diff --git a/src/hotspot/cpu/zero/abstractInterpreter_zero.cpp b/src/hotspot/cpu/zero/abstractInterpreter_zero.cpp
index d81a73b747f..bf0d13f02f8 100644
--- a/src/hotspot/cpu/zero/abstractInterpreter_zero.cpp
+++ b/src/hotspot/cpu/zero/abstractInterpreter_zero.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2007, 2008, 2009, 2010, 2011 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -103,13 +103,13 @@ void AbstractInterpreter::layout_activation(Method* method,
 
   BytecodeInterpreter::layout_interpreterState(istate,
                                                caller,
-                                               NULL,
+                                               nullptr,
                                                method,
                                                locals,
                                                stack,
                                                stack_base,
                                                monitor_base,
-                                               NULL,
+                                               nullptr,
                                                is_top_frame);
 }
 
diff --git a/src/hotspot/cpu/zero/bytecodeInterpreter_zero.cpp b/src/hotspot/cpu/zero/bytecodeInterpreter_zero.cpp
index de44d3afb58..3f02ff573fa 100644
--- a/src/hotspot/cpu/zero/bytecodeInterpreter_zero.cpp
+++ b/src/hotspot/cpu/zero/bytecodeInterpreter_zero.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2008 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -60,7 +60,7 @@ const char *BytecodeInterpreter::name_of_field_at_address(address addr) {
 #undef DO
   if (addr > (address) &_result && addr < (address) (&_result + 1))
     return "_result)";
-  return NULL;
+  return nullptr;
 }
 
 void BytecodeInterpreter::layout_interpreterState(interpreterState istate,
@@ -77,13 +77,13 @@ void BytecodeInterpreter::layout_interpreterState(interpreterState istate,
   istate->set_method(method);
   istate->set_mirror(method->method_holder()->java_mirror());
   istate->set_self_link(istate);
-  istate->set_prev_link(NULL);
+  istate->set_prev_link(nullptr);
   // thread will be set by a hacky repurposing of frame::patch_pc()
   // bcp will be set by vframeArrayElement::unpack_on_stack()
   istate->set_constants(method->constants()->cache());
   istate->set_msg(BytecodeInterpreter::method_resume);
   istate->set_bcp_advance(0);
-  istate->set_oop_temp(NULL);
+  istate->set_oop_temp(nullptr);
   if (caller->is_interpreted_frame()) {
     interpreterState prev = caller->get_interpreterState();
     prev->set_callee(method);
@@ -92,7 +92,7 @@ void BytecodeInterpreter::layout_interpreterState(interpreterState istate,
     else
       prev->set_bcp_advance(3);
   }
-  istate->set_callee(NULL);
+  istate->set_callee(nullptr);
   istate->set_monitor_base((BasicObjectLock *) monitor_base);
   istate->set_stack_base(stack_base);
   istate->set_stack(stack);
diff --git a/src/hotspot/cpu/zero/compiledIC_zero.cpp b/src/hotspot/cpu/zero/compiledIC_zero.cpp
index 5a3bfb028e3..b0564643af0 100644
--- a/src/hotspot/cpu/zero/compiledIC_zero.cpp
+++ b/src/hotspot/cpu/zero/compiledIC_zero.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -45,7 +45,7 @@
 
 address CompiledStaticCall::emit_to_interp_stub(CodeBuffer &cbuf, address mark) {
   ShouldNotReachHere(); // Only needed for COMPILER2.
-  return NULL;
+  return nullptr;
 }
 
 int CompiledStaticCall::to_interp_stub_size() {
diff --git a/src/hotspot/cpu/zero/continuationFreezeThaw_zero.inline.hpp b/src/hotspot/cpu/zero/continuationFreezeThaw_zero.inline.hpp
index 7de24a461c9..83f163d2bd5 100644
--- a/src/hotspot/cpu/zero/continuationFreezeThaw_zero.inline.hpp
+++ b/src/hotspot/cpu/zero/continuationFreezeThaw_zero.inline.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -80,7 +80,7 @@ inline void ThawBase::derelativize_interpreted_frame_metadata(const frame& hf, c
 
 inline intptr_t* ThawBase::align(const frame& hf, intptr_t* frame_sp, frame& caller, bool bottom) {
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 inline void ThawBase::patch_pd(frame& f, const frame& caller) {
diff --git a/src/hotspot/cpu/zero/continuationHelper_zero.inline.hpp b/src/hotspot/cpu/zero/continuationHelper_zero.inline.hpp
index 70a12473e0e..56da168d9b1 100644
--- a/src/hotspot/cpu/zero/continuationHelper_zero.inline.hpp
+++ b/src/hotspot/cpu/zero/continuationHelper_zero.inline.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2022, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -30,7 +30,7 @@
 template<typename FKind> // TODO: maybe do the same CRTP trick with Interpreted and Compiled as with hframe
 static inline intptr_t** link_address(const frame& f) {
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 inline int ContinuationHelper::frame_align_words(int size) {
@@ -40,7 +40,7 @@ inline int ContinuationHelper::frame_align_words(int size) {
 
