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1 /* Copyright (C) 2012-2018 Free Software Foundation, Inc.
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2 Contributed by Richard Henderson <rth@redhat.com>.
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3
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4 This file is part of the GNU Atomic Library (libatomic).
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5
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6 Libatomic is free software; you can redistribute it and/or modify it
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7 under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 3 of the License, or
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9 (at your option) any later version.
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10
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11 Libatomic is distributed in the hope that it will be useful, but WITHOUT ANY
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12 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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13 FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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14 more details.
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15
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16 Under Section 7 of GPL version 3, you are granted additional
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17 permissions described in the GCC Runtime Library Exception, version
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18 3.1, as published by the Free Software Foundation.
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19
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20 You should have received a copy of the GNU General Public License and
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21 a copy of the GCC Runtime Library Exception along with this program;
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22 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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23 <http://www.gnu.org/licenses/>. */
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24
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25 #include "libatomic_i.h"
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26
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27
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28 /* If we natively support the load, and if we're unconcerned with extra
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29 barriers (e.g. fully in-order cpu for which barriers are a nop), then
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30 go ahead and expand the operation inline. */
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31 #if !defined(WANT_SPECIALCASE_RELAXED) && !defined(__OPTIMIZE_SIZE__)
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32 # define EXACT_INLINE(N, DEST, SRC, DONE) \
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33 if (C2(HAVE_ATOMIC_LDST_,N)) \
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34 { \
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35 DEST = __atomic_load_n (SRC, __ATOMIC_SEQ_CST); \
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36 DONE; \
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37 }
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38 #else
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39 # define EXACT_INLINE(N, DEST, SRC, DONE)
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40 #endif
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41
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42
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43 #define EXACT_(N, DEST, SRC, DONE) \
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44 do { \
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45 EXACT_INLINE (N, DEST, SRC, DONE); \
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46 DEST = C3(local_,load_,N) (SRC, smodel); \
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47 DONE; \
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48 } while (0)
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49
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50 #define EXACT(N) \
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51 do { \
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52 if (!C2(HAVE_INT,N)) break; \
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53 if ((uintptr_t)mptr & (N - 1)) break; \
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54 EXACT_(N, *PTR(N,rptr), PTR(N,mptr), return); \
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55 } while (0)
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56
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57 #define LARGER(N) \
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58 do { \
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59 if (!C2(HAVE_INT,N)) break; \
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60 r = (uintptr_t)mptr & (N - 1); \
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61 a = (uintptr_t)mptr & -N; \
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62 if (r + n <= N) \
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63 EXACT_ (N, u.C2(i,N), PTR(N,a), goto Lfinish); \
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64 } while (0)
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65
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66
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67 void
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68 libat_load (size_t n, void *mptr, void *rptr, int smodel)
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69 {
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70 union max_size_u u;
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71 uintptr_t r, a;
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72
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73 switch (n)
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74 {
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75 case 0: return;
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76 case 1: EXACT(1); goto L4;
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77 case 2: EXACT(2); goto L4;
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78 case 4: EXACT(4); goto L8;
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79 case 8: EXACT(8); goto L16;
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80 case 16: EXACT(16); break;
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81
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82 case 3: L4: LARGER(4); /* FALLTHRU */
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83 case 5 ... 7: L8: LARGER(8); /* FALLTHRU */
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84 case 9 ... 15: L16: LARGER(16); break;
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85
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86 Lfinish:
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87 memcpy (rptr, u.b + r, n);
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88 return;
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89 }
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90
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91 pre_seq_barrier (smodel);
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92 libat_lock_n (mptr, n);
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93
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94 memcpy (rptr, mptr, n);
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95
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96 libat_unlock_n (mptr, n);
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97 post_seq_barrier (smodel);
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98 }
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99
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100 EXPORT_ALIAS (load);
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