File: | polly/lib/External/isl/isl_stride.c |
Warning: | line 151, column 2 Value stored to 'pos' is never read |
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1 | /* |
2 | * Copyright 2012-2013 Ecole Normale Superieure |
3 | * |
4 | * Use of this software is governed by the MIT license |
5 | * |
6 | * Written by Sven Verdoolaege, |
7 | * Ecole Normale Superieure, 45 rue d'Ulm, 75230 Paris, France |
8 | */ |
9 | |
10 | #include <isl/val.h> |
11 | #include <isl_map_private.h> |
12 | #include <isl_aff_private.h> |
13 | #include <isl/constraint.h> |
14 | #include <isl/set.h> |
15 | |
16 | /* Stride information about a specific set dimension. |
17 | * The values of the set dimension are equal to |
18 | * "offset" plus a multiple of "stride". |
19 | */ |
20 | struct isl_stride_info { |
21 | isl_val *stride; |
22 | isl_aff *offset; |
23 | }; |
24 | |
25 | /* Return the ctx to which "si" belongs. |
26 | */ |
27 | isl_ctx *isl_stride_info_get_ctx(__isl_keep isl_stride_info *si) |
28 | { |
29 | if (!si) |
30 | return NULL((void*)0); |
31 | |
32 | return isl_val_get_ctx(si->stride); |
33 | } |
34 | |
35 | /* Free "si" and return NULL. |
36 | */ |
37 | __isl_null isl_stride_info *isl_stride_info_free( |
38 | __isl_take isl_stride_info *si) |
39 | { |
40 | if (!si) |
41 | return NULL((void*)0); |
42 | isl_val_free(si->stride); |
43 | isl_aff_free(si->offset); |
44 | free(si); |
45 | return NULL((void*)0); |
46 | } |
47 | |
48 | /* Construct an isl_stride_info object with given offset and stride. |
49 | */ |
50 | __isl_give isl_stride_info *isl_stride_info_alloc( |
51 | __isl_take isl_val *stride, __isl_take isl_aff *offset) |
52 | { |
53 | struct isl_stride_info *si; |
54 | |
55 | if (!stride || !offset) |
56 | goto error; |
57 | si = isl_alloc_type(isl_val_get_ctx(stride), struct isl_stride_info)((struct isl_stride_info *)isl_malloc_or_die(isl_val_get_ctx( stride), sizeof(struct isl_stride_info))); |
58 | if (!si) |
59 | goto error; |
60 | si->stride = stride; |
61 | si->offset = offset; |
62 | return si; |
63 | error: |
64 | isl_val_free(stride); |
65 | isl_aff_free(offset); |
66 | return NULL((void*)0); |
67 | } |
68 | |
69 | /* Make a copy of "si" and return it. |
70 | */ |
71 | __isl_give isl_stride_info *isl_stride_info_copy( |
72 | __isl_keep isl_stride_info *si) |
73 | { |
74 | if (!si) |
75 | return NULL((void*)0); |
76 | |
77 | return isl_stride_info_alloc(isl_val_copy(si->stride), |
78 | isl_aff_copy(si->offset)); |
79 | } |
80 | |
81 | /* Return the stride of "si". |
82 | */ |
83 | __isl_give isl_val *isl_stride_info_get_stride(__isl_keep isl_stride_info *si) |
84 | { |
85 | if (!si) |
86 | return NULL((void*)0); |
87 | return isl_val_copy(si->stride); |
88 | } |
89 | |
90 | /* Return the offset of "si". |
91 | */ |
92 | __isl_give isl_aff *isl_stride_info_get_offset(__isl_keep isl_stride_info *si) |
93 | { |
94 | if (!si) |
95 | return NULL((void*)0); |
96 | return isl_aff_copy(si->offset); |
97 | } |
98 | |
99 | /* Information used inside detect_stride. |
100 | * |
101 | * "pos" is the set dimension at which the stride is being determined. |
102 | * "want_offset" is set if the offset should be computed. |
103 | * "found" is set if some stride was found already. |
104 | * "stride" and "offset" contain the (combined) stride and offset |
