Immediate index operand for string [] and streamline code for generating array ops.

runtime/vm/flow_graph_compiler_x64.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_FLOW_GRAPH_COMPILER_X64_H_
 #define VM_FLOW_GRAPH_COMPILER_X64_H_
 
 #ifndef VM_FLOW_GRAPH_COMPILER_H_
 #error Include flow_graph_compiler.h instead of flow_graph_compiler_x64.h.
 #endif
@@ skipping 214 matching lines @@
     return current_block_->try_index();
   }
 
   bool may_reoptimize() const { return may_reoptimize_; }
 
   static Condition FlipCondition(Condition condition);
 
   static bool EvaluateCondition(Condition condition, intptr_t l, intptr_t r);
 
   // Array/list element address computations.
+  static intptr_t DataOffsetFor(intptr_t cid);
+  static intptr_t ElementSizeFor(intptr_t cid);
   static FieldAddress ElementAddressForIntIndex(intptr_t cid,
                                                 Register array,
                                                 intptr_t offset);
   static FieldAddress ElementAddressForRegIndex(intptr_t cid,
                                                 Register array,
                                                 Register index);
 
  private:
   void EmitFrameEntry();
 
@@ skipping 110 matching lines @@
   // that should be used when deoptimizing we store it in this variable.
   // In future AddDeoptStub should be moved out of the instruction template.
   Environment* pending_deoptimization_env_;
 
   DISALLOW_COPY_AND_ASSIGN(FlowGraphCompiler);
 };
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_COMPILER_X64_H_