Mercurial > hg > CbC > CbC_gcc
annotate gcc/tree-ssa-loop-ch.c @ 136:4627f235cf2a
fix c-next example
| author | Shinji KONO <kono@ie.u-ryukyu.ac.jp> |
|---|---|
| date | Thu, 08 Nov 2018 14:11:56 +0900 |
| parents | 84e7813d76e9 |
| children | 1830386684a0 |
| rev | line source |
|---|---|
| 0 | 1 /* Loop header copying on trees. |
| 131 | 2 Copyright (C) 2004-2018 Free Software Foundation, Inc. |
|
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3 |
| 0 | 4 This file is part of GCC. |
|
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5 |
| 0 | 6 GCC is free software; you can redistribute it and/or modify it |
| 7 under the terms of the GNU General Public License as published by the | |
| 8 Free Software Foundation; either version 3, or (at your option) any | |
| 9 later version. | |
|
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10 |
| 0 | 11 GCC is distributed in the hope that it will be useful, but WITHOUT |
| 12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 14 for more details. | |
|
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15 |
| 0 | 16 You should have received a copy of the GNU General Public License |
| 17 along with GCC; see the file COPYING3. If not see | |
| 18 <http://www.gnu.org/licenses/>. */ | |
| 19 | |
| 20 #include "config.h" | |
| 21 #include "system.h" | |
| 22 #include "coretypes.h" | |
| 111 | 23 #include "backend.h" |
| 0 | 24 #include "tree.h" |
| 111 | 25 #include "gimple.h" |
| 26 #include "cfghooks.h" | |
| 0 | 27 #include "tree-pass.h" |
| 111 | 28 #include "gimple-ssa.h" |
| 29 #include "gimple-iterator.h" | |
| 30 #include "tree-cfg.h" | |
| 31 #include "tree-into-ssa.h" | |
| 0 | 32 #include "cfgloop.h" |
| 33 #include "tree-inline.h" | |
| 111 | 34 #include "tree-ssa-scopedtables.h" |
| 35 #include "tree-ssa-threadedge.h" | |
| 36 #include "params.h" | |
| 0 | 37 |
| 38 /* Duplicates headers of loops if they are small enough, so that the statements | |
| 39 in the loop body are always executed when the loop is entered. This | |
| 40 increases effectiveness of code motion optimizations, and reduces the need | |
| 41 for loop preconditioning. */ | |
| 42 | |
| 43 /* Check whether we should duplicate HEADER of LOOP. At most *LIMIT | |
| 44 instructions should be duplicated, limit is decreased by the actual | |
| 45 amount. */ | |
| 46 | |
| 47 static bool | |
| 48 should_duplicate_loop_header_p (basic_block header, struct loop *loop, | |
| 49 int *limit) | |
| 50 { | |
| 51 gimple_stmt_iterator bsi; | |
| 111 | 52 gimple *last; |
| 0 | 53 |
| 111 | 54 gcc_assert (!header->aux); |
| 0 | 55 |
| 56 /* Loop header copying usually increases size of the code. This used not to | |
| 57 be true, since quite often it is possible to verify that the condition is | |
| 58 satisfied in the first iteration and therefore to eliminate it. Jump | |
| 59 threading handles these cases now. */ | |
| 131 | 60 if (optimize_loop_for_size_p (loop) |
| 61 && !loop->force_vectorize) | |
| 111 | 62 { |
| 63 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 64 fprintf (dump_file, | |
| 65 " Not duplicating bb %i: optimizing for size.\n", | |
| 66 header->index); | |
| 67 return false; | |
| 68 } | |
| 0 | 69 |
| 70 gcc_assert (EDGE_COUNT (header->succs) > 0); | |
| 71 if (single_succ_p (header)) | |
| 111 | 72 { |
| 73 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 74 fprintf (dump_file, | |
| 75 " Not duplicating bb %i: it is single succ.\n", | |
| 76 header->index); | |
| 77 return false; | |
| 78 } | |
| 79 | |
| 0 | 80 if (flow_bb_inside_loop_p (loop, EDGE_SUCC (header, 0)->dest) |
| 81 && flow_bb_inside_loop_p (loop, EDGE_SUCC (header, 1)->dest)) | |
| 111 | 82 { |
| 83 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 84 fprintf (dump_file, | |
| 85 " Not duplicating bb %i: both sucessors are in loop.\n", | |
| 86 loop->num); | |
| 87 return false; | |
| 88 } | |
| 0 | 89 |
| 90 /* If this is not the original loop header, we want it to have just | |
| 91 one predecessor in order to match the && pattern. */ | |
| 92 if (header != loop->header && !single_pred_p (header)) | |
| 111 | 93 { |
| 94 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 95 fprintf (dump_file, | |
| 96 " Not duplicating bb %i: it has mutiple predecestors.\n", | |
| 97 header->index); | |
| 98 return false; | |
| 99 } | |
| 0 | 100 |
| 101 last = last_stmt (header); | |
| 102 if (gimple_code (last) != GIMPLE_COND) | |
| 111 | 103 { |
| 104 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 105 fprintf (dump_file, | |
| 106 " Not duplicating bb %i: it does not end by conditional.\n", | |
| 107 header->index); | |
| 108 return false; | |
| 109 } | |
| 0 | 110 |
| 111 | 111 /* Count number of instructions and punt on calls. */ |
| 0 | 112 for (bsi = gsi_start_bb (header); !gsi_end_p (bsi); gsi_next (&bsi)) |
| 113 { | |
| 114 last = gsi_stmt (bsi); | |
| 115 | |
| 116 if (gimple_code (last) == GIMPLE_LABEL) | |
| 117 continue; | |
| 118 | |
|
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119 if (is_gimple_debug (last)) |
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120 continue; |
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121 |
| 111 | 122 if (gimple_code (last) == GIMPLE_CALL |
| 123 && (!gimple_inexpensive_call_p (as_a <gcall *> (last)) | |
| 124 /* IFN_LOOP_DIST_ALIAS means that inner loop is distributed | |
| 125 at current loop's header. Don't copy in this case. */ | |
| 126 || gimple_call_internal_p (last, IFN_LOOP_DIST_ALIAS))) | |
| 127 { | |
| 128 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 129 fprintf (dump_file, | |
| 130 " Not duplicating bb %i: it contains call.\n", | |
| 131 header->index); | |
| 132 return false; | |
| 133 } | |
| 0 | 134 |
| 135 *limit -= estimate_num_insns (last, &eni_size_weights); | |
| 136 if (*limit < 0) | |
| 111 | 137 { |
| 138 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 139 fprintf (dump_file, | |
| 140 " Not duplicating bb %i contains too many insns.\n", | |
| 141 header->index); | |
| 142 return false; | |
| 143 } | |
| 0 | 144 } |
| 111 | 145 if (dump_file && (dump_flags & TDF_DETAILS)) |
| 146 fprintf (dump_file, " Will duplicate bb %i\n", header->index); | |
| 0 | 147 return true; |
| 148 } | |
| 149 | |
| 150 /* Checks whether LOOP is a do-while style loop. */ | |
| 151 | |
| 152 static bool | |
| 153 do_while_loop_p (struct loop *loop) | |
| 154 { | |
