gcc/cfgloop.h

   1 /* Natural loop functions
   2    Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
   3    2005, 2006, 2007  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 /* Structure to hold decision about unrolling/peeling.  */
  31 enum lpt_dec
  32 {
  33   LPT_NONE,
  34   LPT_PEEL_COMPLETELY,
  35   LPT_PEEL_SIMPLE,
  36   LPT_UNROLL_CONSTANT,
  37   LPT_UNROLL_RUNTIME,
  38   LPT_UNROLL_STUPID
  39 };
  40
  41 struct lpt_decision GTY (())
  42 {
  43   enum lpt_dec decision;
  44   unsigned times;
  45 };
  46
  47 /* The structure describing a bound on number of iterations of a loop.  */
  48
  49 struct nb_iter_bound GTY ((chain_next ("%h.next")))
  50 {
  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   double_int bound;
  62
  63   /* True if the statement will cause the loop to be leaved the (at most)
  64      BOUND + 1-st time it is executed, that is, all the statements after it
  65      are executed at most BOUND times.  */
  66   bool is_exit;
  67
  68   /* The next bound in the list.  */
  69   struct nb_iter_bound *next;
  70 };
  71
  72 /* Description of the loop exit.  */
  73
  74 struct loop_exit GTY (())
  75 {
  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 loop GTY ((chain_next ("%h.next")))
 104 {
 105   /* Index into loops array.  */
 106   int num;
 107
 108   /* Basic block of loop header.  */
 109   struct basic_block_def *header;
 110
 111   /* Basic block of loop latch.  */
 112   struct basic_block_def *latch;
 113
 114   /* For loop unrolling/peeling decision.  */
 115   struct lpt_decision lpt_decision;
 116
 117   /* Number of loop insns.  */
 118   unsigned ninsns;
 119
 120   /* Average number of executed insns per iteration.  */
 121   unsigned av_ninsns;
 122
 123   /* Number of blocks contained within the loop.  */
 124   unsigned num_nodes;
 125
 126   /* Superloops of the loop, starting with the outermost loop.  */
 127   VEC (loop_p, gc) *superloops;
 128
 129   /* The first inner (child) loop or NULL if innermost loop.  */
 130   struct loop *inner;
 131
 132   /* Link to the next (sibling) loop.  */
 133   struct loop *next;
 134
 135   /* Auxiliary info specific to a pass.  */
 136   PTR GTY ((skip (""))) aux;
 137
 138   /* The number of times the latch of the loop is executed.
 139      This is an INTEGER_CST or an expression containing symbolic
 140      names.  Don't access this field directly:
 141      number_of_latch_executions computes and caches the computed
 142      information in this field.  */
 143   tree nb_iterations;
 144
 145   /* An integer estimation of the number of iterations.  Estimate_state
 146      describes what is the state of the estimation.  */
 147   enum loop_estimation estimate_state;
 148
 149   /* An integer guaranteed to bound the number of iterations of the loop
 150      from above.  */
 151   bool any_upper_bound;
 152   double_int nb_iterations_upper_bound;
 153
 154   /* An integer giving the expected number of iterations of the loop.  */
 155   bool any_estimate;
 156   double_int nb_iterations_estimate;
 157
 158   /* Upper bound on number of iterations of a loop.  */
 159   struct nb_iter_bound *bounds;
 160
 161   /* Head of the cyclic list of the exits of the loop.  */
 162   struct loop_exit *exits;
 163 };
 164
 165 /* Flags for state of loop structure.  */
 166 enum
 167 {
 168   LOOPS_HAVE_PREHEADERS = 1,
 169   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 170   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
 171   LOOPS_HAVE_RECORDED_EXITS = 8,
 172   LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16,
 173   LOOP_CLOSED_SSA = 32,
 174   LOOPS_NEED_FIXUP = 64,
 175   LOOPS_HAVE_FALLTHRU_PREHEADERS = 128
 176 };
 177
 178 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 179                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 180 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
 181
