Changeset 37627 in webkit for trunk/JavaScriptCore

Timestamp:

Oct 15, 2008, 9:36:12 PM (17 years ago)

Author:

[email protected]

Message:

2008-10-15 Cameron Zwarich <​[email protected]>

Reviewed by Maciej Stachowiak.

Bug 21633: Avoid using a HashMap when there is only a single transition
<​https://bugs.webkit.org/show_bug.cgi?id=21633>

This is a 0.8% speedup on SunSpider and between a 0.5% and 1.0% speedup
on the V8 benchmark suite, depending on which harness we use. It will
also slightly reduce the memory footprint of a StructureID.

• kjs/StructureID.cpp: (JSC::StructureID::StructureID): (JSC::StructureID::~StructureID): (JSC::StructureID::addPropertyTransition):
• kjs/StructureID.h: (JSC::StructureID::):

Location:

trunk/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• kjs/StructureID.cpp (modified) (5 diffs)
• kjs/StructureID.h (modified) (1 diff)

trunk/JavaScriptCore/ChangeLog

@@ +1 @@
+2008-10-15  Cameron Zwarich  <[email protected]>
+
+        Reviewed by Maciej Stachowiak.
+
+        Bug 21633: Avoid using a HashMap when there is only a single transition
+        <https://bugs.webkit.org/show_bug.cgi?id=21633>
+
+        This is a 0.8% speedup on SunSpider and between a 0.5% and 1.0% speedup
+        on the V8 benchmark suite, depending on which harness we use. It will
+        also slightly reduce the memory footprint of a StructureID.
+
+        * kjs/StructureID.cpp:
+        (JSC::StructureID::StructureID):
+        (JSC::StructureID::~StructureID):
+        (JSC::StructureID::addPropertyTransition):
+        * kjs/StructureID.h:
+        (JSC::StructureID::):
+
 2008-10-15  Csaba Osztrogonac  <[email protected]>
 

trunk/JavaScriptCore/kjs/StructureID.cpp

@@ -54 +54 @@
     , m_nameInPrevious(0)
     , m_transitionCount(0)
+    , m_usingSingleTransitionSlot(true)
     , m_propertyStorageCapacity(JSObject::inlineStorageCapacity)
     , m_cachedTransistionOffset(WTF::notFound)
@@ -59 +60 @@
     ASSERT(m_prototype);
     ASSERT(m_prototype->isObject() || m_prototype->isNull());
+
+    m_transitions.singleTransition = 0;
 
 #ifndef NDEBUG
@@ -71 +74 @@
 {
     if (m_previous) {
-        ASSERT(m_previous->m_transitionTable.contains(make_pair(m_nameInPrevious, m_attributesInPrevious)));
-        m_previous->m_transitionTable.remove(make_pair(m_nameInPrevious, m_attributesInPrevious));
+        if (m_previous->m_usingSingleTransitionSlot) {
+            m_previous->m_transitions.singleTransition->deref();
+            m_previous->m_transitions.singleTransition = 0;
+        } else {
+            ASSERT(m_previous->m_transitions.table->contains(make_pair(m_nameInPrevious, m_attributesInPrevious)));
+            m_previous->m_transitions.table->remove(make_pair(m_nameInPrevious, m_attributesInPrevious));
+        }
     }
 
     if (m_cachedPropertyNameArrayData)
         m_cachedPropertyNameArrayData->setCachedStructureID(0);
+
+    if (m_usingSingleTransitionSlot) {
+        if (m_transitions.singleTransition)
+            m_transitions.singleTransition->deref();
+    } else
+        delete m_transitions.table;
 
 #ifndef NDEBUG
@@ -169 +183 @@
     ASSERT(structureID->typeInfo().type() == ObjectType);
 
-    if (StructureID* existingTransition = structureID->m_transitionTable.get(make_pair(propertyName.ustring().rep(), attributes))) {
-        offset = existingTransition->cachedTransistionOffset();
-        ASSERT(offset != WTF::notFound);
-        return existingTransition;
+    if (structureID->m_usingSingleTransitionSlot) {
+        StructureID* existingTransition = structureID->m_transitions.singleTransition;
+        if (existingTransition && existingTransition->m_nameInPrevious == propertyName.ustring().rep() && existingTransition->m_attributesInPrevious == attributes) {
+            offset = structureID->m_transitions.singleTransition->cachedTransistionOffset();
+            ASSERT(offset != WTF::notFound);
+            return existingTransition;
+        }
+    } else {
+        if (StructureID* existingTransition = structureID->m_transitions.table->get(make_pair(propertyName.ustring().rep(), attributes))) {
+            offset = existingTransition->cachedTransistionOffset();
+            ASSERT(offset != WTF::notFound);
+            return existingTransition;
+        }        
     }
 
@@ -199 +222 @@
     transition->setCachedTransistionOffset(offset);
 
-    structureID->m_transitionTable.add(make_pair(propertyName.ustring().rep(), attributes), transition.get());
+    if (structureID->m_usingSingleTransitionSlot) {
+        if (!structureID->m_transitions.singleTransition) {
+            structureID->m_transitions.singleTransition = transition.get();
+            transition->ref();
+            return transition.release();
+        }
+
+        StructureID* existingTransition = structureID->m_transitions.singleTransition;
+        structureID->m_usingSingleTransitionSlot = false;
+        TransitionTable* transitionTable = new TransitionTable;
+        structureID->m_transitions.table = transitionTable;
+        transitionTable->add(make_pair(existingTransition->m_nameInPrevious, existingTransition->m_attributesInPrevious), existingTransition);
+        existingTransition->deref();
+    }
+    structureID->m_transitions.table->add(make_pair(propertyName.ustring().rep(), attributes), transition.get());
     return transition.release();
 }

trunk/JavaScriptCore/kjs/StructureID.h

@@ -153 +153 @@
 
         size_t m_transitionCount;
-        TransitionTable m_transitionTable;
+        bool m_usingSingleTransitionSlot;
+        union {
+            StructureID* singleTransition;
+            TransitionTable* table;
+        } m_transitions;
 
         RefPtr<PropertyNameArrayData> m_cachedPropertyNameArrayData;