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

src/compiler/node-properties.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_PROPERTIES_H_
 #define V8_COMPILER_NODE_PROPERTIES_H_
 
 #include "src/compiler/node.h"
 #include "src/types.h"
 
@@ skipping 76 matching lines @@
   // merge node or expanding an existing merge node if necessary.
   static void MergeControlToEnd(Graph* graph, CommonOperatorBuilder* common,
                                 Node* node);
 
   // Replace all uses of {node} with the given replacement nodes. All occurring
   // use kinds need to be replaced, {NULL} is only valid if a use kind is
   // guaranteed not to exist.
   static void ReplaceUses(Node* node, Node* value, Node* effect = nullptr,
                           Node* success = nullptr, Node* exception = nullptr);
 
+  // Safe wrapper to mutate the operator of a node. Checks that the node is
+  // currently in a state that satisfies constraints of the new operator.
+  static void ChangeOp(Node* node, const Operator* new_op);
+
   // ---------------------------------------------------------------------------
   // Miscellaneous utilities.
 
   static Node* FindProjection(Node* node, size_t projection_index);
 
   // Collect the branch-related projections from a node, such as IfTrue,
   // IfFalse, IfSuccess, IfException, IfValue and IfDefault.
   //  - Branch: [ IfTrue, IfFalse ]
   //  - Call  : [ IfSuccess, IfException ]
   //  - Switch: [ IfValue, ..., IfDefault ]
@@ skipping 17 matching lines @@
 
  private:
   static inline bool IsInputRange(Edge edge, int first, int count);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_NODE_PROPERTIES_H_