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1 /* Copyright (C) 2012-2018 Free Software Foundation, Inc.
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2 Contributed by Richard Henderson <rth@redhat.com>.
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3
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4 This file is part of the GNU Atomic Library (libatomic).
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5
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6 Libatomic is free software; you can redistribute it and/or modify it
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7 under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 3 of the License, or
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9 (at your option) any later version.
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10
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11 Libatomic is distributed in the hope that it will be useful, but WITHOUT ANY
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12 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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13 FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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14 more details.
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15
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16 Under Section 7 of GPL version 3, you are granted additional
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17 permissions described in the GCC Runtime Library Exception, version
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18 3.1, as published by the Free Software Foundation.
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19
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20 You should have received a copy of the GNU General Public License and
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21 a copy of the GCC Runtime Library Exception along with this program;
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22 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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23 <http://www.gnu.org/licenses/>. */
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24
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25 /* Included after all more target-specific host-config.h. */
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26
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27
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28 /* The target may have some OS specific way to implement compare-and-swap. */
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29 #if !defined(atomic_compare_exchange_n) && SIZE(HAVE_ATOMIC_CAS)
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30 # define atomic_compare_exchange_n __atomic_compare_exchange_n
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31 #endif
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32 #if !defined(atomic_compare_exchange_w) && WSIZE(HAVE_ATOMIC_CAS)
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33 # define atomic_compare_exchange_w __atomic_compare_exchange_n
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34 #endif
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35
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36 /* For some targets, it may be significantly faster to avoid all barriers
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37 if the user only wants relaxed memory order. Sometimes we don't want
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38 the extra code bloat. In all cases, use the input to avoid warnings. */
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39 #if defined(WANT_SPECIALCASE_RELAXED) && !defined(__OPTIMIZE_SIZE__)
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40 # define maybe_specialcase_relaxed(x) ((x) == __ATOMIC_RELAXED)
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41 #else
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42 # define maybe_specialcase_relaxed(x) ((x) & 0)
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43 #endif
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44
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45 /* Similar, but for targets for which the seq_cst model is sufficiently
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46 more expensive than the acq_rel model. */
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47 #if defined(WANT_SPECIALCASE_ACQREL) && !defined(__OPTIMIZE_SIZE__)
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48 # define maybe_specialcase_acqrel(x) ((x) != __ATOMIC_SEQ_CST)
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49 #else
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50 # define maybe_specialcase_acqrel(x) ((x) & 0)
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51 #endif
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52
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53
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54 /* The target may have some OS specific way to emit barriers. */
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55 #ifndef pre_post_barrier
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56 static inline void __attribute__((always_inline, artificial))
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57 pre_barrier(int model)
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58 {
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59 if (!maybe_specialcase_relaxed(model))
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60 {
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61 if (maybe_specialcase_acqrel(model))
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62 __atomic_thread_fence (__ATOMIC_ACQ_REL);
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63 else
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64 __atomic_thread_fence (__ATOMIC_SEQ_CST);
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65 }
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66 }
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67 static inline void __attribute__((always_inline, artificial))
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68 post_barrier(int model)
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69 {
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70 pre_barrier(model);
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71 }
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72 #define pre_post_barrier 1
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73 #endif /* pre_post_barrier */
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74
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75 /* Similar, but assume that acq_rel is already handled via locks. */
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76 #ifndef pre_post_seq_barrier
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77 static inline void __attribute__((always_inline, artificial))
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78 pre_seq_barrier(int model)
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79 {
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80 }
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81 static inline void __attribute__((always_inline, artificial))
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82 post_seq_barrier(int model)
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83 {
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84 }
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85 #define pre_post_seq_barrier 1
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86 #endif
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