| 111 | 155 gimple *stmt = last_stmt (loop->latch); |
| 0 | 156 |
| 157 /* If the latch of the loop is not empty, it is not a do-while loop. */ | |
| 158 if (stmt | |
| 159 && gimple_code (stmt) != GIMPLE_LABEL) | |
| 111 | 160 { |
| 161 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 162 fprintf (dump_file, | |
| 163 "Loop %i is not do-while loop: latch is not empty.\n", | |
| 164 loop->num); | |
| 165 return false; | |
| 166 } | |
| 0 | 167 |
| 131 | 168 /* If the latch does not have a single predecessor, it is not a |
| 169 do-while loop. */ | |
| 170 if (!single_pred_p (loop->latch)) | |
| 111 | 171 { |
| 172 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 173 fprintf (dump_file, | |
| 131 | 174 "Loop %i is not do-while loop: latch has multiple " |
| 175 "predecessors.\n", loop->num); | |
| 111 | 176 return false; |
| 177 } | |
| 131 | 178 |
| 179 /* If the latch predecessor doesn't exit the loop, it is not a | |
| 180 do-while loop. */ | |
| 181 if (!loop_exits_from_bb_p (loop, single_pred (loop->latch))) | |
| 182 { | |
| 183 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 184 fprintf (dump_file, | |
| 185 "Loop %i is not do-while loop: latch predecessor " | |
| 186 "does not exit loop.\n", loop->num); | |
| 187 return false; | |
| 188 } | |
| 189 | |
| 111 | 190 if (dump_file && (dump_flags & TDF_DETAILS)) |
| 191 fprintf (dump_file, "Loop %i is do-while loop\n", loop->num); | |
| 0 | 192 |
| 193 return true; | |
| 194 } | |
| 195 | |
| 111 | 196 namespace { |
| 197 | |
| 198 /* Common superclass for both header-copying phases. */ | |
| 199 class ch_base : public gimple_opt_pass | |
| 200 { | |
| 201 protected: | |
| 202 ch_base (pass_data data, gcc::context *ctxt) | |
| 203 : gimple_opt_pass (data, ctxt) | |
| 204 {} | |
| 205 | |
| 206 /* Copies headers of all loops in FUN for which process_loop_p is true. */ | |
| 207 unsigned int copy_headers (function *fun); | |
| 208 | |
| 209 /* Return true to copy headers of LOOP or false to skip. */ | |
| 210 virtual bool process_loop_p (struct loop *loop) = 0; | |
| 211 }; | |
| 212 | |
| 213 const pass_data pass_data_ch = | |
| 214 { | |
| 215 GIMPLE_PASS, /* type */ | |
| 216 "ch", /* name */ | |
| 217 OPTGROUP_LOOP, /* optinfo_flags */ | |
| 218 TV_TREE_CH, /* tv_id */ | |
| 219 ( PROP_cfg | PROP_ssa ), /* properties_required */ | |
| 220 0, /* properties_provided */ | |
| 221 0, /* properties_destroyed */ | |
| 222 0, /* todo_flags_start */ | |
| 223 0, /* todo_flags_finish */ | |
| 224 }; | |
| 225 | |
| 226 class pass_ch : public ch_base | |
| 227 { | |
| 228 public: | |
| 229 pass_ch (gcc::context *ctxt) | |
| 230 : ch_base (pass_data_ch, ctxt) | |
| 231 {} | |
| 232 | |
| 233 /* opt_pass methods: */ | |
| 234 virtual bool gate (function *) { return flag_tree_ch != 0; } | |
| 235 | |
| 236 /* Initialize and finalize loop structures, copying headers inbetween. */ | |
| 237 virtual unsigned int execute (function *); | |
| 238 | |
| 239 opt_pass * clone () { return new pass_ch (m_ctxt); } | |
| 240 | |
| 241 protected: | |
| 242 /* ch_base method: */ | |
| 243 virtual bool process_loop_p (struct loop *loop); | |
| 244 }; // class pass_ch | |
| 245 | |
| 246 const pass_data pass_data_ch_vect = | |
