1 /* Natural loop functions 2 Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 3 2005, 2006, 2007, 2008, 2009 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 #ifndef GCC_CFGLOOP_H 22 #define GCC_CFGLOOP_H 23 24 #include "basic-block.h" 25 /* For rtx_code. */ 26 #include "rtl.h" 27 #include "vecprim.h" 28 #include "double-int.h" 29 30 /* Structure to hold decision about unrolling/peeling. */ 31 enum lpt_dec 32 { 33 LPT_NONE, 34 LPT_PEEL_COMPLETELY, 35 LPT_PEEL_SIMPLE, 36 LPT_UNROLL_CONSTANT, 37 LPT_UNROLL_RUNTIME, 38 LPT_UNROLL_STUPID 39 }; 40 41 struct lpt_decision GTY (()) 42 { 43 enum lpt_dec decision; 44 unsigned times; 45 }; 46 47 /* The structure describing a bound on number of iterations of a loop. */ 48 49 struct nb_iter_bound GTY ((chain_next ("%h.next"))) 50 { 51 /* The statement STMT is executed at most ... */ 52 gimple stmt; 53 54 /* ... BOUND + 1 times (BOUND must be an unsigned constant). 55 The + 1 is added for the following reasons: 56 57 a) 0 would otherwise be unused, while we would need to care more about 58 overflows (as MAX + 1 is sometimes produced as the estimate on number 59 of executions of STMT). 60 b) it is consistent with the result of number_of_iterations_exit. */ 61 double_int bound; 62 63 /* True if the statement will cause the loop to be leaved the (at most) 64 BOUND + 1-st time it is executed, that is, all the statements after it 65 are executed at most BOUND times. */ 66 bool is_exit; 67 68 /* The next bound in the list. */ 69 struct nb_iter_bound *next; 70 }; 71 72 /* Description of the loop exit. */ 73 74 struct loop_exit GTY (()) 75 { 76 /* The exit edge. */ 77 struct edge_def *e; 78 79 /* Previous and next exit in the list of the exits of the loop. */ 80 struct loop_exit *prev; 81 struct loop_exit *next; 82 83 /* Next element in the list of loops from that E exits. */ 84 struct loop_exit *next_e; 85 }; 86 87 typedef struct loop *loop_p; 88 DEF_VEC_P (loop_p); 89 DEF_VEC_ALLOC_P (loop_p, heap); 90 DEF_VEC_ALLOC_P (loop_p, gc); 91 92 /* An integer estimation of the number of iterations. Estimate_state 93 describes what is the state of the estimation. */ 94 enum loop_estimation 95 { 96 /* Estimate was not computed yet. */ 97 EST_NOT_COMPUTED, 98 /* Estimate is ready. */ 99 EST_AVAILABLE 100 }; 101 102 /* Structure to hold information for each natural loop. */ 103 struct loop GTY ((chain_next ("%h.next"))) 104 { 105 /* Index into loops array. */ 106 int num; 107 108 /* Number of loop insns. */ 109 unsigned ninsns; 110 111 /* Basic block of loop header. */ 112 struct basic_block_def *header; 113 114 /* Basic block of loop latch. */ 115 struct basic_block_def *latch; 116 117 /* For loop unrolling/peeling decision. */ 118 struct lpt_decision lpt_decision; 119 120 /* Average number of executed insns per iteration. */ 121 unsigned av_ninsns; 122 123 /* Number of blocks contained within the loop. */ 124 unsigned num_nodes; 125 126 /* Superloops of the loop, starting with the outermost loop. */ 127 VEC (loop_p, gc) *superloops; 128 129 /* The first inner (child) loop or NULL if innermost loop. */ 130 struct loop *inner; 131 132 /* Link to the next (sibling) loop. */ 133 struct loop *next; 134 135 /* Auxiliary info specific to a pass. */ 136 PTR GTY ((skip (""))) aux; 137 138 /* The number of times the latch of the loop is executed. 