gcc/cfgloop.h

   1 /* Natural loop functions
   2    Copyright (C) 1987-2017 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 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.
  15
  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 #ifndef GCC_CFGLOOP_H
  21 #define GCC_CFGLOOP_H
  22
  23 #include "cfgloopmanip.h"
  24
  25 /* Structure to hold decision about unrolling/peeling.  */
  26 enum lpt_dec
  27 {
  28   LPT_NONE,
  29   LPT_UNROLL_CONSTANT,
  30   LPT_UNROLL_RUNTIME,
  31   LPT_UNROLL_STUPID
  32 };
  33
  34 struct GTY (()) lpt_decision {
  35   enum lpt_dec decision;
  36   unsigned times;
  37 };
  38
  39 /* The type of extend applied to an IV.  */
  40 enum iv_extend_code
  41 {
  42   IV_SIGN_EXTEND,
  43   IV_ZERO_EXTEND,
  44   IV_UNKNOWN_EXTEND
  45 };
  46
  47 /* The structure describing a bound on number of iterations of a loop.  */
  48
  49 struct GTY ((chain_next ("%h.next"))) nb_iter_bound {
  50   /* The statement STMT is executed at most ...  */
  51   gimple *stmt;
  52
  53   /* ... BOUND + 1 times (BOUND must be an unsigned constant).
  54      The + 1 is added for the following reasons:
  55
  56      a) 0 would otherwise be unused, while we would need to care more about
  57         overflows (as MAX + 1 is sometimes produced as the estimate on number
  58         of executions of STMT).
  59      b) it is consistent with the result of number_of_iterations_exit.  */
  60   widest_int bound;
  61
  62   /* True if the statement will cause the loop to be leaved the (at most)
  63      BOUND + 1-st time it is executed, that is, all the statements after it
  64      are executed at most BOUND times.  */
  65   bool is_exit;
  66
  67   /* The next bound in the list.  */
  68   struct nb_iter_bound *next;
  69 };
  70
  71 /* Description of the loop exit.  */
  72
  73 struct GTY ((for_user)) loop_exit {
  74   /* The exit edge.  */
  75   edge e;
  76
  77   /* Previous and next exit in the list of the exits of the loop.  */
  78   struct loop_exit *prev;
  79   struct loop_exit *next;
  80
  81   /* Next element in the list of loops from that E exits.  */
  82   struct loop_exit *next_e;
  83 };
  84
  85 struct loop_exit_hasher : ggc_ptr_hash<loop_exit>
  86 {
  87   typedef edge compare_type;
  88
  89   static hashval_t hash (loop_exit *);
  90   static bool equal (loop_exit *, edge);
  91   static void remove (loop_exit *);
  92 };
  93
  94 typedef struct loop *loop_p;
  95
  96 /* An integer estimation of the number of iterations.  Estimate_state
  97    describes what is the state of the estimation.  */
  98 enum loop_estimation
  99 {
 100   /* Estimate was not computed yet.  */
 101   EST_NOT_COMPUTED,
 102   /* Estimate is ready.  */
 103   EST_AVAILABLE,
 104   EST_LAST
 105 };
 106
 107 /* The structure describing non-overflow control induction variable for
 108    loop's exit edge.  */
 109 struct GTY ((chain_next ("%h.next"))) control_iv {
 110   tree base;
 111   tree step;
 112   struct control_iv *next;
 113 };
 114
 115 /* Structure to hold information for each natural loop.  */
 116 struct GTY ((chain_next ("%h.next"))) loop {
 117   /* Index into loops array.  */
 118   int num;
 119
 120   /* Number of loop insns.  */
 121   unsigned ninsns;
 122
 123   /* Basic block of loop header.  */
 124   basic_block header;
 125
 126   /* Basic block of loop latch.  */
 127   basic_block latch;
 128
 129   /* For loop unrolling/peeling decision.  */
 130   struct lpt_decision lpt_decision;
 131
 132   /* Average number of executed insns per iteration.  */
 133   unsigned av_ninsns;
 134
 135   /* Number of blocks contained within the loop.  */
 136   unsigned num_nodes;
 137
 138   /* Superloops of the loop, starting with the outermost loop.  */
 139   vec<loop_p, va_gc> *superloops;
 140
 141   /* The first inner (child) loop or NULL if innermost loop.  */
 142   struct loop *inner;
 143
 144   /* Link to the next (sibling) loop.  */
 145   struct loop *next;
 146
 147   /* Auxiliary info specific to a pass.  */
 148   PTR GTY ((skip (""))) aux;
 149
 150   /* The number of times the latch of the loop is executed.  This can be an
 151      INTEGER_CST, or a symbolic expression representing the number of
 152      iterations like "N - 1", or a COND_EXPR containing the runtime
 153      conditions under which the number of iterations is non zero.
