTypeArgsLenIndex, Smi::Handle(Smi::New(type_args_len)));
  // Set total number of passed arguments.
  descriptor.SetAt(kCountIndex, Smi::Handle(Smi::New(num_arguments)));
  // Set number of positional arguments.
  descriptor.SetAt(kPositionalCountIndex, Smi::Handle(Smi::New(num_pos_args)));
  // Set alphabetically sorted entries for named arguments.
  String& name = String::Handle(zone);
  Smi& pos = Smi::Handle(zone);
  String& previous_name = String::Handle(zone);
  Smi& previous_pos = Smi::Handle(zone);
  for (intptr_t i = 0; i < num_named_args; i++) {
    name ^= optional_arguments_names.At(i);
    pos = Smi::New(num_pos_args + i);
    intptr_t insert_index = kFirstNamedEntryIndex + (kNamedEntrySize * i);
    // Shift already inserted pairs with "larger" names.
    while (insert_index > kFirstNamedEntryIndex) {
      intptr_t previous_index = insert_index - kNamedEntrySize;
      previous_name ^= descriptor.At(previous_index + kNameOffset);
      intptr_t result = name.CompareTo(previous_name);
      ASSERT(result != 0);  // Duplicate argument names checked in parser.
      if (result > 0) break;
      previous_pos ^= descriptor.At(previous_index + kPositionOffset);
      descriptor.SetAt(insert_index + kNameOffset, previous_name);
      descriptor.SetAt(insert_index + kPositionOffset, previous_pos);
      insert_index = previous_index;
    }
    // Insert pair in descriptor array.
    descriptor.SetAt(insert_index + kNameOffset, name);
    descriptor.SetAt(insert_index + kPositionOffset, pos);
  }
  // Set terminating null.
  descriptor.SetAt(descriptor_len - 1, Object::null_object());

  // Share the immutable descriptor when possible by canonicalizing it.
  descriptor.MakeImmutable();
  descriptor ^= descriptor.CheckAndCanonicalize(thread, NULL);
  ASSERT(!descriptor.IsNull());
  return descriptor.raw();
}

RawArray* ArgumentsDescriptor::New(intptr_t type_args_len,
                                   intptr_t num_arguments) {
  ASSERT(type_args_len >= 0);
  ASSERT(num_arguments >= 0);
  if ((type_args_len == 0) && (num_arguments < kCachedDescriptorCount)) {
    return cached_args_descriptors_[num_arguments];
  }
  return NewNonCached(type_args_len, num_arguments);
}

RawArray* ArgumentsDescriptor::NewNonCached(intptr_t type_args_len,
                                            intptr_t num_arguments,
                                            bool canonicalize) {
  // Build the arguments descriptor array, which consists of the length of the
  // type argument vector, total argument count; the positional argument count;
  // and a terminating null to simplify iterating in generated code.
  Thread* thread = Thread::Current();
  Zone* zone = thread->zone();
  const intptr_t descriptor_len = LengthFor(0);
  Array& descriptor =
      Array::Handle(zone, Array::New(descriptor_len, Heap::kOld));
  const Smi& arg_count = Smi::Handle(zone, Smi::New(num_arguments));

  // Set type argument vector length.
  descriptor.SetAt(kTypeArgsLenIndex,
                   Smi::Handle(zone, Smi::New(type_args_len)));

  // Set total number of passed arguments.
  descriptor.SetAt(kCountIndex, arg_count);

  // Set number of positional arguments.
  descriptor.SetAt(kPositionalCountIndex, arg_count);

  // Set terminating null.
  descriptor.SetAt((descriptor_len - 1), Object::null_object());

  // Share the immutable descriptor when possible by canonicalizing it.
  descriptor.MakeImmutable();
  if (canonicalize) {
    descriptor ^= descriptor.CheckAndCanonicalize(thread, NULL);
  }
  ASSERT(!descriptor.IsNull());
  return descriptor.raw();
}

void ArgumentsDescriptor::InitOnce() {
  for (int i = 0; i < kCachedDescriptorCount; i++) {
    cached_args_descriptors_[i] =
        ArgumentsDescriptor::NewNonCached(/*type_args_len=*/0, i, false);
  }
}

