Mercurial > hg > CbC > CbC_gcc
annotate gcc/tree-ssa-loop-prefetch.c @ 128:fe568345ddd5
fix CbC-example
| author | mir3636 |
|---|---|
| date | Wed, 11 Apr 2018 19:32:28 +0900 |
| parents | 04ced10e8804 |
| children | 84e7813d76e9 |
| rev | line source |
|---|---|
| 0 | 1 /* Array prefetching. |
| 111 | 2 Copyright (C) 2005-2017 Free Software Foundation, Inc. |
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3 |
| 0 | 4 This file is part of GCC. |
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5 |
| 0 | 6 GCC is free software; you can redistribute it and/or modify it |
| 7 under the terms of the GNU General Public License as published by the | |
| 8 Free Software Foundation; either version 3, or (at your option) any | |
| 9 later version. | |
|
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10 |
| 0 | 11 GCC is distributed in the hope that it will be useful, but WITHOUT |
| 12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 14 for more details. | |
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15 |
| 0 | 16 You should have received a copy of the GNU General Public License |
| 17 along with GCC; see the file COPYING3. If not see | |
| 18 <http://www.gnu.org/licenses/>. */ | |
| 19 | |
| 20 #include "config.h" | |
| 21 #include "system.h" | |
| 22 #include "coretypes.h" | |
| 111 | 23 #include "backend.h" |
| 24 #include "target.h" | |
| 25 #include "rtl.h" | |
| 0 | 26 #include "tree.h" |
| 111 | 27 #include "gimple.h" |
| 28 #include "predict.h" | |
| 29 #include "tree-pass.h" | |
| 30 #include "gimple-ssa.h" | |
| 31 #include "optabs-query.h" | |
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32 #include "tree-pretty-print.h" |
| 111 | 33 #include "fold-const.h" |
| 34 #include "stor-layout.h" | |
| 35 #include "gimplify.h" | |
| 36 #include "gimple-iterator.h" | |
| 37 #include "gimplify-me.h" | |
| 38 #include "tree-ssa-loop-ivopts.h" | |
| 39 #include "tree-ssa-loop-manip.h" | |
| 40 #include "tree-ssa-loop-niter.h" | |
| 41 #include "tree-ssa-loop.h" | |
| 42 #include "ssa.h" | |
| 43 #include "tree-into-ssa.h" | |
| 0 | 44 #include "cfgloop.h" |
| 45 #include "tree-scalar-evolution.h" | |
| 46 #include "params.h" | |
| 47 #include "langhooks.h" | |
| 48 #include "tree-inline.h" | |
| 49 #include "tree-data-ref.h" | |
| 111 | 50 #include "diagnostic-core.h" |
| 51 #include "dbgcnt.h" | |
| 0 | 52 |
| 53 /* This pass inserts prefetch instructions to optimize cache usage during | |
| 54 accesses to arrays in loops. It processes loops sequentially and: | |
| 55 | |
| 56 1) Gathers all memory references in the single loop. | |
| 57 2) For each of the references it decides when it is profitable to prefetch | |
| 58 it. To do it, we evaluate the reuse among the accesses, and determines | |
| 59 two values: PREFETCH_BEFORE (meaning that it only makes sense to do | |
| 60 prefetching in the first PREFETCH_BEFORE iterations of the loop) and | |
| 61 PREFETCH_MOD (meaning that it only makes sense to prefetch in the | |
| 62 iterations of the loop that are zero modulo PREFETCH_MOD). For example | |
| 63 (assuming cache line size is 64 bytes, char has size 1 byte and there | |
| 64 is no hardware sequential prefetch): | |
| 65 | |
| 66 char *a; | |
| 67 for (i = 0; i < max; i++) | |
| 68 { | |
| 69 a[255] = ...; (0) | |
| 70 a[i] = ...; (1) | |
| 71 a[i + 64] = ...; (2) | |
| 72 a[16*i] = ...; (3) | |
| 73 a[187*i] = ...; (4) | |
| 74 a[187*i + 50] = ...; (5) | |
| 75 } | |
| 76 | |
| 77 (0) obviously has PREFETCH_BEFORE 1 | |
| 78 (1) has PREFETCH_BEFORE 64, since (2) accesses the same memory | |
| 79 location 64 iterations before it, and PREFETCH_MOD 64 (since | |
| 80 it hits the same cache line otherwise). | |
| 81 (2) has PREFETCH_MOD 64 | |
| 82 (3) has PREFETCH_MOD 4 | |
| 83 (4) has PREFETCH_MOD 1. We do not set PREFETCH_BEFORE here, since | |
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84 the cache line accessed by (5) is the same with probability only |
| 0 | 85 7/32. |
| 86 (5) has PREFETCH_MOD 1 as well. | |
| 87 | |
| 88 Additionally, we use data dependence analysis to determine for each | |
| 89 reference the distance till the first reuse; this information is used | |
| 90 to determine the temporality of the issued prefetch instruction. | |
| 91 | |
| 92 3) We determine how much ahead we need to prefetch. The number of | |
| 93 iterations needed is time to fetch / time spent in one iteration of | |
| 94 the loop. The problem is that we do not know either of these values, | |
| 95 so we just make a heuristic guess based on a magic (possibly) | |
| 96 target-specific constant and size of the loop. | |
| 97 | |
| 98 4) Determine which of the references we prefetch. We take into account | |
| 99 that there is a maximum number of simultaneous prefetches (provided | |
| 100 by machine description). We prefetch as many prefetches as possible | |
| 101 while still within this bound (starting with those with lowest | |
| 102 prefetch_mod, since they are responsible for most of the cache | |
| 103 misses). | |
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104 |
| 0 | 105 5) We unroll and peel loops so that we are able to satisfy PREFETCH_MOD |
| 106 and PREFETCH_BEFORE requirements (within some bounds), and to avoid | |
| 107 prefetching nonaccessed memory. | |
| 108 TODO -- actually implement peeling. | |
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109 |
| 0 | 110 6) We actually emit the prefetch instructions. ??? Perhaps emit the |
| 111 prefetch instructions with guards in cases where 5) was not sufficient | |
| 112 to satisfy the constraints? | |
| 113 | |
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114 A cost model is implemented to determine whether or not prefetching is |
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115 profitable for a given loop. The cost model has three heuristics: |
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116 |
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117 1. Function trip_count_to_ahead_ratio_too_small_p implements a |
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118 heuristic that determines whether or not the loop has too few |
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119 iterations (compared to ahead). Prefetching is not likely to be |
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120 beneficial if the trip count to ahead ratio is below a certain |
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121 minimum. |
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122 |
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123 2. Function mem_ref_count_reasonable_p implements a heuristic that |
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124 determines whether the given loop has enough CPU ops that can be |
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125 overlapped with cache missing memory ops. If not, the loop |
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126 won't benefit from prefetching. In the implementation, |
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127 prefetching is not considered beneficial if the ratio between |
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128 the instruction count and the mem ref count is below a certain |
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129 minimum. |
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130 |
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131 3. Function insn_to_prefetch_ratio_too_small_p implements a |
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132 heuristic that disables prefetching in a loop if the prefetching |
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133 cost is above a certain limit. The relative prefetching cost is |
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134 estimated by taking the ratio between the prefetch count and the |
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135 total intruction count (this models the I-cache cost). |
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136 |
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137 The limits used in these heuristics are defined as parameters with |
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138 reasonable default values. Machine-specific default values will be |
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139 added later. |
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140 |
| 0 | 141 Some other TODO: |
| 142 -- write and use more general reuse analysis (that could be also used | |
| 143 in other cache aimed loop optimizations) | |
| 144 -- make it behave sanely together with the prefetches given by user | |
| 145 (now we just ignore them; at the very least we should avoid | |
| 146 optimizing loops in that user put his own prefetches) | |
| 147 -- we assume cache line size alignment of arrays; this could be | |
| 148 improved. */ | |
| 149 | |
| 150 /* Magic constants follow. These should be replaced by machine specific | |
| 151 numbers. */ | |
| 152 | |
| 153 /* True if write can be prefetched by a read prefetch. */ | |
| 154 | |
| 155 #ifndef WRITE_CAN_USE_READ_PREFETCH | |
| 156 #define WRITE_CAN_USE_READ_PREFETCH 1 | |
| 157 #endif | |
| 158 | |
| 159 /* True if read can be prefetched by a write prefetch. */ | |
| 160 | |
| 161 #ifndef READ_CAN_USE_WRITE_PREFETCH | |
| 162 #define READ_CAN_USE_WRITE_PREFETCH 0 | |
| 163 #endif | |
| 164 | |
| 165 /* The size of the block loaded by a single prefetch. Usually, this is | |
| 166 the same as cache line size (at the moment, we only consider one level | |
| 167 of cache hierarchy). */ | |
| 168 | |
| 169 #ifndef PREFETCH_BLOCK | |
| 170 #define PREFETCH_BLOCK L1_CACHE_LINE_SIZE | |
| 171 #endif | |
| 172 | |
| 173 /* Do we have a forward hardware sequential prefetching? */ | |
| 174 | |
| 175 #ifndef HAVE_FORWARD_PREFETCH | |
| 176 #define HAVE_FORWARD_PREFETCH 0 | |
| 177 #endif | |
| 178 | |
| 179 /* Do we have a backward hardware sequential prefetching? */ | |
| 180 | |
| 181 #ifndef HAVE_BACKWARD_PREFETCH | |
| 182 #define HAVE_BACKWARD_PREFETCH 0 | |
| 183 #endif | |
| 184 | |
| 185 /* In some cases we are only able to determine that there is a certain | |
| 186 probability that the two accesses hit the same cache line. In this | |
| 187 case, we issue the prefetches for both of them if this probability | |
| 188 is less then (1000 - ACCEPTABLE_MISS_RATE) per thousand. */ | |
| 189 | |
| 190 #ifndef ACCEPTABLE_MISS_RATE | |
| 191 #define ACCEPTABLE_MISS_RATE 50 | |
| 192 #endif | |
| 193 | |
| 194 #define L1_CACHE_SIZE_BYTES ((unsigned) (L1_CACHE_SIZE * 1024)) | |
| 195 #define L2_CACHE_SIZE_BYTES ((unsigned) (L2_CACHE_SIZE * 1024)) | |
| 196 | |
| 197 /* We consider a memory access nontemporal if it is not reused sooner than | |
| 198 after L2_CACHE_SIZE_BYTES of memory are accessed. However, we ignore | |
| 199 accesses closer than L1_CACHE_SIZE_BYTES / NONTEMPORAL_FRACTION, | |
| 200 so that we use nontemporal prefetches e.g. if single memory location | |
| 201 is accessed several times in a single iteration of the loop. */ | |
| 202 #define NONTEMPORAL_FRACTION 16 | |
| 203 | |
| 204 /* In case we have to emit a memory fence instruction after the loop that | |
| 205 uses nontemporal stores, this defines the builtin to use. */ | |
| 206 | |
| 207 #ifndef FENCE_FOLLOWING_MOVNT | |
| 208 #define FENCE_FOLLOWING_MOVNT NULL_TREE | |
| 209 #endif | |
| 210 | |
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211 /* It is not profitable to prefetch when the trip count is not at |
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212 least TRIP_COUNT_TO_AHEAD_RATIO times the prefetch ahead distance. |
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213 For example, in a loop with a prefetch ahead distance of 10, |
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214 supposing that TRIP_COUNT_TO_AHEAD_RATIO is equal to 4, it is |
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215 profitable to prefetch when the trip count is greater or equal to |
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216 40. In that case, 30 out of the 40 iterations will benefit from |
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217 prefetching. */ |
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218 |
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219 #ifndef TRIP_COUNT_TO_AHEAD_RATIO |
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220 #define TRIP_COUNT_TO_AHEAD_RATIO 4 |
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221 #endif |
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222 |
| 0 | 223 /* The group of references between that reuse may occur. */ |
| 224 | |
| 225 struct mem_ref_group | |
| 226 { | |
| 227 tree base; /* Base of the reference. */ | |
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228 tree step; /* Step of the reference. */ |