105 | * found so far and are NULL when "found" is not set. |
106 | * If "want_offset" is not set, then "offset" remains NULL. |
107 | */ |
108 | struct isl_detect_stride_data { |
109 | int pos; |
110 | int want_offset; |
111 | int found; |
112 | isl_val *stride; |
113 | isl_aff *offset; |
114 | }; |
115 | |
116 | /* Set the stride and offset of data->pos to the given |
117 | * value and expression. |
118 | * |
119 | * If we had already found a stride before, then the two strides |
120 | * are combined into a single stride. |
121 | * |
122 | * In particular, if the new stride information is of the form |
123 | * |
124 | * i = f + s (...) |
125 | * |
126 | * and the old stride information is of the form |
127 | * |
128 | * i = f2 + s2 (...) |
129 | * |
130 | * then we compute the extended gcd of s and s2 |
131 | * |
132 | * a s + b s2 = g, |
133 | * |
134 | * with g = gcd(s,s2), multiply the first equation with t1 = b s2/g |
135 | * and the second with t2 = a s1/g. |
136 | * This results in |
137 | * |
138 | * i = (b s2 + a s1)/g i = t1 f + t2 f2 + (s s2)/g (...) |
139 | * |
140 | * so that t1 f + t2 f2 is the combined offset and (s s2)/g = lcm(s,s2) |
141 | * is the combined stride. |
142 | */ |
143 | static isl_stat set_stride(struct isl_detect_stride_data *data, |
144 | __isl_take isl_val *stride, __isl_take isl_aff *offset) |
145 | { |
146 | int pos; |
147 | |
148 | if (!stride || !offset) |
149 | goto error; |
150 | |
151 | pos = data->pos; |
Value stored to 'pos' is never read | |
152 | |
153 | if (data->found) { |
154 | isl_val *stride2, *a, *b, *g; |
155 | isl_aff *offset2; |
156 | |
157 | stride2 = data->stride; |
158 | g = isl_val_gcdext(isl_val_copy(stride), isl_val_copy(stride2), |
159 | &a, &b); |
160 | a = isl_val_mul(a, isl_val_copy(stride)); |
161 | a = isl_val_div(a, isl_val_copy(g)); |
162 | stride2 = isl_val_div(stride2, g); |
163 | b = isl_val_mul(b, isl_val_copy(stride2)); |
164 | stride = isl_val_mul(stride, stride2); |
165 | |
166 | if (!data->want_offset) { |
167 | isl_val_free(a); |
168 | isl_val_free(b); |
169 | } else { |
170 | offset2 = data->offset; |
171 | offset2 = isl_aff_scale_val(offset2, a); |
172 | offset = isl_aff_scale_val(offset, b); |
173 | offset = isl_aff_add(offset, offset2); |
174 | } |
175 | } |
176 | |
177 | data->found = 1; |
178 | data->stride = stride; |
179 | if (data->want_offset) |
180 | data->offset = offset; |
181 | else |
182 | isl_aff_free(offset); |
183 | if (!data->stride || (data->want_offset && !data->offset)) |
184 | return isl_stat_error; |
185 | |
186 | return isl_stat_ok; |
187 | error: |
188 | isl_val_free(stride); |
189 | isl_aff_free(offset); |
190 | return isl_stat_error; |
191 | } |
192 | |
193 | /* Check if constraint "c" imposes any stride on dimension data->pos |
194 | * and, if so, update the stride information in "data". |
195 | * |
196 | * In order to impose a stride on the dimension, "c" needs to be an equality |
197 | * and it needs to involve the dimension. Note that "c" may also be |
198 | * a div constraint and thus an inequality that we cannot use. |
199 | * |
200 | * Let c be of the form |
201 | * |
202 | * h(p) + g * v * i + g * stride * f(alpha) = 0 |
203 | * |
204 | * with h(p) an expression in terms of the parameters and other dimensions |
205 | * and f(alpha) an expression in terms of the existentially quantified |
206 | * variables. |
207 | * |
208 | * If "stride" is not zero and not one, then it represents a non-trivial stride |
209 | * on "i". We compute a and b such that |
210 | * |
211 | * a v + b stride = 1 |
212 | * |
213 | * We have |
214 | * |
215 | * g v i = -h(p) + g stride f(alpha) |
216 | * |
217 | * a g v i = -a h(p) + g stride f(alpha) |
218 | * |
219 | * a g v i + b g stride i = -a h(p) + g stride * (...) |
220 | * |
221 | * g i = -a h(p) + g stride * (...) |
222 | * |
223 | * i = -a h(p)/g + stride * (...) |
224 | * |
225 | * The expression "-a h(p)/g" can therefore be used as offset. |
226 | */ |
227 | static isl_stat detect_stride(__isl_take isl_constraint *c, void *user) |
228 | { |
229 | struct isl_detect_stride_data *data = user; |
230 | int i; |
231 | isl_size n_div; |
232 | isl_ctx *ctx; |
233 | isl_stat r = isl_stat_ok; |
234 | isl_val *v, *stride, *m; |
235 | isl_bool is_eq, relevant, has_stride; |
236 | |
237 | is_eq = isl_constraint_is_equality(c); |
238 | relevant = isl_constraint_involves_dims(c, isl_dim_set, data->pos, 1); |
239 | if (is_eq < 0 || relevant < 0) |
240 | goto error; |
241 | if (!is_eq || !relevant) { |
242 | isl_constraint_free(c); |
243 | return isl_stat_ok; |
244 | } |
245 | |
246 | n_div = isl_constraint_dim(c, isl_dim_div); |
247 | if (n_div < 0) |
248 | goto error; |
249 | ctx = isl_constraint_get_ctx(c); |
250 | stride = isl_val_zero(ctx); |
251 | for (i = 0; i < n_div; ++i) { |
252 | v = isl_constraint_get_coefficient_val(c, isl_dim_div, i); |
253 | stride = isl_val_gcd(stride, v); |
254 | } |
255 | |
256 | v = isl_constraint_get_coefficient_val(c, isl_dim_set, data->pos); |
257 | m = isl_val_gcd(isl_val_copy(stride), isl_val_copy(v)); |
258 | stride = isl_val_div(stride, isl_val_copy(m)); |
259 | v = isl_val_div(v, isl_val_copy(m)); |
260 | |
261 | has_stride = isl_val_gt_si(stride, 1); |
262 | if (has_stride >= 0 && has_stride) { |
263 | isl_aff *aff; |
264 | isl_val *gcd, *a, *b; |
265 | |
266 | gcd = isl_val_gcdext(v, isl_val_copy(stride), &a, &b); |
267 | isl_val_free(gcd); |
268 | isl_val_free(b); |
269 | |
270 | aff = isl_constraint_get_aff(c); |
271 | for (i = 0; i < n_div; ++i) |
272 | aff = isl_aff_set_coefficient_si(aff, |
273 | isl_dim_div, i, 0); |
274 | aff = isl_aff_set_coefficient_si(aff, isl_dim_in, data->pos, 0); |
275 | aff = isl_aff_remove_unused_divs(aff); |
276 | a = isl_val_neg(a); |
277 | aff = isl_aff_scale_val(aff, a); |
278 | aff = isl_aff_scale_down_val(aff, m); |
279 | r = set_stride(data, stride, aff); |
280 | } else { |
281 | isl_val_free(stride); |
282 | isl_val_free(m); |
283 | isl_val_free(v); |
284 | } |
285 | |
286 | isl_constraint_free(c); |
287 | if (has_stride < 0) |
288 | return isl_stat_error; |
289 | return r; |
290 | error: |
291 | isl_constraint_free(c); |
292 | return isl_stat_error; |
293 | } |
294 | |
295 | /* Check if the constraints in "set" imply any stride on set dimension "pos" and |
296 | * store the results in data->stride and data->offset. |
297 | * |
298 | * In particular, compute the affine hull and then check if |
299 | * any of the constraints in the hull impose any stride on the dimension. |
