1  /* Copyright (C) 2015-2023 Free Software Foundation, Inc.
       2     Contributed by Mentor Embedded.
       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 is the AMD GCN implementation of doacross spinning.  */
      27  
      28  #ifndef GOMP_DOACROSS_H
      29  #define GOMP_DOACROSS_H 1
      30  
      31  #include "libgomp.h"
      32  
      33  static inline int
      34  cpu_relax (void)
      35  {
      36    /* This can be implemented as just a memory barrier, but a sleep seems
      37       like it should allow the wavefront to yield (maybe?)
      38       Use the shortest possible sleep time of 1*64 cycles.  */
      39    asm volatile ("s_sleep\t1" ::: "memory");
      40    return 0;
      41  }
      42  
      43  static inline void doacross_spin (unsigned long *addr, unsigned long expected,
      44  				  unsigned long cur)
      45  {
      46    /* Prevent compiler from optimizing based on bounds of containing object.  */
      47    asm ("" : "+r" (addr));
      48    do
      49      {
      50         /* An alternative implementation might use s_setprio to lower the
      51  	  priority temporarily, and then restore it after.  */
      52        int i = cpu_relax ();
      53        cur = addr[i];
      54      }
      55    while (cur <= expected);
      56  }
      57  
      58  #endif /* GOMP_DOACROSS_H */