1/* Copyright (C) 2012-2015 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#include "libatomic_i.h" 26 27 28/* If we support the builtin, just use it. */ 29#if !DONE && SIZE(HAVE_ATOMIC_LDST) 30void 31SIZE(libat_store) (UTYPE *mptr, UTYPE newval, int smodel) 32{ 33 if (maybe_specialcase_relaxed(smodel)) 34 __atomic_store_n (mptr, newval, __ATOMIC_RELAXED); 35 else if (maybe_specialcase_acqrel(smodel)) 36 /* Note that ACQ and ACQ_REL are not valid for store. */ 37 __atomic_store_n (mptr, newval, __ATOMIC_RELEASE); 38 else 39 __atomic_store_n (mptr, newval, __ATOMIC_SEQ_CST); 40} 41 42#define DONE 1 43#endif /* HAVE_ATOMIC_STORE */ 44 45/* If we have compare-and-swap, use it perform the store. */ 46#if !DONE && defined(atomic_compare_exchange_n) 47void 48SIZE(libat_store) (UTYPE *mptr, UTYPE newval, int smodel) 49{ 50 UTYPE oldval; 51 52 pre_barrier (smodel); 53 54 oldval = *mptr; 55 while (!atomic_compare_exchange_n (mptr, &oldval, newval, true, 56 __ATOMIC_RELAXED, __ATOMIC_RELAXED)) 57 continue; 58 59 post_barrier (smodel); 60} 61 62#define DONE 1 63#endif /* atomic_compare_exchange_n */ 64 65 66/* If this type is smaller than word-sized, fall back to a word-sized 67 compare-and-swap loop. */ 68#if !DONE && N < WORDSIZE && defined(atomic_compare_exchange_w) 69void 70SIZE(libat_store) (UTYPE *mptr, UTYPE newval, int smodel) 71{ 72 UWORD mask, shift, woldval, wnewval, t, *wptr; 73 74 pre_barrier (smodel); 75 76 wptr = (UWORD *)((uintptr_t)mptr & -WORDSIZE); 77 shift = (((uintptr_t)mptr % WORDSIZE) * CHAR_BIT) ^ SIZE(INVERT_MASK); 78 mask = SIZE(MASK) << shift; 79 80 wnewval = (UWORD)newval << shift; 81 woldval = __atomic_load_n (wptr, __ATOMIC_RELAXED); 82 do 83 { 84 t = (woldval & ~mask) | wnewval; 85 } 86 while (!atomic_compare_exchange_w (wptr, &woldval, t)); 87 88 post_barrier (smodel); 89} 90 91#define DONE 1 92#endif /* N < WORDSIZE && atomic_compare_exchange_w */ 93 94 95/* Otherwise, fall back to some sort of protection mechanism. */ 96#if !DONE 97void 98SIZE(libat_store) (UTYPE *mptr, UTYPE newval, int smodel) 99{ 100 UWORD magic; 101 102 pre_seq_barrier (smodel); 103 magic = protect_start (mptr); 104 105 *mptr = newval; 106 107 protect_end (mptr, magic); 108 post_seq_barrier (smodel); 109} 110#endif 111 112EXPORT_ALIAS (SIZE(store)); 113