 154
 155      Don't access this field directly: number_of_latch_executions
 156      computes and caches the computed information in this field.  */
 157   tree nb_iterations;
 158
 159   /* An integer guaranteed to be greater or equal to nb_iterations.  Only
 160      valid if any_upper_bound is true.  */
 161   widest_int nb_iterations_upper_bound;
 162
 163   widest_int nb_iterations_likely_upper_bound;
 164
 165   /* An integer giving an estimate on nb_iterations.  Unlike
 166      nb_iterations_upper_bound, there is no guarantee that it is at least
 167      nb_iterations.  */
 168   widest_int nb_iterations_estimate;
 169
 170   /* If > 0, an integer, where the user asserted that for any
 171      I in [ 0, nb_iterations ) and for any J in
 172      [ I, min ( I + safelen, nb_iterations ) ), the Ith and Jth iterations
 173      of the loop can be safely evaluated concurrently.  */
 174   int safelen;
 175
 176   /* Constraints are generally set by consumers and affect certain
 177      semantics of niter analyzer APIs.  Currently the APIs affected are
 178      number_of_iterations_exit* functions and their callers.  One typical
 179      use case of constraints is to vectorize possibly infinite loop:
 180
 181        1) Compute niter->assumptions by calling niter analyzer API and
 182           record it as possible condition for loop versioning.
 183        2) Clear buffered result of niter/scev analyzer.
 184        3) Set constraint LOOP_C_FINITE assuming the loop is finite.
 185        4) Analyze data references.  Since data reference analysis depends
 186           on niter/scev analyzer, the point is that niter/scev analysis
 187           is done under circumstance of LOOP_C_FINITE constraint.
 188        5) Version the loop with niter->assumptions computed in step 1).
 189        6) Vectorize the versioned loop in which niter->assumptions is
 190           checked to be true.
 191        7) Update constraints in versioned loops so that niter analyzer
 192           in following passes can use it.
 193
 194      Note consumers are usually the loop optimizers and it is consumers'
 195      responsibility to set/clear constraints correctly.  Failing to do
 196      that might result in hard to track down bugs in niter/scev consumers.  */
 197   unsigned constraints;
 198
 199   /* An integer estimation of the number of iterations.  Estimate_state
 200      describes what is the state of the estimation.  */
 201   ENUM_BITFIELD(loop_estimation) estimate_state : 8;
 202
 203   unsigned any_upper_bound : 1;
 204   unsigned any_estimate : 1;
 205   unsigned any_likely_upper_bound : 1;
 206
 207   /* True if the loop can be parallel.  */
 208   unsigned can_be_parallel : 1;
 209
 210   /* True if -Waggressive-loop-optimizations warned about this loop
 211      already.  */
 212   unsigned warned_aggressive_loop_optimizations : 1;
 213
 214   /* True if this loop should never be vectorized.  */
 215   unsigned dont_vectorize : 1;
 216
 217   /* True if we should try harder to vectorize this loop.  */
 218   unsigned force_vectorize : 1;
 219
 220   /* True if the loop is part of an oacc kernels region.  */
 221   unsigned in_oacc_kernels_region : 1;
 222
 223   /* For SIMD loops, this is a unique identifier of the loop, referenced
 224      by IFN_GOMP_SIMD_VF, IFN_GOMP_SIMD_LANE and IFN_GOMP_SIMD_LAST_LANE
 225      builtins.  */
 226   tree simduid;
 227
 228   /* Upper bound on number of iterations of a loop.  */
 229   struct nb_iter_bound *bounds;
 230
 231   /* Non-overflow control ivs of a loop.  */
 232   struct control_iv *control_ivs;
 233
 234   /* Head of the cyclic list of the exits of the loop.  */
 235   struct loop_exit *exits;
 236
 237   /* Number of iteration analysis data for RTL.  */
 238   struct niter_desc *simple_loop_desc;
 239
 240   /* For sanity checking during loop fixup we record here the former
 241      loop header for loops marked for removal.  Note that this prevents
 242      the basic-block from being collected but its index can still be
 243      reused.  */
 244   basic_block former_header;
 245 };
 246
 247 /* Set if the loop is known to be infinite.  */
 248 #define LOOP_C_INFINITE         (1 << 0)
 249 /* Set if the loop is known to be finite without any assumptions.  */
 250 #define LOOP_C_FINITE           (1 << 1)
 251
 252 /* Set C to the LOOP constraint.  */
 253 static inline void
 254 loop_constraint_set (struct loop *loop, unsigned c)
 255 {
 256   loop->constraints |= c;
 257 }
 258
 259 /* Clear C from the LOOP constraint.  */
 260 static inline void
 261 loop_constraint_clear (struct loop *loop, unsigned c)
 262 {
 263   loop->constraints &= ~c;
 264 }
 265
 266 /* Check if C is set in the LOOP constraint.  */
 267 static inline bool
 268 loop_constraint_set_p (struct loop *loop, unsigned c)
 269 {
 270   return (loop->constraints & c) == c;
 271 }
 272
 273 /* Flags for state of loop structure.  */
 274 enum
 275 {
 276   LOOPS_HAVE_PREHEADERS = 1,
 277   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 278   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
 279   LOOPS_HAVE_RECORDED_EXITS = 8,
 280   LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16,
 281   LOOP_CLOSED_SSA = 32,
 282   LOOPS_NEED_FIXUP = 64,
 283   LOOPS_HAVE_FALLTHRU_PREHEADERS = 128
 284 };
 285
 286 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 287                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 288 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
 289
 290 /* Structure to hold CFG information about natural loops within a function.  */
 291 struct GTY (()) loops {
 292   /* State of loops.  */
 293   int state;
 294
 295   /* Array of the loops.  */
 296   vec<loop_p, va_gc> *larray;
 297
 298   /* Maps edges to the list of their descriptions as loop exits.  Edges
 299      whose sources or destinations have loop_father == NULL (which may
 300      happen during the cfg manipulations) should not appear in EXITS.  */
 301   hash_table<loop_exit_hasher> *GTY(()) exits;
 302
 303   /* Pointer to root of loop hierarchy tree.  */
 304   struct loop *tree_root;
 305 };
 306
 307 /* Loop recognition.  */
 308 bool bb_loop_header_p (basic_block);
 309 void init_loops_structure (struct function *, struct loops *, unsigned);
 310 extern struct loops *flow_loops_find (struct loops *);
 311 extern void disambiguate_loops_with_multiple_latches (void);
 312 extern void flow_loops_free (struct loops *);
 313 extern void flow_loops_dump (FILE *,
 314                              void (*)(const struct loop *, FILE *, int), int);
 315 extern void flow_loop_dump (const struct loop *, FILE *,
 316                             void (*)(const struct loop *, FILE *, int), int);
 317 struct loop *alloc_loop (void);
 318 extern void flow_loop_free (struct loop *);
 319 int flow_loop_nodes_find (basic_block, struct loop *);
 320 unsigned fix_loop_structure (bitmap changed_bbs);
 321 bool mark_irreducible_loops (void);
 322 void release_recorded_exits (function *);
 323 void record_loop_exits (void);
 324 void rescan_loop_exit (edge, bool, bool);
 325
 326 /* Loop data structure manipulation/querying.  */
 327 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 328 extern void flow_loop_tree_node_remove (struct loop *);
 329 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 330 extern bool flow_bb_inside_loop_p (const struct loop *, const_basic_block);
 331 extern struct loop * find_common_loop (struct loop *, struct loop *);
 332 struct loop *superloop_at_depth (struct loop *, unsigned);
 333 struct eni_weights;
 334 extern int num_loop_insns (const struct loop *);
 335 extern int average_num_loop_insns (const struct loop *);
 336 extern unsigned get_loop_level (const struct loop *);
 337 extern bool loop_exit_edge_p (const struct loop *, const_edge);
 338 extern bool loop_exits_to_bb_p (struct loop *, basic_block);
 339 extern bool loop_exits_from_bb_p (struct loop *, basic_block);
 340 extern void mark_loop_exit_edges (void);
 341 extern location_t get_loop_location (struct loop *loop);
 342
 343 /* Loops & cfg manipulation.  */
 344 extern basic_block *get_loop_body (const struct loop *);
 345 extern unsigned get_loop_body_with_size (const struct loop *, basic_block *,
 346                                          unsigned);