| 247 { | |
| 248 GIMPLE_PASS, /* type */ | |
| 249 "ch_vect", /* name */ | |
| 250 OPTGROUP_LOOP, /* optinfo_flags */ | |
| 251 TV_TREE_CH, /* tv_id */ | |
| 252 ( PROP_cfg | PROP_ssa ), /* properties_required */ | |
| 253 0, /* properties_provided */ | |
| 254 0, /* properties_destroyed */ | |
| 255 0, /* todo_flags_start */ | |
| 256 0, /* todo_flags_finish */ | |
| 257 }; | |
| 258 | |
| 259 /* This is a more aggressive version of the same pass, designed to run just | |
| 260 before if-conversion and vectorization, to put more loops into the form | |
| 261 required for those phases. */ | |
| 262 class pass_ch_vect : public ch_base | |
| 263 { | |
| 264 public: | |
| 265 pass_ch_vect (gcc::context *ctxt) | |
| 266 : ch_base (pass_data_ch_vect, ctxt) | |
| 267 {} | |
| 268 | |
| 269 /* opt_pass methods: */ | |
| 270 virtual bool gate (function *fun) | |
| 271 { | |
| 272 return flag_tree_ch != 0 | |
| 273 && (flag_tree_loop_vectorize != 0 || fun->has_force_vectorize_loops); | |
| 274 } | |
| 275 | |
| 276 /* Just copy headers, no initialization/finalization of loop structures. */ | |
| 277 virtual unsigned int execute (function *); | |
| 278 | |
| 279 protected: | |
| 280 /* ch_base method: */ | |
| 281 virtual bool process_loop_p (struct loop *loop); | |
| 282 }; // class pass_ch_vect | |
| 283 | |
| 0 | 284 /* For all loops, copy the condition at the end of the loop body in front |
| 285 of the loop. This is beneficial since it increases efficiency of | |
| 286 code motion optimizations. It also saves one jump on entry to the loop. */ | |
| 287 | |
| 111 | 288 unsigned int |
| 289 ch_base::copy_headers (function *fun) | |
| 0 | 290 { |
| 291 struct loop *loop; | |
| 292 basic_block header; | |
| 293 edge exit, entry; | |
| 294 basic_block *bbs, *copied_bbs; | |
| 295 unsigned n_bbs; | |
| 296 unsigned bbs_size; | |
| 111 | 297 bool changed = false; |
| 0 | 298 |
| 111 | 299 if (number_of_loops (fun) <= 1) |
| 0 | 300 return 0; |
| 301 | |
| 111 | 302 bbs = XNEWVEC (basic_block, n_basic_blocks_for_fn (fun)); |
| 303 copied_bbs = XNEWVEC (basic_block, n_basic_blocks_for_fn (fun)); | |
| 304 bbs_size = n_basic_blocks_for_fn (fun); | |
| 0 | 305 |
| 111 | 306 FOR_EACH_LOOP (loop, 0) |
| 0 | 307 { |
| 111 | 308 int initial_limit = PARAM_VALUE (PARAM_MAX_LOOP_HEADER_INSNS); |
| 309 int remaining_limit = initial_limit; | |
| 310 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 311 fprintf (dump_file, | |
| 312 "Analyzing loop %i\n", loop->num); | |
| 0 | 313 |
| 314 header = loop->header; | |
| 315 | |
| 316 /* If the loop is already a do-while style one (either because it was | |
| 317 written as such, or because jump threading transformed it into one), | |
| 318 we might be in fact peeling the first iteration of the loop. This | |
| 131 | 319 in general is not a good idea. Also avoid touching infinite loops. */ |
| 320 if (!loop_has_exit_edges (loop) | |
| 321 || !process_loop_p (loop)) | |
| 0 | 322 continue; |
| 323 | |
| 324 /* Iterate the header copying up to limit; this takes care of the cases | |
| 325 like while (a && b) {...}, where we want to have both of the conditions | |
| 326 copied. TODO -- handle while (a || b) - like cases, by not requiring | |