 inline intptr_t* ContinuationHelper::frame_align_pointer(intptr_t* sp) {
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 template<typename FKind>
@@ -73,18 +73,18 @@ inline bool ContinuationHelper::Frame::assert_frame_laid_out(frame f) {
 
 inline intptr_t** ContinuationHelper::Frame::callee_link_address(const frame& f) {
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 template<typename FKind>
 static inline intptr_t* real_fp(const frame& f) {
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 inline address* ContinuationHelper::InterpretedFrame::return_pc_address(const frame& f) {
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 inline void ContinuationHelper::InterpretedFrame::patch_sender_sp(frame& f, const frame& caller) {
@@ -93,12 +93,12 @@ inline void ContinuationHelper::InterpretedFrame::patch_sender_sp(frame& f, cons
 
 inline address* ContinuationHelper::Frame::return_pc_address(const frame& f) {
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 inline address ContinuationHelper::Frame::real_pc(const frame& f) {
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 inline void ContinuationHelper::Frame::patch_pc(const frame& f, address pc) {
@@ -107,22 +107,22 @@ inline void ContinuationHelper::Frame::patch_pc(const frame& f, address pc) {
 
 inline intptr_t* ContinuationHelper::InterpretedFrame::frame_top(const frame& f, InterpreterOopMap* mask) { // inclusive; this will be copied with the frame
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 inline intptr_t* ContinuationHelper::InterpretedFrame::frame_bottom(const frame& f) { // exclusive; this will not be copied with the frame
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 inline intptr_t* ContinuationHelper::InterpretedFrame::frame_top(const frame& f, int callee_argsize, bool callee_interpreted) {
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 inline intptr_t* ContinuationHelper::InterpretedFrame::callers_sp(const frame& f) {
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 #endif // CPU_ZERO_CONTINUATIONHELPER_ZERO_INLINE_HPP
diff --git a/src/hotspot/cpu/zero/disassembler_zero.hpp b/src/hotspot/cpu/zero/disassembler_zero.hpp
index 559eb62fb51..20739a040b2 100644
--- a/src/hotspot/cpu/zero/disassembler_zero.hpp
+++ b/src/hotspot/cpu/zero/disassembler_zero.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2007, 2010 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -39,7 +39,7 @@
   // the perfect job. In those cases, decode_instruction0 may kick in
   // and do it right.
   // If nothing had to be done, just return "here", otherwise return "here + instr_len(here)"
-  static address decode_instruction0(address here, outputStream* st, address virtual_begin = NULL) {
+  static address decode_instruction0(address here, outputStream* st, address virtual_begin = nullptr) {
     return here;
   }
 
diff --git a/src/hotspot/cpu/zero/frame_zero.cpp b/src/hotspot/cpu/zero/frame_zero.cpp
index 66766a4094a..70f19708a53 100644
--- a/src/hotspot/cpu/zero/frame_zero.cpp
+++ b/src/hotspot/cpu/zero/frame_zero.cpp
@@ -53,7 +53,7 @@ bool frame::is_fake_stub_frame() const {
 
 frame frame::sender_for_entry_frame(RegisterMap *map) const {
   assert(zeroframe()->is_entry_frame(), "wrong type of frame");
-  assert(map != NULL, "map must be set");
+  assert(map != nullptr, "map must be set");
   assert(!entry_frame_is_first(), "next Java fp must be non zero");
   assert(entry_frame_call_wrapper()->anchor()->last_Java_sp() == sender_sp(),
          "sender should be next Java frame");
@@ -88,14 +88,14 @@ BasicObjectLock* frame::interpreter_frame_monitor_end() const {
 }
 
 void frame::patch_pc(Thread* thread, address pc) {
-  if (pc != NULL) {
+  if (pc != nullptr) {
     assert(_cb == CodeCache::find_blob(pc), "unexpected pc");
     _pc = pc;
     _deopt_state = is_deoptimized;
   } else {
     // We borrow this call to set the thread pointer in the interpreter
     // state; the hook to set up deoptimized frames isn't supplied it.
-    assert(pc == NULL, "should be");
+    assert(pc == nullptr, "should be");
     get_interpreterState()->set_thread(JavaThread::cast(thread));
   }
 }
@@ -207,9 +207,9 @@ BasicType frame::interpreter_frame_result(oop* oop_result,
     }
     else {
       oop* obj_p = (oop *) tos_addr;
-      obj = (obj_p == NULL) ? (oop) NULL : *obj_p;
+      obj = (obj_p == nullptr) ? (oop) nullptr : *obj_p;
     }
-    assert(obj == NULL || Universe::heap()->is_in(obj), "sanity check");
+    assert(obj == nullptr || Universe::heap()->is_in(obj), "sanity check");
     *oop_result = obj;
     break;
 
