[turbofan] Added the optional Float64RoundTiesEven operator to turbofan.

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

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <algorithm>
 
 #include "src/base/adapters.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
@@ skipping 1120 matching lines @@
 void InstructionSelector::VisitFloat64RoundTruncate(Node* node) {
   VisitRR(this, node, kSSEFloat64Round | MiscField::encode(kRoundToZero));
 }
 
 
 void InstructionSelector::VisitFloat64RoundTiesAway(Node* node) {
   UNREACHABLE();
 }
 
 
+void InstructionSelector::VisitFloat64RoundTiesEven(Node* node) {
+  VisitRR(this, node, kSSEFloat64Round | MiscField::encode(kRoundToNearest));
+}
+
+
 void InstructionSelector::EmitPrepareArguments(NodeVector* arguments,
                                                const CallDescriptor* descriptor,
                                                Node* node) {
   X64OperandGenerator g(this);
 
   // Prepare for C function call.
   if (descriptor->IsCFunctionCall()) {
     Emit(kArchPrepareCallCFunction |
              MiscField::encode(static_cast<int>(descriptor->CParameterCount())),
          0, nullptr, 0, nullptr);
@@ skipping 510 matching lines @@
       MachineOperatorBuilder::kFloat64Min |
       MachineOperatorBuilder::kWord32ShiftIsSafe |
       MachineOperatorBuilder::kWord32Ctz | MachineOperatorBuilder::kWord64Ctz;
   if (CpuFeatures::IsSupported(POPCNT)) {
     flags |= MachineOperatorBuilder::kWord32Popcnt |
              MachineOperatorBuilder::kWord64Popcnt;
   }
   if (CpuFeatures::IsSupported(SSE4_1)) {
     flags |= MachineOperatorBuilder::kFloat64RoundDown |
              MachineOperatorBuilder::kFloat64RoundUp |
-             MachineOperatorBuilder::kFloat64RoundTruncate;
+             MachineOperatorBuilder::kFloat64RoundTruncate |
+             MachineOperatorBuilder::kFloat64RoundTiesEven;
   }
   return flags;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8