gcc/cfgloop.h

   1 /* Natural loop functions
   2    Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
   3    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 2, 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 COPYING.  If not, write to the Free
  19 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  20 02110-1301, USA.  */
  21
  22 #ifndef GCC_CFGLOOP_H
  23 #define GCC_CFGLOOP_H
  24
  25 #include "basic-block.h"
  26 /* For rtx_code.  */
  27 #include "rtl.h"
  28 #include "vecprim.h"
  29 #include "double-int.h"
  30
  31 /* Structure to hold decision about unrolling/peeling.  */
  32 enum lpt_dec
  33 {
  34   LPT_NONE,
  35   LPT_PEEL_COMPLETELY,
  36   LPT_PEEL_SIMPLE,
  37   LPT_UNROLL_CONSTANT,
  38   LPT_UNROLL_RUNTIME,
  39   LPT_UNROLL_STUPID
  40 };
  41
  42 struct lpt_decision
  43 {
  44   enum lpt_dec decision;
  45   unsigned times;
  46 };
  47
  48 /* The structure describing a bound on number of iterations of a loop.  */
  49
  50 struct nb_iter_bound
  51 {
  52   /* The statement STMT is executed at most ...  */
  53   tree 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 loop_exit
  76 {
  77   /* The exit edge.  */
  78   edge e;
  79
  80   /* Previous and next exit in the list of the exits of the loop.  */
  81   struct loop_exit *prev;
  82   struct loop_exit *next;
  83
  84   /* Next element in the list of loops from that E exits.  */
  85   struct loop_exit *next_e;
  86 };
  87
  88 typedef struct loop *loop_p;
  89 DEF_VEC_P (loop_p);
  90 DEF_VEC_ALLOC_P (loop_p, heap);
  91
  92 /* Structure to hold information for each natural loop.  */
  93 struct loop
  94 {
  95   /* Index into loops array.  */
  96   int num;
  97
  98   /* Basic block of loop header.  */
  99   basic_block header;
 100
 101   /* Basic block of loop latch.  */
 102   basic_block latch;
 103
 104   /* For loop unrolling/peeling decision.  */
 105   struct lpt_decision lpt_decision;
 106
 107   /* Number of loop insns.  */
 108   unsigned ninsns;
 109
 110   /* Average number of executed insns per iteration.  */
 111   unsigned av_ninsns;
 112
 113   /* Number of blocks contained within the loop.  */
 114   unsigned num_nodes;
 115
 116   /* Superloops of the loop, starting with the outermost loop.  */
 117   VEC (loop_p, heap) *superloops;
 118
 119   /* The first inner (child) loop or NULL if innermost loop.  */
 120   struct loop *inner;
 121
 122   /* Link to the next (sibling) loop.  */
 123   struct loop *next;
 124
 125   /* Loop that is copy of this loop.  */
 126   struct loop *copy;
 127
 128   /* Auxiliary info specific to a pass.  */
 129   void *aux;
 130
 131   /* The number of times the latch of the loop is executed.
 132      This is an INTEGER_CST or an expression containing symbolic
 133      names.  Don't access this field directly:
 134      number_of_latch_executions computes and caches the computed
 135      information in this field.  */
 136   tree nb_iterations;
 137
 138   /* An integer estimation of the number of iterations.  Estimate_state
 139      describes what is the state of the estimation.  */
 140   enum
 141     {
 142       /* Estimate was not computed yet.  */
 143       EST_NOT_COMPUTED,
 144       /* Estimate is ready.  */
 145       EST_AVAILABLE
 146     } estimate_state;
 147
 148   /* An integer guaranteed to bound the number of iterations of the loop
 149      from above.  */
 150   bool any_upper_bound;
 151   double_int nb_iterations_upper_bound;
 152
 153   /* An integer giving the expected number of iterations of the loop.  */
 154   bool any_estimate;
 155   double_int nb_iterations_estimate;
 156
 157   /* Upper bound on number of iterations of a loop.  */
 158   struct nb_iter_bound *bounds;
 159
 160   /* Head of the cyclic list of the exits of the loop.  */
 161   struct loop_exit exits;
 162 };
 163
 164 /* Flags for state of loop structure.  */
 165 enum
 166 {
 167   LOOPS_HAVE_PREHEADERS = 1,
 168   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 169   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
 170   LOOPS_HAVE_RECORDED_EXITS = 8,
 171   LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16,
 172   LOOP_CLOSED_SSA = 32
 173 };
 174
 175 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 176                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 177 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
 178
 179 /* Structure to hold CFG information about natural loops within a function.  */
 180 struct loops
 181 {
 182   /* State of loops.  */
 183   int state;
 184
 185   /* Array of the loops.  */
 186   VEC (loop_p, heap) *larray;
 187
 188   /* Maps edges to the list of their descriptions as loop exits.  Edges
 189      whose sources or destinations have loop_father == NULL (which may
 190      happen during the cfg manipulations) should not appear in EXITS.  */
 191   htab_t exits;
 192
 193   /* Pointer to root of loop hierarchy tree.  */
 194   struct loop *tree_root;
 195 };
 196
 197 /* Loop recognition.  */
