Add initial hydrogenized NewStringAddStub.

src/hydrogen.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1258 matching lines @@
                                    HValue* length);
 
   void BuildTransitionElementsKind(HValue* object,
                                    HValue* map,
                                    ElementsKind from_kind,
                                    ElementsKind to_kind,
                                    bool is_jsarray);
 
   HValue* BuildNumberToString(HValue* object, Handle<Type> type);
 
+  // Computes the size for a sequential string of the given length and encoding.
+  HValue* BuildSeqStringSizeFor(HValue* length,
+                                String::Encoding encoding);
+  // Copies characters from one sequential string to another.
+  void BuildCopySeqStringChars(HValue* src,
+                               HValue* src_offset,
+                               String::Encoding src_encoding,
+                               HValue* dst,
+                               HValue* dst_offset,
+                               String::Encoding dst_encoding,
+                               HValue* length);
+  // Both operands are non-empty strings.
+  HValue* BuildUncheckedStringAdd(HValue* left,
+                                  HValue* right,
+                                  PretenureFlag pretenure_flag);
+  // Both operands are strings.
+  HValue* BuildStringAdd(HValue* left,
+                         HValue* right,
+                         PretenureFlag pretenure_flag);
+
   HInstruction* BuildUncheckedMonomorphicElementAccess(
       HValue* checked_object,
       HValue* key,
       HValue* val,
       bool is_js_array,
       ElementsKind elements_kind,
       bool is_store,
       LoadKeyedHoleMode load_mode,
       KeyedAccessStoreMode store_mode);
 
   HInstruction* AddElementAccess(
       HValue* elements,
       HValue* checked_key,
       HValue* val,
       HValue* dependency,
       ElementsKind elements_kind,
       bool is_store,
       LoadKeyedHoleMode load_mode = NEVER_RETURN_HOLE);
 
   HLoadNamedField* BuildLoadNamedField(HValue* object, HObjectAccess access);
   HInstruction* AddLoadNamedField(HValue* object, HObjectAccess access);
   HInstruction* BuildLoadStringLength(HValue* object, HValue* checked_value);
-  HStoreNamedField* AddStoreMapConstant(HValue* object, Handle<Map>);
+  HStoreNamedField* AddStoreMapConstant(HValue* object, Handle<Map> map);
+  HStoreNamedField* AddStoreMapConstantNoWriteBarrier(HValue* object,
+                                                      Handle<Map> map) {
+    HStoreNamedField* store_map = AddStoreMapConstant(object, map);
+    store_map->SkipWriteBarrier();
+    return store_map;
+  }
   HLoadNamedField* AddLoadElements(HValue* object);
 
   bool MatchRotateRight(HValue* left,
                         HValue* right,
                         HValue** operand,
                         HValue** shift_amount);
 
   HInstruction* BuildBinaryOperation(Token::Value op,
                                      HValue* left,
                                      HValue* right,
@@ skipping 1184 matching lines @@
   }
 
  private:
   HGraphBuilder* builder_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_H_