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f1717362 | 1 | /* Copyright (C) 2012-2016 Free Software Foundation, Inc. |
6db1d2ca | 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 | #define EXACT(N) \ | |
29 | do { \ | |
30 | if (!C2(HAVE_INT,N)) break; \ | |
31 | if ((uintptr_t)ptr & (N - 1)) break; \ | |
32 | if (__atomic_always_lock_free(N, 0)) return true; \ | |
33 | if (C2(MAYBE_HAVE_ATOMIC_CAS_,N)) return true; \ | |
34 | } while (0) | |
35 | ||
36 | ||
37 | #define LARGER(N) \ | |
38 | do { \ | |
39 | uintptr_t r = (uintptr_t)ptr & (N - 1); \ | |
40 | if (!C2(HAVE_INT,N)) break; \ | |
41 | if (!C2(HAVE_ATOMIC_LDST_,N)) break; \ | |
42 | if (!C2(MAYBE_HAVE_ATOMIC_CAS_,N)) break; \ | |
43 | if (r + n <= N) return true; \ | |
44 | } while (0) | |
45 | ||
46 | ||
47 | bool | |
48 | libat_is_lock_free (size_t n, void *ptr) | |
49 | { | |
50 | switch (n) | |
51 | { | |
52 | case 0: return true; | |
53 | case 1: EXACT(1); goto L4; | |
54 | case 2: EXACT(2); goto L4; | |
55 | case 4: EXACT(4); goto L8; | |
56 | case 8: EXACT(8); goto L16; | |
57 | case 16: EXACT(16); break; | |
58 | ||
59 | case 3: L4: LARGER(4); /* FALLTHRU */ | |
60 | case 5 ... 7: L8: LARGER(8); /* FALLTHRU */ | |
61 | case 9 ... 15: L16: LARGER(16); break; | |
62 | } | |
63 | ||
64 | return false; | |
65 | } | |
66 | ||
67 | EXPORT_ALIAS (is_lock_free); |