gcc/cfgloop.h

   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 #include "bitmap.h"
  31 #include "sbitmap.h"
  32
  33 /* Structure to hold decision about unrolling/peeling.  */
  34 enum lpt_dec
  35 {
  36   LPT_NONE,
  37   LPT_PEEL_COMPLETELY,
  38   LPT_PEEL_SIMPLE,
  39   LPT_UNROLL_CONSTANT,
  40   LPT_UNROLL_RUNTIME,
  41   LPT_UNROLL_STUPID
  42 };
  43
  44 struct GTY (()) lpt_decision {
  45   enum lpt_dec decision;
  46   unsigned times;
  47 };
  48
  49 /* The structure describing a bound on number of iterations of a loop.  */
  50
  51 struct GTY ((chain_next ("%h.next"))) nb_iter_bound {
  52   /* The statement STMT is executed at most ...  */
  53   gimple stmt;
  54
  55   /* ... BOUND + 1 times (BOUND must be an unsigned constant).
  56      The + 1 is added for the following reasons:
  57
  58      a) 0 would otherwise be unused, while we would need to care more about
  59         overflows (as MAX + 1 is sometimes produced as the estimate on number
  60         of executions of STMT).
  61      b) it is consistent with the result of number_of_iterations_exit.  */
  62   double_int bound;
  63
  64   /* True if the statement will cause the loop to be leaved the (at most)
  65      BOUND + 1-st time it is executed, that is, all the statements after it
  66      are executed at most BOUND times.  */
  67   bool is_exit;
  68
  69   /* The next bound in the list.  */
  70   struct nb_iter_bound *next;
  71 };
  72
  73 /* Description of the loop exit.  */
  74
  75 struct GTY (()) loop_exit {
  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 GTY ((chain_next ("%h.next"))) loop {
 104   /* Index into loops array.  */
 105   int num;
 106
 107   /* Number of loop insns.  */
 108   unsigned ninsns;
 109
 110   /* Basic block of loop header.  */
 111   struct basic_block_def *header;
 112
 113   /* Basic block of loop latch.  */
 114   struct basic_block_def *latch;
 115
 116   /* For loop unrolling/peeling decision.  */
 117   struct lpt_decision lpt_decision;
 118
 119   /* Average number of executed insns per iteration.  */
 120   unsigned av_ninsns;
 121
 122   /* Number of blocks contained within the loop.  */
 123   unsigned num_nodes;
 124
 125   /* Superloops of the loop, starting with the outermost loop.  */
 126   VEC (loop_p, gc) *superloops;
 127
 128   /* The first inner (child) loop or NULL if innermost loop.  */
 129   struct loop *inner;
 130
 131   /* Link to the next (sibling) loop.  */
 132   struct loop *next;
 133
 134   /* Auxiliary info specific to a pass.  */
 135   PTR GTY ((skip (""))) aux;
 136
 137   /* The number of times the latch of the loop is executed.
