[turbofan] Restore basic write barrier elimination.

src/compiler/machine-operator.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/compiler/machine-operator.h"
 
 #include "src/base/lazy-instance.h"
 #include "src/compiler/opcodes.h"
 #include "src/compiler/operator.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
-std::ostream& operator<<(std::ostream& os, WriteBarrierKind kind) {
-  switch (kind) {
-    case kNoWriteBarrier:
-      return os << "NoWriteBarrier";
-    case kMapWriteBarrier:
-      return os << "MapWriteBarrier";
-    case kPointerWriteBarrier:
-      return os << "PointerWriteBarrier";
-    case kFullWriteBarrier:
-      return os << "FullWriteBarrier";
-  }
-  UNREACHABLE();
-  return os;
-}
-
-
 bool operator==(StoreRepresentation lhs, StoreRepresentation rhs) {
   return lhs.representation() == rhs.representation() &&
          lhs.write_barrier_kind() == rhs.write_barrier_kind();
 }
 
 
 bool operator!=(StoreRepresentation lhs, StoreRepresentation rhs) {
   return !(lhs == rhs);
 }
 
@@ skipping 606 matching lines @@
   }
   ATOMIC_TYPE_LIST(LOAD)
 #undef LOAD
   UNREACHABLE();
   return nullptr;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8