/usr/include/atomic_ops/sysdeps/acquire_release_volatile.h is in libatomic-ops-dev 7.2~alpha5+cvs20101124-1ubuntu1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 | /*
* Copyright (c) 2003 Hewlett-Packard Development Company, L.P.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
/*
* This file adds definitions appropriate for environments in which an AO_t
* volatile load has acquire semantics, and an AO_t volatile store has release
* semantics. This is arguably supposed to be true with the standard Itanium
* software conventions.
*/
/*
* Empirically gcc/ia64 does some reordering of ordinary operations around volatiles
* even when we think it shouldn't. Gcc 3.3 and earlier could reorder a volatile store
* with another store. As of March 2005, gcc pre-4 reused previously computed
* common subexpressions across a volatile load.
* Hence we now add compiler barriers for gcc.
*/
#if !defined(AO_GCC_BARRIER)
# if defined(__GNUC__)
# define AO_GCC_BARRIER() AO_compiler_barrier()
# else
# define AO_GCC_BARRIER()
# endif
#endif
AO_INLINE AO_t
AO_load_acquire(const volatile AO_t *p)
{
AO_t result = *p;
/* A normal volatile load generates an ld.acq */
AO_GCC_BARRIER();
return result;
}
#define AO_HAVE_load_acquire
AO_INLINE void
AO_store_release(volatile AO_t *p, AO_t val)
{
AO_GCC_BARRIER();
/* A normal volatile store generates an st.rel */
*p = val;
}
#define AO_HAVE_store_release
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