RawObject* DartLibraryCalls::InstanceCreate(const Library& lib,
                                            const String& class_name,
                                            const String& constructor_name,
                                            const Array& arguments) {
  const Class& cls = Class::Handle(lib.LookupClassAllowPrivate(class_name));
  ASSERT(!cls.IsNull());
  // For now, we only support a non-parameterized or raw type.
  const int kNumExtraArgs = 1;  // implicit rcvr arg.
  const Instance& exception_object = Instance::Handle(Instance::New(cls));
  const Array& constructor_arguments =
      Array::Handle(Array::New(arguments.Length() + kNumExtraArgs));
  constructor_arguments.SetAt(0, exception_object);
  Object& obj = Object::Handle();
  for (intptr_t i = 0; i < arguments.Length(); i++) {
    obj = arguments.At(i);
    constructor_arguments.SetAt((i + kNumExtraArgs), obj);
  }

  const String& function_name =
      String::Handle(String::Concat(class_name, constructor_name));
  const Function& constructor =
      Function::Handle(cls.LookupConstructorAllowPrivate(function_name));
  ASSERT(!constructor.IsNull());
  const Object& retval = Object::Handle(
      DartEntry::InvokeFunction(constructor, constructor_arguments));
  ASSERT(retval.IsNull() || retval.IsError());
  if (retval.IsError()) {
    return retval.raw();
  }
  return exception_object.raw();
}

RawObject* DartLibraryCalls::ToString(const Instance& receiver) {
  const int kTypeArgsLen = 0;
  const int kNumArguments = 1;  // Receiver.
  ArgumentsDescriptor args_desc(
      Array::Handle(ArgumentsDescriptor::New(kTypeArgsLen, kNumArguments)));
  const Function& function = Function::Handle(
      Resolver::ResolveDynamic(receiver, Symbols::toString(), args_desc));
  ASSERT(!function.IsNull());
  const Array& args = Array::Handle(Array::New(kNumArguments));
  args.SetAt(0, receiver);
  const Object& result =
      Object::Handle(DartEntry::InvokeFunction(function, args));
  ASSERT(result.IsInstance() || result.IsError());
  return result.raw();
}

RawObject* DartLibraryCalls::HashCode(const Instance& receiver) {
  const int kTypeArgsLen = 0;
  const int kNumArguments = 1;  // Receiver.
  ArgumentsDescriptor args_desc(
      Array::Handle(ArgumentsDescriptor::New(kTypeArgsLen, kNumArguments)));
  const Function& function = Function::Handle(
      Resolver::ResolveDynamic(receiver, Symbols::hashCode(), args_desc));
  ASSERT(!function.IsNull());
  const Array& args = Array::Handle(Array::New(kNumArguments));
  args.SetAt(0, receiver);
  const Object& result =
      Object::Handle(DartEntry::InvokeFunction(function, args));
  ASSERT(result.IsInstance() || result.IsError());
  return result.raw();
}

RawObject* DartLibraryCalls::Equals(const Instance& left,
                                    const Instance& right) {
  const int kTypeArgsLen = 0;
  const int kNumArguments = 2;
  ArgumentsDescriptor args_desc(
      Array::Handle(ArgumentsDescriptor::New(kTypeArgsLen, kNumArguments)));
  const Function& function = Function::Handle(
      Resolver::ResolveDynamic(left, Symbols::EqualOperator(), args_desc));
  ASSERT(!function.IsNull());

  const Array& args = Array::Handle(Array::New(kNumArguments));
  args.SetAt(0, left);
  args.SetAt(1, right);
  const Object& result =
      Object::Handle(DartEntry::InvokeFunction(function, args));
  ASSERT(result.IsInstance() || result.IsError());
  return result.raw();
}

// On success, returns a RawInstance.  On failure, a RawError.
RawObject* DartLibraryCalls::IdentityHashCode(const Instance& object) {
  const int kNumArguments = 1;
  Thread* thread = Thread::Current();
  Zone* zone = thread->zone();
  const Library& libcore = Library::Handle(zone, Library::CoreLibrary());
  ASSERT(!libcore.IsNull());
  const Function& function = Function::Handle(
      zone, libcore.LookupFunctionAllowPrivate(Symbols::identityHashCode()));
  ASSERT(!function.IsNull());
  const Array& args = Array::Handle(zone, Array::New(kNumArguments));
  args.SetAt(0, object);
  const Object& result =
      Object::Handle(zone, DartEntry::InvokeFunction(function, args));
  ASSERT(result.IsInstance() || result.IsError());
  return result.raw();
}