139 This is an INTEGER_CST or an expression containing symbolic 140 names. Don't access this field directly: 141 number_of_latch_executions computes and caches the computed 142 information in this field. */ 143 tree nb_iterations; 144 145 /* An integer guaranteed to bound the number of iterations of the loop 146 from above. */ 147 double_int nb_iterations_upper_bound; 148 149 /* An integer giving the expected number of iterations of the loop. */ 150 double_int nb_iterations_estimate; 151 152 bool any_upper_bound; 153 bool any_estimate; 154 155 /* An integer estimation of the number of iterations. Estimate_state 156 describes what is the state of the estimation. */ 157 enum loop_estimation estimate_state; 158 159 /* Upper bound on number of iterations of a loop. */ 160 struct nb_iter_bound *bounds; 161 162 /* Head of the cyclic list of the exits of the loop. */ 163 struct loop_exit *exits; 164 }; 165 166 /* Flags for state of loop structure. */ 167 enum 168 { 169 LOOPS_HAVE_PREHEADERS = 1, 170 LOOPS_HAVE_SIMPLE_LATCHES = 2, 171 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4, 172 LOOPS_HAVE_RECORDED_EXITS = 8, 173 LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16, 174 LOOP_CLOSED_SSA = 32, 175 LOOPS_NEED_FIXUP = 64, 176 LOOPS_HAVE_FALLTHRU_PREHEADERS = 128 177 }; 178 179 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \ 180 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS) 181 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES) 182 183 /* Structure to hold CFG information about natural loops within a function. */ 184 struct loops GTY (()) 185 { 186 /* State of loops. */ 187 int state; 188 189 /* Array of the loops. */ 190 VEC (loop_p, gc) *larray; 191 192 /* Maps edges to the list of their descriptions as loop exits. Edges 193 whose sources or destinations have loop_father == NULL (which may 194 happen during the cfg manipulations) should not appear in EXITS. */ 195 htab_t GTY((param_is (struct loop_exit))) exits; 196 197 /* Pointer to root of loop hierarchy tree. */ 198 struct loop *tree_root; 199 }; 200 201 /* Loop recognition. */ 202 extern int flow_loops_find (struct loops *); 203 extern void disambiguate_loops_with_multiple_latches (void); 204 extern void flow_loops_free (struct loops *); 205 extern void flow_loops_dump (FILE *, 206 void (*)(const struct loop *, FILE *, int), int); 207 extern void flow_loop_dump (const struct loop *, FILE *, 208 void (*)(const struct loop *, FILE *, int), int); 209 struct loop *alloc_loop (void); 210 extern void flow_loop_free (struct loop *); 211 int flow_loop_nodes_find (basic_block, struct loop *); 212 void fix_loop_structure (bitmap changed_bbs); 213 void mark_irreducible_loops (void); 214 void release_recorded_exits (void); 215 void record_loop_exits (void); 216 void rescan_loop_exit (edge, bool, bool); 217 218 /* Loop data structure manipulation/querying. */ 219 extern void flow_loop_tree_node_add (struct loop *, struct loop *); 220 extern void flow_loop_tree_node_remove (struct loop *); 221 extern void add_loop (struct loop *, struct loop *); 222 extern bool flow_loop_nested_p (const struct loop *, const struct loop *); 223 extern bool flow_bb_inside_loop_p (const struct loop *, const_basic_block); 224 extern struct loop * find_common_loop (struct loop *, struct loop *); 225 struct loop *superloop_at_depth (struct loop *, unsigned); 226 struct eni_weights_d; 227 extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *); 228 extern int num_loop_insns (const struct loop *); 229 extern int average_num_loop_insns (const struct loop *); 230 extern unsigned get_loop_level (const struct loop *); 231 extern bool loop_exit_edge_p (const struct loop *, const_edge); 232 extern bool is_loop_exit (struct loop *, basic_block); 233 extern void mark_loop_exit_edges (void); 234 235 /* Loops & cfg manipulation. */ 236 extern basic_block *get_loop_body (const struct loop *); 237 extern unsigned get_loop_body_with_size (const struct loop *, basic_block *, 238 unsigned); 239 extern basic_block *get_loop_body_in_dom_order (const struct loop *); 240 extern basic_block *get_loop_body_in_bfs_order (const struct loop *); 241 extern basic_block *get_loop_body_in_custom_order (const struct loop *, 242 int (*) (const void *, const void *)); 243 244 