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

src/compiler/linkage.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/ast/scopes.h"
 #include "src/code-stubs.h"
 #include "src/compiler.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/frame.h"
 #include "src/compiler/linkage.h"
@@ skipping 102 matching lines @@
       more_this = false;
     }
     ++current_input;
     ++other_input;
   }
   return HasSameReturnLocationsAs(OpParameter<CallDescriptor const*>(node));
 }
 
 
 CallDescriptor* Linkage::ComputeIncoming(Zone* zone, CompilationInfo* info) {
-  if (info->code_stub() != NULL) {
+  if (info->code_stub() != nullptr) {
     // Use the code stub interface descriptor.
     CodeStub* stub = info->code_stub();
     CallInterfaceDescriptor descriptor = stub->GetCallInterfaceDescriptor();
     return GetStubCallDescriptor(
         info->isolate(), zone, descriptor, stub->GetStackParameterCount(),
         CallDescriptor::kNoFlags, Operator::kNoProperties);
   }
   if (info->has_literal()) {
     // If we already have the function literal, use the number of parameters
     // plus the receiver.
     return GetJSCallDescriptor(zone, info->is_osr(),
                                1 + info->literal()->parameter_count(),
                                CallDescriptor::kNoFlags);
   }
   if (!info->closure().is_null()) {
     // If we are compiling a JS function, use a JS call descriptor,
     // plus the receiver.
     SharedFunctionInfo* shared = info->closure()->shared();
     return GetJSCallDescriptor(zone, info->is_osr(),
                                1 + shared->internal_formal_parameter_count(),
                                CallDescriptor::kNoFlags);
   }
-  return NULL;  // TODO(titzer): ?
+  return nullptr;  // TODO(titzer): ?
 }
 
 
 // static
 int Linkage::FrameStateInputCount(Runtime::FunctionId function) {
   // Most runtime functions need a FrameState. A few chosen ones that we know
   // not to call into arbitrary JavaScript, not to throw, and not to deoptimize
   // are blacklisted here and can be called without a FrameState.
   switch (function) {
     case Runtime::kAllocateInTargetSpace:
@@ skipping 374 matching lines @@
   } else {
     DCHECK(loc == regloc(kContextRegister));
     return LinkageLocation::ForCalleeFrameSlot(Frame::kContextSlot);
   }
 }
 
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8