gcc/cfgloop.h

   1 /* Natural loop functions
   2    Copyright (C) 1987-2020 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 class GTY ((chain_next ("%h.next"))) nb_iter_bound {
  50 public:
  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   widest_int bound;
  62
  63   /* True if, after executing the statement BOUND + 1 times, we will
  64      leave the loop; that is, all the statements after it are executed at most
  65      BOUND times.  */
  66   bool is_exit;
  67
  68   /* The next bound in the list.  */
  69   class nb_iter_bound *next;
  70 };
  71
  72 /* Description of the loop exit.  */
  73
  74 struct GTY ((for_user)) loop_exit {
  75   /* The exit edge.  */
  76   edge e;
  77
  78   /* Previous and next exit in the list of the exits of the loop.  */
  79   struct loop_exit *prev;
  80   struct loop_exit *next;
  81
  82   /* Next element in the list of loops from that E exits.  */
  83   struct loop_exit *next_e;
  84 };
  85
  86 struct loop_exit_hasher : ggc_ptr_hash<loop_exit>
  87 {
  88   typedef edge compare_type;
  89
  90   static hashval_t hash (loop_exit *);
  91   static bool equal (loop_exit *, edge);
  92   static void remove (loop_exit *);
  93 };
  94
  95 typedef class loop *loop_p;
  96
  97 /* An integer estimation of the number of iterations.  Estimate_state
  98    describes what is the state of the estimation.  */
  99 enum loop_estimation
 100 {
 101   /* Estimate was not computed yet.  */
 102   EST_NOT_COMPUTED,
 103   /* Estimate is ready.  */
 104   EST_AVAILABLE,
 105   EST_LAST
 106 };
 107
 108 /* The structure describing non-overflow control induction variable for
 109    loop's exit edge.  */
 110 struct GTY ((chain_next ("%h.next"))) control_iv {
 111   tree base;
 112   tree step;
 113   struct control_iv *next;
 114 };
 115
 116 /* Structure to hold information for each natural loop.  */
 117 class GTY ((chain_next ("%h.next"))) loop {
 118 public:
 119   /* Index into loops array.  Note indices will never be reused after loop
 120      is destroyed.  */
 121   int num;
 122
 123   /* Number of loop insns.  */
 124   unsigned ninsns;
 125
 126   /* Basic block of loop header.  */
 127   basic_block header;
 128
 129   /* Basic block of loop latch.  */
 130   basic_block latch;
 131
 132   /* For loop unrolling/peeling decision.  */
 133   struct lpt_decision lpt_decision;
 134
 135   /* Average number of executed insns per iteration.  */
 136   unsigned av_ninsns;
 137
 138   /* Number of blocks contained within the loop.  */
 139   unsigned num_nodes;
 140
 141   /* Superloops of the loop, starting with the outermost loop.  */
 142   vec<loop_p, va_gc> *superloops;
 143
 144   /* The first inner (child) loop or NULL if innermost loop.  */
 145   class loop *inner;
 146
 147   /* Link to the next (sibling) loop.  */
 148   class loop *next;
 149
 150   /* Auxiliary info specific to a pass.  */
 151   PTR GTY ((skip (""))) aux;
 152
 153   /* The number of times the latch of the loop is executed.  This can be an
 154      INTEGER_CST, or a symbolic expression representing the number of
 155      iterations like "N - 1", or a COND_EXPR containing the runtime
 156      conditions under which the number of iterations is non zero.
 157
 158      Don't access this field directly: number_of_latch_executions
 159      computes and caches the computed information in this field.  */
 160   tree nb_iterations;
 161
 162   /* An integer guaranteed to be greater or equal to nb_iterations.  Only
 163      valid if any_upper_bound is true.  */
 164   widest_int nb_iterations_upper_bound;
 165
 166   widest_int nb_iterations_likely_upper_bound;
 167
 168   /* An integer giving an estimate on nb_iterations.  Unlike
 169      nb_iterations_upper_bound, there is no guarantee that it is at least
 170      nb_iterations.  */
 171   widest_int nb_iterations_estimate;
 172
 173   /* If > 0, an integer, where the user asserted that for any
 174      I in [ 0, nb_iterations ) and for any J in
 175      [ I, min ( I + safelen, nb_iterations ) ), the Ith and Jth iterations
 176      of the loop can be safely evaluated concurrently.  */
 177   int safelen;
 178
 179   /* Preferred vectorization factor for the loop if non-zero.  */
 180   int simdlen;
 181
 182   /* Constraints are generally set by consumers and affect certain
 183      semantics of niter analyzer APIs.  Currently the APIs affected are
 184      number_of_iterations_exit* functions and their callers.  One typical
 185      use case of constraints is to vectorize possibly infinite loop:
 186
 187        1) Compute niter->assumptions by calling niter analyzer API and
 188           record it as possible condition for loop versioning.
