Fix Array length check

Author: rhuanjl

lib/Runtime/Library/JsBuiltIn/JsBuiltIn.js

@@ -187,11 +187,9 @@
             __chakraLibrary.arrayCreateDataPropertyOrThrow(compareArray, index, "" + array[index]);
         }
 
-        const fast = length < 1073741825;
         const buffer = [];
         const stringBuffer = [];
-
-        let i = 1, j = 0, k = 0, bucketSize = 4, position = 0;
+        let i = 1, j = 0, k = 0, bucketSize = 4, lastSize = 2, position = 0;
 
         // handle pairs first
         while (i < length) {
@@ -212,11 +210,11 @@
             while (position < length) {
                 const left = position;
                 let right = position + bucketSize;
-                right < length ? right : length;
-                const mid = fast ? left + right >> 1 : (left + right) / 2 |0;
+                const mid = left + lastSize;
 
                 // perform a merge but only if it's necessary
-                if (mid < length && compareArray[mid - 1] > compareArray[mid]) {
+                if (mid < length && compareArray[mid] < compareArray[mid - 1]) {
+                    right = right < length ? right : length;
                     i = left, j = 0, k = left;
                     const currentLength = buffer.length;
 
@@ -269,14 +267,14 @@
                 position += bucketSize;
             }
             position = 0;
+            lastSize = bucketSize;
             bucketSize *= 2;
         }
     });
 
     platform.registerChakraLibraryFunction("MergeSort", function(array, length, compareFn) {
-        const fast = length < 1073741825;
         const buffer = [];
-        let i = 1, j = 0, k = 0, bucketSize = 4, position = 0;
+        let i = 1, j = 0, k = 0, bucketSize = 4, lastSize = 2, position = 0;
 
         // handle pairs first
         while (i < length) {
@@ -294,11 +292,11 @@
             while (position < length) {
                 const left = position;
                 let right = position + bucketSize;
-                right < length ? right : length;
-                const mid = fast ? left + right >> 1 : (left + right) / 2 |0;
+                const mid = left + lastSize;
 
                 // perform a merge but only if it's necessary
-                if (mid < length && compareFn(array[mid - 1], array[mid]) > 0) {
+                if (mid < length && compareFn(array[mid], array[mid - 1]) < 0) {
+                    right = right < length ? right : length;
                     i = left, j = 0, k = left;
                     const currentLength = buffer.length;
 
@@ -342,6 +340,7 @@
                 position += bucketSize;
             }
             position = 0;
+            lastSize = bucketSize;
             bucketSize *= 2;
         }
     });
@@ -376,35 +375,33 @@
             __chakraLibrary.raiseFunctionArgument_NeedFunction("Array.prototype.sort");
         }
 
-        const objInfo = __chakraLibrary.CheckArrayAndGetLen(this, "Array.prototype.sort");
-        const array = objInfo.o;
-        let len = objInfo.len;
+        const {o, len} = __chakraLibrary.CheckArrayAndGetLen(this, "Array.prototype.sort");
 
         if (len < 2) { // early return if length < 2
-            return array;
+            return o;
         }
 
         // check for if the array has any missing values
         // also pull in any values from the prototype
-        let i = 0;
+        let i = 0, length = len;
         while (i < len) {
-            if (array[i] === undefined) {
-                len = __chakraLibrary.FillArrayHoles(array, len, i);
+            if (o[i] === undefined) {
+                length = __chakraLibrary.FillArrayHoles(o, len, i);
                 break;
             }
-            array[i] = array[i++];
+            o[i] = o[i++];
         }
 
-        if (len > 1)
+        if (length > 1)
         {
             if (compareFn !== undefined) {
-                __chakraLibrary.MergeSort(array, len, compareFn);
+                __chakraLibrary.MergeSort(o, length, compareFn);
             } else {
-                __chakraLibrary.DefaultMergeSort(array, len);
+                __chakraLibrary.DefaultMergeSort(o, length);
             }
         }
 
-        return array;
+        return o;
     });
 
     platform.registerFunction(platform.FunctionKind.Array_filter, function (callbackfn, thisArg = undefined) {