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83ffe9cd | 1 | /* Copyright (C) 2005-2023 Free Software Foundation, Inc. |
a68ab351 JJ |
2 | Contributed by Richard Henderson <rth@redhat.com>. |
3 | ||
f1f3453e TS |
4 | This file is part of the GNU Offloading and Multi Processing Library |
5 | (libgomp). | |
a68ab351 JJ |
6 | |
7 | Libgomp is free software; you can redistribute it and/or modify it | |
748086b7 JJ |
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. | |
a68ab351 JJ |
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 | |
748086b7 | 14 | FOR A PARTICULAR PURPOSE. See the GNU General Public License for |
a68ab351 JJ |
15 | more details. |
16 | ||
748086b7 JJ |
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/>. */ | |
a68ab351 JJ |
25 | |
26 | /* This file contains routines for managing work-share iteration, both | |
27 | for loops and sections. */ | |
28 | ||
29 | #include "libgomp.h" | |
30 | #include <stdlib.h> | |
31 | ||
32 | typedef unsigned long long gomp_ull; | |
33 | ||
34 | /* This function implements the STATIC scheduling method. The caller should | |
35 | iterate *pstart <= x < *pend. Return zero if there are more iterations | |
36 | to perform; nonzero if not. Return less than 0 if this thread had | |
37 | received the absolutely last iteration. */ | |
38 | ||
39 | int | |
40 | gomp_iter_ull_static_next (gomp_ull *pstart, gomp_ull *pend) | |
41 | { | |
42 | struct gomp_thread *thr = gomp_thread (); | |
43 | struct gomp_team *team = thr->ts.team; | |
44 | struct gomp_work_share *ws = thr->ts.work_share; | |
45 | unsigned long nthreads = team ? team->nthreads : 1; | |
46 | ||
47 | if (thr->ts.static_trip == -1) | |
48 | return -1; | |
49 | ||
50 | /* Quick test for degenerate teams and orphaned constructs. */ | |
51 | if (nthreads == 1) | |
52 | { | |
53 | *pstart = ws->next_ull; | |
54 | *pend = ws->end_ull; | |
55 | thr->ts.static_trip = -1; | |
56 | return ws->next_ull == ws->end_ull; | |
57 | } | |
58 | ||
59 | /* We interpret chunk_size zero as "unspecified", which means that we | |
60 | should break up the iterations such that each thread makes only one | |
61 | trip through the outer loop. */ | |
62 | if (ws->chunk_size_ull == 0) | |
63 | { | |
fb79f500 | 64 | gomp_ull n, q, i, t, s0, e0, s, e; |
a68ab351 JJ |
65 | |
66 | if (thr->ts.static_trip > 0) | |
67 | return 1; | |
68 | ||
69 | /* Compute the total number of iterations. */ | |
70 | if (__builtin_expect (ws->mode, 0) == 0) | |
71 | n = (ws->end_ull - ws->next_ull + ws->incr_ull - 1) / ws->incr_ull; | |
72 | else | |
73 | n = (ws->next_ull - ws->end_ull - ws->incr_ull - 1) / -ws->incr_ull; | |
74 | i = thr->ts.team_id; | |
75 | ||
76 | /* Compute the "zero-based" start and end points. That is, as | |
77 | if the loop began at zero and incremented by one. */ | |
78 | q = n / nthreads; | |
fb79f500 JJ |
79 | t = n % nthreads; |
80 | if (i < t) | |
81 | { | |
82 | t = 0; | |
83 | q++; | |
84 | } | |
85 | s0 = q * i + t; | |
a68ab351 | 86 | e0 = s0 + q; |
a68ab351 JJ |
87 | |
88 | /* Notice when no iterations allocated for this thread. */ | |
89 | if (s0 >= e0) | |
90 | { | |
91 | thr->ts.static_trip = 1; | |
92 | return 1; | |
93 | } | |
94 | ||
95 | /* Transform these to the actual start and end numbers. */ | |
96 | s = s0 * ws->incr_ull + ws->next_ull; | |
97 | e = e0 * ws->incr_ull + ws->next_ull; | |
98 | ||
99 | *pstart = s; | |
100 | *pend = e; | |
101 | thr->ts.static_trip = (e0 == n ? -1 : 1); | |
102 | return 0; | |
103 | } | |
104 | else | |
105 | { | |
106 | gomp_ull n, s0, e0, i, c, s, e; | |
107 | ||
108 | /* Otherwise, each thread gets exactly chunk_size iterations | |
109 | (if available) each time through the loop. */ | |
110 | ||
111 | if (__builtin_expect (ws->mode, 0) == 0) | |
112 | n = (ws->end_ull - ws->next_ull + ws->incr_ull - 1) / ws->incr_ull; | |
113 | else | |
114 | n = (ws->next_ull - ws->end_ull - ws->incr_ull - 1) / -ws->incr_ull; | |
115 | i = thr->ts.team_id; | |
116 | c = ws->chunk_size_ull; | |
117 | ||
118 | /* Initial guess is a C sized chunk positioned nthreads iterations | |
119 | in, offset by our thread number. */ | |
120 | s0 = (thr->ts.static_trip * (gomp_ull) nthreads + i) * c; | |
121 | e0 = s0 + c; | |
122 | ||
123 | /* Detect overflow. */ | |
124 | if (s0 >= n) | |
125 | return 1; | |
126 | if (e0 > n) | |
127 | e0 = n; | |
128 | ||
129 | /* Transform these to the actual start and end numbers. */ | |
130 | s = s0 * ws->incr_ull + ws->next_ull; | |
131 | e = e0 * ws->incr_ull + ws->next_ull; | |
132 | ||
133 | *pstart = s; | |
134 | *pend = e; | |
135 | ||
136 | if (e0 == n) | |
137 | thr->ts.static_trip = -1; | |
138 | else | |
139 | thr->ts.static_trip++; | |
140 | return 0; | |
141 | } | |
142 | } | |
143 | ||
144 | ||
145 | /* This function implements the DYNAMIC scheduling method. Arguments are | |
146 | as for gomp_iter_ull_static_next. This function must be called with | |
147 | ws->lock held. */ | |
148 | ||
149 | bool | |
150 | gomp_iter_ull_dynamic_next_locked (gomp_ull *pstart, gomp_ull *pend) | |
151 | { | |
152 | struct gomp_thread *thr = gomp_thread (); | |
153 | struct gomp_work_share *ws = thr->ts.work_share; | |
154 | gomp_ull start, end, chunk, left; | |
155 | ||
156 | start = ws->next_ull; | |
157 | if (start == ws->end_ull) | |
158 | return false; | |
159 | ||
160 | chunk = ws->chunk_size_ull; | |
161 | left = ws->end_ull - start; | |
162 | if (__builtin_expect (ws->mode & 2, 0)) | |
163 | { | |
164 | if (chunk < left) | |
165 | chunk = left; | |
166 | } | |
167 | else | |
168 | { | |
169 | if (chunk > left) | |
170 | chunk = left; | |
171 | } | |
172 | end = start + chunk; | |
173 | ||
174 | ws->next_ull = end; | |
175 | *pstart = start; | |
176 | *pend = end; | |
177 | return true; | |
178 | } | |
179 | ||
180 | ||
181 | #if defined HAVE_SYNC_BUILTINS && defined __LP64__ | |
182 | /* Similar, but doesn't require the lock held, and uses compare-and-swap | |
183 | instead. Note that the only memory value that changes is ws->next_ull. */ | |
184 | ||
185 | bool | |
186 | gomp_iter_ull_dynamic_next (gomp_ull *pstart, gomp_ull *pend) | |
187 | { | |
188 | struct gomp_thread *thr = gomp_thread (); | |
189 | struct gomp_work_share *ws = thr->ts.work_share; | |
190 | gomp_ull start, end, nend, chunk; | |
191 | ||
192 | end = ws->end_ull; | |
193 | chunk = ws->chunk_size_ull; | |
194 | ||
195 | if (__builtin_expect (ws->mode & 1, 1)) | |
196 | { | |
197 | gomp_ull tmp = __sync_fetch_and_add (&ws->next_ull, chunk); | |
198 | if (__builtin_expect (ws->mode & 2, 0) == 0) | |
199 | { | |
200 | if (tmp >= end) | |
201 | return false; | |
202 | nend = tmp + chunk; | |
203 | if (nend > end) | |
204 | nend = end; | |
205 | *pstart = tmp; | |
206 | *pend = nend; | |
207 | return true; | |
208 | } | |
209 | else | |
210 | { | |
211 | if (tmp <= end) | |
212 | return false; | |
213 | nend = tmp + chunk; | |
214 | if (nend < end) | |
215 | nend = end; | |
216 | *pstart = tmp; | |
217 | *pend = nend; | |
218 | return true; | |
219 | } | |
220 | } | |
221 | ||
bfe7ac89 | 222 | start = __atomic_load_n (&ws->next_ull, MEMMODEL_RELAXED); |
a68ab351 JJ |
223 | while (1) |
224 | { | |
225 | gomp_ull left = end - start; | |
226 | gomp_ull tmp; | |
227 | ||
228 | if (start == end) | |
229 | return false; | |
230 | ||
231 | if (__builtin_expect (ws->mode & 2, 0)) | |
232 | { | |
233 | if (chunk < left) | |
234 | chunk = left; | |
235 | } | |
236 | else | |
237 | { | |
238 | if (chunk > left) | |
239 | chunk = left; | |
240 | } | |
241 | nend = start + chunk; | |
242 | ||
243 | tmp = __sync_val_compare_and_swap (&ws->next_ull, start, nend); | |
244 | if (__builtin_expect (tmp == start, 1)) | |
245 | break; | |
246 | ||
247 | start = tmp; | |
248 | } | |
249 | ||
250 | *pstart = start; | |
251 | *pend = nend; | |
252 | return true; | |
253 | } | |
254 | #endif /* HAVE_SYNC_BUILTINS */ | |
255 | ||
256 | ||
257 | /* This function implements the GUIDED scheduling method. Arguments are | |
258 | as for gomp_iter_ull_static_next. This function must be called with the | |
259 | work share lock held. */ | |
260 | ||
261 | bool | |
262 | gomp_iter_ull_guided_next_locked (gomp_ull *pstart, gomp_ull *pend) | |
263 | { | |
264 | struct gomp_thread *thr = gomp_thread (); | |
265 | struct gomp_work_share *ws = thr->ts.work_share; | |
266 | struct gomp_team *team = thr->ts.team; | |
267 | gomp_ull nthreads = team ? team->nthreads : 1; | |
268 | gomp_ull n, q; | |
269 | gomp_ull start, end; | |
270 | ||
271 | if (ws->next_ull == ws->end_ull) | |
272 | return false; | |
273 | ||
274 | start = ws->next_ull; | |
275 | if (__builtin_expect (ws->mode, 0) == 0) | |
276 | n = (ws->end_ull - start) / ws->incr_ull; | |
277 | else | |
278 | n = (start - ws->end_ull) / -ws->incr_ull; | |
279 | q = (n + nthreads - 1) / nthreads; | |
280 | ||
281 | if (q < ws->chunk_size_ull) | |
282 | q = ws->chunk_size_ull; | |
283 | if (q <= n) | |
284 | end = start + q * ws->incr_ull; | |
285 | else | |
286 | end = ws->end_ull; | |
287 | ||
288 | ws->next_ull = end; | |
289 | *pstart = start; | |
290 | *pend = end; | |
291 | return true; | |
292 | } | |
293 | ||
294 | #if defined HAVE_SYNC_BUILTINS && defined __LP64__ | |
295 | /* Similar, but doesn't require the lock held, and uses compare-and-swap | |
296 | instead. Note that the only memory value that changes is ws->next_ull. */ | |
297 | ||
298 | bool | |
299 | gomp_iter_ull_guided_next (gomp_ull *pstart, gomp_ull *pend) | |
300 | { | |
301 | struct gomp_thread *thr = gomp_thread (); | |
302 | struct gomp_work_share *ws = thr->ts.work_share; | |
303 | struct gomp_team *team = thr->ts.team; | |
304 | gomp_ull nthreads = team ? team->nthreads : 1; | |
305 | gomp_ull start, end, nend, incr; | |
306 | gomp_ull chunk_size; | |
307 | ||
bfe7ac89 | 308 | start = __atomic_load_n (&ws->next_ull, MEMMODEL_RELAXED); |
a68ab351 JJ |
309 | end = ws->end_ull; |
310 | incr = ws->incr_ull; | |
311 | chunk_size = ws->chunk_size_ull; | |
312 | ||
313 | while (1) | |
314 | { | |
315 | gomp_ull n, q; | |
316 | gomp_ull tmp; | |
317 | ||
318 | if (start == end) | |
319 | return false; | |
320 | ||
321 | if (__builtin_expect (ws->mode, 0) == 0) | |
322 | n = (end - start) / incr; | |
323 | else | |
324 | n = (start - end) / -incr; | |
325 | q = (n + nthreads - 1) / nthreads; | |
326 | ||
327 | if (q < chunk_size) | |
328 | q = chunk_size; | |
329 | if (__builtin_expect (q <= n, 1)) | |
330 | nend = start + q * incr; | |
331 | else | |
332 | nend = end; | |
333 | ||
334 | tmp = __sync_val_compare_and_swap (&ws->next_ull, start, nend); | |
335 | if (__builtin_expect (tmp == start, 1)) | |
336 | break; | |
337 | ||
338 | start = tmp; | |
339 | } | |
340 | ||
341 | *pstart = start; | |
342 | *pend = nend; | |
343 | return true; | |
344 | } | |
345 | #endif /* HAVE_SYNC_BUILTINS */ |