Changeset 63268 in webkit for trunk/JavaScriptCore/runtime/JSArray.h

Timestamp:

Jul 13, 2010, 5:29:32 PM (15 years ago)

Author:

[email protected]

Message:

2010-07-13 Andreas Kling <​[email protected]>

Reviewed by Darin Adler.

Avoid slow-path for put() in Array.splice()
​https://bugs.webkit.org/show_bug.cgi?id=41920

Defer creation of the returned array until its final size is known
to avoid growing it while adding elements.

• runtime/JSArray.cpp: (JSC::JSArray::JSArray): Add two modes of creation, CreateInitialized (old) and CreateCompact (which should only be used when constructing arrays whose size and contents are known at the time of creation.) (JSC::JSArray::setLength): Skip first consistency check if in CreateCompact initialization mode. (Only applies to non-empty arrays.) (JSC::JSArray::checkConsistency): Build fix (JSValue::type() is gone)
• runtime/JSArray.h: (JSC::JSArray::uncheckedSetIndex): Added for fast initialization of compact arrays. Does no bounds or other sanity checking.
• runtime/ArrayPrototype.cpp: (JSC::arrayProtoFuncSplice): Optimized creation of the returned JSArray.
• runtime/ArrayConstructor.cpp: (JSC::constructArrayWithSizeQuirk): Pass CreateInitialized to ctor.
• runtime/JSGlobalObject.h: (JSC::constructEmptyArray): Pass CreateInitialized to ctor.
• runtime/RegExpConstructor.cpp: (JSC::RegExpMatchesArray::RegExpMatchesArray): Pass CreateInitialized to ctor.

File:

• trunk/JavaScriptCore/runtime/JSArray.h (modified) (4 diffs)

trunk/JavaScriptCore/runtime/JSArray.h

@@ -23 +23 @@
 
 #include "JSObject.h"
+
+#define CHECK_ARRAY_CONSISTENCY 0
 
 namespace JSC {
@@ -34 +36 @@
         void* subclassData; // A JSArray subclass can use this to fill the vector lazily.
         size_t reportedMapCapacity;
+#if CHECK_ARRAY_CONSISTENCY
+        bool m_inCompactInitialization;
+#endif
         JSValue m_vector[1];
     };
+
+    // The CreateCompact creation mode is used for fast construction of arrays
+    // whose size and contents are known at time of creation.
+    //
+    // There are two obligations when using this mode:
+    //
+    //   - uncheckedSetIndex() must be used when initializing the array.
+    //   - setLength() must be called after initialization.
+
+    enum ArrayCreationMode { CreateCompact, CreateInitialized };
 
     class JSArray : public JSObject {
@@ -43 +58 @@
     public:
         explicit JSArray(NonNullPassRefPtr<Structure>);
-        JSArray(NonNullPassRefPtr<Structure>, unsigned initialLength);
+        JSArray(NonNullPassRefPtr<Structure>, unsigned initialLength, ArrayCreationMode);
         JSArray(NonNullPassRefPtr<Structure>, const ArgList& initialValues);
         virtual ~JSArray();
@@ -82 +97 @@
             }
             x = v;
+        }
+
+        void uncheckedSetIndex(unsigned i, JSValue v)
+        {
+            ASSERT(canSetIndex(i));
+#if CHECK_ARRAY_CONSISTENCY
+            ASSERT(m_storage->m_inCompactInitialization);
+#endif
+            m_storage->m_vector[i] = v;
         }