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/*
* 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)
*
* Copyright (c) 2009 Helge Bahmann
* Copyright (c) 2013 Tim Blechmann
* Copyright (c) 2014 Andrey Semashev
*/
/*!
* \file atomic/detail/ops_gcc_ppc_common.hpp
*
* This header contains basic utilities for gcc PowerPC backend.
*/
#ifndef BOOST_ATOMIC_DETAIL_OPS_GCC_PPC_COMMON_HPP_INCLUDED_
#define BOOST_ATOMIC_DETAIL_OPS_GCC_PPC_COMMON_HPP_INCLUDED_
#include <boost/memory_order.hpp>
#include <boost/atomic/detail/config.hpp>
#ifdef BOOST_HAS_PRAGMA_ONCE
#pragma once
#endif
namespace boost {
namespace atomics {
namespace detail {
// The implementation below uses information from this document:
// http://www.rdrop.com/users/paulmck/scalability/paper/N2745r.2010.02.19a.html
// A note about memory_order_consume. Technically, this architecture allows to avoid
// unnecessary memory barrier after consume load since it supports data dependency ordering.
// However, some compiler optimizations may break a seemingly valid code relying on data
// dependency tracking by injecting bogus branches to aid out of order execution.
// This may happen not only in Boost.Atomic code but also in user's code, which we have no
// control of. See this thread: http://lists.boost.org/Archives/boost/2014/06/213890.php.
// For this reason we promote memory_order_consume to memory_order_acquire.
struct gcc_ppc_operations_base
{
static BOOST_CONSTEXPR_OR_CONST bool is_always_lock_free = true;
static BOOST_FORCEINLINE void fence_before(memory_order order) BOOST_NOEXCEPT
{
#if defined(__powerpc64__) || defined(__PPC64__)
if (order == memory_order_seq_cst)
__asm__ __volatile__ ("sync" ::: "memory");
else if ((order & memory_order_release) != 0)
__asm__ __volatile__ ("lwsync" ::: "memory");
#else
if ((order & memory_order_release) != 0)
__asm__ __volatile__ ("sync" ::: "memory");
#endif
}
static BOOST_FORCEINLINE void fence_after(memory_order order) BOOST_NOEXCEPT
{
if ((order & (memory_order_consume | memory_order_acquire)) != 0)
__asm__ __volatile__ ("isync" ::: "memory");
}
};
} // namespace detail
} // namespace atomics
} // namespace boost
#endif // BOOST_ATOMIC_DETAIL_OPS_GCC_PPC_COMMON_HPP_INCLUDED_
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