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+//
+// detail/gcc_arm_fenced_block.hpp
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2018 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#ifndef ASIO_DETAIL_GCC_ARM_FENCED_BLOCK_HPP
+#define ASIO_DETAIL_GCC_ARM_FENCED_BLOCK_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include "asio/detail/config.hpp"
+
+#if defined(__GNUC__) && defined(__arm__)
+
+#include "asio/detail/noncopyable.hpp"
+
+#include "asio/detail/push_options.hpp"
+
+namespace asio {
+namespace detail {
+
+class gcc_arm_fenced_block
+ : private noncopyable
+{
+public:
+ enum half_t { half };
+ enum full_t { full };
+
+ // Constructor for a half fenced block.
+ explicit gcc_arm_fenced_block(half_t)
+ {
+ }
+
+ // Constructor for a full fenced block.
+ explicit gcc_arm_fenced_block(full_t)
+ {
+ barrier();
+ }
+
+ // Destructor.
+ ~gcc_arm_fenced_block()
+ {
+ barrier();
+ }
+
+private:
+ static void barrier()
+ {
+#if defined(__ARM_ARCH_4__) \
+ || defined(__ARM_ARCH_4T__) \
+ || defined(__ARM_ARCH_5__) \
+ || defined(__ARM_ARCH_5E__) \
+ || defined(__ARM_ARCH_5T__) \
+ || defined(__ARM_ARCH_5TE__) \
+ || defined(__ARM_ARCH_5TEJ__) \
+ || defined(__ARM_ARCH_6__) \
+ || defined(__ARM_ARCH_6J__) \
+ || defined(__ARM_ARCH_6K__) \
+ || defined(__ARM_ARCH_6Z__) \
+ || defined(__ARM_ARCH_6ZK__) \
+ || defined(__ARM_ARCH_6T2__)
+# if defined(__thumb__)
+ // This is just a placeholder and almost certainly not sufficient.
+ __asm__ __volatile__ ("" : : : "memory");
+# else // defined(__thumb__)
+ int a = 0, b = 0;
+ __asm__ __volatile__ ("swp %0, %1, [%2]"
+ : "=&r"(a) : "r"(1), "r"(&b) : "memory", "cc");
+# endif // defined(__thumb__)
+#else
+ // ARMv7 and later.
+ __asm__ __volatile__ ("dmb" : : : "memory");
+#endif
+ }
+};
+
+} // namespace detail
+} // namespace asio
+
+#include "asio/detail/pop_options.hpp"
+
+#endif // defined(__GNUC__) && defined(__arm__)
+
+#endif // ASIO_DETAIL_GCC_ARM_FENCED_BLOCK_HPP