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *); 245 edge single_exit (const struct loop *); 246 extern unsigned num_loop_branches (const struct loop *); 247 248 extern edge loop_preheader_edge (const struct loop *); 249 extern edge loop_latch_edge (const struct loop *); 250 251 extern void add_bb_to_loop (basic_block, struct loop *); 252 extern void remove_bb_from_loops (basic_block); 253 254 extern void cancel_loop_tree (struct loop *); 255 extern void delete_loop (struct loop *); 256 257 enum 258 { 259 CP_SIMPLE_PREHEADERS = 1, 260 CP_FALLTHRU_PREHEADERS = 2 261 }; 262 263 basic_block create_preheader (struct loop *, int); 264 extern void create_preheaders (int); 265 extern void force_single_succ_latches (void); 266 267 extern void verify_loop_structure (void); 268 269 /* Loop analysis. */ 270 extern bool just_once_each_iteration_p (const struct loop *, const_basic_block); 271 gcov_type expected_loop_iterations_unbounded (const struct loop *); 272 extern unsigned expected_loop_iterations (const struct loop *); 273 extern rtx doloop_condition_get (rtx); 274 275 void estimate_numbers_of_iterations_loop (struct loop *); 276 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool); 277 bool estimated_loop_iterations (struct loop *, bool, double_int *); 278 279 /* Loop manipulation. */ 280 extern bool can_duplicate_loop_p (const struct loop *loop); 281 282 #define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in 283 duplicate_loop_to_header_edge. */ 284 #define DLTHE_RECORD_COPY_NUMBER 2 /* Record copy number in the aux 285 field of newly create BB. */ 286 #define DLTHE_FLAG_COMPLETTE_PEEL 4 /* Update frequencies expecting 287 a complete peeling. */ 288 289 extern edge create_empty_if_region_on_edge (edge, tree); 290 extern struct loop *create_empty_loop_on_edge (edge, tree, tree, tree, tree, 291 tree *, struct loop *); 292 extern struct loop * duplicate_loop (struct loop *, struct loop *); 293 extern bool duplicate_loop_to_header_edge (struct loop *, edge, 294 unsigned, sbitmap, edge, 295 VEC (edge, heap) **, int); 296 extern struct loop *loopify (edge, edge, 297 basic_block, edge, edge, bool, 298 unsigned, unsigned); 299 struct loop * loop_version (struct loop *, void *, 300 basic_block *, unsigned, unsigned, unsigned, bool); 301 extern bool remove_path (edge); 302 void scale_loop_frequencies (struct loop *, int, int); 303 304 /* Induction variable analysis. */ 305 306 /* The description of induction variable. The things are a bit complicated 307 due to need to handle subregs and extends. The value of the object described 308 by it can be obtained as follows (all computations are done in extend_mode): 309 310 Value in i-th iteration is 311 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)). 312 313 If first_special is true, the value in the first iteration is 314 delta + mult * base 315 316 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is 317 subreg_{mode} (base + i * step) 318 319 The get_iv_value function can be used to obtain these expressions. 320 321 ??? Add a third mode field that would specify the mode in that inner 322 computation is done, which would enable it to be different from the 323 outer one? */ 324 325 struct rtx_iv 326 { 327 /* Its base and step (mode of base and step is supposed to be extend_mode, 328 see the description above). */ 329 rtx base, step; 330 331 /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN). */ 332 enum rtx_code extend; 333 334 /* Operations applied in the extended mode. */ 335 rtx delta, mult; 336 337 /* The mode it is extended to. */ 338 enum machine_mode extend_mode; 339 340 /* The mode the variable iterates in. */ 341 enum machine_mode mode; 342 343 /* Whether the first iteration needs to be handled specially. */ 344 unsigned first_special : 1; 345 }; 346 347 /* The