RawObject* DartLibraryCalls::LookupHandler(Dart_Port port_id) {
  Thread* thread = Thread::Current();
  Zone* zone = thread->zone();
  Function& function = Function::Handle(
      zone, thread->isolate()->object_store()->lookup_port_handler());
  const int kTypeArgsLen = 0;
  const int kNumArguments = 1;
  if (function.IsNull()) {
    Library& isolate_lib = Library::Handle(zone, Library::IsolateLibrary());
    ASSERT(!isolate_lib.IsNull());
    const String& class_name = String::Handle(
        zone, isolate_lib.PrivateName(Symbols::_RawReceivePortImpl()));
    const String& function_name = String::Handle(
        zone, isolate_lib.PrivateName(Symbols::_lookupHandler()));
    function = Resolver::ResolveStatic(isolate_lib, class_name, function_name,
                                       kTypeArgsLen, kNumArguments,
                                       Object::empty_array());
    ASSERT(!function.IsNull());
    thread->isolate()->object_store()->set_lookup_port_handler(function);
  }
  const Array& args = Array::Handle(zone, Array::New(kNumArguments));
  args.SetAt(0, Integer::Handle(zone, Integer::New(port_id)));
  const Object& result =
      Object::Handle(zone, DartEntry::InvokeFunction(function, args));
  return result.raw();
}

RawObject* DartLibraryCalls::HandleMessage(const Object& handler,
                                           const Instance& message) {
  Thread* thread = Thread::Current();
  Zone* zone = thread->zone();
  Isolate* isolate = thread->isolate();
  Function& function = Function::Handle(
      zone, isolate->object_store()->handle_message_function());
  const int kTypeArgsLen = 0;
  const int kNumArguments = 2;
  if (function.IsNull()) {
    Library& isolate_lib = Library::Handle(zone, Library::IsolateLibrary());
    ASSERT(!isolate_lib.IsNull());
    const String& class_name = String::Handle(
        zone, isolate_lib.PrivateName(Symbols::_RawReceivePortImpl()));
    const String& function_name = String::Handle(
        zone, isolate_lib.PrivateName(Symbols::_handleMessage()));
    function = Resolver::ResolveStatic(isolate_lib, class_name, function_name,
                                       kTypeArgsLen, kNumArguments,
                                       Object::empty_array());
    ASSERT(!function.IsNull());
    isolate->object_store()->set_handle_message_function(function);
  }
  const Array& args = Array::Handle(zone, Array::New(kNumArguments));
  args.SetAt(0, handler);
  args.SetAt(1, message);
#if !defined(PRODUCT)
  if (isolate->debugger()->IsStepping()) {
    // If the isolate is being debugged and the debugger was stepping
    // through code, enable single stepping so debugger will stop
    // at the first location the user is interested in.
    isolate->debugger()->SetResumeAction(Debugger::kStepInto);
  }
#endif
  const Object& result =
      Object::Handle(zone, DartEntry::InvokeFunction(function, args));
  ASSERT(result.IsNull() || result.IsError());
  return result.raw();
}

RawObject* DartLibraryCalls::DrainMicrotaskQueue() {
  Zone* zone = Thread::Current()->zone();
  Library& isolate_lib = Library::Handle(zone, Library::IsolateLibrary());
  ASSERT(!isolate_lib.IsNull());
  Function& function =
      Function::Handle(zone, isolate_lib.LookupFunctionAllowPrivate(
                                 Symbols::_runPendingImmediateCallback()));
  const Object& result = Object::Handle(
      zone, DartEntry::InvokeFunction(function, Object::empty_array()));
  ASSERT(result.IsNull() || result.IsError());
  return result.raw();
}

RawObject* DartLibraryCalls::MapSetAt(const Instance& map,
                                      const Instance& key,
                                      const Instance& value) {
  const int kTypeArgsLen = 0;
  const int kNumArguments = 3;
  ArgumentsDescriptor args_desc(
      Array::Handle(ArgumentsDescriptor::New(kTypeArgsLen, kNumArguments)));
  const Function& function = Function::Handle(
      Resolver::ResolveDynamic(map, Symbols::AssignIndexToken(), args_desc));
  ASSERT(!function.IsNull());
  const Array& args = Array::Handle(Array::New(kNumArguments));
  args.SetAt(0, map);
  args.SetAt(1, key);
  args.SetAt(2, value);
  const Object& result =
      Object::Handle(DartEntry::InvokeFunction(function, args));
  return result.raw();
}

}  // namespace dart