 189        2) Clear buffered result of niter/scev analyzer.
 190        3) Set constraint LOOP_C_FINITE assuming the loop is finite.
 191        4) Analyze data references.  Since data reference analysis depends
 192           on niter/scev analyzer, the point is that niter/scev analysis
 193           is done under circumstance of LOOP_C_FINITE constraint.
 194        5) Version the loop with niter->assumptions computed in step 1).
 195        6) Vectorize the versioned loop in which niter->assumptions is
 196           checked to be true.
 197        7) Update constraints in versioned loops so that niter analyzer
 198           in following passes can use it.
 199
 200      Note consumers are usually the loop optimizers and it is consumers'
 201      responsibility to set/clear constraints correctly.  Failing to do
 202      that might result in hard to track down bugs in niter/scev consumers.  */
 203   unsigned constraints;
 204
 205   /* An integer estimation of the number of iterations.  Estimate_state
 206      describes what is the state of the estimation.  */
 207   ENUM_BITFIELD(loop_estimation) estimate_state : 8;
 208
 209   unsigned any_upper_bound : 1;
 210   unsigned any_estimate : 1;
 211   unsigned any_likely_upper_bound : 1;
 212
 213   /* True if the loop can be parallel.  */
 214   unsigned can_be_parallel : 1;
 215
 216   /* True if -Waggressive-loop-optimizations warned about this loop
 217      already.  */
 218   unsigned warned_aggressive_loop_optimizations : 1;
 219
 220   /* True if this loop should never be vectorized.  */
 221   unsigned dont_vectorize : 1;
 222
 223   /* True if we should try harder to vectorize this loop.  */
 224   unsigned force_vectorize : 1;
 225
 226   /* True if the loop is part of an oacc kernels region.  */
 227   unsigned in_oacc_kernels_region : 1;
 228
 229   /* True if the loop is known to be finite.  This is a localized
 230      flag_finite_loops or similar pragmas state.  */
 231   unsigned finite_p : 1;
 232
 233   /* The number of times to unroll the loop.  0 means no information given,
 234      just do what we always do.  A value of 1 means do not unroll the loop.
 235      A value of USHRT_MAX means unroll with no specific unrolling factor.
 236      Other values means unroll with the given unrolling factor.  */
 237   unsigned short unroll;
 238
 239   /* If this loop was inlined the main clique of the callee which does
 240      not need remapping when copying the loop body.  */
 241   unsigned short owned_clique;
 242
 243   /* For SIMD loops, this is a unique identifier of the loop, referenced
 244      by IFN_GOMP_SIMD_VF, IFN_GOMP_SIMD_LANE and IFN_GOMP_SIMD_LAST_LANE
 245      builtins.  */
 246   tree simduid;
 247
 248   /* In loop optimization, it's common to generate loops from the original
 249      loop.  This field records the index of the original loop which can be
 250      used to track the original loop from newly generated loops.  This can
 251      be done by calling function get_loop (cfun, orig_loop_num).  Note the
 252      original loop could be destroyed for various reasons thus no longer
 253      exists, as a result, function call to get_loop returns NULL pointer.
