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