cpu/atmega_common: Add atomic_utils_arch.h

cpu/atmega_common/include/atomic_utils_arch.h

@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2020 Otto-von-Guericke-Universität Magdeburg
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser General
+ * Public License v2.1. See the file LICENSE in the top level directory for more
+ * details.
+ */
+
+/**
+ * @ingroup     cpu_atmega_common
+ *
+ * @{
+ *
+ * @file
+ * @brief       Implementation of fast atomic utility functions
+ * @author      Marian Buschsieweke <marian.buschsieweke@ovgu.de>
+ */
+
+#ifndef ATOMIC_UTILS_ARCH_H
+#define ATOMIC_UTILS_ARCH_H
+#ifndef DOXYGEN
+
+#include "periph_cpu.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* clang provides no built-in atomic access to regular variables */
+#ifndef __clang__
+
+#define HAS_ATOMIC_LOAD_U8
+static inline uint8_t atomic_load_u8(const uint8_t *var)
+{
+    return __atomic_load_1(var, __ATOMIC_SEQ_CST);
+}
+
+#define HAS_ATOMIC_STORE_U8
+static inline void atomic_store_u8(uint8_t *dest, uint8_t val)
+{
+    __atomic_store_1(dest, val, __ATOMIC_SEQ_CST);
+}
+
+#endif /* __clang__ */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* DOXYGEN */
+#endif /* ATOMIC_UTILS_ARCH_H */
+/** @} */