Reapply r4686: Complete version of full codegen for x64....

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
===================================================================
--- src/x64/macro-assembler-x64.cc	(revision 4688)
+++ src/x64/macro-assembler-x64.cc	(working copy)
@@ -802,7 +802,7 @@
 
 void MacroAssembler::SmiSub(Register dst,
                             Register src1,
-                            Operand const& src2,
+                            const Operand& src2,
                             Label* on_not_smi_result) {
   if (on_not_smi_result == NULL) {
     // No overflow checking. Use only when it's known that
@@ -920,6 +920,14 @@
 }
 
 
+void MacroAssembler::SmiAddConstant(const Operand& dst, Smi* constant) {
+  if (constant->value() != 0) {
+    Move(kScratchRegister, constant);
+    addq(dst, kScratchRegister);
+  }
+}
+
+
 void MacroAssembler::SmiAddConstant(Register dst,
                                     Register src,
                                     Smi* constant,