2021-01-04 10:26:59 +01:00
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/* Copyright (C) 2012-2021 Free Software Foundation, Inc.
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2012-05-01 17:48:28 +02:00
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Contributed by Richard Henderson <rth@redhat.com>.
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This file is part of the GNU Atomic Library (libatomic).
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Libatomic is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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Libatomic is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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/* Included after all more target-specific host-config.h. */
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/* The target may have some OS specific way to implement compare-and-swap. */
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#if !defined(atomic_compare_exchange_n) && SIZE(HAVE_ATOMIC_CAS)
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# define atomic_compare_exchange_n __atomic_compare_exchange_n
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#endif
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#if !defined(atomic_compare_exchange_w) && WSIZE(HAVE_ATOMIC_CAS)
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# define atomic_compare_exchange_w __atomic_compare_exchange_n
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#endif
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/* For some targets, it may be significantly faster to avoid all barriers
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if the user only wants relaxed memory order. Sometimes we don't want
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the extra code bloat. In all cases, use the input to avoid warnings. */
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#if defined(WANT_SPECIALCASE_RELAXED) && !defined(__OPTIMIZE_SIZE__)
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# define maybe_specialcase_relaxed(x) ((x) == __ATOMIC_RELAXED)
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#else
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# define maybe_specialcase_relaxed(x) ((x) & 0)
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#endif
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/* Similar, but for targets for which the seq_cst model is sufficiently
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more expensive than the acq_rel model. */
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#if defined(WANT_SPECIALCASE_ACQREL) && !defined(__OPTIMIZE_SIZE__)
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# define maybe_specialcase_acqrel(x) ((x) != __ATOMIC_SEQ_CST)
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#else
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# define maybe_specialcase_acqrel(x) ((x) & 0)
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#endif
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/* The target may have some OS specific way to emit barriers. */
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#ifndef pre_post_barrier
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static inline void __attribute__((always_inline, artificial))
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pre_barrier(int model)
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{
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if (!maybe_specialcase_relaxed(model))
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{
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if (maybe_specialcase_acqrel(model))
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__atomic_thread_fence (__ATOMIC_ACQ_REL);
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else
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__atomic_thread_fence (__ATOMIC_SEQ_CST);
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}
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}
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static inline void __attribute__((always_inline, artificial))
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post_barrier(int model)
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{
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pre_barrier(model);
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}
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#define pre_post_barrier 1
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#endif /* pre_post_barrier */
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/* Similar, but assume that acq_rel is already handled via locks. */
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#ifndef pre_post_seq_barrier
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static inline void __attribute__((always_inline, artificial))
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pre_seq_barrier(int model)
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{
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}
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static inline void __attribute__((always_inline, artificial))
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post_seq_barrier(int model)
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{
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}
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#define pre_post_seq_barrier 1
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#endif
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