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

src/compiler/bytecode-graph-builder.h

 // Copyright 2015 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_BYTECODE_GRAPH_BUILDER_H_
 #define V8_COMPILER_BYTECODE_GRAPH_BUILDER_H_
 
 #include "src/compiler.h"
 #include "src/compiler/bytecode-branch-analysis.h"
 #include "src/compiler/js-graph.h"
@@ skipping 47 matching lines @@
   // Helper function for creating a pair containing type feedback vector and
   // a feedback slot.
   VectorSlotPair CreateVectorSlotPair(int slot_id);
 
   void set_environment(Environment* env) { environment_ = env; }
   const Environment* environment() const { return environment_; }
   Environment* environment() { return environment_; }
 
   // Node creation helpers
   Node* NewNode(const Operator* op, bool incomplete = false) {
-    return MakeNode(op, 0, static_cast<Node**>(NULL), incomplete);
+    return MakeNode(op, 0, static_cast<Node**>(nullptr), incomplete);
   }
 
   Node* NewNode(const Operator* op, Node* n1) {
     Node* buffer[] = {n1};
     return MakeNode(op, arraysize(buffer), buffer, false);
   }
 
   Node* NewNode(const Operator* op, Node* n1, Node* n2) {
     Node* buffer[] = {n1, n2};
     return MakeNode(op, arraysize(buffer), buffer, false);
@@ skipping 253 matching lines @@
   Node* accumulator_state_values_;
   int register_base_;
   int accumulator_base_;
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_BYTECODE_GRAPH_BUILDER_H_