| 0 | 229 struct mem_ref *refs; /* References in the group. */ |
| 230 struct mem_ref_group *next; /* Next group of references. */ | |
| 111 | 231 unsigned int uid; /* Group UID, used only for debugging. */ |
| 0 | 232 }; |
| 233 | |
| 234 /* Assigned to PREFETCH_BEFORE when all iterations are to be prefetched. */ | |
| 235 | |
| 111 | 236 #define PREFETCH_ALL HOST_WIDE_INT_M1U |
| 0 | 237 |
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238 /* Do not generate a prefetch if the unroll factor is significantly less |
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239 than what is required by the prefetch. This is to avoid redundant |
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240 prefetches. For example, when prefetch_mod is 16 and unroll_factor is |
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241 2, prefetching requires unrolling the loop 16 times, but |
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242 the loop is actually unrolled twice. In this case (ratio = 8), |
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243 prefetching is not likely to be beneficial. */ |
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244 |
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245 #ifndef PREFETCH_MOD_TO_UNROLL_FACTOR_RATIO |
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246 #define PREFETCH_MOD_TO_UNROLL_FACTOR_RATIO 4 |
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247 #endif |
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248 |
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249 /* Some of the prefetch computations have quadratic complexity. We want to |
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250 avoid huge compile times and, therefore, want to limit the amount of |
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251 memory references per loop where we consider prefetching. */ |
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252 |
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253 #ifndef PREFETCH_MAX_MEM_REFS_PER_LOOP |
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254 #define PREFETCH_MAX_MEM_REFS_PER_LOOP 200 |
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255 #endif |
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256 |
| 0 | 257 /* The memory reference. */ |
| 258 | |
| 259 struct mem_ref | |
| 260 { | |
| 111 | 261 gimple *stmt; /* Statement in that the reference appears. */ |
| 0 | 262 tree mem; /* The reference. */ |
| 263 HOST_WIDE_INT delta; /* Constant offset of the reference. */ | |
| 264 struct mem_ref_group *group; /* The group of references it belongs to. */ | |
| 265 unsigned HOST_WIDE_INT prefetch_mod; | |
| 266 /* Prefetch only each PREFETCH_MOD-th | |
| 267 iteration. */ | |
| 268 unsigned HOST_WIDE_INT prefetch_before; | |
| 269 /* Prefetch only first PREFETCH_BEFORE | |
| 270 iterations. */ | |
| 271 unsigned reuse_distance; /* The amount of data accessed before the first | |
| 272 reuse of this value. */ | |
| 273 struct mem_ref *next; /* The next reference in the group. */ | |
| 111 | 274 unsigned int uid; /* Ref UID, used only for debugging. */ |
| 0 | 275 unsigned write_p : 1; /* Is it a write? */ |
| 276 unsigned independent_p : 1; /* True if the reference is independent on | |
| 277 all other references inside the loop. */ | |
| 278 unsigned issue_prefetch_p : 1; /* Should we really issue the prefetch? */ | |
| 279 unsigned storent_p : 1; /* True if we changed the store to a | |
| 280 nontemporal one. */ | |
| 281 }; | |
| 282 | |
| 111 | 283 /* Dumps information about memory reference */ |
| 284 static void | |
| 285 dump_mem_details (FILE *file, tree base, tree step, | |
| 286 HOST_WIDE_INT delta, bool write_p) | |
| 287 { | |
| 288 fprintf (file, "(base "); | |
| 289 print_generic_expr (file, base, TDF_SLIM); | |
| 290 fprintf (file, ", step "); | |
| 291 if (cst_and_fits_in_hwi (step)) | |
| 292 fprintf (file, HOST_WIDE_INT_PRINT_DEC, int_cst_value (step)); | |
| 293 else | |
| 294 print_generic_expr (file, step, TDF_SLIM); | |
| 295 fprintf (file, ")\n"); | |
| 296 fprintf (file, " delta " HOST_WIDE_INT_PRINT_DEC "\n", delta); | |
| 297 fprintf (file, " %s\n\n", write_p ? "write" : "read"); | |
| 298 } | |
| 299 | |
| 0 | 300 /* Dumps information about reference REF to FILE. */ |
| 301 | |
| 302 static void | |
| 303 dump_mem_ref (FILE *file, struct mem_ref *ref) | |
| 304 { | |
| 111 | 305 fprintf (file, "reference %u:%u (", ref->group->uid, ref->uid); |
| 306 print_generic_expr (file, ref->mem, TDF_SLIM); | |
| 0 | 307 fprintf (file, ")\n"); |
| 308 } | |
| 309 | |
| 310 /* Finds a group with BASE and STEP in GROUPS, or creates one if it does not | |
| 311 exist. */ | |
| 312 | |
| 313 static struct mem_ref_group * | |
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314 find_or_create_group (struct mem_ref_group **groups, tree base, tree step) |
| 0 | 315 { |
| 111 | 316 /* Global count for setting struct mem_ref_group->uid. */ |
| 317 static unsigned int last_mem_ref_group_uid = 0; | |
| 318 | |
| 0 | 319 struct mem_ref_group *group; |
| 320 | |
| 321 for (; *groups; groups = &(*groups)->next) | |
| 322 { | |
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323 if (operand_equal_p ((*groups)->step, step, 0) |
| 0 | 324 && operand_equal_p ((*groups)->base, base, 0)) |
| 325 return *groups; | |
| 326 | |
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327 /* If step is an integer constant, keep the list of groups sorted |
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328 by decreasing step. */ |
| 111 | 329 if (cst_and_fits_in_hwi ((*groups)->step) && cst_and_fits_in_hwi (step) |
| 330 && int_cst_value ((*groups)->step) < int_cst_value (step)) | |
| 0 | 331 break; |
| 332 } | |
| 333 | |
| 334 group = XNEW (struct mem_ref_group); | |
| 335 group->base = base; | |
| 336 group->step = step; | |
| 337 group->refs = NULL; | |
| 111 | 338 group->uid = ++last_mem_ref_group_uid; |
| 0 | 339 group->next = *groups; |
| 340 *groups = group; | |
| 341 | |
| 342 return group; | |
| 343 } | |
| 344 | |
| 345 /* Records a memory reference MEM in GROUP with offset DELTA and write status | |
| 346 WRITE_P. The reference occurs in statement STMT. */ | |
| 347 | |
| 348 static void | |
| 111 | 349 record_ref (struct mem_ref_group *group, gimple *stmt, tree mem, |
| 0 | 350 HOST_WIDE_INT delta, bool write_p) |
| 351 { | |
| 111 | 352 unsigned int last_mem_ref_uid = 0; |
| 0 | 353 struct mem_ref **aref; |
| 354 | |
| 355 /* Do not record the same address twice. */ | |
| 356 for (aref = &group->refs; *aref; aref = &(*aref)->next) | |
| 357 { | |
| 111 | 358 last_mem_ref_uid = (*aref)->uid; |
| 359 | |
| 0 | 360 /* It does not have to be possible for write reference to reuse the read |
| 361 prefetch, or vice versa. */ | |
| 362 if (!WRITE_CAN_USE_READ_PREFETCH | |
| 363 && write_p | |
| 364 && !(*aref)->write_p) | |
| 365 continue; | |
| 366 if (!READ_CAN_USE_WRITE_PREFETCH | |
| 367 && !write_p | |
| 368 && (*aref)->write_p) | |
| 369 continue; | |
| 370 | |
| 371 if ((*aref)->delta == delta) | |
| 372 return; | |
| 373 } | |
| 374 | |
| 375 (*aref) = XNEW (struct mem_ref); | |
| 376 (*aref)->stmt = stmt; | |
| 377 (*aref)->mem = mem; | |
| 378 (*aref)->delta = delta; | |
| 379 (*aref)->write_p = write_p; | |
| 380 (*aref)->prefetch_before = PREFETCH_ALL; | |
| 381 (*aref)->prefetch_mod = 1; | |
| 382 (*aref)->reuse_distance = 0; | |
| 383 (*aref)->issue_prefetch_p = false; | |
| 384 (*aref)->group = group; | |
| 385 (*aref)->next = NULL; | |
| 386 (*aref)->independent_p = false; | |
| 387 (*aref)->storent_p = false; | |
| 111 | 388 (*aref)->uid = last_mem_ref_uid + 1; |
| 0 | 389 |
| 390 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 111 | 391 { |
| 392 dump_mem_ref (dump_file, *aref); | |
| 393 | |
| 394 fprintf (dump_file, " group %u ", group->uid); | |
| 395 dump_mem_details (dump_file, group->base, group->step, delta, | |
| 396 write_p); | |
| 397 } | |
| 0 | 398 } |
| 399 | |
| 400 /* Release memory references in GROUPS. */ | |
| 401 | |
| 402 static void | |
| 403 release_mem_refs (struct mem_ref_group *groups) | |
| 404 { | |
| 405 struct mem_ref_group *next_g; | |
| 406 struct mem_ref *ref, *next_r; | |
| 407 | |
| 408 for (; groups; groups = next_g) | |
| 409 { | |
| 410 next_g = groups->next; | |
| 411 for (ref = groups->refs; ref; ref = next_r) | |
| 412 { | |
| 413 next_r = ref->next; | |
| 414 free (ref); | |
| 415 } | |
| 416 free (groups); | |
| 417 } | |
| 418 } | |
| 419 | |
| 420 /* A structure used to pass arguments to idx_analyze_ref. */ | |
| 421 | |
| 422 struct ar_data | |
| 423 { | |
| 424 struct loop *loop; /* Loop of the reference. */ | |
| 111 | 425 gimple *stmt; /* Statement of the reference. */ |
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426 tree *step; /* Step of the memory reference. */ |
| 0 | 427 HOST_WIDE_INT *delta; /* Offset of the memory reference. */ |
| 428 }; | |
| 429 | |
| 430 /* Analyzes a single INDEX of a memory reference to obtain information | |
| 431 described at analyze_ref. Callback for for_each_index. */ | |
| 432 | |
| 433 static bool | |
| 434 idx_analyze_ref (tree base, tree *index, void *data) | |
| 435 { | |
| 436 struct ar_data *ar_data = (struct ar_data *) data; | |
| 437 tree ibase, step, stepsize; | |
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438 HOST_WIDE_INT idelta = 0, imult = 1; |
| 0 | 439 affine_iv iv; |
| 440 | |
| 441 if (!simple_iv (ar_data->loop, loop_containing_stmt (ar_data->stmt), | |
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442 *index, &iv, true)) |
| 0 | 443 return false; |
| 444 ibase = iv.base; | |
| 445 step = iv.step; | |
| 446 | |
| 447 if (TREE_CODE (ibase) == POINTER_PLUS_EXPR | |
| 448 && cst_and_fits_in_hwi (TREE_OPERAND (ibase, 1))) | |
| 449 { | |
| 450 idelta = int_cst_value (TREE_OPERAND (ibase, 1)); | |
| 451 ibase = TREE_OPERAND (ibase, 0); | |
| 452 } | |
| 453 if (cst_and_fits_in_hwi (ibase)) | |
| 454 { | |
| 455 idelta += int_cst_value (ibase); | |
| 456 ibase = build_int_cst (TREE_TYPE (ibase), 0); | |
| 457 } | |
| 458 | |
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459 if (TREE_CODE (base) == ARRAY_REF) |
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460 { |
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461 stepsize = array_ref_element_size (base); |
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462 if (!cst_and_fits_in_hwi (stepsize)) |
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463 return false; |
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464 imult = int_cst_value (stepsize); |
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465 step = fold_build2 (MULT_EXPR, sizetype, |
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466 fold_convert (sizetype, step), |
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467 fold_convert (sizetype, stepsize)); |
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468 idelta *= imult; |
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469 } |
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470 |
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471 if (*ar_data->step == NULL_TREE) |
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472 *ar_data->step = step; |
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473 else |
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474 *ar_data->step = fold_build2 (PLUS_EXPR, sizetype, |
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475 fold_convert (sizetype, *ar_data->step), |
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476 fold_convert (sizetype, step)); |
| 0 | 477 *ar_data->delta += idelta; |
| 478 *index = ibase; | |
| 479 | |
| 480 return true; | |
| 481 } | |
| 482 | |
| 483 /* Tries to express REF_P in shape &BASE + STEP * iter + DELTA, where DELTA and | |
| 484 STEP are integer constants and iter is number of iterations of LOOP. The | |
| 485 reference occurs in statement STMT. Strips nonaddressable component | |
| 486 references from REF_P. */ | |
| 487 | |
| 488 static bool | |
| 489 analyze_ref (struct loop *loop, tree *ref_p, tree *base, | |
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490 tree *step, HOST_WIDE_INT *delta, |
| 111 | 491 gimple *stmt) |
| 0 | 492 { |
| 493 struct ar_data ar_data; | |
| 494 tree off; | |
| 495 HOST_WIDE_INT bit_offset; | |
| 496 tree ref = *ref_p; | |
| 497 | |
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498 *step = NULL_TREE; |
| 0 | 499 *delta = 0; |
| 500 | |
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501 /* First strip off the component references. Ignore bitfields. |
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502 Also strip off the real and imagine parts of a complex, so that |
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503 they can have the same base. */ |
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504 if (TREE_CODE (ref) == REALPART_EXPR |
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505 || TREE_CODE (ref) == IMAGPART_EXPR |
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506 || (TREE_CODE (ref) == COMPONENT_REF |
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507 && DECL_NONADDRESSABLE_P (TREE_OPERAND (ref, 1)))) |
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508 { |
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509 if (TREE_CODE (ref) == IMAGPART_EXPR) |
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510 *delta += int_size_in_bytes (TREE_TYPE (ref)); |
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511 ref = TREE_OPERAND (ref, 0); |
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512 } |
| 0 | 513 |
| 514 *ref_p = ref; | |
| 515 | |
| 516 for (; TREE_CODE (ref) == COMPONENT_REF; ref = TREE_OPERAND (ref, 0)) | |
| 517 { | |
| 518 off = DECL_FIELD_BIT_OFFSET (TREE_OPERAND (ref, 1)); | |
| 519 bit_offset = TREE_INT_CST_LOW (off); | |
| 520 gcc_assert (bit_offset % BITS_PER_UNIT == 0); | |
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521 |
| 0 | 522 *delta += bit_offset / BITS_PER_UNIT; |
| 523 } | |
| 524 | |
| 525 *base = unshare_expr (ref); | |
| 526 ar_data.loop = loop; | |
| 527 ar_data.stmt = stmt; | |
| 528 ar_data.step = step; | |
| 529 ar_data.delta = delta; | |
| 530 return for_each_index (base, idx_analyze_ref, &ar_data); | |
| 531 } | |
| 532 | |
| 533 /* Record a memory reference REF to the list REFS. The reference occurs in | |
| 534 LOOP in statement STMT and it is write if WRITE_P. Returns true if the | |
| 535 reference was recorded, false otherwise. */ | |
| 536 | |
| 537 static bool | |
| 538 gather_memory_references_ref (struct loop *loop, struct mem_ref_group **refs, | |
| 111 | 539 tree ref, bool write_p, gimple *stmt) |
| 0 | 540 { |
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541 tree base, step; |
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542 HOST_WIDE_INT delta; |
| 0 | 543 struct mem_ref_group *agrp; |
| 544 | |
| 545 if (get_base_address (ref) == NULL) | |
| 546 return false; | |
| 547 | |
| 548 if (!analyze_ref (loop, &ref, &base, &step, &delta, stmt)) | |
| 549 return false; | |
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550 /* If analyze_ref fails the default is a NULL_TREE. We can stop here. */ |
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551 if (step == NULL_TREE) |
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552 return false; |
| 0 | 553 |
|
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554 /* Stop if the address of BASE could not be taken. */ |
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555 if (may_be_nonaddressable_p (base)) |
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556 return false; |
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557 |
| 111 | 558 /* Limit non-constant step prefetching only to the innermost loops and |
| 559 only when the step is loop invariant in the entire loop nest. */ | |
| 560 if (!cst_and_fits_in_hwi (step)) | |
| 561 { | |
| 562 if (loop->inner != NULL) | |
| 563 { | |
| 564 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 565 { | |
| 566 fprintf (dump_file, "Memory expression %p\n",(void *) ref ); | |
| 567 print_generic_expr (dump_file, ref, TDF_SLIM); | |
| 568 fprintf (dump_file,":"); | |
| 569 dump_mem_details (dump_file, base, step, delta, write_p); | |
| 570 fprintf (dump_file, | |
| 571 "Ignoring %p, non-constant step prefetching is " | |
| 572 "limited to inner most loops \n", | |
| 573 (void *) ref); | |
| 574 } | |
| 575 return false; | |
| 576 } | |
| 577 else | |
| 578 { | |
| 579 if (!expr_invariant_in_loop_p (loop_outermost (loop), step)) | |
| 580 { | |
| 581 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 582 { | |
| 583 fprintf (dump_file, "Memory expression %p\n",(void *) ref ); | |
| 584 print_generic_expr (dump_file, ref, TDF_SLIM); | |
| 585 fprintf (dump_file,":"); | |
| 586 dump_mem_details (dump_file, base, step, delta, write_p); | |
| 587 fprintf (dump_file, | |
| 588 "Not prefetching, ignoring %p due to " | |
| 589 "loop variant step\n", | |
| 590 (void *) ref); | |
| 591 } | |
| 592 return false; | |
| 593 } | |
| 594 } | |
| 595 } | |
|
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596 |
| 0 | 597 /* Now we know that REF = &BASE + STEP * iter + DELTA, where DELTA and STEP |
| 598 are integer constants. */ | |
| 599 agrp = find_or_create_group (refs, base, step); | |
| 600 record_ref (agrp, stmt, ref, delta, write_p); | |
| 601 | |
| 602 return true; | |
| 603 } | |
| 604 | |
| 605 /* Record the suitable memory references in LOOP. NO_OTHER_REFS is set to | |
| 606 true if there are no other memory references inside the loop. */ | |
| 607 | |
| 608 static struct mem_ref_group * | |
|
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609 gather_memory_references (struct loop *loop, bool *no_other_refs, unsigned *ref_count) |
| 0 | 610 { |
| 611 basic_block *body = get_loop_body_in_dom_order (loop); | |
| 612 basic_block bb; | |
| 613 unsigned i; | |
| 614 gimple_stmt_iterator bsi; | |
| 111 | 615 gimple *stmt; |
| 0 | 616 tree lhs, rhs; |
| 617 struct mem_ref_group *refs = NULL; | |
| 618 | |
| 619 *no_other_refs = true; | |
|
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620 *ref_count = 0; |
| 0 | 621 |
| 622 /* Scan the loop body in order, so that the former references precede the | |
| 623 later ones. */ | |
| 624 for (i = 0; i < loop->num_nodes; i++) | |
| 625 { | |
| 626 bb = body[i]; | |
| 627 if (bb->loop_father != loop) | |
| 628 continue; | |
| 629 | |
| 630 for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi)) | |
| 631 { | |
| 632 stmt = gsi_stmt (bsi); | |
| 633 | |
| 634 if (gimple_code (stmt) != GIMPLE_ASSIGN) | |
| 635 { | |
|
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636 if (gimple_vuse (stmt) |
| 0 | 637 || (is_gimple_call (stmt) |
| 638 && !(gimple_call_flags (stmt) & ECF_CONST))) | |
| 639 *no_other_refs = false; | |
| 640 continue; | |
| 641 } | |
| 642 | |
| 111 | 643 if (! gimple_vuse (stmt)) |
| 644 continue; | |
| 645 | |
| 0 | 646 lhs = gimple_assign_lhs (stmt); |
| 647 rhs = gimple_assign_rhs1 (stmt); | |
| 648 | |
| 649 if (REFERENCE_CLASS_P (rhs)) | |
|
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650 { |
| 0 | 651 *no_other_refs &= gather_memory_references_ref (loop, &refs, |
| 652 rhs, false, stmt); | |
|
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653 *ref_count += 1; |
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654 } |
| 0 | 655 if (REFERENCE_CLASS_P (lhs)) |
|
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656 { |
| 0 | 657 *no_other_refs &= gather_memory_references_ref (loop, &refs, |
| 658 lhs, true, stmt); | |
|
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659 *ref_count += 1; |
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660 } |
| 0 | 661 } |
| 662 } | |
| 663 free (body); | |
| 664 | |
| 665 return refs; | |
| 666 } | |
| 667 | |
| 668 /* Prune the prefetch candidate REF using the self-reuse. */ | |
| 669 | |
| 670 static void | |
| 671 prune_ref_by_self_reuse (struct mem_ref *ref) | |
| 672 { | |
|
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673 HOST_WIDE_INT step; |
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674 bool backward; |
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675 |
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676 /* If the step size is non constant, we cannot calculate prefetch_mod. */ |
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677 if (!cst_and_fits_in_hwi (ref->group->step)) |
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678 return; |
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679 |
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680 step = int_cst_value (ref->group->step); |
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681 |
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682 backward = step < 0; |
| 0 | 683 |
| 684 if (step == 0) | |
| 685 { | |
| 686 /* Prefetch references to invariant address just once. */ | |
| 687 ref->prefetch_before = 1; | |
| 688 return; | |
| 689 } | |
| 690 | |
| 691 if (backward) | |
| 692 step = -step; | |
| 693 | |
| 694 if (step > PREFETCH_BLOCK) | |
| 695 return; | |
| 696 | |
| 697 if ((backward && HAVE_BACKWARD_PREFETCH) | |
| 698 || (!backward && HAVE_FORWARD_PREFETCH)) | |
| 699 { | |
| 700 ref->prefetch_before = 1; | |
| 701 return; | |
| 702 } | |
| 703 | |
| 704 ref->prefetch_mod = PREFETCH_BLOCK / step; | |
| 705 } | |
| 706 | |
| 707 /* Divides X by BY, rounding down. */ | |
| 708 | |
| 709 static HOST_WIDE_INT | |
| 710 ddown (HOST_WIDE_INT x, unsigned HOST_WIDE_INT by) | |
| 711 { | |
| 712 gcc_assert (by > 0); | |
| 713 | |
| 714 if (x >= 0) | |
| 111 | 715 return x / (HOST_WIDE_INT) by; |
| 0 | 716 else |
| 111 | 717 return (x + (HOST_WIDE_INT) by - 1) / (HOST_WIDE_INT) by; |
| 0 | 718 } |
| 719 | |
|
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720 /* Given a CACHE_LINE_SIZE and two inductive memory references |
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721 with a common STEP greater than CACHE_LINE_SIZE and an address |
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722 difference DELTA, compute the probability that they will fall |
|
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723 in different cache lines. Return true if the computed miss rate |
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724 is not greater than the ACCEPTABLE_MISS_RATE. DISTINCT_ITERS is the |
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725 number of distinct iterations after which the pattern repeats itself. |
|
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726 ALIGN_UNIT is the unit of alignment in bytes. */ |
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727 |
|
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728 static bool |
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729 is_miss_rate_acceptable (unsigned HOST_WIDE_INT cache_line_size, |
|
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730 HOST_WIDE_INT step, HOST_WIDE_INT delta, |
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731 unsigned HOST_WIDE_INT distinct_iters, |
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732 int align_unit) |
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733 { |
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734 unsigned align, iter; |
|
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735 int total_positions, miss_positions, max_allowed_miss_positions; |
|
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736 int address1, address2, cache_line1, cache_line2; |
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737 |
|
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738 /* It always misses if delta is greater than or equal to the cache |
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739 line size. */ |
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740 if (delta >= (HOST_WIDE_INT) cache_line_size) |
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741 return false; |
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|
742 |
|
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743 miss_positions = 0; |
|
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744 total_positions = (cache_line_size / align_unit) * distinct_iters; |
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745 max_allowed_miss_positions = (ACCEPTABLE_MISS_RATE * total_positions) / 1000; |
|
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746 |
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747 /* Iterate through all possible alignments of the first |
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748 memory reference within its cache line. */ |
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749 for (align = 0; align < cache_line_size; align += align_unit) |
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|
750 |
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751 /* Iterate through all distinct iterations. */ |
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752 for (iter = 0; iter < distinct_iters; iter++) |
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753 { |
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754 address1 = align + step * iter; |
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755 address2 = address1 + delta; |
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|
756 cache_line1 = address1 / cache_line_size; |
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757 cache_line2 = address2 / cache_line_size; |
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758 if (cache_line1 != cache_line2) |
|
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759 { |
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760 miss_positions += 1; |
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761 if (miss_positions > max_allowed_miss_positions) |
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762 return false; |
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763 } |
|
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764 } |
|
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765 return true; |
|
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766 } |
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767 |
| 0 | 768 /* Prune the prefetch candidate REF using the reuse with BY. |
| 769 If BY_IS_BEFORE is true, BY is before REF in the loop. */ | |
| 770 | |
| 771 static void | |
| 772 prune_ref_by_group_reuse (struct mem_ref *ref, struct mem_ref *by, | |
| 773 bool by_is_before) | |
| 774 { | |
|
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775 HOST_WIDE_INT step; |
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776 bool backward; |
| 0 | 777 HOST_WIDE_INT delta_r = ref->delta, delta_b = by->delta; |
| 778 HOST_WIDE_INT delta = delta_b - delta_r; | |
| 779 HOST_WIDE_INT hit_from; | |
| 780 unsigned HOST_WIDE_INT prefetch_before, prefetch_block; | |
|
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781 HOST_WIDE_INT reduced_step; |
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782 unsigned HOST_WIDE_INT reduced_prefetch_block; |
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783 tree ref_type; |
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784 int align_unit; |
| 0 | 785 |
|
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786 /* If the step is non constant we cannot calculate prefetch_before. */ |
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787 if (!cst_and_fits_in_hwi (ref->group->step)) { |
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788 return; |
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789 } |
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790 |
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791 step = int_cst_value (ref->group->step); |
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792 |
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793 backward = step < 0; |
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794 |
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795 |
| 0 | 796 if (delta == 0) |
| 797 { | |
| 798 /* If the references has the same address, only prefetch the | |
| 799 former. */ | |
| 800 if (by_is_before) | |
| 801 ref->prefetch_before = 0; | |
|
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802 |
| 0 | 803 return; |
| 804 } | |
| 805 | |
| 806 if (!step) | |
| 807 { | |
| 808 /* If the reference addresses are invariant and fall into the | |
| 809 same cache line, prefetch just the first one. */ | |
| 810 if (!by_is_before) | |
| 811 return; | |
| 812 | |
| 813 if (ddown (ref->delta, PREFETCH_BLOCK) | |
| 814 != ddown (by->delta, PREFETCH_BLOCK)) | |
| 815 return; | |
| 816 | |
| 817 ref->prefetch_before = 0; | |
| 818 return; | |
| 819 } | |
| 820 | |
| 821 /* Only prune the reference that is behind in the array. */ | |
| 822 if (backward) | |
| 823 { | |
| 824 if (delta > 0) | |
| 825 return; | |
| 826 | |
| 827 /* Transform the data so that we may assume that the accesses | |
| 828 are forward. */ | |
| 829 delta = - delta; | |
| 830 step = -step; | |
| 831 delta_r = PREFETCH_BLOCK - 1 - delta_r; | |
| 832 delta_b = PREFETCH_BLOCK - 1 - delta_b; | |
| 833 } | |
| 834 else | |
| 835 { | |
| 836 if (delta < 0) | |
| 837 return; | |
| 838 } | |
| 839 | |
| 840 /* Check whether the two references are likely to hit the same cache | |
| 841 line, and how distant the iterations in that it occurs are from | |
| 842 each other. */ | |
| 843 | |
| 844 if (step <= PREFETCH_BLOCK) | |
| 845 { | |
| 846 /* The accesses are sure to meet. Let us check when. */ | |
| 847 hit_from = ddown (delta_b, PREFETCH_BLOCK) * PREFETCH_BLOCK; | |
| 848 prefetch_before = (hit_from - delta_r + step - 1) / step; | |
| 849 | |
|
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850 /* Do not reduce prefetch_before if we meet beyond cache size. */ |
| 111 | 851 if (prefetch_before > absu_hwi (L2_CACHE_SIZE_BYTES / step)) |
|
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852 prefetch_before = PREFETCH_ALL; |
| 0 | 853 if (prefetch_before < ref->prefetch_before) |
| 854 ref->prefetch_before = prefetch_before; | |
| 855 | |
| 856 return; | |
| 857 } | |
| 858 | |
|
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859 /* A more complicated case with step > prefetch_block. First reduce |
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860 the ratio between the step and the cache line size to its simplest |
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861 terms. The resulting denominator will then represent the number of |
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862 distinct iterations after which each address will go back to its |
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863 initial location within the cache line. This computation assumes |
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864 that PREFETCH_BLOCK is a power of two. */ |
| 0 | 865 prefetch_block = PREFETCH_BLOCK; |
|
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866 reduced_prefetch_block = prefetch_block; |
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867 reduced_step = step; |
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868 while ((reduced_step & 1) == 0 |
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869 && reduced_prefetch_block > 1) |
| 0 | 870 { |
|
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871 reduced_step >>= 1; |
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872 reduced_prefetch_block >>= 1; |
| 0 | 873 } |
| 874 | |
| 875 prefetch_before = delta / step; | |
| 876 delta %= step; | |
|
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877 ref_type = TREE_TYPE (ref->mem); |
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878 align_unit = TYPE_ALIGN (ref_type) / 8; |
|
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879 if (is_miss_rate_acceptable (prefetch_block, step, delta, |
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880 reduced_prefetch_block, align_unit)) |
| 0 | 881 { |
|
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882 /* Do not reduce prefetch_before if we meet beyond cache size. */ |
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883 if (prefetch_before > L2_CACHE_SIZE_BYTES / PREFETCH_BLOCK) |
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884 prefetch_before = PREFETCH_ALL; |
| 0 | 885 if (prefetch_before < ref->prefetch_before) |
| 886 ref->prefetch_before = prefetch_before; | |
| 887 | |
| 888 return; | |
| 889 } | |
| 890 | |
| 891 /* Try also the following iteration. */ | |
| 892 prefetch_before++; | |
| 893 delta = step - delta; | |
|
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894 if (is_miss_rate_acceptable (prefetch_block, step, delta, |
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895 reduced_prefetch_block, align_unit)) |
| 0 | 896 { |
| 897 if (prefetch_before < ref->prefetch_before) | |
| 898 ref->prefetch_before = prefetch_before; | |
| 899 | |
| 900 return; | |
| 901 } | |
| 902 | |
| 903 /* The ref probably does not reuse by. */ | |
| 904 return; | |
| 905 } | |
| 906 | |
| 907 /* Prune the prefetch candidate REF using the reuses with other references | |
| 908 in REFS. */ | |
| 909 | |
| 910 static void | |
| 911 prune_ref_by_reuse (struct mem_ref *ref, struct mem_ref *refs) | |
| 912 { | |
| 913 struct mem_ref *prune_by; | |
| 914 bool before = true; | |
| 915 | |
| 916 prune_ref_by_self_reuse (ref); | |
| 917 | |
| 918 for (prune_by = refs; prune_by; prune_by = prune_by->next) | |
| 919 { | |
| 920 if (prune_by == ref) | |
| 921 { | |
| 922 before = false; | |
| 923 continue; | |
| 924 } | |
| 925 | |
| 926 if (!WRITE_CAN_USE_READ_PREFETCH | |
| 927 && ref->write_p | |
| 928 && !prune_by->write_p) | |
| 929 continue; | |
| 930 if (!READ_CAN_USE_WRITE_PREFETCH | |
| 931 && !ref->write_p | |
| 932 && prune_by->write_p) | |
| 933 continue; | |
| 934 | |
| 935 prune_ref_by_group_reuse (ref, prune_by, before); | |
| 936 } | |
| 937 } | |
| 938 | |
| 939 /* Prune the prefetch candidates in GROUP using the reuse analysis. */ | |
| 940 | |
| 941 static void | |
| 942 prune_group_by_reuse (struct mem_ref_group *group) | |
| 943 { | |
| 944 struct mem_ref *ref_pruned; | |
| 945 | |
| 946 for (ref_pruned = group->refs; ref_pruned; ref_pruned = ref_pruned->next) | |
| 947 { | |
| 948 prune_ref_by_reuse (ref_pruned, group->refs); | |
| 949 | |
| 950 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 951 { | |
| 111 | 952 dump_mem_ref (dump_file, ref_pruned); |
| 0 | 953 |
| 954 if (ref_pruned->prefetch_before == PREFETCH_ALL | |
| 955 && ref_pruned->prefetch_mod == 1) | |
| 956 fprintf (dump_file, " no restrictions"); | |
| 957 else if (ref_pruned->prefetch_before == 0) | |
| 958 fprintf (dump_file, " do not prefetch"); | |
| 959 else if (ref_pruned->prefetch_before <= ref_pruned->prefetch_mod) | |
| 960 fprintf (dump_file, " prefetch once"); | |
| 961 else | |
| 962 { | |
| 963 if (ref_pruned->prefetch_before != PREFETCH_ALL) | |
| 964 { | |
| 965 fprintf (dump_file, " prefetch before "); | |
| 966 fprintf (dump_file, HOST_WIDE_INT_PRINT_DEC, | |
| 967 ref_pruned->prefetch_before); | |
| 968 } | |
| 969 if (ref_pruned->prefetch_mod != 1) | |
| 970 { | |
| 971 fprintf (dump_file, " prefetch mod "); | |
| 972 fprintf (dump_file, HOST_WIDE_INT_PRINT_DEC, | |
| 973 ref_pruned->prefetch_mod); | |
| 974 } | |
| 975 } | |
| 976 fprintf (dump_file, "\n"); | |
| 977 } | |
| 978 } | |
| 979 } | |
| 980 | |
| 981 /* Prune the list of prefetch candidates GROUPS using the reuse analysis. */ | |
| 982 | |
| 983 static void | |
| 984 prune_by_reuse (struct mem_ref_group *groups) | |
| 985 { | |
| 986 for (; groups; groups = groups->next) | |
| 987 prune_group_by_reuse (groups); | |
| 988 } | |
| 989 | |
| 990 /* Returns true if we should issue prefetch for REF. */ | |
| 991 | |
| 992 static bool | |
| 993 should_issue_prefetch_p (struct mem_ref *ref) | |
| 994 { | |
| 995 /* For now do not issue prefetches for only first few of the | |
| 996 iterations. */ | |
| 997 if (ref->prefetch_before != PREFETCH_ALL) | |
|
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998 { |
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999 if (dump_file && (dump_flags & TDF_DETAILS)) |
| 111 | 1000 fprintf (dump_file, "Ignoring reference %u:%u due to prefetch_before\n", |
| 1001 ref->group->uid, ref->uid); | |
|
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1002 return false; |
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1003 } |
| 0 | 1004 |
| 1005 /* Do not prefetch nontemporal stores. */ | |
| 1006 if (ref->storent_p) | |
|
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1007 { |
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1008 if (dump_file && (dump_flags & TDF_DETAILS)) |
| 111 | 1009 fprintf (dump_file, "Ignoring nontemporal store reference %u:%u\n", ref->group->uid, ref->uid); |
|
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1010 return false; |
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1011 } |
| 0 | 1012 |
| 1013 return true; | |
| 1014 } | |
| 1015 | |
| 1016 /* Decide which of the prefetch candidates in GROUPS to prefetch. | |
| 1017 AHEAD is the number of iterations to prefetch ahead (which corresponds | |
| 1018 to the number of simultaneous instances of one prefetch running at a | |
| 1019 time). UNROLL_FACTOR is the factor by that the loop is going to be | |
| 1020 unrolled. Returns true if there is anything to prefetch. */ | |
| 1021 | |
| 1022 static bool | |
| 1023 schedule_prefetches (struct mem_ref_group *groups, unsigned unroll_factor, | |
| 1024 unsigned ahead) | |
| 1025 { | |
| 1026 unsigned remaining_prefetch_slots, n_prefetches, prefetch_slots; | |
| 1027 unsigned slots_per_prefetch; | |
| 1028 struct mem_ref *ref; | |
| 1029 bool any = false; | |
| 1030 | |
| 1031 /* At most SIMULTANEOUS_PREFETCHES should be running at the same time. */ | |
| 1032 remaining_prefetch_slots = SIMULTANEOUS_PREFETCHES; | |
| 1033 | |
| 1034 /* The prefetch will run for AHEAD iterations of the original loop, i.e., | |
| 1035 AHEAD / UNROLL_FACTOR iterations of the unrolled loop. In each iteration, | |
| 1036 it will need a prefetch slot. */ | |
| 1037 slots_per_prefetch = (ahead + unroll_factor / 2) / unroll_factor; | |
| 1038 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 1039 fprintf (dump_file, "Each prefetch instruction takes %u prefetch slots.\n", | |
| 1040 slots_per_prefetch); | |
| 1041 | |
| 1042 /* For now we just take memory references one by one and issue | |
| 1043 prefetches for as many as possible. The groups are sorted | |
| 1044 starting with the largest step, since the references with | |
| 1045 large step are more likely to cause many cache misses. */ | |
| 1046 | |
| 1047 for (; groups; groups = groups->next) | |
| 1048 for (ref = groups->refs; ref; ref = ref->next) | |
| 1049 { | |
| 1050 if (!should_issue_prefetch_p (ref)) | |
| 1051 continue; | |
| 1052 | |
|
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1053 /* The loop is far from being sufficiently unrolled for this |
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1054 prefetch. Do not generate prefetch to avoid many redudant |
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1055 prefetches. */ |
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1056 if (ref->prefetch_mod / unroll_factor > PREFETCH_MOD_TO_UNROLL_FACTOR_RATIO) |
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1057 continue; |
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1058 |
| 0 | 1059 /* If we need to prefetch the reference each PREFETCH_MOD iterations, |
| 1060 and we unroll the loop UNROLL_FACTOR times, we need to insert | |
| 1061 ceil (UNROLL_FACTOR / PREFETCH_MOD) instructions in each | |
| 1062 iteration. */ | |
| 1063 n_prefetches = ((unroll_factor + ref->prefetch_mod - 1) | |
| 1064 / ref->prefetch_mod); | |
| 1065 prefetch_slots = n_prefetches * slots_per_prefetch; | |
| 1066 | |
| 1067 /* If more than half of the prefetches would be lost anyway, do not | |
| 1068 issue the prefetch. */ | |
| 1069 if (2 * remaining_prefetch_slots < prefetch_slots) | |
| 1070 continue; | |
| 1071 | |
| 111 | 1072 /* Stop prefetching if debug counter is activated. */ |
| 1073 if (!dbg_cnt (prefetch)) | |
| 1074 continue; | |
| 1075 | |
| 0 | 1076 ref->issue_prefetch_p = true; |
| 111 | 1077 if (dump_file && (dump_flags & TDF_DETAILS)) |
| 1078 fprintf (dump_file, "Decided to issue prefetch for reference %u:%u\n", | |
| 1079 ref->group->uid, ref->uid); | |
| 0 | 1080 |
| 1081 if (remaining_prefetch_slots <= prefetch_slots) | |
| 1082 return true; | |
| 1083 remaining_prefetch_slots -= prefetch_slots; | |
| 1084 any = true; | |
| 1085 } | |
| 1086 | |
| 1087 return any; | |
| 1088 } | |
| 1089 | |
|
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1090 /* Return TRUE if no prefetch is going to be generated in the given |
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1091 GROUPS. */ |
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1092 |
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1093 static bool |
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1094 nothing_to_prefetch_p (struct mem_ref_group *groups) |
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1095 { |
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1096 struct mem_ref *ref; |
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1097 |
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1098 for (; groups; groups = groups->next) |
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1099 for (ref = groups->refs; ref; ref = ref->next) |
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1100 if (should_issue_prefetch_p (ref)) |
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1101 return false; |
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1102 |
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1103 return true; |
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1104 } |
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1105 |
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1106 /* Estimate the number of prefetches in the given GROUPS. |
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1107 UNROLL_FACTOR is the factor by which LOOP was unrolled. */ |
| 0 | 1108 |
|
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1109 static int |
|
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1110 estimate_prefetch_count (struct mem_ref_group *groups, unsigned unroll_factor) |
| 0 | 1111 { |
| 1112 struct mem_ref *ref; | |
|
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1113 unsigned n_prefetches; |
|
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1114 int prefetch_count = 0; |
| 0 | 1115 |
| 1116 for (; groups; groups = groups->next) | |
| 1117 for (ref = groups->refs; ref; ref = ref->next) | |
| 1118 if (should_issue_prefetch_p (ref)) | |
|
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1119 { |
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1120 n_prefetches = ((unroll_factor + ref->prefetch_mod - 1) |
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1121 / ref->prefetch_mod); |
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1122 prefetch_count += n_prefetches; |
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1123 } |
| 0 | 1124 |
|
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1125 return prefetch_count; |
| 0 | 1126 } |
| 1127 | |
| 1128 /* Issue prefetches for the reference REF into loop as decided before. | |
| 1129 HEAD is the number of iterations to prefetch ahead. UNROLL_FACTOR | |
| 1130 is the factor by which LOOP was unrolled. */ | |
| 1131 | |
| 1132 static void | |
| 1133 issue_prefetch_ref (struct mem_ref *ref, unsigned unroll_factor, unsigned ahead) | |
| 1134 { | |
| 1135 HOST_WIDE_INT delta; | |
|
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1136 tree addr, addr_base, write_p, local, forward; |
| 111 | 1137 gcall *prefetch; |
| 0 | 1138 gimple_stmt_iterator bsi; |
| 1139 unsigned n_prefetches, ap; | |
| 1140 bool nontemporal = ref->reuse_distance >= L2_CACHE_SIZE_BYTES; | |
| 1141 | |
| 1142 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 111 | 1143 fprintf (dump_file, "Issued%s prefetch for reference %u:%u.\n", |
| 0 | 1144 nontemporal ? " nontemporal" : "", |
| 111 | 1145 ref->group->uid, ref->uid); |
| 0 | 1146 |
| 1147 bsi = gsi_for_stmt (ref->stmt); | |
| 1148 | |
| 1149 n_prefetches = ((unroll_factor + ref->prefetch_mod - 1) | |
| 1150 / ref->prefetch_mod); | |
| 1151 addr_base = build_fold_addr_expr_with_type (ref->mem, ptr_type_node); | |
| 1152 addr_base = force_gimple_operand_gsi (&bsi, unshare_expr (addr_base), | |
| 1153 true, NULL, true, GSI_SAME_STMT); | |
| 1154 write_p = ref->write_p ? integer_one_node : integer_zero_node; | |
|
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1155 local = nontemporal ? integer_zero_node : integer_three_node; |
| 0 | 1156 |
| 1157 for (ap = 0; ap < n_prefetches; ap++) | |
| 1158 { | |
|
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1159 if (cst_and_fits_in_hwi (ref->group->step)) |
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1160 { |
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1161 /* Determine the address to prefetch. */ |
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1162 delta = (ahead + ap * ref->prefetch_mod) * |
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1163 int_cst_value (ref->group->step); |
| 111 | 1164 addr = fold_build_pointer_plus_hwi (addr_base, delta); |
| 1165 addr = force_gimple_operand_gsi (&bsi, unshare_expr (addr), true, | |
| 1166 NULL, true, GSI_SAME_STMT); | |
|
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1167 } |
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1168 else |
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1169 { |
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1170 /* The step size is non-constant but loop-invariant. We use the |
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1171 heuristic to simply prefetch ahead iterations ahead. */ |
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1172 forward = fold_build2 (MULT_EXPR, sizetype, |
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1173 fold_convert (sizetype, ref->group->step), |
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1174 fold_convert (sizetype, size_int (ahead))); |
| 111 | 1175 addr = fold_build_pointer_plus (addr_base, forward); |
|
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1176 addr = force_gimple_operand_gsi (&bsi, unshare_expr (addr), true, |
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1177 NULL, true, GSI_SAME_STMT); |
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1178 } |
| 111 | 1179 |
| 1180 if (addr_base != addr | |
| 1181 && TREE_CODE (addr_base) == SSA_NAME | |
| 1182 && TREE_CODE (addr) == SSA_NAME) | |
| 1183 { | |
| 1184 duplicate_ssa_name_ptr_info (addr, SSA_NAME_PTR_INFO (addr_base)); | |
| 1185 /* As this isn't a plain copy we have to reset alignment | |
| 1186 information. */ | |
| 1187 if (SSA_NAME_PTR_INFO (addr)) | |
| 1188 mark_ptr_info_alignment_unknown (SSA_NAME_PTR_INFO (addr)); | |
| 1189 } | |
| 1190 | |
| 0 | 1191 /* Create the prefetch instruction. */ |
| 111 | 1192 prefetch = gimple_build_call (builtin_decl_explicit (BUILT_IN_PREFETCH), |
| 0 | 1193 3, addr, write_p, local); |
| 1194 gsi_insert_before (&bsi, prefetch, GSI_SAME_STMT); | |
| 1195 } | |
| 1196 } | |
| 1197 | |
| 1198 /* Issue prefetches for the references in GROUPS into loop as decided before. | |
| 1199 HEAD is the number of iterations to prefetch ahead. UNROLL_FACTOR is the | |
| 1200 factor by that LOOP was unrolled. */ | |
| 1201 | |
| 1202 static void | |
| 1203 issue_prefetches (struct mem_ref_group *groups, | |
| 1204 unsigned unroll_factor, unsigned ahead) | |
| 1205 { | |
| 1206 struct mem_ref *ref; | |
| 1207 | |
| 1208 for (; groups; groups = groups->next) | |
| 1209 for (ref = groups->refs; ref; ref = ref->next) | |
| 1210 if (ref->issue_prefetch_p) | |
| 1211 issue_prefetch_ref (ref, unroll_factor, ahead); | |
| 1212 } | |
| 1213 | |
| 1214 /* Returns true if REF is a memory write for that a nontemporal store insn | |
| 1215 can be used. */ | |
| 1216 | |
| 1217 static bool | |
| 1218 nontemporal_store_p (struct mem_ref *ref) | |
| 1219 { | |
| 111 | 1220 machine_mode mode; |
| 0 | 1221 enum insn_code code; |
| 1222 | |
| 1223 /* REF must be a write that is not reused. We require it to be independent | |
| 1224 on all other memory references in the loop, as the nontemporal stores may | |
| 1225 be reordered with respect to other memory references. */ | |
| 1226 if (!ref->write_p | |
| 1227 || !ref->independent_p | |
| 1228 || ref->reuse_distance < L2_CACHE_SIZE_BYTES) | |
| 1229 return false; | |
| 1230 | |
| 1231 /* Check that we have the storent instruction for the mode. */ | |
| 1232 mode = TYPE_MODE (TREE_TYPE (ref->mem)); | |
| 1233 if (mode == BLKmode) | |
| 1234 return false; | |
| 1235 | |
|
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1236 code = optab_handler (storent_optab, mode); |
| 0 | 1237 return code != CODE_FOR_nothing; |
| 1238 } | |
| 1239 | |
| 1240 /* If REF is a nontemporal store, we mark the corresponding modify statement | |
| 1241 and return true. Otherwise, we return false. */ | |
| 1242 | |
| 1243 static bool | |
| 1244 mark_nontemporal_store (struct mem_ref *ref) | |
| 1245 { | |
| 1246 if (!nontemporal_store_p (ref)) | |
| 1247 return false; | |
| 1248 | |
| 1249 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 111 | 1250 fprintf (dump_file, "Marked reference %u:%u as a nontemporal store.\n", |
| 1251 ref->group->uid, ref->uid); | |
| 0 | 1252 |
| 1253 gimple_assign_set_nontemporal_move (ref->stmt, true); | |
| 1254 ref->storent_p = true; | |
| 1255 | |
| 1256 return true; | |
| 1257 } | |
| 1258 | |
| 1259 /* Issue a memory fence instruction after LOOP. */ | |
| 1260 | |
| 1261 static void | |
| 1262 emit_mfence_after_loop (struct loop *loop) | |
| 1263 { | |
| 111 | 1264 vec<edge> exits = get_loop_exit_edges (loop); |
| 0 | 1265 edge exit; |
| 111 | 1266 gcall *call; |
| 0 | 1267 gimple_stmt_iterator bsi; |
| 1268 unsigned i; | |
| 1269 | |
| 111 | 1270 FOR_EACH_VEC_ELT (exits, i, exit) |
| 0 | 1271 { |
| 1272 call = gimple_build_call (FENCE_FOLLOWING_MOVNT, 0); | |
| 1273 | |
| 1274 if (!single_pred_p (exit->dest) | |
| 1275 /* If possible, we prefer not to insert the fence on other paths | |
| 1276 in cfg. */ | |
| 1277 && !(exit->flags & EDGE_ABNORMAL)) | |
| 1278 split_loop_exit_edge (exit); | |
| 1279 bsi = gsi_after_labels (exit->dest); | |
| 1280 | |
| 1281 gsi_insert_before (&bsi, call, GSI_NEW_STMT); | |
| 1282 } | |
| 1283 | |
| 111 | 1284 exits.release (); |
| 0 | 1285 update_ssa (TODO_update_ssa_only_virtuals); |
| 1286 } | |
| 1287 | |
| 1288 /* Returns true if we can use storent in loop, false otherwise. */ | |
| 1289 | |
| 1290 static bool | |
| 1291 may_use_storent_in_loop_p (struct loop *loop) | |
| 1292 { | |
| 1293 bool ret = true; | |
| 1294 | |
| 1295 if (loop->inner != NULL) | |
| 1296 return false; | |
| 1297 | |
| 1298 /* If we must issue a mfence insn after using storent, check that there | |
| 1299 is a suitable place for it at each of the loop exits. */ | |
| 1300 if (FENCE_FOLLOWING_MOVNT != NULL_TREE) | |
| 1301 { | |
| 111 | 1302 vec<edge> exits = get_loop_exit_edges (loop); |
| 0 | 1303 unsigned i; |
| 1304 edge exit; | |
| 1305 | |
| 111 | 1306 FOR_EACH_VEC_ELT (exits, i, exit) |
| 0 | 1307 if ((exit->flags & EDGE_ABNORMAL) |
| 111 | 1308 && exit->dest == EXIT_BLOCK_PTR_FOR_FN (cfun)) |
| 0 | 1309 ret = false; |
| 1310 | |
| 111 | 1311 exits.release (); |
| 0 | 1312 } |
| 1313 | |
| 1314 return ret; | |
| 1315 } | |
| 1316 | |
| 1317 /* Marks nontemporal stores in LOOP. GROUPS contains the description of memory | |
| 1318 references in the loop. */ | |
| 1319 | |
| 1320 static void | |
| 1321 mark_nontemporal_stores (struct loop *loop, struct mem_ref_group *groups) | |
| 1322 { | |
| 1323 struct mem_ref *ref; | |
| 1324 bool any = false; | |
| 1325 | |
| 1326 if (!may_use_storent_in_loop_p (loop)) | |
| 1327 return; | |
| 1328 | |
| 1329 for (; groups; groups = groups->next) | |
| 1330 for (ref = groups->refs; ref; ref = ref->next) | |
| 1331 any |= mark_nontemporal_store (ref); | |
| 1332 | |
| 1333 if (any && FENCE_FOLLOWING_MOVNT != NULL_TREE) | |
| 1334 emit_mfence_after_loop (loop); | |
| 1335 } | |
| 1336 | |
| 1337 /* Determines whether we can profitably unroll LOOP FACTOR times, and if | |
| 1338 this is the case, fill in DESC by the description of number of | |
| 1339 iterations. */ | |
| 1340 | |
| 1341 static bool | |
| 1342 should_unroll_loop_p (struct loop *loop, struct tree_niter_desc *desc, | |
| 1343 unsigned factor) | |
| 1344 { | |
| 1345 if (!can_unroll_loop_p (loop, factor, desc)) | |
| 1346 return false; | |
| 1347 | |
| 1348 /* We only consider loops without control flow for unrolling. This is not | |
| 1349 a hard restriction -- tree_unroll_loop works with arbitrary loops | |
| 1350 as well; but the unrolling/prefetching is usually more profitable for | |
| 1351 loops consisting of a single basic block, and we want to limit the | |
| 1352 code growth. */ | |
| 1353 if (loop->num_nodes > 2) | |
| 1354 return false; | |
| 1355 | |
| 1356 return true; | |
| 1357 } | |
| 1358 | |
| 1359 /* Determine the coefficient by that unroll LOOP, from the information | |
| 1360 contained in the list of memory references REFS. Description of | |
| 111 | 1361 number of iterations of LOOP is stored to DESC. NINSNS is the number of |
| 0 | 1362 insns of the LOOP. EST_NITER is the estimated number of iterations of |
| 1363 the loop, or -1 if no estimate is available. */ | |
| 1364 | |
| 1365 static unsigned | |
| 1366 determine_unroll_factor (struct loop *loop, struct mem_ref_group *refs, | |
| 1367 unsigned ninsns, struct tree_niter_desc *desc, | |
| 1368 HOST_WIDE_INT est_niter) | |
| 1369 { | |
| 1370 unsigned upper_bound; | |
| 1371 unsigned nfactor, factor, mod_constraint; | |
| 1372 struct mem_ref_group *agp; | |
| 1373 struct mem_ref *ref; | |
| 1374 | |
| 1375 /* First check whether the loop is not too large to unroll. We ignore | |
| 1376 PARAM_MAX_UNROLL_TIMES, because for small loops, it prevented us | |
| 1377 from unrolling them enough to make exactly one cache line covered by each | |
| 1378 iteration. Also, the goal of PARAM_MAX_UNROLL_TIMES is to prevent | |
| 1379 us from unrolling the loops too many times in cases where we only expect | |
| 1380 gains from better scheduling and decreasing loop overhead, which is not | |
| 1381 the case here. */ | |
| 1382 upper_bound = PARAM_VALUE (PARAM_MAX_UNROLLED_INSNS) / ninsns; | |
| 1383 | |
| 1384 /* If we unrolled the loop more times than it iterates, the unrolled version | |
| 1385 of the loop would be never entered. */ | |
| 1386 if (est_niter >= 0 && est_niter < (HOST_WIDE_INT) upper_bound) | |
| 1387 upper_bound = est_niter; | |
| 1388 | |
| 1389 if (upper_bound <= 1) | |
| 1390 return 1; | |
| 1391 | |
| 1392 /* Choose the factor so that we may prefetch each cache just once, | |
| 1393 but bound the unrolling by UPPER_BOUND. */ | |
| 1394 factor = 1; | |
| 1395 for (agp = refs; agp; agp = agp->next) | |
| 1396 for (ref = agp->refs; ref; ref = ref->next) | |
| 1397 if (should_issue_prefetch_p (ref)) | |
| 1398 { | |
| 1399 mod_constraint = ref->prefetch_mod; | |
| 1400 nfactor = least_common_multiple (mod_constraint, factor); | |
| 1401 if (nfactor <= upper_bound) | |
| 1402 factor = nfactor; | |
| 1403 } | |
| 1404 | |
| 1405 if (!should_unroll_loop_p (loop, desc, factor)) | |
| 1406 return 1; | |
| 1407 | |
| 1408 return factor; | |
| 1409 } | |
| 1410 | |
| 1411 /* Returns the total volume of the memory references REFS, taking into account | |
| 1412 reuses in the innermost loop and cache line size. TODO -- we should also | |
| 1413 take into account reuses across the iterations of the loops in the loop | |
| 1414 nest. */ | |
| 1415 | |
| 1416 static unsigned | |
| 1417 volume_of_references (struct mem_ref_group *refs) | |
| 1418 { | |
| 1419 unsigned volume = 0; | |
| 1420 struct mem_ref_group *gr; | |
| 1421 struct mem_ref *ref; | |
| 1422 | |
| 1423 for (gr = refs; gr; gr = gr->next) | |
| 1424 for (ref = gr->refs; ref; ref = ref->next) | |
| 1425 { | |
| 1426 /* Almost always reuses another value? */ | |
| 1427 if (ref->prefetch_before != PREFETCH_ALL) | |
| 1428 continue; | |
| 1429 | |
| 1430 /* If several iterations access the same cache line, use the size of | |
| 1431 the line divided by this number. Otherwise, a cache line is | |
| 1432 accessed in each iteration. TODO -- in the latter case, we should | |
| 1433 take the size of the reference into account, rounding it up on cache | |
| 1434 line size multiple. */ | |
| 1435 volume += L1_CACHE_LINE_SIZE / ref->prefetch_mod; | |
| 1436 } | |
| 1437 return volume; | |
| 1438 } | |
| 1439 | |
| 1440 /* Returns the volume of memory references accessed across VEC iterations of | |
| 1441 loops, whose sizes are described in the LOOP_SIZES array. N is the number | |
| 1442 of the loops in the nest (length of VEC and LOOP_SIZES vectors). */ | |
| 1443 | |
| 1444 static unsigned | |
| 1445 volume_of_dist_vector (lambda_vector vec, unsigned *loop_sizes, unsigned n) | |
| 1446 { | |
| 1447 unsigned i; | |
| 1448 | |
| 1449 for (i = 0; i < n; i++) | |
| 1450 if (vec[i] != 0) | |
| 1451 break; | |
| 1452 | |
| 1453 if (i == n) | |
| 1454 return 0; | |
| 1455 | |
| 1456 gcc_assert (vec[i] > 0); | |
| 1457 | |
| 1458 /* We ignore the parts of the distance vector in subloops, since usually | |
| 1459 the numbers of iterations are much smaller. */ | |
| 1460 return loop_sizes[i] * vec[i]; | |
| 1461 } | |
| 1462 | |
| 1463 /* Add the steps of ACCESS_FN multiplied by STRIDE to the array STRIDE | |
| 1464 at the position corresponding to the loop of the step. N is the depth | |
| 1465 of the considered loop nest, and, LOOP is its innermost loop. */ | |
| 1466 | |
| 1467 static void | |
| 1468 add_subscript_strides (tree access_fn, unsigned stride, | |
| 1469 HOST_WIDE_INT *strides, unsigned n, struct loop *loop) | |
| 1470 { | |
| 1471 struct loop *aloop; | |
| 1472 tree step; | |
| 1473 HOST_WIDE_INT astep; | |
| 1474 unsigned min_depth = loop_depth (loop) - n; | |
| 1475 | |
| 1476 while (TREE_CODE (access_fn) == POLYNOMIAL_CHREC) | |
| 1477 { | |
| 1478 aloop = get_chrec_loop (access_fn); | |
| 1479 step = CHREC_RIGHT (access_fn); | |
| 1480 access_fn = CHREC_LEFT (access_fn); | |
| 1481 | |
| 1482 if ((unsigned) loop_depth (aloop) <= min_depth) | |
| 1483 continue; | |
| 1484 | |
| 111 | 1485 if (tree_fits_shwi_p (step)) |
| 1486 astep = tree_to_shwi (step); | |
| 0 | 1487 else |
| 1488 astep = L1_CACHE_LINE_SIZE; | |
| 1489 | |
| 1490 strides[n - 1 - loop_depth (loop) + loop_depth (aloop)] += astep * stride; | |
| 1491 | |
| 1492 } | |
| 1493 } | |
| 1494 | |
| 1495 /* Returns the volume of memory references accessed between two consecutive | |
| 1496 self-reuses of the reference DR. We consider the subscripts of DR in N | |
| 1497 loops, and LOOP_SIZES contains the volumes of accesses in each of the | |
| 1498 loops. LOOP is the innermost loop of the current loop nest. */ | |
| 1499 | |
| 1500 static unsigned | |
| 1501 self_reuse_distance (data_reference_p dr, unsigned *loop_sizes, unsigned n, | |
| 1502 struct loop *loop) | |
| 1503 { | |
| 1504 tree stride, access_fn; | |
| 1505 HOST_WIDE_INT *strides, astride; | |
| 111 | 1506 vec<tree> access_fns; |
| 0 | 1507 tree ref = DR_REF (dr); |
| 1508 unsigned i, ret = ~0u; | |
| 1509 | |
| 1510 /* In the following example: | |
| 1511 | |
| 1512 for (i = 0; i < N; i++) | |
| 1513 for (j = 0; j < N; j++) | |
| 1514 use (a[j][i]); | |
| 1515 the same cache line is accessed each N steps (except if the change from | |
| 1516 i to i + 1 crosses the boundary of the cache line). Thus, for self-reuse, | |
| 1517 we cannot rely purely on the results of the data dependence analysis. | |
| 1518 | |
| 1519 Instead, we compute the stride of the reference in each loop, and consider | |
| 1520 the innermost loop in that the stride is less than cache size. */ | |
| 1521 | |
| 1522 strides = XCNEWVEC (HOST_WIDE_INT, n); | |
| 1523 access_fns = DR_ACCESS_FNS (dr); | |
| 1524 | |
| 111 | 1525 FOR_EACH_VEC_ELT (access_fns, i, access_fn) |
| 0 | 1526 { |
| 1527 /* Keep track of the reference corresponding to the subscript, so that we | |
| 1528 know its stride. */ | |
| 1529 while (handled_component_p (ref) && TREE_CODE (ref) != ARRAY_REF) | |
| 1530 ref = TREE_OPERAND (ref, 0); | |
|
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1531 |
| 0 | 1532 if (TREE_CODE (ref) == ARRAY_REF) |
| 1533 { | |
| 1534 stride = TYPE_SIZE_UNIT (TREE_TYPE (ref)); | |
| 111 | 1535 if (tree_fits_uhwi_p (stride)) |
| 1536 astride = tree_to_uhwi (stride); | |
| 0 | 1537 else |
| 1538 astride = L1_CACHE_LINE_SIZE; | |
| 1539 | |
| 1540 ref = TREE_OPERAND (ref, 0); | |
| 1541 } | |
| 1542 else | |
| 1543 astride = 1; | |
| 1544 | |
| 1545 add_subscript_strides (access_fn, astride, strides, n, loop); | |
| 1546 } | |
| 1547 | |
| 1548 for (i = n; i-- > 0; ) | |
| 1549 { | |
| 1550 unsigned HOST_WIDE_INT s; | |
| 1551 | |
| 1552 s = strides[i] < 0 ? -strides[i] : strides[i]; | |
| 1553 | |
| 1554 if (s < (unsigned) L1_CACHE_LINE_SIZE | |
| 1555 && (loop_sizes[i] | |
| 1556 > (unsigned) (L1_CACHE_SIZE_BYTES / NONTEMPORAL_FRACTION))) | |
| 1557 { | |
| 1558 ret = loop_sizes[i]; | |
| 1559 break; | |
| 1560 } | |
| 1561 } | |
| 1562 | |
| 1563 free (strides); | |
| 1564 return ret; | |
| 1565 } | |
| 1566 | |
| 1567 /* Determines the distance till the first reuse of each reference in REFS | |
| 1568 in the loop nest of LOOP. NO_OTHER_REFS is true if there are no other | |
| 111 | 1569 memory references in the loop. Return false if the analysis fails. */ |
| 0 | 1570 |
| 111 | 1571 static bool |
| 0 | 1572 determine_loop_nest_reuse (struct loop *loop, struct mem_ref_group *refs, |
| 1573 bool no_other_refs) | |
| 1574 { | |
| 1575 struct loop *nest, *aloop; | |
| 111 | 1576 vec<data_reference_p> datarefs = vNULL; |
| 1577 vec<ddr_p> dependences = vNULL; | |
| 0 | 1578 struct mem_ref_group *gr; |
| 1579 struct mem_ref *ref, *refb; | |
| 111 | 1580 auto_vec<loop_p> vloops; |
| 0 | 1581 unsigned *loop_data_size; |
| 1582 unsigned i, j, n; | |
| 1583 unsigned volume, dist, adist; | |
| 1584 HOST_WIDE_INT vol; | |
| 1585 data_reference_p dr; | |
| 1586 ddr_p dep; | |
| 1587 | |
| 1588 if (loop->inner) | |
| 111 | 1589 return true; |
| 0 | 1590 |
| 1591 /* Find the outermost loop of the loop nest of loop (we require that | |
| 1592 there are no sibling loops inside the nest). */ | |
| 1593 nest = loop; | |
| 1594 while (1) | |
| 1595 { | |
| 1596 aloop = loop_outer (nest); | |
| 1597 | |
| 1598 if (aloop == current_loops->tree_root | |
| 1599 || aloop->inner->next) | |
| 1600 break; | |
| 1601 | |
| 1602 nest = aloop; | |
| 1603 } | |
| 1604 | |
| 1605 /* For each loop, determine the amount of data accessed in each iteration. | |
| 1606 We use this to estimate whether the reference is evicted from the | |
| 1607 cache before its reuse. */ | |
| 1608 find_loop_nest (nest, &vloops); | |
| 111 | 1609 n = vloops.length (); |
| 0 | 1610 loop_data_size = XNEWVEC (unsigned, n); |
| 1611 volume = volume_of_references (refs); | |
| 1612 i = n; | |
| 1613 while (i-- != 0) | |
| 1614 { | |
| 1615 loop_data_size[i] = volume; | |
| 1616 /* Bound the volume by the L2 cache size, since above this bound, | |
| 1617 all dependence distances are equivalent. */ | |
| 1618 if (volume > L2_CACHE_SIZE_BYTES) | |
| 1619 continue; | |
| 1620 | |
| 111 | 1621 aloop = vloops[i]; |
| 1622 vol = estimated_stmt_executions_int (aloop); | |
| 1623 if (vol == -1) | |
| 0 | 1624 vol = expected_loop_iterations (aloop); |
| 1625 volume *= vol; | |
| 1626 } | |
| 1627 | |
| 1628 /* Prepare the references in the form suitable for data dependence | |
| 1629 analysis. We ignore unanalyzable data references (the results | |
| 1630 are used just as a heuristics to estimate temporality of the | |
| 1631 references, hence we do not need to worry about correctness). */ | |
| 1632 for (gr = refs; gr; gr = gr->next) | |
| 1633 for (ref = gr->refs; ref; ref = ref->next) | |
| 1634 { | |
| 111 | 1635 dr = create_data_ref (loop_preheader_edge (nest), |
| 1636 loop_containing_stmt (ref->stmt), | |
| 1637 ref->mem, ref->stmt, !ref->write_p, false); | |
| 0 | 1638 |
| 1639 if (dr) | |
| 1640 { | |
| 1641 ref->reuse_distance = volume; | |
| 1642 dr->aux = ref; | |
| 111 | 1643 datarefs.safe_push (dr); |
| 0 | 1644 } |
| 1645 else | |
| 1646 no_other_refs = false; | |
| 1647 } | |
| 1648 | |
| 111 | 1649 FOR_EACH_VEC_ELT (datarefs, i, dr) |
| 0 | 1650 { |
| 1651 dist = self_reuse_distance (dr, loop_data_size, n, loop); | |
| 1652 ref = (struct mem_ref *) dr->aux; | |
| 1653 if (ref->reuse_distance > dist) | |
| 1654 ref->reuse_distance = dist; | |
| 1655 | |
| 1656 if (no_other_refs) | |
| 1657 ref->independent_p = true; | |
| 1658 } | |
| 1659 | |
| 111 | 1660 if (!compute_all_dependences (datarefs, &dependences, vloops, true)) |
| 1661 return false; | |
| 0 | 1662 |
| 111 | 1663 FOR_EACH_VEC_ELT (dependences, i, dep) |
| 0 | 1664 { |
| 1665 if (DDR_ARE_DEPENDENT (dep) == chrec_known) | |
| 1666 continue; | |
| 1667 | |
| 1668 ref = (struct mem_ref *) DDR_A (dep)->aux; | |
| 1669 refb = (struct mem_ref *) DDR_B (dep)->aux; | |
| 1670 | |
| 1671 if (DDR_ARE_DEPENDENT (dep) == chrec_dont_know | |
| 111 | 1672 || DDR_COULD_BE_INDEPENDENT_P (dep) |
| 0 | 1673 || DDR_NUM_DIST_VECTS (dep) == 0) |
| 1674 { | |
| 1675 /* If the dependence cannot be analyzed, assume that there might be | |
| 1676 a reuse. */ | |
| 1677 dist = 0; | |
|
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1678 |
| 0 | 1679 ref->independent_p = false; |
| 1680 refb->independent_p = false; | |
| 1681 } | |
| 1682 else | |
| 1683 { | |
| 1684 /* The distance vectors are normalized to be always lexicographically | |
| 1685 positive, hence we cannot tell just from them whether DDR_A comes | |
| 1686 before DDR_B or vice versa. However, it is not important, | |
| 1687 anyway -- if DDR_A is close to DDR_B, then it is either reused in | |
| 1688 DDR_B (and it is not nontemporal), or it reuses the value of DDR_B | |
| 1689 in cache (and marking it as nontemporal would not affect | |
| 1690 anything). */ | |
| 1691 | |
| 1692 dist = volume; | |
| 1693 for (j = 0; j < DDR_NUM_DIST_VECTS (dep); j++) | |
| 1694 { | |
| 1695 adist = volume_of_dist_vector (DDR_DIST_VECT (dep, j), | |
| 1696 loop_data_size, n); | |
| 1697 | |
| 1698 /* If this is a dependence in the innermost loop (i.e., the | |
| 1699 distances in all superloops are zero) and it is not | |
| 1700 the trivial self-dependence with distance zero, record that | |
| 1701 the references are not completely independent. */ | |
| 1702 if (lambda_vector_zerop (DDR_DIST_VECT (dep, j), n - 1) | |
| 1703 && (ref != refb | |
| 1704 || DDR_DIST_VECT (dep, j)[n-1] != 0)) | |
| 1705 { | |
| 1706 ref->independent_p = false; | |
| 1707 refb->independent_p = false; | |
| 1708 } | |
| 1709 | |
| 1710 /* Ignore accesses closer than | |
| 1711 L1_CACHE_SIZE_BYTES / NONTEMPORAL_FRACTION, | |
| 1712 so that we use nontemporal prefetches e.g. if single memory | |
| 1713 location is accessed several times in a single iteration of | |
| 1714 the loop. */ | |
| 1715 if (adist < L1_CACHE_SIZE_BYTES / NONTEMPORAL_FRACTION) | |
| 1716 continue; | |
| 1717 | |
| 1718 if (adist < dist) | |
| 1719 dist = adist; | |
| 1720 } | |
| 1721 } | |
| 1722 | |
| 1723 if (ref->reuse_distance > dist) | |
| 1724 ref->reuse_distance = dist; | |
| 1725 if (refb->reuse_distance > dist) | |
| 1726 refb->reuse_distance = dist; | |
| 1727 } | |
| 1728 | |
| 1729 free_dependence_relations (dependences); | |
| 1730 free_data_refs (datarefs); | |
| 1731 free (loop_data_size); | |
| 1732 | |
| 1733 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 1734 { | |
| 1735 fprintf (dump_file, "Reuse distances:\n"); | |
| 1736 for (gr = refs; gr; gr = gr->next) | |
| 1737 for (ref = gr->refs; ref; ref = ref->next) | |
| 111 | 1738 fprintf (dump_file, " reference %u:%u distance %u\n", |
| 1739 ref->group->uid, ref->uid, ref->reuse_distance); | |
| 0 | 1740 } |
| 111 | 1741 |
| 1742 return true; | |
| 0 | 1743 } |
| 1744 | |
|
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1745 /* Determine whether or not the trip count to ahead ratio is too small based |
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|
1746 on prefitablility consideration. |
|
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1747 AHEAD: the iteration ahead distance, |
|
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1748 EST_NITER: the estimated trip count. */ |
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1749 |
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1750 static bool |
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1751 trip_count_to_ahead_ratio_too_small_p (unsigned ahead, HOST_WIDE_INT est_niter) |
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1752 { |
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1753 /* Assume trip count to ahead ratio is big enough if the trip count could not |
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1754 be estimated at compile time. */ |
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1755 if (est_niter < 0) |
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1756 return false; |
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1757 |
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1758 if (est_niter < (HOST_WIDE_INT) (TRIP_COUNT_TO_AHEAD_RATIO * ahead)) |
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1759 { |
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1760 if (dump_file && (dump_flags & TDF_DETAILS)) |
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1761 fprintf (dump_file, |
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1762 "Not prefetching -- loop estimated to roll only %d times\n", |
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1763 (int) est_niter); |
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1764 return true; |
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1765 } |
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1766 |
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1767 return false; |
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1768 } |
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1769 |
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|
1770 /* Determine whether or not the number of memory references in the loop is |
|
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|
1771 reasonable based on the profitablity and compilation time considerations. |
|
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|
1772 NINSNS: estimated number of instructions in the loop, |
|
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|
1773 MEM_REF_COUNT: total number of memory references in the loop. */ |
|
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|
1774 |
|
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|
1775 static bool |
|
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|
1776 mem_ref_count_reasonable_p (unsigned ninsns, unsigned mem_ref_count) |
|
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|
1777 { |
|
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|
1778 int insn_to_mem_ratio; |
|
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|
1779 |
|
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|
1780 if (mem_ref_count == 0) |
|
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|
1781 return false; |
|
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|
1782 |
|
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1783 /* Miss rate computation (is_miss_rate_acceptable) and dependence analysis |
|
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|
1784 (compute_all_dependences) have high costs based on quadratic complexity. |
|
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1785 To avoid huge compilation time, we give up prefetching if mem_ref_count |
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1786 is too large. */ |
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1787 if (mem_ref_count > PREFETCH_MAX_MEM_REFS_PER_LOOP) |
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1788 return false; |
|
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|
1789 |
|
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1790 /* Prefetching improves performance by overlapping cache missing |
|
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1791 memory accesses with CPU operations. If the loop does not have |
|
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1792 enough CPU operations to overlap with memory operations, prefetching |
|
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1793 won't give a significant benefit. One approximate way of checking |
|
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|
1794 this is to require the ratio of instructions to memory references to |
|
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|
1795 be above a certain limit. This approximation works well in practice. |
|
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|
1796 TODO: Implement a more precise computation by estimating the time |
|
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|
1797 for each CPU or memory op in the loop. Time estimates for memory ops |
|
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|
1798 should account for cache misses. */ |
|
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1799 insn_to_mem_ratio = ninsns / mem_ref_count; |
|
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|
1800 |
|
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1801 if (insn_to_mem_ratio < PREFETCH_MIN_INSN_TO_MEM_RATIO) |
|
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1802 { |
|
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1803 if (dump_file && (dump_flags & TDF_DETAILS)) |
|
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1804 fprintf (dump_file, |
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1805 "Not prefetching -- instruction to memory reference ratio (%d) too small\n", |
|
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1806 insn_to_mem_ratio); |
|
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1807 return false; |
|
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1808 } |
|
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|
1809 |
|
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1810 return true; |
|
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1811 } |
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1812 |
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1813 /* Determine whether or not the instruction to prefetch ratio in the loop is |
|
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1814 too small based on the profitablity consideration. |
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1815 NINSNS: estimated number of instructions in the loop, |
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1816 PREFETCH_COUNT: an estimate of the number of prefetches, |
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1817 UNROLL_FACTOR: the factor to unroll the loop if prefetching. */ |
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1818 |
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1819 static bool |
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1820 insn_to_prefetch_ratio_too_small_p (unsigned ninsns, unsigned prefetch_count, |
|
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1821 unsigned unroll_factor) |
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1822 { |
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1823 int insn_to_prefetch_ratio; |
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1824 |
|
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1825 /* Prefetching most likely causes performance degradation when the instruction |
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1826 to prefetch ratio is too small. Too many prefetch instructions in a loop |
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1827 may reduce the I-cache performance. |
|
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1828 (unroll_factor * ninsns) is used to estimate the number of instructions in |
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1829 the unrolled loop. This implementation is a bit simplistic -- the number |
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1830 of issued prefetch instructions is also affected by unrolling. So, |
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1831 prefetch_mod and the unroll factor should be taken into account when |
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1832 determining prefetch_count. Also, the number of insns of the unrolled |
