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 5This file is part of GCC. 6 7GCC is free software; you can redistribute it and/or modify it under 8the terms of the GNU General Public License as published by the Free 9Software Foundation; either version 3, or (at your option) any later 10version. 11 12GCC is distributed in the hope that it will be useful, but WITHOUT ANY 13WARRANTY; without even the implied warranty of MERCHANTABILITY or 14FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15for more details. 16 17You should have received a copy of the GNU General Public License 18along 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. */ 31enum 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 41struct GTY (()) lpt_decision { 42 enum lpt_dec decision; 43 unsigned times; 44}; 45 46/* The structure describing a bound on number of iterations of a loop. */ 47 48struct GTY ((chain_next ("%h.next"))) nb_iter_bound { 49 /* The statement STMT is executed at most ... */ 50 gimple stmt; 51 52 /* ... BOUND + 1 times (BOUND must be an unsigned constant). 53 The + 1 is added for the following reasons: 54 55 a) 0 would otherwise be unused, while we would need to care more about 56 overflows (as MAX + 1 is sometimes produced as the estimate on number 57 of executions of STMT). 58 b) it is consistent with the result of number_of_iterations_exit. */ 59 double_int bound; 60 61 /* True if the statement will cause the loop to be leaved the (at most) 62 BOUND + 1-st time it is executed, that is, all the statements after it 63 are executed at most BOUND times. */ 64 bool is_exit; 65 66 /* The next bound in the list. */ 67 struct nb_iter_bound *next; 68}; 69 70/* Description of the loop exit. */ 71 72struct GTY (()) loop_exit { 73 /* The exit edge. */ 74 struct edge_def *e; 75 76 /* Previous and next exit in the list of the exits of the loop. */ 77 struct loop_exit *prev; 78 struct loop_exit *next; 79 80 /* Next element in the list of loops from that E exits. */ 81 struct loop_exit *next_e; 82}; 83 84typedef struct loop *loop_p; 85DEF_VEC_P (loop_p); 86DEF_VEC_ALLOC_P (loop_p, heap); 87DEF_VEC_ALLOC_P (loop_p, gc); 88 89/* An integer estimation of the number of iterations. Estimate_state 90 describes what is the state of the estimation. */ 91enum loop_estimation 92{ 93 /* Estimate was not computed yet. */ 94 EST_NOT_COMPUTED, 95 /* Estimate is ready. */ 96 EST_AVAILABLE 97}; 98 99/* Structure to hold information for each natural loop. */ 100struct GTY ((chain_next ("%h.next"))) loop { 101 /* Index into loops array. */ 102 int num; 103 104 /* Number of loop insns. */ 105 unsigned ninsns; 106 107 /* Basic block of loop header. */ 108 struct basic_block_def *header; 109 110 /* Basic block of loop latch. */ 111 struct basic_block_def *latch; 112 113 /* For loop unrolling/peeling decision. */ 114 struct lpt_decision lpt_decision; 115 116 /* Average number of executed insns per iteration. */ 117 unsigned av_ninsns; 118 119 /* Number of blocks contained within the loop. */ 120 unsigned num_nodes; 121 122 /* Superloops of the loop, starting with the outermost loop. */ 123 VEC (loop_p, gc) *superloops; 124 125 /* The first inner (child) loop or NULL if innermost loop. */ 126 struct loop *inner; 127 128 /* Link to the next (sibling) loop. */ 129 struct loop *next; 130 131 /* Auxiliary info specific to a pass. */ 132 PTR GTY ((skip (""))) aux; 133 134 /* The number of times the latch of the loop is executed. 