 182 /* Structure to hold CFG information about natural loops within a function.  */
 183 struct loops GTY (())
 184 {
 185   /* State of loops.  */
 186   int state;
 187
 188   /* Array of the loops.  */
 189   VEC (loop_p, gc) *larray;
 190
 191   /* Maps edges to the list of their descriptions as loop exits.  Edges
 192      whose sources or destinations have loop_father == NULL (which may
 193      happen during the cfg manipulations) should not appear in EXITS.  */
 194   htab_t GTY((param_is (struct loop_exit))) exits;
 195
 196   /* Pointer to root of loop hierarchy tree.  */
 197   struct loop *tree_root;
 198 };
 199
 200 /* Loop recognition.  */
 201 extern int flow_loops_find (struct loops *);
 202 extern void disambiguate_loops_with_multiple_latches (void);
 203 extern void flow_loops_free (struct loops *);
 204 extern void flow_loops_dump (FILE *,
 205                              void (*)(const struct loop *, FILE *, int), int);
 206 extern void flow_loop_dump (const struct loop *, FILE *,
 207                             void (*)(const struct loop *, FILE *, int), int);
 208 struct loop *alloc_loop (void);
 209 extern void flow_loop_free (struct loop *);
 210 int flow_loop_nodes_find (basic_block, struct loop *);
 211 void fix_loop_structure (bitmap changed_bbs);
 212 void mark_irreducible_loops (void);
 213 void release_recorded_exits (void);
 214 void record_loop_exits (void);
 215 void rescan_loop_exit (edge, bool, bool);
 216
 217 /* Loop data structure manipulation/querying.  */
 218 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 219 extern void flow_loop_tree_node_remove (struct loop *);
 220 extern void add_loop (struct loop *, struct loop *);
 221 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 222 extern bool flow_bb_inside_loop_p (const struct loop *, const_basic_block);
 223 extern struct loop * find_common_loop (struct loop *, struct loop *);
 224 struct loop *superloop_at_depth (struct loop *, unsigned);
 225 struct eni_weights_d;
 226 extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *);
 227 extern int num_loop_insns (const struct loop *);
 228 extern int average_num_loop_insns (const struct loop *);
 229 extern unsigned get_loop_level (const struct loop *);
 230 extern bool loop_exit_edge_p (const struct loop *, const_edge);
 231 extern bool is_loop_exit (struct loop *, basic_block);
 232 extern void mark_loop_exit_edges (void);
 233
 234 /* Loops & cfg manipulation.  */
 235 extern basic_block *get_loop_body (const struct loop *);
 236 extern unsigned get_loop_body_with_size (const struct loop *, basic_block *,
 237                                          unsigned);
 238 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 239 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 240 extern basic_block *get_loop_body_in_custom_order (const struct loop *,
 241                                int (*) (const void *, const void *));
 242
 243 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
 244 edge single_exit (const struct loop *);
 245 extern unsigned num_loop_branches (const struct loop *);
 246
 247 extern edge loop_preheader_edge (const struct loop *);
 248 extern edge loop_latch_edge (const struct loop *);
 249
 250 extern void add_bb_to_loop (basic_block, struct loop *);
 251 extern void remove_bb_from_loops (basic_block);
 252
 253 extern void cancel_loop_tree (struct loop *);
 254 extern void delete_loop (struct loop *);
 255
 256 enum
 257 {
 258   CP_SIMPLE_PREHEADERS = 1,
 259   CP_FALLTHRU_PREHEADERS = 2
 260 };
 261
 262 basic_block create_preheader (struct loop *, int);
 263 extern void create_preheaders (int);
 264 extern void force_single_succ_latches (void);
 265
 266 extern void verify_loop_structure (void);
 267
 268 /* Loop analysis.  */
 269 extern bool just_once_each_iteration_p (const struct loop *, const_basic_block);
 270 gcov_type expected_loop_iterations_unbounded (const struct loop *);
 271 extern unsigned expected_loop_iterations (const struct loop *);
