Mercurial > hg > CbC > CbC_gcc
annotate gcc/tree-ssa-sink.c @ 118:fd00160c1b76
ifdef TARGET_64BIT
| author | mir3636 |
|---|---|
| date | Tue, 27 Feb 2018 15:01:35 +0900 |
| parents | 04ced10e8804 |
| children | 84e7813d76e9 |
| rev | line source |
|---|---|
| 0 | 1 /* Code sinking for trees |
| 111 | 2 Copyright (C) 2001-2017 Free Software Foundation, Inc. |
| 0 | 3 Contributed by Daniel Berlin <dan@dberlin.org> |
| 4 | |
| 5 This file is part of GCC. | |
| 6 | |
| 7 GCC is free software; you can redistribute it and/or modify | |
| 8 it under the terms of the GNU General Public License as published by | |
| 9 the Free Software Foundation; either version 3, or (at your option) | |
| 10 any later version. | |
| 11 | |
| 12 GCC is distributed in the hope that it will be useful, | |
| 13 but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 15 GNU General Public License 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 #include "config.h" | |
| 22 #include "system.h" | |
| 23 #include "coretypes.h" | |
| 111 | 24 #include "backend.h" |
| 0 | 25 #include "tree.h" |
| 26 #include "gimple.h" | |
| 111 | 27 #include "cfghooks.h" |
| 0 | 28 #include "tree-pass.h" |
| 111 | 29 #include "ssa.h" |
| 30 #include "gimple-pretty-print.h" | |
| 31 #include "fold-const.h" | |
| 32 #include "stor-layout.h" | |
| 33 #include "cfganal.h" | |
| 34 #include "gimple-iterator.h" | |
| 35 #include "tree-cfg.h" | |
| 0 | 36 #include "cfgloop.h" |
| 111 | 37 #include "params.h" |
| 0 | 38 |
| 39 /* TODO: | |
| 40 1. Sinking store only using scalar promotion (IE without moving the RHS): | |
| 41 | |
| 42 *q = p; | |
| 43 p = p + 1; | |
| 44 if (something) | |
| 45 *q = <not p>; | |
| 46 else | |
| 47 y = *q; | |
| 48 | |
|
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49 |
| 0 | 50 should become |
| 51 sinktemp = p; | |
| 52 p = p + 1; | |
| 53 if (something) | |
| 54 *q = <not p>; | |
| 55 else | |
| 56 { | |
| 57 *q = sinktemp; | |
| 58 y = *q | |
| 59 } | |
| 60 Store copy propagation will take care of the store elimination above. | |
|
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61 |
| 0 | 62 |
| 63 2. Sinking using Partial Dead Code Elimination. */ | |
| 64 | |
| 65 | |
| 66 static struct | |
|
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67 { |
| 0 | 68 /* The number of statements sunk down the flowgraph by code sinking. */ |
| 69 int sunk; | |
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70 |
| 0 | 71 } sink_stats; |
| 72 | |
| 73 | |
| 74 /* Given a PHI, and one of its arguments (DEF), find the edge for | |
| 75 that argument and return it. If the argument occurs twice in the PHI node, | |
| 76 we return NULL. */ | |
| 77 | |
| 78 static basic_block | |
| 111 | 79 find_bb_for_arg (gphi *phi, tree def) |
| 0 | 80 { |
| 81 size_t i; | |
| 82 bool foundone = false; | |
| 83 basic_block result = NULL; | |
| 84 for (i = 0; i < gimple_phi_num_args (phi); i++) | |
| 85 if (PHI_ARG_DEF (phi, i) == def) | |
| 86 { | |
| 87 if (foundone) | |
| 88 return NULL; | |
| 89 foundone = true; | |
| 90 result = gimple_phi_arg_edge (phi, i)->src; | |
| 91 } | |
| 92 return result; | |
| 93 } | |
| 94 | |
| 95 /* When the first immediate use is in a statement, then return true if all | |
| 96 immediate uses in IMM are in the same statement. | |
| 97 We could also do the case where the first immediate use is in a phi node, | |
| 98 and all the other uses are in phis in the same basic block, but this | |
| 99 requires some expensive checking later (you have to make sure no def/vdef | |
