Use xorps to break the cvtsi2sd unnecessary dependence due to its partially written

src/ia32/macro-assembler-ia32.h

 // Copyright 2012 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 348 matching lines @@
   // Store the function for the given builtin in the target register.
   void GetBuiltinFunction(Register target, Builtins::JavaScript id);
 
   // Store the code object for the given builtin in the target register.
   void GetBuiltinEntry(Register target, Builtins::JavaScript id);
 
   // Expression support
   void Set(Register dst, const Immediate& x);
   void Set(const Operand& dst, const Immediate& x);
 
+  // cvtsi2sd instruction only writes to the low 64-bit of dst register, which
+  // hinders register renaming and makes dependence chains longer. So we use
+  // xorps to clear the dst register before cvtsi2sd to solve this issue.
+  void Cvtsi2sd(XMMRegister dst, Register src) { Cvtsi2sd(dst, Operand(src)); }
+  void Cvtsi2sd(XMMRegister dst, const Operand& src);
+
   // Support for constant splitting.
   bool IsUnsafeImmediate(const Immediate& x);
   void SafeSet(Register dst, const Immediate& x);
   void SafePush(const Immediate& x);
 
   // Compare object type for heap object.
   // Incoming register is heap_object and outgoing register is map.
   void CmpObjectType(Register heap_object, InstanceType type, Register map);
 
   // Compare instance type for map.
@@ skipping 695 matching lines @@
   }                                                                       \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_MACRO_ASSEMBLER_IA32_H_