 198 extern int flow_loops_find (struct loops *);
 199 extern void disambiguate_loops_with_multiple_latches (void);
 200 extern void flow_loops_free (struct loops *);
 201 extern void flow_loops_dump (FILE *,
 202                              void (*)(const struct loop *, FILE *, int), int);
 203 extern void flow_loop_dump (const struct loop *, FILE *,
 204                             void (*)(const struct loop *, FILE *, int), int);
 205 struct loop *alloc_loop (void);
 206 extern void flow_loop_free (struct loop *);
 207 int flow_loop_nodes_find (basic_block, struct loop *);
 208 void fix_loop_structure (bitmap changed_bbs);
 209 void mark_irreducible_loops (void);
 210 void release_recorded_exits (void);
 211 void record_loop_exits (void);
 212 void rescan_loop_exit (edge, bool, bool);
 213
 214 /* Loop data structure manipulation/querying.  */
 215 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 216 extern void flow_loop_tree_node_remove (struct loop *);
 217 extern void add_loop (struct loop *, struct loop *);
 218 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 219 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
 220 extern struct loop * find_common_loop (struct loop *, struct loop *);
 221 struct loop *superloop_at_depth (struct loop *, unsigned);
 222 struct eni_weights_d;
 223 extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *);
 224 extern int num_loop_insns (struct loop *);
 225 extern int average_num_loop_insns (struct loop *);
 226 extern unsigned get_loop_level (const struct loop *);
 227 extern bool loop_exit_edge_p (const struct loop *, edge);
 228 extern void mark_loop_exit_edges (void);
 229
 230 /* Loops & cfg manipulation.  */
 231 extern basic_block *get_loop_body (const struct loop *);
 232 extern unsigned get_loop_body_with_size (const struct loop *, basic_block *,
 233                                          unsigned);
 234 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 235 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 236 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
 237 edge single_exit (const struct loop *);
 238 extern unsigned num_loop_branches (const struct loop *);
 239
 240 extern edge loop_preheader_edge (const struct loop *);
 241 extern edge loop_latch_edge (const struct loop *);
 242
 243 extern void add_bb_to_loop (basic_block, struct loop *);
 244 extern void remove_bb_from_loops (basic_block);
 245
 246 extern void cancel_loop_tree (struct loop *);
 247 extern void delete_loop (struct loop *);
 248
 249 enum
 250 {
 251   CP_SIMPLE_PREHEADERS = 1
 252 };
 253
 254 extern void create_preheaders (int);
 255 extern void force_single_succ_latches (void);
 256
 257 extern void verify_loop_structure (void);
 258
 259 /* Loop analysis.  */
 260 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
 261 gcov_type expected_loop_iterations_unbounded (const struct loop *);
 262 extern unsigned expected_loop_iterations (const struct loop *);
 263 extern rtx doloop_condition_get (rtx);
 264
 265 void estimate_numbers_of_iterations_loop (struct loop *);
 266 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool);
 267 bool estimated_loop_iterations (struct loop *, bool, double_int *);
 268
 269 /* Loop manipulation.  */
 270 extern bool can_duplicate_loop_p (struct loop *loop);
 271
 272 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 273                                            duplicate_loop_to_header_edge.  */
 274 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 275                                            field of newly create BB.  */
 276 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 277                                            a complete peeling.  */
 278
 279 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 280 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 281                                            unsigned, sbitmap, edge,
 282                                            VEC (edge, heap) **, int);
 283 extern struct loop *loopify (edge, edge,
 284                              basic_block, edge, edge, bool,
 285                              unsigned, unsigned);
 286 struct loop * loop_version (struct loop *, void *,
 287                             basic_block *, unsigned, unsigned, unsigned, bool);
 288 extern bool remove_path (edge);
 289 void scale_loop_frequencies (struct loop *, int, int);
 290
 291 /* Induction variable analysis.  */
 292
 293 /* The description of induction variable.  The things are a bit complicated
 294    due to need to handle subregs and extends.  The value of the object described
 295    by it can be obtained as follows (all computations are done in extend_mode):
 296
 297    Value in i-th iteration is
 298      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 299
 300    If first_special is true, the value in the first iteration is
 301      delta + mult * base
 302
 303    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 304      subreg_{mode} (base + i * step)
 305
 306    The get_iv_value function can be used to obtain these expressions.
 307
 308    ??? Add a third mode field that would specify the mode in that inner
 309    computation is done, which would enable it to be different from the
 310    outer one?  */
 311
 312 struct rtx_iv
 313 {
 314   /* Its base and step (mode of base and step is supposed to be extend_mode,
 315      see the description above).  */
 316   rtx base, step;
 317
 318   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 319   enum rtx_code extend;
 320
 321   /* Operations applied in the extended mode.  */
 322   rtx delta, mult;
 323
 324   /* The mode it is extended to.  */
 325   enum machine_mode extend_mode;
 326
 327   /* The mode the variable iterates in.  */
 328   enum machine_mode mode;
 329
 330   /* Whether the first iteration needs to be handled specially.  */
 331   unsigned first_special : 1;
 332 };
 333
 334 /* The description of an exit from the loop and of the number of iterations
 335    till we take the exit.  */
 336
 337 struct niter_desc
 338 {
 339   /* The edge out of the loop.  */
 340   edge out_edge;
 341
 342   /* The other edge leading from the condition.  */
 343   edge in_edge;
 344
 345   /* True if we are able to say anything about number of iterations of the
 346      loop.  */
 347   bool simple_p;
 348
 349   /* True if the loop iterates the constant number of times.  */
 350   bool const_iter;
 351
 352   /* Number of iterations if constant.  */
 353   unsigned HOST_WIDEST_INT niter;
 354
 355   /* Upper bound on the number of iterations.  */
 356   unsigned HOST_WIDEST_INT niter_max;
 357
 358   /* Assumptions under that the rest of the information is valid.  */
 359   rtx assumptions;
 360
 361   /* Assumptions under that the loop ends before reaching the latch,
 362      even if value of niter_expr says otherwise.  */
 363   rtx noloop_assumptions;
 364
 365   /* Condition under that the loop is infinite.  */
 366   rtx infinite;
 367
 368   /* Whether the comparison is signed.  */
 369   bool signed_p;
 370
 371   /* The mode in that niter_expr should be computed.  */
 372   enum machine_mode mode;
 373
 374   /* The number of iterations of the loop.  */
 375   rtx niter_expr;
 376 };
 377
 378 extern void iv_analysis_loop_init (struct loop *);
 379 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 380 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 381 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 382 extern rtx get_iv_value (struct rtx_iv *, rtx);
 383 extern bool biv_p (rtx, rtx);
 384 extern void find_simple_exit (struct loop *, struct niter_desc *);
 385 extern void iv_analysis_done (void);
 386 extern struct df *iv_current_loop_df (void);
 387
 388 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 389 extern void free_simple_loop_desc (struct loop *loop);
 390
 391 static inline struct niter_desc *
 392 simple_loop_desc (struct loop *loop)
 393 {
 394   return (struct niter_desc *) loop->aux;
 395 }
 396
 397 /* Accessors for the loop structures.  */
 398
 399 /* Returns the loop with index NUM from current_loops.  */
 400
 401 static inline struct loop *
 402 get_loop (unsigned num)
 403 {
 404   return VEC_index (loop_p, current_loops->larray, num);
 405 }
 406
 407 /* Returns the number of superloops of LOOP.  */
 408
 409 static inline unsigned
 410 loop_depth (const struct loop *loop)
 411 {
 412   return VEC_length (loop_p, loop->superloops);
 413 }
 414
 415 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
 416    loop.  */
 417
 418 static inline struct loop *
 419 loop_outer (const struct loop *loop)
 420 {
 421   unsigned n = VEC_length (loop_p, loop->superloops);
 422
 423   if (n == 0)
 424     return NULL;
 425
 426   return VEC_index (loop_p, loop->superloops, n - 1);
 427 }
 428
 429 /* Returns the list of loops in current_loops.  */
 430
 431 static inline VEC (loop_p, heap) *
 432 get_loops (void)
 433 {
 434   if (!current_loops)
 435     return NULL;
 436
 437   return current_loops->larray;
 438 }
 439
 440 /* Returns the number of loops in current_loops (including the removed
 441    ones and the fake loop that forms the root of the loop tree).  */
 442
 443 static inline unsigned
 444 number_of_loops (void)
 445 {
 446   if (!current_loops)
 447     return 0;
 448
 449   return VEC_length (loop_p, current_loops->larray);
 450 }
 451
 452 /* Loop iterators.  */
 453
 454 /* Flags for loop iteration.  */
 455
 456 enum li_flags
 457 {
