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
  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
  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
  50 {
  51   /* The statement STMT is executed at most ...  */
  52   tree 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
  75 {
  76   /* The exit edge.  */
  77   edge 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 /* Structure to hold information for each natural loop.  */
  88 struct loop
  89 {
  90   /* Index into loops array.  */
  91   int num;
  92
  93   /* Basic block of loop header.  */
  94   basic_block header;
  95
  96   /* Basic block of loop latch.  */
  97   basic_block latch;
  98
  99   /* For loop unrolling/peeling decision.  */
 100   struct lpt_decision lpt_decision;
 101
 102   /* Number of loop insns.  */
 103   unsigned ninsns;
 104
 105   /* Average number of executed insns per iteration.  */
 106   unsigned av_ninsns;
 107
 108   /* Number of blocks contained within the loop.  */
 109   unsigned num_nodes;
 110
 111   /* The loop nesting depth.  */
 112   int depth;
 113
 114   /* Superloops of the loop.  */
 115   struct loop **pred;
 116
 117   /* The outer (parent) loop or NULL if outermost loop.  */
 118   struct loop *outer;
 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   void *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 };
 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 typedef struct loop *loop_p;
 180 DEF_VEC_P (loop_p);
 181 DEF_VEC_ALLOC_P (loop_p, heap);
 182
 183 /* Structure to hold CFG information about natural loops within a function.  */
 184 struct loops
 185 {
 186   /* State of loops.  */
 187   int state;
 188
 189   /* Array of the loops.  */
 190   VEC (loop_p, heap) *larray;
 191
 192   /* Maps edges to the list of their descriptions as loop exits.  Edges
 193      whose sources or destinations have loop_father == NULL (which may
 194      happen during the cfg manipulations) should not appear in EXITS.  */
 195   htab_t exits;
 196
 197   /* Pointer to root of loop hierarchy tree.  */
 198   struct loop *tree_root;
 199 };
 200
 201 /* Loop recognition.  */
 202 extern int flow_loops_find (struct loops *);
 203 extern void disambiguate_loops_with_multiple_latches (void);
 204 extern void flow_loops_free (struct loops *);
 205 extern void flow_loops_dump (FILE *,
 206                              void (*)(const struct loop *, FILE *, int), int);
 207 extern void flow_loop_dump (const struct loop *, FILE *,
 208                             void (*)(const struct loop *, FILE *, int), int);
 209 struct loop *alloc_loop (void);
 210 extern void flow_loop_free (struct loop *);
 211 int flow_loop_nodes_find (basic_block, struct loop *);
 212 void fix_loop_structure (bitmap changed_bbs);
 213 void mark_irreducible_loops (void);
 214 void release_recorded_exits (void);
 215 void record_loop_exits (void);
 216 void rescan_loop_exit (edge, bool, bool);
 217
 218 /* Loop data structure manipulation/querying.  */
 219 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 220 extern void flow_loop_tree_node_remove (struct loop *);
 221 extern void add_loop (struct loop *, struct loop *);
 222 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 223 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
 224 extern struct loop * find_common_loop (struct loop *, struct loop *);
 225 struct loop *superloop_at_depth (struct loop *, unsigned);
 226 struct eni_weights_d;
 227 extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *);
 228 extern int num_loop_insns (struct loop *);
 229 extern int average_num_loop_insns (struct loop *);
 230 extern unsigned get_loop_level (const struct loop *);
 231 extern bool loop_exit_edge_p (const struct loop *, edge);
 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 VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
 241 edge single_exit (const struct loop *);
 242 extern unsigned num_loop_branches (const struct loop *);
 243
 244 extern edge loop_preheader_edge (const struct loop *);
 245 extern edge loop_latch_edge (const struct loop *);
 246
 247 extern void add_bb_to_loop (basic_block, struct loop *);
 248 extern void remove_bb_from_loops (basic_block);
 249
 250 extern void cancel_loop_tree (struct loop *);
 251 extern void delete_loop (struct loop *);
 252
 253 enum
 254 {
 255   CP_SIMPLE_PREHEADERS = 1
 256 };
 257
 258 extern void create_preheaders (int);
 259 extern void force_single_succ_latches (void);
 260
 261 extern void verify_loop_structure (void);
 262
 263 /* Loop analysis.  */
 264 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
 265 gcov_type expected_loop_iterations_unbounded (const struct loop *);
 266 extern unsigned expected_loop_iterations (const struct loop *);
 267 extern rtx doloop_condition_get (rtx);
 268
 269 void estimate_numbers_of_iterations_loop (struct loop *);
 270 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool);
 271 bool estimated_loop_iterations (struct loop *, bool, double_int *);
 272
 273 /* Loop manipulation.  */
 274 extern bool can_duplicate_loop_p (struct loop *loop);
 275
 276 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 277                                            duplicate_loop_to_header_edge.  */
 278 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 279                                            field of newly create BB.  */
 280 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 281                                            a complete peeling.  */
 282
 283 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 284 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 285                                            unsigned, sbitmap, edge,
 286                                            VEC (edge, heap) **, int);
 287 extern struct loop *loopify (edge, edge,
 288                              basic_block, edge, edge, bool,
 289                              unsigned, unsigned);
 290 struct loop * loop_version (struct loop *, void *,
 291                             basic_block *, unsigned, unsigned, unsigned, bool);
 292 extern bool remove_path (edge);
 293 void scale_loop_frequencies (struct loop *, int, int);
 294
 295 /* Induction variable analysis.  */
 296
 297 /* The description of induction variable.  The things are a bit complicated
 298    due to need to handle subregs and extends.  The value of the object described
 299    by it can be obtained as follows (all computations are done in extend_mode):
 300
 301    Value in i-th iteration is
 302      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 303
 304    If first_special is true, the value in the first iteration is
 305      delta + mult * base
 306
 307    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 308      subreg_{mode} (base + i * step)
