X87: [TurboFan] enable the Float64RoundDown and Float64RoundTruncate operators in x87.

src/compiler/x87/instruction-selector-x87.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 "src/base/adapters.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
 namespace v8 {
@@ skipping 1282 matching lines @@
 InstructionSelector::SupportedMachineOperatorFlags() {
   MachineOperatorBuilder::Flags flags =
       MachineOperatorBuilder::kFloat32Max |
       MachineOperatorBuilder::kFloat32Min |
       MachineOperatorBuilder::kFloat64Max |
       MachineOperatorBuilder::kFloat64Min |
       MachineOperatorBuilder::kWord32ShiftIsSafe;
   if (CpuFeatures::IsSupported(POPCNT)) {
     flags |= MachineOperatorBuilder::kWord32Popcnt;
   }
+
+  flags |= MachineOperatorBuilder::kFloat64RoundDown |
+           MachineOperatorBuilder::kFloat64RoundTruncate;
   return flags;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8