135 This is an INTEGER_CST or an expression containing symbolic 136 names. Don't access this field directly: 137 number_of_latch_executions computes and caches the computed 138 information in this field. */ 139 tree nb_iterations; 140 141 /* An integer guaranteed to bound the number of iterations of the loop 142 from above. */ 143 double_int nb_iterations_upper_bound; 144 145 /* An integer giving the expected number of iterations of the loop. */ 146 double_int nb_iterations_estimate; 147 148 bool any_upper_bound; 149 bool any_estimate; 150 151 /* An integer estimation of the number of iterations. Estimate_state 152 describes what is the state of the estimation. */ 153 enum loop_estimation estimate_state; 154 155 /* Upper bound on number of iterations of a loop. */ 156 struct nb_iter_bound *bounds; 157 158 /* Head of the cyclic list of the exits of the loop. */ 159 struct loop_exit *exits; 160 161 /* True if the loop can be parallel. */ 162 bool can_be_parallel; 163 164 /* The single induction variable of the loop when the loop is in 165 normal form. */ 166 tree single_iv; 167}; 168 169/* Flags for state of loop structure. */ 170enum 171{ 172 LOOPS_HAVE_PREHEADERS = 1, 173 LOOPS_HAVE_SIMPLE_LATCHES = 2, 174 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4, 175 LOOPS_HAVE_RECORDED_EXITS = 8, 176 LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16, 177 LOOP_CLOSED_SSA = 32, 178 LOOPS_NEED_FIXUP = 64, 179 LOOPS_HAVE_FALLTHRU_PREHEADERS = 128 180}; 181 182#define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \ 183 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS) 184#define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES) 185 186/* Structure to hold CFG information about natural loops within a function. */ 187struct GTY (()) loops { 188 /* State of loops. */ 189 int state; 190 191 /* Array of the loops. */ 192 VEC (loop_p, gc) *larray; 193 194 /* Maps edges to the list of their descriptions as loop exits. Edges 195 whose sources or destinations have loop_father == NULL (which may 196 happen during the cfg manipulations) should not appear in EXITS. */ 197 htab_t GTY((param_is (struct loop_exit))) exits; 198 199 /* Pointer to root of loop hierarchy tree. */ 200 struct loop *tree_root; 201}; 202 203/* Loop recognition. */ 204extern int flow_loops_find (struct loops *); 205extern void disambiguate_loops_with_multiple_latches (void); 206extern void flow_loops_free (struct loops *); 207extern void flow_loops_dump (FILE *, 208 void (*)(const struct loop *, FILE *, int), int); 209extern void flow_loop_dump (const struct loop *, FILE *, 210 void (*)(const struct loop *, FILE *, int), int); 211struct loop *alloc_loop (void); 212extern void flow_loop_free (struct loop *); 213int flow_loop_nodes_find (basic_block, struct loop *); 214void fix_loop_structure (bitmap changed_bbs); 215bool mark_irreducible_loops (void); 216void release_recorded_exits (void); 217void record_loop_exits (void); 218void rescan_loop_exit (edge, bool, bool); 219 220/* Loop data structure manipulation/querying. */ 221extern void flow_loop_tree_node_add (struct loop *, struct loop *); 222extern void flow_loop_tree_node_remove (struct loop *); 223extern void add_loop (struct loop *, struct loop *); 224extern bool flow_loop_nested_p (const struct loop *, const struct loop *); 225extern bool flow_bb_inside_loop_p (const struct loop *, const_basic_block); 226extern struct loop * find_common_loop (struct loop *, struct loop *); 227struct loop *superloop_at_depth (struct loop *, unsigned); 228struct eni_weights_d; 229extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *); 230extern int num_loop_insns (const struct loop *); 231extern int average_num_loop_insns (const struct loop *); 232extern unsigned get_loop_level (const struct loop *); 233extern bool loop_exit_edge_p (const struct loop *, const_edge); 234extern bool is_loop_exit (struct loop *, basic_block); 235extern void mark_loop_exit_edges (void); 236 237/* Loops & cfg manipulation. */ 238extern basic_block *get_loop_body (const struct loop *); 239extern unsigned get_loop_body_with_size (const struct loop *, basic_block *, 240 unsigned); 241extern basic_block *get_loop_body_in_dom_order (const struct loop *); 242extern basic_block *get_loop_body_in_bfs_order (const struct loop *); 243extern basic_block *get_loop_body_in_custom_order (const struct loop *, 244 int (*) (const void *, const void *)); 245 246extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *); 247edge single_exit (const struct loop *); 248extern unsigned num_loop_branches (const struct loop *); 249 250extern edge loop_preheader_edge (const struct loop *); 251extern edge loop_latch_edge (const struct loop *); 252 253extern void add_bb_to_loop (basic_block, struct loop *); 254extern void remove_bb_from_loops (basic_block); 255 256extern void cancel_loop_tree (struct loop *); 257extern void delete_loop (struct loop *); 258 259enum 260{ 261 CP_SIMPLE_PREHEADERS = 1, 262 CP_FALLTHRU_PREHEADERS = 2 263}; 264 265basic_block create_preheader (struct loop *, int); 266extern void create_preheaders (int); 267extern void force_single_succ_latches (void); 268 269extern void verify_loop_structure (void); 270 271/* Loop analysis. */ 272extern bool just_once_each_iteration_p (const struct loop *, const_basic_block); 273gcov_type expected_loop_iterations_unbounded (const struct loop *); 274extern unsigned expected_loop_iterations (const struct loop *); 275extern rtx doloop_condition_get (rtx); 276 277void estimate_numbers_of_iterations_loop (struct loop *); 278HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool); 279bool estimated_loop_iterations (struct loop *, bool, double_int *); 280 281/* Loop manipulation. */ 282extern bool can_duplicate_loop_p (const struct loop *loop); 283 284#define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in 285 duplicate_loop_to_header_edge. */ 286#define DLTHE_RECORD_COPY_NUMBER 2 /* Record copy number in the aux 287 field of newly create BB. */ 288#define DLTHE_FLAG_COMPLETTE_PEEL 4 /* Update frequencies expecting 289 a complete peeling. */ 290 291extern edge create_empty_if_region_on_edge (edge, tree); 292extern struct loop *create_empty_loop_on_edge (edge, tree, tree, tree, tree, 293 tree *, tree *, struct loop *); 294extern struct loop * duplicate_loop (struct loop *, struct loop *); 295extern void duplicate_subloops (struct loop *, struct loop *); 296extern bool duplicate_loop_to_header_edge (struct loop *, edge, 297 unsigned, sbitmap, edge, 298 VEC (edge, heap) **, int); 299extern struct loop *loopify (edge, edge, 300 basic_block, edge, edge, bool, 301 unsigned, unsigned); 302struct loop * loop_version (struct loop *, void *, 303 basic_block *, unsigned, unsigned, unsigned, bool); 304extern bool remove_path (edge); 305void scale_loop_frequencies (struct loop *, int, int); 306 307/* Induction variable analysis. */ 308 309/* The description of induction variable. The things are a bit complicated 310 due to need to handle subregs and extends. The value of the object described 311 by it can be obtained as follows (all computations are done in extend_mode): 312 313 Value in i-th iteration is 314 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)). 315 316 If first_special is true, the value in the first iteration is 317 delta + mult * base 318 319 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is 320 subreg_{mode} (base + i * step) 321 322 The get_iv_value function can be used to obtain these expressions. 323 324 ??? Add a third mode field that would specify the mode in that inner 325 computation is done, which would enable it to be different from the 326 outer one? */ 327 328struct rtx_iv 329{ 330 /* Its base and step (mode of base and step is supposed to be extend_mode, 331 see the description above). */ 332 rtx base, step; 333 334 /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN). */ 335 enum rtx_code extend; 336 337 /* Operations applied in the extended mode. */ 338 rtx delta, mult; 339 340 /* The mode it is extended to. */ 341 enum machine_mode extend_mode; 342 343 /* The mode the variable iterates