diff --git a/src/hotspot/os_cpu/aix_ppc/javaThread_aix_ppc.cpp b/src/hotspot/os_cpu/aix_ppc/javaThread_aix_ppc.cpp
index 506a8197483..aeed103c4de 100644
--- a/src/hotspot/os_cpu/aix_ppc/javaThread_aix_ppc.cpp
+++ b/src/hotspot/os_cpu/aix_ppc/javaThread_aix_ppc.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2012, 2014 SAP SE. All rights reserved.
  * Copyright (c) 2022, IBM Corp.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
@@ -61,17 +61,17 @@ bool JavaThread::pd_get_top_frame_for_profiling(frame* fr_addr, void* ucontext,
     ucontext_t* uc = (ucontext_t*) ucontext;
     address pc = (address)uc->uc_mcontext.jmp_context.iar;
 
-    if (pc == NULL) {
+    if (pc == nullptr) {
       // ucontext wasn't useful
       return false;
     }
 
     frame ret_frame((intptr_t*)uc->uc_mcontext.jmp_context.gpr[1/*REG_SP*/], pc);
 
-    if (ret_frame.fp() == NULL) {
+    if (ret_frame.fp() == nullptr) {
       // The found frame does not have a valid frame pointer.
       // Bail out because this will create big trouble later on, either
-      //  - when using istate, calculated as (NULL - ijava_state_size) or
+      //  - when using istate, calculated as (nullptr - ijava_state_size) or
       //  - when using fp() directly in safe_for_sender()
       //
       // There is no conclusive description (yet) how this could happen, but it does.
diff --git a/src/hotspot/os_cpu/aix_ppc/os_aix_ppc.cpp b/src/hotspot/os_cpu/aix_ppc/os_aix_ppc.cpp
index 301b8a2e647..034dd6b8b8a 100644
--- a/src/hotspot/os_cpu/aix_ppc/os_aix_ppc.cpp
+++ b/src/hotspot/os_cpu/aix_ppc/os_aix_ppc.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2012, 2021 SAP SE. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -90,7 +90,7 @@ intptr_t* os::Aix::ucontext_get_sp(const ucontext_t * uc) {
 }
 
 intptr_t* os::Aix::ucontext_get_fp(const ucontext_t * uc) {
-  return NULL;
+  return nullptr;
 }
 
 void os::Posix::ucontext_set_pc(ucontext_t* uc, address new_pc) {
@@ -107,14 +107,14 @@ address os::fetch_frame_from_context(const void* ucVoid,
   address epc;
   const ucontext_t* uc = (const ucontext_t*)ucVoid;
 
-  if (uc != NULL) {
+  if (uc != nullptr) {
     epc = os::Posix::ucontext_get_pc(uc);
     if (ret_sp) *ret_sp = os::Aix::ucontext_get_sp(uc);
     if (ret_fp) *ret_fp = os::Aix::ucontext_get_fp(uc);
   } else {
-    epc = NULL;
-    if (ret_sp) *ret_sp = (intptr_t *)NULL;
-    if (ret_fp) *ret_fp = (intptr_t *)NULL;
+    epc = nullptr;
+    if (ret_sp) *ret_sp = (intptr_t *)nullptr;
+    if (ret_fp) *ret_fp = (intptr_t *)nullptr;
   }
 
   return epc;
@@ -141,9 +141,9 @@ frame os::fetch_compiled_frame_from_context(const void* ucVoid) {
 }
 
 frame os::get_sender_for_C_frame(frame* fr) {
-  if (*fr->sp() == NULL) {
+  if (*fr->sp() == nullptr) {
     // fr is the last C frame
-    return frame(NULL, NULL);
+    return frame(nullptr, nullptr);
   }
   return frame(fr->sender_sp(), fr->sender_pc());
 }
@@ -159,27 +159,27 @@ bool PosixSignals::pd_hotspot_signal_handler(int sig, siginfo_t* info,
                                              ucontext_t* uc, JavaThread* thread) {
 
   // Decide if this trap can be handled by a stub.
-  address stub = NULL;
+  address stub = nullptr;
 
   // retrieve program counter
-  address const pc = uc ? os::Posix::ucontext_get_pc(uc) : NULL;
+  address const pc = uc ? os::Posix::ucontext_get_pc(uc) : nullptr;
 
   // retrieve crash address
-  address const addr = info ? (const address) info->si_addr : NULL;
+  address const addr = info ? (const address) info->si_addr : nullptr;
 
-  if (info == NULL || uc == NULL) {
+  if (info == nullptr || uc == nullptr) {
     return false; // Fatal error
   }
 
   // If we are a java thread...
-  if (thread != NULL) {
+  if (thread != nullptr) {
 
     // Handle ALL stack overflow variations here
     if (sig == SIGSEGV && thread->is_in_full_stack(addr)) {
       // stack overflow
       if (os::Posix::handle_stack_overflow(thread, addr, pc, uc, &stub)) {
         return true; // continue
-      } else if (stub != NULL) {
+      } else if (stub != nullptr) {
         goto run_stub;
       } else {
         return false; // Fatal error
@@ -222,7 +222,7 @@ bool PosixSignals::pd_hotspot_signal_handler(int sig, siginfo_t* info,
       //     happens rarely.  In heap based and disjoint base compressd oop modes also loads
       //     are used for null checks.
 
