[turbofan] Restore basic write barrier elimination.

src/compiler/simplified-operator.h

 // 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.
 
 #ifndef V8_COMPILER_SIMPLIFIED_OPERATOR_H_
 #define V8_COMPILER_SIMPLIFIED_OPERATOR_H_
 
 #include <iosfwd>
 
 #include "src/handles.h"
 #include "src/machine-type.h"
 #include "src/objects.h"
 
 namespace v8 {
 namespace internal {
 
 // Forward declarations.
 class Type;
 class Zone;
 
 
 namespace compiler {
 
 // Forward declarations.
 class Operator;
 struct SimplifiedOperatorGlobalCache;
 
+enum BaseTaggedness : uint8_t { kUntaggedBase, kTaggedBase };
 
-enum BaseTaggedness { kUntaggedBase, kTaggedBase };
+size_t hash_value(BaseTaggedness);
 
 std::ostream& operator<<(std::ostream&, BaseTaggedness);
 
 
 // An access descriptor for loads/stores of array buffers.
 class BufferAccess final {
  public:
   explicit BufferAccess(ExternalArrayType external_array_type)
       : external_array_type_(external_array_type) {}
 
@@ skipping 16 matching lines @@
 
 // An access descriptor for loads/stores of fixed structures like field
 // accesses of heap objects. Accesses from either tagged or untagged base
 // pointers are supported; untagging is done automatically during lowering.
 struct FieldAccess {
   BaseTaggedness base_is_tagged;  // specifies if the base pointer is tagged.
   int offset;                     // offset of the field, without tag.
   MaybeHandle<Name> name;         // debugging only.
   Type* type;                     // type of the field.
   MachineType machine_type;       // machine type of the field.
+  WriteBarrierKind write_barrier_kind;  // write barrier hint.
 
   int tag() const { return base_is_tagged == kTaggedBase ? kHeapObjectTag : 0; }
 };
 
 bool operator==(FieldAccess const&, FieldAccess const&);
 bool operator!=(FieldAccess const&, FieldAccess const&);
 
 size_t hash_value(FieldAccess const&);
 
 std::ostream& operator<<(std::ostream&, FieldAccess const&);
 
 FieldAccess const& FieldAccessOf(const Operator* op) WARN_UNUSED_RESULT;
 
 
 // An access descriptor for loads/stores of indexed structures like characters
 // in strings or off-heap backing stores. Accesses from either tagged or
 // untagged base pointers are supported; untagging is done automatically during
 // lowering.
 struct ElementAccess {
   BaseTaggedness base_is_tagged;  // specifies if the base pointer is tagged.
   int header_size;                // size of the header, without tag.
   Type* type;                     // type of the element.
   MachineType machine_type;       // machine type of the element.
+  WriteBarrierKind write_barrier_kind;  // write barrier hint.
 
   int tag() const { return base_is_tagged == kTaggedBase ? kHeapObjectTag : 0; }
 };
 
 bool operator==(ElementAccess const&, ElementAccess const&);
 bool operator!=(ElementAccess const&, ElementAccess const&);
 
 size_t hash_value(ElementAccess const&);
 
 std::ostream& operator<<(std::ostream&, ElementAccess const&);
@@ skipping 103 matching lines @@
   Zone* const zone_;
 
   DISALLOW_COPY_AND_ASSIGN(SimplifiedOperatorBuilder);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_SIMPLIFIED_OPERATOR_H_