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1833 loop will usually be significantly smaller than the number of insns of the |
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1834 original loop * unroll_factor (at least the induction variable increases |
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1835 and the exit branches will get eliminated), so it might be better to use |
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1836 tree_estimate_loop_size + estimated_unrolled_size. */ |
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1837 insn_to_prefetch_ratio = (unroll_factor * ninsns) / prefetch_count; |
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1838 if (insn_to_prefetch_ratio < MIN_INSN_TO_PREFETCH_RATIO) |
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1839 { |
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1840 if (dump_file && (dump_flags & TDF_DETAILS)) |
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|
1841 fprintf (dump_file, |
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1842 "Not prefetching -- instruction to prefetch ratio (%d) too small\n", |
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|
1843 insn_to_prefetch_ratio); |
|
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1844 return true; |
|
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1845 } |
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1846 |
|
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1847 return false; |
|
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1848 } |
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1849 |
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1850 |
| 0 | 1851 /* Issue prefetch instructions for array references in LOOP. Returns |
| 1852 true if the LOOP was unrolled. */ | |
| 1853 | |
| 1854 static bool | |
| 1855 loop_prefetch_arrays (struct loop *loop) | |
| 1856 { | |
| 1857 struct mem_ref_group *refs; | |
| 1858 unsigned ahead, ninsns, time, unroll_factor; | |
| 1859 HOST_WIDE_INT est_niter; | |
| 1860 struct tree_niter_desc desc; | |
| 1861 bool unrolled = false, no_other_refs; | |
|
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1862 unsigned prefetch_count; |
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|
1863 unsigned mem_ref_count; |
| 0 | 1864 |
| 1865 if (optimize_loop_nest_for_size_p (loop)) | |
| 1866 { | |
| 1867 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 1868 fprintf (dump_file, " ignored (cold area)\n"); | |
| 1869 return false; | |
| 1870 } | |
| 1871 | |
|
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1872 /* FIXME: the time should be weighted by the probabilities of the blocks in |
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1873 the loop body. */ |
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1874 time = tree_num_loop_insns (loop, &eni_time_weights); |
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1875 if (time == 0) |
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1876 return false; |
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|
1877 |
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1878 ahead = (PREFETCH_LATENCY + time - 1) / time; |
| 111 | 1879 est_niter = estimated_stmt_executions_int (loop); |
| 1880 if (est_niter == -1) | |
| 1881 est_niter = likely_max_stmt_executions_int (loop); | |
|
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1882 |
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1883 /* Prefetching is not likely to be profitable if the trip count to ahead |
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1884 ratio is too small. */ |
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1885 if (trip_count_to_ahead_ratio_too_small_p (ahead, est_niter)) |
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1886 return false; |
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1887 |
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1888 ninsns = tree_num_loop_insns (loop, &eni_size_weights); |
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1889 |
| 0 | 1890 /* Step 1: gather the memory references. */ |
|
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1891 refs = gather_memory_references (loop, &no_other_refs, &mem_ref_count); |
| 0 | 1892 |
|
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1893 /* Give up prefetching if the number of memory references in the |
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1894 loop is not reasonable based on profitablity and compilation time |
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1895 considerations. */ |
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1896 if (!mem_ref_count_reasonable_p (ninsns, mem_ref_count)) |
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1897 goto fail; |
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1898 |
| 0 | 1899 /* Step 2: estimate the reuse effects. */ |
| 1900 prune_by_reuse (refs); | |
| 1901 | |
|
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1902 if (nothing_to_prefetch_p (refs)) |
| 0 | 1903 goto fail; |
| 1904 | |
| 111 | 1905 if (!determine_loop_nest_reuse (loop, refs, no_other_refs)) |
| 1906 goto fail; | |
| 0 | 1907 |
|
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1908 /* Step 3: determine unroll factor. */ |
| 0 | 1909 unroll_factor = determine_unroll_factor (loop, refs, ninsns, &desc, |
| 1910 est_niter); | |
|
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1911 |
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1912 /* Estimate prefetch count for the unrolled loop. */ |
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1913 prefetch_count = estimate_prefetch_count (refs, unroll_factor); |
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1914 if (prefetch_count == 0) |
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1915 goto fail; |
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1916 |
| 0 | 1917 if (dump_file && (dump_flags & TDF_DETAILS)) |
|
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1918 fprintf (dump_file, "Ahead %d, unroll factor %d, trip count " |
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1919 HOST_WIDE_INT_PRINT_DEC "\n" |
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1920 "insn count %d, mem ref count %d, prefetch count %d\n", |
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1921 ahead, unroll_factor, est_niter, |
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1922 ninsns, mem_ref_count, prefetch_count); |
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1923 |
|
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1924 /* Prefetching is not likely to be profitable if the instruction to prefetch |
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1925 ratio is too small. */ |
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1926 if (insn_to_prefetch_ratio_too_small_p (ninsns, prefetch_count, |
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1927 unroll_factor)) |
|
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1928 goto fail; |
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1929 |
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1930 mark_nontemporal_stores (loop, refs); |
| 0 | 1931 |
| 1932 /* Step 4: what to prefetch? */ | |
| 1933 if (!schedule_prefetches (refs, unroll_factor, ahead)) | |
| 1934 goto fail; | |
| 1935 | |
| 1936 /* Step 5: unroll the loop. TODO -- peeling of first and last few | |
| 1937 iterations so that we do not issue superfluous prefetches. */ | |
| 1938 if (unroll_factor != 1) | |
| 1939 { | |
| 1940 tree_unroll_loop (loop, unroll_factor, | |
| 1941 single_dom_exit (loop), &desc); | |
| 1942 unrolled = true; | |
| 1943 } | |
| 1944 | |
| 1945 /* Step 6: issue the prefetches. */ | |
| 1946 issue_prefetches (refs, unroll_factor, ahead); | |
| 1947 | |
| 1948 fail: | |
| 1949 release_mem_refs (refs); | |
| 1950 return unrolled; | |
| 1951 } | |
| 1952 | |
| 1953 /* Issue prefetch instructions for array references in loops. */ | |
| 1954 | |
| 1955 unsigned int | |
| 1956 tree_ssa_prefetch_arrays (void) | |
| 1957 { | |
| 1958 struct loop *loop; | |
| 1959 bool unrolled = false; | |
| 1960 int todo_flags = 0; | |
| 1961 | |
| 111 | 1962 if (!targetm.have_prefetch () |
| 0 | 1963 /* It is possible to ask compiler for say -mtune=i486 -march=pentium4. |
| 1964 -mtune=i486 causes us having PREFETCH_BLOCK 0, since this is part | |
| 1965 of processor costs and i486 does not have prefetch, but | |
| 111 | 1966 -march=pentium4 causes targetm.have_prefetch to be true. Ugh. */ |
| 0 | 1967 || PREFETCH_BLOCK == 0) |
| 1968 return 0; | |
| 1969 | |
| 1970 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 1971 { | |
| 1972 fprintf (dump_file, "Prefetching parameters:\n"); | |
| 1973 fprintf (dump_file, " simultaneous prefetches: %d\n", | |
| 1974 SIMULTANEOUS_PREFETCHES); | |
| 1975 fprintf (dump_file, " prefetch latency: %d\n", PREFETCH_LATENCY); | |
| 1976 fprintf (dump_file, " prefetch block size: %d\n", PREFETCH_BLOCK); | |
| 1977 fprintf (dump_file, " L1 cache size: %d lines, %d kB\n", | |
| 1978 L1_CACHE_SIZE_BYTES / L1_CACHE_LINE_SIZE, L1_CACHE_SIZE); | |
| 1979 fprintf (dump_file, " L1 cache line size: %d\n", L1_CACHE_LINE_SIZE); | |
| 1980 fprintf (dump_file, " L2 cache size: %d kB\n", L2_CACHE_SIZE); | |
|
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1981 fprintf (dump_file, " min insn-to-prefetch ratio: %d \n", |
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1982 MIN_INSN_TO_PREFETCH_RATIO); |
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1983 fprintf (dump_file, " min insn-to-mem ratio: %d \n", |
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1984 PREFETCH_MIN_INSN_TO_MEM_RATIO); |
| 0 | 1985 fprintf (dump_file, "\n"); |
| 1986 } | |
| 1987 | |
| 1988 initialize_original_copy_tables (); | |
| 1989 | |
| 111 | 1990 if (!builtin_decl_explicit_p (BUILT_IN_PREFETCH)) |
| 0 | 1991 { |
|
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1992 tree type = build_function_type_list (void_type_node, |
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1993 const_ptr_type_node, NULL_TREE); |
| 0 | 1994 tree decl = add_builtin_function ("__builtin_prefetch", type, |
| 1995 BUILT_IN_PREFETCH, BUILT_IN_NORMAL, | |
| 1996 NULL, NULL_TREE); | |
| 1997 DECL_IS_NOVOPS (decl) = true; | |
| 111 | 1998 set_builtin_decl (BUILT_IN_PREFETCH, decl, false); |
| 0 | 1999 } |
| 2000 | |
| 111 | 2001 FOR_EACH_LOOP (loop, LI_FROM_INNERMOST) |
| 0 | 2002 { |
| 2003 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 2004 fprintf (dump_file, "Processing loop %d:\n", loop->num); | |
| 2005 | |
| 2006 unrolled |= loop_prefetch_arrays (loop); | |
| 2007 | |
| 2008 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 2009 fprintf (dump_file, "\n\n"); | |
| 2010 } | |
| 2011 | |
| 2012 if (unrolled) | |
| 2013 { | |
| 2014 scev_reset (); | |
| 2015 todo_flags |= TODO_cleanup_cfg; | |
| 2016 } | |
| 2017 | |
| 2018 free_original_copy_tables (); | |
| 2019 return todo_flags; | |
| 2020 } | |
| 111 | 2021 |
| 2022 /* Prefetching. */ | |
| 2023 | |
| 2024 namespace { | |
| 2025 | |
| 2026 const pass_data pass_data_loop_prefetch = | |
| 2027 { | |
| 2028 GIMPLE_PASS, /* type */ | |
| 2029 "aprefetch", /* name */ | |
| 2030 OPTGROUP_LOOP, /* optinfo_flags */ | |
| 2031 TV_TREE_PREFETCH, /* tv_id */ | |
| 2032 ( PROP_cfg | PROP_ssa ), /* properties_required */ | |
| 2033 0, /* properties_provided */ | |
| 2034 0, /* properties_destroyed */ | |
| 2035 0, /* todo_flags_start */ | |
| 2036 0, /* todo_flags_finish */ | |
| 2037 }; | |
| 2038 | |
| 2039 class pass_loop_prefetch : public gimple_opt_pass | |
| 2040 { | |
| 2041 public: | |
| 2042 pass_loop_prefetch (gcc::context *ctxt) | |
| 2043 : gimple_opt_pass (pass_data_loop_prefetch, ctxt) | |
| 2044 {} | |
| 2045 | |
| 2046 /* opt_pass methods: */ | |
| 2047 virtual bool gate (function *) { return flag_prefetch_loop_arrays > 0; } | |
| 2048 virtual unsigned int execute (function *); | |
| 2049 | |
| 2050 }; // class pass_loop_prefetch | |
| 2051 | |
| 2052 unsigned int | |
| 2053 pass_loop_prefetch::execute (function *fun) | |
| 2054 { | |
| 2055 if (number_of_loops (fun) <= 1) | |
| 2056 return 0; | |
| 2057 | |
| 2058 if ((PREFETCH_BLOCK & (PREFETCH_BLOCK - 1)) != 0) | |
| 2059 { | |
| 2060 static bool warned = false; | |
| 2061 | |
| 2062 if (!warned) | |
| 2063 { | |
| 2064 warning (OPT_Wdisabled_optimization, | |
| 2065 "%<l1-cache-size%> parameter is not a power of two %d", | |
| 2066 PREFETCH_BLOCK); | |
| 2067 warned = true; | |
| 2068 } | |
| 2069 return 0; | |
| 2070 } | |
| 2071 | |
| 2072 return tree_ssa_prefetch_arrays (); | |
| 2073 } | |
| 2074 | |
| 2075 } // anon namespace | |
| 2076 | |
| 2077 gimple_opt_pass * | |
| 2078 make_pass_loop_prefetch (gcc::context *ctxt) | |
| 2079 { | |
| 2080 return new pass_loop_prefetch (ctxt); | |
| 2081 } | |
| 2082 | |
| 2083 |