@@ -338,7 +338,7 @@ void InterpreterFrame::identify_word(int   frame_index,
   // JNI stuff
   if (istate->method()->is_native() && addr < istate->stack_base()) {
     address hA = istate->method()->signature_handler();
-    if (hA != NULL) {
+    if (hA != nullptr) {
       if (hA != (address) InterpreterRuntime::slow_signature_handler) {
         InterpreterRuntime::SignatureHandler *handler =
           InterpreterRuntime::SignatureHandler::from_handlerAddr(hA);
diff --git a/src/hotspot/cpu/zero/frame_zero.inline.hpp b/src/hotspot/cpu/zero/frame_zero.inline.hpp
index 46131a13a72..1b504cfa666 100644
--- a/src/hotspot/cpu/zero/frame_zero.inline.hpp
+++ b/src/hotspot/cpu/zero/frame_zero.inline.hpp
@@ -31,16 +31,16 @@
 // Constructors
 
 inline frame::frame() {
-  _zeroframe = NULL;
-  _sp = NULL;
-  _pc = NULL;
-  _cb = NULL;
+  _zeroframe = nullptr;
+  _sp = nullptr;
+  _pc = nullptr;
+  _cb = nullptr;
   _deopt_state = unknown;
   _on_heap = false;
   DEBUG_ONLY(_frame_index = -1;)
 }
 
-inline address  frame::sender_pc()           const { ShouldNotCallThis(); return NULL; }
+inline address  frame::sender_pc()           const { ShouldNotCallThis(); return nullptr; }
 
 inline frame::frame(intptr_t* sp) {
   Unimplemented();
@@ -54,19 +54,19 @@ inline frame::frame(ZeroFrame* zf, intptr_t* sp) {
   switch (zeroframe()->type()) {
   case ZeroFrame::ENTRY_FRAME:
     _pc = StubRoutines::call_stub_return_pc();
-    _cb = NULL;
+    _cb = nullptr;
     _deopt_state = not_deoptimized;
     break;
 
   case ZeroFrame::INTERPRETER_FRAME:
-    _pc = NULL;
-    _cb = NULL;
+    _pc = nullptr;
+    _cb = nullptr;
     _deopt_state = not_deoptimized;
     break;
 
   case ZeroFrame::FAKE_STUB_FRAME:
-    _pc = NULL;
-    _cb = NULL;
+    _pc = nullptr;
+    _cb = nullptr;
     _deopt_state = not_deoptimized;
     break;
 
@@ -87,12 +87,12 @@ inline intptr_t* frame::real_fp() const {
 
 inline intptr_t* frame::link() const {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 inline intptr_t* frame::link_or_null() const {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 inline interpreterState frame::get_interpreterState() const {
@@ -121,7 +121,7 @@ inline oop* frame::interpreter_frame_mirror_addr() const {
 
 inline intptr_t* frame::interpreter_frame_mdp_addr() const {
   fatal("Should not call this: Zero never profiles");
-  return NULL; // silence compiler warnings
+  return nullptr; // silence compiler warnings
 }
 
 inline intptr_t* frame::interpreter_frame_tos_address() const {
@@ -143,7 +143,7 @@ inline intptr_t* frame::interpreter_frame_expression_stack() const {
 }
 
 // Return a unique id for this frame. The id must have a value where
-// we can distinguish identity and younger/older relationship. NULL
+// we can distinguish identity and younger/older relationship. null
 // represents an invalid (incomparable) frame.
 inline intptr_t* frame::id() const {
   return fp();
@@ -159,7 +159,7 @@ inline void frame::set_saved_oop_result(RegisterMap* map, oop obj) {
 
 inline oop frame::saved_oop_result(RegisterMap* map) const {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 inline bool frame::is_older(intptr_t* id) const {
@@ -169,7 +169,7 @@ inline bool frame::is_older(intptr_t* id) const {
 
 inline intptr_t* frame::entry_frame_argument_at(int offset) const {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 inline intptr_t* frame::unextended_sp() const {
@@ -178,7 +178,7 @@ inline intptr_t* frame::unextended_sp() const {
 
 inline const ImmutableOopMap* frame::get_oop_map() const {
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 inline int frame::compiled_frame_stack_argsize() const {
@@ -217,7 +217,7 @@ inline int frame::frame_size() const {
 
 inline address* frame::sender_pc_addr() const {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 //------------------------------------------------------------------------------
diff --git a/src/hotspot/cpu/zero/icBuffer_zero.cpp b/src/hotspot/cpu/zero/icBuffer_zero.cpp
index 64b273c908c..adde916a4c4 100644
--- a/src/hotspot/cpu/zero/icBuffer_zero.cpp
+++ b/src/hotspot/cpu/zero/icBuffer_zero.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2007 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -47,10 +47,10 @@ void InlineCacheBuffer::assemble_ic_buffer_code(address code_begin,
 address InlineCacheBuffer::ic_buffer_entry_point(address code_begin) {
   // NB ic_stub_code_size() must return the size of the code we generate
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 void* InlineCacheBuffer::ic_buffer_cached_value(address code_begin) {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
diff --git a/src/hotspot/cpu/zero/interpreterRT_zero.cpp b/src/hotspot/cpu/zero/interpreterRT_zero.cpp
index 59328afd731..5aeb5a0981d 100644
--- a/src/hotspot/cpu/zero/interpreterRT_zero.cpp
+++ b/src/hotspot/cpu/zero/interpreterRT_zero.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2007, 2008, 2010 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -62,7 +62,7 @@ void InterpreterRuntime::SignatureHandlerGeneratorBase::pass_object() {
 }
 