 254      In this case, this field should not be used and needs to be cleared
 255      whenever possible.  */
 256   int orig_loop_num;
 257
 258   /* Upper bound on number of iterations of a loop.  */
 259   class nb_iter_bound *bounds;
 260
 261   /* Non-overflow control ivs of a loop.  */
 262   struct control_iv *control_ivs;
 263
 264   /* Head of the cyclic list of the exits of the loop.  */
 265   struct loop_exit *exits;
 266
 267   /* Number of iteration analysis data for RTL.  */
 268   class niter_desc *simple_loop_desc;
 269
 270   /* For sanity checking during loop fixup we record here the former
 271      loop header for loops marked for removal.  Note that this prevents
 272      the basic-block from being collected but its index can still be
 273      reused.  */
 274   basic_block former_header;
 275 };
 276
 277 /* Set if the loop is known to be infinite.  */
 278 #define LOOP_C_INFINITE         (1 << 0)
 279 /* Set if the loop is known to be finite without any assumptions.  */
 280 #define LOOP_C_FINITE           (1 << 1)
 281
 282 /* Set C to the LOOP constraint.  */
 283 static inline void
 284 loop_constraint_set (class loop *loop, unsigned c)
 285 {
 286   loop->constraints |= c;
 287 }
 288
 289 /* Clear C from the LOOP constraint.  */
 290 static inline void
 291 loop_constraint_clear (class loop *loop, unsigned c)
 292 {
 293   loop->constraints &= ~c;
 294 }
 295
 296 /* Check if C is set in the LOOP constraint.  */
 297 static inline bool
 298 loop_constraint_set_p (class loop *loop, unsigned c)
 299 {
 300   return (loop->constraints & c) == c;
 301 }
 302
 303 /* Flags for state of loop structure.  */
 304 enum
 305 {
 306   LOOPS_HAVE_PREHEADERS = 1,
 307   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 308   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
 309   LOOPS_HAVE_RECORDED_EXITS = 8,
 310   LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16,
 311   LOOP_CLOSED_SSA = 32,
 312   LOOPS_NEED_FIXUP = 64,
 313   LOOPS_HAVE_FALLTHRU_PREHEADERS = 128
 314 };
 315
 316 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 317                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 318 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
 319
 320 /* Structure to hold CFG information about natural loops within a function.  */
 321 struct GTY (()) loops {
 322   /* State of loops.  */
 323   int state;
 324
 325   /* Array of the loops.  */
 326   vec<loop_p, va_gc> *larray;
 327
 328   /* Maps edges to the list of their descriptions as loop exits.  Edges
 329      whose sources or destinations have loop_father == NULL (which may
 330      happen during the cfg manipulations) should not appear in EXITS.  */
 331   hash_table<loop_exit_hasher> *GTY(()) exits;
 332
 333   /* Pointer to root of loop hierarchy tree.  */
 334   class loop *tree_root;
 335 };
 336
 337 /* Loop recognition.  */
 338 bool bb_loop_header_p (basic_block);
 339 void init_loops_structure (struct function *, struct loops *, unsigned);
 340 extern struct loops *flow_loops_find (struct loops *);
 341 extern void disambiguate_loops_with_multiple_latches (void);
 342 extern void flow_loops_free (struct loops *);
 343 extern void flow_loops_dump (FILE *,
 344                              void (*)(const class loop *, FILE *, int), int);
 345 extern void flow_loop_dump (const class loop *, FILE *,
 346                             void (*)(const class loop *, FILE *, int), int);
 347 class loop *alloc_loop (void);
 348 extern void flow_loop_free (class loop *);
 349 int flow_loop_nodes_find (basic_block, class loop *);
 350 unsigned fix_loop_structure (bitmap changed_bbs);
 351 bool mark_irreducible_loops (void);
 352 void release_recorded_exits (function *);
 353 void record_loop_exits (void);
 354 void rescan_loop_exit (edge, bool, bool);
 355 void sort_sibling_loops (function *);
 356
 357 /* Loop data structure manipulation/querying.  */
 358 extern void flow_loop_tree_node_add (class loop *, class loop *,
 359                                      class loop * = NULL);
 360 extern void flow_loop_tree_node_remove (class loop *);
 361 extern bool flow_loop_nested_p  (const class loop *, const class loop *);
 362 extern bool flow_bb_inside_loop_p (const class loop *, const_basic_block);
 363 extern class loop * find_common_loop (class loop *, class loop *);
 364 class loop *superloop_at_depth (class loop *, unsigned);
 365 struct eni_weights;
 366 extern int num_loop_insns (const class loop *);
