[generators] Create the fixed array holding the registers only once.

src/runtime/runtime-generator.cc

 // Copyright 2014 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/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/factory.h"
 #include "src/frames-inl.h"
 #include "src/objects-inl.h"
 
 namespace v8 {
 namespace internal {
 
 RUNTIME_FUNCTION(Runtime_CreateJSGeneratorObject) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 2);
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
   CONVERT_ARG_HANDLE_CHECKED(Object, receiver, 1);
   RUNTIME_ASSERT(function->shared()->is_generator());
 
+  Handle<FixedArray> operand_stack;
+  if (FLAG_ignition && FLAG_ignition_generators) {
+    int size = function->shared()->bytecode_array()->register_count();
+    operand_stack = isolate->factory()->NewFixedArray(size);
+  } else {
+    DCHECK(!function->shared()->HasBytecodeArray());
+    operand_stack = handle(isolate->heap()->empty_fixed_array());
+  }
+
   Handle<JSGeneratorObject> generator =
       isolate->factory()->NewJSGeneratorObject(function);
   generator->set_function(*function);
   generator->set_context(isolate->context());
   generator->set_receiver(*receiver);
-  generator->set_operand_stack(isolate->heap()->empty_fixed_array());
+  generator->set_operand_stack(*operand_stack);
   generator->set_continuation(JSGeneratorObject::kGeneratorExecuting);
   return *generator;
 }
 
 
 RUNTIME_FUNCTION(Runtime_SuspendJSGeneratorObject) {
   HandleScope handle_scope(isolate);
   DCHECK(args.length() == 1);
   CONVERT_ARG_HANDLE_CHECKED(JSGeneratorObject, generator_object, 0);
 
@@ skipping 102 matching lines @@
     int offset = generator->continuation();
     RUNTIME_ASSERT(0 <= offset && offset < code->instruction_size());
     return Smi::FromInt(code->SourcePosition(offset));
   }
 
   return isolate->heap()->undefined_value();
 }
 
 }  // namespace internal
 }  // namespace v8