1 /* Copyright (C) 2015-2023 Free Software Foundation, Inc.
2 Contributed by Alexander Monakov <amonakov@ispras.ru>
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 an NVPTX specific implementation of a barrier synchronization
27 mechanism for libgomp. This type is private to the library. This
28 implementation uses atomic instructions and bar.sync instruction. */
29
30 #ifndef GOMP_BARRIER_H
31 #define GOMP_BARRIER_H 1
32
33 #include "mutex.h"
34
35 typedef struct
36 {
37 unsigned total;
38 unsigned generation;
39 unsigned awaited;
40 unsigned awaited_final;
41 } gomp_barrier_t;
42
43 typedef unsigned int gomp_barrier_state_t;
44
45 /* The generation field contains a counter in the high bits, with a few
46 low bits dedicated to flags. Note that TASK_PENDING and WAS_LAST can
47 share space because WAS_LAST is never stored back to generation. */
48 #define BAR_TASK_PENDING 1
49 #define BAR_WAS_LAST 1
50 #define BAR_WAITING_FOR_TASK 2
51 #define BAR_CANCELLED 4
52 #define BAR_INCR 8
53
54 static inline void gomp_barrier_init (gomp_barrier_t *bar, unsigned count)
55 {
56 bar->total = count;
57 bar->awaited = count;
58 bar->awaited_final = count;
59 bar->generation = 0;
60 }
61
62 static inline void gomp_barrier_reinit (gomp_barrier_t *bar, unsigned count)
63 {
64 __atomic_add_fetch (&bar->awaited, count - bar->total, MEMMODEL_ACQ_REL);
65 bar->total = count;
66 }
67
68 static inline void gomp_barrier_destroy (gomp_barrier_t *bar)
69 {
70 }
71
72 extern void gomp_barrier_wait (gomp_barrier_t *);
73 extern void gomp_barrier_wait_last (gomp_barrier_t *);
74 extern void gomp_barrier_wait_end (gomp_barrier_t *, gomp_barrier_state_t);
75 extern void gomp_team_barrier_wait (gomp_barrier_t *);
76 extern void gomp_team_barrier_wait_final (gomp_barrier_t *);
77 extern void gomp_team_barrier_wait_end (gomp_barrier_t *,
78 gomp_barrier_state_t);
79 extern bool gomp_team_barrier_wait_cancel (gomp_barrier_t *);
80 extern bool gomp_team_barrier_wait_cancel_end (gomp_barrier_t *,
81 gomp_barrier_state_t);
82 struct gomp_team;
83 extern void gomp_team_barrier_cancel (struct gomp_team *);
84
85 static inline void
86 gomp_team_barrier_wake (gomp_barrier_t *bar, int count)
87 {
88 /* We never "wake up" threads on nvptx. Threads wait at barrier
89 instructions till barrier fullfilled. Do nothing here. */
90 }
91
92 static inline gomp_barrier_state_t
93 gomp_barrier_wait_start (gomp_barrier_t *bar)
94 {
95 unsigned int ret = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE);
96 ret &= -BAR_INCR | BAR_CANCELLED;
97 /* A memory barrier is needed before exiting from the various forms
98 of gomp_barrier_wait, to satisfy OpenMP API version 3.1 section
99 2.8.6 flush Construct, which says there is an implicit flush during
100 a barrier region. This is a convenient place to add the barrier,
101 so we use MEMMODEL_ACQ_REL here rather than MEMMODEL_ACQUIRE. */
102 if (__atomic_add_fetch (&bar->awaited, -1, MEMMODEL_ACQ_REL) == 0)
103 ret |= BAR_WAS_LAST;
104 return ret;
105 }
106
107 static inline gomp_barrier_state_t
108 gomp_barrier_wait_cancel_start (gomp_barrier_t *bar)
109 {
110 return gomp_barrier_wait_start (bar);
111 }
112
113 /* This is like gomp_barrier_wait_start, except it decrements
114 bar->awaited_final rather than bar->awaited and should be used
115 for the gomp_team_end barrier only. */
116 static inline gomp_barrier_state_t
117 gomp_barrier_wait_final_start (gomp_barrier_t *bar)
118 {
119 unsigned int ret = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE);
120 ret &= -BAR_INCR | BAR_CANCELLED;
121 /* See above gomp_barrier_wait_start comment. */
122 if (__atomic_add_fetch (&bar->awaited_final, -1, MEMMODEL_ACQ_REL) == 0)
123 ret |= BAR_WAS_LAST;
124 return ret;
125 }
126
127 static inline bool
128 gomp_barrier_last_thread (gomp_barrier_state_t state)
129 {
130 return state & BAR_WAS_LAST;
131 }
132
133 /* All the inlines below must be called with team->task_lock
134 held. */
135
136 static inline void
137 gomp_team_barrier_set_task_pending (gomp_barrier_t *bar)
138 {
139 bar->generation |= BAR_TASK_PENDING;
140 }
141
142 static inline void
143 gomp_team_barrier_clear_task_pending (gomp_barrier_t *bar)
144 {
145 bar->generation &= ~BAR_TASK_PENDING;
146 }
147
148 static inline void
149 gomp_team_barrier_set_waiting_for_tasks (gomp_barrier_t *bar)
150 {
151 bar->generation |= BAR_WAITING_FOR_TASK;
152 }
153
154 static inline bool
155 gomp_team_barrier_waiting_for_tasks (gomp_barrier_t *bar)
156 {
157 return (bar->generation & BAR_WAITING_FOR_TASK) != 0;
158 }
159
160 static inline bool
161 gomp_team_barrier_cancelled (gomp_barrier_t *bar)
162 {
163 return __builtin_expect ((bar->generation & BAR_CANCELLED) != 0, 0);
164 }
165
166 static inline void
167 gomp_team_barrier_done (gomp_barrier_t *bar, gomp_barrier_state_t state)
168 {
169 bar->generation = (state & -BAR_INCR) + BAR_INCR;
170 }
171
172 #endif /* GOMP_BARRIER_H */