[turbofan] Make Node::set_op safer via wrapper.

src/compiler/node.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_NODE_H_
 #define V8_COMPILER_NODE_H_
 
 #include "src/compiler/opcodes.h"
 #include "src/compiler/operator.h"
 #include "src/types.h"
@@ skipping 31 matching lines @@
 class Node final {
  public:
   static Node* New(Zone* zone, NodeId id, const Operator* op, int input_count,
                    Node* const* inputs, bool has_extensible_inputs);
   static Node* Clone(Zone* zone, NodeId id, const Node* node);
 
   bool IsDead() const { return InputCount() > 0 && !InputAt(0); }
   void Kill();
 
   const Operator* op() const { return op_; }
-  void set_op(const Operator* op) { op_ = op; }
 
   IrOpcode::Value opcode() const {
     DCHECK(op_->opcode() <= IrOpcode::kLast);
     return static_cast<IrOpcode::Value>(op_->opcode());
   }
 
   NodeId id() const { return IdField::decode(bit_field_); }
 
   int InputCount() const {
     return has_inline_inputs() ? InlineCountField::decode(bit_field_)
@@ skipping 214 matching lines @@
     Use* ptr = has_inline_inputs() ? reinterpret_cast<Use*>(this)
                                    : reinterpret_cast<Use*>(inputs_.outline_);
     return &ptr[-1 - input_index];
   }
 
   void AppendUse(Use* use);
   void RemoveUse(Use* use);
 
   void* operator new(size_t, void* location) { return location; }
 
+  // Only NodeProperties should manipulate the op.
+  void set_op(const Operator* op) { op_ = op; }
+
   // Only NodeProperties should manipulate the type.
   Type* type() const { return type_; }
   void set_type(Type* type) { type_ = type; }
 
   // Only NodeMarkers should manipulate the marks on nodes.
   Mark mark() { return mark_; }
   void set_mark(Mark mark) { mark_ = mark; }
 
   inline bool has_inline_inputs() const {
     return InlineCountField::decode(bit_field_) != kOutlineMarker;
@@ skipping 255 matching lines @@
 }
 
 
 Node::Uses::const_iterator Node::Uses::end() const { return const_iterator(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_NODE_H_