| 100 in the statement occurs for multiple edges in the various phi nodes it's | |
| 101 used in, so that you only have one place you can sink it to. */ | |
| 102 | |
| 103 static bool | |
| 111 | 104 all_immediate_uses_same_place (def_operand_p def_p) |
| 0 | 105 { |
| 111 | 106 tree var = DEF_FROM_PTR (def_p); |
| 0 | 107 imm_use_iterator imm_iter; |
| 108 use_operand_p use_p; | |
| 109 | |
| 111 | 110 gimple *firstuse = NULL; |
| 111 FOR_EACH_IMM_USE_FAST (use_p, imm_iter, var) | |
| 0 | 112 { |
| 111 | 113 if (is_gimple_debug (USE_STMT (use_p))) |
| 114 continue; | |
| 115 if (firstuse == NULL) | |
| 116 firstuse = USE_STMT (use_p); | |
| 117 else | |
| 118 if (firstuse != USE_STMT (use_p)) | |
| 119 return false; | |
| 0 | 120 } |
| 121 | |
| 122 return true; | |
| 123 } | |
| 124 | |
| 125 /* Find the nearest common dominator of all of the immediate uses in IMM. */ | |
| 126 | |
| 127 static basic_block | |
| 111 | 128 nearest_common_dominator_of_uses (def_operand_p def_p, bool *debug_stmts) |
|
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129 { |
| 111 | 130 tree var = DEF_FROM_PTR (def_p); |
| 131 auto_bitmap blocks; | |
| 0 | 132 basic_block commondom; |
| 133 unsigned int j; | |
| 134 bitmap_iterator bi; | |
| 135 imm_use_iterator imm_iter; | |
| 136 use_operand_p use_p; | |
| 137 | |
| 111 | 138 FOR_EACH_IMM_USE_FAST (use_p, imm_iter, var) |
| 0 | 139 { |
| 111 | 140 gimple *usestmt = USE_STMT (use_p); |
| 141 basic_block useblock; | |
| 0 | 142 |
| 111 | 143 if (gphi *phi = dyn_cast <gphi *> (usestmt)) |
| 144 { | |
| 145 int idx = PHI_ARG_INDEX_FROM_USE (use_p); | |
| 0 | 146 |
| 111 | 147 useblock = gimple_phi_arg_edge (phi, idx)->src; |
| 148 } | |
| 149 else if (is_gimple_debug (usestmt)) | |
| 150 { | |
| 151 *debug_stmts = true; | |
| 152 continue; | |
| 153 } | |
| 154 else | |
| 155 { | |
| 156 useblock = gimple_bb (usestmt); | |
| 157 } | |
| 0 | 158 |
| 111 | 159 /* Short circuit. Nothing dominates the entry block. */ |
| 160 if (useblock == ENTRY_BLOCK_PTR_FOR_FN (cfun)) | |
| 161 return NULL; | |
| 162 | |
| 163 bitmap_set_bit (blocks, useblock->index); | |
| 0 | 164 } |
| 111 | 165 commondom = BASIC_BLOCK_FOR_FN (cfun, bitmap_first_set_bit (blocks)); |
| 0 | 166 EXECUTE_IF_SET_IN_BITMAP (blocks, 0, j, bi) |
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167 commondom = nearest_common_dominator (CDI_DOMINATORS, commondom, |
| 111 | 168 BASIC_BLOCK_FOR_FN (cfun, j)); |
| 0 | 169 return commondom; |
| 170 } | |
| 171 | |
| 111 | 172 /* Given EARLY_BB and LATE_BB, two blocks in a path through the dominator |
| 173 tree, return the best basic block between them (inclusive) to place | |
| 174 statements. | |
| 175 | |
| 176 We want the most control dependent block in the shallowest loop nest. | |
| 177 | |
| 178 If the resulting block is in a shallower loop nest, then use it. Else | |
| 179 only use the resulting block if it has significantly lower execution | |
| 180 frequency than EARLY_BB to avoid gratutious statement movement. We | |
| 181 consider statements with VOPS more desirable to move. | |
| 182 | |
| 183 This pass would obviously benefit from PDO as it utilizes block | |
| 184 frequencies. It would also benefit from recomputing frequencies | |
| 185 if profile data is not available since frequencies often get out | |
| 186 of sync with reality. */ | |
| 187 | |
| 188 static basic_block | |
| 189 select_best_block (basic_block early_bb, | |
| 190 basic_block late_bb, | |
| 191 gimple *stmt) | |
| 192 { | |
| 193 basic_block best_bb = late_bb; | |
| 194 basic_block temp_bb = late_bb; | |
| 195 int threshold; | |