 367 extern int average_num_loop_insns (const class loop *);
 368 extern unsigned get_loop_level (const class loop *);
 369 extern bool loop_exit_edge_p (const class loop *, const_edge);
 370 extern bool loop_exits_to_bb_p (class loop *, basic_block);
 371 extern bool loop_exits_from_bb_p (class loop *, basic_block);
 372 extern void mark_loop_exit_edges (void);
 373 extern dump_user_location_t get_loop_location (class loop *loop);
 374
 375 /* Loops & cfg manipulation.  */
 376 extern basic_block *get_loop_body (const class loop *);
 377 extern unsigned get_loop_body_with_size (const class loop *, basic_block *,
 378                                          unsigned);
 379 extern basic_block *get_loop_body_in_dom_order (const class loop *);
 380 extern basic_block *get_loop_body_in_bfs_order (const class loop *);
 381 extern basic_block *get_loop_body_in_custom_order (const class loop *,
 382                                int (*) (const void *, const void *));
 383 extern basic_block *get_loop_body_in_custom_order (const class loop *, void *,
 384                                int (*) (const void *, const void *, void *));
 385
 386 extern auto_vec<edge> get_loop_exit_edges (const class loop *, basic_block * = NULL);
 387 extern edge single_exit (const class loop *);
 388 extern edge single_likely_exit (class loop *loop, vec<edge>);
 389 extern unsigned num_loop_branches (const class loop *);
 390
 391 extern edge loop_preheader_edge (const class loop *);
 392 extern edge loop_latch_edge (const class loop *);
 393
 394 extern void add_bb_to_loop (basic_block, class loop *);
 395 extern void remove_bb_from_loops (basic_block);
 396
 397 extern void cancel_loop_tree (class loop *);
 398 extern void delete_loop (class loop *);
 399
 400
 401 extern void verify_loop_structure (void);
 402
 403 /* Loop analysis.  */
 404 extern bool just_once_each_iteration_p (const class loop *, const_basic_block);
 405 gcov_type expected_loop_iterations_unbounded (const class loop *,
 406                                               bool *read_profile_p = NULL, bool by_profile_only = false);
 407 extern unsigned expected_loop_iterations (class loop *);
 408 extern rtx doloop_condition_get (rtx_insn *);
 409
 410 void mark_loop_for_removal (loop_p);
 411
 412 /* Induction variable analysis.  */
 413
 414 /* The description of induction variable.  The things are a bit complicated
 415    due to need to handle subregs and extends.  The value of the object described
 416    by it can be obtained as follows (all computations are done in extend_mode):
 417
 418    Value in i-th iteration is
 419      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 420
 421    If first_special is true, the value in the first iteration is
 422      delta + mult * base
 423
 424    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 425      subreg_{mode} (base + i * step)
 426
 427    The get_iv_value function can be used to obtain these expressions.
 428
 429    ??? Add a third mode field that would specify the mode in that inner
 430    computation is done, which would enable it to be different from the
 431    outer one?  */
 432
 433 class rtx_iv
 434 {
 435 public:
 436   /* Its base and step (mode of base and step is supposed to be extend_mode,
 437      see the description above).  */
 438   rtx base, step;
 439
 440   /* The type of extend applied to it (IV_SIGN_EXTEND, IV_ZERO_EXTEND,
 441      or IV_UNKNOWN_EXTEND).  */
 442   enum iv_extend_code extend;
 443
 444   /* Operations applied in the extended mode.  */
 445   rtx delta, mult;
 446
 447   /* The mode it is extended to.  */
 448   scalar_int_mode extend_mode;
 449
 450   /* The mode the variable iterates in.  */
 451   scalar_int_mode mode;
 452
 453   /* Whether the first iteration needs to be handled specially.  */
 454   unsigned first_special : 1;
 455 };
 456
 457 /* The description of an exit from the loop and of the number of iterations
 458    till we take the exit.  */
 459
 460 class GTY(()) niter_desc
 461 {
 462 public:
 463   /* The edge out of the loop.  */
 464   edge out_edge;
 465
 466   /* The other edge leading from the condition.  */
 467   edge in_edge;
 468
 469   /* True if we are able to say anything about number of iterations of the
 470      loop.  */
 471   bool simple_p;
 472
 473   /* True if the loop iterates the constant number of times.  */
 474   bool const_iter;
 475
 476   /* Number of iterations if constant.  */
 477   uint64_t niter;
 478
