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

src/ppc/macro-assembler-ppc.cc

Index: src/ppc/macro-assembler-ppc.cc
diff --git a/src/ppc/macro-assembler-ppc.cc b/src/ppc/macro-assembler-ppc.cc
index 49ec792d44dbeb3d890083902f7ad96e30138e56..8eb352bb1062fd965a1a1b66c2268eb9e0fff612 100644
--- a/src/ppc/macro-assembler-ppc.cc
+++ b/src/ppc/macro-assembler-ppc.cc
@@ -664,6 +664,15 @@ void MacroAssembler::ConvertIntToFloat(const DoubleRegister dst,
 }
 
 
+#if V8_TARGET_ARCH_PPC64
+void MacroAssembler::ConvertInt64ToDouble(Register src,
+                                          DoubleRegister double_dst) {
+  MovInt64ToDouble(double_dst, src);
+  fcfid(double_dst, double_dst);
+}
+#endif
+
+
 void MacroAssembler::ConvertDoubleToInt64(const DoubleRegister double_input,
 #if !V8_TARGET_ARCH_PPC64
                                           const Register dst_hi,