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 /* 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 GTY (()) lpt_decision {
  42   enum lpt_dec decision;
  43   unsigned times;
  44 };
  45
  46 /* The structure describing a bound on number of iterations of a loop.  */
  47
  48 struct GTY ((chain_next ("%h.next"))) nb_iter_bound {
  49   /* The statement STMT is executed at most ...  */
  50   gimple stmt;
  51
  52   /* ... BOUND + 1 times (BOUND must be an unsigned constant).
  53      The + 1 is added for the following reasons:
  54
  55      a) 0 would otherwise be unused, while we would need to care more about
  56         overflows (as MAX + 1 is sometimes produced as the estimate on number
  57         of executions of STMT).
  58      b) it is consistent with the result of number_of_iterations_exit.  */
  59   double_int bound;
  60
  61   /* True if the statement will cause the loop to be leaved the (at most)
  62      BOUND + 1-st time it is executed, that is, all the statements after it
  63      are executed at most BOUND times.  */
  64   bool is_exit;
  65
  66   /* The next bound in the list.  */
  67   struct nb_iter_bound *next;
  68 };
  69
  70 /* Description of the loop exit.  */
  71
  72 struct GTY (()) loop_exit {
  73   /* The exit edge.  */
  74   struct edge_def *e;
  75
  76   /* Previous and next exit in the list of the exits of the loop.  */
  77   struct loop_exit *prev;
  78   struct loop_exit *next;
  79
  80   /* Next element in the list of loops from that E exits.  */
  81   struct loop_exit *next_e;
  82 };
  83
  84 typedef struct loop *loop_p;
  85 DEF_VEC_P (loop_p);
  86 DEF_VEC_ALLOC_P (loop_p, heap);
  87 DEF_VEC_ALLOC_P (loop_p, gc);
  88
  89 /* An integer estimation of the number of iterations.  Estimate_state
  90    describes what is the state of the estimation.  */
  91 enum loop_estimation
  92 {
  93   /* Estimate was not computed yet.  */
  94   EST_NOT_COMPUTED,
  95   /* Estimate is ready.  */
  96   EST_AVAILABLE
  97 };
  98
  99 /* Structure to hold information for each natural loop.  */
 100 struct GTY ((chain_next ("%h.next"))) loop {
 101   /* Index into loops array.  */
 102   int num;
 103
 104   /* Number of loop insns.  */
 105   unsigned ninsns;
 106
 107   /* Basic block of loop header.  */
 108   struct basic_block_def *header;
 109
 110   /* Basic block of loop latch.  */
 111   struct basic_block_def *latch;
 112
 113   /* For loop unrolling/peeling decision.  */
 114   struct lpt_decision lpt_decision;
 115
 116   /* Average number of executed insns per iteration.  */
 117   unsigned av_ninsns;
 118
 119   /* Number of blocks contained within the loop.  */
 120   unsigned num_nodes;
 121
 122   /* Superloops of the loop, starting with the outermost loop.  */
 123   VEC (loop_p, gc) *superloops;
 124
 125   /* The first inner (child) loop or NULL if innermost loop.  */
 126   struct loop *inner;
 127
 128   /* Link to the next (sibling) loop.  */
 129   struct loop *next;
 130
 131   /* Auxiliary info specific to a pass.  */
 132   PTR GTY ((skip (""))) aux;
 133
 134   /* The number of times the latch of the loop is executed.
