src/dawn/common/Atomic.h

// Copyright 2025 The Dawn & Tint Authors
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#ifndef SRC_DAWN_COMMON_ATOMIC_H_
#define SRC_DAWN_COMMON_ATOMIC_H_

#include <atomic>
#include <concepts>

namespace dawn {

// Equivalent to C++ stdlib's fetch_max that is only available in C++26 and beyond. This returns the
// value preceding the effects of this function.
template <typename T>
    requires std::totally_ordered<T>
T FetchMax(std::atomic<T>& t, T arg) {
    // Atomically set |t| to |arg| if |arg| > |t|.
    T current = t.load(std::memory_order::acquire);
    while (arg > current && t.compare_exchange_weak(current, arg, std::memory_order::acq_rel)) {
    }
    return current;
}

}  // namespace dawn

#endif  // SRC_DAWN_COMMON_RESULT_H_