Port CompileMathFloorCall from ia32 to x64

src/x64/assembler-x64.h

Index: src/x64/assembler-x64.h
diff --git a/src/x64/assembler-x64.h b/src/x64/assembler-x64.h
index 4e36b6e4bc4062ead3023e978af5e2115b7c99db..71dc27807611b650742296cb8a6e351e7ac1ec72 100644
--- a/src/x64/assembler-x64.h
+++ b/src/x64/assembler-x64.h
@@ -1386,6 +1386,8 @@ class Assembler : public AssemblerBase {
   void movmskpd(Register dst, XMMRegister src);
   void movmskps(Register dst, XMMRegister src);
 
+  void cmpltsd(XMMRegister dst, XMMRegister src);
+
   // The first argument is the reg field, the second argument is the r/m field.
   void emit_sse_operand(XMMRegister dst, XMMRegister src);
   void emit_sse_operand(XMMRegister reg, const Operand& adr);