 309
 310    The get_iv_value function can be used to obtain these expressions.
 311
 312    ??? Add a third mode field that would specify the mode in that inner
 313    computation is done, which would enable it to be different from the
 314    outer one?  */
 315
 316 struct rtx_iv
 317 {
 318   /* Its base and step (mode of base and step is supposed to be extend_mode,
 319      see the description above).  */
 320   rtx base, step;
 321
 322   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 323   enum rtx_code extend;
 324
 325   /* Operations applied in the extended mode.  */
 326   rtx delta, mult;
 327
 328   /* The mode it is extended to.  */
 329   enum machine_mode extend_mode;
 330
 331   /* The mode the variable iterates in.  */
 332   enum machine_mode mode;
 333
 334   /* Whether the first iteration needs to be handled specially.  */
 335   unsigned first_special : 1;
 336 };
 337
 338 /* The description of an exit from the loop and of the number of iterations
 339    till we take the exit.  */
 340
 341 struct niter_desc
 342 {
 343   /* The edge out of the loop.  */
 344   edge out_edge;
 345
 346   /* The other edge leading from the condition.  */
 347   edge in_edge;
 348
 349   /* True if we are able to say anything about number of iterations of the
 350      loop.  */
 351   bool simple_p;
 352
 353   /* True if the loop iterates the constant number of times.  */
 354   bool const_iter;
 355
 356   /* Number of iterations if constant.  */
 357   unsigned HOST_WIDEST_INT niter;
 358
 359   /* Upper bound on the number of iterations.  */
 360   unsigned HOST_WIDEST_INT niter_max;
 361
 362   /* Assumptions under that the rest of the information is valid.  */
 363   rtx assumptions;
 364
 365   /* Assumptions under that the loop ends before reaching the latch,
 366      even if value of niter_expr says otherwise.  */
 367   rtx noloop_assumptions;
 368
 369   /* Condition under that the loop is infinite.  */
 370   rtx infinite;
 371
 372   /* Whether the comparison is signed.  */
 373   bool signed_p;
 374
 375   /* The mode in that niter_expr should be computed.  */
 376   enum machine_mode mode;
 377
 378   /* The number of iterations of the loop.  */
 379   rtx niter_expr;
 380 };
 381
 382 extern void iv_analysis_loop_init (struct loop *);
 383 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 384 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 385 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 386 extern rtx get_iv_value (struct rtx_iv *, rtx);
 387 extern bool biv_p (rtx, rtx);
 388 extern void find_simple_exit (struct loop *, struct niter_desc *);
 389 extern void iv_analysis_done (void);
 390 extern struct df *iv_current_loop_df (void);
 391
 392 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 393 extern void free_simple_loop_desc (struct loop *loop);
 394
 395 static inline struct niter_desc *
 396 simple_loop_desc (struct loop *loop)
 397 {
 398   return (struct niter_desc *) loop->aux;
 399 }
 400
 401 /* Accessors for the loop structures.  */
 402
 403 /* Returns the loop with index NUM from current_loops.  */
 404
 405 static inline struct loop *
 406 get_loop (unsigned num)
 407 {
 408   return VEC_index (loop_p, current_loops->larray, num);
 409 }
 410
 411 /* Returns the list of loops in current_loops.  */
 412
 413 static inline VEC (loop_p, heap) *
 414 get_loops (void)
 415 {
 416   if (!current_loops)
 417     return NULL;
 418
 419   return current_loops->larray;
 420 }
 421
 422 /* Returns the number of loops in current_loops (including the removed
 423    ones and the fake loop that forms the root of the loop tree).  */
 424
 425 static inline unsigned
 426 number_of_loops (void)
 427 {
 428   if (!current_loops)
 429     return 0;
 430
 431   return VEC_length (loop_p, current_loops->larray);
 432 }
 433
 434 /* Loop iterators.  */
 435
 436 /* Flags for loop iteration.  */
 437
 438 enum li_flags
 439 {
 440   LI_INCLUDE_ROOT = 1,          /* Include the fake root of the loop tree.  */
 441   LI_FROM_INNERMOST = 2,        /* Iterate over the loops in the reverse order,
 442                                    starting from innermost ones.  */
 443   LI_ONLY_INNERMOST = 4         /* Iterate only over innermost loops.  */
 444 };
 445
 446 /* The iterator for loops.  */
 447
 448 typedef struct
 449 {
 450   /* The list of loops to visit.  */
 451   VEC(int,heap) *to_visit;
 452
