libstdc++-v3/include/parallel/compatibility.h

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2007-2024 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
  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
 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 */