[libcxx-commits] [libcxx] [libc++] Implement P0493R5: Atomic minimum/maximum (PR #180333)

[A. Jiang via libcxx-commits]

================
@@ -377,6 +403,32 @@ struct atomic_ref<_Tp*> : public __atomic_ref_base<_Tp*> {
   _LIBCPP_HIDE_FROM_ABI _Tp* fetch_sub(ptrdiff_t __arg, memory_order __order = memory_order_seq_cst) const noexcept {
     return __atomic_fetch_sub(this->__ptr_, __arg * sizeof(_Tp), std::__to_gcc_order(__order));
   }
+#  if _LIBCPP_STD_VER >= 26
+  _LIBCPP_HIDE_FROM_ABI _Tp* fetch_max(_Tp* __arg, memory_order __order = memory_order_seq_cst) const noexcept {
+#    if __has_builtin(__atomic_fetch_max)
+    return __atomic_fetch_max(this->__ptr_, __arg * sizeof(_Tp), std::__to_gcc_order(__order));
+#    else
+    _Tp* __old = this->load(memory_order_relaxed);
+    _Tp* __new;
+    do {
+      __new = __old > __arg ? __old : __arg;
+    } while (!this->compare_exchange_weak(__old, __new, __order, memory_order_relaxed));
+    return __old;
+#    endif
+  }
+  _LIBCPP_HIDE_FROM_ABI _Tp* fetch_min(_Tp* __arg, memory_order __order = memory_order_seq_cst) const noexcept {
+#    if __has_builtin(__atomic_fetch_min)
+    return __atomic_fetch_min(this->__ptr_, __arg * sizeof(_Tp), std::__to_gcc_order(__order));
----------------
frederick-vs-ja wrote:

```suggestion
    return __atomic_fetch_min(this->__ptr_, __arg, std::__to_gcc_order(__order));
```

https://github.com/llvm/llvm-project/pull/180333