Start using the overwrite mode from the full codegens to generate...

src/x64/code-stubs-x64.h

 // Copyright 2010 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 94 matching lines @@
   // stack together with the actual call.
   void GenerateCall(MacroAssembler* masm, Register left, Register right);
   void GenerateCall(MacroAssembler* masm, Register left, Smi* right);
   void GenerateCall(MacroAssembler* masm, Smi* left, Register right);
 
   Result GenerateCall(MacroAssembler* masm,
                       VirtualFrame* frame,
                       Result* left,
                       Result* right);
 
+  bool ArgsInRegistersSupported() {
+    return (op_ == Token::ADD) || (op_ == Token::SUB)
+        || (op_ == Token::MUL) || (op_ == Token::DIV);
+  }
+
  private:
   Token::Value op_;
   OverwriteMode mode_;
   GenericBinaryFlags flags_;
   bool args_in_registers_;  // Arguments passed in registers not on the stack.
   bool args_reversed_;  // Left and right argument are swapped.
 
   // Number type information of operands, determined by code generator.
   TypeInfo static_operands_type_;
 
@@ skipping 40 matching lines @@
            | RuntimeTypeInfoBits::encode(runtime_operands_type_);
   }
 
   void Generate(MacroAssembler* masm);
   void GenerateSmiCode(MacroAssembler* masm, Label* slow);
   void GenerateLoadArguments(MacroAssembler* masm);
   void GenerateReturn(MacroAssembler* masm);
   void GenerateRegisterArgsPush(MacroAssembler* masm);
   void GenerateTypeTransition(MacroAssembler* masm);
 
-  bool ArgsInRegistersSupported() {
-    return (op_ == Token::ADD) || (op_ == Token::SUB)
-        || (op_ == Token::MUL) || (op_ == Token::DIV);
-  }
   bool IsOperationCommutative() {
     return (op_ == Token::ADD) || (op_ == Token::MUL);
   }
 
   void SetArgsInRegisters() { args_in_registers_ = true; }
   void SetArgsReversed() { args_reversed_ = true; }
   bool HasSmiCodeInStub() { return (flags_ & NO_SMI_CODE_IN_STUB) == 0; }
   bool HasArgsInRegisters() { return args_in_registers_; }
   bool HasArgsReversed() { return args_reversed_; }
 
@@ skipping 194 matching lines @@
     return ObjectBits::encode(object_.code()) |
            AddressBits::encode(addr_.code()) |
            ScratchBits::encode(scratch_.code());
   }
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_CODE_STUBS_X64_H_