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3e6a2e37 | 1 | /* Copyright (C) 2012-2014 Free Software Foundation, Inc. |
48310492 RH |
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_EXCHANGE) | |
30 | UTYPE | |
31 | SIZE(libat_exchange) (UTYPE *mptr, UTYPE newval, int smodel) | |
32 | { | |
33 | if (maybe_specialcase_relaxed(smodel)) | |
34 | return __atomic_exchange_n (mptr, newval, __ATOMIC_RELAXED); | |
35 | else if (maybe_specialcase_acqrel(smodel)) | |
36 | return __atomic_exchange_n (mptr, newval, __ATOMIC_ACQ_REL); | |
37 | else | |
38 | return __atomic_exchange_n (mptr, newval, __ATOMIC_SEQ_CST); | |
39 | } | |
40 | ||
41 | #define DONE 1 | |
42 | #endif /* HAVE_ATOMIC_EXCHANGE */ | |
43 | ||
44 | ||
45 | #if !DONE && defined(atomic_compare_exchange_n) | |
46 | UTYPE | |
47 | SIZE(libat_exchange) (UTYPE *mptr, UTYPE newval, int smodel) | |
48 | { | |
49 | UTYPE oldval; | |
50 | ||
51 | pre_barrier (smodel); | |
52 | ||
53 | oldval = *mptr; | |
54 | while (!atomic_compare_exchange_n (mptr, &oldval, newval, true, | |
55 | __ATOMIC_RELAXED, __ATOMIC_RELAXED)) | |
56 | continue; | |
57 | ||
58 | post_barrier (smodel); | |
59 | ||
60 | return oldval; | |
61 | } | |
62 | ||
63 | #define DONE 1 | |
64 | #endif /* atomic_compare_exchange_n */ | |
65 | ||
66 | ||
67 | /* If this type is smaller than word-sized, fall back to a word-sized | |
68 | compare-and-swap loop. */ | |
69 | #if !DONE && N <= WORDSIZE && defined(atomic_compare_exchange_w) | |
70 | UTYPE | |
71 | SIZE(libat_exchange) (UTYPE *mptr, UTYPE newval, int smodel) | |
72 | { | |
73 | UWORD mask, shift, woldval, wnewval, t, *wptr; | |
74 | ||
75 | pre_barrier (smodel); | |
76 | ||
77 | if (N < WORDSIZE) | |
78 | { | |
79 | wptr = (UWORD *)((uintptr_t)mptr & -WORDSIZE); | |
80 | shift = (((uintptr_t)mptr % WORDSIZE) * CHAR_BIT) ^ SIZE(INVERT_MASK); | |
81 | mask = SIZE(MASK) << shift; | |
82 | } | |
83 | else | |
84 | { | |
85 | wptr = (UWORD *)mptr; | |
86 | shift = 0; | |
87 | mask = -1; | |
88 | } | |
89 | ||
90 | wnewval = (UWORD)newval << shift; | |
91 | woldval = __atomic_load_n (wptr, __ATOMIC_RELAXED); | |
92 | do | |
93 | { | |
94 | t = (woldval & ~mask) | wnewval; | |
95 | } | |
96 | while (!atomic_compare_exchange_w (wptr, &woldval, t, true, | |
97 | __ATOMIC_RELAXED, __ATOMIC_RELAXED)); | |
98 | ||
99 | post_barrier (smodel); | |
100 | return woldval >> shift; | |
101 | } | |
102 | ||
103 | #define DONE 1 | |
104 | #endif /* HAVE_ATOMIC_CAS && N < WORDSIZE */ | |
105 | ||
106 | ||
107 | /* Otherwise, fall back to some sort of protection mechanism. */ | |
108 | #if !DONE | |
109 | UTYPE | |
110 | SIZE(libat_exchange) (UTYPE *mptr, UTYPE newval, int smodel UNUSED) | |
111 | { | |
112 | UTYPE oldval; | |
113 | UWORD magic; | |
114 | ||
115 | pre_seq_barrier (smodel); | |
116 | magic = protect_start (mptr); | |
117 | ||
118 | oldval = *mptr; | |
119 | *mptr = newval; | |
120 | ||
121 | protect_end (mptr, magic); | |
122 | post_seq_barrier (smodel); | |
123 | ||
124 | return oldval; | |
125 | } | |
126 | #endif | |
127 | ||
128 | EXPORT_ALIAS (SIZE(exchange)); |