PPC: [turbofan] Added the RoundInt64ToFloat64 instruction to TurboFan.

src/ppc/macro-assembler-ppc.h

Index: src/ppc/macro-assembler-ppc.h
diff --git a/src/ppc/macro-assembler-ppc.h b/src/ppc/macro-assembler-ppc.h
index f4f7d5cc1a5468a2c6dd64067948ad3db7b059e9..60f8a22fe379a6689f0c1f2c3afa947b4c08991b 100644
--- a/src/ppc/macro-assembler-ppc.h
+++ b/src/ppc/macro-assembler-ppc.h
@@ -385,6 +385,10 @@ class MacroAssembler : public Assembler {
   void ConvertIntToFloat(const DoubleRegister dst, const Register src,
                          const Register int_scratch);
 
+#if V8_TARGET_ARCH_PPC64
+  void ConvertInt64ToDouble(Register src, DoubleRegister double_dst);
+#endif
+
   // Converts the double_input to an integer.  Note that, upon return,
   // the contents of double_dst will also hold the fixed point representation.
   void ConvertDoubleToInt64(const DoubleRegister double_input,