Reland r22082 "Replace HeapNumber as doublebox with an explicit MutableHeapNumber."

src/objects-inl.h

 // Copyright 2012 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.
 //
 // Review notes:
 //
 // - The use of macros in these inline functions may seem superfluous
 // but it is absolutely needed to make sure gcc generates optimal
 // code. gcc is not happy when attempting to inline too deep.
 //
@@ skipping 147 matching lines @@
   return HAS_SMI_TAG(this);
 }
 
 
 bool Object::IsHeapObject() const {
   return Internals::HasHeapObjectTag(this);
 }
 
 
 TYPE_CHECKER(HeapNumber, HEAP_NUMBER_TYPE)
+TYPE_CHECKER(MutableHeapNumber, MUTABLE_HEAP_NUMBER_TYPE)
 TYPE_CHECKER(Symbol, SYMBOL_TYPE)
 
 
 bool Object::IsString() const {
   return Object::IsHeapObject()
     && HeapObject::cast(this)->map()->instance_type() < FIRST_NONSTRING_TYPE;
 }
 
 
 bool Object::IsName() const {
@@ skipping 92 matching lines @@
 }
 
 
 Handle<Object> Object::NewStorageFor(Isolate* isolate,
                                      Handle<Object> object,
                                      Representation representation) {
   if (representation.IsSmi() && object->IsUninitialized()) {
     return handle(Smi::FromInt(0), isolate);
   }
   if (!representation.IsDouble()) return object;
+  double value;
   if (object->IsUninitialized()) {
-    return isolate->factory()->NewHeapNumber(0);
+    value = 0;
+  } else if (object->IsMutableHeapNumber()) {
+    value = HeapNumber::cast(*object)->value();
+  } else {
+    value = object->Number();
   }
-  return isolate->factory()->NewHeapNumber(object->Number());
+  return isolate->factory()->NewHeapNumber(value, MUTABLE);
 }
 
 
+Handle<Object> Object::WrapForRead(Isolate* isolate,
+                                   Handle<Object> object,
+                                   Representation representation) {
+  ASSERT(!object->IsUninitialized());
+  if (!representation.IsDouble()) {
+    ASSERT(object->FitsRepresentation(representation));
+    return object;
+  }
+  return isolate->factory()->NewHeapNumber(HeapNumber::cast(*object)->value());
+}
+
+
 StringShape::StringShape(const String* str)
   : type_(str->map()->instance_type()) {
   set_valid();
   ASSERT((type_ & kIsNotStringMask) == kStringTag);
 }
 
 
 StringShape::StringShape(Map* map)
   : type_(map->instance_type()) {
   set_valid();
@@ skipping 2775 matching lines @@
 CAST_ACCESSOR(ExternalUint32Array)
 CAST_ACCESSOR(ExternalUint8Array)
 CAST_ACCESSOR(ExternalUint8ClampedArray)
 CAST_ACCESSOR(FixedArray)
 CAST_ACCESSOR(FixedArrayBase)
 CAST_ACCESSOR(FixedDoubleArray)
 CAST_ACCESSOR(FixedTypedArrayBase)
 CAST_ACCESSOR(Foreign)
 CAST_ACCESSOR(FreeSpace)
 CAST_ACCESSOR(GlobalObject)
-CAST_ACCESSOR(HeapNumber)
 CAST_ACCESSOR(HeapObject)
 CAST_ACCESSOR(JSArray)
 CAST_ACCESSOR(JSArrayBuffer)
 CAST_ACCESSOR(JSArrayBufferView)
 CAST_ACCESSOR(JSBuiltinsObject)
 CAST_ACCESSOR(JSDataView)
 CAST_ACCESSOR(JSDate)
 CAST_ACCESSOR(JSFunction)
 CAST_ACCESSOR(JSFunctionProxy)
 CAST_ACCESSOR(JSFunctionResultCache)
@@ skipping 2844 matching lines @@
   return continuation() == kGeneratorExecuting;
 }
 
 ACCESSORS(JSModule, context, Object, kContextOffset)
 ACCESSORS(JSModule, scope_info, ScopeInfo, kScopeInfoOffset)
 
 
 ACCESSORS(JSValue, value, Object, kValueOffset)
 
 
+HeapNumber* HeapNumber::cast(Object* object) {
+  SLOW_ASSERT(object->IsHeapNumber() || object->IsMutableHeapNumber());
+  return reinterpret_cast<HeapNumber*>(object);
+}
+
+
+const HeapNumber* HeapNumber::cast(const Object* object) {
+  SLOW_ASSERT(object->IsHeapNumber() || object->IsMutableHeapNumber());
+  return reinterpret_cast<const HeapNumber*>(object);
+}
+
+
 ACCESSORS(JSDate, value, Object, kValueOffset)
 ACCESSORS(JSDate, cache_stamp, Object, kCacheStampOffset)
 ACCESSORS(JSDate, year, Object, kYearOffset)
 ACCESSORS(JSDate, month, Object, kMonthOffset)
 ACCESSORS(JSDate, day, Object, kDayOffset)
 ACCESSORS(JSDate, weekday, Object, kWeekdayOffset)
 ACCESSORS(JSDate, hour, Object, kHourOffset)
 ACCESSORS(JSDate, min, Object, kMinOffset)
 ACCESSORS(JSDate, sec, Object, kSecOffset)
 
@@ skipping 1065 matching lines @@
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 #undef NOBARRIER_READ_BYTE_FIELD
 #undef NOBARRIER_WRITE_BYTE_FIELD
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_