1 /* Copyright (C) 2015-2020 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 */ 59