1 // -*- C++ -*-
2 
3 // Copyright (C) 2007-2018 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 
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 /** @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
__add_omp(volatile _Tp * __ptr,_Tp __addend)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
__fetch_and_add(volatile _Tp * __ptr,_Tp __addend)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
__cas_omp(volatile _Tp * __ptr,_Tp __comparand,_Tp __replacement)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
__compare_and_swap(volatile _Tp * __ptr,_Tp __comparand,_Tp __replacement)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
__yield()121   __yield()
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 */
132