Replace HeapNumber as doublebox with an explicit MutableHeapNumber.

src/objects-debug.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 69 matching lines @@
   }
 
   switch (instance_type) {
     case SYMBOL_TYPE:
       Symbol::cast(this)->SymbolVerify();
       break;
     case MAP_TYPE:
       Map::cast(this)->MapVerify();
       break;
     case HEAP_NUMBER_TYPE:
+    case MUTABLE_HEAP_NUMBER_TYPE:
       HeapNumber::cast(this)->HeapNumberVerify();
       break;
     case FIXED_ARRAY_TYPE:
       FixedArray::cast(this)->FixedArrayVerify();
       break;
     case FIXED_DOUBLE_ARRAY_TYPE:
       FixedDoubleArray::cast(this)->FixedDoubleArrayVerify();
       break;
     case CONSTANT_POOL_ARRAY_TYPE:
       ConstantPoolArray::cast(this)->ConstantPoolArrayVerify();
@@ skipping 125 matching lines @@
 void Symbol::SymbolVerify() {
   CHECK(IsSymbol());
   CHECK(HasHashCode());
   CHECK_GT(Hash(), 0);
   CHECK(name()->IsUndefined() || name()->IsString());
   CHECK(flags()->IsSmi());
 }
 
 
 void HeapNumber::HeapNumberVerify() {
-  CHECK(IsHeapNumber());
+  CHECK(IsHeapNumber() || IsMutableHeapNumber());
 }
 
 
 void ByteArray::ByteArrayVerify() {
   CHECK(IsByteArray());
 }
 
 
 void FreeSpace::FreeSpaceVerify() {
   CHECK(IsFreeSpace());
@@ skipping 37 matching lines @@
   if (HasFastProperties()) {
     CHECK_EQ(map()->unused_property_fields(),
              (map()->inobject_properties() + properties()->length() -
               map()->NextFreePropertyIndex()));
     DescriptorArray* descriptors = map()->instance_descriptors();
     for (int i = 0; i < map()->NumberOfOwnDescriptors(); i++) {
       if (descriptors->GetDetails(i).type() == FIELD) {
         Representation r = descriptors->GetDetails(i).representation();
         int field = descriptors->GetFieldIndex(i);
         Object* value = RawFastPropertyAt(field);
-        if (r.IsDouble()) ASSERT(value->IsHeapNumber());
+        if (r.IsDouble()) ASSERT(value->IsMutableHeapNumber());
         if (value->IsUninitialized()) continue;
         if (r.IsSmi()) ASSERT(value->IsSmi());
         if (r.IsHeapObject()) ASSERT(value->IsHeapObject());
       }
     }
   }
 
   // If a GC was caused while constructing this object, the elements
   // pointer may point to a one pointer filler map.
   if (ElementsAreSafeToExamine()) {
@@ skipping 853 matching lines @@
   for (int i = 0; i < number_of_transitions(); ++i) {
     if (!CheckOneBackPointer(current_map, GetTarget(i))) return false;
   }
   return true;
 }
 
 
 #endif  // DEBUG
 
 } }  // namespace v8::internal