 453   /* The index of the actual loop.  */
 454   unsigned idx;
 455 } loop_iterator;
 456
 457 static inline void
 458 fel_next (loop_iterator *li, loop_p *loop)
 459 {
 460   int anum;
 461
 462   while (VEC_iterate (int, li->to_visit, li->idx, anum))
 463     {
 464       li->idx++;
 465       *loop = get_loop (anum);
 466       if (*loop)
 467         return;
 468     }
 469
 470   VEC_free (int, heap, li->to_visit);
 471   *loop = NULL;
 472 }
 473
 474 static inline void
 475 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
 476 {
 477   struct loop *aloop;
 478   unsigned i;
 479   int mn;
 480
 481   li->idx = 0;
 482   if (!current_loops)
 483     {
 484       li->to_visit = NULL;
 485       *loop = NULL;
 486       return;
 487     }
 488
 489   li->to_visit = VEC_alloc (int, heap, number_of_loops ());
 490   mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
 491
 492   if (flags & LI_ONLY_INNERMOST)
 493     {
 494       for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
 495         if (aloop != NULL
 496             && aloop->inner == NULL
 497             && aloop->num >= mn)
 498           VEC_quick_push (int, li->to_visit, aloop->num);
 499     }
 500   else if (flags & LI_FROM_INNERMOST)
 501     {
 502       /* Push the loops to LI->TO_VISIT in postorder.  */
 503       for (aloop = current_loops->tree_root;
 504            aloop->inner != NULL;
 505            aloop = aloop->inner)
 506         continue;
 507
 508       while (1)
 509         {
 510           if (aloop->num >= mn)
 511             VEC_quick_push (int, li->to_visit, aloop->num);
 512
 513           if (aloop->next)
 514             {
 515               for (aloop = aloop->next;
 516                    aloop->inner != NULL;
 517                    aloop = aloop->inner)
 518                 continue;
 519             }
 520           else if (!aloop->outer)
 521             break;
 522           else
 523             aloop = aloop->outer;
 524         }
 525     }
 526   else
 527     {
 528       /* Push the loops to LI->TO_VISIT in preorder.  */
 529       aloop = current_loops->tree_root;
 530       while (1)
 531         {
 532           if (aloop->num >= mn)
 533             VEC_quick_push (int, li->to_visit, aloop->num);
 534
 535           if (aloop->inner != NULL)
 536             aloop = aloop->inner;
 537           else
 538             {
 539               while (aloop != NULL && aloop->next == NULL)
 540                 aloop = aloop->outer;
 541               if (aloop == NULL)
 542                 break;
 543               aloop = aloop->next;
 544             }
 545         }
 546     }
 547
 548   fel_next (li, loop);
 549 }
 550
 551 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
 552   for (fel_init (&(LI), &(LOOP), FLAGS); \
 553        (LOOP); \
 554        fel_next (&(LI), &(LOOP)))
 555
 556 #define FOR_EACH_LOOP_BREAK(LI) \
 557   { \
 558     VEC_free (int, heap, (LI)->to_visit); \
 559     break; \
 560   }
 561
 562 /* The properties of the target.  */
 563
 564 extern unsigned target_avail_regs;      /* Number of available registers.  */
 565 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 566 extern unsigned target_small_cost;      /* The cost for register when there
 567                                            is a free one.  */
 568 extern unsigned target_pres_cost;       /* The cost for register when there are
 569                                            not too many free ones.  */
 570 extern unsigned target_spill_cost;      /* The cost for register when we need
 571                                            to spill.  */
 572
 573 /* Register pressure estimation for induction variable optimizations & loop
 574    invariant motion.  */
 575 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 576 extern void init_set_costs (void);
 577
 578 /* Loop optimizer initialization.  */
 579 extern void loop_optimizer_init (unsigned);
 580 extern void loop_optimizer_finalize (void);
 581
 582 /* Optimization passes.  */
 583 extern void unswitch_loops (void);
 584
 585 enum
 586 {
 587   UAP_PEEL = 1,         /* Enables loop peeling.  */
 588   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 589   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 590 };
 591
 592 extern void unroll_and_peel_loops (int);
 593 extern void doloop_optimize_loops (void);
 594 extern void move_loop_invariants (void);
 595
 596 #endif /* GCC_CFGLOOP_H */