 138      This is an INTEGER_CST or an expression containing symbolic
 139      names.  Don't access this field directly:
 140      number_of_latch_executions computes and caches the computed
 141      information in this field.  */
 142   tree nb_iterations;
 143
 144   /* An integer guaranteed to bound the number of iterations of the loop
 145      from above.  */
 146   double_int nb_iterations_upper_bound;
 147
 148   /* An integer giving the expected number of iterations of the loop.  */
 149   double_int nb_iterations_estimate;
 150
 151   bool any_upper_bound;
 152   bool any_estimate;
 153
 154   /* True if the loop can be parallel.  */
 155   bool can_be_parallel;
 156
 157   /* An integer estimation of the number of iterations.  Estimate_state
 158      describes what is the state of the estimation.  */
 159   enum loop_estimation estimate_state;
 160
 161   /* Upper bound on number of iterations of a loop.  */
 162   struct nb_iter_bound *bounds;
 163
 164   /* Head of the cyclic list of the exits of the loop.  */
 165   struct loop_exit *exits;
 166
 167   /* The single induction variable of the loop when the loop is in
 168      normal form.  */
 169   tree single_iv;
 170 };
 171
 172 /* Flags for state of loop structure.  */
 173 enum
 174 {
 175   LOOPS_HAVE_PREHEADERS = 1,
 176   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 177   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
 178   LOOPS_HAVE_RECORDED_EXITS = 8,
 179   LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16,
 180   LOOP_CLOSED_SSA = 32,
 181   LOOPS_NEED_FIXUP = 64,
 182   LOOPS_HAVE_FALLTHRU_PREHEADERS = 128
 183 };
 184
 185 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 186                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 187 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
 188
 189 /* Structure to hold CFG information about natural loops within a function.  */
 190 struct GTY (()) loops {
 191   /* State of loops.  */
 192   int state;
 193
 194   /* Array of the loops.  */
 195   VEC (loop_p, gc) *larray;
 196
 197   /* Maps edges to the list of their descriptions as loop exits.  Edges
 198      whose sources or destinations have loop_father == NULL (which may
 199      happen during the cfg manipulations) should not appear in EXITS.  */
 200   htab_t GTY((param_is (struct loop_exit))) exits;
 201
 202   /* Pointer to root of loop hierarchy tree.  */
 203   struct loop *tree_root;
 204 };
 205
 206 /* Loop recognition.  */
 207 extern int flow_loops_find (struct loops *);
 208 extern void disambiguate_loops_with_multiple_latches (void);
 209 extern void flow_loops_free (struct loops *);
 210 extern void flow_loops_dump (FILE *,
 211                              void (*)(const struct loop *, FILE *, int), int);
 212 extern void flow_loop_dump (const struct loop *, FILE *,
 213                             void (*)(const struct loop *, FILE *, int), int);
 214 struct loop *alloc_loop (void);
 215 extern void flow_loop_free (struct loop *);
 216 int flow_loop_nodes_find (basic_block, struct loop *);
 217 void fix_loop_structure (bitmap changed_bbs);
 218 bool mark_irreducible_loops (void);
 219 void release_recorded_exits (void);
 220 void record_loop_exits (void);
 221 void rescan_loop_exit (edge, bool, bool);
 222
 223 /* Loop data structure manipulation/querying.  */
 224 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 225 extern void flow_loop_tree_node_remove (struct loop *);
 226 extern void add_loop (struct loop *, struct loop *);
 227 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 228 extern bool flow_bb_inside_loop_p (const struct loop *, const_basic_block);
 229 extern struct loop * find_common_loop (struct loop *, struct loop *);
 230 struct loop *superloop_at_depth (struct loop *, unsigned);
 231 struct eni_weights_d;
 232 extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *);
 233 extern int num_loop_insns (const struct loop *);
 234 extern int average_num_loop_insns (const struct loop *);
 235 extern unsigned get_loop_level (const struct loop *);
 236 extern bool loop_exit_edge_p (const struct loop *, const_edge);
 237 extern bool is_loop_exit (struct loop *, basic_block);
 238 extern void mark_loop_exit_edges (void);
 239
 240 /* Loops & cfg manipulation.  */
 241 extern basic_block *get_loop_body (const struct loop *);
 242 extern unsigned get_loop_body_with_size (const struct loop *, basic_block *,