| 327 the header to have just a single successor and copying up to | |
| 328 postdominator. */ | |
| 329 | |
| 330 exit = NULL; | |
| 331 n_bbs = 0; | |
| 111 | 332 while (should_duplicate_loop_header_p (header, loop, &remaining_limit)) |
| 0 | 333 { |
| 334 /* Find a successor of header that is inside a loop; i.e. the new | |
| 335 header after the condition is copied. */ | |
| 336 if (flow_bb_inside_loop_p (loop, EDGE_SUCC (header, 0)->dest)) | |
| 337 exit = EDGE_SUCC (header, 0); | |
| 338 else | |
| 339 exit = EDGE_SUCC (header, 1); | |
| 340 bbs[n_bbs++] = header; | |
| 341 gcc_assert (bbs_size > n_bbs); | |
| 342 header = exit->dest; | |
| 131 | 343 /* Make sure to stop copying after we copied the first exit test. |
| 344 Without further heuristics we do not want to rotate the loop | |
| 345 any further. */ | |
| 346 if (loop_exits_from_bb_p (loop, exit->src)) | |
| 347 break; | |
| 0 | 348 } |
| 349 | |
| 350 if (!exit) | |
| 351 continue; | |
| 352 | |
| 353 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 354 fprintf (dump_file, | |
| 111 | 355 "Duplicating header of the loop %d up to edge %d->%d," |
| 356 " %i insns.\n", | |
| 357 loop->num, exit->src->index, exit->dest->index, | |
| 358 initial_limit - remaining_limit); | |
| 0 | 359 |
| 360 /* Ensure that the header will have just the latch as a predecessor | |
| 361 inside the loop. */ | |
| 362 if (!single_pred_p (exit->dest)) | |
| 363 exit = single_pred_edge (split_edge (exit)); | |
| 364 | |
| 365 entry = loop_preheader_edge (loop); | |
| 366 | |
| 111 | 367 propagate_threaded_block_debug_into (exit->dest, entry->dest); |
| 368 if (!gimple_duplicate_sese_region (entry, exit, bbs, n_bbs, copied_bbs, | |
| 369 true)) | |
| 0 | 370 { |
| 371 fprintf (dump_file, "Duplication failed.\n"); | |
| 372 continue; | |
| 373 } | |
| 374 | |
| 375 /* If the loop has the form "for (i = j; i < j + 10; i++)" then | |
| 376 this copying can introduce a case where we rely on undefined | |
| 377 signed overflow to eliminate the preheader condition, because | |
| 378 we assume that "j < j + 10" is true. We don't want to warn | |
| 379 about that case for -Wstrict-overflow, because in general we | |
| 380 don't warn about overflow involving loops. Prevent the | |
| 381 warning by setting the no_warning flag in the condition. */ | |
| 382 if (warn_strict_overflow > 0) | |
| 383 { | |
| 384 unsigned int i; | |
| 385 | |
| 386 for (i = 0; i < n_bbs; ++i) | |
| 387 { | |
| 388 gimple_stmt_iterator bsi; | |
| 389 | |
| 390 for (bsi = gsi_start_bb (copied_bbs[i]); | |
| 391 !gsi_end_p (bsi); | |
| 392 gsi_next (&bsi)) | |
| 393 { | |
| 111 | 394 gimple *stmt = gsi_stmt (bsi); |
| 0 | 395 if (gimple_code (stmt) == GIMPLE_COND) |
| 396 gimple_set_no_warning (stmt, true); | |
| 397 else if (is_gimple_assign (stmt)) | |
| 398 { | |
| 399 enum tree_code rhs_code = gimple_assign_rhs_code (stmt); | |
| 400 if (TREE_CODE_CLASS (rhs_code) == tcc_comparison) | |
| 401 gimple_set_no_warning (stmt, true); | |
| 402 } | |
| 403 } | |
| 404 } | |
| 405 } | |
| 406 | |
| 407 /* Ensure that the latch and the preheader is simple (we know that they | |
| 408 are not now, since there was the loop exit condition. */ | |
