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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgomp/] [ordered.c] - Blame information for rev 834

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1 735 jeremybenn
/* Copyright (C) 2005, 2009 Free Software Foundation, Inc.
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   Contributed by Richard Henderson <rth@redhat.com>.
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   This file is part of the GNU OpenMP Library (libgomp).
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   Libgomp is free software; you can redistribute it and/or modify it
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   under the terms of the GNU General Public License as published by
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   the Free Software Foundation; either version 3, or (at your option)
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   any later version.
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   Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
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   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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   FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
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   more details.
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   Under Section 7 of GPL version 3, you are granted additional
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   permissions described in the GCC Runtime Library Exception, version
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   3.1, as published by the Free Software Foundation.
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   You should have received a copy of the GNU General Public License and
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   a copy of the GCC Runtime Library Exception along with this program;
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   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
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   <http://www.gnu.org/licenses/>.  */
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/* This file handles the ORDERED construct.  */
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#include "libgomp.h"
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/* This function is called when first allocating an iteration block.  That
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   is, the thread is not currently on the queue.  The work-share lock must
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   be held on entry.  */
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void
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gomp_ordered_first (void)
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{
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  struct gomp_thread *thr = gomp_thread ();
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  struct gomp_team *team = thr->ts.team;
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  struct gomp_work_share *ws = thr->ts.work_share;
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  unsigned index;
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  /* Work share constructs can be orphaned.  */
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  if (team == NULL || team->nthreads == 1)
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    return;
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  index = ws->ordered_cur + ws->ordered_num_used;
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  if (index >= team->nthreads)
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    index -= team->nthreads;
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  ws->ordered_team_ids[index] = thr->ts.team_id;
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  /* If this is the first and only thread in the queue, then there is
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     no one to release us when we get to our ordered section.  Post to
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     our own release queue now so that we won't block later.  */
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  if (ws->ordered_num_used++ == 0)
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    gomp_sem_post (team->ordered_release[thr->ts.team_id]);
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}
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/* This function is called when completing the last iteration block.  That
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   is, there are no more iterations to perform and so the thread should be
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   removed from the queue entirely.  Because of the way ORDERED blocks are
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   managed, it follows that we currently own access to the ORDERED block,
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   and should now pass it on to the next thread.  The work-share lock must
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   be held on entry.  */
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void
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gomp_ordered_last (void)
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{
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  struct gomp_thread *thr = gomp_thread ();
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  struct gomp_team *team = thr->ts.team;
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  struct gomp_work_share *ws = thr->ts.work_share;
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  unsigned next_id;
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  /* Work share constructs can be orphaned.  */
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  if (team == NULL || team->nthreads == 1)
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    return;
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  /* We're no longer the owner.  */
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  ws->ordered_owner = -1;
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  /* If we're not the last thread in the queue, then wake the next.  */
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  if (--ws->ordered_num_used > 0)
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    {
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      unsigned next = ws->ordered_cur + 1;
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      if (next == team->nthreads)
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        next = 0;
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      ws->ordered_cur = next;
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      next_id = ws->ordered_team_ids[next];
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      gomp_sem_post (team->ordered_release[next_id]);
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    }
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}
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/* This function is called when allocating a subsequent allocation block.
