X64 implementation: Emit correct merge code for virtual frames at CFG merges.

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
===================================================================
--- src/x64/macro-assembler-x64.h	(revision 2231)
+++ src/x64/macro-assembler-x64.h	(working copy)
@@ -158,6 +158,21 @@
   void Set(Register dst, int64_t x);
   void Set(const Operand& dst, int64_t x);
 
+  // Handle support
+  bool IsUnsafeSmi(Smi* value);
+  bool IsUnsafeSmi(Handle<Object> value) {
+    return IsUnsafeSmi(Smi::cast(*value));
+  }
+
+  void LoadUnsafeSmi(Register dst, Smi* source);
+  void LoadUnsafeSmi(Register dst, Handle<Object> source) {
+    LoadUnsafeSmi(dst, Smi::cast(*source));
+  }
+
+  void Move(Register dst, Handle<Object> source);
+  void Move(const Operand& dst, Handle<Object> source);
+  void Cmp(Register dst, Handle<Object> source);
+
   // Control Flow
   void Jump(Address destination, RelocInfo::Mode rmode);
   void Jump(ExternalReference ext);