 458   LI_INCLUDE_ROOT = 1,          /* Include the fake root of the loop tree.  */
 459   LI_FROM_INNERMOST = 2,        /* Iterate over the loops in the reverse order,
 460                                    starting from innermost ones.  */
 461   LI_ONLY_INNERMOST = 4         /* Iterate only over innermost loops.  */
 462 };
 463
 464 /* The iterator for loops.  */
 465
 466 typedef struct
 467 {
 468   /* The list of loops to visit.  */
 469   VEC(int,heap) *to_visit;
 470
 471   /* The index of the actual loop.  */
 472   unsigned idx;
 473 } loop_iterator;
 474
 475 static inline void
 476 fel_next (loop_iterator *li, loop_p *loop)
 477 {
 478   int anum;
 479
 480   while (VEC_iterate (int, li->to_visit, li->idx, anum))
 481     {
 482       li->idx++;
 483       *loop = get_loop (anum);
 484       if (*loop)
 485         return;
 486     }
 487
 488   VEC_free (int, heap, li->to_visit);
 489   *loop = NULL;
 490 }
 491
 492 static inline void
 493 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
 494 {
 495   struct loop *aloop;
 496   unsigned i;
 497   int mn;
 498
 499   li->idx = 0;
 500   if (!current_loops)
 501     {
 502       li->to_visit = NULL;
 503       *loop = NULL;
 504       return;
 505     }
 506
 507   li->to_visit = VEC_alloc (int, heap, number_of_loops ());
 508   mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
 509
 510   if (flags & LI_ONLY_INNERMOST)
 511     {
 512       for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
 513         if (aloop != NULL
 514             && aloop->inner == NULL
 515             && aloop->num >= mn)
 516           VEC_quick_push (int, li->to_visit, aloop->num);
 517     }
 518   else if (flags & LI_FROM_INNERMOST)
 519     {
 520       /* Push the loops to LI->TO_VISIT in postorder.  */
 521       for (aloop = current_loops->tree_root;
 522            aloop->inner != NULL;
 523            aloop = aloop->inner)
 524         continue;
 525
 526       while (1)
 527         {
 528           if (aloop->num >= mn)
 529             VEC_quick_push (int, li->to_visit, aloop->num);
 530
 531           if (aloop->next)
 532             {
 533               for (aloop = aloop->next;
 534                    aloop->inner != NULL;
 535                    aloop = aloop->inner)
 536                 continue;
 537             }
 538           else if (!loop_outer (aloop))
 539             break;
 540           else
 541             aloop = loop_outer (aloop);
 542         }
 543     }
 544   else
 545     {
 546       /* Push the loops to LI->TO_VISIT in preorder.  */
 547       aloop = current_loops->tree_root;
 548       while (1)
 549         {
 550           if (aloop->num >= mn)
 551             VEC_quick_push (int, li->to_visit, aloop->num);
 552
 553           if (aloop->inner != NULL)
 554             aloop = aloop->inner;
 555           else
 556             {
 557               while (aloop != NULL && aloop->next == NULL)
 558                 aloop = loop_outer (aloop);
 559               if (aloop == NULL)
 560                 break;
 561               aloop = aloop->next;
 562             }
 563         }
 564     }
 565
 566   fel_next (li, loop);
 567 }
 568
 569 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
 570   for (fel_init (&(LI), &(LOOP), FLAGS); \
 571        (LOOP); \
 572        fel_next (&(LI), &(LOOP)))
 573
 574 #define FOR_EACH_LOOP_BREAK(LI) \
 575   { \
 576     VEC_free (int, heap, (LI)->to_visit); \
 577     break; \
 578   }
 579
 580 /* The properties of the target.  */
 581
 582 extern unsigned target_avail_regs;
 583 extern unsigned target_res_regs;
 584 extern unsigned target_reg_cost;
 585 extern unsigned target_spill_cost;
 586
 587 /* Register pressure estimation for induction variable optimizations & loop
 588    invariant motion.  */
 589 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned);
 590 extern void init_set_costs (void);
 591
 592 /* Loop optimizer initialization.  */
 593 extern void loop_optimizer_init (unsigned);
 594 extern void loop_optimizer_finalize (void);
 595
 596 /* Optimization passes.  */
 597 extern void unswitch_loops (void);
 598
 599 enum
 600 {
 601   UAP_PEEL = 1,         /* Enables loop peeling.  */
 602   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 603   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 604 };
 605
 606 extern void unroll_and_peel_loops (int);
 607 extern void doloop_optimize_loops (void);
 608 extern void move_loop_invariants (void);
 609
 610 #endif /* GCC_CFGLOOP_H */