 347 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 348 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 349 extern basic_block *get_loop_body_in_custom_order (const struct loop *,
 350                                int (*) (const void *, const void *));
 351
 352 extern vec<edge> get_loop_exit_edges (const struct loop *);
 353 extern edge single_exit (const struct loop *);
 354 extern edge single_likely_exit (struct loop *loop);
 355 extern unsigned num_loop_branches (const struct loop *);
 356
 357 extern edge loop_preheader_edge (const struct loop *);
 358 extern edge loop_latch_edge (const struct loop *);
 359
 360 extern void add_bb_to_loop (basic_block, struct loop *);
 361 extern void remove_bb_from_loops (basic_block);
 362
 363 extern void cancel_loop_tree (struct loop *);
 364 extern void delete_loop (struct loop *);
 365
 366
 367 extern void verify_loop_structure (void);
 368
 369 /* Loop analysis.  */
 370 extern bool just_once_each_iteration_p (const struct loop *, const_basic_block);
 371 gcov_type expected_loop_iterations_unbounded (const struct loop *,
 372                                               bool *read_profile_p = NULL);
 373 extern unsigned expected_loop_iterations (struct loop *);
 374 extern rtx doloop_condition_get (rtx_insn *);
 375
 376 void mark_loop_for_removal (loop_p);
 377
 378 /* Induction variable analysis.  */
 379
 380 /* The description of induction variable.  The things are a bit complicated
 381    due to need to handle subregs and extends.  The value of the object described
 382    by it can be obtained as follows (all computations are done in extend_mode):
 383
 384    Value in i-th iteration is
 385      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 386
 387    If first_special is true, the value in the first iteration is
 388      delta + mult * base
 389
 390    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 391      subreg_{mode} (base + i * step)
 392
 393    The get_iv_value function can be used to obtain these expressions.
 394
 395    ??? Add a third mode field that would specify the mode in that inner
 396    computation is done, which would enable it to be different from the
 397    outer one?  */
 398
 399 struct rtx_iv
 400 {
 401   /* Its base and step (mode of base and step is supposed to be extend_mode,
 402      see the description above).  */
 403   rtx base, step;
 404
 405   /* The type of extend applied to it (IV_SIGN_EXTEND, IV_ZERO_EXTEND,
 406      or IV_UNKNOWN_EXTEND).  */
 407   enum iv_extend_code extend;
 408
 409   /* Operations applied in the extended mode.  */
 410   rtx delta, mult;
 411
 412   /* The mode it is extended to.  */
 413   machine_mode extend_mode;
 414
 415   /* The mode the variable iterates in.  */
 416   machine_mode mode;
 417
 418   /* Whether the first iteration needs to be handled specially.  */
 419   unsigned first_special : 1;
 420 };
 421
 422 /* The description of an exit from the loop and of the number of iterations
 423    till we take the exit.  */
 424
 425 struct GTY(()) niter_desc
 426 {
 427   /* The edge out of the loop.  */
 428   edge out_edge;
 429
 430   /* The other edge leading from the condition.  */
 431   edge in_edge;
 432
 433   /* True if we are able to say anything about number of iterations of the
 434      loop.  */
 435   bool simple_p;
 436
 437   /* True if the loop iterates the constant number of times.  */
 438   bool const_iter;
 439
 440   /* Number of iterations if constant.  */
 441   uint64_t niter;
 442
 443   /* Assumptions under that the rest of the information is valid.  */
 444   rtx assumptions;
 445
 446   /* Assumptions under that the loop ends before reaching the latch,
 447      even if value of niter_expr says otherwise.  */
 448   rtx noloop_assumptions;
 449
 450   /* Condition under that the loop is infinite.  */
 451   rtx infinite;
 452
 453   /* Whether the comparison is signed.  */
 454   bool signed_p;
 455
 456   /* The mode in that niter_expr should be computed.  */
 457   machine_mode mode;
 458
 459   /* The number of iterations of the loop.  */
 460   rtx niter_expr;
 461 };
