Short-circuit embedded cons strings.

src/hydrogen-instructions.cc

 // 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 3310 matching lines @@
 
 #undef DEFINE_NEW_H_SIMPLE_ARITHMETIC_INSTR
 
 
 HInstruction* HStringAdd::New(
     Zone* zone, HValue* context, HValue* left, HValue* right) {
   if (FLAG_fold_constants && left->IsConstant() && right->IsConstant()) {
     HConstant* c_right = HConstant::cast(right);
     HConstant* c_left = HConstant::cast(left);
     if (c_left->HasStringValue() && c_right->HasStringValue()) {
-      Factory* factory = Isolate::Current()->factory();
-      return new(zone) HConstant(factory->NewConsString(c_left->StringValue(),
-                                                        c_right->StringValue()),
-                                 Representation::Tagged());
+      Handle<String> concat = zone->isolate()->factory()->NewFlatConcatString(
+          c_left->StringValue(), c_right->StringValue());
+      return new(zone) HConstant(concat, Representation::Tagged());
     }
   }
   return new(zone) HStringAdd(context, left, right);
 }
 
 
 HInstruction* HStringCharFromCode::New(
     Zone* zone, HValue* context, HValue* char_code) {
   if (FLAG_fold_constants && char_code->IsConstant()) {
     HConstant* c_code = HConstant::cast(char_code);
@@ skipping 526 matching lines @@
     case kBackingStore:
       if (!name_.is_null()) stream->Add(*String::cast(*name_)->ToCString());
       stream->Add("[backing-store]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal