text: /* Copyright (C) 2015-2020 Free Software Foundation, Inc.
     Contributed by Alexander Monakov <amonakov@ispras.ru>
  
     This file is part of the GNU Offloading and Multi Processing Library
     (libgomp).
  
     Libgomp is free software; you can redistribute it and/or modify it
     under the terms of the GNU General Public License as published by
     the Free Software Foundation; either version 3, or (at your option)
     any later version.
  
     Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
     WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
     FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
     more details.
  
     Under Section 7 of GPL version 3, you are granted additional
     permissions described in the GCC Runtime Library Exception, version
     3.1, as published by the Free Software Foundation.
  
     You should have received a copy of the GNU General Public License and
     a copy of the GCC Runtime Library Exception along with this program;
     see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
     <http://www.gnu.org/licenses/>.  */
  
  /* This is an NVPTX specific implementation of a barrier synchronization
     mechanism for libgomp.  This type is private to the library.  This
     implementation uses atomic instructions and bar.sync instruction.  */
  
  #ifndef GOMP_BARRIER_H
  #define GOMP_BARRIER_H 1
  
  #include "mutex.h"
  
  typedef struct
  {
    unsigned total;
    unsigned generation;
    unsigned awaited;
    unsigned awaited_final;
  } gomp_barrier_t;
  
  typedef unsigned int gomp_barrier_state_t;
  
  /* The generation field contains a counter in the high bits, with a few
     low bits dedicated to flags.  Note that TASK_PENDING and WAS_LAST can
     share space because WAS_LAST is never stored back to generation.  */
  #define BAR_TASK_PENDING	1
  #define BAR_WAS_LAST		1
  #define BAR_WAITING_FOR_TASK	2
  #define BAR_CANCELLED		4
  #define BAR_INCR		8
  
  static inline void gomp_barrier_init (gomp_barrier_t *bar, unsigned count)
  {
    bar->total = count;
    bar->awaited = count;
    bar->awaited_final = count;
    bar->generation = 0;
  }
  
  static inline void gomp_barrier_reinit (gomp_barrier_t *bar, unsigned count)
  {
    __atomic_add_fetch (&bar->awaited, count - bar->total, MEMMODEL_ACQ_REL);
    bar->total = count;
  }
  
  static inline void gomp_barrier_destroy (gomp_barrier_t *bar)
  {
  }
  
  extern void gomp_barrier_wait (gomp_barrier_t *);
  extern void gomp_barrier_wait_last (gomp_barrier_t *);
  extern void gomp_barrier_wait_end (gomp_barrier_t *, gomp_barrier_state_t);
  extern void gomp_team_barrier_wait (gomp_barrier_t *);
  extern void gomp_team_barrier_wait_final (gomp_barrier_t *);
  extern void gomp_team_barrier_wait_end (gomp_barrier_t *,
  					gomp_barrier_state_t);
  extern bool gomp_team_barrier_wait_cancel (gomp_barrier_t *);
  extern bool gomp_team_barrier_wait_cancel_end (gomp_barrier_t *,
  					       gomp_barrier_state_t);
  extern void gomp_team_barrier_wake (gomp_barrier_t *, int);
  struct gomp_team;
  extern void gomp_team_barrier_cancel (struct gomp_team *);
  
  static inline gomp_barrier_state_t
  gomp_barrier_wait_start (gomp_barrier_t *bar)
  {
    unsigned int ret = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE);
    ret &= -BAR_INCR | BAR_CANCELLED;
    /* A memory barrier is needed before exiting from the various forms
       of gomp_barrier_wait, to satisfy OpenMP API version 3.1 section
       2.8.6 flush Construct, which says there is an implicit flush during
       a barrier region.  This is a convenient place to add the barrier,
       so we use MEMMODEL_ACQ_REL here rather than MEMMODEL_ACQUIRE.  */
    if (__atomic_add_fetch (&bar->awaited, -1, MEMMODEL_ACQ_REL) == 0)
      ret |= BAR_WAS_LAST;
    return ret;
  }
  
  static inline gomp_barrier_state_t
  gomp_barrier_wait_cancel_start (gomp_barrier_t *bar)
  {
    return gomp_barrier_wait_start (bar);
  }
  
  /* This is like gomp_barrier_wait_start, except it decrements
     bar->awaited_final rather than bar->awaited and should be used
     for the gomp_team_end barrier only.  */
  static inline gomp_barrier_state_t
  gomp_barrier_wait_final_start (gomp_barrier_t *bar)
  {
    unsigned int ret = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE);
    ret &= -BAR_INCR | BAR_CANCELLED;
    /* See above gomp_barrier_wait_start comment.  */
    if (__atomic_add_fetch (&bar->awaited_final, -1, MEMMODEL_ACQ_REL) == 0)
      ret |= BAR_WAS_LAST;
    return ret;
  }
  
  static inline bool
  gomp_barrier_last_thread (gomp_barrier_state_t state)
  {
    return state & BAR_WAS_LAST;
  }
  
  /* All the inlines below must be called with team->task_lock
     held.  */
  
  static inline void
  gomp_team_barrier_set_task_pending (gomp_barrier_t *bar)
  {
    bar->generation |= BAR_TASK_PENDING;
  }
  
  static inline void
  gomp_team_barrier_clear_task_pending (gomp_barrier_t *bar)
  {
    bar->generation &= ~BAR_TASK_PENDING;
  }
  
  static inline void
  gomp_team_barrier_set_waiting_for_tasks (gomp_barrier_t *bar)
  {
    bar->generation |= BAR_WAITING_FOR_TASK;
  }
  
  static inline bool
  gomp_team_barrier_waiting_for_tasks (gomp_barrier_t *bar)
  {
    return (bar->generation & BAR_WAITING_FOR_TASK) != 0;
  }
  
  static inline bool
  gomp_team_barrier_cancelled (gomp_barrier_t *bar)
  {
    return __builtin_expect ((bar->generation & BAR_CANCELLED) != 0, 0);
  }
  
  static inline void
  gomp_team_barrier_done (gomp_barrier_t *bar, gomp_barrier_state_t state)
  {
    bar->generation = (state & -BAR_INCR) + BAR_INCR;
  }
  
  #endif /* GOMP_BARRIER_H */
  