[turbofan] Build s/NULL/nullptr/g and CHECK(x != nullptr) to CHECK_NOT_NULL(x).

src/compiler/simplified-lowering.cc

 // 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.
 
 #include "src/compiler/simplified-lowering.h"
 
 #include <limits>
 
 #include "src/base/bits.h"
 #include "src/code-factory.h"
@@ skipping 310 matching lines @@
     TRACE("--{Propagation phase}--\n");
     phase_ = PROPAGATE;
     EnqueueInitial(jsgraph_->graph()->end());
     // Process nodes from the queue until it is empty.
     while (!queue_.empty()) {
       Node* node = queue_.front();
       NodeInfo* info = GetInfo(node);
       queue_.pop();
       info->set_queued(false);
       TRACE(" visit #%d: %s\n", node->id(), node->op()->mnemonic());
-      VisitNode(node, info->truncation(), NULL);
+      VisitNode(node, info->truncation(), nullptr);
       TRACE("  ==> output ");
       PrintInfo(info->output_type());
       TRACE("\n");
     }
 
     // Run lowering and change insertion phase.
     TRACE("--{Simplified lowering phase}--\n");
     phase_ = LOWER;
     // Process nodes from the collected {nodes_} vector.
     for (NodeVector::iterator i = nodes_.begin(); i != nodes_.end(); ++i) {
@@ skipping 1492 matching lines @@
   ReplaceEffectUses(node, comparison);
   node->ReplaceInput(0, comparison);
   node->ReplaceInput(1, jsgraph()->SmiConstant(EQUAL));
   node->TrimInputCount(2);
   NodeProperties::ChangeOp(node, machine()->IntLessThanOrEqual());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8