Simplify some code related to x64 calling convention.

src/x64/assembler-x64.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // 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.
 //
@@ skipping 182 matching lines @@
 const Register r8 = { kRegister_r8_Code };
 const Register r9 = { kRegister_r9_Code };
 const Register r10 = { kRegister_r10_Code };
 const Register r11 = { kRegister_r11_Code };
 const Register r12 = { kRegister_r12_Code };
 const Register r13 = { kRegister_r13_Code };
 const Register r14 = { kRegister_r14_Code };
 const Register r15 = { kRegister_r15_Code };
 const Register no_reg = { kRegister_no_reg_Code };
 
+#ifdef _WIN64
+  // Windows calling convention

[mvstanton, 2013/04/24 10:54:54]

Can you mention fastcall here?

+  const Register arg_reg_1 = rcx;
+  const Register arg_reg_2 = rdx;
+  const Register arg_reg_3 = r8;
+  const Register arg_reg_4 = r9;
+#else
+  // AMD64 calling convention
+  const Register arg_reg_1 = rdi;
+  const Register arg_reg_2 = rsi;
+  const Register arg_reg_3 = rdx;
+  const Register arg_reg_4 = rcx;
+#endif  // _WIN64
 
 struct XMMRegister {
   static const int kMaxNumRegisters = 16;
   static const int kMaxNumAllocatableRegisters = 15;
   static int NumAllocatableRegisters() {
     return kMaxNumAllocatableRegisters;
   }
 
   static int ToAllocationIndex(XMMRegister reg) {
     ASSERT(reg.code() != 0);
@@ skipping 1425 matching lines @@
  private:
   Assembler* assembler_;
 #ifdef DEBUG
   int space_before_;
 #endif
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_ASSEMBLER_X64_H_