Changeset 87838 in webkit for trunk/Source/JavaScriptCore/parser/ParserArena.h

Timestamp:

Jun 1, 2011, 1:09:04 PM (14 years ago)

Author:

[email protected]

Message:

2011-06-01 Oliver Hunt <​[email protected]>

Reviewed by Geoffrey Garen.

Add single character lookup cache to IdentifierArena
​https://bugs.webkit.org/show_bug.cgi?id=61879

Add a simple lookup cache for single ascii character
identifiers. Produces around a 2% improvement in parse
time for my adhoc parser test.

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

File:

• trunk/Source/JavaScriptCore/parser/ParserArena.h (modified) (1 diff)

trunk/Source/JavaScriptCore/parser/ParserArena.h

@@ -38 +38 @@
         WTF_MAKE_FAST_ALLOCATED;
     public:
+        IdentifierArena()
+        {
+            clear();
+        }
+
         ALWAYS_INLINE const Identifier& makeIdentifier(JSGlobalData*, const UChar* characters, size_t length);
         const Identifier& makeNumericIdentifier(JSGlobalData*, double number);
 
-        void clear() { m_identifiers.clear(); }
+        void clear()
+        {
+            m_identifiers.clear();
+            for (unsigned  i = 0; i < 128; i++)
+                m_shortIdentifiers[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;
     };
 
     ALWAYS_INLINE const Identifier& IdentifierArena::makeIdentifier(JSGlobalData* globalData, const UChar* characters, size_t length)
     {
+        if (length == 1 && characters[0] < MaximumCachableCharacter) {
+            if (Identifier* ident = m_shortIdentifiers[characters[0]])
+                return *ident;
+            m_identifiers.append(Identifier(globalData, characters, length));
+            m_shortIdentifiers[characters[0]] = &m_identifiers.last();
+            return m_identifiers.last();
+        }
         m_identifiers.append(Identifier(globalData, characters, length));
         return m_identifiers.last();