Optionally use 31-bits SMI value for 64-bit system

src/x64/lithium-x64.h

Index: src/x64/lithium-x64.h
diff --git a/src/x64/lithium-x64.h b/src/x64/lithium-x64.h
index 63f5227f8dc043b5bd45d2e10ae7c404b529ca6a..61b87b4c0d0f62f4c99d07545e7c520b5e95f559 100644
--- a/src/x64/lithium-x64.h
+++ b/src/x64/lithium-x64.h
@@ -1919,13 +1919,15 @@ class LUint32ToDouble: public LTemplateInstruction<1, 1, 1> {
 };
 
 
-class LNumberTagI: public LTemplateInstruction<1, 1, 0> {
+class LNumberTagI: public LTemplateInstruction<1, 1, 1> {
  public:
-  explicit LNumberTagI(LOperand* value) {
+  explicit LNumberTagI(LOperand* value, LOperand* temp) {
     inputs_[0] = value;
+    temps_[0] = temp;
   }
 
   LOperand* value() { return inputs_[0]; }
+  LOperand* temp() { return temps_[0]; }
 
   DECLARE_CONCRETE_INSTRUCTION(NumberTagI, "number-tag-i")
 };