| 196 | |
| 197 while (temp_bb != early_bb) | |
| 198 { | |
| 199 /* If we've moved into a lower loop nest, then that becomes | |
| 200 our best block. */ | |
| 201 if (bb_loop_depth (temp_bb) < bb_loop_depth (best_bb)) | |
| 202 best_bb = temp_bb; | |
| 203 | |
| 204 /* Walk up the dominator tree, hopefully we'll find a shallower | |
| 205 loop nest. */ | |
| 206 temp_bb = get_immediate_dominator (CDI_DOMINATORS, temp_bb); | |
| 207 } | |
| 208 | |
| 209 /* If we found a shallower loop nest, then we always consider that | |
| 210 a win. This will always give us the most control dependent block | |
| 211 within that loop nest. */ | |
| 212 if (bb_loop_depth (best_bb) < bb_loop_depth (early_bb)) | |
| 213 return best_bb; | |
| 214 | |
| 215 /* Get the sinking threshold. If the statement to be moved has memory | |
| 216 operands, then increase the threshold by 7% as those are even more | |
| 217 profitable to avoid, clamping at 100%. */ | |
| 218 threshold = PARAM_VALUE (PARAM_SINK_FREQUENCY_THRESHOLD); | |
| 219 if (gimple_vuse (stmt) || gimple_vdef (stmt)) | |
| 220 { | |
| 221 threshold += 7; | |
| 222 if (threshold > 100) | |
| 223 threshold = 100; | |
| 224 } | |
| 225 | |
| 226 /* If BEST_BB is at the same nesting level, then require it to have | |
| 227 significantly lower execution frequency to avoid gratutious movement. */ | |
| 228 if (bb_loop_depth (best_bb) == bb_loop_depth (early_bb) | |
| 229 && best_bb->frequency < (early_bb->frequency * threshold / 100.0)) | |
| 230 return best_bb; | |
| 231 | |
| 232 /* No better block found, so return EARLY_BB, which happens to be the | |
| 233 statement's original block. */ | |
| 234 return early_bb; | |
| 235 } | |
| 236 | |
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237 /* Given a statement (STMT) and the basic block it is currently in (FROMBB), |
| 0 | 238 determine the location to sink the statement to, if any. |
| 239 Returns true if there is such location; in that case, TOGSI points to the | |
| 240 statement before that STMT should be moved. */ | |
| 241 | |
| 242 static bool | |
| 111 | 243 statement_sink_location (gimple *stmt, basic_block frombb, |
| 244 gimple_stmt_iterator *togsi, bool *zero_uses_p) | |
| 0 | 245 { |
| 111 | 246 gimple *use; |
| 0 | 247 use_operand_p one_use = NULL_USE_OPERAND_P; |
| 248 basic_block sinkbb; | |
| 249 use_operand_p use_p; | |
| 250 def_operand_p def_p; | |
| 251 ssa_op_iter iter; | |
| 252 imm_use_iterator imm_iter; | |
| 253 | |
| 111 | 254 *zero_uses_p = false; |
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255 |
| 111 | 256 /* We only can sink assignments and non-looping const/pure calls. */ |
| 257 int cf; | |
| 258 if (!is_gimple_assign (stmt) | |
| 259 && (!is_gimple_call (stmt) | |
| 260 || !((cf = gimple_call_flags (stmt)) & (ECF_CONST|ECF_PURE)) | |
| 261 || (cf & ECF_LOOPING_CONST_OR_PURE))) | |
| 0 | 262 return false; |
| 263 | |
| 111 | 264 /* We only can sink stmts with a single definition. */ |
| 265 def_p = single_ssa_def_operand (stmt, SSA_OP_ALL_DEFS); | |
| 266 if (def_p == NULL_DEF_OPERAND_P) | |
| 0 | 267 return false; |
| 268 | |
| 269 /* There are a few classes of things we can't or don't move, some because we | |
| 270 don't have code to handle it, some because it's not profitable and some | |
|
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271 because it's not legal. |
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272 |
| 0 | 273 We can't sink things that may be global stores, at least not without |
| 274 calculating a lot more information, because we may cause it to no longer | |
| 275 be seen by an external routine that needs it depending on where it gets | |
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276 moved to. |
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277 |
| 0 | 278 We can't sink statements that end basic blocks without splitting the |
| 279 incoming edge for the sink location to place it there. | |
| 280 | |
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281 We can't sink statements that have volatile operands. |
| 0 | 282 |
| 283 We don't want to sink dead code, so anything with 0 immediate uses is not | |
| 284 sunk. | |
| 285 | |
| 286 Don't sink BLKmode assignments if current function has any local explicit | |
| 287 register variables, as BLKmode assignments may involve memcpy or memset | |
| 288 calls or, on some targets, inline expansion thereof that sometimes need | |
| 289 to use specific hard registers. | |
| 290 | |
| 291 */ | |
| 292 if (stmt_ends_bb_p (stmt) | |
| 293 || gimple_has_side_effects (stmt) | |
| 294 || (cfun->has_local_explicit_reg_vars | |
| 111 | 295 && TYPE_MODE (TREE_TYPE (gimple_get_lhs (stmt))) == BLKmode)) |
| 0 | 296 return false; |
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297 |
| 111 | 298 /* Return if there are no immediate uses of this stmt. */ |
| 299 if (has_zero_uses (DEF_FROM_PTR (def_p))) | |
| 0 | 300 { |
| 111 | 301 *zero_uses_p = true; |
| 302 return false; | |
| 0 | 303 } |
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304 |
| 111 | 305 if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (DEF_FROM_PTR (def_p))) |
| 306 return false; | |
| 307 | |
| 0 | 308 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES) |
| 309 { | |
| 310 tree use = USE_FROM_PTR (use_p); | |
| 311 if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (use)) | |
| 312 return false; | |
| 313 } | |
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314 |
| 111 | 315 use = NULL; |
| 316 | |
| 317 /* If stmt is a store the one and only use needs to be the VOP | |
| 318 merging PHI node. */ | |
| 319 if (virtual_operand_p (DEF_FROM_PTR (def_p))) | |
| 320 { | |
| 321 FOR_EACH_IMM_USE_FAST (use_p, imm_iter, DEF_FROM_PTR (def_p)) | |
| 322 { | |
| 323 gimple *use_stmt = USE_STMT (use_p); | |
| 324 | |
| 325 /* A killing definition is not a use. */ | |
| 326 if ((gimple_has_lhs (use_stmt) | |
| 327 && operand_equal_p (gimple_get_lhs (stmt), | |
| 328 gimple_get_lhs (use_stmt), 0)) | |
| 329 || stmt_kills_ref_p (use_stmt, gimple_get_lhs (stmt))) | |
| 330 { | |
| 331 /* If use_stmt is or might be a nop assignment then USE_STMT | |
| 332 acts as a use as well as definition. */ | |
| 333 if (stmt != use_stmt | |
| 334 && ref_maybe_used_by_stmt_p (use_stmt, | |
| 335 gimple_get_lhs (stmt))) | |
| 336 return false; | |
| 337 continue; | |
| 338 } | |
| 339 | |
| 340 if (gimple_code (use_stmt) != GIMPLE_PHI) | |
| 341 return false; | |
| 342 | |
| 343 if (use | |
| 344 && use != use_stmt) | |
| 345 return false; | |
| 346 | |
| 347 use = use_stmt; | |
| 348 } | |
| 349 if (!use) | |
| 350 return false; | |
| 351 } | |
| 0 | 352 /* If all the immediate uses are not in the same place, find the nearest |
| 353 common dominator of all the immediate uses. For PHI nodes, we have to | |
| 354 find the nearest common dominator of all of the predecessor blocks, since | |
| 355 that is where insertion would have to take place. */ | |
| 111 | 356 else if (gimple_vuse (stmt) |
| 357 || !all_immediate_uses_same_place (def_p)) | |
| 0 | 358 { |
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359 bool debug_stmts = false; |