in. */ 344 enum machine_mode mode; 345 346 /* Whether the first iteration needs to be handled specially. */ 347 unsigned first_special : 1; 348}; 349 350/* The description of an exit from the loop and of the number of iterations 351 till we take the exit. */ 352 353struct niter_desc 354{ 355 /* The edge out of the loop. */ 356 edge out_edge; 357 358 /* The other edge leading from the condition. */ 359 edge in_edge; 360 361 /* True if we are able to say anything about number of iterations of the 362 loop. */ 363 bool simple_p; 364 365 /* True if the loop iterates the constant number of times. */ 366 bool const_iter; 367 368 /* Number of iterations if constant. */ 369 unsigned HOST_WIDEST_INT niter; 370 371 /* Upper bound on the number of iterations. */ 372 unsigned HOST_WIDEST_INT niter_max; 373 374 /* Assumptions under that the rest of the information is valid. */ 375 rtx assumptions; 376 377 /* Assumptions under that the loop ends before reaching the latch, 378 even if value of niter_expr says otherwise. */ 379 rtx noloop_assumptions; 380 381 /* Condition under that the loop is infinite. */ 382 rtx infinite; 383 384 /* Whether the comparison is signed. */ 385 bool signed_p; 386 387 /* The mode in that niter_expr should be computed. */ 388 enum machine_mode mode; 389 390 /* The number of iterations of the loop. */ 391 rtx niter_expr; 392}; 393 394extern void iv_analysis_loop_init (struct loop *); 395extern bool iv_analyze (rtx, rtx, struct rtx_iv *); 396extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *); 397extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *); 398extern rtx get_iv_value (struct rtx_iv *, rtx); 399extern bool biv_p (rtx, rtx); 400extern void find_simple_exit (struct loop *, struct niter_desc *); 401extern void iv_analysis_done (void); 402 403extern struct niter_desc *get_simple_loop_desc (struct loop *loop); 404extern void free_simple_loop_desc (struct loop *loop); 405 406static inline struct niter_desc * 407simple_loop_desc (struct loop *loop) 408{ 409 return (struct niter_desc *) loop->aux; 410} 411 412/* Accessors for the loop structures. */ 413 414/* Returns the loop with index NUM from current_loops. */ 415 416static inline struct loop * 417get_loop (unsigned num) 418{ 419 return VEC_index (loop_p, current_loops->larray, num); 420} 421 422/* Returns the number of superloops of LOOP. */ 423 424static inline unsigned 425loop_depth (const struct loop *loop) 426{ 427 return VEC_length (loop_p, loop->superloops); 428} 429 430/* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost 431 loop. */ 432 433static inline struct loop * 434loop_outer (const struct loop *loop) 435{ 436 unsigned n = VEC_length (loop_p, loop->superloops); 437 438 if (n == 0) 439 return NULL; 440 441 return VEC_index (loop_p, loop->superloops, n - 1); 442} 443 444/* Returns the list of loops in current_loops. */ 445 446static inline VEC (loop_p, gc) * 447get_loops (void) 448{ 449 if (!current_loops) 450 return NULL; 451 452 return current_loops->larray; 453} 454 455/* Returns the number of loops in current_loops (including the removed 456 ones and the fake loop that forms the root of the loop tree). */ 457 458static inline unsigned 459number_of_loops (void) 460{ 461 if (!current_loops) 462 return 0; 463 464 return VEC_length (loop_p, current_loops->larray); 465} 466 467/* Returns true if state of the loops satisfies all properties 468 described by FLAGS. */ 469 470static inline bool 471loops_state_satisfies_p (unsigned flags) 472{ 473 return (current_loops->state & flags) == flags; 474} 475 476/* Sets FLAGS to the loops state. */ 477 478static inline void 479loops_state_set (unsigned flags) 480{ 481 current_loops->state |= flags; 482} 483 484/* Clears FLAGS from the loops state. */ 485 486static inline void 487loops_state_clear (unsigned flags) 488{ 489 if (!current_loops) 490 