1 /* Copyright (C) 2012-2021 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_TAS)
30 bool
SIZE(libat_test_and_set)31 SIZE(libat_test_and_set) (UTYPE *mptr, int smodel)
32 {
33 if (maybe_specialcase_relaxed(smodel))
34 return __atomic_test_and_set (mptr, __ATOMIC_RELAXED);
35 else if (maybe_specialcase_acqrel(smodel))
36 return __atomic_test_and_set (mptr, __ATOMIC_ACQ_REL);
37 else
38 return __atomic_test_and_set (mptr, __ATOMIC_SEQ_CST);
39 }
40
41 #define DONE 1
42 #endif /* HAVE_ATOMIC_TAS */
43
44
45 /* If this type is smaller than word-sized, fall back to a word-sized
46 compare-and-swap loop. */
47 #if !DONE && N <= WORDSIZE && defined(atomic_compare_exchange_w)
48 bool
SIZE(libat_test_and_set)49 SIZE(libat_test_and_set) (UTYPE *mptr, int smodel)
50 {
51 UWORD wval, woldval, shift, *wptr, t;
52
53 pre_barrier (smodel);
54
55 if (N < WORDSIZE)
56 {
57 wptr = (UWORD *)((uintptr_t)mptr & -WORDSIZE);
58 shift = SIZE(INVERT_MASK);
59 }
60 else
61 {
62 wptr = (UWORD *)mptr;
63 shift = 0;
64 }
65
66 wval = (UWORD)__GCC_ATOMIC_TEST_AND_SET_TRUEVAL << shift;
67 woldval = __atomic_load_n (wptr, __ATOMIC_RELAXED);
68 do
69 {
70 t = woldval | wval;
71 }
72 while (!atomic_compare_exchange_w (wptr, &woldval, t, true,
73 __ATOMIC_RELAXED, __ATOMIC_RELAXED));
74
75 post_barrier (smodel);
76 return woldval != 0;
77 }
78
79 #define DONE 1
80 #endif /* HAVE_ATOMIC_CAS && N < WORDSIZE */
81
82
83 /* Otherwise, fall back to some sort of protection mechanism. */
84 #if !DONE && N == 1
85 bool
SIZE(libat_test_and_set)86 SIZE(libat_test_and_set) (UTYPE *mptr, int smodel)
87 {
88 UTYPE oldval;
89 UWORD magic;
90
91 pre_seq_barrier (smodel);
92 magic = protect_start (mptr);
93
94 oldval = *mptr;
95 *mptr = __GCC_ATOMIC_TEST_AND_SET_TRUEVAL;
96
97 protect_end (mptr, magic);
98 post_seq_barrier (smodel);
99
100 return oldval != 0;
101 }
102
103 #define DONE 1
104 #endif /* N == 1 */
105
106
107 #if !DONE
108 bool
SIZE(libat_test_and_set)109 SIZE(libat_test_and_set) (UTYPE *mptr, int smodel UNUSED)
110 {
111 return libat_test_and_set_1 ((U_1 *)mptr, smodel);
112 }
113 #endif
114
115 EXPORT_ALIAS (SIZE(test_and_set));
116