74 lines
2.7 KiB
C++
74 lines
2.7 KiB
C++
/*
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* Distributed under the Boost Software License, Version 1.0.
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* (See accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*
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* Copyright (c) 2009 Helge Bahmann
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* Copyright (c) 2013 Tim Blechmann
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* Copyright (c) 2014 Andrey Semashev
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*/
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/*!
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* \file atomic/detail/ops_gcc_ppc_common.hpp
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*
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* This header contains basic utilities for gcc PowerPC backend.
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*/
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#ifndef BOOST_ATOMIC_DETAIL_OPS_GCC_PPC_COMMON_HPP_INCLUDED_
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#define BOOST_ATOMIC_DETAIL_OPS_GCC_PPC_COMMON_HPP_INCLUDED_
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#include <boost/memory_order.hpp>
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#include <boost/atomic/detail/config.hpp>
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#include <boost/atomic/detail/header.hpp>
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#ifdef BOOST_HAS_PRAGMA_ONCE
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#pragma once
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#endif
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namespace boost {
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namespace atomics {
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namespace detail {
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// The implementation below uses information from this document:
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// http://www.rdrop.com/users/paulmck/scalability/paper/N2745r.2010.02.19a.html
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// A note about memory_order_consume. Technically, this architecture allows to avoid
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// unnecessary memory barrier after consume load since it supports data dependency ordering.
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// However, some compiler optimizations may break a seemingly valid code relying on data
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// dependency tracking by injecting bogus branches to aid out of order execution.
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// This may happen not only in Boost.Atomic code but also in user's code, which we have no
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// control of. See this thread: http://lists.boost.org/Archives/boost/2014/06/213890.php.
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// For this reason we promote memory_order_consume to memory_order_acquire.
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struct core_arch_operations_gcc_ppc_base
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{
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static BOOST_CONSTEXPR_OR_CONST bool full_cas_based = false;
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static BOOST_CONSTEXPR_OR_CONST bool is_always_lock_free = true;
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static BOOST_FORCEINLINE void fence_before(memory_order order) BOOST_NOEXCEPT
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{
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#if defined(__powerpc64__) || defined(__PPC64__)
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if (order == memory_order_seq_cst)
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__asm__ __volatile__ ("sync" ::: "memory");
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else if ((static_cast< unsigned int >(order) & static_cast< unsigned int >(memory_order_release)) != 0u)
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__asm__ __volatile__ ("lwsync" ::: "memory");
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#else
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if ((static_cast< unsigned int >(order) & static_cast< unsigned int >(memory_order_release)) != 0u)
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__asm__ __volatile__ ("sync" ::: "memory");
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#endif
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}
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static BOOST_FORCEINLINE void fence_after(memory_order order) BOOST_NOEXCEPT
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{
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if ((static_cast< unsigned int >(order) & (static_cast< unsigned int >(memory_order_consume) | static_cast< unsigned int >(memory_order_acquire))) != 0u)
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__asm__ __volatile__ ("isync" ::: "memory");
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}
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};
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} // namespace detail
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} // namespace atomics
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} // namespace boost
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#include <boost/atomic/detail/footer.hpp>
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#endif // BOOST_ATOMIC_DETAIL_OPS_GCC_PPC_COMMON_HPP_INCLUDED_
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