[turbofan] Avoid unnecessary write barriers and improve code generation.

src/compiler/machine-operator.h

 // Copyright 2013 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.
 
 #ifndef V8_COMPILER_MACHINE_OPERATOR_H_
 #define V8_COMPILER_MACHINE_OPERATOR_H_
 
 #include "src/base/flags.h"
 #include "src/compiler/machine-type.h"
 
@@ skipping 31 matching lines @@
 V8_INLINE size_t hash_value(TruncationMode mode) {
   return static_cast<uint8_t>(mode);
 }
 
 std::ostream& operator<<(std::ostream&, TruncationMode);
 
 TruncationMode TruncationModeOf(Operator const*);
 
 
 // Supported write barrier modes.
-enum WriteBarrierKind { kNoWriteBarrier, kFullWriteBarrier };
+enum WriteBarrierKind {
+  kNoWriteBarrier,
+  kMapWriteBarrier,
+  kPointerWriteBarrier,
+  kFullWriteBarrier
+};
 
 std::ostream& operator<<(std::ostream& os, WriteBarrierKind);
 
 
 // A Load needs a MachineType.
 typedef MachineType LoadRepresentation;
 
 
 // A Store needs a MachineType and a WriteBarrierKind in order to emit the
 // correct write barrier.
@@ skipping 255 matching lines @@
 };
 
 
 DEFINE_OPERATORS_FOR_FLAGS(MachineOperatorBuilder::Flags)
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_MACHINE_OPERATOR_H_