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