 135      This is an INTEGER_CST or an expression containing symbolic
 136      names.  Don't access this field directly:
 137      number_of_latch_executions computes and caches the computed
 138      information in this field.  */
 139   tree nb_iterations;
 140
 141   /* An integer guaranteed to bound the number of iterations of the loop
 142      from above.  */
 143   double_int nb_iterations_upper_bound;
 144
 145   /* An integer giving the expected number of iterations of the loop.  */
 146   double_int nb_iterations_estimate;
 147
 148   bool any_upper_bound;
 149   bool any_estimate;
 150
 151   /* An integer estimation of the number of iterations.  Estimate_state
 152      describes what is the state of the estimation.  */
 153   enum loop_estimation estimate_state;
 154
 155   /* Upper bound on number of iterations of a loop.  */
 156   struct nb_iter_bound *bounds;
 157
 158   /* Head of the cyclic list of the exits of the loop.  */
 159   struct loop_exit *exits;
 160
 161   /* True if the loop can be parallel.  */
 162   bool can_be_parallel;
 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 GTY (()) loops {
 184   /* State of loops.  */
 185   int state;
 186
 187   /* Array of the loops.  */
 188   VEC (loop_p, gc) *larray;
 189
 190   /* Maps edges to the list of their descriptions as loop exits.  Edges
 191      whose sources or destinations have loop_father == NULL (which may
 192      happen during the cfg manipulations) should not appear in EXITS.  */
 193   htab_t GTY((param_is (struct loop_exit))) exits;
 194
 195   /* Pointer to root of loop hierarchy tree.  */
 196   struct loop *tree_root;
 197 };
 198
 199 /* Loop recognition.  */
 200 extern int flow_loops_find (struct loops *);
 201 extern void disambiguate_loops_with_multiple_latches (void);
 202 extern void flow_loops_free (struct loops *);
 203 extern void flow_loops_dump (FILE *,
 204                              void (*)(const struct loop *, FILE *, int), int);
 205 extern void flow_loop_dump (const struct loop *, FILE *,
 206                             void (*)(const struct loop *, FILE *, int), int);
 207 struct loop *alloc_loop (void);
 208 extern void flow_loop_free (struct loop *);
 209 int flow_loop_nodes_find (basic_block, struct loop *);
 210 void fix_loop_structure (bitmap changed_bbs);
 211 bool mark_irreducible_loops (void);
 212 void release_recorded_exits (void);
 213 void record_loop_exits (void);
 214 void rescan_loop_exit (edge, bool, bool);
 215
 216 /* Loop data structure manipulation/querying.  */
 217 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 218 extern void flow_loop_tree_node_remove (struct loop *);
 219 extern void add_loop (struct loop *, struct loop *);
 220 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 221 extern bool flow_bb_inside_loop_p (const struct loop *, const_basic_block);
 222 extern struct loop * find_common_loop (struct loop *, struct loop *);
 223 struct loop *superloop_at_depth (struct loop *, unsigned);
 224 struct eni_weights_d;
 225 extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *);
 226 extern int num_loop_insns (const struct loop *);
 227 extern int average_num_loop_insns (const struct loop *);
 228 extern unsigned get_loop_level (const struct loop *);
 229 extern bool loop_exit_edge_p (const struct loop *, const_edge);
 230 extern bool is_loop_exit (struct loop *, basic_block);
 231 extern void mark_loop_exit_edges (void);
 232
 233 /* Loops & cfg manipulation.  */
 234 extern basic_block *get_loop_body (const struct loop *);
 235 extern unsigned get_loop_body_with_size (const struct loop *, basic_block *,
 236                                          unsigned);
 237 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 238 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 239 extern basic_block *get_loop_body_in_custom_order (const struct loop *,
 240                                int (*) (const void *, const void *));
 241
 242 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
 243 edge single_exit (const struct loop *);
 244 extern unsigned num_loop_branches (const struct loop *);
 245
 246 extern edge loop_preheader_edge (const struct loop *);
 247 extern edge loop_latch_edge (const struct loop *);
 248
 249 extern void add_bb_to_loop (basic_block, struct loop *);
 250 extern void remove_bb_from_loops (basic_block);
 251
 252 extern void cancel_loop_tree (struct loop *);
 253 extern void delete_loop (struct loop *);
 254
 255 enum
 256 {
 257   CP_SIMPLE_PREHEADERS = 1,
 258   CP_FALLTHRU_PREHEADERS = 2
 259 };
 260
 261 basic_block create_preheader (struct loop *, int);
 262 extern void create_preheaders (int);
 263 extern void force_single_succ_latches (void);
 264
 265 extern void verify_loop_structure (void);
 266
 267 /* Loop analysis.  */
 268 extern bool just_once_each_iteration_p (const struct loop *, const_basic_block);
 269 gcov_type expected_loop_iterations_unbounded (const struct loop *);
 270 extern unsigned expected_loop_iterations (const struct loop *);
 271 extern rtx doloop_condition_get (rtx);
 272
 273 void estimate_numbers_of_iterations_loop (struct loop *);
 274 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool);
 275 bool estimated_loop_iterations (struct loop *, bool, double_int *);
 276
 277 /* Loop manipulation.  */
 278 extern bool can_duplicate_loop_p (const struct loop *loop);
 279
 280 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 281                                            duplicate_loop_to_header_edge.  */
 282 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 283                                            field of newly create BB.  */
 284 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 285                                            a complete peeling.  */
 286
 287 extern edge create_empty_if_region_on_edge (edge, tree);
 288 extern struct loop *create_empty_loop_on_edge (edge, tree, tree, tree, tree,
 289                                                tree *, tree *, struct loop *);
 290 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 291 extern void duplicate_subloops (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 extern bool finite_loop_p (struct loop *);
 648
 649 #endif /* GCC_CFGLOOP_H */