 void InterpreterRuntime::SignatureHandlerGeneratorBase::push(BasicType type) {
-  ffi_type *ftype = NULL;
+  ffi_type *ftype = nullptr;
   switch (type) {
   case T_VOID:
     ftype = &ffi_type_void;
diff --git a/src/hotspot/cpu/zero/javaFrameAnchor_zero.hpp b/src/hotspot/cpu/zero/javaFrameAnchor_zero.hpp
index cb92f1b97a4..89eb5ac23f1 100644
--- a/src/hotspot/cpu/zero/javaFrameAnchor_zero.hpp
+++ b/src/hotspot/cpu/zero/javaFrameAnchor_zero.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2007, 2008, 2010 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -35,15 +35,15 @@
   //  1 - initializing a new state (thread creation, javaCalls)
   //  2 - saving a current state (javaCalls)
   //  3 - restoring an old state (javaCalls)
-  // Note that whenever _last_Java_sp != NULL other anchor fields
+  // Note that whenever _last_Java_sp != null other anchor fields
   // must be valid.  The profiler apparently depends on this.
 
   void clear() {
     // clearing _last_Java_sp must be first
-    _last_Java_sp = NULL;
+    _last_Java_sp = nullptr;
     // fence?
-    _last_Java_fp = NULL;
-    _last_Java_pc = NULL;
+    _last_Java_fp = nullptr;
+    _last_Java_pc = nullptr;
   }
 
   void copy(JavaFrameAnchor* src) {
@@ -56,11 +56,11 @@
     // data
     //
     // Hack Alert: Temporary bugfix for 4717480/4721647 To act like
-    // previous version (pd_cache_state) don't NULL _last_Java_sp
+    // previous version (pd_cache_state) don't null _last_Java_sp
     // unless the value is changing
     //
     if (_last_Java_sp != sp)
-      _last_Java_sp = NULL;
+      _last_Java_sp = nullptr;
 
     _last_Java_fp = fp;
     _last_Java_pc = pc;
diff --git a/src/hotspot/cpu/zero/methodHandles_zero.cpp b/src/hotspot/cpu/zero/methodHandles_zero.cpp
index 3ec5081cba7..4021d0e74b6 100644
--- a/src/hotspot/cpu/zero/methodHandles_zero.cpp
+++ b/src/hotspot/cpu/zero/methodHandles_zero.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2009, 2010, 2011 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -84,7 +84,7 @@ void MethodHandles::setup_frame_anchor(JavaThread* thread) {
     frame = frame->next();
   }
 
-  assert(frame != NULL, "must be");
+  assert(frame != nullptr, "must be");
   thread->set_last_Java_frame(frame, sp);
 }
 
@@ -127,7 +127,7 @@ int MethodHandles::method_handle_entry_invokeBasic(Method* method, intptr_t UNUS
   int numArgs = method->size_of_parameters();
 
   oop recv = STACK_OBJECT(-numArgs);
-  if (recv == NULL) {
+  if (recv == nullptr) {
     throw_NPE(THREAD);
     return 0;
   }
@@ -172,7 +172,7 @@ int MethodHandles::method_handle_entry_linkToInterface(Method* method, intptr_t
 
   int numArgs = target->size_of_parameters();
   oop recv = STACK_OBJECT(-numArgs);
-  if (recv == NULL) {
+  if (recv == nullptr) {
     throw_NPE(THREAD);
     return 0;
   }
@@ -190,7 +190,7 @@ int MethodHandles::method_handle_entry_linkToInterface(Method* method, intptr_t
   // that the method no longer exists (got deleted) or is private.
   // Private class methods can never be an implementation of an
   // interface method. In those cases, throw AME.
-  if (vmtarget != NULL) {
+  if (vmtarget != nullptr) {
     invoke_target(vmtarget, THREAD);
   } else {
     throw_AME(recv->klass(), target, THREAD);
@@ -216,7 +216,7 @@ int MethodHandles::method_handle_entry_linkToVirtual(Method* method, intptr_t UN
 
   int numArgs = target->size_of_parameters();
   oop recv = STACK_OBJECT(-numArgs);
-  if (recv == NULL) {
+  if (recv == nullptr) {
     throw_NPE(THREAD);
     return 0;
   }
@@ -258,7 +258,7 @@ address MethodHandles::generate_method_handle_interpreter_entry(MacroAssembler*
     return ZeroInterpreterGenerator::generate_entry_impl(masm, (address) MethodHandles::method_handle_entry_linkToVirtual);
   default:
     ShouldNotReachHere();
-    return NULL;
+    return nullptr;
   }
 }
 
diff --git a/src/hotspot/cpu/zero/nativeInst_zero.hpp b/src/hotspot/cpu/zero/nativeInst_zero.hpp
index 9cafe5ca700..5b2c9743cf9 100644
--- a/src/hotspot/cpu/zero/nativeInst_zero.hpp
+++ b/src/hotspot/cpu/zero/nativeInst_zero.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2007 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -61,7 +61,7 @@ class NativeInstruction {
 
 inline NativeInstruction* nativeInstruction_at(address address) {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 class NativeCall : public NativeInstruction {
@@ -72,22 +72,22 @@ class NativeCall : public NativeInstruction {
 
   address instruction_address() const {
     ShouldNotCallThis();
-    return NULL;
+    return nullptr;
   }
 
