libstdc++
parallel/compatibility.h
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1 // -*- C++ -*-
2 
3 // Copyright (C) 2007-2021 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the terms
7 // of the GNU General Public License as published by the Free Software
8 // Foundation; either version 3, or (at your option) any later
9 // version.
10 
11 // This library is distributed in the hope that it will be useful, but
12 // WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 // General Public License for 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 
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24 
25 /** @file parallel/compatibility.h
26  * @brief Compatibility layer, mostly concerned with atomic operations.
27  *
28  * This file is a GNU parallel extension to the Standard C++ Library
29  * and contains implementation details for the library's internal use.
30  */
31 
32 // Written by Felix Putze.
33 
34 #ifndef _GLIBCXX_PARALLEL_COMPATIBILITY_H
35 #define _GLIBCXX_PARALLEL_COMPATIBILITY_H 1
36 
37 #include <parallel/types.h>
38 #include <parallel/base.h>
39 
40 #if !defined(_WIN32) || defined (__CYGWIN__)
41 #include <sched.h>
42 #endif
43 
44 #ifdef __MINGW32__
45 // Including <windows.h> will drag in all the windows32 names. Since
46 // that can cause user code portability problems, we just declare the
47 // one needed function here.
48 extern "C"
49 __attribute((dllimport)) void __attribute__((stdcall)) Sleep (unsigned long);
50 #endif
51 
52 namespace __gnu_parallel
53 {
54  template<typename _Tp>
55  inline _Tp
56  __add_omp(volatile _Tp* __ptr, _Tp __addend)
57  {
58  int64_t __res;
59 #pragma omp critical
60  {
61  __res = *__ptr;
62  *(__ptr) += __addend;
63  }
64  return __res;
65  }
66 
67  /** @brief Add a value to a variable, atomically.
68  *
69  * @param __ptr Pointer to a signed integer.
70  * @param __addend Value to add.
71  */
72  template<typename _Tp>
73  inline _Tp
74  __fetch_and_add(volatile _Tp* __ptr, _Tp __addend)
75  {
76  if (__atomic_always_lock_free(sizeof(_Tp), __ptr))
77  return __atomic_fetch_add(__ptr, __addend, __ATOMIC_ACQ_REL);
78  return __add_omp(__ptr, __addend);
79  }
80 
81  template<typename _Tp>
82  inline bool
83  __cas_omp(volatile _Tp* __ptr, _Tp __comparand, _Tp __replacement)
84  {
85  bool __res = false;
86 #pragma omp critical
87  {
88  if (*__ptr == __comparand)
89  {
90  *__ptr = __replacement;
91  __res = true;
92  }
93  }
94  return __res;
95  }
96 
97  /** @brief Compare-and-swap
98  *
99  * Compare @c *__ptr and @c __comparand. If equal, let @c
100  * *__ptr=__replacement and return @c true, return @c false otherwise.
101  *
102  * @param __ptr Pointer to signed integer.
103  * @param __comparand Compare value.
104  * @param __replacement Replacement value.
105  */
106  template<typename _Tp>
107  inline bool
108  __compare_and_swap(volatile _Tp* __ptr, _Tp __comparand, _Tp __replacement)
109  {
110  if (__atomic_always_lock_free(sizeof(_Tp), __ptr))
111  return __atomic_compare_exchange_n(__ptr, &__comparand, __replacement,
112  false, __ATOMIC_ACQ_REL,
113  __ATOMIC_RELAXED);
114  return __cas_omp(__ptr, __comparand, __replacement);
115  }
116 
117  /** @brief Yield control to another thread, without waiting for
118  * the end of the time slice.
119  */
120  inline void
122  {
123 #if defined (_WIN32) && !defined (__CYGWIN__)
124  Sleep(0);
125 #else
126  sched_yield();
127 #endif
128  }
129 } // end namespace
130 
131 #endif /* _GLIBCXX_PARALLEL_COMPATIBILITY_H */
Sequential helper functions. This file is a GNU parallel extension to the Standard C++ Library.
Basic types and typedefs. This file is a GNU parallel extension to the Standard C++ Library.
GNU parallel code for public use.
_Tp __fetch_and_add(volatile _Tp *__ptr, _Tp __addend)
Add a value to a variable, atomically.
void __yield()
Yield control to another thread, without waiting for the end of the time slice.
bool __compare_and_swap(volatile _Tp *__ptr, _Tp __comparand, _Tp __replacement)
Compare-and-swap.