]>
Commit | Line | Data |
---|---|---|
b32b8144 FG |
1 | /* |
2 | * Distributed under the Boost Software License, Version 1.0. | |
3 | * (See accompanying file LICENSE_1_0.txt or copy at | |
4 | * http://www.boost.org/LICENSE_1_0.txt) | |
5 | * | |
6 | * Copyright (c) 2009 Helge Bahmann | |
7 | * Copyright (c) 2013 Tim Blechmann | |
8 | * Copyright (c) 2014 Andrey Semashev | |
9 | */ | |
10 | /*! | |
11 | * \file atomic/detail/ops_gcc_ppc_common.hpp | |
12 | * | |
13 | * This header contains basic utilities for gcc PowerPC backend. | |
14 | */ | |
15 | ||
16 | #ifndef BOOST_ATOMIC_DETAIL_OPS_GCC_PPC_COMMON_HPP_INCLUDED_ | |
17 | #define BOOST_ATOMIC_DETAIL_OPS_GCC_PPC_COMMON_HPP_INCLUDED_ | |
18 | ||
19 | #include <boost/memory_order.hpp> | |
20 | #include <boost/atomic/detail/config.hpp> | |
21 | ||
22 | #ifdef BOOST_HAS_PRAGMA_ONCE | |
23 | #pragma once | |
24 | #endif | |
25 | ||
26 | namespace boost { | |
27 | namespace atomics { | |
28 | namespace detail { | |
29 | ||
30 | // The implementation below uses information from this document: | |
31 | // http://www.rdrop.com/users/paulmck/scalability/paper/N2745r.2010.02.19a.html | |
32 | ||
33 | // A note about memory_order_consume. Technically, this architecture allows to avoid | |
34 | // unnecessary memory barrier after consume load since it supports data dependency ordering. | |
35 | // However, some compiler optimizations may break a seemingly valid code relying on data | |
36 | // dependency tracking by injecting bogus branches to aid out of order execution. | |
37 | // This may happen not only in Boost.Atomic code but also in user's code, which we have no | |
38 | // control of. See this thread: http://lists.boost.org/Archives/boost/2014/06/213890.php. | |
39 | // For this reason we promote memory_order_consume to memory_order_acquire. | |
40 | ||
41 | struct gcc_ppc_operations_base | |
42 | { | |
11fdf7f2 | 43 | static BOOST_CONSTEXPR_OR_CONST bool full_cas_based = false; |
b32b8144 FG |
44 | static BOOST_CONSTEXPR_OR_CONST bool is_always_lock_free = true; |
45 | ||
46 | static BOOST_FORCEINLINE void fence_before(memory_order order) BOOST_NOEXCEPT | |
47 | { | |
48 | #if defined(__powerpc64__) || defined(__PPC64__) | |
49 | if (order == memory_order_seq_cst) | |
50 | __asm__ __volatile__ ("sync" ::: "memory"); | |
11fdf7f2 | 51 | else if ((static_cast< unsigned int >(order) & static_cast< unsigned int >(memory_order_release)) != 0u) |
b32b8144 FG |
52 | __asm__ __volatile__ ("lwsync" ::: "memory"); |
53 | #else | |
11fdf7f2 | 54 | if ((static_cast< unsigned int >(order) & static_cast< unsigned int >(memory_order_release)) != 0u) |
b32b8144 FG |
55 | __asm__ __volatile__ ("sync" ::: "memory"); |
56 | #endif | |
57 | } | |
58 | ||
59 | static BOOST_FORCEINLINE void fence_after(memory_order order) BOOST_NOEXCEPT | |
60 | { | |
11fdf7f2 | 61 | if ((static_cast< unsigned int >(order) & (static_cast< unsigned int >(memory_order_consume) | static_cast< unsigned int >(memory_order_acquire))) != 0u) |
b32b8144 FG |
62 | __asm__ __volatile__ ("isync" ::: "memory"); |
63 | } | |
64 | }; | |
65 | ||
66 | } // namespace detail | |
67 | } // namespace atomics | |
68 | } // namespace boost | |
69 | ||
70 | #endif // BOOST_ATOMIC_DETAIL_OPS_GCC_PPC_COMMON_HPP_INCLUDED_ |