| 111 | 360 basic_block commondom = nearest_common_dominator_of_uses (def_p, |
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361 &debug_stmts); |
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362 |
| 0 | 363 if (commondom == frombb) |
| 364 return false; | |
| 365 | |
| 111 | 366 /* If this is a load then do not sink past any stores. |
| 367 ??? This is overly simple but cheap. We basically look | |
| 368 for an existing load with the same VUSE in the path to one | |
| 369 of the sink candidate blocks and we adjust commondom to the | |
| 370 nearest to commondom. */ | |
| 371 if (gimple_vuse (stmt)) | |
| 372 { | |
| 373 /* Do not sink loads from hard registers. */ | |
| 374 if (gimple_assign_single_p (stmt) | |
| 375 && TREE_CODE (gimple_assign_rhs1 (stmt)) == VAR_DECL | |
| 376 && DECL_HARD_REGISTER (gimple_assign_rhs1 (stmt))) | |
| 377 return false; | |
| 378 | |
| 379 imm_use_iterator imm_iter; | |
| 380 use_operand_p use_p; | |
| 381 basic_block found = NULL; | |
| 382 FOR_EACH_IMM_USE_FAST (use_p, imm_iter, gimple_vuse (stmt)) | |
| 383 { | |
| 384 gimple *use_stmt = USE_STMT (use_p); | |
| 385 basic_block bb = gimple_bb (use_stmt); | |
| 386 /* For PHI nodes the block we know sth about | |
| 387 is the incoming block with the use. */ | |
| 388 if (gimple_code (use_stmt) == GIMPLE_PHI) | |
| 389 bb = EDGE_PRED (bb, PHI_ARG_INDEX_FROM_USE (use_p))->src; | |
| 390 /* Any dominator of commondom would be ok with | |
| 391 adjusting commondom to that block. */ | |
| 392 bb = nearest_common_dominator (CDI_DOMINATORS, bb, commondom); | |
| 393 if (!found) | |
| 394 found = bb; | |
| 395 else if (dominated_by_p (CDI_DOMINATORS, bb, found)) | |
| 396 found = bb; | |
| 397 /* If we can't improve, stop. */ | |
| 398 if (found == commondom) | |
| 399 break; | |
| 400 } | |
| 401 commondom = found; | |
| 402 if (commondom == frombb) | |
| 403 return false; | |
| 404 } | |
| 405 | |
| 0 | 406 /* Our common dominator has to be dominated by frombb in order to be a |
| 407 trivially safe place to put this statement, since it has multiple | |
|
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408 uses. */ |
| 0 | 409 if (!dominated_by_p (CDI_DOMINATORS, commondom, frombb)) |
| 410 return false; | |
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411 |
| 111 | 412 commondom = select_best_block (frombb, commondom, stmt); |
| 0 | 413 |
| 111 | 414 if (commondom == frombb) |
| 415 return false; | |
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416 |
| 0 | 417 *togsi = gsi_after_labels (commondom); |
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418 |
| 0 | 419 return true; |
| 420 } | |
| 111 | 421 else |
| 0 | 422 { |
| 111 | 423 FOR_EACH_IMM_USE_FAST (one_use, imm_iter, DEF_FROM_PTR (def_p)) |
| 424 { | |
| 425 if (is_gimple_debug (USE_STMT (one_use))) | |
| 426 continue; | |
| 427 break; | |
| 428 } | |
| 429 use = USE_STMT (one_use); | |
| 0 | 430 |
| 111 | 431 if (gimple_code (use) != GIMPLE_PHI) |
| 432 { | |
| 433 sinkbb = gimple_bb (use); | |
| 434 sinkbb = select_best_block (frombb, gimple_bb (use), stmt); | |
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435 |
| 111 | 436 if (sinkbb == frombb) |
| 437 return false; | |
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438 |
| 111 | 439 *togsi = gsi_for_stmt (use); |
| 440 | |
| 441 return true; | |
| 442 } | |
| 0 | 443 } |
| 444 | |
| 111 | 445 sinkbb = find_bb_for_arg (as_a <gphi *> (use), DEF_FROM_PTR (def_p)); |
| 0 | 446 |
| 111 | 447 /* This can happen if there are multiple uses in a PHI. */ |
| 0 | 448 if (!sinkbb) |
| 449 return false; | |
