Optimize array copyWithin for fast-array cases (#3295)

Performance results:
Intel: 0m9,7s -> 0m0,07s
ARM: over 10m -> 1m38s

JerryScript-DCO-1.0-Signed-off-by: Adam Szilagyi aszilagy@inf.u-szeged.hu

jerry-core/ecma/builtin-objects/ecma-builtin-array-prototype.c

@@ -2338,9 +2338,8 @@ ecma_builtin_array_prototype_object_copy_within (const ecma_value_t args[], /**<
     }
   }
 
-  ecma_free_value (error);
-
   uint32_t count = JERRY_MIN (end - start, len - target);
+
   bool forward = true;
 
   if (start < target && target < start + count)
@@ -2350,6 +2349,39 @@ ecma_builtin_array_prototype_object_copy_within (const ecma_value_t args[], /**<
     forward = false;
   }
 
+  if (ecma_op_object_is_fast_array (obj_p))
+  {
+    ecma_extended_object_t *ext_obj_p = (ecma_extended_object_t *) obj_p;
+
+    if (ext_obj_p->u.array.u.hole_count < ECMA_FAST_ARRAY_HOLE_ONE)
+    {
+      if (obj_p->u1.property_list_cp != JMEM_CP_NULL)
+      {
+        ecma_value_t *buffer_p = ECMA_GET_NON_NULL_POINTER (ecma_value_t, obj_p->u1.property_list_cp);
+
+        for (; count > 0; count--)
+        {
+          ecma_free_value_if_not_object (buffer_p[target]);
+          buffer_p[target] = ecma_copy_value_if_not_object (buffer_p[start]);
+
+          if (forward)
+          {
+            start++;
+            target++;
+          }
+          else
+          {
+            start--;
+            target--;
+          }
+        }
+      }
+
+      ecma_ref_object (obj_p);
+      return ecma_make_object_value (obj_p);
+    }
+  }
+
   while (count > 0)
   {
     ecma_value_t get_value = ecma_op_object_find_by_uint32_index (obj_p, start);