x64: Make sure that the upper half of a 64bit register contains 0 for int32 values.

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 1228 matching lines @@
  public:
   LBitI(LOperand* left, LOperand* right) {
     inputs_[0] = left;
     inputs_[1] = right;
   }
 
   LOperand* left() { return inputs_[0]; }
   LOperand* right() { return inputs_[1]; }
 
   Token::Value op() const { return hydrogen()->op(); }
+  bool IsInteger32() const {
+    return hydrogen()->representation().IsInteger32();
+  }
 
   DECLARE_CONCRETE_INSTRUCTION(BitI, "bit-i")
   DECLARE_HYDROGEN_ACCESSOR(Bitwise)
 };
 
 
 class LShiftI V8_FINAL : public LTemplateInstruction<1, 2, 0> {
  public:
   LShiftI(Token::Value op, LOperand* left, LOperand* right, bool can_deopt)
       : op_(op), can_deopt_(can_deopt) {
@@ skipping 1568 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(LChunkBuilder);
 };
 
 #undef DECLARE_HYDROGEN_ACCESSOR
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::int
 
 #endif  // V8_X64_LITHIUM_X64_H_