   address next_instruction_address() const {
     ShouldNotCallThis();
-    return NULL;
+    return nullptr;
   }
 
   address return_address() const {
     ShouldNotCallThis();
-    return NULL;
+    return nullptr;
   }
 
   address destination() const {
     ShouldNotCallThis();
-    return NULL;
+    return nullptr;
   }
 
   void set_destination_mt_safe(address dest) {
@@ -110,19 +110,19 @@ class NativeCall : public NativeInstruction {
 
 inline NativeCall* nativeCall_before(address return_address) {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 inline NativeCall* nativeCall_at(address address) {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 class NativeMovConstReg : public NativeInstruction {
  public:
   address next_instruction_address() const {
     ShouldNotCallThis();
-    return NULL;
+    return nullptr;
   }
 
   intptr_t data() const {
@@ -137,7 +137,7 @@ class NativeMovConstReg : public NativeInstruction {
 
 inline NativeMovConstReg* nativeMovConstReg_at(address address) {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 class NativeMovRegMem : public NativeInstruction {
@@ -158,7 +158,7 @@ class NativeMovRegMem : public NativeInstruction {
 
 inline NativeMovRegMem* nativeMovRegMem_at(address address) {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 class NativeJump : public NativeInstruction {
@@ -169,7 +169,7 @@ class NativeJump : public NativeInstruction {
 
   address jump_destination() const {
     ShouldNotCallThis();
-    return NULL;
+    return nullptr;
   }
 
   void set_jump_destination(address dest) {
@@ -187,14 +187,14 @@ class NativeJump : public NativeInstruction {
 
 inline NativeJump* nativeJump_at(address address) {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 class NativeGeneralJump : public NativeInstruction {
  public:
   address jump_destination() const {
     ShouldNotCallThis();
-    return NULL;
+    return nullptr;
   }
 
   static void insert_unconditional(address code_pos, address entry) {
@@ -208,7 +208,7 @@ class NativeGeneralJump : public NativeInstruction {
 
 inline NativeGeneralJump* nativeGeneralJump_at(address address) {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 class NativePostCallNop: public NativeInstruction {
@@ -221,13 +221,13 @@ public:
 
 inline NativePostCallNop* nativePostCallNop_at(address address) {
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 class NativeDeoptInstruction: public NativeInstruction {
 public:
-  address instruction_address() const       { Unimplemented(); return NULL; }
-  address next_instruction_address() const  { Unimplemented(); return NULL; }
+  address instruction_address() const       { Unimplemented(); return nullptr; }
+  address next_instruction_address() const  { Unimplemented(); return nullptr; }
 
   void  verify() { Unimplemented(); }
 
diff --git a/src/hotspot/cpu/zero/registerMap_zero.hpp b/src/hotspot/cpu/zero/registerMap_zero.hpp
index d8c5809543d..0715a96f5ee 100644
--- a/src/hotspot/cpu/zero/registerMap_zero.hpp
+++ b/src/hotspot/cpu/zero/registerMap_zero.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -31,8 +31,8 @@
  private:
   // This is the hook for finding a register in an "well-known" location,
   // such as a register block of a predetermined format.
-  // Since there is none, we just return NULL.
-  address pd_location(VMReg reg) const { return NULL; }
+  // Since there is none, we just return null.
+  address pd_location(VMReg reg) const { return nullptr; }
 
   address pd_location(VMReg base_reg, int slot_idx) const {
     return location(base_reg->next(slot_idx), nullptr);
diff --git a/src/hotspot/cpu/zero/register_zero.cpp b/src/hotspot/cpu/zero/register_zero.cpp
index 5d695430171..812119b66af 100644
--- a/src/hotspot/cpu/zero/register_zero.cpp
+++ b/src/hotspot/cpu/zero/register_zero.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2007 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -32,10 +32,10 @@ const int ConcreteRegisterImpl::max_fpr =
 
 const char* RegisterImpl::name() const {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 const char* FloatRegisterImpl::name() const {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
diff --git a/src/hotspot/cpu/zero/relocInfo_zero.cpp b/src/hotspot/cpu/zero/relocInfo_zero.cpp
index e908f796136..1e9fdc1081d 100644
--- a/src/hotspot/cpu/zero/relocInfo_zero.cpp
+++ b/src/hotspot/cpu/zero/relocInfo_zero.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2007, 2009, 2010, 2011 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -36,7 +36,7 @@ void Relocation::pd_set_data_value(address x, intptr_t o, bool verify_only) {
 
 address Relocation::pd_call_destination(address orig_addr) {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 void Relocation::pd_set_call_destination(address x) {
@@ -45,7 +45,7 @@ void Relocation::pd_set_call_destination(address x) {
 