 272 extern rtx doloop_condition_get (rtx);
 273
 274 void estimate_numbers_of_iterations_loop (struct loop *);
 275 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool);
 276 bool estimated_loop_iterations (struct loop *, bool, double_int *);
 277
 278 /* Loop manipulation.  */
 279 extern bool can_duplicate_loop_p (const struct loop *loop);
 280
 281 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 282                                            duplicate_loop_to_header_edge.  */
 283 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 284                                            field of newly create BB.  */
 285 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 286                                            a complete peeling.  */
 287
 288 extern edge create_empty_if_region_on_edge (edge, tree);
 289 extern struct loop *create_empty_loop_on_edge (edge, tree, tree, tree, tree,
 290                                                tree *, struct loop *);
 291 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 292 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 293                                            unsigned, sbitmap, edge,
 294                                            VEC (edge, heap) **, int);
 295 extern struct loop *loopify (edge, edge,
 296                              basic_block, edge, edge, bool,
 297                              unsigned, unsigned);
 298 struct loop * loop_version (struct loop *, void *,
 299                             basic_block *, unsigned, unsigned, unsigned, bool);
 300 extern bool remove_path (edge);
 301 void scale_loop_frequencies (struct loop *, int, int);
 302
 303 /* Induction variable analysis.  */
 304
 305 /* The description of induction variable.  The things are a bit complicated
 306    due to need to handle subregs and extends.  The value of the object described
 307    by it can be obtained as follows (all computations are done in extend_mode):
 308
 309    Value in i-th iteration is
 310      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 311
 312    If first_special is true, the value in the first iteration is
 313      delta + mult * base
 314
 315    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 316      subreg_{mode} (base + i * step)
 317
 318    The get_iv_value function can be used to obtain these expressions.
 319
 320    ??? Add a third mode field that would specify the mode in that inner
 321    computation is done, which would enable it to be different from the
 322    outer one?  */
 323
 324 struct rtx_iv
 325 {
 326   /* Its base and step (mode of base and step is supposed to be extend_mode,
 327      see the description above).  */
 328   rtx base, step;
 329
 330   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 331   enum rtx_code extend;
 332
 333   /* Operations applied in the extended mode.  */
 334   rtx delta, mult;
 335
 336   /* The mode it is extended to.  */
 337   enum machine_mode extend_mode;
 338
 339   /* The mode the variable iterates in.  */
 340   enum machine_mode mode;
 341
 342   /* Whether the first iteration needs to be handled specially.  */
 343   unsigned first_special : 1;
 344 };
 345
 346 /* The description of an exit from the loop and of the number of iterations
 347    till we take the exit.  */
 348
 349 struct niter_desc
 350 {
 351   /* The edge out of the loop.  */
 352   edge out_edge;
 353
 354   /* The other edge leading from the condition.  */
 355   edge in_edge;
 356
 357   /* True if we are able to say anything about number of iterations of the
 358      loop.  */
 359   bool simple_p;
 360
 361   /* True if the loop iterates the constant number of times.  */
 362   bool const_iter;
 363
 364   /* Number of iterations if constant.  */
 365   unsigned HOST_WIDEST_INT niter;
 366
 367   /* Upper bound on the number of iterations.  */
 368   unsigned HOST_WIDEST_INT niter_max;
 369
 370   /* Assumptions under that the rest of the information is valid.  */
