[turbofan] Added the RoundInt64ToFloat64 instruction to TurboFan.

src/compiler/ppc/instruction-selector-ppc.cc

Index: src/compiler/ppc/instruction-selector-ppc.cc
diff --git a/src/compiler/ppc/instruction-selector-ppc.cc b/src/compiler/ppc/instruction-selector-ppc.cc
index d211a439135c7fe761ded2abb6a13a1e106e61ff..42f62ea5762aae596b69db6c61790c439e251995 100644
--- a/src/compiler/ppc/instruction-selector-ppc.cc
+++ b/src/compiler/ppc/instruction-selector-ppc.cc
@@ -867,6 +867,11 @@ void InstructionSelector::VisitChangeInt32ToFloat64(Node* node) {
 }
 
 
+void InstructionSelector::VisitChangeInt64ToFloat64(Node* node) {
+  UNIMPLEMENTED();
+}
+
+
 void InstructionSelector::VisitChangeUint32ToFloat64(Node* node) {
   VisitRR(this, kPPC_Uint32ToDouble, node);
 }