8301497: Replace NULL with nullptr in cpu/s390

Reviewed-by: amitkumar, coleenp

Author: jdksjolen

src/hotspot/cpu/s390/abstractInterpreter_s390.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2016, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2016 SAP SE. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -121,17 +121,17 @@ int AbstractInterpreter::size_activation(int max_stack,
 //
 // Parameters:
 //
-// interpreter_frame != NULL:
+// interpreter_frame isn't null:
 //   set up the method, locals, and monitors.
-//   The frame interpreter_frame, if not NULL, is guaranteed to be the
+//   The frame interpreter_frame, if not null, is guaranteed to be the
 //   right size, as determined by a previous call to this method.
 //   It is also guaranteed to be walkable even though it is in a skeletal state
 //
-// is_top_frame == true:
+// is_top_frame is true:
 //   We're processing the *oldest* interpreter frame!
 //
 // pop_frame_extra_args:
-//   If this is != 0 we are returning to a deoptimized frame by popping
+//   If this isn't 0 we are returning to a deoptimized frame by popping
 //   off the callee frame. We want to re-execute the call that called the
 //   callee interpreted, but since the return to the interpreter would pop
 //   the arguments off advance the esp by dummy popframe_extra_args slots.

src/hotspot/cpu/s390/assembler_s390.hpp

@@ -137,7 +137,7 @@ class RelAddr {
     assert(((uint64_t)target & 0x0001L) == 0, "target of a relative address must be aligned");
     assert(((uint64_t)pc     & 0x0001L) == 0, "origin of a relative address must be aligned");
 
-    if ((target == NULL) || (target == pc)) {
+    if ((target == nullptr) || (target == pc)) {
       return 0;  // Yet unknown branch destination.
     } else {
       guarantee(is_in_range_of_RelAddr(target, pc, shortForm), "target not within reach");
@@ -295,7 +295,7 @@ class AddressLiteral {
 
  protected:
   // creation
-  AddressLiteral() : _address(NULL), _rspec() {}
+  AddressLiteral() : _address(nullptr), _rspec() {}
 
  public:
   AddressLiteral(address addr, RelocationHolder const& rspec)

src/hotspot/cpu/s390/c1_CodeStubs_s390.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2016, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2016, 2018 SAP SE. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -375,7 +375,7 @@ void PatchingStub::emit_code(LIR_Assembler* ce) {
 
   address entry = __ pc();
   NativeGeneralJump::insert_unconditional((address)_pc_start, entry);
-  address target = NULL;
+  address target = nullptr;
   relocInfo::relocType reloc_type = relocInfo::none;
   switch (_id) {
     case access_field_id:  target = Runtime1::entry_for (Runtime1::access_field_patching_id); break;