Revert of [Atomics] Remove Atomics code stubs; use TF ops

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 2006 matching lines @@
 
 
 void InstructionSelector::VisitFloat64InsertHighWord32(Node* node) {
   X64OperandGenerator g(this);
   Node* left = node->InputAt(0);
   Node* right = node->InputAt(1);
   Emit(kSSEFloat64InsertHighWord32, g.DefineSameAsFirst(node),
        g.UseRegister(left), g.Use(right));
 }
 
-void InstructionSelector::VisitAtomicLoad(Node* node) {
-  LoadRepresentation load_rep = LoadRepresentationOf(node->op());
-  DCHECK(load_rep.representation() == MachineRepresentation::kWord8 ||
-         load_rep.representation() == MachineRepresentation::kWord16 ||
-         load_rep.representation() == MachineRepresentation::kWord32);
-  USE(load_rep);
-  VisitLoad(node);
-}
 
 // static
 MachineOperatorBuilder::Flags
 InstructionSelector::SupportedMachineOperatorFlags() {
   MachineOperatorBuilder::Flags flags =
       MachineOperatorBuilder::kFloat32Max |
       MachineOperatorBuilder::kFloat32Min |
       MachineOperatorBuilder::kFloat64Max |
       MachineOperatorBuilder::kFloat64Min |
       MachineOperatorBuilder::kWord32ShiftIsSafe |
@@ skipping 11 matching lines @@
              MachineOperatorBuilder::kFloat64RoundTruncate |
              MachineOperatorBuilder::kFloat32RoundTiesEven |
              MachineOperatorBuilder::kFloat64RoundTiesEven;
   }
   return flags;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8