[turbofan] Nodes are killed by resetting all their inputs to zero.

src/compiler/node.cc

 // 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.
 
 #include "src/compiler/node.h"
 
 #include "src/compiler/generic-node-inl.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 void Node::Kill() {
   DCHECK_NOT_NULL(op());
   RemoveAllInputs();
   DCHECK(uses().empty());
-  set_op(NULL);
 }
 
 
 void Node::CollectProjections(NodeVector* projections) {
   for (size_t i = 0; i < projections->size(); i++) {
     (*projections)[i] = NULL;
   }
   for (UseIter i = uses().begin(); i != uses().end(); ++i) {
     if ((*i)->opcode() != IrOpcode::kProjection) continue;
     int32_t index = OpParameter<int32_t>(*i);
@@ skipping 28 matching lines @@
       os << n.InputAt(i)->id();
     }
     os << ")";
   }
   return os;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8