Fix LoadFieldByIndex to take mutable heap-numbers into account.

src/runtime.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 14529 matching lines @@
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_NotifyContextDisposed) {
   HandleScope scope(isolate);
   ASSERT(args.length() == 0);
   isolate->heap()->NotifyContextDisposed();
   return isolate->heap()->undefined_value();
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_LoadMutableDouble) {
+  HandleScope scope(isolate);
+  ASSERT(args.length() == 2);
+  CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
+  CONVERT_ARG_HANDLE_CHECKED(Smi, index, 1);
+  int idx = index->value() >> 1;
+  if (idx < 0) {
+    idx = -idx + object->map()->inobject_properties() - 1;
+  }
+  return *JSObject::FastPropertyAt(object, Representation::Double(), idx);
+}
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_TryMigrateInstance) {
   HandleScope scope(isolate);
   ASSERT(args.length() == 1);
   CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
   if (!object->IsJSObject()) return Smi::FromInt(0);
   Handle<JSObject> js_object = Handle<JSObject>::cast(object);
   if (!js_object->map()->is_deprecated()) return Smi::FromInt(0);
   // This call must not cause lazy deopts, because it's called from deferred
   // code where we can't handle lazy deopts for lack of a suitable bailout
   // ID. So we just try migration and signal failure if necessary,
@@ skipping 609 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal