Mercurial > hg > CbC > CbC_gcc
annotate gcc/predict.c @ 55:77e2b8dfacca gcc-4.4.5
update it from 4.4.3 to 4.5.0
| author | ryoma <e075725@ie.u-ryukyu.ac.jp> |
|---|---|
| date | Fri, 12 Feb 2010 23:39:51 +0900 |
| parents | a06113de4d67 |
| children | b7f97abdc517 |
| rev | line source |
|---|---|
| 0 | 1 /* Branch prediction routines for the GNU compiler. |
|
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ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
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diff
changeset
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2 Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009 |
| 0 | 3 Free Software Foundation, Inc. |
| 4 | |
| 5 This file is part of GCC. | |
| 6 | |
| 7 GCC is free software; you can redistribute it and/or modify it under | |
| 8 the terms of the GNU General Public License as published by the Free | |
| 9 Software Foundation; either version 3, or (at your option) any later | |
| 10 version. | |
| 11 | |
| 12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
| 13 WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 15 for more details. | |
| 16 | |
| 17 You should have received a copy of the GNU General Public License | |
| 18 along with GCC; see the file COPYING3. If not see | |
| 19 <http://www.gnu.org/licenses/>. */ | |
| 20 | |
| 21 /* References: | |
| 22 | |
| 23 [1] "Branch Prediction for Free" | |
| 24 Ball and Larus; PLDI '93. | |
| 25 [2] "Static Branch Frequency and Program Profile Analysis" | |
| 26 Wu and Larus; MICRO-27. | |
| 27 [3] "Corpus-based Static Branch Prediction" | |
| 28 Calder, Grunwald, Lindsay, Martin, Mozer, and Zorn; PLDI '95. */ | |
| 29 | |
| 30 | |
| 31 #include "config.h" | |
| 32 #include "system.h" | |
| 33 #include "coretypes.h" | |
| 34 #include "tm.h" | |
| 35 #include "tree.h" | |
| 36 #include "rtl.h" | |
| 37 #include "tm_p.h" | |
| 38 #include "hard-reg-set.h" | |
| 39 #include "basic-block.h" | |
| 40 #include "insn-config.h" | |
| 41 #include "regs.h" | |
| 42 #include "flags.h" | |
| 43 #include "output.h" | |
| 44 #include "function.h" | |
| 45 #include "except.h" | |
| 46 #include "toplev.h" | |
| 47 #include "recog.h" | |
| 48 #include "expr.h" | |
| 49 #include "predict.h" | |
| 50 #include "coverage.h" | |
| 51 #include "sreal.h" | |
| 52 #include "params.h" | |
| 53 #include "target.h" | |
| 54 #include "cfgloop.h" | |
| 55 #include "tree-flow.h" | |
| 56 #include "ggc.h" | |
| 57 #include "tree-dump.h" | |
| 58 #include "tree-pass.h" | |
| 59 #include "timevar.h" | |
| 60 #include "tree-scalar-evolution.h" | |
| 61 #include "cfgloop.h" | |
| 62 #include "pointer-set.h" | |
| 63 | |
| 64 /* real constants: 0, 1, 1-1/REG_BR_PROB_BASE, REG_BR_PROB_BASE, | |
| 65 1/REG_BR_PROB_BASE, 0.5, BB_FREQ_MAX. */ | |
| 66 static sreal real_zero, real_one, real_almost_one, real_br_prob_base, | |
| 67 real_inv_br_prob_base, real_one_half, real_bb_freq_max; | |
| 68 | |
|
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ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
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changeset
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69 /* Random guesstimation given names. |
| 0 | 70 PROV_VERY_UNLIKELY should be small enough so basic block predicted |
| 71 by it gets bellow HOT_BB_FREQUENCY_FRANCTION. */ | |
| 72 #define PROB_VERY_UNLIKELY (REG_BR_PROB_BASE / 2000 - 1) | |
| 73 #define PROB_EVEN (REG_BR_PROB_BASE / 2) | |
| 74 #define PROB_VERY_LIKELY (REG_BR_PROB_BASE - PROB_VERY_UNLIKELY) | |
| 75 #define PROB_ALWAYS (REG_BR_PROB_BASE) | |
| 76 | |
| 77 static void combine_predictions_for_insn (rtx, basic_block); | |
| 78 static void dump_prediction (FILE *, enum br_predictor, int, basic_block, int); | |
| 79 static void predict_paths_leading_to (basic_block, enum br_predictor, enum prediction); | |
| 80 static void choose_function_section (void); | |
| 81 static bool can_predict_insn_p (const_rtx); | |
| 82 | |
| 83 /* Information we hold about each branch predictor. | |
| 84 Filled using information from predict.def. */ | |
| 85 | |
| 86 struct predictor_info | |
| 87 { | |
| 88 const char *const name; /* Name used in the debugging dumps. */ | |
| 89 const int hitrate; /* Expected hitrate used by | |
| 90 predict_insn_def call. */ | |
| 91 const int flags; | |
| 92 }; | |
| 93 | |
| 94 /* Use given predictor without Dempster-Shaffer theory if it matches | |
| 95 using first_match heuristics. */ | |
| 96 #define PRED_FLAG_FIRST_MATCH 1 | |
| 97 | |
| 98 /* Recompute hitrate in percent to our representation. */ | |
| 99 | |
| 100 #define HITRATE(VAL) ((int) ((VAL) * REG_BR_PROB_BASE + 50) / 100) | |
| 101 | |
| 102 #define DEF_PREDICTOR(ENUM, NAME, HITRATE, FLAGS) {NAME, HITRATE, FLAGS}, | |
| 103 static const struct predictor_info predictor_info[]= { | |
| 104 #include "predict.def" | |
| 105 | |
| 106 /* Upper bound on predictors. */ | |
| 107 {NULL, 0, 0} | |
| 108 }; | |
| 109 #undef DEF_PREDICTOR | |
| 110 | |
| 111 /* Return TRUE if frequency FREQ is considered to be hot. */ | |
| 112 | |
| 113 static inline bool | |
| 114 maybe_hot_frequency_p (int freq) | |
| 115 { | |
| 116 if (!profile_info || !flag_branch_probabilities) | |
| 117 { | |
| 118 if (cfun->function_frequency == FUNCTION_FREQUENCY_UNLIKELY_EXECUTED) | |
| 119 return false; | |
| 120 if (cfun->function_frequency == FUNCTION_FREQUENCY_HOT) | |
| 121 return true; | |
| 122 } | |
| 123 if (profile_status == PROFILE_ABSENT) | |
| 124 return true; | |
| 125 if (freq < BB_FREQ_MAX / PARAM_VALUE (HOT_BB_FREQUENCY_FRACTION)) | |
| 126 return false; | |
| 127 return true; | |
| 128 } | |
| 129 | |
| 130 /* Return TRUE if frequency FREQ is considered to be hot. */ | |
| 131 | |
| 132 static inline bool | |
| 133 maybe_hot_count_p (gcov_type count) | |
| 134 { | |
| 135 if (profile_status != PROFILE_READ) | |
| 136 return true; | |
| 137 /* Code executed at most once is not hot. */ | |
| 138 if (profile_info->runs >= count) | |
| 139 return false; | |
| 140 return (count | |
| 141 > profile_info->sum_max / PARAM_VALUE (HOT_BB_COUNT_FRACTION)); | |
| 142 } | |
| 143 | |
| 144 /* Return true in case BB can be CPU intensive and should be optimized | |
| 145 for maximal performance. */ | |
| 146 | |
| 147 bool | |
| 148 maybe_hot_bb_p (const_basic_block bb) | |
| 149 { | |
| 150 if (profile_status == PROFILE_READ) | |
| 151 return maybe_hot_count_p (bb->count); | |
| 152 return maybe_hot_frequency_p (bb->frequency); | |
| 153 } | |
| 154 | |
| 155 /* Return true if the call can be hot. */ | |
| 156 | |
| 157 bool | |
| 158 cgraph_maybe_hot_edge_p (struct cgraph_edge *edge) | |
| 159 { | |
| 160 if (profile_info && flag_branch_probabilities | |
| 161 && (edge->count | |
| 162 <= profile_info->sum_max / PARAM_VALUE (HOT_BB_COUNT_FRACTION))) | |
| 163 return false; | |
| 164 if (lookup_attribute ("cold", DECL_ATTRIBUTES (edge->callee->decl)) | |
| 165 || lookup_attribute ("cold", DECL_ATTRIBUTES (edge->caller->decl))) | |
| 166 return false; | |
| 167 if (lookup_attribute ("hot", DECL_ATTRIBUTES (edge->caller->decl))) | |
| 168 return true; | |
| 169 if (flag_guess_branch_prob | |
|
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77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
170 && edge->frequency <= (CGRAPH_FREQ_BASE |
|
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
171 / PARAM_VALUE (HOT_BB_FREQUENCY_FRACTION))) |
| 0 | 172 return false; |
| 173 return true; | |
| 174 } | |
| 175 | |
| 176 /* Return true in case BB can be CPU intensive and should be optimized | |
| 177 for maximal performance. */ | |
| 178 | |
| 179 bool | |
| 180 maybe_hot_edge_p (edge e) | |
| 181 { | |
| 182 if (profile_status == PROFILE_READ) | |
| 183 return maybe_hot_count_p (e->count); | |
| 184 return maybe_hot_frequency_p (EDGE_FREQUENCY (e)); | |
| 185 } | |
| 186 | |
| 187 /* Return true in case BB is probably never executed. */ | |
| 188 bool | |
| 189 probably_never_executed_bb_p (const_basic_block bb) | |
| 190 { | |
| 191 if (profile_info && flag_branch_probabilities) | |
| 192 return ((bb->count + profile_info->runs / 2) / profile_info->runs) == 0; | |
| 193 if ((!profile_info || !flag_branch_probabilities) | |
| 194 && cfun->function_frequency == FUNCTION_FREQUENCY_UNLIKELY_EXECUTED) | |
| 195 return true; | |
| 196 return false; | |
| 197 } | |
| 198 | |
| 199 /* Return true when current function should always be optimized for size. */ | |
| 200 | |
| 201 bool | |
| 202 optimize_function_for_size_p (struct function *fun) | |
| 203 { | |
| 204 return (optimize_size | |
| 205 || (fun && (fun->function_frequency | |
| 206 == FUNCTION_FREQUENCY_UNLIKELY_EXECUTED))); | |
| 207 } | |
| 208 | |
| 209 /* Return true when current function should always be optimized for speed. */ | |
| 210 | |
| 211 bool | |
| 212 optimize_function_for_speed_p (struct function *fun) | |
| 213 { | |
| 214 return !optimize_function_for_size_p (fun); | |
| 215 } | |
| 216 | |
| 217 /* Return TRUE when BB should be optimized for size. */ | |
| 218 | |
| 219 bool | |
| 220 optimize_bb_for_size_p (const_basic_block bb) | |
| 221 { | |
| 222 return optimize_function_for_size_p (cfun) || !maybe_hot_bb_p (bb); | |
| 223 } | |
| 224 | |
| 225 /* Return TRUE when BB should be optimized for speed. */ | |
| 226 | |
| 227 bool | |
| 228 optimize_bb_for_speed_p (const_basic_block bb) | |
| 229 { | |
| 230 return !optimize_bb_for_size_p (bb); | |
| 231 } | |
| 232 | |
| 233 /* Return TRUE when BB should be optimized for size. */ | |
| 234 | |
| 235 bool | |
| 236 optimize_edge_for_size_p (edge e) | |
| 237 { | |
| 238 return optimize_function_for_size_p (cfun) || !maybe_hot_edge_p (e); | |
| 239 } | |
| 240 | |
| 241 /* Return TRUE when BB should be optimized for speed. */ | |
| 242 | |
| 243 bool | |
| 244 optimize_edge_for_speed_p (edge e) | |
| 245 { | |
| 246 return !optimize_edge_for_size_p (e); | |
| 247 } | |
| 248 | |
| 249 /* Return TRUE when BB should be optimized for size. */ | |
| 250 | |
| 251 bool | |
| 252 optimize_insn_for_size_p (void) | |
| 253 { | |
| 254 return optimize_function_for_size_p (cfun) || !crtl->maybe_hot_insn_p; | |
| 255 } | |
| 256 | |
| 257 /* Return TRUE when BB should be optimized for speed. */ | |
| 258 | |
| 259 bool | |
| 260 optimize_insn_for_speed_p (void) | |
| 261 { | |
| 262 return !optimize_insn_for_size_p (); | |
| 263 } | |
| 264 | |
| 265 /* Return TRUE when LOOP should be optimized for size. */ | |
| 266 | |
| 267 bool | |
| 268 optimize_loop_for_size_p (struct loop *loop) | |
| 269 { | |
| 270 return optimize_bb_for_size_p (loop->header); | |
| 271 } | |
| 272 | |
| 273 /* Return TRUE when LOOP should be optimized for speed. */ | |
| 274 | |
| 275 bool | |
| 276 optimize_loop_for_speed_p (struct loop *loop) | |
| 277 { | |
| 278 return optimize_bb_for_speed_p (loop->header); | |
| 279 } | |
| 280 | |
| 281 /* Return TRUE when LOOP nest should be optimized for speed. */ | |
| 282 | |
| 283 bool | |
| 284 optimize_loop_nest_for_speed_p (struct loop *loop) | |
| 285 { | |
| 286 struct loop *l = loop; | |
| 287 if (optimize_loop_for_speed_p (loop)) | |
| 288 return true; | |
| 289 l = loop->inner; | |
| 290 while (l && l != loop) | |
| 291 { | |
| 292 if (optimize_loop_for_speed_p (l)) | |
| 293 return true; | |
| 294 if (l->inner) | |
| 295 l = l->inner; | |
| 296 else if (l->next) | |
| 297 l = l->next; | |
| 298 else | |
| 299 { | |
| 300 while (l != loop && !l->next) | |
| 301 l = loop_outer (l); | |
| 302 if (l != loop) | |
| 303 l = l->next; | |
| 304 } | |
| 305 } | |
| 306 return false; | |
| 307 } | |
| 308 | |
| 309 /* Return TRUE when LOOP nest should be optimized for size. */ | |
| 310 | |
| 311 bool | |
| 312 optimize_loop_nest_for_size_p (struct loop *loop) | |
| 313 { | |
| 314 return !optimize_loop_nest_for_speed_p (loop); | |
| 315 } | |
| 316 | |
| 317 /* Return true when edge E is likely to be well predictable by branch | |
| 318 predictor. */ | |
| 319 | |
| 320 bool | |
| 321 predictable_edge_p (edge e) | |
| 322 { | |
| 323 if (profile_status == PROFILE_ABSENT) | |
| 324 return false; | |
| 325 if ((e->probability | |
| 326 <= PARAM_VALUE (PARAM_PREDICTABLE_BRANCH_OUTCOME) * REG_BR_PROB_BASE / 100) | |
| 327 || (REG_BR_PROB_BASE - e->probability | |
| 328 <= PARAM_VALUE (PARAM_PREDICTABLE_BRANCH_OUTCOME) * REG_BR_PROB_BASE / 100)) | |
| 329 return true; | |
| 330 return false; | |
| 331 } | |
| 332 | |
| 333 | |
| 334 /* Set RTL expansion for BB profile. */ | |
| 335 | |
| 336 void | |
| 337 rtl_profile_for_bb (basic_block bb) | |
| 338 { | |
| 339 crtl->maybe_hot_insn_p = maybe_hot_bb_p (bb); | |
| 340 } | |
| 341 | |
| 342 /* Set RTL expansion for edge profile. */ | |
| 343 | |
| 344 void | |
| 345 rtl_profile_for_edge (edge e) | |
| 346 { | |
| 347 crtl->maybe_hot_insn_p = maybe_hot_edge_p (e); | |
| 348 } | |
| 349 | |
| 350 /* Set RTL expansion to default mode (i.e. when profile info is not known). */ | |
| 351 void | |
| 352 default_rtl_profile (void) | |
| 353 { | |
| 354 crtl->maybe_hot_insn_p = true; | |
| 355 } | |
| 356 | |
| 357 /* Return true if the one of outgoing edges is already predicted by | |
| 358 PREDICTOR. */ | |
| 359 | |
| 360 bool | |
| 361 rtl_predicted_by_p (const_basic_block bb, enum br_predictor predictor) | |
| 362 { | |
| 363 rtx note; | |
| 364 if (!INSN_P (BB_END (bb))) | |
| 365 return false; | |
| 366 for (note = REG_NOTES (BB_END (bb)); note; note = XEXP (note, 1)) | |
| 367 if (REG_NOTE_KIND (note) == REG_BR_PRED | |
| 368 && INTVAL (XEXP (XEXP (note, 0), 0)) == (int)predictor) | |
| 369 return true; | |
| 370 return false; | |
| 371 } | |
| 372 | |
| 373 /* This map contains for a basic block the list of predictions for the | |
| 374 outgoing edges. */ | |
| 375 | |
| 376 static struct pointer_map_t *bb_predictions; | |
| 377 | |
| 378 /* Return true if the one of outgoing edges is already predicted by | |
| 379 PREDICTOR. */ | |
| 380 | |
| 381 bool | |
| 382 gimple_predicted_by_p (const_basic_block bb, enum br_predictor predictor) | |
| 383 { | |
| 384 struct edge_prediction *i; | |
| 385 void **preds = pointer_map_contains (bb_predictions, bb); | |
| 386 | |
| 387 if (!preds) | |
| 388 return false; | |
|
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77e2b8dfacca
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ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
389 |
| 0 | 390 for (i = (struct edge_prediction *) *preds; i; i = i->ep_next) |
| 391 if (i->ep_predictor == predictor) | |
| 392 return true; | |
| 393 return false; | |
| 394 } | |
| 395 | |
| 396 /* Return true when the probability of edge is reliable. | |
|
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77e2b8dfacca
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ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
397 |
| 0 | 398 The profile guessing code is good at predicting branch outcome (ie. |
| 399 taken/not taken), that is predicted right slightly over 75% of time. | |
| 400 It is however notoriously poor on predicting the probability itself. | |
| 401 In general the profile appear a lot flatter (with probabilities closer | |
| 402 to 50%) than the reality so it is bad idea to use it to drive optimization | |
| 403 such as those disabling dynamic branch prediction for well predictable | |
| 404 branches. | |
| 405 | |
| 406 There are two exceptions - edges leading to noreturn edges and edges | |
| 407 predicted by number of iterations heuristics are predicted well. This macro | |
| 408 should be able to distinguish those, but at the moment it simply check for | |
| 409 noreturn heuristic that is only one giving probability over 99% or bellow | |
| 410 1%. In future we might want to propagate reliability information across the | |
| 411 CFG if we find this information useful on multiple places. */ | |
| 412 static bool | |
| 413 probability_reliable_p (int prob) | |
| 414 { | |
| 415 return (profile_status == PROFILE_READ | |
| 416 || (profile_status == PROFILE_GUESSED | |
| 417 && (prob <= HITRATE (1) || prob >= HITRATE (99)))); | |
| 418 } | |
| 419 | |
| 420 /* Same predicate as above, working on edges. */ | |
| 421 bool | |
| 422 edge_probability_reliable_p (const_edge e) | |
| 423 { | |
| 424 return probability_reliable_p (e->probability); | |
| 425 } | |
| 426 | |
| 427 /* Same predicate as edge_probability_reliable_p, working on notes. */ | |
| 428 bool | |
| 429 br_prob_note_reliable_p (const_rtx note) | |
| 430 { | |
| 431 gcc_assert (REG_NOTE_KIND (note) == REG_BR_PROB); | |
| 432 return probability_reliable_p (INTVAL (XEXP (note, 0))); | |
| 433 } | |
| 434 | |
| 435 static void | |
| 436 predict_insn (rtx insn, enum br_predictor predictor, int probability) | |
| 437 { | |
| 438 gcc_assert (any_condjump_p (insn)); | |
| 439 if (!flag_guess_branch_prob) | |
| 440 return; | |
| 441 | |
| 442 add_reg_note (insn, REG_BR_PRED, | |
| 443 gen_rtx_CONCAT (VOIDmode, | |
| 444 GEN_INT ((int) predictor), | |
| 445 GEN_INT ((int) probability))); | |
| 446 } | |
| 447 | |
| 448 /* Predict insn by given predictor. */ | |
| 449 | |
| 450 void | |
| 451 predict_insn_def (rtx insn, enum br_predictor predictor, | |
| 452 enum prediction taken) | |
| 453 { | |
| 454 int probability = predictor_info[(int) predictor].hitrate; | |
| 455 | |
| 456 if (taken != TAKEN) | |
| 457 probability = REG_BR_PROB_BASE - probability; | |
| 458 | |
| 459 predict_insn (insn, predictor, probability); | |
| 460 } | |
| 461 | |
| 462 /* Predict edge E with given probability if possible. */ | |
| 463 | |
| 464 void | |
| 465 rtl_predict_edge (edge e, enum br_predictor predictor, int probability) | |
| 466 { | |
| 467 rtx last_insn; | |
| 468 last_insn = BB_END (e->src); | |
| 469 | |
| 470 /* We can store the branch prediction information only about | |
| 471 conditional jumps. */ | |
| 472 if (!any_condjump_p (last_insn)) | |
| 473 return; | |
| 474 | |
| 475 /* We always store probability of branching. */ | |
| 476 if (e->flags & EDGE_FALLTHRU) | |
| 477 probability = REG_BR_PROB_BASE - probability; | |
| 478 | |
| 479 predict_insn (last_insn, predictor, probability); | |
| 480 } | |
| 481 | |
| 482 /* Predict edge E with the given PROBABILITY. */ | |
| 483 void | |
| 484 gimple_predict_edge (edge e, enum br_predictor predictor, int probability) | |
| 485 { | |
| 486 gcc_assert (profile_status != PROFILE_GUESSED); | |
| 487 if ((e->src != ENTRY_BLOCK_PTR && EDGE_COUNT (e->src->succs) > 1) | |
| 488 && flag_guess_branch_prob && optimize) | |
| 489 { | |
| 490 struct edge_prediction *i = XNEW (struct edge_prediction); | |
| 491 void **preds = pointer_map_insert (bb_predictions, e->src); | |
| 492 | |
| 493 i->ep_next = (struct edge_prediction *) *preds; | |
| 494 *preds = i; | |
| 495 i->ep_probability = probability; | |
| 496 i->ep_predictor = predictor; | |
| 497 i->ep_edge = e; | |
| 498 } | |
| 499 } | |
| 500 | |
| 501 /* Remove all predictions on given basic block that are attached | |
| 502 to edge E. */ | |
| 503 void | |
| 504 remove_predictions_associated_with_edge (edge e) | |
| 505 { | |
| 506 void **preds; | |
|
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77e2b8dfacca
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ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
507 |
| 0 | 508 if (!bb_predictions) |
| 509 return; | |
| 510 | |
| 511 preds = pointer_map_contains (bb_predictions, e->src); | |
| 512 | |
| 513 if (preds) | |
| 514 { | |
| 515 struct edge_prediction **prediction = (struct edge_prediction **) preds; | |
| 516 struct edge_prediction *next; | |
| 517 | |
| 518 while (*prediction) | |
| 519 { | |
| 520 if ((*prediction)->ep_edge == e) | |
| 521 { | |
| 522 next = (*prediction)->ep_next; | |
| 523 free (*prediction); | |
| 524 *prediction = next; | |
| 525 } | |
| 526 else | |
| 527 prediction = &((*prediction)->ep_next); | |
| 528 } | |
| 529 } | |
| 530 } | |
| 531 | |
| 532 /* Clears the list of predictions stored for BB. */ | |
| 533 | |
| 534 static void | |
| 535 clear_bb_predictions (basic_block bb) | |
| 536 { | |
| 537 void **preds = pointer_map_contains (bb_predictions, bb); | |
| 538 struct edge_prediction *pred, *next; | |
| 539 | |
| 540 if (!preds) | |
| 541 return; | |
| 542 | |
| 543 for (pred = (struct edge_prediction *) *preds; pred; pred = next) | |
| 544 { | |
| 545 next = pred->ep_next; | |
| 546 free (pred); | |
| 547 } | |
| 548 *preds = NULL; | |
| 549 } | |
| 550 | |
| 551 /* Return true when we can store prediction on insn INSN. | |
| 552 At the moment we represent predictions only on conditional | |
| 553 jumps, not at computed jump or other complicated cases. */ | |
| 554 static bool | |
| 555 can_predict_insn_p (const_rtx insn) | |
| 556 { | |
| 557 return (JUMP_P (insn) | |
| 558 && any_condjump_p (insn) | |
| 559 && EDGE_COUNT (BLOCK_FOR_INSN (insn)->succs) >= 2); | |
| 560 } | |
| 561 | |
| 562 /* Predict edge E by given predictor if possible. */ | |
| 563 | |
| 564 void | |
| 565 predict_edge_def (edge e, enum br_predictor predictor, | |
| 566 enum prediction taken) | |
| 567 { | |
| 568 int probability = predictor_info[(int) predictor].hitrate; | |
| 569 | |
| 570 if (taken != TAKEN) | |
| 571 probability = REG_BR_PROB_BASE - probability; | |
| 572 | |
| 573 predict_edge (e, predictor, probability); | |
| 574 } | |
| 575 | |
| 576 /* Invert all branch predictions or probability notes in the INSN. This needs | |
| 577 to be done each time we invert the condition used by the jump. */ | |
| 578 | |
| 579 void | |
| 580 invert_br_probabilities (rtx insn) | |
| 581 { | |
| 582 rtx note; | |
| 583 | |
| 584 for (note = REG_NOTES (insn); note; note = XEXP (note, 1)) | |
| 585 if (REG_NOTE_KIND (note) == REG_BR_PROB) | |
| 586 XEXP (note, 0) = GEN_INT (REG_BR_PROB_BASE - INTVAL (XEXP (note, 0))); | |
| 587 else if (REG_NOTE_KIND (note) == REG_BR_PRED) | |
| 588 XEXP (XEXP (note, 0), 1) | |
| 589 = GEN_INT (REG_BR_PROB_BASE - INTVAL (XEXP (XEXP (note, 0), 1))); | |
| 590 } | |
| 591 | |
| 592 /* Dump information about the branch prediction to the output file. */ | |
| 593 | |
| 594 static void | |
| 595 dump_prediction (FILE *file, enum br_predictor predictor, int probability, | |
| 596 basic_block bb, int used) | |
| 597 { | |
| 598 edge e; | |
| 599 edge_iterator ei; | |
| 600 | |
| 601 if (!file) | |
| 602 return; | |
| 603 | |
| 604 FOR_EACH_EDGE (e, ei, bb->succs) | |
| 605 if (! (e->flags & EDGE_FALLTHRU)) | |
| 606 break; | |
| 607 | |
| 608 fprintf (file, " %s heuristics%s: %.1f%%", | |
| 609 predictor_info[predictor].name, | |
| 610 used ? "" : " (ignored)", probability * 100.0 / REG_BR_PROB_BASE); | |
| 611 | |
| 612 if (bb->count) | |
| 613 { | |
| 614 fprintf (file, " exec "); | |
| 615 fprintf (file, HOST_WIDEST_INT_PRINT_DEC, bb->count); | |
| 616 if (e) | |
| 617 { | |
| 618 fprintf (file, " hit "); | |
| 619 fprintf (file, HOST_WIDEST_INT_PRINT_DEC, e->count); | |
| 620 fprintf (file, " (%.1f%%)", e->count * 100.0 / bb->count); | |
| 621 } | |
| 622 } | |
| 623 | |
| 624 fprintf (file, "\n"); | |
| 625 } | |
| 626 | |
| 627 /* We can not predict the probabilities of outgoing edges of bb. Set them | |
| 628 evenly and hope for the best. */ | |
| 629 static void | |
| 630 set_even_probabilities (basic_block bb) | |
| 631 { | |
| 632 int nedges = 0; | |
| 633 edge e; | |
| 634 edge_iterator ei; | |
| 635 | |
| 636 FOR_EACH_EDGE (e, ei, bb->succs) | |
| 637 if (!(e->flags & (EDGE_EH | EDGE_FAKE))) | |
| 638 nedges ++; | |
| 639 FOR_EACH_EDGE (e, ei, bb->succs) | |
| 640 if (!(e->flags & (EDGE_EH | EDGE_FAKE))) | |
| 641 e->probability = (REG_BR_PROB_BASE + nedges / 2) / nedges; | |
| 642 else | |
| 643 e->probability = 0; | |
| 644 } | |
| 645 | |
| 646 /* Combine all REG_BR_PRED notes into single probability and attach REG_BR_PROB | |
| 647 note if not already present. Remove now useless REG_BR_PRED notes. */ | |
| 648 | |
| 649 static void | |
| 650 combine_predictions_for_insn (rtx insn, basic_block bb) | |
| 651 { | |
| 652 rtx prob_note; | |
| 653 rtx *pnote; | |
| 654 rtx note; | |
| 655 int best_probability = PROB_EVEN; | |
|
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656 enum br_predictor best_predictor = END_PREDICTORS; |
| 0 | 657 int combined_probability = REG_BR_PROB_BASE / 2; |
| 658 int d; | |
| 659 bool first_match = false; | |
| 660 bool found = false; | |
| 661 | |
| 662 if (!can_predict_insn_p (insn)) | |
| 663 { | |
| 664 set_even_probabilities (bb); | |
| 665 return; | |
| 666 } | |
| 667 | |
| 668 prob_note = find_reg_note (insn, REG_BR_PROB, 0); | |
| 669 pnote = ®_NOTES (insn); | |
| 670 if (dump_file) | |
| 671 fprintf (dump_file, "Predictions for insn %i bb %i\n", INSN_UID (insn), | |
| 672 bb->index); | |
| 673 | |
| 674 /* We implement "first match" heuristics and use probability guessed | |
| 675 by predictor with smallest index. */ | |
| 676 for (note = REG_NOTES (insn); note; note = XEXP (note, 1)) | |
| 677 if (REG_NOTE_KIND (note) == REG_BR_PRED) | |
| 678 { | |
|
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679 enum br_predictor predictor = ((enum br_predictor) |
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680 INTVAL (XEXP (XEXP (note, 0), 0))); |
| 0 | 681 int probability = INTVAL (XEXP (XEXP (note, 0), 1)); |
| 682 | |
| 683 found = true; | |
| 684 if (best_predictor > predictor) | |
| 685 best_probability = probability, best_predictor = predictor; | |
| 686 | |
| 687 d = (combined_probability * probability | |
| 688 + (REG_BR_PROB_BASE - combined_probability) | |
| 689 * (REG_BR_PROB_BASE - probability)); | |
| 690 | |
| 691 /* Use FP math to avoid overflows of 32bit integers. */ | |
| 692 if (d == 0) | |
| 693 /* If one probability is 0% and one 100%, avoid division by zero. */ | |
| 694 combined_probability = REG_BR_PROB_BASE / 2; | |
| 695 else | |
| 696 combined_probability = (((double) combined_probability) * probability | |
| 697 * REG_BR_PROB_BASE / d + 0.5); | |
| 698 } | |
| 699 | |
| 700 /* Decide which heuristic to use. In case we didn't match anything, | |
| 701 use no_prediction heuristic, in case we did match, use either | |
| 702 first match or Dempster-Shaffer theory depending on the flags. */ | |
| 703 | |
| 704 if (predictor_info [best_predictor].flags & PRED_FLAG_FIRST_MATCH) | |
| 705 first_match = true; | |
| 706 | |
| 707 if (!found) | |
| 708 dump_prediction (dump_file, PRED_NO_PREDICTION, | |
| 709 combined_probability, bb, true); | |
| 710 else | |
| 711 { | |
| 712 dump_prediction (dump_file, PRED_DS_THEORY, combined_probability, | |
| 713 bb, !first_match); | |
| 714 dump_prediction (dump_file, PRED_FIRST_MATCH, best_probability, | |
| 715 bb, first_match); | |
| 716 } | |
| 717 | |
| 718 if (first_match) | |
| 719 combined_probability = best_probability; | |
| 720 dump_prediction (dump_file, PRED_COMBINED, combined_probability, bb, true); | |
| 721 | |
| 722 while (*pnote) | |
| 723 { | |
| 724 if (REG_NOTE_KIND (*pnote) == REG_BR_PRED) | |
| 725 { | |
|
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726 enum br_predictor predictor = ((enum br_predictor) |
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727 INTVAL (XEXP (XEXP (*pnote, 0), 0))); |
| 0 | 728 int probability = INTVAL (XEXP (XEXP (*pnote, 0), 1)); |
| 729 | |
| 730 dump_prediction (dump_file, predictor, probability, bb, | |
| 731 !first_match || best_predictor == predictor); | |
| 732 *pnote = XEXP (*pnote, 1); | |
| 733 } | |
| 734 else | |
| 735 pnote = &XEXP (*pnote, 1); | |
| 736 } | |
| 737 | |
| 738 if (!prob_note) | |
| 739 { | |
| 740 add_reg_note (insn, REG_BR_PROB, GEN_INT (combined_probability)); | |
| 741 | |
| 742 /* Save the prediction into CFG in case we are seeing non-degenerated | |
| 743 conditional jump. */ | |
| 744 if (!single_succ_p (bb)) | |
| 745 { | |
| 746 BRANCH_EDGE (bb)->probability = combined_probability; | |
| 747 FALLTHRU_EDGE (bb)->probability | |
| 748 = REG_BR_PROB_BASE - combined_probability; | |
| 749 } | |
| 750 } | |
| 751 else if (!single_succ_p (bb)) | |
| 752 { | |
| 753 int prob = INTVAL (XEXP (prob_note, 0)); | |
| 754 | |
| 755 BRANCH_EDGE (bb)->probability = prob; | |
| 756 FALLTHRU_EDGE (bb)->probability = REG_BR_PROB_BASE - prob; | |
| 757 } | |
| 758 else | |
| 759 single_succ_edge (bb)->probability = REG_BR_PROB_BASE; | |
| 760 } | |
| 761 | |
| 762 /* Combine predictions into single probability and store them into CFG. | |
| 763 Remove now useless prediction entries. */ | |
| 764 | |
| 765 static void | |
| 766 combine_predictions_for_bb (basic_block bb) | |
| 767 { | |
| 768 int best_probability = PROB_EVEN; | |
|
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769 enum br_predictor best_predictor = END_PREDICTORS; |
| 0 | 770 int combined_probability = REG_BR_PROB_BASE / 2; |
| 771 int d; | |
| 772 bool first_match = false; | |
| 773 bool found = false; | |
| 774 struct edge_prediction *pred; | |
| 775 int nedges = 0; | |
| 776 edge e, first = NULL, second = NULL; | |
| 777 edge_iterator ei; | |
| 778 void **preds; | |
| 779 | |
| 780 FOR_EACH_EDGE (e, ei, bb->succs) | |
| 781 if (!(e->flags & (EDGE_EH | EDGE_FAKE))) | |
| 782 { | |
| 783 nedges ++; | |
| 784 if (first && !second) | |
| 785 second = e; | |
| 786 if (!first) | |
| 787 first = e; | |
| 788 } | |
| 789 | |
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790 /* When there is no successor or only one choice, prediction is easy. |
| 0 | 791 |
| 792 We are lazy for now and predict only basic blocks with two outgoing | |
| 793 edges. It is possible to predict generic case too, but we have to | |
| 794 ignore first match heuristics and do more involved combining. Implement | |
| 795 this later. */ | |
| 796 if (nedges != 2) | |
| 797 { | |
| 798 if (!bb->count) | |
| 799 set_even_probabilities (bb); | |
| 800 clear_bb_predictions (bb); | |
| 801 if (dump_file) | |
| 802 fprintf (dump_file, "%i edges in bb %i predicted to even probabilities\n", | |
| 803 nedges, bb->index); | |
| 804 return; | |
| 805 } | |
| 806 | |
| 807 if (dump_file) | |
| 808 fprintf (dump_file, "Predictions for bb %i\n", bb->index); | |
| 809 | |
| 810 preds = pointer_map_contains (bb_predictions, bb); | |
| 811 if (preds) | |
| 812 { | |
| 813 /* We implement "first match" heuristics and use probability guessed | |
| 814 by predictor with smallest index. */ | |
| 815 for (pred = (struct edge_prediction *) *preds; pred; pred = pred->ep_next) | |
| 816 { | |
|
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817 enum br_predictor predictor = pred->ep_predictor; |
| 0 | 818 int probability = pred->ep_probability; |
| 819 | |
| 820 if (pred->ep_edge != first) | |
| 821 probability = REG_BR_PROB_BASE - probability; | |
| 822 | |
| 823 found = true; | |
| 824 /* First match heuristics would be widly confused if we predicted | |
| 825 both directions. */ | |
| 826 if (best_predictor > predictor) | |
| 827 { | |
| 828 struct edge_prediction *pred2; | |
| 829 int prob = probability; | |
| 830 | |
| 831 for (pred2 = (struct edge_prediction *) *preds; pred2; pred2 = pred2->ep_next) | |
| 832 if (pred2 != pred && pred2->ep_predictor == pred->ep_predictor) | |
| 833 { | |
| 834 int probability2 = pred->ep_probability; | |
| 835 | |
| 836 if (pred2->ep_edge != first) | |
| 837 probability2 = REG_BR_PROB_BASE - probability2; | |
| 838 | |
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839 if ((probability < REG_BR_PROB_BASE / 2) != |
| 0 | 840 (probability2 < REG_BR_PROB_BASE / 2)) |
| 841 break; | |
| 842 | |
| 843 /* If the same predictor later gave better result, go for it! */ | |
| 844 if ((probability >= REG_BR_PROB_BASE / 2 && (probability2 > probability)) | |
| 845 || (probability <= REG_BR_PROB_BASE / 2 && (probability2 < probability))) | |
| 846 prob = probability2; | |
| 847 } | |
| 848 if (!pred2) | |
| 849 best_probability = prob, best_predictor = predictor; | |
| 850 } | |
| 851 | |
| 852 d = (combined_probability * probability | |
| 853 + (REG_BR_PROB_BASE - combined_probability) | |
| 854 * (REG_BR_PROB_BASE - probability)); | |
| 855 | |
| 856 /* Use FP math to avoid overflows of 32bit integers. */ | |
| 857 if (d == 0) | |
| 858 /* If one probability is 0% and one 100%, avoid division by zero. */ | |
| 859 combined_probability = REG_BR_PROB_BASE / 2; | |
| 860 else | |
| 861 combined_probability = (((double) combined_probability) | |
| 862 * probability | |
| 863 * REG_BR_PROB_BASE / d + 0.5); | |
| 864 } | |
| 865 } | |
| 866 | |
| 867 /* Decide which heuristic to use. In case we didn't match anything, | |
| 868 use no_prediction heuristic, in case we did match, use either | |
| 869 first match or Dempster-Shaffer theory depending on the flags. */ | |
| 870 | |
| 871 if (predictor_info [best_predictor].flags & PRED_FLAG_FIRST_MATCH) | |
| 872 first_match = true; | |
| 873 | |
| 874 if (!found) | |
| 875 dump_prediction (dump_file, PRED_NO_PREDICTION, combined_probability, bb, true); | |
| 876 else | |
| 877 { | |
| 878 dump_prediction (dump_file, PRED_DS_THEORY, combined_probability, bb, | |
| 879 !first_match); | |
| 880 dump_prediction (dump_file, PRED_FIRST_MATCH, best_probability, bb, | |
| 881 first_match); | |
| 882 } | |
| 883 | |
| 884 if (first_match) | |
| 885 combined_probability = best_probability; | |
| 886 dump_prediction (dump_file, PRED_COMBINED, combined_probability, bb, true); | |
| 887 | |
| 888 if (preds) | |
| 889 { | |
| 890 for (pred = (struct edge_prediction *) *preds; pred; pred = pred->ep_next) | |
| 891 { | |
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892 enum br_predictor predictor = pred->ep_predictor; |
| 0 | 893 int probability = pred->ep_probability; |
| 894 | |
| 895 if (pred->ep_edge != EDGE_SUCC (bb, 0)) | |
| 896 probability = REG_BR_PROB_BASE - probability; | |
| 897 dump_prediction (dump_file, predictor, probability, bb, | |
| 898 !first_match || best_predictor == predictor); | |
| 899 } | |
| 900 } | |
| 901 clear_bb_predictions (bb); | |
| 902 | |
| 903 if (!bb->count) | |
| 904 { | |
| 905 first->probability = combined_probability; | |
| 906 second->probability = REG_BR_PROB_BASE - combined_probability; | |
| 907 } | |
| 908 } | |
| 909 | |
| 910 /* Predict edge probabilities by exploiting loop structure. */ | |
| 911 | |
| 912 static void | |
| 913 predict_loops (void) | |
| 914 { | |
| 915 loop_iterator li; | |
| 916 struct loop *loop; | |
| 917 | |
| 918 /* Try to predict out blocks in a loop that are not part of a | |
| 919 natural loop. */ | |
| 920 FOR_EACH_LOOP (li, loop, 0) | |
| 921 { | |
| 922 basic_block bb, *bbs; | |
| 923 unsigned j, n_exits; | |
| 924 VEC (edge, heap) *exits; | |
| 925 struct tree_niter_desc niter_desc; | |
| 926 edge ex; | |
| 927 | |
| 928 exits = get_loop_exit_edges (loop); | |
| 929 n_exits = VEC_length (edge, exits); | |
| 930 | |
| 931 for (j = 0; VEC_iterate (edge, exits, j, ex); j++) | |
| 932 { | |
| 933 tree niter = NULL; | |
| 934 HOST_WIDE_INT nitercst; | |
| 935 int max = PARAM_VALUE (PARAM_MAX_PREDICTED_ITERATIONS); | |
| 936 int probability; | |
| 937 enum br_predictor predictor; | |
| 938 | |
| 939 if (number_of_iterations_exit (loop, ex, &niter_desc, false)) | |
| 940 niter = niter_desc.niter; | |
| 941 if (!niter || TREE_CODE (niter_desc.niter) != INTEGER_CST) | |
| 942 niter = loop_niter_by_eval (loop, ex); | |
| 943 | |
| 944 if (TREE_CODE (niter) == INTEGER_CST) | |
| 945 { | |
| 946 if (host_integerp (niter, 1) | |
| 947 && compare_tree_int (niter, max-1) == -1) | |
| 948 nitercst = tree_low_cst (niter, 1) + 1; | |
| 949 else | |
| 950 nitercst = max; | |
| 951 predictor = PRED_LOOP_ITERATIONS; | |
| 952 } | |
| 953 /* If we have just one exit and we can derive some information about | |
| 954 the number of iterations of the loop from the statements inside | |
| 955 the loop, use it to predict this exit. */ | |
| 956 else if (n_exits == 1) | |
| 957 { | |
| 958 nitercst = estimated_loop_iterations_int (loop, false); | |
| 959 if (nitercst < 0) | |
| 960 continue; | |
| 961 if (nitercst > max) | |
| 962 nitercst = max; | |
| 963 | |
| 964 predictor = PRED_LOOP_ITERATIONS_GUESSED; | |
| 965 } | |
| 966 else | |
| 967 continue; | |
| 968 | |
| 969 probability = ((REG_BR_PROB_BASE + nitercst / 2) / nitercst); | |
| 970 predict_edge (ex, predictor, probability); | |
| 971 } | |
| 972 VEC_free (edge, heap, exits); | |
| 973 | |
| 974 bbs = get_loop_body (loop); | |
| 975 | |
| 976 for (j = 0; j < loop->num_nodes; j++) | |
| 977 { | |
| 978 int header_found = 0; | |
| 979 edge e; | |
| 980 edge_iterator ei; | |
| 981 | |
| 982 bb = bbs[j]; | |
| 983 | |
| 984 /* Bypass loop heuristics on continue statement. These | |
| 985 statements construct loops via "non-loop" constructs | |
| 986 in the source language and are better to be handled | |
| 987 separately. */ | |
| 988 if (predicted_by_p (bb, PRED_CONTINUE)) | |
| 989 continue; | |
| 990 | |
| 991 /* Loop branch heuristics - predict an edge back to a | |
| 992 loop's head as taken. */ | |
| 993 if (bb == loop->latch) | |
| 994 { | |
| 995 e = find_edge (loop->latch, loop->header); | |
| 996 if (e) | |
| 997 { | |
| 998 header_found = 1; | |
| 999 predict_edge_def (e, PRED_LOOP_BRANCH, TAKEN); | |
| 1000 } | |
| 1001 } | |
| 1002 | |
| 1003 /* Loop exit heuristics - predict an edge exiting the loop if the | |
| 1004 conditional has no loop header successors as not taken. */ | |
| 1005 if (!header_found | |
| 1006 /* If we already used more reliable loop exit predictors, do not | |
| 1007 bother with PRED_LOOP_EXIT. */ | |
| 1008 && !predicted_by_p (bb, PRED_LOOP_ITERATIONS_GUESSED) | |
| 1009 && !predicted_by_p (bb, PRED_LOOP_ITERATIONS)) | |
| 1010 { | |
| 1011 /* For loop with many exits we don't want to predict all exits | |
| 1012 with the pretty large probability, because if all exits are | |
| 1013 considered in row, the loop would be predicted to iterate | |
| 1014 almost never. The code to divide probability by number of | |
| 1015 exits is very rough. It should compute the number of exits | |
| 1016 taken in each patch through function (not the overall number | |
| 1017 of exits that might be a lot higher for loops with wide switch | |
| 1018 statements in them) and compute n-th square root. | |
| 1019 | |
| 1020 We limit the minimal probability by 2% to avoid | |
| 1021 EDGE_PROBABILITY_RELIABLE from trusting the branch prediction | |
| 1022 as this was causing regression in perl benchmark containing such | |
| 1023 a wide loop. */ | |
|
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1024 |
| 0 | 1025 int probability = ((REG_BR_PROB_BASE |
| 1026 - predictor_info [(int) PRED_LOOP_EXIT].hitrate) | |
| 1027 / n_exits); | |
| 1028 if (probability < HITRATE (2)) | |
| 1029 probability = HITRATE (2); | |
| 1030 FOR_EACH_EDGE (e, ei, bb->succs) | |
| 1031 if (e->dest->index < NUM_FIXED_BLOCKS | |
| 1032 || !flow_bb_inside_loop_p (loop, e->dest)) | |
| 1033 predict_edge (e, PRED_LOOP_EXIT, probability); | |
| 1034 } | |
| 1035 } | |
|
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1036 |
| 0 | 1037 /* Free basic blocks from get_loop_body. */ |
| 1038 free (bbs); | |
| 1039 } | |
| 1040 } | |
| 1041 | |
| 1042 /* Attempt to predict probabilities of BB outgoing edges using local | |
| 1043 properties. */ | |
| 1044 static void | |
| 1045 bb_estimate_probability_locally (basic_block bb) | |
| 1046 { | |
| 1047 rtx last_insn = BB_END (bb); | |
| 1048 rtx cond; | |
| 1049 | |
| 1050 if (! can_predict_insn_p (last_insn)) | |
| 1051 return; | |
| 1052 cond = get_condition (last_insn, NULL, false, false); | |
| 1053 if (! cond) | |
| 1054 return; | |
| 1055 | |
| 1056 /* Try "pointer heuristic." | |
| 1057 A comparison ptr == 0 is predicted as false. | |
| 1058 Similarly, a comparison ptr1 == ptr2 is predicted as false. */ | |
| 1059 if (COMPARISON_P (cond) | |
| 1060 && ((REG_P (XEXP (cond, 0)) && REG_POINTER (XEXP (cond, 0))) | |
| 1061 || (REG_P (XEXP (cond, 1)) && REG_POINTER (XEXP (cond, 1))))) | |
| 1062 { | |
| 1063 if (GET_CODE (cond) == EQ) | |
| 1064 predict_insn_def (last_insn, PRED_POINTER, NOT_TAKEN); | |
| 1065 else if (GET_CODE (cond) == NE) | |
| 1066 predict_insn_def (last_insn, PRED_POINTER, TAKEN); | |
| 1067 } | |
| 1068 else | |
| 1069 | |
| 1070 /* Try "opcode heuristic." | |
| 1071 EQ tests are usually false and NE tests are usually true. Also, | |
| 1072 most quantities are positive, so we can make the appropriate guesses | |
| 1073 about signed comparisons against zero. */ | |
| 1074 switch (GET_CODE (cond)) | |
| 1075 { | |
| 1076 case CONST_INT: | |
| 1077 /* Unconditional branch. */ | |
| 1078 predict_insn_def (last_insn, PRED_UNCONDITIONAL, | |
| 1079 cond == const0_rtx ? NOT_TAKEN : TAKEN); | |
| 1080 break; | |
| 1081 | |
| 1082 case EQ: | |
| 1083 case UNEQ: | |
| 1084 /* Floating point comparisons appears to behave in a very | |
| 1085 unpredictable way because of special role of = tests in | |
| 1086 FP code. */ | |
| 1087 if (FLOAT_MODE_P (GET_MODE (XEXP (cond, 0)))) | |
| 1088 ; | |
| 1089 /* Comparisons with 0 are often used for booleans and there is | |
| 1090 nothing useful to predict about them. */ | |
| 1091 else if (XEXP (cond, 1) == const0_rtx | |
| 1092 || XEXP (cond, 0) == const0_rtx) | |
| 1093 ; | |
| 1094 else | |
| 1095 predict_insn_def (last_insn, PRED_OPCODE_NONEQUAL, NOT_TAKEN); | |
| 1096 break; | |
| 1097 | |
| 1098 case NE: | |
| 1099 case LTGT: | |
| 1100 /* Floating point comparisons appears to behave in a very | |
| 1101 unpredictable way because of special role of = tests in | |
| 1102 FP code. */ | |
| 1103 if (FLOAT_MODE_P (GET_MODE (XEXP (cond, 0)))) | |
| 1104 ; | |
| 1105 /* Comparisons with 0 are often used for booleans and there is | |
| 1106 nothing useful to predict about them. */ | |
| 1107 else if (XEXP (cond, 1) == const0_rtx | |
| 1108 || XEXP (cond, 0) == const0_rtx) | |
| 1109 ; | |
| 1110 else | |
| 1111 predict_insn_def (last_insn, PRED_OPCODE_NONEQUAL, TAKEN); | |
| 1112 break; | |
| 1113 | |
| 1114 case ORDERED: | |
| 1115 predict_insn_def (last_insn, PRED_FPOPCODE, TAKEN); | |
| 1116 break; | |
| 1117 | |
| 1118 case UNORDERED: | |
| 1119 predict_insn_def (last_insn, PRED_FPOPCODE, NOT_TAKEN); | |
| 1120 break; | |
| 1121 | |
| 1122 case LE: | |
| 1123 case LT: | |
| 1124 if (XEXP (cond, 1) == const0_rtx || XEXP (cond, 1) == const1_rtx | |
| 1125 || XEXP (cond, 1) == constm1_rtx) | |
| 1126 predict_insn_def (last_insn, PRED_OPCODE_POSITIVE, NOT_TAKEN); | |
| 1127 break; | |
| 1128 | |
| 1129 case GE: | |
| 1130 case GT: | |
| 1131 if (XEXP (cond, 1) == const0_rtx || XEXP (cond, 1) == const1_rtx | |
| 1132 || XEXP (cond, 1) == constm1_rtx) | |
| 1133 predict_insn_def (last_insn, PRED_OPCODE_POSITIVE, TAKEN); | |
| 1134 break; | |
| 1135 | |
| 1136 default: | |
| 1137 break; | |
| 1138 } | |
| 1139 } | |
| 1140 | |
| 1141 /* Set edge->probability for each successor edge of BB. */ | |
| 1142 void | |
| 1143 guess_outgoing_edge_probabilities (basic_block bb) | |
| 1144 { | |
| 1145 bb_estimate_probability_locally (bb); | |
| 1146 combine_predictions_for_insn (BB_END (bb), bb); | |
| 1147 } | |
| 1148 | |
| 1149 static tree expr_expected_value (tree, bitmap); | |
| 1150 | |
| 1151 /* Helper function for expr_expected_value. */ | |
| 1152 | |
| 1153 static tree | |
| 1154 expr_expected_value_1 (tree type, tree op0, enum tree_code code, tree op1, bitmap visited) | |
| 1155 { | |
| 1156 gimple def; | |
| 1157 | |
| 1158 if (get_gimple_rhs_class (code) == GIMPLE_SINGLE_RHS) | |
| 1159 { | |
| 1160 if (TREE_CONSTANT (op0)) | |
| 1161 return op0; | |
| 1162 | |
| 1163 if (code != SSA_NAME) | |
| 1164 return NULL_TREE; | |
| 1165 | |
| 1166 def = SSA_NAME_DEF_STMT (op0); | |
| 1167 | |
| 1168 /* If we were already here, break the infinite cycle. */ | |
| 1169 if (bitmap_bit_p (visited, SSA_NAME_VERSION (op0))) | |
| 1170 return NULL; | |
| 1171 bitmap_set_bit (visited, SSA_NAME_VERSION (op0)); | |
| 1172 | |
| 1173 if (gimple_code (def) == GIMPLE_PHI) | |
| 1174 { | |
| 1175 /* All the arguments of the PHI node must have the same constant | |
| 1176 length. */ | |
| 1177 int i, n = gimple_phi_num_args (def); | |
| 1178 tree val = NULL, new_val; | |
| 1179 | |
| 1180 for (i = 0; i < n; i++) | |
| 1181 { | |
| 1182 tree arg = PHI_ARG_DEF (def, i); | |
| 1183 | |
| 1184 /* If this PHI has itself as an argument, we cannot | |
| 1185 determine the string length of this argument. However, | |
| 1186 if we can find an expected constant value for the other | |
| 1187 PHI args then we can still be sure that this is | |
| 1188 likely a constant. So be optimistic and just | |
| 1189 continue with the next argument. */ | |
| 1190 if (arg == PHI_RESULT (def)) | |
| 1191 continue; | |
| 1192 | |
| 1193 new_val = expr_expected_value (arg, visited); | |
| 1194 if (!new_val) | |
| 1195 return NULL; | |
| 1196 if (!val) | |
| 1197 val = new_val; | |
| 1198 else if (!operand_equal_p (val, new_val, false)) | |
| 1199 return NULL; | |
| 1200 } | |
| 1201 return val; | |
| 1202 } | |
| 1203 if (is_gimple_assign (def)) | |
| 1204 { | |
| 1205 if (gimple_assign_lhs (def) != op0) | |
| 1206 return NULL; | |
| 1207 | |
| 1208 return expr_expected_value_1 (TREE_TYPE (gimple_assign_lhs (def)), | |
| 1209 gimple_assign_rhs1 (def), | |
| 1210 gimple_assign_rhs_code (def), | |
| 1211 gimple_assign_rhs2 (def), | |
| 1212 visited); | |
| 1213 } | |
| 1214 | |
| 1215 if (is_gimple_call (def)) | |
| 1216 { | |
| 1217 tree decl = gimple_call_fndecl (def); | |
| 1218 if (!decl) | |
| 1219 return NULL; | |
| 1220 if (DECL_BUILT_IN_CLASS (decl) == BUILT_IN_NORMAL | |
| 1221 && DECL_FUNCTION_CODE (decl) == BUILT_IN_EXPECT) | |
| 1222 { | |
| 1223 tree val; | |
| 1224 | |
| 1225 if (gimple_call_num_args (def) != 2) | |
| 1226 return NULL; | |
| 1227 val = gimple_call_arg (def, 0); | |
| 1228 if (TREE_CONSTANT (val)) | |
| 1229 return val; | |
| 1230 return gimple_call_arg (def, 1); | |
| 1231 } | |
| 1232 } | |
| 1233 | |
| 1234 return NULL; | |
| 1235 } | |
| 1236 | |
| 1237 if (get_gimple_rhs_class (code) == GIMPLE_BINARY_RHS) | |
| 1238 { | |
| 1239 tree res; | |
| 1240 op0 = expr_expected_value (op0, visited); | |
| 1241 if (!op0) | |
| 1242 return NULL; | |
| 1243 op1 = expr_expected_value (op1, visited); | |
| 1244 if (!op1) | |
| 1245 return NULL; | |
| 1246 res = fold_build2 (code, type, op0, op1); | |
| 1247 if (TREE_CONSTANT (res)) | |
| 1248 return res; | |
| 1249 return NULL; | |
| 1250 } | |
| 1251 if (get_gimple_rhs_class (code) == GIMPLE_UNARY_RHS) | |
| 1252 { | |
| 1253 tree res; | |
| 1254 op0 = expr_expected_value (op0, visited); | |
| 1255 if (!op0) | |
| 1256 return NULL; | |
| 1257 res = fold_build1 (code, type, op0); | |
| 1258 if (TREE_CONSTANT (res)) | |
| 1259 return res; | |
| 1260 return NULL; | |
| 1261 } | |
| 1262 return NULL; | |
| 1263 } | |
| 1264 | |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
1265 /* Return constant EXPR will likely have at execution time, NULL if unknown. |
| 0 | 1266 The function is used by builtin_expect branch predictor so the evidence |
| 1267 must come from this construct and additional possible constant folding. | |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
1268 |
| 0 | 1269 We may want to implement more involved value guess (such as value range |
| 1270 propagation based prediction), but such tricks shall go to new | |
| 1271 implementation. */ | |
| 1272 | |
| 1273 static tree | |
| 1274 expr_expected_value (tree expr, bitmap visited) | |
| 1275 { | |
| 1276 enum tree_code code; | |
| 1277 tree op0, op1; | |
| 1278 | |
| 1279 if (TREE_CONSTANT (expr)) | |
| 1280 return expr; | |
| 1281 | |
| 1282 extract_ops_from_tree (expr, &code, &op0, &op1); | |
| 1283 return expr_expected_value_1 (TREE_TYPE (expr), | |
| 1284 op0, code, op1, visited); | |
| 1285 } | |
| 1286 | |
| 1287 | |
| 1288 /* Get rid of all builtin_expect calls and GIMPLE_PREDICT statements | |
| 1289 we no longer need. */ | |
| 1290 static unsigned int | |
| 1291 strip_predict_hints (void) | |
| 1292 { | |
| 1293 basic_block bb; | |
| 1294 gimple ass_stmt; | |
| 1295 tree var; | |
| 1296 | |
| 1297 FOR_EACH_BB (bb) | |
| 1298 { | |
| 1299 gimple_stmt_iterator bi; | |
| 1300 for (bi = gsi_start_bb (bb); !gsi_end_p (bi);) | |
| 1301 { | |
| 1302 gimple stmt = gsi_stmt (bi); | |
| 1303 | |
| 1304 if (gimple_code (stmt) == GIMPLE_PREDICT) | |
| 1305 { | |
| 1306 gsi_remove (&bi, true); | |
| 1307 continue; | |
| 1308 } | |
| 1309 else if (gimple_code (stmt) == GIMPLE_CALL) | |
| 1310 { | |
| 1311 tree fndecl = gimple_call_fndecl (stmt); | |
| 1312 | |
| 1313 if (fndecl | |
| 1314 && DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL | |
| 1315 && DECL_FUNCTION_CODE (fndecl) == BUILT_IN_EXPECT | |
| 1316 && gimple_call_num_args (stmt) == 2) | |
| 1317 { | |
| 1318 var = gimple_call_lhs (stmt); | |
| 1319 ass_stmt = gimple_build_assign (var, gimple_call_arg (stmt, 0)); | |
| 1320 | |
| 1321 gsi_replace (&bi, ass_stmt, true); | |
| 1322 } | |
| 1323 } | |
| 1324 gsi_next (&bi); | |
| 1325 } | |
| 1326 } | |
| 1327 return 0; | |
| 1328 } | |
| 1329 | |
| 1330 /* Predict using opcode of the last statement in basic block. */ | |
| 1331 static void | |
| 1332 tree_predict_by_opcode (basic_block bb) | |
| 1333 { | |
| 1334 gimple stmt = last_stmt (bb); | |
| 1335 edge then_edge; | |
| 1336 tree op0, op1; | |
| 1337 tree type; | |
| 1338 tree val; | |
| 1339 enum tree_code cmp; | |
| 1340 bitmap visited; | |
| 1341 edge_iterator ei; | |
| 1342 | |
| 1343 if (!stmt || gimple_code (stmt) != GIMPLE_COND) | |
| 1344 return; | |
| 1345 FOR_EACH_EDGE (then_edge, ei, bb->succs) | |
| 1346 if (then_edge->flags & EDGE_TRUE_VALUE) | |
| 1347 break; | |
| 1348 op0 = gimple_cond_lhs (stmt); | |
| 1349 op1 = gimple_cond_rhs (stmt); | |
| 1350 cmp = gimple_cond_code (stmt); | |
| 1351 type = TREE_TYPE (op0); | |
| 1352 visited = BITMAP_ALLOC (NULL); | |
| 1353 val = expr_expected_value_1 (boolean_type_node, op0, cmp, op1, visited); | |
| 1354 BITMAP_FREE (visited); | |
| 1355 if (val) | |
| 1356 { | |
| 1357 if (integer_zerop (val)) | |
| 1358 predict_edge_def (then_edge, PRED_BUILTIN_EXPECT, NOT_TAKEN); | |
| 1359 else | |
| 1360 predict_edge_def (then_edge, PRED_BUILTIN_EXPECT, TAKEN); | |
| 1361 return; | |
| 1362 } | |
| 1363 /* Try "pointer heuristic." | |
| 1364 A comparison ptr == 0 is predicted as false. | |
| 1365 Similarly, a comparison ptr1 == ptr2 is predicted as false. */ | |
| 1366 if (POINTER_TYPE_P (type)) | |
| 1367 { | |
| 1368 if (cmp == EQ_EXPR) | |
| 1369 predict_edge_def (then_edge, PRED_TREE_POINTER, NOT_TAKEN); | |
| 1370 else if (cmp == NE_EXPR) | |
| 1371 predict_edge_def (then_edge, PRED_TREE_POINTER, TAKEN); | |
| 1372 } | |
| 1373 else | |
| 1374 | |
| 1375 /* Try "opcode heuristic." | |
| 1376 EQ tests are usually false and NE tests are usually true. Also, | |
| 1377 most quantities are positive, so we can make the appropriate guesses | |
| 1378 about signed comparisons against zero. */ | |
| 1379 switch (cmp) | |
| 1380 { | |
| 1381 case EQ_EXPR: | |
| 1382 case UNEQ_EXPR: | |
| 1383 /* Floating point comparisons appears to behave in a very | |
| 1384 unpredictable way because of special role of = tests in | |
| 1385 FP code. */ | |
| 1386 if (FLOAT_TYPE_P (type)) | |
| 1387 ; | |
| 1388 /* Comparisons with 0 are often used for booleans and there is | |
| 1389 nothing useful to predict about them. */ | |
| 1390 else if (integer_zerop (op0) || integer_zerop (op1)) | |
| 1391 ; | |
| 1392 else | |
| 1393 predict_edge_def (then_edge, PRED_TREE_OPCODE_NONEQUAL, NOT_TAKEN); | |
| 1394 break; | |
| 1395 | |
| 1396 case NE_EXPR: | |
| 1397 case LTGT_EXPR: | |
| 1398 /* Floating point comparisons appears to behave in a very | |
| 1399 unpredictable way because of special role of = tests in | |
| 1400 FP code. */ | |
| 1401 if (FLOAT_TYPE_P (type)) | |
| 1402 ; | |
| 1403 /* Comparisons with 0 are often used for booleans and there is | |
| 1404 nothing useful to predict about them. */ | |
| 1405 else if (integer_zerop (op0) | |
| 1406 || integer_zerop (op1)) | |
| 1407 ; | |
| 1408 else | |
| 1409 predict_edge_def (then_edge, PRED_TREE_OPCODE_NONEQUAL, TAKEN); | |
| 1410 break; | |
| 1411 | |
| 1412 case ORDERED_EXPR: | |
| 1413 predict_edge_def (then_edge, PRED_TREE_FPOPCODE, TAKEN); | |
| 1414 break; | |
| 1415 | |
| 1416 case UNORDERED_EXPR: | |
| 1417 predict_edge_def (then_edge, PRED_TREE_FPOPCODE, NOT_TAKEN); | |
| 1418 break; | |
| 1419 | |
| 1420 case LE_EXPR: | |
| 1421 case LT_EXPR: | |
| 1422 if (integer_zerop (op1) | |
| 1423 || integer_onep (op1) | |
| 1424 || integer_all_onesp (op1) | |
| 1425 || real_zerop (op1) | |
| 1426 || real_onep (op1) | |
| 1427 || real_minus_onep (op1)) | |
| 1428 predict_edge_def (then_edge, PRED_TREE_OPCODE_POSITIVE, NOT_TAKEN); | |
| 1429 break; | |
| 1430 | |
| 1431 case GE_EXPR: | |
| 1432 case GT_EXPR: | |
| 1433 if (integer_zerop (op1) | |
| 1434 || integer_onep (op1) | |
| 1435 || integer_all_onesp (op1) | |
| 1436 || real_zerop (op1) | |
| 1437 || real_onep (op1) | |
| 1438 || real_minus_onep (op1)) | |
| 1439 predict_edge_def (then_edge, PRED_TREE_OPCODE_POSITIVE, TAKEN); | |
| 1440 break; | |
| 1441 | |
| 1442 default: | |
| 1443 break; | |
| 1444 } | |
| 1445 } | |
| 1446 | |
| 1447 /* Try to guess whether the value of return means error code. */ | |
| 1448 | |
| 1449 static enum br_predictor | |
| 1450 return_prediction (tree val, enum prediction *prediction) | |
| 1451 { | |
| 1452 /* VOID. */ | |
| 1453 if (!val) | |
| 1454 return PRED_NO_PREDICTION; | |
| 1455 /* Different heuristics for pointers and scalars. */ | |
| 1456 if (POINTER_TYPE_P (TREE_TYPE (val))) | |
| 1457 { | |
| 1458 /* NULL is usually not returned. */ | |
| 1459 if (integer_zerop (val)) | |
| 1460 { | |
| 1461 *prediction = NOT_TAKEN; | |
| 1462 return PRED_NULL_RETURN; | |
| 1463 } | |
| 1464 } | |
| 1465 else if (INTEGRAL_TYPE_P (TREE_TYPE (val))) | |
| 1466 { | |
| 1467 /* Negative return values are often used to indicate | |
| 1468 errors. */ | |
| 1469 if (TREE_CODE (val) == INTEGER_CST | |
| 1470 && tree_int_cst_sgn (val) < 0) | |
| 1471 { | |
| 1472 *prediction = NOT_TAKEN; | |
| 1473 return PRED_NEGATIVE_RETURN; | |
| 1474 } | |
| 1475 /* Constant return values seems to be commonly taken. | |
| 1476 Zero/one often represent booleans so exclude them from the | |
| 1477 heuristics. */ | |
| 1478 if (TREE_CONSTANT (val) | |
| 1479 && (!integer_zerop (val) && !integer_onep (val))) | |
| 1480 { | |
| 1481 *prediction = TAKEN; | |
| 1482 return PRED_CONST_RETURN; | |
| 1483 } | |
| 1484 } | |
| 1485 return PRED_NO_PREDICTION; | |
| 1486 } | |
| 1487 | |
| 1488 /* Find the basic block with return expression and look up for possible | |
| 1489 return value trying to apply RETURN_PREDICTION heuristics. */ | |
| 1490 static void | |
| 1491 apply_return_prediction (void) | |
| 1492 { | |
| 1493 gimple return_stmt = NULL; | |
| 1494 tree return_val; | |
| 1495 edge e; | |
| 1496 gimple phi; | |
| 1497 int phi_num_args, i; | |
| 1498 enum br_predictor pred; | |
| 1499 enum prediction direction; | |
| 1500 edge_iterator ei; | |
| 1501 | |
| 1502 FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds) | |
| 1503 { | |
| 1504 return_stmt = last_stmt (e->src); | |
| 1505 if (return_stmt | |
| 1506 && gimple_code (return_stmt) == GIMPLE_RETURN) | |
| 1507 break; | |
| 1508 } | |
| 1509 if (!e) | |
| 1510 return; | |
| 1511 return_val = gimple_return_retval (return_stmt); | |
| 1512 if (!return_val) | |
| 1513 return; | |
| 1514 if (TREE_CODE (return_val) != SSA_NAME | |
| 1515 || !SSA_NAME_DEF_STMT (return_val) | |
| 1516 || gimple_code (SSA_NAME_DEF_STMT (return_val)) != GIMPLE_PHI) | |
| 1517 return; | |
| 1518 phi = SSA_NAME_DEF_STMT (return_val); | |
| 1519 phi_num_args = gimple_phi_num_args (phi); | |
| 1520 pred = return_prediction (PHI_ARG_DEF (phi, 0), &direction); | |
| 1521 | |
| 1522 /* Avoid the degenerate case where all return values form the function | |
| 1523 belongs to same category (ie they are all positive constants) | |
| 1524 so we can hardly say something about them. */ | |
| 1525 for (i = 1; i < phi_num_args; i++) | |
| 1526 if (pred != return_prediction (PHI_ARG_DEF (phi, i), &direction)) | |
| 1527 break; | |
| 1528 if (i != phi_num_args) | |
| 1529 for (i = 0; i < phi_num_args; i++) | |
| 1530 { | |
| 1531 pred = return_prediction (PHI_ARG_DEF (phi, i), &direction); | |
| 1532 if (pred != PRED_NO_PREDICTION) | |
| 1533 predict_paths_leading_to (gimple_phi_arg_edge (phi, i)->src, pred, | |
| 1534 direction); | |
| 1535 } | |
| 1536 } | |
| 1537 | |
| 1538 /* Look for basic block that contains unlikely to happen events | |
| 1539 (such as noreturn calls) and mark all paths leading to execution | |
| 1540 of this basic blocks as unlikely. */ | |
| 1541 | |
| 1542 static void | |
| 1543 tree_bb_level_predictions (void) | |
| 1544 { | |
| 1545 basic_block bb; | |
| 1546 bool has_return_edges = false; | |
| 1547 edge e; | |
| 1548 edge_iterator ei; | |
| 1549 | |
| 1550 FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds) | |
| 1551 if (!(e->flags & (EDGE_ABNORMAL | EDGE_FAKE | EDGE_EH))) | |
| 1552 { | |
| 1553 has_return_edges = true; | |
| 1554 break; | |
| 1555 } | |
| 1556 | |
| 1557 apply_return_prediction (); | |
| 1558 | |
| 1559 FOR_EACH_BB (bb) | |
| 1560 { | |
| 1561 gimple_stmt_iterator gsi; | |
| 1562 | |
| 1563 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) | |
| 1564 { | |
| 1565 gimple stmt = gsi_stmt (gsi); | |
| 1566 tree decl; | |
| 1567 | |
| 1568 if (is_gimple_call (stmt)) | |
| 1569 { | |
| 1570 if ((gimple_call_flags (stmt) & ECF_NORETURN) | |
| 1571 && has_return_edges) | |
| 1572 predict_paths_leading_to (bb, PRED_NORETURN, | |
| 1573 NOT_TAKEN); | |
| 1574 decl = gimple_call_fndecl (stmt); | |
| 1575 if (decl | |
| 1576 && lookup_attribute ("cold", | |
| 1577 DECL_ATTRIBUTES (decl))) | |
| 1578 predict_paths_leading_to (bb, PRED_COLD_FUNCTION, | |
| 1579 NOT_TAKEN); | |
| 1580 } | |
| 1581 else if (gimple_code (stmt) == GIMPLE_PREDICT) | |
| 1582 { | |
| 1583 predict_paths_leading_to (bb, gimple_predict_predictor (stmt), | |
| 1584 gimple_predict_outcome (stmt)); | |
| 1585 /* Keep GIMPLE_PREDICT around so early inlining will propagate | |
| 1586 hints to callers. */ | |
| 1587 } | |
| 1588 } | |
| 1589 } | |
| 1590 } | |
| 1591 | |
| 1592 #ifdef ENABLE_CHECKING | |
| 1593 | |
| 1594 /* Callback for pointer_map_traverse, asserts that the pointer map is | |
| 1595 empty. */ | |
| 1596 | |
| 1597 static bool | |
| 1598 assert_is_empty (const void *key ATTRIBUTE_UNUSED, void **value, | |
| 1599 void *data ATTRIBUTE_UNUSED) | |
| 1600 { | |
| 1601 gcc_assert (!*value); | |
| 1602 return false; | |
| 1603 } | |
| 1604 #endif | |
| 1605 | |
|
55
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|
1606 /* Predict branch probabilities and estimate profile for basic block BB. */ |
|
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|
1607 |
|
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diff
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|
1608 static void |
|
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diff
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|
1609 tree_estimate_probability_bb (basic_block bb) |
|
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|
1610 { |
|
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|
1611 edge e; |
|
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|
1612 edge_iterator ei; |
|
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|
1613 gimple last; |
|
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|
1614 |
|
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|
1615 FOR_EACH_EDGE (e, ei, bb->succs) |
|
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|
1616 { |
|
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|
1617 /* Predict early returns to be probable, as we've already taken |
|
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|
1618 care for error returns and other cases are often used for |
|
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|
1619 fast paths through function. |
|
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|
1620 |
|
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|
1621 Since we've already removed the return statements, we are |
|
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|
1622 looking for CFG like: |
|
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|
1623 |
|
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|
1624 if (conditional) |
|
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|
1625 { |
|
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|
1626 .. |
|
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|
1627 goto return_block |
|
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|
1628 } |
|
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|
1629 some other blocks |
|
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|
1630 return_block: |
|
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|
1631 return_stmt. */ |
|
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0
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|
1632 if (e->dest != bb->next_bb |
|
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|
1633 && e->dest != EXIT_BLOCK_PTR |
|
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|
1634 && single_succ_p (e->dest) |
|
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|
1635 && single_succ_edge (e->dest)->dest == EXIT_BLOCK_PTR |
|
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|
1636 && (last = last_stmt (e->dest)) != NULL |
|
77e2b8dfacca
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|
1637 && gimple_code (last) == GIMPLE_RETURN) |
|
77e2b8dfacca
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0
diff
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|
1638 { |
|
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0
diff
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|
1639 edge e1; |
|
77e2b8dfacca
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0
diff
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|
1640 edge_iterator ei1; |
|
77e2b8dfacca
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0
diff
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|
1641 |
|
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0
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|
1642 if (single_succ_p (bb)) |
|
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diff
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|
1643 { |
|
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parents:
0
diff
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|
1644 FOR_EACH_EDGE (e1, ei1, bb->preds) |
|
77e2b8dfacca
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parents:
0
diff
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|
1645 if (!predicted_by_p (e1->src, PRED_NULL_RETURN) |
|
77e2b8dfacca
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parents:
0
diff
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|
1646 && !predicted_by_p (e1->src, PRED_CONST_RETURN) |
|
77e2b8dfacca
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parents:
0
diff
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|
1647 && !predicted_by_p (e1->src, PRED_NEGATIVE_RETURN)) |
|
77e2b8dfacca
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parents:
0
diff
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|
1648 predict_edge_def (e1, PRED_TREE_EARLY_RETURN, NOT_TAKEN); |
|
77e2b8dfacca
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0
diff
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|
1649 } |
|
77e2b8dfacca
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parents:
0
diff
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|
1650 else |
|
77e2b8dfacca
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parents:
0
diff
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|
1651 if (!predicted_by_p (e->src, PRED_NULL_RETURN) |
|
77e2b8dfacca
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parents:
0
diff
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|
1652 && !predicted_by_p (e->src, PRED_CONST_RETURN) |
|
77e2b8dfacca
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0
diff
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|
1653 && !predicted_by_p (e->src, PRED_NEGATIVE_RETURN)) |
|
77e2b8dfacca
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0
diff
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|
1654 predict_edge_def (e, PRED_TREE_EARLY_RETURN, NOT_TAKEN); |
|
77e2b8dfacca
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|
1655 } |
|
77e2b8dfacca
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0
diff
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|
1656 |
|
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0
diff
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|
1657 /* Look for block we are guarding (ie we dominate it, |
|
77e2b8dfacca
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parents:
0
diff
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|
1658 but it doesn't postdominate us). */ |
|
77e2b8dfacca
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0
diff
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|
1659 if (e->dest != EXIT_BLOCK_PTR && e->dest != bb |
|
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0
diff
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|
1660 && dominated_by_p (CDI_DOMINATORS, e->dest, e->src) |
|
77e2b8dfacca
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0
diff
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|
1661 && !dominated_by_p (CDI_POST_DOMINATORS, e->src, e->dest)) |
|
77e2b8dfacca
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diff
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|
1662 { |
|
77e2b8dfacca
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0
diff
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|
1663 gimple_stmt_iterator bi; |
|
77e2b8dfacca
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0
diff
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|
1664 |
|
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0
diff
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|
1665 /* The call heuristic claims that a guarded function call |
|
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0
diff
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|
1666 is improbable. This is because such calls are often used |
|
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diff
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|
1667 to signal exceptional situations such as printing error |
|
77e2b8dfacca
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diff
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|
1668 messages. */ |
|
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|
1669 for (bi = gsi_start_bb (e->dest); !gsi_end_p (bi); |
|
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|
1670 gsi_next (&bi)) |
|
77e2b8dfacca
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|
1671 { |
|
77e2b8dfacca
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|
1672 gimple stmt = gsi_stmt (bi); |
|
77e2b8dfacca
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|
1673 if (is_gimple_call (stmt) |
|
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diff
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|
1674 /* Constant and pure calls are hardly used to signalize |
|
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0
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|
1675 something exceptional. */ |
|
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|
1676 && gimple_has_side_effects (stmt)) |
|
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|
1677 { |
|
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|
1678 predict_edge_def (e, PRED_CALL, NOT_TAKEN); |
|
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|
1679 break; |
|
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|
1680 } |
|
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|
1681 } |
|
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|
1682 } |
|
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|
1683 } |
|
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|
1684 tree_predict_by_opcode (bb); |
|
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|
1685 } |
|
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|
1686 |
|
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|
1687 /* Predict branch probabilities and estimate profile of the tree CFG. |
|
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|
1688 This function can be called from the loop optimizers to recompute |
|
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|
1689 the profile information. */ |
|
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|
1690 |
|
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|
1691 void |
| 0 | 1692 tree_estimate_probability (void) |
| 1693 { | |
| 1694 basic_block bb; | |
| 1695 | |
| 1696 add_noreturn_fake_exit_edges (); | |
| 1697 connect_infinite_loops_to_exit (); | |
| 1698 /* We use loop_niter_by_eval, which requires that the loops have | |
| 1699 preheaders. */ | |
| 1700 create_preheaders (CP_SIMPLE_PREHEADERS); | |
| 1701 calculate_dominance_info (CDI_POST_DOMINATORS); | |
| 1702 | |
| 1703 bb_predictions = pointer_map_create (); | |
| 1704 tree_bb_level_predictions (); | |
|
55
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|
1705 record_loop_exits (); |
| 0 | 1706 |
| 1707 if (number_of_loops () > 1) | |
| 1708 predict_loops (); | |
| 1709 | |
| 1710 FOR_EACH_BB (bb) | |
|
55
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|
1711 tree_estimate_probability_bb (bb); |
| 0 | 1712 |
| 1713 FOR_EACH_BB (bb) | |
| 1714 combine_predictions_for_bb (bb); | |
| 1715 | |
| 1716 #ifdef ENABLE_CHECKING | |
| 1717 pointer_map_traverse (bb_predictions, assert_is_empty, NULL); | |
| 1718 #endif | |
| 1719 pointer_map_destroy (bb_predictions); | |
| 1720 bb_predictions = NULL; | |
| 1721 | |
| 1722 estimate_bb_frequencies (); | |
| 1723 free_dominance_info (CDI_POST_DOMINATORS); | |
| 1724 remove_fake_exit_edges (); | |
|
55
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|
1725 } |
|
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|
1726 |
|
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|
1727 /* Predict branch probabilities and estimate profile of the tree CFG. |
|
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|
1728 This is the driver function for PASS_PROFILE. */ |
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1729 |
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1730 static unsigned int |
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1731 tree_estimate_probability_driver (void) |
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1732 { |
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1733 unsigned nb_loops; |
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1734 |
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1735 loop_optimizer_init (0); |
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1736 if (dump_file && (dump_flags & TDF_DETAILS)) |
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1737 flow_loops_dump (dump_file, NULL, 0); |
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1738 |
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1739 mark_irreducible_loops (); |
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1740 |
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1741 nb_loops = number_of_loops (); |
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1742 if (nb_loops > 1) |
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1743 scev_initialize (); |
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1744 |
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1745 tree_estimate_probability (); |
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1746 |
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1747 if (nb_loops > 1) |
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1748 scev_finalize (); |
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1749 |
| 0 | 1750 loop_optimizer_finalize (); |
| 1751 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 1752 gimple_dump_cfg (dump_file, dump_flags); | |
| 1753 if (profile_status == PROFILE_ABSENT) | |
| 1754 profile_status = PROFILE_GUESSED; | |
| 1755 return 0; | |
| 1756 } | |
| 1757 | |
| 1758 /* Predict edges to successors of CUR whose sources are not postdominated by | |
| 1759 BB by PRED and recurse to all postdominators. */ | |
| 1760 | |
| 1761 static void | |
| 1762 predict_paths_for_bb (basic_block cur, basic_block bb, | |
| 1763 enum br_predictor pred, | |
| 1764 enum prediction taken) | |
| 1765 { | |
| 1766 edge e; | |
| 1767 edge_iterator ei; | |
| 1768 basic_block son; | |
| 1769 | |
| 1770 /* We are looking for all edges forming edge cut induced by | |
| 1771 set of all blocks postdominated by BB. */ | |
| 1772 FOR_EACH_EDGE (e, ei, cur->preds) | |
| 1773 if (e->src->index >= NUM_FIXED_BLOCKS | |
| 1774 && !dominated_by_p (CDI_POST_DOMINATORS, e->src, bb)) | |
| 1775 { | |
| 1776 gcc_assert (bb == cur || dominated_by_p (CDI_POST_DOMINATORS, cur, bb)); | |
| 1777 predict_edge_def (e, pred, taken); | |
| 1778 } | |
| 1779 for (son = first_dom_son (CDI_POST_DOMINATORS, cur); | |
| 1780 son; | |
| 1781 son = next_dom_son (CDI_POST_DOMINATORS, son)) | |
| 1782 predict_paths_for_bb (son, bb, pred, taken); | |
| 1783 } | |
| 1784 | |
| 1785 /* Sets branch probabilities according to PREDiction and | |
| 1786 FLAGS. */ | |
| 1787 | |
| 1788 static void | |
| 1789 predict_paths_leading_to (basic_block bb, enum br_predictor pred, | |
| 1790 enum prediction taken) | |
| 1791 { | |
| 1792 predict_paths_for_bb (bb, bb, pred, taken); | |
| 1793 } | |
| 1794 | |
| 1795 /* This is used to carry information about basic blocks. It is | |
| 1796 attached to the AUX field of the standard CFG block. */ | |
| 1797 | |
| 1798 typedef struct block_info_def | |
| 1799 { | |
| 1800 /* Estimated frequency of execution of basic_block. */ | |
| 1801 sreal frequency; | |
| 1802 | |
| 1803 /* To keep queue of basic blocks to process. */ | |
| 1804 basic_block next; | |
| 1805 | |
| 1806 /* Number of predecessors we need to visit first. */ | |
| 1807 int npredecessors; | |
| 1808 } *block_info; | |
| 1809 | |
| 1810 /* Similar information for edges. */ | |
| 1811 typedef struct edge_info_def | |
| 1812 { | |
| 1813 /* In case edge is a loopback edge, the probability edge will be reached | |
| 1814 in case header is. Estimated number of iterations of the loop can be | |
| 1815 then computed as 1 / (1 - back_edge_prob). */ | |
| 1816 sreal back_edge_prob; | |
| 1817 /* True if the edge is a loopback edge in the natural loop. */ | |
| 1818 unsigned int back_edge:1; | |
| 1819 } *edge_info; | |
| 1820 | |
| 1821 #define BLOCK_INFO(B) ((block_info) (B)->aux) | |
| 1822 #define EDGE_INFO(E) ((edge_info) (E)->aux) | |
| 1823 | |
| 1824 /* Helper function for estimate_bb_frequencies. | |
| 1825 Propagate the frequencies in blocks marked in | |
| 1826 TOVISIT, starting in HEAD. */ | |
| 1827 | |
| 1828 static void | |
| 1829 propagate_freq (basic_block head, bitmap tovisit) | |
| 1830 { | |
| 1831 basic_block bb; | |
| 1832 basic_block last; | |
| 1833 unsigned i; | |
| 1834 edge e; | |
| 1835 basic_block nextbb; | |
| 1836 bitmap_iterator bi; | |
| 1837 | |
| 1838 /* For each basic block we need to visit count number of his predecessors | |
| 1839 we need to visit first. */ | |
| 1840 EXECUTE_IF_SET_IN_BITMAP (tovisit, 0, i, bi) | |
| 1841 { | |
| 1842 edge_iterator ei; | |
| 1843 int count = 0; | |
| 1844 | |
| 1845 /* The outermost "loop" includes the exit block, which we can not | |
| 1846 look up via BASIC_BLOCK. Detect this and use EXIT_BLOCK_PTR | |
| 1847 directly. Do the same for the entry block. */ | |
| 1848 bb = BASIC_BLOCK (i); | |
| 1849 | |
| 1850 FOR_EACH_EDGE (e, ei, bb->preds) | |
| 1851 { | |
| 1852 bool visit = bitmap_bit_p (tovisit, e->src->index); | |
| 1853 | |
| 1854 if (visit && !(e->flags & EDGE_DFS_BACK)) | |
| 1855 count++; | |
| 1856 else if (visit && dump_file && !EDGE_INFO (e)->back_edge) | |
| 1857 fprintf (dump_file, | |
| 1858 "Irreducible region hit, ignoring edge to %i->%i\n", | |
| 1859 e->src->index, bb->index); | |
| 1860 } | |
| 1861 BLOCK_INFO (bb)->npredecessors = count; | |
| 1862 } | |
| 1863 | |
| 1864 memcpy (&BLOCK_INFO (head)->frequency, &real_one, sizeof (real_one)); | |
| 1865 last = head; | |
| 1866 for (bb = head; bb; bb = nextbb) | |
| 1867 { | |
| 1868 edge_iterator ei; | |
| 1869 sreal cyclic_probability, frequency; | |
| 1870 | |
| 1871 memcpy (&cyclic_probability, &real_zero, sizeof (real_zero)); | |
| 1872 memcpy (&frequency, &real_zero, sizeof (real_zero)); | |
| 1873 | |
| 1874 nextbb = BLOCK_INFO (bb)->next; | |
| 1875 BLOCK_INFO (bb)->next = NULL; | |
| 1876 | |
| 1877 /* Compute frequency of basic block. */ | |
| 1878 if (bb != head) | |
| 1879 { | |
| 1880 #ifdef ENABLE_CHECKING | |
| 1881 FOR_EACH_EDGE (e, ei, bb->preds) | |
| 1882 gcc_assert (!bitmap_bit_p (tovisit, e->src->index) | |
| 1883 || (e->flags & EDGE_DFS_BACK)); | |
| 1884 #endif | |
| 1885 | |
| 1886 FOR_EACH_EDGE (e, ei, bb->preds) | |
| 1887 if (EDGE_INFO (e)->back_edge) | |
| 1888 { | |
| 1889 sreal_add (&cyclic_probability, &cyclic_probability, | |
| 1890 &EDGE_INFO (e)->back_edge_prob); | |
| 1891 } | |
| 1892 else if (!(e->flags & EDGE_DFS_BACK)) | |
| 1893 { | |
| 1894 sreal tmp; | |
| 1895 | |
| 1896 /* frequency += (e->probability | |
| 1897 * BLOCK_INFO (e->src)->frequency / | |
| 1898 REG_BR_PROB_BASE); */ | |
| 1899 | |
| 1900 sreal_init (&tmp, e->probability, 0); | |
| 1901 sreal_mul (&tmp, &tmp, &BLOCK_INFO (e->src)->frequency); | |
| 1902 sreal_mul (&tmp, &tmp, &real_inv_br_prob_base); | |
| 1903 sreal_add (&frequency, &frequency, &tmp); | |
| 1904 } | |
| 1905 | |
| 1906 if (sreal_compare (&cyclic_probability, &real_zero) == 0) | |
| 1907 { | |
| 1908 memcpy (&BLOCK_INFO (bb)->frequency, &frequency, | |
| 1909 sizeof (frequency)); | |
| 1910 } | |
| 1911 else | |
| 1912 { | |
| 1913 if (sreal_compare (&cyclic_probability, &real_almost_one) > 0) | |
| 1914 { | |
| 1915 memcpy (&cyclic_probability, &real_almost_one, | |
| 1916 sizeof (real_almost_one)); | |
| 1917 } | |
| 1918 | |
| 1919 /* BLOCK_INFO (bb)->frequency = frequency | |
| 1920 / (1 - cyclic_probability) */ | |
| 1921 | |
| 1922 sreal_sub (&cyclic_probability, &real_one, &cyclic_probability); | |
| 1923 sreal_div (&BLOCK_INFO (bb)->frequency, | |
| 1924 &frequency, &cyclic_probability); | |
| 1925 } | |
| 1926 } | |
| 1927 | |
| 1928 bitmap_clear_bit (tovisit, bb->index); | |
| 1929 | |
| 1930 e = find_edge (bb, head); | |
| 1931 if (e) | |
| 1932 { | |
| 1933 sreal tmp; | |
|
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1934 |
| 0 | 1935 /* EDGE_INFO (e)->back_edge_prob |
| 1936 = ((e->probability * BLOCK_INFO (bb)->frequency) | |
| 1937 / REG_BR_PROB_BASE); */ | |
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1938 |
| 0 | 1939 sreal_init (&tmp, e->probability, 0); |
| 1940 sreal_mul (&tmp, &tmp, &BLOCK_INFO (bb)->frequency); | |
| 1941 sreal_mul (&EDGE_INFO (e)->back_edge_prob, | |
| 1942 &tmp, &real_inv_br_prob_base); | |
| 1943 } | |
| 1944 | |
| 1945 /* Propagate to successor blocks. */ | |
| 1946 FOR_EACH_EDGE (e, ei, bb->succs) | |
| 1947 if (!(e->flags & EDGE_DFS_BACK) | |
| 1948 && BLOCK_INFO (e->dest)->npredecessors) | |
| 1949 { | |
| 1950 BLOCK_INFO (e->dest)->npredecessors--; | |
| 1951 if (!BLOCK_INFO (e->dest)->npredecessors) | |
| 1952 { | |
| 1953 if (!nextbb) | |
| 1954 nextbb = e->dest; | |
| 1955 else | |
| 1956 BLOCK_INFO (last)->next = e->dest; | |
|
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1957 |