300 | * If no such constraint can be found, then the offset is taken |
301 | * to be the zero expression and the stride is taken to be one. |
302 | */ |
303 | static void set_detect_stride(__isl_keep isl_setisl_map *set, int pos, |
304 | struct isl_detect_stride_data *data) |
305 | { |
306 | isl_basic_setisl_basic_map *hull; |
307 | |
308 | hull = isl_set_affine_hull(isl_set_copy(set)); |
309 | |
310 | data->pos = pos; |
311 | data->found = 0; |
312 | data->stride = NULL((void*)0); |
313 | data->offset = NULL((void*)0); |
314 | if (isl_basic_set_foreach_constraint(hull, &detect_stride, data) < 0) |
315 | goto error; |
316 | |
317 | if (!data->found) { |
318 | data->stride = isl_val_one(isl_set_get_ctx(set)); |
319 | if (data->want_offset) { |
320 | isl_space *space; |
321 | isl_local_space *ls; |
322 | |
323 | space = isl_set_get_space(set); |
324 | ls = isl_local_space_from_space(space); |
325 | data->offset = isl_aff_zero_on_domain(ls); |
326 | } |
327 | } |
328 | isl_basic_set_free(hull); |
329 | return; |
330 | error: |
331 | isl_basic_set_free(hull); |
332 | data->stride = isl_val_free(data->stride); |
333 | data->offset = isl_aff_free(data->offset); |
334 | } |
335 | |
336 | /* Check if the constraints in "set" imply any stride on set dimension "pos" and |
337 | * return the results in the form of an offset and a stride. |
338 | */ |
339 | __isl_give isl_stride_info *isl_set_get_stride_info(__isl_keep isl_setisl_map *set, |
340 | int pos) |
341 | { |
342 | struct isl_detect_stride_data data; |
343 | |
344 | data.want_offset = 1; |
345 | set_detect_stride(set, pos, &data); |
346 | |
347 | return isl_stride_info_alloc(data.stride, data.offset); |
348 | } |
349 | |
350 | /* Check if the constraints in "set" imply any stride on set dimension "pos" and |
351 | * return this stride. |
352 | */ |
353 | __isl_give isl_val *isl_set_get_stride(__isl_keep isl_setisl_map *set, int pos) |
354 | { |
355 | struct isl_detect_stride_data data; |
356 | |
357 | data.want_offset = 0; |
358 | set_detect_stride(set, pos, &data); |
359 | |
360 | return data.stride; |
361 | } |
362 | |
363 | /* Check if the constraints in "map" imply any stride on output dimension "pos", |
364 | * independently of any other output dimensions, and |
365 | * return the results in the form of an offset and a stride. |
366 | * |
367 | * Convert the input to a set with only the input dimensions and |
368 | * the single output dimension such that it be passed to |
369 | * isl_set_get_stride_info and convert the result back to |
370 | * an expression defined over the domain of "map". |
371 | */ |
372 | __isl_give isl_stride_info *isl_map_get_range_stride_info( |
373 | __isl_keep isl_map *map, int pos) |
374 | { |
375 | isl_stride_info *si; |
376 | isl_setisl_map *set; |
377 | isl_size n_in; |
378 | |
379 | n_in = isl_map_dim(map, isl_dim_in); |
380 | if (n_in < 0) |
381 | return NULL((void*)0); |
382 | map = isl_map_copy(map); |
383 | map = isl_map_project_onto(map, isl_dim_out, pos, 1); |
384 | set = isl_map_wrap(map); |
385 | si = isl_set_get_stride_info(set, n_in); |
386 | isl_set_free(set); |
387 | if (!si) |
388 | return NULL((void*)0); |
389 | si->offset = isl_aff_domain_factor_domain(si->offset); |
390 | if (!si->offset) |
391 | return isl_stride_info_free(si); |
392 | return si; |
393 | } |