 479   /* Assumptions under that the rest of the information is valid.  */
 480   rtx assumptions;
 481
 482   /* Assumptions under that the loop ends before reaching the latch,
 483      even if value of niter_expr says otherwise.  */
 484   rtx noloop_assumptions;
 485
 486   /* Condition under that the loop is infinite.  */
 487   rtx infinite;
 488
 489   /* Whether the comparison is signed.  */
 490   bool signed_p;
 491
 492   /* The mode in that niter_expr should be computed.  */
 493   scalar_int_mode mode;
 494
 495   /* The number of iterations of the loop.  */
 496   rtx niter_expr;
 497 };
 498
 499 extern void iv_analysis_loop_init (class loop *);
 500 extern bool iv_analyze (rtx_insn *, scalar_int_mode, rtx, class rtx_iv *);
 501 extern bool iv_analyze_result (rtx_insn *, rtx, class rtx_iv *);
 502 extern bool iv_analyze_expr (rtx_insn *, scalar_int_mode, rtx,
 503                              class rtx_iv *);
 504 extern rtx get_iv_value (class rtx_iv *, rtx);
 505 extern bool biv_p (rtx_insn *, scalar_int_mode, rtx);
 506 extern void iv_analysis_done (void);
 507
 508 extern class niter_desc *get_simple_loop_desc (class loop *loop);
 509 extern void free_simple_loop_desc (class loop *loop);
 510
 511 static inline class niter_desc *
 512 simple_loop_desc (class loop *loop)
 513 {
 514   return loop->simple_loop_desc;
 515 }
 516
 517 /* Accessors for the loop structures.  */
 518
 519 /* Returns the loop with index NUM from FNs loop tree.  */
 520
 521 static inline class loop *
 522 get_loop (struct function *fn, unsigned num)
 523 {
 524   return (*loops_for_fn (fn)->larray)[num];
 525 }
 526
 527 /* Returns the number of superloops of LOOP.  */
 528
 529 static inline unsigned
 530 loop_depth (const class loop *loop)
 531 {
 532   return vec_safe_length (loop->superloops);
 533 }
 534
 535 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
 536    loop.  */
 537
 538 static inline class loop *
 539 loop_outer (const class loop *loop)
 540 {
 541   unsigned n = vec_safe_length (loop->superloops);
 542
 543   if (n == 0)
 544     return NULL;
 545
 546   return (*loop->superloops)[n - 1];
 547 }
 548
 549 /* Returns true if LOOP has at least one exit edge.  */
 550
 551 static inline bool
 552 loop_has_exit_edges (const class loop *loop)
 553 {
 554   return loop->exits->next->e != NULL;
 555 }
 556
 557 /* Returns the list of loops in FN.  */
 558
 559 inline vec<loop_p, va_gc> *
 560 get_loops (struct function *fn)
 561 {
 562   struct loops *loops = loops_for_fn (fn);
 563   if (!loops)
 564     return NULL;
 565
 566   return loops->larray;
 567 }
 568
 569 /* Returns the number of loops in FN (including the removed
 570    ones and the fake loop that forms the root of the loop tree).  */
 571
 572 static inline unsigned
 573 number_of_loops (struct function *fn)
 574 {
 575   struct loops *loops = loops_for_fn (fn);
 576   if (!loops)
 577     return 0;
 578
 579   return vec_safe_length (loops->larray);
 580 }
 581
 582 /* Returns true if state of the loops satisfies all properties
 583    described by FLAGS.  */
 584
 585 static inline bool
 586 loops_state_satisfies_p (function *fn, unsigned flags)
 587 {
 588   return (loops_for_fn (fn)->state & flags) == flags;
 589 }
 590
 591 static inline bool
 592 loops_state_satisfies_p (unsigned flags)
 593 {
 594   return loops_state_satisfies_p (cfun, flags);
 595 }
 596
 597 /* Sets FLAGS to the loops state.  */
 598
 599 static inline void
 600 loops_state_set (function *fn, unsigned flags)
 601 {
 602   loops_for_fn (fn)->state |= flags;
 603 }
 604
 605 static inline void
 606 loops_state_set (unsigned flags)
 607 {
 608   loops_state_set (cfun, flags);
 609 }
 610
 611 /* Clears FLAGS from the loops state.  */
 612
 613 static inline void
 614 loops_state_clear (function *fn, unsigned flags)
 615 {
 616   loops_for_fn (fn)->state &= ~flags;
 617 }
 618
 619 static inline void
 620 loops_state_clear (unsigned flags)
 621 {
 622   if (!current_loops)
 623     return;
 624   loops_state_clear (cfun, flags);
 625 }
 626
 627 /* Check loop structure invariants, if internal consistency checks are
 628    enabled.  */
 629
 630 static inline void
 631 checking_verify_loop_structure (void)
 632 {
 633   /* VERIFY_LOOP_STRUCTURE essentially asserts that no loops need fixups.
 634
 635      The loop optimizers should never make changes to the CFG which
 636      require loop fixups.  But the low level CFG manipulation code may
 637      set the flag conservatively.