 address Relocation::pd_get_address_from_code() {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 address* Relocation::pd_address_in_code() {
diff --git a/src/hotspot/cpu/zero/sharedRuntime_zero.cpp b/src/hotspot/cpu/zero/sharedRuntime_zero.cpp
index aec0e709d88..d55b7aead3f 100644
--- a/src/hotspot/cpu/zero/sharedRuntime_zero.cpp
+++ b/src/hotspot/cpu/zero/sharedRuntime_zero.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2007, 2008, 2009, 2010, 2011 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -74,7 +74,7 @@ nmethod *SharedRuntime::generate_native_wrapper(MacroAssembler *masm,
                                                 VMRegPair *regs,
                                                 BasicType ret_type) {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 int Deoptimization::last_frame_adjust(int callee_parameters,
diff --git a/src/hotspot/cpu/zero/smallRegisterMap_zero.inline.hpp b/src/hotspot/cpu/zero/smallRegisterMap_zero.inline.hpp
index 45f43228f10..b85ead32fd2 100644
--- a/src/hotspot/cpu/zero/smallRegisterMap_zero.inline.hpp
+++ b/src/hotspot/cpu/zero/smallRegisterMap_zero.inline.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -54,7 +54,7 @@ public:
 
   inline address location(VMReg reg, intptr_t* sp) const {
     Unimplemented();
-    return NULL;
+    return nullptr;
   }
 
   inline void set_location(VMReg reg, address loc) { assert_is_rfp(reg); }
@@ -77,7 +77,7 @@ public:
   bool should_skip_missing() const  { return false; }
   VMReg find_register_spilled_here(void* p, intptr_t* sp) {
     Unimplemented();
-    return NULL;
+    return nullptr;
   }
   void print() const { print_on(tty); }
   void print_on(outputStream* st) const { st->print_cr("Small register map"); }
diff --git a/src/hotspot/cpu/zero/stackChunkFrameStream_zero.inline.hpp b/src/hotspot/cpu/zero/stackChunkFrameStream_zero.inline.hpp
index d9f16caca1e..84d6dee9149 100644
--- a/src/hotspot/cpu/zero/stackChunkFrameStream_zero.inline.hpp
+++ b/src/hotspot/cpu/zero/stackChunkFrameStream_zero.inline.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -46,25 +46,25 @@ inline frame StackChunkFrameStream<frame_kind>::to_frame() const {
 template <ChunkFrames frame_kind>
 inline address StackChunkFrameStream<frame_kind>::get_pc() const {
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 template <ChunkFrames frame_kind>
 inline intptr_t* StackChunkFrameStream<frame_kind>::fp() const {
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 template <ChunkFrames frame_kind>
 inline intptr_t* StackChunkFrameStream<frame_kind>::derelativize(int offset) const {
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 template <ChunkFrames frame_kind>
 inline intptr_t* StackChunkFrameStream<frame_kind>::unextended_sp_for_interpreter_frame() const {
   Unimplemented();
-  return NULL;
+  return nullptr;
 }
 
 template <ChunkFrames frame_kind>
diff --git a/src/hotspot/cpu/zero/stack_zero.cpp b/src/hotspot/cpu/zero/stack_zero.cpp
index 275853a6032..ef986111cf8 100644
--- a/src/hotspot/cpu/zero/stack_zero.cpp
+++ b/src/hotspot/cpu/zero/stack_zero.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2010 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -33,7 +33,7 @@
 
 // Inlined causes circular inclusion with thread.hpp
 ZeroStack::ZeroStack()
-    : _base(NULL), _top(NULL), _sp(NULL) {
+    : _base(nullptr), _top(nullptr), _sp(nullptr) {
     _shadow_pages_size = StackOverflow::stack_shadow_zone_size();
   }
 
@@ -64,7 +64,7 @@ void ZeroStack::handle_overflow(TRAPS) {
       frame = frame->next();
     }
 
-    if (frame == NULL)
+    if (frame == nullptr)
       fatal("unrecoverable stack overflow");
 
     thread->set_last_Java_frame(frame, sp);
diff --git a/src/hotspot/cpu/zero/stack_zero.hpp b/src/hotspot/cpu/zero/stack_zero.hpp
index b5742b6a381..3d87ef1a6d2 100644
--- a/src/hotspot/cpu/zero/stack_zero.hpp
+++ b/src/hotspot/cpu/zero/stack_zero.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2008, 2009, 2010 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -42,7 +42,7 @@ class ZeroStack {
   ZeroStack();
 
   bool needs_setup() const {
-    return _base == NULL;
+    return _base == nullptr;
   }
 
   int suggest_size(Thread *thread) const;
@@ -59,9 +59,9 @@ class ZeroStack {
     assert(!needs_setup(), "not set up");
     assert(_sp == _top, "stuff on stack at teardown");
 
-    _base = NULL;
-    _top  = NULL;
-    _sp   = NULL;
+    _base = nullptr;
+    _top  = nullptr;
+    _sp   = nullptr;
   }
 
   intptr_t *sp() const {
diff --git a/src/hotspot/cpu/zero/stubGenerator_zero.cpp b/src/hotspot/cpu/zero/stubGenerator_zero.cpp
index 4fe19588133..f9b48127527 100644
--- a/src/hotspot/cpu/zero/stubGenerator_zero.cpp
+++ b/src/hotspot/cpu/zero/stubGenerator_zero.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2007, 2008, 2010, 2015 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -145,8 +145,8 @@ class StubGenerator: public StubCodeGenerator {
     StubRoutines::_checkcast_arraycopy       = ShouldNotCallThisStub();
     StubRoutines::_generic_arraycopy         = ShouldNotCallThisStub();
 