 462
 463 extern void iv_analysis_loop_init (struct loop *);
 464 extern bool iv_analyze (rtx_insn *, rtx, struct rtx_iv *);
 465 extern bool iv_analyze_result (rtx_insn *, rtx, struct rtx_iv *);
 466 extern bool iv_analyze_expr (rtx_insn *, rtx, machine_mode,
 467                              struct rtx_iv *);
 468 extern rtx get_iv_value (struct rtx_iv *, rtx);
 469 extern bool biv_p (rtx_insn *, rtx);
 470 extern void find_simple_exit (struct loop *, struct niter_desc *);
 471 extern void iv_analysis_done (void);
 472
 473 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 474 extern void free_simple_loop_desc (struct loop *loop);
 475
 476 static inline struct niter_desc *
 477 simple_loop_desc (struct loop *loop)
 478 {
 479   return loop->simple_loop_desc;
 480 }
 481
 482 /* Accessors for the loop structures.  */
 483
 484 /* Returns the loop with index NUM from FNs loop tree.  */
 485
 486 static inline struct loop *
 487 get_loop (struct function *fn, unsigned num)
 488 {
 489   return (*loops_for_fn (fn)->larray)[num];
 490 }
 491
 492 /* Returns the number of superloops of LOOP.  */
 493
 494 static inline unsigned
 495 loop_depth (const struct loop *loop)
 496 {
 497   return vec_safe_length (loop->superloops);
 498 }
 499
 500 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
 501    loop.  */
 502
 503 static inline struct loop *
 504 loop_outer (const struct loop *loop)
 505 {
 506   unsigned n = vec_safe_length (loop->superloops);
 507
 508   if (n == 0)
 509     return NULL;
 510
 511   return (*loop->superloops)[n - 1];
 512 }
 513
 514 /* Returns true if LOOP has at least one exit edge.  */
 515
 516 static inline bool
 517 loop_has_exit_edges (const struct loop *loop)
 518 {
 519   return loop->exits->next->e != NULL;
 520 }
 521
 522 /* Returns the list of loops in FN.  */
 523
 524 inline vec<loop_p, va_gc> *
 525 get_loops (struct function *fn)
 526 {
 527   struct loops *loops = loops_for_fn (fn);
 528   if (!loops)
 529     return NULL;
 530
 531   return loops->larray;
 532 }
 533
 534 /* Returns the number of loops in FN (including the removed
 535    ones and the fake loop that forms the root of the loop tree).  */
 536
 537 static inline unsigned
 538 number_of_loops (struct function *fn)
 539 {
 540   struct loops *loops = loops_for_fn (fn);
 541   if (!loops)
 542     return 0;
 543
 544   return vec_safe_length (loops->larray);
 545 }
 546
 547 /* Returns true if state of the loops satisfies all properties
 548    described by FLAGS.  */
 549
 550 static inline bool
 551 loops_state_satisfies_p (function *fn, unsigned flags)
 552 {
 553   return (loops_for_fn (fn)->state & flags) == flags;
 554 }
 555
 556 static inline bool
 557 loops_state_satisfies_p (unsigned flags)
 558 {
 559   return loops_state_satisfies_p (cfun, flags);
 560 }
 561
 562 /* Sets FLAGS to the loops state.  */
 563
 564 static inline void
 565 loops_state_set (function *fn, unsigned flags)
 566 {
 567   loops_for_fn (fn)->state |= flags;
 568 }
 569
 570 static inline void
 571 loops_state_set (unsigned flags)
 572 {
 573   loops_state_set (cfun, flags);
 574 }
 575
 576 /* Clears FLAGS from the loops state.  */
 577
 578 static inline void
 579 loops_state_clear (function *fn, unsigned flags)
 580 {
 581   loops_for_fn (fn)->state &= ~flags;
 582 }
 583
 584 static inline void
 585 loops_state_clear (unsigned flags)
 586 {
 587   if (!current_loops)
 588     return;
 589   loops_state_clear (cfun, flags);
 590 }
 591
 592 /* Check loop structure invariants, if internal consistency checks are
 593    enabled.  */
 594
 595 static inline void
 596 checking_verify_loop_structure (void)
 597 {
 598   /* VERIFY_LOOP_STRUCTURE essentially asserts that no loops need fixups.
 599
 600      The loop optimizers should never make changes to the CFG which
 601      require loop fixups.  But the low level CFG manipulation code may
 602      set the flag conservatively.
 603
 604      Go ahead and clear the flag here.  That avoids the assert inside
 605      VERIFY_LOOP_STRUCTURE, and if there is an inconsistency in the loop
 606      structures VERIFY_LOOP_STRUCTURE will detect it.