 638
 639      Go ahead and clear the flag here.  That avoids the assert inside
 640      VERIFY_LOOP_STRUCTURE, and if there is an inconsistency in the loop
 641      structures VERIFY_LOOP_STRUCTURE will detect it.
 642
 643      This also avoid the compile time cost of excessive fixups.  */
 644   loops_state_clear (LOOPS_NEED_FIXUP);
 645   if (flag_checking)
 646     verify_loop_structure ();
 647 }
 648
 649 /* Loop iterators.  */
 650
 651 /* Flags for loop iteration.  */
 652
 653 enum li_flags
 654 {
 655   LI_INCLUDE_ROOT = 1,          /* Include the fake root of the loop tree.  */
 656   LI_FROM_INNERMOST = 2,        /* Iterate over the loops in the reverse order,
 657                                    starting from innermost ones.  */
 658   LI_ONLY_INNERMOST = 4         /* Iterate only over innermost loops.  */
 659 };
 660
 661 /* The iterator for loops.  */
 662
 663 class loop_iterator
 664 {
 665 public:
 666   loop_iterator (function *fn, loop_p *loop, unsigned flags);
 667
 668   inline loop_p next ();
 669
 670   /* The function we are visiting.  */
 671   function *fn;
 672
 673   /* The list of loops to visit.  */
 674   auto_vec<int, 16> to_visit;
 675
 676   /* The index of the actual loop.  */
 677   unsigned idx;
 678 };
 679
 680 inline loop_p
 681 loop_iterator::next ()
 682 {
 683   int anum;
 684
 685   while (this->to_visit.iterate (this->idx, &anum))
 686     {
 687       this->idx++;
 688       loop_p loop = get_loop (fn, anum);
 689       if (loop)
 690         return loop;
 691     }
 692
 693   return NULL;
 694 }
 695
 696 inline
 697 loop_iterator::loop_iterator (function *fn, loop_p *loop, unsigned flags)
 698 {
 699   class loop *aloop;
 700   unsigned i;
 701   int mn;
 702
 703   this->idx = 0;
 704   this->fn = fn;
 705   if (!loops_for_fn (fn))
 706     {
 707       *loop = NULL;
 708       return;
 709     }
 710
 711   this->to_visit.reserve_exact (number_of_loops (fn));
 712   mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
 713
 714   if (flags & LI_ONLY_INNERMOST)
 715     {
 716       for (i = 0; vec_safe_iterate (loops_for_fn (fn)->larray, i, &aloop); i++)
 717         if (aloop != NULL
 718             && aloop->inner == NULL
 719             && aloop->num >= mn)
 720           this->to_visit.quick_push (aloop->num);
 721     }
 722   else if (flags & LI_FROM_INNERMOST)
 723     {
 724       /* Push the loops to LI->TO_VISIT in postorder.  */
 725       for (aloop = loops_for_fn (fn)->tree_root;
 726            aloop->inner != NULL;
 727            aloop = aloop->inner)
 728         continue;
 729
 730       while (1)
 731         {
 732           if (aloop->num >= mn)
 733             this->to_visit.quick_push (aloop->num);
 734
 735           if (aloop->next)
 736             {
 737               for (aloop = aloop->next;
 738                    aloop->inner != NULL;
 739                    aloop = aloop->inner)
 740                 continue;
 741             }
 742           else if (!loop_outer (aloop))
 743             break;
 744           else
 745             aloop = loop_outer (aloop);
 746         }
 747     }
 748   else
 749     {
 750       /* Push the loops to LI->TO_VISIT in preorder.  */
 751       aloop = loops_for_fn (fn)->tree_root;
 752       while (1)
 753         {
 754           if (aloop->num >= mn)
 755             this->to_visit.quick_push (aloop->num);
 756
 757           if (aloop->inner != NULL)
 758             aloop = aloop->inner;
 759           else
 760             {
 761               while (aloop != NULL && aloop->next == NULL)
 762                 aloop = loop_outer (aloop);
 763               if (aloop == NULL)
 764                 break;
 765               aloop = aloop->next;
 766             }
 767         }
 768     }
 769
 770   *loop = this->next ();
 771 }
 772
 773 #define FOR_EACH_LOOP(LOOP, FLAGS) \
 774   for (loop_iterator li(cfun, &(LOOP), FLAGS); \