| 409 split_edge (loop_preheader_edge (loop)); | |
| 410 split_edge (loop_latch_edge (loop)); | |
| 111 | 411 |
| 131 | 412 if (dump_file && (dump_flags & TDF_DETAILS)) |
| 413 { | |
| 414 if (do_while_loop_p (loop)) | |
| 415 fprintf (dump_file, "Loop %d is now do-while loop.\n", loop->num); | |
| 416 else | |
| 417 fprintf (dump_file, "Loop %d is still not do-while loop.\n", | |
| 418 loop->num); | |
| 419 } | |
| 420 | |
| 111 | 421 changed = true; |
| 0 | 422 } |
| 423 | |
| 111 | 424 if (changed) |
| 425 update_ssa (TODO_update_ssa); | |
| 0 | 426 free (bbs); |
| 427 free (copied_bbs); | |
| 428 | |
| 111 | 429 return changed ? TODO_cleanup_cfg : 0; |
| 430 } | |
| 431 | |
| 432 /* Initialize the loop structures we need, and finalize after. */ | |
| 433 | |
| 434 unsigned int | |
| 435 pass_ch::execute (function *fun) | |
| 436 { | |
| 437 loop_optimizer_init (LOOPS_HAVE_PREHEADERS | |
| 131 | 438 | LOOPS_HAVE_SIMPLE_LATCHES |
| 439 | LOOPS_HAVE_RECORDED_EXITS); | |
| 111 | 440 |
| 441 unsigned int res = copy_headers (fun); | |
| 442 | |
| 0 | 443 loop_optimizer_finalize (); |
| 111 | 444 return res; |
| 0 | 445 } |
| 446 | |
| 111 | 447 /* Assume an earlier phase has already initialized all the loop structures that |
| 448 we need here (and perhaps others too), and that these will be finalized by | |
| 449 a later phase. */ | |
| 450 | |
| 451 unsigned int | |
| 452 pass_ch_vect::execute (function *fun) | |
| 0 | 453 { |
| 111 | 454 return copy_headers (fun); |
| 455 } | |
| 456 | |
| 457 /* Apply header copying according to a very simple test of do-while shape. */ | |
| 458 | |
| 459 bool | |
| 460 pass_ch::process_loop_p (struct loop *loop) | |
| 461 { | |
| 462 return !do_while_loop_p (loop); | |
| 0 | 463 } |
| 464 | |
| 111 | 465 /* Apply header-copying to loops where we might enable vectorization. */ |
| 466 | |
| 467 bool | |
| 468 pass_ch_vect::process_loop_p (struct loop *loop) | |
| 0 | 469 { |
| 111 | 470 if (!flag_tree_loop_vectorize && !loop->force_vectorize) |
| 471 return false; | |
| 472 | |
| 473 if (loop->dont_vectorize) | |
| 474 return false; | |
| 475 | |
| 476 if (!do_while_loop_p (loop)) | |
| 477 return true; | |
| 478 | |
| 479 /* The vectorizer won't handle anything with multiple exits, so skip. */ | |
| 480 edge exit = single_exit (loop); | |
| 481 if (!exit) | |
| 482 return false; | |
| 483 | |
| 484 /* Copy headers iff there looks to be code in the loop after the exit block, | |
| 485 i.e. the exit block has an edge to another block (besides the latch, | |
| 486 which should be empty). */ | |
| 487 edge_iterator ei; | |
| 488 edge e; | |
| 489 FOR_EACH_EDGE (e, ei, exit->src->succs) | |
| 490 if (!loop_exit_edge_p (loop, e) | |
| 491 && e->dest != loop->header | |
| 492 && e->dest != loop->latch) | |
| 493 return true; | |
| 494 | |
| 495 return false; | |
| 496 } | |
| 497 | |
| 498 } // anon namespace | |
| 499 | |
| 500 gimple_opt_pass * | |
| 501 make_pass_ch_vect (gcc::context *ctxt) | |
| 502 { | |
| 503 return new pass_ch_vect (ctxt); | |
| 504 } | |
| 505 | |
| 506 gimple_opt_pass * | |
| 507 make_pass_ch (gcc::context *ctxt) | |
| 508 { | |
| 509 return new pass_ch (ctxt); | |
| 510 } |