Changeset 169316 in webkit for trunk/Source/JavaScriptCore/runtime/SmallStrings.h

Timestamp:

May 24, 2014, 8:50:43 PM (11 years ago)

Author:

[email protected]

Message:

Object.prototype.toString() should use cached strings for null/undefined.
<​https://webkit.org/b/133261>

Normally, when calling Object.prototype.toString() on a regular object,
we'd cache the result of the stringification on the object's structure,
making repeated calls fast.

For null and undefined, we were not as smart. We'd instead construct a
new string with either "[object Null]" or "[object Undefined]" each time.

This was exposed by Dromaeo's JS library tests, where some prototype.js
subtests generate millions of strings this way.

This patch adds two VM-permanent cached strings to the SmallStrings.
Looks like ~10% speed-up on Dromaeo/jslib-traverse-prototype.html

Reviewed by Darin Adler.

• runtime/ObjectPrototype.cpp:

(JSC::objectProtoFuncToString):

• runtime/SmallStrings.cpp:

(JSC::SmallStrings::SmallStrings):
(JSC::SmallStrings::initializeCommonStrings):
(JSC::SmallStrings::visitStrongReferences):

• runtime/SmallStrings.h:

(JSC::SmallStrings::nullObjectString):
(JSC::SmallStrings::undefinedObjectString):

File:

• trunk/Source/JavaScriptCore/runtime/SmallStrings.h (modified) (2 diffs)

trunk/Source/JavaScriptCore/runtime/SmallStrings.h

@@ -87 +87 @@
 #undef JSC_COMMON_STRINGS_ACCESSOR_DEFINITION
 
+        JSString* nullObjectString() const { return m_nullObjectString; }
+        JSString* undefinedObjectString() const { return m_undefinedObjectString; }
+
     private:
         static const unsigned singleCharacterStringCount = maxSingleCharacterString + 1;
@@ -99 +102 @@
         JSC_COMMON_STRINGS_EACH_NAME(JSC_COMMON_STRINGS_ATTRIBUTE_DECLARATION)
 #undef JSC_COMMON_STRINGS_ATTRIBUTE_DECLARATION
+        JSString* m_nullObjectString;
+        JSString* m_undefinedObjectString;
         JSString* m_singleCharacterStrings[singleCharacterStringCount];
         OwnPtr<SmallStringsStorage> m_storage;