description of an exit from the loop and of the number of iterations 348 till we take the exit. */ 349 350 struct niter_desc 351 { 352 /* The edge out of the loop. */ 353 edge out_edge; 354 355 /* The other edge leading from the condition. */ 356 edge in_edge; 357 358 /* True if we are able to say anything about number of iterations of the 359 loop. */ 360 bool simple_p; 361 362 /* True if the loop iterates the constant number of times. */ 363 bool const_iter; 364 365 /* Number of iterations if constant. */ 366 unsigned HOST_WIDEST_INT niter; 367 368 /* Upper bound on the number of iterations. */ 369 unsigned HOST_WIDEST_INT niter_max; 370 371 /* Assumptions under that the rest of the information is valid. */ 372 rtx assumptions; 373 374 /* Assumptions under that the loop ends before reaching the latch, 375 even if value of niter_expr says otherwise. */ 376 rtx noloop_assumptions; 377 378 /* Condition under that the loop is infinite. */ 379 rtx infinite; 380 381 /* Whether the comparison is signed. */ 382 bool signed_p; 383 384 /* The mode in that niter_expr should be computed. */ 385 enum machine_mode mode; 386 387 /* The number of iterations of the loop. */ 388 rtx niter_expr; 389 }; 390 391 extern void iv_analysis_loop_init (struct loop *); 392 extern bool iv_analyze (rtx, rtx, struct rtx_iv *); 393 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *); 394 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *); 395 extern rtx get_iv_value (struct rtx_iv *, rtx); 396 extern bool biv_p (rtx, rtx); 397 extern void find_simple_exit (struct loop *, struct niter_desc *); 398 extern void iv_analysis_done (void); 399 400 extern struct niter_desc *get_simple_loop_desc (struct loop *loop); 401 extern void free_simple_loop_desc (struct loop *loop); 402 403 static inline struct niter_desc * 404 simple_loop_desc (struct loop *loop) 405 { 406 return (struct niter_desc *) loop->aux; 407 } 408 409 /* Accessors for the loop structures. */ 410 411 /* Returns the loop with index NUM from current_loops. */ 412 413 static inline struct loop * 414 get_loop (unsigned num) 415 { 416 return VEC_index (loop_p, current_loops->larray, num); 417 } 418 419 /* Returns the number of superloops of LOOP. */ 420 421 static inline unsigned 422 loop_depth (const struct loop *loop) 423 { 424 return VEC_length (loop_p, loop->superloops); 425 } 426 427 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost 428 loop. */ 429 430 static inline struct loop * 431 loop_outer (const struct loop *loop) 432 { 433 unsigned n = VEC_length (loop_p, loop->superloops); 434 435 if (n == 0) 436 return NULL; 437 438 return VEC_index (loop_p, loop->superloops, n - 1); 439 } 440 441 /* Returns the list of loops in current_loops. */ 442 443 static inline VEC (loop_p, gc) * 444 get_loops (void) 445 { 446 if (!current_loops) 447 return NULL; 448 449 return current_loops->larray; 450 } 451 452 /* Returns the number of loops in current_loops (including the removed 453 ones and the fake loop that forms the root of the loop tree). */ 454 455 static inline unsigned 456 number_of_loops (void) 457 { 458 if (!current_loops) 459 return 0; 460 461 return VEC_length (loop_p, current_loops->larray); 462 } 463 464 /* Returns true if state of the loops satisfies all properties 465 described by FLAGS. */ 466 467 static inline bool 468 loops_state_satisfies_p (unsigned flags) 469 { 470 return (current_loops->state & flags) == flags; 471 } 472 473 /* Sets FLAGS to the loops state. */ 474 475 static inline void 476 loops_state_set (unsigned flags) 477 { 478 current_loops->state |= flags; 479 } 480 481 /* Clears FLAGS from the loops state. */ 482 483 static inline void 484 loops_state_clear (unsigned flags) 485 { 486 if (!current_loops) 487 return; 488 current_loops->state &= ~flags; 489 } 490 491 /* Loop iterators. */ 492 493 /* Flags for loop iteration. */ 494 495 enum li_flags 496 { 497 LI_INCLUDE_ROOT = 1, /* Include the fake root of the loop tree. */ 498 LI_FROM_INNERMOST = 2, /* Iterate over the loops in the reverse order, 499 starting from innermost ones. */ 500 LI_ONLY_INNERMOST = 4 /* Iterate only over innermost loops. */ 501 }; 502 503 /* The iterator for loops. */ 504 505 typedef struct 506 { 507 /* The list of loops to visit. */ 508 VEC(int,heap) *to_visit; 509 510 /* The index of the actual loop. */ 511 unsigned idx; 512 } loop_iterator; 513 514 static inline void 515 fel_next (loop_iterator *li, loop_p *loop) 516 { 517 int anum; 518 519 while (VEC_iterate (int, li->to_visit, li->idx, anum)) 520 { 521 li->idx++; 522 *loop = get_loop (anum); 523 if (*loop) 524 return; 525 } 526 527 VEC_free (int, heap, li->to_visit); 528 *loop = NULL; 529 } 530 531 static inline void 532 fel_init (loop_iterator *li, loop_p *loop, unsigned flags) 533 { 534 struct loop *aloop; 535 unsigned i; 536 int mn; 537 538 li->idx = 0; 539 if (!current_loops) 540 { 541 li->to_visit = NULL; 542 *loop = NULL; 543 return; 544 } 545 546 li->to_visit = VEC_alloc (int, heap, number_of_loops ()); 547 mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1; 548 549 if (flags & LI_ONLY_INNERMOST) 550 { 551 for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++) 552 if (aloop != NULL 553 && aloop->inner == NULL 554 && aloop->num >= mn) 555 VEC_quick_push (int, li->to_visit, aloop->num); 556 } 557 else if (flags & LI_FROM_INNERMOST) 558 { 559 /* Push the loops to LI->TO_VISIT in postorder. */ 560 for (aloop = current_loops->tree_root; 561 aloop->inner != NULL; 562 aloop = aloop->inner) 563 continue; 564 565 while (1) 566 { 567 if (aloop->num >= mn) 568 VEC_quick_push (int, li->to_visit, aloop->num); 569 570 if (aloop->next) 571 { 572 for (aloop = aloop->next; 573 aloop->inner != NULL; 574 aloop = aloop->inner) 575 continue; 576 } 577 else if (!loop_outer (aloop)) 578 break; 579 else 580 aloop = loop_outer (aloop); 581 } 582 } 583 else 584 { 585 /* Push the loops to LI->TO_VISIT in preorder. */ 586 aloop = current_loops->tree_root; 587 while (1) 588 { 589 if (aloop->num >= mn) 590 VEC_quick_push (int, li->to_visit, aloop->num); 591 592 if (aloop->inner != NULL) 593 aloop = aloop->inner; 594 else 595 { 596 while (aloop != NULL && aloop->next == NULL) 597 aloop = loop_outer (aloop); 598 if (aloop == NULL) 599 break; 600 aloop = aloop->next; 601 } 602 } 603 } 604 605 fel_next (li, loop); 606 } 607 608 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \ 609 for (fel_init (&(LI), &(LOOP), FLAGS); \ 610 (LOOP); \ 611 fel_next (&(LI), &(LOOP))) 612 613 #define FOR_EACH_LOOP_BREAK(LI) \ 614 { \ 615 VEC_free (int, heap, (LI)->to_visit); \ 616 break; \ 617 } 618 619 /* The properties of the target. */ 620 621 extern unsigned target_avail_regs; 622 extern unsigned target_res_regs; 623 extern unsigned target_reg_cost [2]; 624 extern unsigned target_spill_cost [2]; 625 626 /* Register pressure estimation for induction variable optimizations & loop 627 invariant motion. */ 628 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool); 629 extern void init_set_costs (void); 630 631 /* Loop optimizer initialization. */ 632 extern void loop_optimizer_init (unsigned); 633 extern void loop_optimizer_finalize (void); 634 635 /* Optimization passes. */ 636 extern void unswitch_loops (void); 637 638 enum 639 { 640 UAP_PEEL = 1, /* Enables loop peeling. */ 641 UAP_UNROLL = 2, /* Enables unrolling of loops if it seems profitable. */ 642 UAP_UNROLL_ALL = 4 /* Enables unrolling of all loops. */ 643 }; 644 645 extern void unroll_and_peel_loops (int); 646 extern void doloop_optimize_loops (void); 647 extern void move_loop_invariants (void); 648 649 #endif /* GCC_CFGLOOP_H */ 650
