[Atomics] Make Atomics.compareExchange a builtin using TF

src/compiler/ppc/instruction-selector-ppc.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"
 #include "src/ppc/frames-ppc.h"
 
@@ skipping 2101 matching lines @@
   size_t input_count = 0;
   inputs[input_count++] = g.UseUniqueRegister(base);
   inputs[input_count++] = g.UseUniqueRegister(index);
   inputs[input_count++] = g.UseUniqueRegister(value);
   Emit(opcode | AddressingModeField::encode(kMode_MRR),
       0, nullptr, input_count, inputs);
 }
 
 void InstructionSelector::VisitAtomicExchange(Node* node) { UNIMPLEMENTED(); }
 
+void InstructionSelector::VisitAtomicCompareExchange(Node* node) {
+  UNIMPLEMENTED();
+}
+
 // static
 MachineOperatorBuilder::Flags
 InstructionSelector::SupportedMachineOperatorFlags() {
   return MachineOperatorBuilder::kFloat32RoundDown |
          MachineOperatorBuilder::kFloat64RoundDown |
          MachineOperatorBuilder::kFloat32RoundUp |
          MachineOperatorBuilder::kFloat64RoundUp |
          MachineOperatorBuilder::kFloat32RoundTruncate |
          MachineOperatorBuilder::kFloat64RoundTruncate |
          MachineOperatorBuilder::kFloat64RoundTiesAway |
          MachineOperatorBuilder::kWord32Popcnt |
          MachineOperatorBuilder::kWord64Popcnt;
   // We omit kWord32ShiftIsSafe as s[rl]w use 0x3f as a mask rather than 0x1f.
 }
 
 // static
 MachineOperatorBuilder::AlignmentRequirements
 InstructionSelector::AlignmentRequirements() {
   return MachineOperatorBuilder::AlignmentRequirements::
       FullUnalignedAccessSupport();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8