Changeset 184926 in webkit for trunk/Source/JavaScriptCore/builtins

Timestamp:

May 27, 2015, 4:43:22 PM (10 years ago)

Author:

[email protected]

Message:

REGRESSION: These sorting idioms used by Peacekeeper and Browsermark are ~20X slower
​https://bugs.webkit.org/show_bug.cgi?id=145412

Reviewed by Benjamin Poulain.

Cache strings when doing a string-converting sort.

This is a 21% speedup.

• builtins/Array.prototype.js:

(sort.stringComparator): Use subtraction instead of branching because
it's slightly faster.

(sort.comparatorSort):
(sort.stringSort):
(sort): Add a special case for string sorting to avoid redundant string
conversion.

• parser/Parser.cpp:

(JSC::Parser<LexerType>::createBindingPattern): Names can be empty if
they are private names.

File:

• trunk/Source/JavaScriptCore/builtins/Array.prototype.js (modified) (4 diffs)

trunk/Source/JavaScriptCore/builtins/Array.prototype.js

@@ -287 +287 @@
     function stringComparator(a, b)
     {
-        var aString = @toString(a);
-        var bString = @toString(b);
+        var aString = a.string;
+        var bString = b.string;
 
         var aLength = aString.length;
@@ -301 +301 @@
                 continue;
 
-            if (aCharCode < bCharCode)
-                return -1;
-
-            return 1;
-        }
-
-        if (aLength == bLength)
-            return 0;
-
-        if (aLength < bLength)
-            return -1;
-
-        return 1;
+            return aCharCode - bCharCode;
+        }
+
+        return aLength - bLength;
     }
 
@@ -441 +432 @@
     }
 
+    function stringSort(array)
+    {
+        var length = array.length >>> 0;
+
+        // For compatibility with Firefox and Chrome, do nothing observable
+        // to the target array if it has 0 or 1 sortable properties.
+        if (length < 2)
+            return;
+
+        var valueCount = compact(array, length);
+
+        var strings = new @Array(valueCount);
+        for (var i = 0; i < valueCount; ++i)
+            strings[i] = { string: @toString(array[i]), value: array[i] };
+
+        mergeSort(strings, valueCount, stringComparator);
+
+        for (var i = 0; i < valueCount; ++i)
+            array[i] = strings[i].value;
+    }
+
     if (this === null)
         throw new @TypeError("Array.prototype.sort requires that |this| not be null");
@@ -450 +462 @@
         throw new @TypeError("Attempted to assign to readonly property.");
 
-    if (typeof comparator !== "function")
-        comparator = stringComparator;
-
-    var array = @Object(this);
-    comparatorSort(array, comparator);
+    var array = @Object(this);
+
+    if (typeof comparator == "function")
+        comparatorSort(array, comparator);
+    else
+        stringSort(array);
+
     return array;
 }