text: // Copyright 2016 the V8 project authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #include "src/builtins/builtins-utils.h"
  #include "src/builtins/builtins.h"
  #include "src/code-factory.h"
  #include "src/code-stub-assembler.h"
  
  namespace v8 {
  namespace internal {
  
  namespace {
  
  void Generate_GeneratorPrototypeResume(
      CodeStubAssembler* assembler, JSGeneratorObject::ResumeMode resume_mode,
      char const* const method_name) {
    typedef CodeStubAssembler::Label Label;
    typedef compiler::Node Node;
  
    Node* receiver = assembler->Parameter(0);
    Node* value = assembler->Parameter(1);
    Node* context = assembler->Parameter(4);
    Node* closed =
        assembler->SmiConstant(Smi::FromInt(JSGeneratorObject::kGeneratorClosed));
  
    // Check if the {receiver} is actually a JSGeneratorObject.
    Label if_receiverisincompatible(assembler, Label::kDeferred);
    assembler->GotoIf(assembler->TaggedIsSmi(receiver),
                      &if_receiverisincompatible);
    Node* receiver_instance_type = assembler->LoadInstanceType(receiver);
    assembler->GotoUnless(assembler->Word32Equal(
                              receiver_instance_type,
                              assembler->Int32Constant(JS_GENERATOR_OBJECT_TYPE)),
                          &if_receiverisincompatible);
  
    // Check if the {receiver} is running or already closed.
    Node* receiver_continuation = assembler->LoadObjectField(
        receiver, JSGeneratorObject::kContinuationOffset);
    Label if_receiverisclosed(assembler, Label::kDeferred),
        if_receiverisrunning(assembler, Label::kDeferred);
    assembler->GotoIf(assembler->SmiEqual(receiver_continuation, closed),
                      &if_receiverisclosed);
    DCHECK_LT(JSGeneratorObject::kGeneratorExecuting,
              JSGeneratorObject::kGeneratorClosed);
    assembler->GotoIf(assembler->SmiLessThan(receiver_continuation, closed),
                      &if_receiverisrunning);
  
    // Resume the {receiver} using our trampoline.
    Node* result = assembler->CallStub(
        CodeFactory::ResumeGenerator(assembler->isolate()), context, value,
        receiver, assembler->SmiConstant(Smi::FromInt(resume_mode)));
    assembler->Return(result);
  
    assembler->Bind(&if_receiverisincompatible);
    {
      // The {receiver} is not a valid JSGeneratorObject.
      Node* result = assembler->CallRuntime(
          Runtime::kThrowIncompatibleMethodReceiver, context,
          assembler->HeapConstant(assembler->factory()->NewStringFromAsciiChecked(
              method_name, TENURED)),
          receiver);
      assembler->Return(result);  // Never reached.
    }
  
    assembler->Bind(&if_receiverisclosed);
    {
      Callable create_iter_result_object =
          CodeFactory::CreateIterResultObject(assembler->isolate());
  
      // The {receiver} is closed already.
      Node* result = nullptr;
      switch (resume_mode) {
        case JSGeneratorObject::kNext:
          result = assembler->CallStub(create_iter_result_object, context,
                                       assembler->UndefinedConstant(),
                                       assembler->TrueConstant());
          break;
        case JSGeneratorObject::kReturn:
          result = assembler->CallStub(create_iter_result_object, context, value,
                                       assembler->TrueConstant());
          break;
        case JSGeneratorObject::kThrow:
          result = assembler->CallRuntime(Runtime::kThrow, context, value);
          break;
      }
      assembler->Return(result);
    }
  
    assembler->Bind(&if_receiverisrunning);
    {
      Node* result =
          assembler->CallRuntime(Runtime::kThrowGeneratorRunning, context);
      assembler->Return(result);  // Never reached.
    }
  }
  
  }  // anonymous namespace
  
  // ES6 section 25.3.1.2 Generator.prototype.next ( value )
  void Builtins::Generate_GeneratorPrototypeNext(
      compiler::CodeAssemblerState* state) {
    CodeStubAssembler assembler(state);
    Generate_GeneratorPrototypeResume(&assembler, JSGeneratorObject::kNext,
                                      "[Generator].prototype.next");
  }
  
  // ES6 section 25.3.1.3 Generator.prototype.return ( value )
  void Builtins::Generate_GeneratorPrototypeReturn(
      compiler::CodeAssemblerState* state) {
    CodeStubAssembler assembler(state);
    Generate_GeneratorPrototypeResume(&assembler, JSGeneratorObject::kReturn,
                                      "[Generator].prototype.return");
  }
  
  // ES6 section 25.3.1.4 Generator.prototype.throw ( exception )
  void Builtins::Generate_GeneratorPrototypeThrow(
      compiler::CodeAssemblerState* state) {
    CodeStubAssembler assembler(state);
    Generate_GeneratorPrototypeResume(&assembler, JSGeneratorObject::kThrow,
                                      "[Generator].prototype.throw");
  }
  
  }  // namespace internal
  }  // namespace v8
  