[turbofan] Simplify graph construction for for-in.

src/runtime/runtime-array.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/v8.h"
 
 #include "src/arguments.h"
 #include "src/messages.h"
 #include "src/runtime/runtime-utils.h"
 
@@ skipping 1300 matching lines @@
   // This simulates CONVERT_ARG_HANDLE_CHECKED for calls returning pairs.
   // Not worth creating a macro atm as this function should be removed.
   if (!args[0]->IsJSReceiver() || !args[1]->IsObject()) {
     Object* error = isolate->ThrowIllegalOperation();
     return MakePair(error, isolate->heap()->undefined_value());
   }
   Handle<JSReceiver> object = args.at<JSReceiver>(0);
   Handle<Object> cache_type = args.at<Object>(1);
   if (cache_type->IsMap()) {
     // Enum cache case.
-    if (Map::EnumLengthBits::decode(Map::cast(*cache_type)->bit_field3()) ==
-        0) {
-      // 0 length enum.
-      // Can't handle this case in the graph builder,
-      // so transform it into the empty fixed array case.
-      return MakePair(isolate->heap()->empty_fixed_array(), Smi::FromInt(1));
-    }
-    return MakePair(object->map()->instance_descriptors()->GetEnumCache(),
+    return MakePair(Map::cast(*cache_type)->EnumLength() != 0
+                        ? object->map()->instance_descriptors()->GetEnumCache()
+                        : isolate->heap()->empty_fixed_array(),
                     *cache_type);
   } else {
     // FixedArray case.
     Smi* new_cache_type = Smi::FromInt(object->IsJSProxy() ? 0 : 1);
     return MakePair(*Handle<FixedArray>::cast(cache_type), new_cache_type);
   }
 }
 
 
 // TODO(dcarney): remove this function when TurboFan supports it.
@@ skipping 74 matching lines @@
 
 RUNTIME_FUNCTION(Runtime_FastOneByteArrayJoin) {
   SealHandleScope shs(isolate);
   DCHECK(args.length() == 2);
   // Returning undefined means that this fast path fails and one has to resort
   // to a slow path.
   return isolate->heap()->undefined_value();
 }
 }  // namespace internal
 }  // namespace v8