-    // Shared code tests for "NULL" to discover the stub is not generated.
-    StubRoutines::_unsafe_arraycopy          = NULL;
+    // Shared code tests for "null" to discover the stub is not generated.
+    StubRoutines::_unsafe_arraycopy          = nullptr;
 
     // We don't generate specialized code for HeapWord-aligned source
     // arrays, so just use the code we've already generated
diff --git a/src/hotspot/cpu/zero/vtableStubs_zero.cpp b/src/hotspot/cpu/zero/vtableStubs_zero.cpp
index dccbbb2c344..6258762279e 100644
--- a/src/hotspot/cpu/zero/vtableStubs_zero.cpp
+++ b/src/hotspot/cpu/zero/vtableStubs_zero.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2007 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -29,12 +29,12 @@
 
 VtableStub* VtableStubs::create_vtable_stub(int vtable_index) {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 VtableStub* VtableStubs::create_itable_stub(int vtable_index) {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 int VtableStub::pd_code_alignment() {
diff --git a/src/hotspot/cpu/zero/zeroInterpreter_zero.cpp b/src/hotspot/cpu/zero/zeroInterpreter_zero.cpp
index e8f8b8e38b9..a195a076091 100644
--- a/src/hotspot/cpu/zero/zeroInterpreter_zero.cpp
+++ b/src/hotspot/cpu/zero/zeroInterpreter_zero.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2007, 2008, 2009, 2010, 2011 Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -50,12 +50,12 @@
 #include "stack_zero.inline.hpp"
 
 void ZeroInterpreter::initialize_stub() {
-  if (_code != NULL) return;
+  if (_code != nullptr) return;
 
   // generate interpreter
   int code_size = InterpreterCodeSize;
   NOT_PRODUCT(code_size *= 4;)  // debug uses extra interpreter code space
-  _code = new StubQueue(new InterpreterCodeletInterface, code_size, NULL,
+  _code = new StubQueue(new InterpreterCodeletInterface, code_size, nullptr,
                          "Interpreter");
 }
 
@@ -120,8 +120,8 @@ int ZeroInterpreter::Reference_get_entry(Method* method, intptr_t UNUSED, TRAPS)
 
   oop ref = STACK_OBJECT(0);
 
-  // Shortcut if reference is known NULL
-  if (ref == NULL) {
+  // Shortcut if reference is known null
+  if (ref == nullptr) {
     return normal_entry(method, 0, THREAD);
   }
 
@@ -174,7 +174,7 @@ void ZeroInterpreter::main_loop(int recurse, TRAPS) {
   interpreterState istate = frame->interpreter_state();
   Method* method = istate->method();
 
-  intptr_t *result = NULL;
+  intptr_t *result = nullptr;
   int result_slots = 0;
 
   while (true) {
@@ -254,7 +254,7 @@ void ZeroInterpreter::main_loop(int recurse, TRAPS) {
       istate->set_stack_base(istate->stack_base() - monitor_words);
 
       // Zero the new monitor so the interpreter can find it.
-      ((BasicObjectLock *) istate->stack_base())->set_obj(NULL);
+      ((BasicObjectLock *) istate->stack_base())->set_obj(nullptr);
 
       // Resume the interpreter
       istate->set_msg(BytecodeInterpreter::got_monitors);
@@ -327,7 +327,7 @@ int ZeroInterpreter::native_entry(Method* method, intptr_t UNUSED, TRAPS) {
 
   // Lock if necessary
   BasicObjectLock *monitor;
-  monitor = NULL;
+  monitor = nullptr;
   if (method->is_synchronized()) {
     monitor = (BasicObjectLock*) istate->stack_base();
     oop lockee = monitor->obj();
@@ -338,7 +338,7 @@ int ZeroInterpreter::native_entry(Method* method, intptr_t UNUSED, TRAPS) {
     if (call_vm || lockee->cas_set_mark(markWord::from_pointer(monitor), disp) != disp) {
       // Is it simple recursive case?
       if (!call_vm && thread->is_lock_owned((address) disp.clear_lock_bits().to_pointer())) {
-        monitor->lock()->set_displaced_header(markWord::from_pointer(NULL));
+        monitor->lock()->set_displaced_header(markWord::from_pointer(nullptr));
       } else {
         inc_monitor_count = false;
         CALL_VM_NOCHECK(InterpreterRuntime::monitorenter(thread, monitor));
@@ -354,17 +354,17 @@ int ZeroInterpreter::native_entry(Method* method, intptr_t UNUSED, TRAPS) {
   // Get the signature handler
   InterpreterRuntime::SignatureHandler *handler; {
     address handlerAddr = method->signature_handler();
-    if (handlerAddr == NULL) {
+    if (handlerAddr == nullptr) {
       CALL_VM_NOCHECK(InterpreterRuntime::prepare_native_call(thread, method));
       if (HAS_PENDING_EXCEPTION)
         goto unlock_unwind_and_return;
 
       handlerAddr = method->signature_handler();
-      assert(handlerAddr != NULL, "eh?");
+      assert(handlerAddr != nullptr, "eh?");
     }
     if (handlerAddr == (address) InterpreterRuntime::slow_signature_handler) {
       CALL_VM_NOCHECK(handlerAddr =
-        InterpreterRuntime::slow_signature_handler(thread, method, NULL,NULL));
+        InterpreterRuntime::slow_signature_handler(thread, method, nullptr,nullptr));
       if (HAS_PENDING_EXCEPTION)
         goto unlock_unwind_and_return;
     }
@@ -375,7 +375,7 @@ int ZeroInterpreter::native_entry(Method* method, intptr_t UNUSED, TRAPS) {
   // Get the native function entry point
   address function;
   function = method->native_function();
-  assert(function != NULL, "should be set if signature handler is");
+  assert(function != nullptr, "should be set if signature handler is");
 