 775        (LOOP); \
 776        (LOOP) = li.next ())
 777
 778 #define FOR_EACH_LOOP_FN(FN, LOOP, FLAGS) \
 779   for (loop_iterator li(FN, &(LOOP), FLAGS); \
 780        (LOOP); \
 781        (LOOP) = li.next ())
 782
 783 /* The properties of the target.  */
 784 struct target_cfgloop {
 785   /* Number of available registers.  */
 786   unsigned x_target_avail_regs;
 787
 788   /* Number of available registers that are call-clobbered.  */
 789   unsigned x_target_clobbered_regs;
 790
 791   /* Number of registers reserved for temporary expressions.  */
 792   unsigned x_target_res_regs;
 793
 794   /* The cost for register when there still is some reserve, but we are
 795      approaching the number of available registers.  */
 796   unsigned x_target_reg_cost[2];
 797
 798   /* The cost for register when we need to spill.  */
 799   unsigned x_target_spill_cost[2];
 800 };
 801
 802 extern struct target_cfgloop default_target_cfgloop;
 803 #if SWITCHABLE_TARGET
 804 extern struct target_cfgloop *this_target_cfgloop;
 805 #else
 806 #define this_target_cfgloop (&default_target_cfgloop)
 807 #endif
 808
 809 #define target_avail_regs \
 810   (this_target_cfgloop->x_target_avail_regs)
 811 #define target_clobbered_regs \
 812   (this_target_cfgloop->x_target_clobbered_regs)
 813 #define target_res_regs \
 814   (this_target_cfgloop->x_target_res_regs)
 815 #define target_reg_cost \
 816   (this_target_cfgloop->x_target_reg_cost)
 817 #define target_spill_cost \
 818   (this_target_cfgloop->x_target_spill_cost)
 819
 820 /* Register pressure estimation for induction variable optimizations & loop
 821    invariant motion.  */
 822 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool, bool);
 823 extern void init_set_costs (void);
 824
 825 /* Loop optimizer initialization.  */
 826 extern void loop_optimizer_init (unsigned);
 827 extern void loop_optimizer_finalize (function *, bool = false);
 828 inline void
 829 loop_optimizer_finalize ()
 830 {
 831   loop_optimizer_finalize (cfun);
 832 }
 833
 834 /* Optimization passes.  */
 835 enum
 836 {
 837   UAP_UNROLL = 1,       /* Enables unrolling of loops if it seems profitable.  */
 838   UAP_UNROLL_ALL = 2    /* Enables unrolling of all loops.  */
 839 };
 840
 841 extern void doloop_optimize_loops (void);
 842 extern void move_loop_invariants (void);
 843 extern vec<basic_block> get_loop_hot_path (const class loop *loop);
 844
 845 /* Returns the outermost loop of the loop nest that contains LOOP.*/
 846 static inline class loop *
 847 loop_outermost (class loop *loop)
 848 {
 849   unsigned n = vec_safe_length (loop->superloops);
 850
 851   if (n <= 1)
 852     return loop;
 853
 854   return (*loop->superloops)[1];
 855 }
 856
 857 extern void record_niter_bound (class loop *, const widest_int &, bool, bool);
 858 extern HOST_WIDE_INT get_estimated_loop_iterations_int (class loop *);
 859 extern HOST_WIDE_INT get_max_loop_iterations_int (const class loop *);
 860 extern HOST_WIDE_INT get_likely_max_loop_iterations_int (class loop *);
 861 extern bool get_estimated_loop_iterations (class loop *loop, widest_int *nit);
 862 extern bool get_max_loop_iterations (const class loop *loop, widest_int *nit);
 863 extern bool get_likely_max_loop_iterations (class loop *loop, widest_int *nit);
 864 extern int bb_loop_depth (const_basic_block);
 865
 866 /* Converts VAL to widest_int.  */
 867
 868 static inline widest_int
 869 gcov_type_to_wide_int (gcov_type val)
 870 {
 871   HOST_WIDE_INT a[2];
 872
 873   a[0] = (unsigned HOST_WIDE_INT) val;
 874   /* If HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_WIDEST_INT, avoid shifting by
 875      the size of type.  */
 876   val >>= HOST_BITS_PER_WIDE_INT - 1;
 877   val >>= 1;
 878   a[1] = (unsigned HOST_WIDE_INT) val;
 879
 880   return widest_int::from_array (a, 2);
 881 }
 882 #endif /* GCC_CFGLOOP_H */