Implemented the RoundUint64ToFloat64 TurboFan operator for x64 and arm64.

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 0f1dc816a15dd6ac8ab24da152c62d2c810e36c7..ac40dd6595f175e325b77f83f6d4788b2172db9d 100644
--- a/src/compiler/x64/instruction-selector-x64.cc
+++ b/src/compiler/x64/instruction-selector-x64.cc
@@ -971,6 +971,12 @@ void InstructionSelector::VisitRoundInt64ToFloat64(Node* node) {
 }
 
 
+void InstructionSelector::VisitRoundUint64ToFloat64(Node* node) {
+  X64OperandGenerator g(this);
+  Emit(kSSEUint64ToFloat64, 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)));