1  /* Copyright (C) 2012-2023 Free Software Foundation, Inc.
       2     Contributed by Richard Henderson <rth@redhat.com>.
       3  
       4     This file is part of the GNU Atomic Library (libatomic).
       5  
       6     Libatomic is free software; you can redistribute it and/or modify it
       7     under the terms of the GNU General Public License as published by
       8     the Free Software Foundation; either version 3 of the License, or
       9     (at your option) any later version.
      10  
      11     Libatomic is distributed in the hope that it will be useful, but WITHOUT ANY
      12     WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
      13     FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
      14     more details.
      15  
      16     Under Section 7 of GPL version 3, you are granted additional
      17     permissions described in the GCC Runtime Library Exception, version
      18     3.1, as published by the Free Software Foundation.
      19  
      20     You should have received a copy of the GNU General Public License and
      21     a copy of the GCC Runtime Library Exception along with this program;
      22     see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
      23     <http://www.gnu.org/licenses/>.  */
      24  
      25  /* Included after all more target-specific host-config.h.  */
      26  
      27  
      28  /* The target may have some OS specific way to implement compare-and-swap.  */
      29  #if !defined(atomic_compare_exchange_n) && SIZE(HAVE_ATOMIC_CAS)
      30  # define atomic_compare_exchange_n  __atomic_compare_exchange_n
      31  #endif
      32  #if !defined(atomic_compare_exchange_w) && WSIZE(HAVE_ATOMIC_CAS)
      33  # define atomic_compare_exchange_w  __atomic_compare_exchange_n
      34  #endif
      35  
      36  /* For some targets, it may be significantly faster to avoid all barriers
      37     if the user only wants relaxed memory order.  Sometimes we don't want
      38     the extra code bloat.  In all cases, use the input to avoid warnings.  */
      39  #if defined(WANT_SPECIALCASE_RELAXED) && !defined(__OPTIMIZE_SIZE__)
      40  # define maybe_specialcase_relaxed(x)	((x) == __ATOMIC_RELAXED)
      41  #else
      42  # define maybe_specialcase_relaxed(x)	((x) & 0)
      43  #endif
      44  
      45  /* Similar, but for targets for which the seq_cst model is sufficiently
      46     more expensive than the acq_rel model.  */
      47  #if defined(WANT_SPECIALCASE_ACQREL) && !defined(__OPTIMIZE_SIZE__)
      48  # define maybe_specialcase_acqrel(x)	((x) != __ATOMIC_SEQ_CST)
      49  #else
      50  # define maybe_specialcase_acqrel(x)	((x) & 0)
      51  #endif
      52  
      53  
      54  /* The target may have some OS specific way to emit barriers.  */
      55  #ifndef pre_post_barrier
      56  static inline void __attribute__((always_inline, artificial))
      57  pre_barrier(int model)
      58  {
      59    if (!maybe_specialcase_relaxed(model))
      60      {
      61        if (maybe_specialcase_acqrel(model))
      62          __atomic_thread_fence (__ATOMIC_ACQ_REL);
      63        else
      64          __atomic_thread_fence (__ATOMIC_SEQ_CST);
      65      }
      66  }
      67  static inline void __attribute__((always_inline, artificial))
      68  post_barrier(int model)
      69  {
      70    pre_barrier(model);
      71  }
      72  #define pre_post_barrier 1
      73  #endif /* pre_post_barrier */
      74  
      75  /* Similar, but assume that acq_rel is already handled via locks.  */
      76  #ifndef pre_post_seq_barrier
      77  static inline void __attribute__((always_inline, artificial))
      78  pre_seq_barrier(int model)
      79  {
      80  }
      81  static inline void __attribute__((always_inline, artificial))
      82  post_seq_barrier(int model)
      83  {
      84  }
      85  #define pre_post_seq_barrier 1
      86  #endif