Improve array to string conversion.

src/ia32/lithium-ia32.h

Index: src/ia32/lithium-ia32.h
diff --git a/src/ia32/lithium-ia32.h b/src/ia32/lithium-ia32.h
index 2067c62d1bd7c49cbaefbfa133ee367ad49f78e0..4d0cf3f52f1b61720775ceb7d6765b755744ec1c 100644
--- a/src/ia32/lithium-ia32.h
+++ b/src/ia32/lithium-ia32.h
@@ -144,6 +144,7 @@ class LCodeGen;
   V(PushArgument)                               \
   V(RegExpLiteral)                              \
   V(Return)                                     \
+  V(SeqStringSetChar)                           \
   V(ShiftI)                                     \
   V(SmiTag)                                     \
   V(SmiUntag)                                   \
@@ -1179,6 +1180,30 @@ class LDateField: public LTemplateInstruction<1, 1, 1> {
 };
 
 
+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, 2, 0> {
  public:
   LThrow(LOperand* context, LOperand* value) {