   // Build the argument list
   stack->overflow_check(handler->argument_count() * 2, THREAD);
@@ -465,7 +465,7 @@ int ZeroInterpreter::native_entry(Method* method, intptr_t UNUSED, TRAPS) {
   // we release the handle it might be protected by.
   if (handler->result_type() == &ffi_type_pointer) {
     if (result[0] == 0) {
-      istate->set_oop_temp(NULL);
+      istate->set_oop_temp(nullptr);
     } else {
       jobject handle = reinterpret_cast<jobject>(result[0]);
       istate->set_oop_temp(JNIHandles::resolve(handle));
@@ -482,10 +482,10 @@ int ZeroInterpreter::native_entry(Method* method, intptr_t UNUSED, TRAPS) {
     BasicLock *lock = monitor->lock();
     markWord header = lock->displaced_header();
     oop rcvr = monitor->obj();
-    monitor->set_obj(NULL);
+    monitor->set_obj(nullptr);
 
     bool dec_monitor_count = true;
-    if (header.to_pointer() != NULL) {
+    if (header.to_pointer() != nullptr) {
       markWord old_header = markWord::encode(lock);
       if (rcvr->cas_set_mark(header, old_header) != old_header) {
         monitor->set_obj(rcvr);
@@ -616,7 +616,7 @@ int ZeroInterpreter::getter_entry(Method* method, intptr_t UNUSED, TRAPS) {
   // Load the object pointer and drop into the slow path
   // if we have a NullPointerException
   oop object = STACK_OBJECT(0);
-  if (object == NULL) {
+  if (object == nullptr) {
     return normal_entry(method, 0, THREAD);
   }
 
@@ -706,7 +706,7 @@ int ZeroInterpreter::setter_entry(Method* method, intptr_t UNUSED, TRAPS) {
 
   // Figure out where the receiver is. If there is a long/double
   // operand on stack top, then receiver is two slots down.
-  oop object = NULL;
+  oop object = nullptr;
   switch (entry->flag_state()) {
     case ltos:
     case dtos:
@@ -719,7 +719,7 @@ int ZeroInterpreter::setter_entry(Method* method, intptr_t UNUSED, TRAPS) {
 
   // Load the receiver pointer and drop into the slow path
   // if we have a NullPointerException
-  if (object == NULL) {
+  if (object == nullptr) {
     return normal_entry(method, 0, THREAD);
   }
 
@@ -825,13 +825,13 @@ InterpreterFrame *InterpreterFrame::build(Method* const method, TRAPS) {
   istate->set_method(method);
   istate->set_mirror(method->method_holder()->java_mirror());
   istate->set_self_link(istate);
-  istate->set_prev_link(NULL);
+  istate->set_prev_link(nullptr);
   istate->set_thread(thread);
-  istate->set_bcp(method->is_native() ? NULL : method->code_base());
+  istate->set_bcp(method->is_native() ? nullptr : method->code_base());
   istate->set_constants(method->constants()->cache());
   istate->set_msg(BytecodeInterpreter::method_entry);
-  istate->set_oop_temp(NULL);
-  istate->set_callee(NULL);
+  istate->set_oop_temp(nullptr);
+  istate->set_callee(nullptr);
 
   istate->set_monitor_base((BasicObjectLock *) stack->sp());
   if (method->is_synchronized()) {
@@ -872,7 +872,7 @@ InterpreterFrame *InterpreterFrame::build(int size, TRAPS) {
   interpreterState istate =
     (interpreterState) stack->alloc(sizeof(BytecodeInterpreter));
   assert(fp - stack->sp() == istate_off, "should be");
-  istate->set_self_link(NULL); // mark invalid
+  istate->set_self_link(nullptr); // mark invalid
 
   stack->alloc((size_in_words - header_words) * wordSize);
 
@@ -881,11 +881,11 @@ InterpreterFrame *InterpreterFrame::build(int size, TRAPS) {
 
 address ZeroInterpreter::return_entry(TosState state, int length, Bytecodes::Code code) {
   ShouldNotCallThis();
-  return NULL;
+  return nullptr;
 }
 
 address ZeroInterpreter::deopt_entry(TosState state, int length) {
-  return NULL;
+  return nullptr;
 }
 
 address ZeroInterpreter::remove_activation_preserving_args_entry() {
@@ -895,7 +895,7 @@ address ZeroInterpreter::remove_activation_preserving_args_entry() {
 }
 
 address ZeroInterpreter::remove_activation_early_entry(TosState state) {
-  return NULL;
+  return nullptr;
 }
 
 // Helper for figuring out if frames are interpreter frames