return; 491 current_loops->state &= ~flags; 492} 493 494/* Loop iterators. */ 495 496/* Flags for loop iteration. */ 497 498enum li_flags 499{ 500 LI_INCLUDE_ROOT = 1, /* Include the fake root of the loop tree. */ 501 LI_FROM_INNERMOST = 2, /* Iterate over the loops in the reverse order, 502 starting from innermost ones. */ 503 LI_ONLY_INNERMOST = 4 /* Iterate only over innermost loops. */ 504}; 505 506/* The iterator for loops. */ 507 508typedef struct 509{ 510 /* The list of loops to visit. */ 511 VEC(int,heap) *to_visit; 512 513 /* The index of the actual loop. */ 514 unsigned idx; 515} loop_iterator; 516 517static inline void 518fel_next (loop_iterator *li, loop_p *loop) 519{ 520 int anum; 521 522 while (VEC_iterate (int, li->to_visit, li->idx, anum)) 523 { 524 li->idx++; 525 *loop = get_loop (anum); 526 if (*loop) 527 return; 528 } 529 530 VEC_free (int, heap, li->to_visit); 531 *loop = NULL; 532} 533 534static inline void 535fel_init (loop_iterator *li, loop_p *loop, unsigned flags) 536{ 537 struct loop *aloop; 538 unsigned i; 539 int mn; 540 541 li->idx = 0; 542 if (!current_loops) 543 { 544 li->to_visit = NULL; 545 *loop = NULL; 546 return; 547 } 548 549 li->to_visit = VEC_alloc (int, heap, number_of_loops ()); 550 mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1; 551 552 if (flags & LI_ONLY_INNERMOST) 553 { 554 for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++) 555 if (aloop != NULL 556 && aloop->inner == NULL 557 && aloop->num >= mn) 558 VEC_quick_push (int, li->to_visit, aloop->num); 559 } 560 else if (flags & LI_FROM_INNERMOST) 561 { 562 /* Push the loops to LI->TO_VISIT in postorder. */ 563 for (aloop = current_loops->tree_root; 564 aloop->inner != NULL; 565 aloop = aloop->inner) 566 continue; 567 568 while (1) 569 { 570 if (aloop->num >= mn) 571 VEC_quick_push (int, li->to_visit, aloop->num); 572 573 if (aloop->next) 574 { 575 for (aloop = aloop->next; 576 aloop->inner != NULL; 577 aloop = aloop->inner) 578 continue; 579 } 580 else if (!loop_outer (aloop)) 581 break; 582 else 583 aloop = loop_outer (aloop); 584 } 585 } 586 else 587 { 588 /* Push the loops to LI->TO_VISIT in preorder. */ 589 aloop = current_loops->tree_root; 590 while (1) 591 { 592 if (aloop->num >= mn) 593 VEC_quick_push (int, li->to_visit, aloop->num); 594 595 if (aloop->inner != NULL) 596 aloop = aloop->inner; 597 else 598 { 599 while (aloop != NULL && aloop->next == NULL) 600 aloop = loop_outer (aloop); 601 if (aloop == NULL) 602 break; 603 aloop = aloop->next; 604 } 605 } 606 } 607 608 fel_next (li, loop); 609} 610 611#define FOR_EACH_LOOP(LI, LOOP, FLAGS) \ 612 for (fel_init (&(LI), &(LOOP), FLAGS); \ 613 (LOOP); \ 614 fel_next (&(LI), &(LOOP))) 615 616#define FOR_EACH_LOOP_BREAK(LI) \ 617 { \ 618 VEC_free (int, heap, (LI)->to_visit); \ 619 break; \ 620 } 621 622/* The properties of the target. */ 623 624extern unsigned target_avail_regs; 625extern unsigned target_res_regs; 626extern unsigned target_reg_cost [2]; 627extern unsigned target_spill_cost [2]; 628 629/* Register pressure estimation for induction variable optimizations & loop 630 invariant motion. */ 631extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool); 632extern void init_set_costs (void); 633 634/* Loop optimizer initialization. */ 635extern void loop_optimizer_init (unsigned); 636extern void loop_optimizer_finalize (void); 637 638/* Optimization passes. */ 639extern void unswitch_loops (void); 640 641enum 642{ 643 UAP_PEEL = 1, /* Enables loop peeling. */ 644 UAP_UNROLL = 2, /* Enables unrolling of loops if it seems profitable. */ 645 UAP_UNROLL_ALL = 4 /* Enables unrolling of all loops. */ 646}; 647 648extern void unroll_and_peel_loops (int); 649extern void doloop_optimize_loops (void); 650extern void move_loop_invariants (void); 651extern bool finite_loop_p (struct loop *); 652 653#endif /* GCC_CFGLOOP_H */ 654