| 111 | 450 |
| 451 sinkbb = select_best_block (frombb, sinkbb, stmt); | |
| 452 if (!sinkbb || sinkbb == frombb) | |
| 0 | 453 return false; |
| 454 | |
|
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455 /* If the latch block is empty, don't make it non-empty by sinking |
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456 something into it. */ |
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457 if (sinkbb == frombb->loop_father->latch |
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458 && empty_block_p (sinkbb)) |
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459 return false; |
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460 |
| 0 | 461 *togsi = gsi_after_labels (sinkbb); |
| 462 | |
| 463 return true; | |
| 464 } | |
| 465 | |
| 466 /* Perform code sinking on BB */ | |
| 467 | |
| 468 static void | |
| 469 sink_code_in_bb (basic_block bb) | |
| 470 { | |
| 471 basic_block son; | |
| 472 gimple_stmt_iterator gsi; | |
| 473 edge_iterator ei; | |
| 474 edge e; | |
| 475 bool last = true; | |
|
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476 |
| 0 | 477 /* If this block doesn't dominate anything, there can't be any place to sink |
| 478 the statements to. */ | |
| 479 if (first_dom_son (CDI_DOMINATORS, bb) == NULL) | |
| 480 goto earlyout; | |
| 481 | |
| 482 /* We can't move things across abnormal edges, so don't try. */ | |
| 483 FOR_EACH_EDGE (e, ei, bb->succs) | |
| 484 if (e->flags & EDGE_ABNORMAL) | |
| 485 goto earlyout; | |
| 486 | |
| 487 for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi);) | |
| 488 { | |
| 111 | 489 gimple *stmt = gsi_stmt (gsi); |
| 0 | 490 gimple_stmt_iterator togsi; |
| 111 | 491 bool zero_uses_p; |
| 0 | 492 |
| 111 | 493 if (!statement_sink_location (stmt, bb, &togsi, &zero_uses_p)) |
| 0 | 494 { |
| 111 | 495 gimple_stmt_iterator saved = gsi; |
| 0 | 496 if (!gsi_end_p (gsi)) |
| 497 gsi_prev (&gsi); | |
| 111 | 498 /* If we face a dead stmt remove it as it possibly blocks |
| 499 sinking of uses. */ | |
| 500 if (zero_uses_p | |
| 501 && ! gimple_vdef (stmt)) | |
| 502 { | |
| 503 gsi_remove (&saved, true); | |
| 504 release_defs (stmt); | |
| 505 } | |
| 506 else | |
| 507 last = false; | |
| 0 | 508 continue; |
|
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509 } |
| 0 | 510 if (dump_file) |
| 511 { | |
| 512 fprintf (dump_file, "Sinking "); | |
| 513 print_gimple_stmt (dump_file, stmt, 0, TDF_VOPS); | |
| 514 fprintf (dump_file, " from bb %d to bb %d\n", | |
| 515 bb->index, (gsi_bb (togsi))->index); | |
| 516 } | |
|
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517 |
| 111 | 518 /* Update virtual operands of statements in the path we |
| 519 do not sink to. */ | |
| 520 if (gimple_vdef (stmt)) | |
| 521 { | |
| 522 imm_use_iterator iter; | |
| 523 use_operand_p use_p; | |
| 524 gimple *vuse_stmt; | |
| 525 | |
| 526 FOR_EACH_IMM_USE_STMT (vuse_stmt, iter, gimple_vdef (stmt)) | |
| 527 if (gimple_code (vuse_stmt) != GIMPLE_PHI) | |
| 528 FOR_EACH_IMM_USE_ON_STMT (use_p, iter) | |
| 529 SET_USE (use_p, gimple_vuse (stmt)); | |
| 530 } | |
| 531 | |
| 0 | 532 /* If this is the end of the basic block, we need to insert at the end |
| 533 of the basic block. */ | |
| 534 if (gsi_end_p (togsi)) | |
| 535 gsi_move_to_bb_end (&gsi, gsi_bb (togsi)); | |
| 536 else | |
| 537 gsi_move_before (&gsi, &togsi); | |
| 538 | |
| 539 sink_stats.sunk++; | |
| 540 | |
| 541 /* If we've just removed the last statement of the BB, the | |
| 542 gsi_end_p() test below would fail, but gsi_prev() would have | |
