Reviewers: Erik Corry,
Description:
Use the number of in-object properties when deciding how many fast
properties to allow on an object. If there are many in-object
properties it is unlikely that the object is used as a dictionary and
we allow more map transitions to keep such objects in fast case.
Please review this at http://codereview.chromium.org/2818041/show
SVN Base: http://v8.googlecode.com/svn/branches/bleeding_edge/
Affected files:
M src/objects-inl.h
M src/objects.h
M src/objects.cc
Index: src/objects-inl.h
===================================================================
--- src/objects-inl.h (revision 5007)
+++ src/objects-inl.h (working copy)
@@ -1335,6 +1335,21 @@
}
+bool JSObject::HasFastProperties() {
+ return !properties()->IsDictionary();
+}
+
+
+int JSObject::MaxFastProperties() {
+ // Allow extra fast properties if the object has more than
+ // kMaxFastProperties in-object properties. When this is the case,
+ // it is very unlikely that the object is being used as a dictionary
+ // and there is a good chance that allowing more map transitions
+ // will be worth it.
+ return Max(map()->inobject_properties(), kMaxFastProperties);
+}
+
+
void Struct::InitializeBody(int object_size) {
Object* value = Heap::undefined_value();
for (int offset = kHeaderSize; offset < object_size; offset +=
kPointerSize) {
@@ -1343,11 +1358,6 @@
}
-bool JSObject::HasFastProperties() {
- return !properties()->IsDictionary();
-}
-
-
bool Object::ToArrayIndex(uint32_t* index) {
if (IsSmi()) {
int value = Smi::cast(this)->value();
Index: src/objects.cc
===================================================================
--- src/objects.cc (revision 5007)
+++ src/objects.cc (working copy)
@@ -1276,7 +1276,7 @@
}
if (map()->unused_property_fields() == 0) {
- if (properties()->length() > kMaxFastProperties) {
+ if (properties()->length() > MaxFastProperties()) {
Object* obj = NormalizeProperties(CLEAR_INOBJECT_PROPERTIES, 0);
if (obj->IsFailure()) return obj;
return AddSlowProperty(name, value, attributes);
@@ -1474,7 +1474,7 @@
Object* new_value,
PropertyAttributes attributes) {
if (map()->unused_property_fields() == 0 &&
- properties()->length() > kMaxFastProperties) {
+ properties()->length() > MaxFastProperties()) {
Object* obj = NormalizeProperties(CLEAR_INOBJECT_PROPERTIES, 0);
if (obj->IsFailure()) return obj;
return ReplaceSlowProperty(name, new_value, attributes);
Index: src/objects.h
===================================================================
--- src/objects.h (revision 5007)
+++ src/objects.h (working copy)
@@ -1367,6 +1367,7 @@
// Returns the index'th element.
// The undefined object if index is out of bounds.
Object* GetElementWithReceiver(JSObject* receiver, uint32_t index);
+ Object* GetElementWithInterceptor(JSObject* receiver, uint32_t index);
Object* SetFastElementsCapacityAndLength(int capacity, int length);
Object* SetSlowElements(Object* length);
@@ -1547,6 +1548,11 @@
#endif
Object* SlowReverseLookup(Object* value);
+ // Maximal number of fast properties for the JSObject. Used to
+ // restrict the number of map transitions to avoid an explosion in
+ // the number of maps for objects used as dictionaries.
+ inline int MaxFastProperties();
+
// Maximal number of elements (numbered 0 .. kMaxElementCount - 1).
// Also maximal value of JSArray's length property.
static const uint32_t kMaxElementCount = 0xffffffffu;
@@ -1568,8 +1574,6 @@
STATIC_CHECK(kHeaderSize == Internals::kJSObjectHeaderSize);
- Object* GetElementWithInterceptor(JSObject* receiver, uint32_t index);
-
private:
Object* GetElementWithCallback(Object* receiver,
Object* structure,
--
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