[turbofan] Added the optional Float64RoundTiesEven operator 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 38878c5e7cb7d84cfa714714f3788cf68f556d56..426b5c65ccddb11d1219a4ef4daefccfcb30926a 100644
--- a/src/compiler/x64/instruction-selector-x64.cc
+++ b/src/compiler/x64/instruction-selector-x64.cc
@@ -1138,6 +1138,11 @@ void InstructionSelector::VisitFloat64RoundTiesAway(Node* node) {
 }
 
 
+void InstructionSelector::VisitFloat64RoundTiesEven(Node* node) {
+  VisitRR(this, node, kSSEFloat64Round | MiscField::encode(kRoundToNearest));
+}
+
+
 void InstructionSelector::EmitPrepareArguments(NodeVector* arguments,
                                                const CallDescriptor* descriptor,
                                                Node* node) {
@@ -1668,7 +1673,8 @@ InstructionSelector::SupportedMachineOperatorFlags() {
   if (CpuFeatures::IsSupported(SSE4_1)) {
     flags |= MachineOperatorBuilder::kFloat64RoundDown |
              MachineOperatorBuilder::kFloat64RoundUp |
-             MachineOperatorBuilder::kFloat64RoundTruncate;
+             MachineOperatorBuilder::kFloat64RoundTruncate |
+             MachineOperatorBuilder::kFloat64RoundTiesEven;
   }
   return flags;
 }