Refactor the arithmetic instructions for x64 port

test/cctest/test-assembler-x64.cc

 // Copyright 2009 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 123 matching lines @@
   __ ret(0);
 
   CodeDesc desc;
   assm.GetCode(&desc);
   // Call the function from C++.
   int result =  FUNCTION_CAST<F2>(buffer)(3, 2);
   CHECK_EQ(5, result);
 }
 
 
+TEST(AssemblerX64CmpbOperation) {
+  // Allocate an executable page of memory.
+  size_t actual_size;
+  byte* buffer = static_cast<byte*>(OS::Allocate(Assembler::kMinimalBufferSize,
+                                                 &actual_size,
+                                                 true));
+  CHECK(buffer);
+  Assembler assm(CcTest::i_isolate(), buffer, static_cast<int>(actual_size));
+
+  // Assemble a function that compare argument byte returing 1 if equal else 0.
+  // On Windows, it compares rcx with rdx which does not require REX prefix;
+  // on Linux, it compares rdi with rsi which requires REX prefix.
+
+  Label done;
+  __ movq(rax, Immediate(1));
+  __ cmpb(arg1, arg2);
+  __ j(equal, &done);
+  __ movq(rax, Immediate(0));
+  __ bind(&done);
+  __ ret(0);
+
+  CodeDesc desc;
+  assm.GetCode(&desc);
+  // Call the function from C++.
+  int result =  FUNCTION_CAST<F2>(buffer)(0x1002, 0x2002);
+  CHECK_EQ(1, result);
+  result =  FUNCTION_CAST<F2>(buffer)(0x1002, 0x2003);
+  CHECK_EQ(0, result);
+}
+
+
 TEST(AssemblerX64ImulOperation) {
   // Allocate an executable page of memory.
   size_t actual_size;
   byte* buffer = static_cast<byte*>(OS::Allocate(Assembler::kMinimalBufferSize,
                                                  &actual_size,
                                                  true));
   CHECK(buffer);
   Assembler assm(CcTest::i_isolate(), buffer, static_cast<int>(actual_size));
 
   // Assemble a simple function that multiplies arguments returning the high
@@ skipping 552 matching lines @@
       Handle<Code>())->ToObjectChecked());
   CHECK(code->IsCode());
 #ifdef OBJECT_PRINT
   Code::cast(code)->Print();
 #endif
 
   F6 f = FUNCTION_CAST<F6>(Code::cast(code)->entry());
   CHECK_EQ(2, f(1.0, 2.0));
 }
 #undef __