Improve array to string conversion.

src/x64/lithium-x64.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 131 matching lines @@
   V(NumberUntagD)                               \
   V(ObjectLiteral)                              \
   V(OsrEntry)                                   \
   V(OuterContext)                               \
   V(Parameter)                                  \
   V(Power)                                      \
   V(PushArgument)                               \
   V(Random)                                     \
   V(RegExpLiteral)                              \
   V(Return)                                     \
+  V(SeqStringSetChar)                           \
   V(ShiftI)                                     \
   V(SmiTag)                                     \
   V(SmiUntag)                                   \
   V(StackCheck)                                 \
   V(StoreContextSlot)                           \
   V(StoreGlobalCell)                            \
   V(StoreGlobalGeneric)                         \
   V(StoreKeyed)                                 \
   V(StoreKeyedGeneric)                          \
   V(StoreNamedField)                            \
@@ skipping 986 matching lines @@
   Smi* index() const { return index_; }
 
   DECLARE_CONCRETE_INSTRUCTION(ValueOf, "date-field")
   DECLARE_HYDROGEN_ACCESSOR(ValueOf)
 
  private:
   Smi* index_;
 };
 
 
+class LSeqStringSetChar: public LTemplateInstruction<1, 3, 0> {
+ public:
+  LSeqStringSetChar(bool is_one_byte,
+                    LOperand* string,
+                    LOperand* index,
+                    LOperand* value) : is_one_byte_(is_one_byte) {
+    inputs_[0] = string;
+    inputs_[1] = index;
+    inputs_[2] = value;
+  }
+
+  LOperand* string() { return inputs_[0]; }
+  LOperand* index() { return inputs_[1]; }
+  LOperand* value() { return inputs_[2]; }
+  bool is_one_byte() { return is_one_byte_; }
+
+  DECLARE_CONCRETE_INSTRUCTION(SeqStringSetChar, "seq-string-set-char")
+  DECLARE_HYDROGEN_ACCESSOR(SeqStringSetChar)
+
+ private:
+  bool is_one_byte_;
+};
+
+
 class LThrow: public LTemplateInstruction<0, 1, 0> {
  public:
   explicit LThrow(LOperand* value) {
     inputs_[0] = value;
   }
 
   LOperand* value() { return inputs_[0]; }
 
   DECLARE_CONCRETE_INSTRUCTION(Throw, "throw")
 };
@@ skipping 1338 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(LChunkBuilder);
 };
 
 #undef DECLARE_HYDROGEN_ACCESSOR
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::int
 
 #endif  // V8_X64_LITHIUM_X64_H_