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   That is, we're done with the current iteration block and we're allocating
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   another.  This is the logical combination of a call to gomp_ordered_last
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   followed by a call to gomp_ordered_first.  The work-share lock must be
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   held on entry. */
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void
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gomp_ordered_next (void)
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{
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  struct gomp_thread *thr = gomp_thread ();
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  struct gomp_team *team = thr->ts.team;
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  struct gomp_work_share *ws = thr->ts.work_share;
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  unsigned index, next_id;
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  /* Work share constructs can be orphaned.  */
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  if (team == NULL || team->nthreads == 1)
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    return;
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  /* We're no longer the owner.  */
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  ws->ordered_owner = -1;
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  /* If there's only one thread in the queue, that must be us.  */
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  if (ws->ordered_num_used == 1)
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    {
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      /* We have a similar situation as in gomp_ordered_first
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         where we need to post to our own release semaphore.  */
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      gomp_sem_post (team->ordered_release[thr->ts.team_id]);
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      return;
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    }
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  /* If the queue is entirely full, then we move ourself to the end of
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     the queue merely by incrementing ordered_cur.  Only if it's not
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     full do we have to write our id.  */
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  if (ws->ordered_num_used < team->nthreads)
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    {
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      index = ws->ordered_cur + ws->ordered_num_used;
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      if (index >= team->nthreads)
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        index -= team->nthreads;
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      ws->ordered_team_ids[index] = thr->ts.team_id;
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    }
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  index = ws->ordered_cur + 1;
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  if (index == team->nthreads)
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    index = 0;
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  ws->ordered_cur = index;
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  next_id = ws->ordered_team_ids[index];
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  gomp_sem_post (team->ordered_release[next_id]);
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}
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/* This function is called when a statically scheduled loop is first
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   being created.  */
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void
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gomp_ordered_static_init (void)
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{
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  struct gomp_thread *thr = gomp_thread ();
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  struct gomp_team *team = thr->ts.team;
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  if (team == NULL || team->nthreads == 1)
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    return;
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  gomp_sem_post (team->ordered_release[0]);
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}
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/* This function is called when a statically scheduled loop is moving to
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   the next allocation block.  Static schedules are not first come first
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   served like the others, so we're to move to the numerically next thread,
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   not the next thread on a list.  The work-share lock should *not* be held
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   on entry.  */
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void
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gomp_ordered_static_next (void)
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{
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  struct gomp_thread *thr = gomp_thread ();
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  struct gomp_team *team = thr->ts.team;
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  struct gomp_work_share *ws = thr->ts.work_share;
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  unsigned id = thr->ts.team_id;
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  if (team == NULL || team->nthreads == 1)
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    return;
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  ws->ordered_owner = -1;
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  /* This thread currently owns the lock.  Increment the owner.  */
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  if (++id == team->nthreads)
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    id = 0;
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  ws->ordered_team_ids[0] = id;
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  gomp_sem_post (team->ordered_release[id]);
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}
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/* This function is called when we need to assert that the thread owns the
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   ordered section.  Due to the problem of posted-but-not-waited semaphores,
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   this needs to happen before completing a loop iteration.  */
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void
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gomp_ordered_sync (void)
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{
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  struct gomp_thread *thr = gomp_thread ();
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  struct gomp_team *team = thr->ts.team;
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  struct gomp_work_share *ws = thr->ts.work_share;
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  /* Work share constructs can be orphaned.  But this clearly means that
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     we are the only thread, and so we automatically own the section.  */
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  if (team == NULL || team->nthreads == 1)
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    return;
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  /* ??? I believe it to be safe to access this data without taking the
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     ws->lock.  The only presumed race condition is with the previous
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     thread on the queue incrementing ordered_cur such that it points
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     to us, concurrently with our check below.  But our team_id is
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     already present in the queue, and the other thread will always
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     post to our release semaphore.  So the two cases are that we will
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     either win the race an momentarily block on the semaphore, or lose
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     the race and find the semaphore already unlocked and so not block.
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     Either way we get correct results.
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     However, there is an implicit flush on entry to an ordered region,
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     so we do need to have a barrier here.  If we were taking a lock
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     this could be MEMMODEL_RELEASE since the acquire would be coverd
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     by the lock.  */
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  __atomic_thread_fence (MEMMODEL_ACQ_REL);
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  if (ws->ordered_owner != thr->ts.team_id)
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    {
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      gomp_sem_wait (team->ordered_release[thr->ts.team_id]);
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      ws->ordered_owner = thr->ts.team_id;
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    }
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}
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/* This function is called by user code when encountering the start of an
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   ORDERED block.  We must check to see if the current thread is at the
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   head of the queue, and if not, block.  */
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#ifdef HAVE_ATTRIBUTE_ALIAS
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extern void GOMP_ordered_start (void)
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        __attribute__((alias ("gomp_ordered_sync")));
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#else
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void
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GOMP_ordered_start (void)
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{
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  gomp_ordered_sync ();
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}
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#endif
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/* This function is called by user code when encountering the end of an
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   ORDERED block.  With the current ORDERED implementation there's nothing
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   for us to do.
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   However, the current implementation has a flaw in that it does not allow
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   the next thread into the ORDERED section immediately after the current
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   thread exits the ORDERED section in its last iteration.  The existance
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   of this function allows the implementation to change.  */
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void
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GOMP_ordered_end (void)
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{
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}

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