 243                                          unsigned);
 244 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 245 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 246 extern basic_block *get_loop_body_in_custom_order (const struct loop *,
 247                                int (*) (const void *, const void *));
 248
 249 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
 250 edge single_exit (const struct loop *);
 251 extern unsigned num_loop_branches (const struct loop *);
 252
 253 extern edge loop_preheader_edge (const struct loop *);
 254 extern edge loop_latch_edge (const struct loop *);
 255
 256 extern void add_bb_to_loop (basic_block, struct loop *);
 257 extern void remove_bb_from_loops (basic_block);
 258
 259 extern void cancel_loop_tree (struct loop *);
 260 extern void delete_loop (struct loop *);
 261
 262 enum
 263 {
 264   CP_SIMPLE_PREHEADERS = 1,
 265   CP_FALLTHRU_PREHEADERS = 2
 266 };
 267
 268 basic_block create_preheader (struct loop *, int);
 269 extern void create_preheaders (int);
 270 extern void force_single_succ_latches (void);
 271
 272 extern void verify_loop_structure (void);
 273
 274 /* Loop analysis.  */
 275 extern bool just_once_each_iteration_p (const struct loop *, const_basic_block);
 276 gcov_type expected_loop_iterations_unbounded (const struct loop *);
 277 extern unsigned expected_loop_iterations (const struct loop *);
 278 extern rtx doloop_condition_get (rtx);
 279
 280 void estimate_numbers_of_iterations_loop (struct loop *);
 281 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool);
 282 bool estimated_loop_iterations (struct loop *, bool, double_int *);
 283
 284 /* Loop manipulation.  */
 285 extern bool can_duplicate_loop_p (const struct loop *loop);
 286
 287 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 288                                            duplicate_loop_to_header_edge.  */
 289 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 290                                            field of newly create BB.  */
 291 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 292                                            a complete peeling.  */
 293
 294 extern edge create_empty_if_region_on_edge (edge, tree);
 295 extern struct loop *create_empty_loop_on_edge (edge, tree, tree, tree, tree,
 296                                                tree *, tree *, struct loop *);
 297 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 298 extern void duplicate_subloops (struct loop *, struct loop *);
 299 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 300                                            unsigned, sbitmap, edge,
 301                                            VEC (edge, heap) **, int);
 302 extern struct loop *loopify (edge, edge,
 303                              basic_block, edge, edge, bool,
 304                              unsigned, unsigned);
 305 struct loop * loop_version (struct loop *, void *,
 306                             basic_block *, unsigned, unsigned, unsigned, bool);
 307 extern bool remove_path (edge);
 308 void scale_loop_frequencies (struct loop *, int, int);
 309
 310 /* Induction variable analysis.  */
 311
 312 /* The description of induction variable.  The things are a bit complicated
 313    due to need to handle subregs and extends.  The value of the object described
 314    by it can be obtained as follows (all computations are done in extend_mode):
 315
 316    Value in i-th iteration is
 317      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 318
 319    If first_special is true, the value in the first iteration is
 320      delta + mult * base
 321
 322    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 323      subreg_{mode} (base + i * step)
 324
 325    The get_iv_value function can be used to obtain these expressions.
 326
 327    ??? Add a third mode field that would specify the mode in that inner
 328    computation is done, which would enable it to be different from the
 329    outer one?  */
 330
 331 struct rtx_iv
 332 {
 333   /* Its base and step (mode of base and step is supposed to be extend_mode,
 334      see the description above).  */
 335   rtx base, step;
 336
 337   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 338   enum rtx_code extend;
 339
 340   /* Operations applied in the extended mode.  */
 341   rtx delta, mult;
 342
 343   /* The mode it is extended to.  */
 344   enum machine_mode extend_mode;
 345
 346   /* The mode the variable iterates in.  */
 347   enum machine_mode mode;
 348
 349   /* Whether the first iteration needs to be handled specially.  */
 350   unsigned first_special : 1;
 351 };
 352
 353 /* The description of an exit from the loop and of the number of iterations
 354    till we take the exit.  */
 355
 356 struct niter_desc
 357 {
 358   /* The edge out of the loop.  */
 359   edge out_edge;
 360
 361   /* The other edge leading from the condition.  */
 362   edge in_edge;
 363
 364   /* True if we are able to say anything about number of iterations of the
 365      loop.  */
 366   bool simple_p;
 367
 368   /* True if the loop iterates the constant number of times.  */
 369   bool const_iter;
 370
 371   /* Number of iterations if constant.  */
 372   unsigned HOST_WIDEST_INT niter;
 373
 374   /* Upper bound on the number of iterations.  */
 375   unsigned HOST_WIDEST_INT niter_max;
 376
 377   /* Assumptions under that the rest of the information is valid.  */
 378   rtx assumptions;
 379
 380   /* Assumptions under that the loop ends before reaching the latch,
 381      even if value of niter_expr says otherwise.  */
 382   rtx noloop_assumptions;
 383
 384   /* Condition under that the loop is infinite.  */
 385   rtx infinite;
 386
 387   /* Whether the comparison is signed.  */
 388   bool signed_p;
 389
 390   /* The mode in that niter_expr should be computed.  */
 391   enum machine_mode mode;
 392
 393   /* The number of iterations of the loop.  */
 394   rtx niter_expr;
 395 };
 396
 397 extern void iv_analysis_loop_init (struct loop *);
 398 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 399 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 400 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 401 extern rtx get_iv_value (struct rtx_iv *, rtx);
 402 extern bool biv_p (rtx, rtx);
 403 extern void find_simple_exit (struct loop *, struct niter_desc *);
 404 extern void iv_analysis_done (void);
 405
 406 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 407 extern void free_simple_loop_desc (struct loop *loop);
 408
 409 static inline struct niter_desc *
 410 simple_loop_desc (struct loop *loop)
 411 {
 412   return (struct niter_desc *) loop->aux;
 413 }
 414
 415 /* Accessors for the loop structures.  */
 416
 417 /* Returns the loop with index NUM from current_loops.  */
 418
 419 static inline struct loop *
 420 get_loop (unsigned num)
 421 {
 422   return VEC_index (loop_p, current_loops->larray, num);
 423 }
 424
 425 /* Returns the number of superloops of LOOP.  */
 426
 427 static inline unsigned
 428 loop_depth (const struct loop *loop)
 429 {
 430   return VEC_length (loop_p, loop->superloops);
 431 }
 432
 433 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
 434    loop.  */
 435
 436 static inline struct loop *
 437 loop_outer (const struct loop *loop)
 438 {
 439   unsigned n = VEC_length (loop_p, loop->superloops);
 440
 441   if (n == 0)
 442     return NULL;
 443
 444   return VEC_index (loop_p, loop->superloops, n - 1);
 445 }
 446
 447 /* Returns the list of loops in current_loops.  */
 448
 449 static inline VEC (loop_p, gc) *
 450 get_loops (void)
 451 {
 452   if (!current_loops)
 453     return NULL;
 454
 455   return current_loops->larray;
 456 }
 457
 458 /* Returns the number of loops in current_loops (including the removed
 459    ones and the fake loop that forms the root of the loop tree).  */
 460
 461 static inline unsigned
 462 number_of_loops (void)
 463 {
 464   if (!current_loops)
 465     return 0;
 466
 467   return VEC_length (loop_p, current_loops->larray);
 468 }
 469
 470 /* Returns true if state of the loops satisfies all properties
 471    described by FLAGS.  */
 472
 473 static inline bool
 474 loops_state_satisfies_p (unsigned flags)
 475 {
 476   return (current_loops->state & flags) == flags;
 477 }
 478
 479 /* Sets FLAGS to the loops state.  */
 480
 481 static inline void
 482 loops_state_set (unsigned flags)
 483 {
 484   current_loops->state |= flags;
 485 }
 486
 487 /* Clears FLAGS from the loops state.  */
 488
 489 static inline void
 490 loops_state_clear (unsigned flags)
 491 {
 492   if (!current_loops)
 493     return;
 494   current_loops->state &= ~flags;
 495 }
 496
 497 /* Loop iterators.  */
 498
 499 /* Flags for loop iteration.  */
 500
 501 enum li_flags
 502 {
 503   LI_INCLUDE_ROOT = 1,          /* Include the fake root of the loop tree.  */