-      CodeBlob *cb = NULL;
+      CodeBlob *cb = nullptr;
       int stop_type = -1;
       // Handle signal from NativeJump::patch_verified_entry().
       if (sig == SIGILL && nativeInstruction_at(pc)->is_sigill_not_entrant()) {
@@ -236,7 +236,7 @@ bool PosixSignals::pd_hotspot_signal_handler(int sig, siginfo_t* info,
       else if ((sig == USE_POLL_BIT_ONLY ? SIGTRAP : SIGSEGV) &&
                ((NativeInstruction*)pc)->is_safepoint_poll() &&
                CodeCache::contains((void*) pc) &&
-               ((cb = CodeCache::find_blob(pc)) != NULL) &&
+               ((cb = CodeCache::find_blob(pc)) != nullptr) &&
                cb->is_compiled()) {
         if (TraceTraps) {
           tty->print_cr("trap: safepoint_poll at " INTPTR_FORMAT " (%s)", p2i(pc),
@@ -249,7 +249,7 @@ bool PosixSignals::pd_hotspot_signal_handler(int sig, siginfo_t* info,
       else if (UseSIGTRAP && sig == SIGTRAP &&
                ((NativeInstruction*)pc)->is_safepoint_poll_return() &&
                CodeCache::contains((void*) pc) &&
-               ((cb = CodeCache::find_blob(pc)) != NULL) &&
+               ((cb = CodeCache::find_blob(pc)) != nullptr) &&
                cb->is_compiled()) {
         if (TraceTraps) {
           tty->print_cr("trap: safepoint_poll at return at " INTPTR_FORMAT " (nmethod)", p2i(pc));
@@ -313,7 +313,7 @@ bool PosixSignals::pd_hotspot_signal_handler(int sig, siginfo_t* info,
         bool msg_present = (stop_type & MacroAssembler::stop_msg_present);
         stop_type = (stop_type &~ MacroAssembler::stop_msg_present);
 
-        const char *msg = NULL;
+        const char *msg = nullptr;
         switch (stop_type) {
           case MacroAssembler::stop_stop              : msg = "stop"; break;
           case MacroAssembler::stop_untested          : msg = "untested"; break;
@@ -332,7 +332,7 @@ bool PosixSignals::pd_hotspot_signal_handler(int sig, siginfo_t* info,
         // End life with a fatal error, message and detail message and the context.
         // Note: no need to do any post-processing here (e.g. signal chaining)
         va_list va_dummy;
-        VMError::report_and_die(thread, uc, NULL, 0, msg, detail_msg, va_dummy);
+        VMError::report_and_die(thread, uc, nullptr, 0, msg, detail_msg, va_dummy);
         va_end(va_dummy);
 
         ShouldNotReachHere();
@@ -342,9 +342,9 @@ bool PosixSignals::pd_hotspot_signal_handler(int sig, siginfo_t* info,
         // BugId 4454115: A read from a MappedByteBuffer can fault here if the
         // underlying file has been truncated. Do not crash the VM in such a case.
         CodeBlob* cb = CodeCache::find_blob(pc);
-        CompiledMethod* nm = cb ? cb->as_compiled_method_or_null() : NULL;
+        CompiledMethod* nm = cb ? cb->as_compiled_method_or_null() : nullptr;
         bool is_unsafe_arraycopy = (thread->doing_unsafe_access() && UnsafeCopyMemory::contains_pc(pc));
-        if ((nm != NULL && nm->has_unsafe_access()) || is_unsafe_arraycopy) {
+        if ((nm != nullptr && nm->has_unsafe_access()) || is_unsafe_arraycopy) {
           address next_pc = pc + 4;
           if (is_unsafe_arraycopy) {
             next_pc = UnsafeCopyMemory::page_error_continue_pc(pc);
@@ -394,9 +394,9 @@ run_stub:
 
   // One of the above code blocks ininitalized the stub, so we want to
   // delegate control to that stub.
-  if (stub != NULL) {
+  if (stub != nullptr) {
     // Save all thread context in case we need to restore it.
-    if (thread != NULL) thread->set_saved_exception_pc(pc);
+    if (thread != nullptr) thread->set_saved_exception_pc(pc);
     os::Posix::ucontext_set_pc(uc, stub);
     return true;
   }
@@ -433,7 +433,7 @@ size_t os::Posix::default_stack_size(os::ThreadType thr_type) {
 // helper functions for fatal error handler
 
 void os::print_context(outputStream *st, const void *context) {
-  if (context == NULL) return;
+  if (context == nullptr) return;
 
   const ucontext_t* uc = (const ucontext_t*)context;
 
@@ -451,7 +451,7 @@ void os::print_context(outputStream *st, const void *context) {
 }
 
 void os::print_tos_pc(outputStream *st, const void *context) {
-  if (context == NULL) return;
+  if (context == nullptr) return;
 
   const ucontext_t* uc = (const ucontext_t*)context;
 
@@ -474,7 +474,7 @@ void os::print_tos_pc(outputStream *st, const void *context) {
 }
 
 void os::print_register_info(outputStream *st, const void *context) {
-  if (context == NULL) return;
+  if (context == nullptr) return;
 
   ucontext_t *uc = (ucontext_t*)context;