libgomp/sections.c

   1 /* Copyright (C) 2005-2017 Free Software Foundation, Inc.
   2    Contributed by Richard Henderson <rth@redhat.com>.
   3
   4    This file is part of the GNU Offloading and Multi Processing Library
   5    (libgomp).
   6
   7    Libgomp is free software; you can redistribute it and/or modify it
   8    under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3, or (at your option)
  10    any later version.
  11
  12    Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
  13    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  14    FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  15    more details.
  16
  17    Under Section 7 of GPL version 3, you are granted additional
  18    permissions described in the GCC Runtime Library Exception, version
  19    3.1, as published by the Free Software Foundation.
  20
  21    You should have received a copy of the GNU General Public License and
  22    a copy of the GCC Runtime Library Exception along with this program;
  23    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  24    <http://www.gnu.org/licenses/>.  */
  25
  26 /* This file handles the SECTIONS construct.  */
  27
  28 #include "libgomp.h"
  29
  30
  31 /* Initialize the given work share construct from the given arguments.  */
  32
  33 static inline void
  34 gomp_sections_init (struct gomp_work_share *ws, unsigned count)
  35 {
  36   ws->sched = GFS_DYNAMIC;
  37   ws->chunk_size = 1;
  38   ws->end = count + 1L;
  39   ws->incr = 1;
  40   ws->next = 1;
  41 #ifdef HAVE_SYNC_BUILTINS
  42   /* Prepare things to make each iteration faster.  */
  43   if (sizeof (long) > sizeof (unsigned))
  44     ws->mode = 1;
  45   else
  46     {
  47       struct gomp_thread *thr = gomp_thread ();
  48       struct gomp_team *team = thr->ts.team;
  49       long nthreads = team ? team->nthreads : 1;
  50
  51       ws->mode = ((nthreads | ws->end)
  52                   < 1UL << (sizeof (long) * __CHAR_BIT__ / 2 - 1));
  53     }
  54 #else
  55   ws->mode = 0;
  56 #endif
  57 }
  58
  59 /* This routine is called when first encountering a sections construct
  60    that is not bound directly to a parallel construct.  The first thread
  61    that arrives will create the work-share construct; subsequent threads
  62    will see the construct exists and allocate work from it.
  63
  64    COUNT is the number of sections in this construct.
  65
  66    Returns the 1-based section number for this thread to perform, or 0 if
  67    all work was assigned to other threads prior to this thread's arrival.  */
  68
  69 unsigned
  70 GOMP_sections_start (unsigned count)
  71 {
  72   struct gomp_thread *thr = gomp_thread ();
  73   long s, e, ret;
  74
  75   if (gomp_work_share_start (false))
  76     {
  77       gomp_sections_init (thr->ts.work_share, count);
  78       gomp_work_share_init_done ();
  79     }
  80
  81 #ifdef HAVE_SYNC_BUILTINS
  82   if (gomp_iter_dynamic_next (&s, &e))
  83     ret = s;
  84   else
  85     ret = 0;
  86 #else
  87   gomp_mutex_lock (&thr->ts.work_share->lock);
  88   if (gomp_iter_dynamic_next_locked (&s, &e))
  89     ret = s;
  90   else
  91     ret = 0;
  92   gomp_mutex_unlock (&thr->ts.work_share->lock);
  93 #endif
  94
  95   return ret;
  96 }
  97
  98 /* This routine is called when the thread completes processing of the
  99    section currently assigned to it.  If the work-share construct is
 100    bound directly to a parallel construct, then the construct may have
 101    been set up before the parallel.  In which case, this may be the
 102    first iteration for the thread.
 103
 104    Returns the 1-based section number for this thread to perform, or 0 if
 105    all work was assigned to other threads prior to this thread's arrival.  */
 106
 107 unsigned
 108 GOMP_sections_next (void)
 109 {
 110   long s, e, ret;
 111
 112 #ifdef HAVE_SYNC_BUILTINS
 113   if (gomp_iter_dynamic_next (&s, &e))
 114     ret = s;
 115   else
 116     ret = 0;
 117 #else
 118   struct gomp_thread *thr = gomp_thread ();
 119
 120   gomp_mutex_lock (&thr->ts.work_share->lock);
 121   if (gomp_iter_dynamic_next_locked (&s, &e))
 122     ret = s;
 123   else
 124     ret = 0;
 125   gomp_mutex_unlock (&thr->ts.work_share->lock);
 126 #endif
 127
 128   return ret;
 129 }
 130
 131 /* This routine pre-initializes a work-share construct to avoid one
 132    synchronization once we get into the loop.  */
 133
 134 void
 135 GOMP_parallel_sections_start (void (*fn) (void *), void *data,
 136                               unsigned num_threads, unsigned count)
 137 {
 138   struct gomp_team *team;
 139
 140   num_threads = gomp_resolve_num_threads (num_threads, count);
 141   team = gomp_new_team (num_threads);
 142   gomp_sections_init (&team->work_shares[0], count);
 143   gomp_team_start (fn, data, num_threads, 0, team);
 144 }
 145
 146 ialias_redirect (GOMP_parallel_end)
 147
 148 void
 149 GOMP_parallel_sections (void (*fn) (void *), void *data,
 150                         unsigned num_threads, unsigned count, unsigned flags)
 151 {
 152   struct gomp_team *team;
 153
 154   num_threads = gomp_resolve_num_threads (num_threads, count);
 155   team = gomp_new_team (num_threads);
 156   gomp_sections_init (&team->work_shares[0], count);
 157   gomp_team_start (fn, data, num_threads, flags, team);
 158   fn (data);
 159   GOMP_parallel_end ();
 160 }
 161
 162 /* The GOMP_section_end* routines are called after the thread is told
 163    that all sections are complete.  The first two versions synchronize
 164    all threads; the nowait version does not.  */
 165
 166 void
 167 GOMP_sections_end (void)
 168 {
 169   gomp_work_share_end ();
 170 }
 171
 172 bool
 173 GOMP_sections_end_cancel (void)
 174 {
 175   return gomp_work_share_end_cancel ();
 176 }
 177
 178 void
 179 GOMP_sections_end_nowait (void)
 180 {
 181   gomp_work_share_end_nowait ();
 182 }