 371   rtx assumptions;
 372
 373   /* Assumptions under that the loop ends before reaching the latch,
 374      even if value of niter_expr says otherwise.  */
 375   rtx noloop_assumptions;
 376
 377   /* Condition under that the loop is infinite.  */
 378   rtx infinite;
 379
 380   /* Whether the comparison is signed.  */
 381   bool signed_p;
 382
 383   /* The mode in that niter_expr should be computed.  */
 384   enum machine_mode mode;
 385
 386   /* The number of iterations of the loop.  */
 387   rtx niter_expr;
 388 };
 389
 390 extern void iv_analysis_loop_init (struct loop *);
 391 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 392 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 393 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 394 extern rtx get_iv_value (struct rtx_iv *, rtx);
 395 extern bool biv_p (rtx, rtx);
 396 extern void find_simple_exit (struct loop *, struct niter_desc *);
 397 extern void iv_analysis_done (void);
 398
 399 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 400 extern void free_simple_loop_desc (struct loop *loop);
 401
 402 static inline struct niter_desc *
 403 simple_loop_desc (struct loop *loop)
 404 {
 405   return (struct niter_desc *) loop->aux;
 406 }
 407
 408 /* Accessors for the loop structures.  */
 409
 410 /* Returns the loop with index NUM from current_loops.  */
 411
 412 static inline struct loop *
 413 get_loop (unsigned num)
 414 {
 415   return VEC_index (loop_p, current_loops->larray, num);
 416 }
 417
 418 /* Returns the number of superloops of LOOP.  */
 419
 420 static inline unsigned
 421 loop_depth (const struct loop *loop)
 422 {
 423   return VEC_length (loop_p, loop->superloops);
 424 }
 425
 426 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
 427    loop.  */
 428
 429 static inline struct loop *
 430 loop_outer (const struct loop *loop)
 431 {
 432   unsigned n = VEC_length (loop_p, loop->superloops);
 433
 434   if (n == 0)
 435     return NULL;
 436
 437   return VEC_index (loop_p, loop->superloops, n - 1);
 438 }
 439
 440 /* Returns the list of loops in current_loops.  */
 441
 442 static inline VEC (loop_p, gc) *
 443 get_loops (void)
 444 {
 445   if (!current_loops)
 446     return NULL;
 447
 448   return current_loops->larray;
 449 }
 450
 451 /* Returns the number of loops in current_loops (including the removed
 452    ones and the fake loop that forms the root of the loop tree).  */
 453
 454 static inline unsigned
 455 number_of_loops (void)
 456 {
 457   if (!current_loops)
 458     return 0;
 459
 460   return VEC_length (loop_p, current_loops->larray);
 461 }
 462
 463 /* Returns true if state of the loops satisfies all properties
 464    described by FLAGS.  */
 465
 466 static inline bool
 467 loops_state_satisfies_p (unsigned flags)
 468 {
 469   return (current_loops->state & flags) == flags;
 470 }
 471
 472 /* Sets FLAGS to the loops state.  */
 473
 474 static inline void
 475 loops_state_set (unsigned flags)
 476 {
 477   current_loops->state |= flags;
 478 }
 479
 480 /* Clears FLAGS from the loops state.  */
 481
 482 static inline void
 483 loops_state_clear (unsigned flags)
 484 {
 485   if (!current_loops)
 486     return;
 487   current_loops->state &= ~flags;
 488 }
 489
 490 /* Loop iterators.  */
 491
 492 /* Flags for loop iteration.  */
 493
 494 enum li_flags
 495 {
 496   LI_INCLUDE_ROOT = 1,          /* Include the fake root of the loop tree.  */
 497   LI_FROM_INNERMOST = 2,        /* Iterate over the loops in the reverse order,
 498                                    starting from innermost ones.  */
 499   LI_ONLY_INNERMOST = 4         /* Iterate only over innermost loops.  */
 500 };
 501
 502 /* The iterator for loops.  */
 503
 504 typedef struct
 505 {
 506   /* The list of loops to visit.  */
 507   VEC(int,heap) *to_visit;
 508
 509   /* The index of the actual loop.  */
 510   unsigned idx;
 511 } loop_iterator;
 512