 607
 608      This also avoid the compile time cost of excessive fixups.  */
 609   loops_state_clear (LOOPS_NEED_FIXUP);
 610   if (flag_checking)
 611     verify_loop_structure ();
 612 }
 613
 614 /* Loop iterators.  */
 615
 616 /* Flags for loop iteration.  */
 617
 618 enum li_flags
 619 {
 620   LI_INCLUDE_ROOT = 1,          /* Include the fake root of the loop tree.  */
 621   LI_FROM_INNERMOST = 2,        /* Iterate over the loops in the reverse order,
 622                                    starting from innermost ones.  */
 623   LI_ONLY_INNERMOST = 4         /* Iterate only over innermost loops.  */
 624 };
 625
 626 /* The iterator for loops.  */
 627
 628 struct loop_iterator
 629 {
 630   loop_iterator (function *fn, loop_p *loop, unsigned flags);
 631   ~loop_iterator ();
 632
 633   inline loop_p next ();
 634
 635   /* The function we are visiting.  */
 636   function *fn;
 637
 638   /* The list of loops to visit.  */
 639   vec<int> to_visit;
 640
 641   /* The index of the actual loop.  */
 642   unsigned idx;
 643 };
 644
 645 inline loop_p
 646 loop_iterator::next ()
 647 {
 648   int anum;
 649
 650   while (this->to_visit.iterate (this->idx, &anum))
 651     {
 652       this->idx++;
 653       loop_p loop = get_loop (fn, anum);
 654       if (loop)
 655         return loop;
 656     }
 657
 658   return NULL;
 659 }
 660
 661 inline
 662 loop_iterator::loop_iterator (function *fn, loop_p *loop, unsigned flags)
 663 {
 664   struct loop *aloop;
 665   unsigned i;
 666   int mn;
 667
 668   this->idx = 0;
 669   this->fn = fn;
 670   if (!loops_for_fn (fn))
 671     {
 672       this->to_visit.create (0);
 673       *loop = NULL;
 674       return;
 675     }
 676
 677   this->to_visit.create (number_of_loops (fn));
 678   mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
 679
 680   if (flags & LI_ONLY_INNERMOST)
 681     {
 682       for (i = 0; vec_safe_iterate (loops_for_fn (fn)->larray, i, &aloop); i++)
 683         if (aloop != NULL
 684             && aloop->inner == NULL
 685             && aloop->num >= mn)
 686           this->to_visit.quick_push (aloop->num);
 687     }
 688   else if (flags & LI_FROM_INNERMOST)
 689     {
 690       /* Push the loops to LI->TO_VISIT in postorder.  */
 691       for (aloop = loops_for_fn (fn)->tree_root;
 692            aloop->inner != NULL;
 693            aloop = aloop->inner)
 694         continue;
 695
 696       while (1)
 697         {
 698           if (aloop->num >= mn)
 699             this->to_visit.quick_push (aloop->num);
 700
 701           if (aloop->next)
 702             {
 703               for (aloop = aloop->next;
 704                    aloop->inner != NULL;
 705                    aloop = aloop->inner)
 706                 continue;
 707             }
 708           else if (!loop_outer (aloop))
 709             break;
 710           else
 711             aloop = loop_outer (aloop);
 712         }
 713     }
 714   else
 715     {
 716       /* Push the loops to LI->TO_VISIT in preorder.  */
 717       aloop = loops_for_fn (fn)->tree_root;
 718       while (1)
 719         {
 720           if (aloop->num >= mn)
 721             this->to_visit.quick_push (aloop->num);
 722
 723           if (aloop->inner != NULL)
 724             aloop = aloop->inner;
 725           else
 726             {
 727               while (aloop != NULL && aloop->next == NULL)
 728                 aloop = loop_outer (aloop);
 729               if (aloop == NULL)
 730                 break;
 731               aloop = aloop->next;
 732             }
 733         }
 734     }
 735
 736   *loop = this->next ();
 737 }
 738
 739 inline
 740 loop_iterator::~loop_iterator ()
 741 {
 742   this->to_visit.release ();
 743 }
 744
 745 #define FOR_EACH_LOOP(LOOP, FLAGS) \
 746   for (loop_iterator li(cfun, &(LOOP), FLAGS); \
 747        (LOOP); \
