Bug 1358504 - Add a 1-entry cache to ObjectGroup::defaultNewGroup. r=bhackett

js/src/jscompartment.cpp

@@ -1047,6 +1047,7 @@ JSCompartment::purge()
     dtoaCache.purge();
     newProxyCache.purge();
     lastCachedNativeIterator = nullptr;
+    objectGroups.purge();
 }
 
 void

js/src/vm/ObjectGroup.cpp

@@ -461,6 +461,20 @@ class ObjectGroupCompartment::NewTable : public JS::WeakCache<js::GCHashSet<NewE
     explicit NewTable(Zone* zone) : Base(zone, Table()) {}
 };
 
+MOZ_ALWAYS_INLINE ObjectGroup*
+ObjectGroupCompartment::DefaultNewGroupCache::lookup(const Class* clasp, TaggedProto proto,
+                                                     JSObject* associated)
+{
+    if (group_ &&
+        associated_ == associated &&
+        group_->proto() == proto &&
+        (!clasp || group_->clasp() == clasp))
+    {
+        return group_;
+    }
+    return nullptr;
+}
+
 /* static */ ObjectGroup*
 ObjectGroup::defaultNewGroup(JSContext* cx, const Class* clasp,
                              TaggedProto proto, JSObject* associated)
@@ -473,20 +487,6 @@ ObjectGroup::defaultNewGroup(JSContext* cx, const Class* clasp,
     // unboxed plain object.
     MOZ_ASSERT_IF(!clasp, !!associated);
 
-    AutoEnterAnalysis enter(cx);
-
-    ObjectGroupCompartment::NewTable*& table = cx->compartment()->objectGroups.defaultNewTable;
-
-    if (!table) {
-        table = cx->new_<ObjectGroupCompartment::NewTable>(cx->zone());
-        if (!table || !table->init()) {
-            js_delete(table);
-            table = nullptr;
-            ReportOutOfMemory(cx);
-            return nullptr;
-        }
-    }
-
     if (associated && !associated->is<TypeDescr>()) {
         MOZ_ASSERT(!clasp);
         if (associated->is<JSFunction>()) {
@@ -513,6 +513,25 @@ ObjectGroup::defaultNewGroup(JSContext* cx, const Class* clasp,
             clasp = &PlainObject::class_;
     }
 
+    ObjectGroupCompartment& groups = cx->compartment()->objectGroups;
+
+    if (ObjectGroup* group = groups.defaultNewGroupCache.lookup(clasp, proto, associated))
+        return group;
+
+    AutoEnterAnalysis enter(cx);
+
+    ObjectGroupCompartment::NewTable*& table = groups.defaultNewTable;
+
+    if (!table) {
+        table = cx->new_<ObjectGroupCompartment::NewTable>(cx->zone());
+        if (!table || !table->init()) {
+            js_delete(table);
+            table = nullptr;
+            ReportOutOfMemory(cx);
+            return nullptr;
+        }
+    }
+
     if (proto.isObject() && !proto.toObject()->isDelegate()) {
         RootedObject protoObj(cx, proto.toObject());
         if (!JSObject::setDelegate(cx, protoObj))
@@ -536,6 +555,7 @@ ObjectGroup::defaultNewGroup(JSContext* cx, const Class* clasp,
         MOZ_ASSERT_IF(!clasp, group->clasp() == &PlainObject::class_ ||
                               group->clasp() == &UnboxedPlainObject::class_);
         MOZ_ASSERT(group->proto() == proto);
+        groups.defaultNewGroupCache.put(group, associated);
         return group;
     }
 
@@ -582,6 +602,7 @@ ObjectGroup::defaultNewGroup(JSContext* cx, const Class* clasp,
         AddTypePropertyId(cx, group, nullptr, NameToId(names.columnNumber), TypeSet::Int32Type());
     }
 
+    groups.defaultNewGroupCache.put(group, associated);
     return group;
 }
 
@@ -1681,6 +1702,7 @@ ObjectGroupCompartment::removeDefaultNewGroup(const Class* clasp, TaggedProto pr
     MOZ_RELEASE_ASSERT(p);
 
     defaultNewTable->get().remove(p);
+    defaultNewGroupCache.purge();
 }
 
 void
@@ -1692,6 +1714,7 @@ ObjectGroupCompartment::replaceDefaultNewGroup(const Class* clasp, TaggedProto p
     auto p = defaultNewTable->lookup(lookup);
     MOZ_RELEASE_ASSERT(p);
     defaultNewTable->get().remove(p);
+    defaultNewGroupCache.purge();
     {
         AutoEnterOOMUnsafeRegion oomUnsafe;
         if (!defaultNewTable->putNew(lookup, NewEntry(group, associated)))
@@ -1770,6 +1793,7 @@ ObjectGroupCompartment::clearTables()
         defaultNewTable->clear();
     if (lazyTable && lazyTable->initialized())
         lazyTable->clear();
+    defaultNewGroupCache.purge();
 }
 
 /* static */ bool

js/src/vm/ObjectGroup.h

@@ -566,6 +566,28 @@ class ObjectGroupCompartment
     NewTable* defaultNewTable;
     NewTable* lazyTable;
 
+    // Cache for defaultNewGroup. Purged on GC.
+    class DefaultNewGroupCache
+    {
+        ObjectGroup* group_;
+        JSObject* associated_;
+
+      public:
+        DefaultNewGroupCache() { purge(); }
+
+        void purge() {
+            group_ = nullptr;
+        }
+        void put(ObjectGroup* group, JSObject* associated) {
+            group_ = group;
+            associated_ = associated;
+        }
+
+        MOZ_ALWAYS_INLINE ObjectGroup* lookup(const Class* clasp, TaggedProto proto,
+                                              JSObject* associated);
+    };
+    DefaultNewGroupCache defaultNewGroupCache;
+
     struct ArrayObjectKey;
     using ArrayObjectTable = js::GCRekeyableHashMap<ArrayObjectKey,
                                                     ReadBarrieredObjectGroup,
@@ -628,6 +650,10 @@ class ObjectGroupCompartment
 
     void sweep(FreeOp* fop);
 
+    void purge() {
+        defaultNewGroupCache.purge();
+    }
+
 #ifdef JSGC_HASH_TABLE_CHECKS
     void checkTablesAfterMovingGC() {
         checkNewTableAfterMovingGC(defaultNewTable);