 513 static inline void
 514 fel_next (loop_iterator *li, loop_p *loop)
 515 {
 516   int anum;
 517
 518   while (VEC_iterate (int, li->to_visit, li->idx, anum))
 519     {
 520       li->idx++;
 521       *loop = get_loop (anum);
 522       if (*loop)
 523         return;
 524     }
 525
 526   VEC_free (int, heap, li->to_visit);
 527   *loop = NULL;
 528 }
 529
 530 static inline void
 531 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
 532 {
 533   struct loop *aloop;
 534   unsigned i;
 535   int mn;
 536
 537   li->idx = 0;
 538   if (!current_loops)
 539     {
 540       li->to_visit = NULL;
 541       *loop = NULL;
 542       return;
 543     }
 544
 545   li->to_visit = VEC_alloc (int, heap, number_of_loops ());
 546   mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
 547
 548   if (flags & LI_ONLY_INNERMOST)
 549     {
 550       for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
 551         if (aloop != NULL
 552             && aloop->inner == NULL
 553             && aloop->num >= mn)
 554           VEC_quick_push (int, li->to_visit, aloop->num);
 555     }
 556   else if (flags & LI_FROM_INNERMOST)
 557     {
 558       /* Push the loops to LI->TO_VISIT in postorder.  */
 559       for (aloop = current_loops->tree_root;
 560            aloop->inner != NULL;
 561            aloop = aloop->inner)
 562         continue;
 563
 564       while (1)
 565         {
 566           if (aloop->num >= mn)
 567             VEC_quick_push (int, li->to_visit, aloop->num);
 568
 569           if (aloop->next)
 570             {
 571               for (aloop = aloop->next;
 572                    aloop->inner != NULL;
 573                    aloop = aloop->inner)
 574                 continue;
 575             }
 576           else if (!loop_outer (aloop))
 577             break;
 578           else
 579             aloop = loop_outer (aloop);
 580         }
 581     }
 582   else
 583     {
 584       /* Push the loops to LI->TO_VISIT in preorder.  */
 585       aloop = current_loops->tree_root;
 586       while (1)
 587         {
 588           if (aloop->num >= mn)
 589             VEC_quick_push (int, li->to_visit, aloop->num);
 590
 591           if (aloop->inner != NULL)
 592             aloop = aloop->inner;
 593           else
 594             {
 595               while (aloop != NULL && aloop->next == NULL)
 596                 aloop = loop_outer (aloop);
 597               if (aloop == NULL)
 598                 break;
 599               aloop = aloop->next;
 600             }
 601         }
 602     }
 603
 604   fel_next (li, loop);
 605 }
 606
 607 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
 608   for (fel_init (&(LI), &(LOOP), FLAGS); \
 609        (LOOP); \
 610        fel_next (&(LI), &(LOOP)))
 611
 612 #define FOR_EACH_LOOP_BREAK(LI) \
 613   { \
 614     VEC_free (int, heap, (LI)->to_visit); \
 615     break; \
 616   }
 617
 618 /* The properties of the target.  */
 619
 620 extern unsigned target_avail_regs;
 621 extern unsigned target_res_regs;
 622 extern unsigned target_reg_cost [2];
 623 extern unsigned target_spill_cost [2];
 624
 625 /* Register pressure estimation for induction variable optimizations & loop
 626    invariant motion.  */
 627 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool);
 628 extern void init_set_costs (void);
 629
 630 /* Loop optimizer initialization.  */
 631 extern void loop_optimizer_init (unsigned);
 632 extern void loop_optimizer_finalize (void);
 633
 634 /* Optimization passes.  */
 635 extern void unswitch_loops (void);
 636
 637 enum
 638 {
 639   UAP_PEEL = 1,         /* Enables loop peeling.  */
 640   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 641   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 642 };
 643
 644 extern void unroll_and_peel_loops (int);
 645 extern void doloop_optimize_loops (void);
 646 extern void move_loop_invariants (void);
 647
 648 #endif /* GCC_CFGLOOP_H */