Changeset 88394 in webkit for trunk/Source/JavaScriptCore/parser/ParserArena.h

Timestamp:

Jun 8, 2011, 2:54:15 PM (14 years ago)

Author:

[email protected]

Message:

2011-06-08 Oliver Hunt <​[email protected]>

Reviewed by Geoffrey Garen.

Add faster lookup cache for multi character identifiers
​https://bugs.webkit.org/show_bug.cgi?id=62327

Add a non-hash lookup for mutiple character identifiers. This saves us from
adding repeated identifiers to the ParserArena's identifier list as people
tend to not start all their variables and properties with the same character
and happily identifier locality works in our favour.

• parser/ParserArena.h: (JSC::IdentifierArena::isEmpty): (JSC::IdentifierArena::clear): (JSC::IdentifierArena::makeIdentifier):

File:

• trunk/Source/JavaScriptCore/parser/ParserArena.h (modified) (2 diffs)

trunk/Source/JavaScriptCore/parser/ParserArena.h

@@ -46 +46 @@
         const Identifier& makeNumericIdentifier(JSGlobalData*, double number);
 
+        bool isEmpty() const { return m_identifiers.isEmpty(); }
+
+    public:
+        static const int MaximumCachableCharacter = 128;
+        typedef SegmentedVector<Identifier, 64> IdentifierVector;
         void clear()
         {
             m_identifiers.clear();
-            for (unsigned  i = 0; i < 128; i++)
+            for (int i = 0; i < MaximumCachableCharacter; i++)
                 m_shortIdentifiers[i] = 0;
+            for (int i = 0; i < MaximumCachableCharacter; i++)
+                m_recentIdentifiers[i] = 0;
         }
-        bool isEmpty() const { return m_identifiers.isEmpty(); }
 
     private:
-        static const int MaximumCachableCharacter = 128;
-        typedef SegmentedVector<Identifier, 64> IdentifierVector;
         IdentifierVector m_identifiers;
         FixedArray<Identifier*, MaximumCachableCharacter> m_shortIdentifiers;
+        FixedArray<Identifier*, MaximumCachableCharacter> m_recentIdentifiers;
     };
 
     ALWAYS_INLINE const Identifier& IdentifierArena::makeIdentifier(JSGlobalData* globalData, const UChar* characters, size_t length)
     {
-        if (length == 1 && characters[0] < MaximumCachableCharacter) {
+        if (characters[0] >= MaximumCachableCharacter) {
+            m_identifiers.append(Identifier(globalData, characters, length));
+            return m_identifiers.last();
+        }
+        if (length == 1) {
             if (Identifier* ident = m_shortIdentifiers[characters[0]])
                 return *ident;
@@ -70 +79 @@
             return m_identifiers.last();
         }
+        Identifier* ident = m_recentIdentifiers[characters[0]];
+        if (ident && Identifier::equal(ident->impl(), characters, length))
+            return *ident;
         m_identifiers.append(Identifier(globalData, characters, length));
+        m_recentIdentifiers[characters[0]] = &m_identifiers.last();
         return m_identifiers.last();
     }