[x64] Make use of vxorpd when AVX is enabled.

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index 01a449f6098967094accb6d6edcdf8e8b29f82ed..e1538ad48a6e6761440f4f553924b2f44a27b937 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -808,7 +808,7 @@ class MacroAssembler: public Assembler {
 
   // 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.
+  // xorpd to clear the dst register before cvtsi2sd to solve this issue.
   void Cvtlsi2sd(XMMRegister dst, Register src);
   void Cvtlsi2sd(XMMRegister dst, const Operand& src);
 
@@ -905,6 +905,8 @@ class MacroAssembler: public Assembler {
   void Movq(XMMRegister dst, Register src);
   void Movq(Register dst, XMMRegister src);
 
+  void Xorpd(XMMRegister dst, XMMRegister src);
+
   // Control Flow
   void Jump(Address destination, RelocInfo::Mode rmode);
   void Jump(ExternalReference ext);