Leaving a generator via an exception causes it to close

src/x64/full-codegen-x64.cc

 // Copyright 2012 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/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
@@ skipping 2178 matching lines @@
     Expression *value,
     JSGeneratorObject::ResumeMode resume_mode) {
   // The value stays in rax, and is ultimately read by the resumed generator, as
   // if CallRuntime(Runtime::kSuspendJSGeneratorObject) returned it. Or it
   // is read to throw the value when the resumed generator is already closed.
   // rbx will hold the generator object until the activation has been resumed.
   VisitForStackValue(generator);
   VisitForAccumulatorValue(value);
   __ Pop(rbx);
 
-  // Check generator state.
-  Label wrong_state, closed_state, done;
-  STATIC_ASSERT(JSGeneratorObject::kGeneratorExecuting < 0);
-  STATIC_ASSERT(JSGeneratorObject::kGeneratorClosed == 0);
-  __ SmiCompare(FieldOperand(rbx, JSGeneratorObject::kContinuationOffset),
-                Smi::FromInt(0));
-  __ j(equal, &closed_state);
-  __ j(less, &wrong_state);
-
   // Load suspended function and context.
   __ movp(rsi, FieldOperand(rbx, JSGeneratorObject::kContextOffset));
   __ movp(rdi, FieldOperand(rbx, JSGeneratorObject::kFunctionOffset));
 
   // Push receiver.
   __ Push(FieldOperand(rbx, JSGeneratorObject::kReceiverOffset));
 
   // Push holes for arguments to generator function.
   __ movp(rdx, FieldOperand(rdi, JSFunction::kSharedFunctionInfoOffset));
   __ LoadSharedFunctionInfoSpecialField(rdx, rdx,
       SharedFunctionInfo::kFormalParameterCountOffset);
   __ LoadRoot(rcx, Heap::kTheHoleValueRootIndex);
   Label push_argument_holes, push_frame;
   __ bind(&push_argument_holes);
   __ subp(rdx, Immediate(1));
   __ j(carry, &push_frame);
   __ Push(rcx);
   __ jmp(&push_argument_holes);
 
   // Enter a new JavaScript frame, and initialize its slots as they were when
   // the generator was suspended.
-  Label resume_frame;
+  Label resume_frame, done;
   __ bind(&push_frame);
   __ call(&resume_frame);
   __ jmp(&done);
   __ bind(&resume_frame);
   __ pushq(rbp);  // Caller's frame pointer.
   __ movp(rbp, rsp);
   __ Push(rsi);  // Callee's context.
   __ Push(rdi);  // Callee's JS Function.
 
   // Load the operand stack size.
@@ skipping 26 matching lines @@
   __ Push(rcx);
   __ jmp(&push_operand_holes);
   __ bind(&call_resume);
   __ Push(rbx);
   __ Push(result_register());
   __ Push(Smi::FromInt(resume_mode));
   __ CallRuntime(Runtime::kResumeJSGeneratorObject, 3);
   // Not reached: the runtime call returns elsewhere.
   __ Abort(kGeneratorFailedToResume);
 
-  // Reach here when generator is closed.
-  __ bind(&closed_state);
-  if (resume_mode == JSGeneratorObject::NEXT) {
-    // Return completed iterator result when generator is closed.
-    __ PushRoot(Heap::kUndefinedValueRootIndex);
-    // Pop value from top-of-stack slot; box result into result register.
-    EmitCreateIteratorResult(true);
-  } else {
-    // Throw the provided value.
-    __ Push(rax);
-    __ CallRuntime(Runtime::kThrow, 1);
-  }
-  __ jmp(&done);
-
-  // Throw error if we attempt to operate on a running generator.
-  __ bind(&wrong_state);
-  __ Push(rbx);
-  __ CallRuntime(Runtime::kThrowGeneratorStateError, 1);
-
   __ bind(&done);
   context()->Plug(result_register());
 }
 
 
 void FullCodeGenerator::EmitCreateIteratorResult(bool done) {
   Label gc_required;
   Label allocated;
 
   const int instance_size = 5 * kPointerSize;
@@ skipping 2954 matching lines @@
   DCHECK_EQ(isolate->builtins()->OsrAfterStackCheck()->entry(),
             Assembler::target_address_at(call_target_address,
                                          unoptimized_code));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64