Calling a generator function returns a generator object

src/x64/full-codegen-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
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@@ skipping 266 matching lines @@
     { Comment cmnt(masm_, "[ Stack check");
       PrepareForBailoutForId(BailoutId::Declarations(), NO_REGISTERS);
       Label ok;
       __ CompareRoot(rsp, Heap::kStackLimitRootIndex);
       __ j(above_equal, &ok, Label::kNear);
       StackCheckStub stub;
       __ CallStub(&stub);
       __ bind(&ok);
     }
 
+    if (function()->is_generator()) {

[wingo, 2013/04/03 16:36:24]

How to communicate this iterator object from its allocation to the "yield" call
sites?  I think the answer is to use a local variable.

Instead of fabricating a runtime call here, I think we probably need to add some
nodes to the AST to CallRuntime(CreateJSGeneratorIterator), store it in a
variable, and record that variable in the FunctionState; and follow it with a
runtime call to SuspendGenerator in the prologue, passing the saved generator
iterator as a param.

With forced context allocation, an added local would get put in the context
object, leading to the silliness where the context has a pointer to the iterator
and vice versa.  Oh well; probably something we can live with.

+      Comment cmnt(masm_, "[ Generator Iterator");
+      __ push(Operand(rbp, JavaScriptFrameConstants::kFunctionOffset));
+      __ CallRuntime(Runtime::kCreateJSGeneratorIterator, 1);
+      // TODO(wingo): Suspend the generator.
+      EmitReturnSequence();
+    }
+
     { Comment cmnt(masm_, "[ Body");
       ASSERT(loop_depth() == 0);
       VisitStatements(function()->body());
       ASSERT(loop_depth() == 0);
     }
   }
 
   // Always emit a 'return undefined' in case control fell off the end of
   // the body.
   { Comment cmnt(masm_, "[ return <undefined>;");
@@ skipping 4257 matching lines @@
   *context_length = 0;
   return previous_;
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64