 504   LI_FROM_INNERMOST = 2,        /* Iterate over the loops in the reverse order,
 505                                    starting from innermost ones.  */
 506   LI_ONLY_INNERMOST = 4         /* Iterate only over innermost loops.  */
 507 };
 508
 509 /* The iterator for loops.  */
 510
 511 typedef struct
 512 {
 513   /* The list of loops to visit.  */
 514   VEC(int,heap) *to_visit;
 515
 516   /* The index of the actual loop.  */
 517   unsigned idx;
 518 } loop_iterator;
 519
 520 static inline void
 521 fel_next (loop_iterator *li, loop_p *loop)
 522 {
 523   int anum;
 524
 525   while (VEC_iterate (int, li->to_visit, li->idx, anum))
 526     {
 527       li->idx++;
 528       *loop = get_loop (anum);
 529       if (*loop)
 530         return;
 531     }
 532
 533   VEC_free (int, heap, li->to_visit);
 534   *loop = NULL;
 535 }
 536
 537 static inline void
 538 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
 539 {
 540   struct loop *aloop;
 541   unsigned i;
 542   int mn;
 543
 544   li->idx = 0;
 545   if (!current_loops)
 546     {
 547       li->to_visit = NULL;
 548       *loop = NULL;
 549       return;
 550     }
 551
 552   li->to_visit = VEC_alloc (int, heap, number_of_loops ());
 553   mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
 554
 555   if (flags & LI_ONLY_INNERMOST)
 556     {
 557       for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
 558         if (aloop != NULL
 559             && aloop->inner == NULL
 560             && aloop->num >= mn)
 561           VEC_quick_push (int, li->to_visit, aloop->num);
 562     }
 563   else if (flags & LI_FROM_INNERMOST)
 564     {
 565       /* Push the loops to LI->TO_VISIT in postorder.  */
 566       for (aloop = current_loops->tree_root;
 567            aloop->inner != NULL;
 568            aloop = aloop->inner)
 569         continue;
 570
 571       while (1)
 572         {
 573           if (aloop->num >= mn)
 574             VEC_quick_push (int, li->to_visit, aloop->num);
 575
 576           if (aloop->next)
 577             {
 578               for (aloop = aloop->next;
 579                    aloop->inner != NULL;
 580                    aloop = aloop->inner)
 581                 continue;
 582             }
 583           else if (!loop_outer (aloop))
 584             break;
 585           else
 586             aloop = loop_outer (aloop);
 587         }
 588     }
 589   else
 590     {
 591       /* Push the loops to LI->TO_VISIT in preorder.  */
 592       aloop = current_loops->tree_root;
 593       while (1)
 594         {
 595           if (aloop->num >= mn)
 596             VEC_quick_push (int, li->to_visit, aloop->num);
 597
 598           if (aloop->inner != NULL)
 599             aloop = aloop->inner;
 600           else
 601             {
 602               while (aloop != NULL && aloop->next == NULL)
 603                 aloop = loop_outer (aloop);
 604               if (aloop == NULL)
 605                 break;
 606               aloop = aloop->next;
 607             }
 608         }
 609     }
 610
 611   fel_next (li, loop);
 612 }
 613
 614 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
 615   for (fel_init (&(LI), &(LOOP), FLAGS); \
 616        (LOOP); \
 617        fel_next (&(LI), &(LOOP)))
 618
 619 #define FOR_EACH_LOOP_BREAK(LI) \
 620   { \
 621     VEC_free (int, heap, (LI)->to_visit); \
 622     break; \
 623   }
 624
 625 /* The properties of the target.  */
 626
 627 extern unsigned target_avail_regs;
 628 extern unsigned target_res_regs;
 629 extern unsigned target_reg_cost [2];
 630 extern unsigned target_spill_cost [2];
 631
 632 /* Register pressure estimation for induction variable optimizations & loop
 633    invariant motion.  */
 634 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool);
 635 extern void init_set_costs (void);
 636
 637 /* Loop optimizer initialization.  */
 638 extern void loop_optimizer_init (unsigned);
 639 extern void loop_optimizer_finalize (void);
 640
 641 /* Optimization passes.  */
 642 extern void unswitch_loops (void);
 643
 644 enum
 645 {
 646   UAP_PEEL = 1,         /* Enables loop peeling.  */
 647   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 648   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 649 };
 650
 651 extern void unroll_and_peel_loops (int);
 652 extern void doloop_optimize_loops (void);
 653 extern void move_loop_invariants (void);
 654 extern bool finite_loop_p (struct loop *);
 655
 656 #endif /* GCC_CFGLOOP_H */