 748        (LOOP) = li.next ())
 749
 750 #define FOR_EACH_LOOP_FN(FN, LOOP, FLAGS) \
 751   for (loop_iterator li(fn, &(LOOP), FLAGS); \
 752        (LOOP); \
 753        (LOOP) = li.next ())
 754
 755 /* The properties of the target.  */
 756 struct target_cfgloop {
 757   /* Number of available registers.  */
 758   unsigned x_target_avail_regs;
 759
 760   /* Number of available registers that are call-clobbered.  */
 761   unsigned x_target_clobbered_regs;
 762
 763   /* Number of registers reserved for temporary expressions.  */
 764   unsigned x_target_res_regs;
 765
 766   /* The cost for register when there still is some reserve, but we are
 767      approaching the number of available registers.  */
 768   unsigned x_target_reg_cost[2];
 769
 770   /* The cost for register when we need to spill.  */
 771   unsigned x_target_spill_cost[2];
 772 };
 773
 774 extern struct target_cfgloop default_target_cfgloop;
 775 #if SWITCHABLE_TARGET
 776 extern struct target_cfgloop *this_target_cfgloop;
 777 #else
 778 #define this_target_cfgloop (&default_target_cfgloop)
 779 #endif
 780
 781 #define target_avail_regs \
 782   (this_target_cfgloop->x_target_avail_regs)
 783 #define target_clobbered_regs \
 784   (this_target_cfgloop->x_target_clobbered_regs)
 785 #define target_res_regs \
 786   (this_target_cfgloop->x_target_res_regs)
 787 #define target_reg_cost \
 788   (this_target_cfgloop->x_target_reg_cost)
 789 #define target_spill_cost \
 790   (this_target_cfgloop->x_target_spill_cost)
 791
 792 /* Register pressure estimation for induction variable optimizations & loop
 793    invariant motion.  */
 794 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool, bool);
 795 extern void init_set_costs (void);
 796
 797 /* Loop optimizer initialization.  */
 798 extern void loop_optimizer_init (unsigned);
 799 extern void loop_optimizer_finalize (function *);
 800 inline void
 801 loop_optimizer_finalize ()
 802 {
 803   loop_optimizer_finalize (cfun);
 804 }
 805
 806 /* Optimization passes.  */
 807 enum
 808 {
 809   UAP_UNROLL = 1,       /* Enables unrolling of loops if it seems profitable.  */
 810   UAP_UNROLL_ALL = 2    /* Enables unrolling of all loops.  */
 811 };
 812
 813 extern void doloop_optimize_loops (void);
 814 extern void move_loop_invariants (void);
 815 extern vec<basic_block> get_loop_hot_path (const struct loop *loop);
 816
 817 /* Returns the outermost loop of the loop nest that contains LOOP.*/
 818 static inline struct loop *
 819 loop_outermost (struct loop *loop)
 820 {
 821   unsigned n = vec_safe_length (loop->superloops);
 822
 823   if (n <= 1)
 824     return loop;
 825
 826   return (*loop->superloops)[1];
 827 }
 828
 829 extern void record_niter_bound (struct loop *, const widest_int &, bool, bool);
 830 extern HOST_WIDE_INT get_estimated_loop_iterations_int (struct loop *);
 831 extern HOST_WIDE_INT get_max_loop_iterations_int (const struct loop *);
 832 extern HOST_WIDE_INT get_likely_max_loop_iterations_int (struct loop *);
 833 extern bool get_estimated_loop_iterations (struct loop *loop, widest_int *nit);
 834 extern bool get_max_loop_iterations (const struct loop *loop, widest_int *nit);
 835 extern bool get_likely_max_loop_iterations (struct loop *loop, widest_int *nit);
 836 extern int bb_loop_depth (const_basic_block);
 837
 838 /* Converts VAL to widest_int.  */
 839
 840 static inline widest_int
 841 gcov_type_to_wide_int (gcov_type val)
 842 {
 843   HOST_WIDE_INT a[2];
 844
 845   a[0] = (unsigned HOST_WIDE_INT) val;
 846   /* If HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_WIDEST_INT, avoid shifting by
 847      the size of type.  */
 848   val >>= HOST_BITS_PER_WIDE_INT - 1;
 849   val >>= 1;
 850   a[1] = (unsigned HOST_WIDE_INT) val;
 851
 852   return widest_int::from_array (a, 2);
 853 }
 854 #endif /* GCC_CFGLOOP_H */