Additional minor cleanup regarding CallWrapper: Use the null object pattern.

src/x64/macro-assembler-x64.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 226 matching lines @@
   }
 
   // ---------------------------------------------------------------------------
   // JavaScript invokes
 
   // Invoke the JavaScript function code by either calling or jumping.
   void InvokeCode(Register code,
                   const ParameterCount& expected,
                   const ParameterCount& actual,
                   InvokeFlag flag,
-                  CallWrapper* call_wrapper = NULL);
+                  const CallWrapper& call_wrapper = NullCallWrapper());
 
   void InvokeCode(Handle<Code> code,
                   const ParameterCount& expected,
                   const ParameterCount& actual,
                   RelocInfo::Mode rmode,
                   InvokeFlag flag,
-                  CallWrapper* call_wrapper = NULL);
+                  const CallWrapper& call_wrapper = NullCallWrapper());
 
   // Invoke the JavaScript function in the given register. Changes the
   // current context to the context in the function before invoking.
   void InvokeFunction(Register function,
                       const ParameterCount& actual,
                       InvokeFlag flag,
-                      CallWrapper* call_wrapper = NULL);
+                      const CallWrapper& call_wrapper = NullCallWrapper());
 
   void InvokeFunction(JSFunction* function,
                       const ParameterCount& actual,
                       InvokeFlag flag,
-                      CallWrapper* call_wrapper = NULL);
+                      const CallWrapper& call_wrapper = NullCallWrapper());
 
   // Invoke specified builtin JavaScript function. Adds an entry to
   // the unresolved list if the name does not resolve.
   void InvokeBuiltin(Builtins::JavaScript id,
                      InvokeFlag flag,
-                     CallWrapper* call_wrapper = NULL);
+                     const CallWrapper& call_wrapper = NullCallWrapper());
 
   // Store the function for the given builtin in the target register.
   void GetBuiltinFunction(Register target, Builtins::JavaScript id);
 
   // Store the code object for the given builtin in the target register.
   void GetBuiltinEntry(Register target, Builtins::JavaScript id);
 
 
   // ---------------------------------------------------------------------------
   // Smi tagging, untagging and operations on tagged smis.
@@ skipping 836 matching lines @@
   Handle<Object> code_object_;
 
   // Helper functions for generating invokes.
   template <typename LabelType>
   void InvokePrologue(const ParameterCount& expected,
                       const ParameterCount& actual,
                       Handle<Code> code_constant,
                       Register code_register,
                       LabelType* done,
                       InvokeFlag flag,
-                      CallWrapper* call_wrapper);
+                      const CallWrapper& call_wrapper);
 
   // Activation support.
   void EnterFrame(StackFrame::Type type);
   void LeaveFrame(StackFrame::Type type);
 
   void EnterExitFramePrologue(bool save_rax);
 
   // Allocates arg_stack_space * kPointerSize memory (not GCed) on the stack
   // accessible via StackSpaceOperand.
   void EnterExitFrameEpilogue(int arg_stack_space, bool save_doubles);
@@ skipping 789 matching lines @@
 }
 
 
 template <typename LabelType>
 void MacroAssembler::InvokePrologue(const ParameterCount& expected,
                                     const ParameterCount& actual,
                                     Handle<Code> code_constant,
                                     Register code_register,
                                     LabelType* done,
                                     InvokeFlag flag,
-                                    CallWrapper* call_wrapper) {
+                                    const CallWrapper& call_wrapper) {
   bool definitely_matches = false;
   NearLabel invoke;
   if (expected.is_immediate()) {
     ASSERT(actual.is_immediate());
     if (expected.immediate() == actual.immediate()) {
       definitely_matches = true;
     } else {
       Set(rax, actual.immediate());
       if (expected.immediate() ==
               SharedFunctionInfo::kDontAdaptArgumentsSentinel) {
@@ skipping 28 matching lines @@
   if (!definitely_matches) {
     Handle<Code> adaptor = isolate()->builtins()->ArgumentsAdaptorTrampoline();
     if (!code_constant.is_null()) {
       movq(rdx, code_constant, RelocInfo::EMBEDDED_OBJECT);
       addq(rdx, Immediate(Code::kHeaderSize - kHeapObjectTag));
     } else if (!code_register.is(rdx)) {
       movq(rdx, code_register);
     }
 
     if (flag == CALL_FUNCTION) {
-      if (call_wrapper != NULL) call_wrapper->BeforeCall(CallSize(adaptor));
+      call_wrapper.BeforeCall(CallSize(adaptor));
       Call(adaptor, RelocInfo::CODE_TARGET);
-      if (call_wrapper != NULL) call_wrapper->AfterCall();
+      call_wrapper.AfterCall();
       jmp(done);
     } else {
       Jump(adaptor, RelocInfo::CODE_TARGET);
     }
     bind(&invoke);
   }
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_MACRO_ASSEMBLER_X64_H_