| 543 succeeded, and we want it to succeed. So we keep track of | |
| 544 whether we're at the last statement and pick up the new last | |
| 545 statement. */ | |
| 546 if (last) | |
| 547 { | |
| 548 gsi = gsi_last_bb (bb); | |
| 549 continue; | |
| 550 } | |
| 551 | |
| 552 last = false; | |
| 553 if (!gsi_end_p (gsi)) | |
| 554 gsi_prev (&gsi); | |
|
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555 |
| 0 | 556 } |
| 557 earlyout: | |
| 558 for (son = first_dom_son (CDI_POST_DOMINATORS, bb); | |
| 559 son; | |
| 560 son = next_dom_son (CDI_POST_DOMINATORS, son)) | |
| 561 { | |
| 562 sink_code_in_bb (son); | |
| 563 } | |
|
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564 } |
| 0 | 565 |
| 566 /* Perform code sinking. | |
| 567 This moves code down the flowgraph when we know it would be | |
| 568 profitable to do so, or it wouldn't increase the number of | |
| 569 executions of the statement. | |
| 570 | |
| 571 IE given | |
|
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572 |
| 0 | 573 a_1 = b + c; |
| 574 if (<something>) | |
| 575 { | |
| 576 } | |
| 577 else | |
| 578 { | |
| 579 foo (&b, &c); | |
| 580 a_5 = b + c; | |
| 581 } | |
| 582 a_6 = PHI (a_5, a_1); | |
| 583 USE a_6. | |
| 584 | |
| 585 we'll transform this into: | |
| 586 | |
| 587 if (<something>) | |
| 588 { | |
| 589 a_1 = b + c; | |
| 590 } | |
| 591 else | |
| 592 { | |
| 593 foo (&b, &c); | |
| 594 a_5 = b + c; | |
| 595 } | |
| 596 a_6 = PHI (a_5, a_1); | |
| 597 USE a_6. | |
| 598 | |
| 599 Note that this reduces the number of computations of a = b + c to 1 | |
| 600 when we take the else edge, instead of 2. | |
| 601 */ | |
| 111 | 602 namespace { |
| 603 | |
| 604 const pass_data pass_data_sink_code = | |
| 605 { | |
| 606 GIMPLE_PASS, /* type */ | |
| 607 "sink", /* name */ | |
| 608 OPTGROUP_NONE, /* optinfo_flags */ | |
| 609 TV_TREE_SINK, /* tv_id */ | |
| 610 /* PROP_no_crit_edges is ensured by running split_critical_edges in | |
| 611 pass_data_sink_code::execute (). */ | |
| 612 ( PROP_cfg | PROP_ssa ), /* properties_required */ | |
| 613 0, /* properties_provided */ | |
| 614 0, /* properties_destroyed */ | |
| 615 0, /* todo_flags_start */ | |
| 616 TODO_update_ssa, /* todo_flags_finish */ | |
| 617 }; | |
| 618 | |
| 619 class pass_sink_code : public gimple_opt_pass | |
| 620 { | |
| 621 public: | |
| 622 pass_sink_code (gcc::context *ctxt) | |
| 623 : gimple_opt_pass (pass_data_sink_code, ctxt) | |
| 624 {} | |
| 625 | |
| 626 /* opt_pass methods: */ | |
| 627 virtual bool gate (function *) { return flag_tree_sink != 0; } | |
| 628 virtual unsigned int execute (function *); | |
| 629 | |
| 630 }; // class pass_sink_code | |
| 631 | |
| 632 unsigned int | |
| 633 pass_sink_code::execute (function *fun) | |
| 0 | 634 { |
| 635 loop_optimizer_init (LOOPS_NORMAL); | |
| 111 | 636 split_critical_edges (); |
| 0 | 637 connect_infinite_loops_to_exit (); |
| 638 memset (&sink_stats, 0, sizeof (sink_stats)); | |
| 639 calculate_dominance_info (CDI_DOMINATORS); | |
| 640 calculate_dominance_info (CDI_POST_DOMINATORS); | |
| 111 | 641 sink_code_in_bb (EXIT_BLOCK_PTR_FOR_FN (fun)); |
| 642 statistics_counter_event (fun, "Sunk statements", sink_stats.sunk); | |
| 0 | 643 free_dominance_info (CDI_POST_DOMINATORS); |
| 644 remove_fake_exit_edges (); | |
| 645 loop_optimizer_finalize (); | |
| 646 | |
| 647 return 0; | |
| 648 } | |
| 649 | |
| 111 | 650 } // anon namespace |
| 0 | 651 |
| 111 | 652 gimple_opt_pass * |
| 653 make_pass_sink_code (gcc::context *ctxt) | |
| 0 | 654 { |
| 111 | 655 return new pass_sink_code (ctxt); |
| 656 } |