libatomic/host-config.h

   1 /* Copyright (C) 2012-2017 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