From 319e21e9b48b4a9646c803e23d16f0b7df827d3f Mon Sep 17 00:00:00 2001
From: Axel Boldt-Christmas <aboldtch@openjdk.org>
Date: Mon, 26 Jan 2026 13:44:06 +0000
Subject: [PATCH] 8374677: ZGC: Convert zArray to use Atomic<T>

Reviewed-by: stefank, tschatzl
---
 src/hotspot/share/gc/z/zArray.hpp        | 8 +++++---
 src/hotspot/share/gc/z/zArray.inline.hpp | 7 +++----
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/src/hotspot/share/gc/z/zArray.hpp b/src/hotspot/share/gc/z/zArray.hpp
index 2c2f8a5dbfb..d39def4096e 100644
--- a/src/hotspot/share/gc/z/zArray.hpp
+++ b/src/hotspot/share/gc/z/zArray.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2026, 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
@@ -26,7 +26,7 @@
 
 #include "cppstdlib/type_traits.hpp"
 #include "memory/allocation.hpp"
-#include "runtime/atomicAccess.hpp"
+#include "runtime/atomic.hpp"
 #include "runtime/os.hpp"
 #include "runtime/thread.hpp"
 #include "utilities/growableArray.hpp"
@@ -78,7 +78,9 @@ public:
 template <typename T, bool Parallel>
 class ZArrayIteratorImpl : public StackObj {
 private:
-  size_t         _next;
+  using NextType = std::conditional_t<Parallel, Atomic<size_t>, size_t>;
+
+  NextType       _next;
   const size_t   _end;
   const T* const _array;
 
diff --git a/src/hotspot/share/gc/z/zArray.inline.hpp b/src/hotspot/share/gc/z/zArray.inline.hpp
index 9e2bc19118e..15caa54ebab 100644
--- a/src/hotspot/share/gc/z/zArray.inline.hpp
+++ b/src/hotspot/share/gc/z/zArray.inline.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2026, 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
@@ -27,7 +27,6 @@
 #include "gc/z/zArray.hpp"
 
 #include "gc/z/zLock.inline.hpp"
-#include "runtime/atomicAccess.hpp"
 
 template <typename T>
 ZArraySlice<T>::ZArraySlice(T* data, int len)
@@ -130,7 +129,7 @@ inline bool ZArrayIteratorImpl<T, Parallel>::next_serial(size_t* index) {
 
 template <typename T, bool Parallel>
 inline bool ZArrayIteratorImpl<T, Parallel>::next_parallel(size_t* index) {
-  const size_t claimed_index = AtomicAccess::fetch_then_add(&_next, 1u, memory_order_relaxed);
+  const size_t claimed_index = _next.fetch_then_add(1u, memory_order_relaxed);
 
   if (claimed_index < _end) {
     *index = claimed_index;
@@ -177,7 +176,7 @@ inline bool ZArrayIteratorImpl<T, Parallel>::next_if(T* elem, Function predicate
 
 template <typename T, bool Parallel>
 inline bool ZArrayIteratorImpl<T, Parallel>::next_index(size_t* index) {
-  if (Parallel) {
+  if constexpr (Parallel) {
     return next_parallel(index);
   } else {
     return next_serial(index);