| 1 | // boost/memory_order.hpp |
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| 2 | // |
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| 3 | // Defines enum boost::memory_order per the C++0x working draft |
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| 4 | // |
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| 5 | // Copyright (c) 2008, 2009 Peter Dimov |
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| 6 | // Copyright (c) 2018 Andrey Semashev |
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| 7 | // |
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| 8 | // Distributed under the Boost Software License, Version 1.0. |
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| 9 | // See accompanying file LICENSE_1_0.txt or copy at |
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| 10 | // http://www.boost.org/LICENSE_1_0.txt) |
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| 11 | |
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| 12 | #ifndef BOOST_MEMORY_ORDER_HPP_INCLUDED |
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| 13 | #define BOOST_MEMORY_ORDER_HPP_INCLUDED |
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| 14 | |
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| 15 | #include <boost/config.hpp> |
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| 16 | |
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| 17 | #if defined(BOOST_HAS_PRAGMA_ONCE) |
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| 18 | # pragma once |
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| 19 | #endif |
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| 20 | |
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| 21 | namespace boost |
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| 22 | { |
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| 23 | |
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| 24 | // |
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| 25 | // Enum values are chosen so that code that needs to insert |
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| 26 | // a trailing fence for acquire semantics can use a single |
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| 27 | // test such as: |
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| 28 | // |
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| 29 | // if( mo & memory_order_acquire ) { ...fence... } |
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| 30 | // |
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| 31 | // For leading fences one can use: |
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| 32 | // |
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| 33 | // if( mo & memory_order_release ) { ...fence... } |
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| 34 | // |
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| 35 | // Architectures such as Alpha that need a fence on consume |
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| 36 | // can use: |
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| 37 | // |
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| 38 | // if( mo & ( memory_order_acquire | memory_order_consume ) ) { ...fence... } |
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| 39 | // |
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| 40 | // The values are also in the order of increasing "strength" |
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| 41 | // of the fences so that success/failure orders can be checked |
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| 42 | // efficiently in compare_exchange methods. |
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| 43 | // |
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| 44 | |
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| 45 | #if !defined(BOOST_NO_CXX11_SCOPED_ENUMS) |
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| 46 | |
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| 47 | enum class memory_order : unsigned int |
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| 48 | { |
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| 49 | relaxed = 0, |
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| 50 | consume = 1, |
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| 51 | acquire = 2, |
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| 52 | release = 4, |
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| 53 | acq_rel = 6, // acquire | release |
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| 54 | seq_cst = 14 // acq_rel | 8 |
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| 55 | }; |
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| 56 | |
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| 57 | BOOST_INLINE_VARIABLE BOOST_CONSTEXPR_OR_CONST memory_order memory_order_relaxed = memory_order::relaxed; |
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| 58 | BOOST_INLINE_VARIABLE BOOST_CONSTEXPR_OR_CONST memory_order memory_order_consume = memory_order::consume; |
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| 59 | BOOST_INLINE_VARIABLE BOOST_CONSTEXPR_OR_CONST memory_order memory_order_acquire = memory_order::acquire; |
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| 60 | BOOST_INLINE_VARIABLE BOOST_CONSTEXPR_OR_CONST memory_order memory_order_release = memory_order::release; |
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| 61 | BOOST_INLINE_VARIABLE BOOST_CONSTEXPR_OR_CONST memory_order memory_order_acq_rel = memory_order::acq_rel; |
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| 62 | BOOST_INLINE_VARIABLE BOOST_CONSTEXPR_OR_CONST memory_order memory_order_seq_cst = memory_order::seq_cst; |
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| 63 | |
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| 64 | #undef BOOST_MEMORY_ORDER_INLINE_VARIABLE |
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| 65 | |
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| 66 | #else // !defined(BOOST_NO_CXX11_SCOPED_ENUMS) |
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| 67 | |
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| 68 | enum memory_order |
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| 69 | { |
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| 70 | memory_order_relaxed = 0, |
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| 71 | memory_order_consume = 1, |
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| 72 | memory_order_acquire = 2, |
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| 73 | memory_order_release = 4, |
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| 74 | memory_order_acq_rel = 6, // acquire | release |
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| 75 | memory_order_seq_cst = 14 // acq_rel | 8 |
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| 76 | }; |
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| 77 | |
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| 78 | #endif // !defined(BOOST_NO_CXX11_SCOPED_ENUMS) |
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| 79 | |
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| 80 | } // namespace boost |
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| 81 | |
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| 82 | #endif // #ifndef BOOST_MEMORY_ORDER_HPP_INCLUDED |
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| 83 | |
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