[turbofan] Added the RoundInt64ToFloat64 instruction to TurboFan.

src/compiler/x64/instruction-selector-x64.cc

Index: src/compiler/x64/instruction-selector-x64.cc
diff --git a/src/compiler/x64/instruction-selector-x64.cc b/src/compiler/x64/instruction-selector-x64.cc
index d2b5f7685ae3b4c67a25ea0677ad046ca9edd649..b6dd082c3907023dd7a284d38b1f3fe81506563b 100644
--- a/src/compiler/x64/instruction-selector-x64.cc
+++ b/src/compiler/x64/instruction-selector-x64.cc
@@ -918,6 +918,12 @@ void InstructionSelector::VisitTruncateInt64ToInt32(Node* node) {
 }
 
 
+void InstructionSelector::VisitRoundInt64ToFloat64(Node* node) {
+  X64OperandGenerator g(this);
+  Emit(kSSEInt64ToFloat64, g.DefineAsRegister(node), g.Use(node->InputAt(0)));
+}
+
+
 void InstructionSelector::VisitBitcastFloat32ToInt32(Node* node) {
   X64OperandGenerator g(this);
   Emit(kX64BitcastFI, g.DefineAsRegister(node), g.Use(node->InputAt(0)));