Improve C++ code for string splittig (Dromaeo benchmark).

runtime/vm/object.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 3982 matching lines @@
                                   const String& str2,
                                   Heap::Space space);
   static RawOneByteString* ConcatAll(const Array& strings,
                                      intptr_t len,
                                      Heap::Space space);
 
   static RawOneByteString* Transform(int32_t (*mapping)(int32_t ch),
                                      const String& str,
                                      Heap::Space space);
 
+  // High performance version of substring for one-byte strings.
+  // "str" must be OneByteString.
+  static RawOneByteString* SubStringUnchecked(const String& str,
+                                              intptr_t begin_index,
+                                              intptr_t length,
+                                              Heap::Space space);
+
   static const ClassId kClassId = kOneByteStringCid;
 
   static RawOneByteString* null() {
     return reinterpret_cast<RawOneByteString*>(Object::null());
   }
 
  private:
   static RawOneByteString* raw(const String& str) {
     return reinterpret_cast<RawOneByteString*>(str.raw());
   }
@@ skipping 398 matching lines @@
     return *ObjectAddr(index);
   }
   void SetAt(intptr_t index, const Object& value) const {
     ASSERT(!IsNull());
     ASSERT(index < Length());
     const Array& arr = Array::Handle(data());
     arr.SetAt(index, value);
   }
 
   void Add(const Object& value, Heap::Space space = Heap::kNew) const;
+  void Add(Isolate* isolate,
+           const Object& value,
+           Heap::Space space = Heap::kNew) const;
+
   void Grow(intptr_t new_capacity, Heap::Space space = Heap::kNew) const;
   RawObject* RemoveLast() const;
 
   virtual RawAbstractTypeArguments* GetTypeArguments() const {
     ASSERT(AbstractTypeArguments::AreEqual(
         AbstractTypeArguments::Handle(Array::Handle(data()).GetTypeArguments()),
         AbstractTypeArguments::Handle(raw_ptr()->type_arguments_)));
     return raw_ptr()->type_arguments_;
   }
   virtual void SetTypeArguments(const AbstractTypeArguments& value) const {
@@ skipping 1542 matching lines @@
     if (this->CharAt(i) != str.CharAt(begin_index + i)) {
       return false;
     }
   }
   return true;
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_