| 0 | 1958 last = e->dest; |
| 1959 } | |
| 1960 } | |
| 1961 } | |
| 1962 } | |
| 1963 | |
| 1964 /* Estimate probabilities of loopback edges in loops at same nest level. */ | |
| 1965 | |
| 1966 static void | |
| 1967 estimate_loops_at_level (struct loop *first_loop) | |
| 1968 { | |
| 1969 struct loop *loop; | |
| 1970 | |
| 1971 for (loop = first_loop; loop; loop = loop->next) | |
| 1972 { | |
| 1973 edge e; | |
| 1974 basic_block *bbs; | |
| 1975 unsigned i; | |
| 1976 bitmap tovisit = BITMAP_ALLOC (NULL); | |
| 1977 | |
| 1978 estimate_loops_at_level (loop->inner); | |
| 1979 | |
| 1980 /* Find current loop back edge and mark it. */ | |
| 1981 e = loop_latch_edge (loop); | |
| 1982 EDGE_INFO (e)->back_edge = 1; | |
| 1983 | |
| 1984 bbs = get_loop_body (loop); | |
| 1985 for (i = 0; i < loop->num_nodes; i++) | |
| 1986 bitmap_set_bit (tovisit, bbs[i]->index); | |
| 1987 free (bbs); | |
| 1988 propagate_freq (loop->header, tovisit); | |
| 1989 BITMAP_FREE (tovisit); | |
| 1990 } | |
| 1991 } | |
| 1992 | |
| 1993 /* Propagates frequencies through structure of loops. */ | |
| 1994 | |
| 1995 static void | |
| 1996 estimate_loops (void) | |
| 1997 { | |
| 1998 bitmap tovisit = BITMAP_ALLOC (NULL); | |
| 1999 basic_block bb; | |
| 2000 | |
| 2001 /* Start by estimating the frequencies in the loops. */ | |
| 2002 if (number_of_loops () > 1) | |
| 2003 estimate_loops_at_level (current_loops->tree_root->inner); | |
| 2004 | |
| 2005 /* Now propagate the frequencies through all the blocks. */ | |
| 2006 FOR_ALL_BB (bb) | |
| 2007 { | |
| 2008 bitmap_set_bit (tovisit, bb->index); | |
| 2009 } | |
| 2010 propagate_freq (ENTRY_BLOCK_PTR, tovisit); | |
| 2011 BITMAP_FREE (tovisit); | |
| 2012 } | |
| 2013 | |
| 2014 /* Convert counts measured by profile driven feedback to frequencies. | |
| 2015 Return nonzero iff there was any nonzero execution count. */ | |
| 2016 | |
| 2017 int | |
| 2018 counts_to_freqs (void) | |
| 2019 { | |
| 2020 gcov_type count_max, true_count_max = 0; | |
| 2021 basic_block bb; | |
| 2022 | |
|
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2023 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb) |
| 0 | 2024 true_count_max = MAX (bb->count, true_count_max); |
| 2025 | |
| 2026 count_max = MAX (true_count_max, 1); | |
| 2027 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb) | |
| 2028 bb->frequency = (bb->count * BB_FREQ_MAX + count_max / 2) / count_max; | |
| 2029 | |
| 2030 return true_count_max; | |
| 2031 } | |
| 2032 | |
| 2033 /* Return true if function is likely to be expensive, so there is no point to | |
| 2034 optimize performance of prologue, epilogue or do inlining at the expense | |
| 2035 of code size growth. THRESHOLD is the limit of number of instructions | |
| 2036 function can execute at average to be still considered not expensive. */ | |
| 2037 | |
| 2038 bool | |
| 2039 expensive_function_p (int threshold) | |
| 2040 { | |
| 2041 unsigned int sum = 0; | |
| 2042 basic_block bb; | |
| 2043 unsigned int limit; | |
| 2044 | |
| 2045 /* We can not compute accurately for large thresholds due to scaled | |
| 2046 frequencies. */ | |
| 2047 gcc_assert (threshold <= BB_FREQ_MAX); | |
| 2048 | |
| 2049 /* Frequencies are out of range. This either means that function contains | |
| 2050 internal loop executing more than BB_FREQ_MAX times or profile feedback | |
| 2051 is available and function has not been executed at all. */ | |
| 2052 if (ENTRY_BLOCK_PTR->frequency == 0) | |
| 2053 return true; | |
| 2054 | |
| 2055 /* Maximally BB_FREQ_MAX^2 so overflow won't happen. */ | |
| 2056 limit = ENTRY_BLOCK_PTR->frequency * threshold; | |
| 2057 FOR_EACH_BB (bb) | |
| 2058 { | |
| 2059 rtx insn; | |
| 2060 | |
| 2061 for (insn = BB_HEAD (bb); insn != NEXT_INSN (BB_END (bb)); | |
| 2062 insn = NEXT_INSN (insn)) | |
| 2063 if (active_insn_p (insn)) | |
| 2064 { | |
| 2065 sum += bb->frequency; | |
| 2066 if (sum > limit) | |
| 2067 return true; | |
| 2068 } | |
| 2069 } | |
| 2070 | |
| 2071 return false; | |
| 2072 } | |
| 2073 | |
| 2074 /* Estimate basic blocks frequency by given branch probabilities. */ | |
| 2075 | |
| 2076 void | |
| 2077 estimate_bb_frequencies (void) | |
| 2078 { | |
| 2079 basic_block bb; | |
| 2080 sreal freq_max; | |
| 2081 | |
| 2082 if (profile_status != PROFILE_READ || !counts_to_freqs ()) | |
| 2083 { | |
| 2084 static int real_values_initialized = 0; | |
| 2085 | |
| 2086 if (!real_values_initialized) | |
| 2087 { | |
| 2088 real_values_initialized = 1; | |
| 2089 sreal_init (&real_zero, 0, 0); | |
| 2090 sreal_init (&real_one, 1, 0); | |
| 2091 sreal_init (&real_br_prob_base, REG_BR_PROB_BASE, 0); | |
| 2092 sreal_init (&real_bb_freq_max, BB_FREQ_MAX, 0); | |
| 2093 sreal_init (&real_one_half, 1, -1); | |
| 2094 sreal_div (&real_inv_br_prob_base, &real_one, &real_br_prob_base); | |
| 2095 sreal_sub (&real_almost_one, &real_one, &real_inv_br_prob_base); | |
| 2096 } | |
| 2097 | |
| 2098 mark_dfs_back_edges (); | |
| 2099 | |
| 2100 single_succ_edge (ENTRY_BLOCK_PTR)->probability = REG_BR_PROB_BASE; | |
| 2101 | |
| 2102 /* Set up block info for each basic block. */ | |
| 2103 alloc_aux_for_blocks (sizeof (struct block_info_def)); | |
| 2104 alloc_aux_for_edges (sizeof (struct edge_info_def)); | |
| 2105 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb) | |
| 2106 { | |
| 2107 edge e; | |
| 2108 edge_iterator ei; | |
| 2109 | |
| 2110 FOR_EACH_EDGE (e, ei, bb->succs) | |
| 2111 { | |
| 2112 sreal_init (&EDGE_INFO (e)->back_edge_prob, e->probability, 0); | |
| 2113 sreal_mul (&EDGE_INFO (e)->back_edge_prob, | |
| 2114 &EDGE_INFO (e)->back_edge_prob, | |
| 2115 &real_inv_br_prob_base); | |
| 2116 } | |
| 2117 } | |
| 2118 | |
| 2119 /* First compute probabilities locally for each loop from innermost | |
| 2120 to outermost to examine probabilities for back edges. */ | |
| 2121 estimate_loops (); | |
| 2122 | |
| 2123 memcpy (&freq_max, &real_zero, sizeof (real_zero)); | |
| 2124 FOR_EACH_BB (bb) | |
| 2125 if (sreal_compare (&freq_max, &BLOCK_INFO (bb)->frequency) < 0) | |
| 2126 memcpy (&freq_max, &BLOCK_INFO (bb)->frequency, sizeof (freq_max)); | |
| 2127 | |
| 2128 sreal_div (&freq_max, &real_bb_freq_max, &freq_max); | |
| 2129 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb) | |
| 2130 { | |
| 2131 sreal tmp; | |
| 2132 | |
| 2133 sreal_mul (&tmp, &BLOCK_INFO (bb)->frequency, &freq_max); | |
| 2134 sreal_add (&tmp, &tmp, &real_one_half); | |
| 2135 bb->frequency = sreal_to_int (&tmp); | |
| 2136 } | |
| 2137 | |
| 2138 free_aux_for_blocks (); | |
| 2139 free_aux_for_edges (); | |
| 2140 } | |
| 2141 compute_function_frequency (); | |
| 2142 if (flag_reorder_functions) | |
| 2143 choose_function_section (); | |
| 2144 } | |
| 2145 | |
| 2146 /* Decide whether function is hot, cold or unlikely executed. */ | |
|
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2147 void |
| 0 | 2148 compute_function_frequency (void) |
| 2149 { | |
| 2150 basic_block bb; | |
| 2151 | |
| 2152 if (!profile_info || !flag_branch_probabilities) | |
| 2153 { | |
| 2154 if (lookup_attribute ("cold", DECL_ATTRIBUTES (current_function_decl)) | |
| 2155 != NULL) | |
| 2156 cfun->function_frequency = FUNCTION_FREQUENCY_UNLIKELY_EXECUTED; | |
| 2157 else if (lookup_attribute ("hot", DECL_ATTRIBUTES (current_function_decl)) | |
| 2158 != NULL) | |
| 2159 cfun->function_frequency = FUNCTION_FREQUENCY_HOT; | |
| 2160 return; | |
| 2161 } | |
| 2162 cfun->function_frequency = FUNCTION_FREQUENCY_UNLIKELY_EXECUTED; | |
| 2163 FOR_EACH_BB (bb) | |
| 2164 { | |
| 2165 if (maybe_hot_bb_p (bb)) | |
| 2166 { | |
| 2167 cfun->function_frequency = FUNCTION_FREQUENCY_HOT; | |
| 2168 return; | |
| 2169 } | |
| 2170 if (!probably_never_executed_bb_p (bb)) | |
| 2171 cfun->function_frequency = FUNCTION_FREQUENCY_NORMAL; | |
| 2172 } | |
| 2173 } | |
| 2174 | |
| 2175 /* Choose appropriate section for the function. */ | |
| 2176 static void | |
| 2177 choose_function_section (void) | |
| 2178 { | |
| 2179 if (DECL_SECTION_NAME (current_function_decl) | |
| 2180 || !targetm.have_named_sections | |
| 2181 /* Theoretically we can split the gnu.linkonce text section too, | |
| 2182 but this requires more work as the frequency needs to match | |
| 2183 for all generated objects so we need to merge the frequency | |
| 2184 of all instances. For now just never set frequency for these. */ | |
| 2185 || DECL_ONE_ONLY (current_function_decl)) | |
| 2186 return; | |
| 2187 | |
| 2188 /* If we are doing the partitioning optimization, let the optimization | |
| 2189 choose the correct section into which to put things. */ | |
| 2190 | |
| 2191 if (flag_reorder_blocks_and_partition) | |
| 2192 return; | |
| 2193 | |
| 2194 if (cfun->function_frequency == FUNCTION_FREQUENCY_HOT) | |
| 2195 DECL_SECTION_NAME (current_function_decl) = | |
| 2196 build_string (strlen (HOT_TEXT_SECTION_NAME), HOT_TEXT_SECTION_NAME); | |
| 2197 if (cfun->function_frequency == FUNCTION_FREQUENCY_UNLIKELY_EXECUTED) | |
| 2198 DECL_SECTION_NAME (current_function_decl) = | |
| 2199 build_string (strlen (UNLIKELY_EXECUTED_TEXT_SECTION_NAME), | |
| 2200 UNLIKELY_EXECUTED_TEXT_SECTION_NAME); | |
| 2201 } | |
| 2202 | |
| 2203 static bool | |
| 2204 gate_estimate_probability (void) | |
| 2205 { | |
| 2206 return flag_guess_branch_prob; | |
| 2207 } | |
| 2208 | |
| 2209 /* Build PREDICT_EXPR. */ | |
| 2210 tree | |
| 2211 build_predict_expr (enum br_predictor predictor, enum prediction taken) | |
| 2212 { | |
| 2213 tree t = build1 (PREDICT_EXPR, void_type_node, | |
| 2214 build_int_cst (NULL, predictor)); | |
|
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2215 SET_PREDICT_EXPR_OUTCOME (t, taken); |
| 0 | 2216 return t; |
| 2217 } | |
| 2218 | |
| 2219 const char * | |
| 2220 predictor_name (enum br_predictor predictor) | |
| 2221 { | |
| 2222 return predictor_info[predictor].name; | |
| 2223 } | |
| 2224 | |
|
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2225 struct gimple_opt_pass pass_profile = |
| 0 | 2226 { |
| 2227 { | |
| 2228 GIMPLE_PASS, | |
| 2229 "profile", /* name */ | |
| 2230 gate_estimate_probability, /* gate */ | |
|
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2231 tree_estimate_probability_driver, /* execute */ |
| 0 | 2232 NULL, /* sub */ |
| 2233 NULL, /* next */ | |
| 2234 0, /* static_pass_number */ | |
| 2235 TV_BRANCH_PROB, /* tv_id */ | |
| 2236 PROP_cfg, /* properties_required */ | |
| 2237 0, /* properties_provided */ | |
| 2238 0, /* properties_destroyed */ | |
| 2239 0, /* todo_flags_start */ | |
| 2240 TODO_ggc_collect | TODO_verify_ssa /* todo_flags_finish */ | |
| 2241 } | |
| 2242 }; | |
| 2243 | |
|
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2244 struct gimple_opt_pass pass_strip_predict_hints = |
| 0 | 2245 { |
| 2246 { | |
| 2247 GIMPLE_PASS, | |
|
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2248 "*strip_predict_hints", /* name */ |
| 0 | 2249 NULL, /* gate */ |
| 2250 strip_predict_hints, /* execute */ | |
| 2251 NULL, /* sub */ | |
| 2252 NULL, /* next */ | |
| 2253 0, /* static_pass_number */ | |
| 2254 TV_BRANCH_PROB, /* tv_id */ | |
| 2255 PROP_cfg, /* properties_required */ | |
| 2256 0, /* properties_provided */ | |
| 2257 0, /* properties_destroyed */ | |
| 2258 0, /* todo_flags_start */ | |
| 2259 TODO_ggc_collect | TODO_verify_ssa /* todo_flags_finish */ | |
| 2260 } | |
| 2261 }; |