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   /* True if the bound is "realistic" -- i.e., most likely the loop really has
  69      number of iterations close to the bound.  Exact bounds (if the number of
  70      iterations of a loop is a constant) and bounds derived from the size of
  71      data accessed in the loop are considered realistic.  */
  72   bool realistic;
  73
  74   /* The next bound in the list.  */
  75   struct nb_iter_bound *next;
  76 };
  77
  78 /* Description of the loop exit.  */
  79
  80 struct loop_exit
  81 {
  82   /* The exit edge.  */
  83   edge e;
  84
  85   /* Previous and next exit in the list of the exits of the loop.  */
  86   struct loop_exit *prev;
  87   struct loop_exit *next;
  88
  89   /* Next element in the list of loops from that E exits.  */
  90   struct loop_exit *next_e;
  91 };
  92
  93 /* Structure to hold information for each natural loop.  */
  94 struct loop
  95 {
  96   /* Index into loops array.  */
  97   int num;
  98
  99   /* Basic block of loop header.  */
 100   basic_block header;
 101
 102   /* Basic block of loop latch.  */
 103   basic_block 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   /* The loop nesting depth.  */
 118   int depth;
 119
 120   /* Superloops of the loop.  */
 121   struct loop **pred;
 122
 123   /* The outer (parent) loop or NULL if outermost loop.  */
 124   struct loop *outer;
 125
 126   /* The first inner (child) loop or NULL if innermost loop.  */
 127   struct loop *inner;
 128
 129   /* Link to the next (sibling) loop.  */
 130   struct loop *next;
 131
 132   /* Loop that is copy of this loop.  */
 133   struct loop *copy;
 134
 135   /* Auxiliary info specific to a pass.  */
 136   void *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
 148     {
 149       /* Estimate was not computed yet.  */
 150       EST_NOT_COMPUTED,
 151       /* Estimate was computed, but we could derive no useful bound.  */
 152       EST_NOT_AVAILABLE,
 153       /* Estimate is ready.  */
 154       EST_AVAILABLE
 155     } estimate_state;
 156   double_int estimated_nb_iterations;
 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 extern unsigned expected_loop_iterations (const struct loop *);
 266 extern rtx doloop_condition_get (rtx);
 267
 268 void estimate_numbers_of_iterations_loop (struct loop *);
 269 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool);
 270
 271 /* Loop manipulation.  */
 272 extern bool can_duplicate_loop_p (struct loop *loop);
 273
 274 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 275                                            duplicate_loop_to_header_edge.  */
 276 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 277                                            field of newly create BB.  */
 278 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 279                                            a complete peeling.  */
 280
 281 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 282 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 283                                            unsigned, sbitmap, edge,
 284                                            VEC (edge, heap) **, int);
 285 extern struct loop *loopify (edge, edge,
 286                              basic_block, edge, edge, bool,
 287                              unsigned, unsigned);
 288 struct loop * loop_version (struct loop *, void *,
 289                             basic_block *, unsigned, unsigned, unsigned, bool);
 290 extern bool remove_path (edge);
 291 void scale_loop_frequencies (struct loop *, int, int);
 292
 293 /* Induction variable analysis.  */
 294
 295 /* The description of induction variable.  The things are a bit complicated
 296    due to need to handle subregs and extends.  The value of the object described
 297    by it can be obtained as follows (all computations are done in extend_mode):
 298
 299    Value in i-th iteration is
 300      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 301
 302    If first_special is true, the value in the first iteration is
 303      delta + mult * base
 304
 305    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 306      subreg_{mode} (base + i * step)
 307
 308    The get_iv_value function can be used to obtain these expressions.
 309
 310    ??? Add a third mode field that would specify the mode in that inner
 311    computation is done, which would enable it to be different from the
 312    outer one?  */
 313
 314 struct rtx_iv
 315 {
 316   /* Its base and step (mode of base and step is supposed to be extend_mode,
 317      see the description above).  */
 318   rtx base, step;
 319
 320   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 321   enum rtx_code extend;
 322
 323   /* Operations applied in the extended mode.  */
 324   rtx delta, mult;
 325
 326   /* The mode it is extended to.  */
 327   enum machine_mode extend_mode;
 328
 329   /* The mode the variable iterates in.  */
 330   enum machine_mode mode;
 331
 332   /* Whether the first iteration needs to be handled specially.  */
 333   unsigned first_special : 1;
 334 };
 335
 336 /* The description of an exit from the loop and of the number of iterations
 337    till we take the exit.  */
 338
 339 struct niter_desc
 340 {
 341   /* The edge out of the loop.  */
 342   edge out_edge;
 343
 344   /* The other edge leading from the condition.  */
 345   edge in_edge;
 346
 347   /* True if we are able to say anything about number of iterations of the
 348      loop.  */
 349   bool simple_p;
 350
 351   /* True if the loop iterates the constant number of times.  */
 352   bool const_iter;
 353
 354   /* Number of iterations if constant.  */
 355   unsigned HOST_WIDEST_INT niter;
 356
 357   /* Upper bound on the number of iterations.  */
 358   unsigned HOST_WIDEST_INT niter_max;
 359
 360   /* Assumptions under that the rest of the information is valid.  */
 361   rtx assumptions;
 362
 363   /* Assumptions under that the loop ends before reaching the latch,
 364      even if value of niter_expr says otherwise.  */
 365   rtx noloop_assumptions;
 366
 367   /* Condition under that the loop is infinite.  */
 368   rtx infinite;
 369
 370   /* Whether the comparison is signed.  */
 371   bool signed_p;
 372
 373   /* The mode in that niter_expr should be computed.  */
 374   enum machine_mode mode;
 375
 376   /* The number of iterations of the loop.  */
 377   rtx niter_expr;
 378 };
 379
 380 extern void iv_analysis_loop_init (struct loop *);
 381 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 382 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 383 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 384 extern rtx get_iv_value (struct rtx_iv *, rtx);
 385 extern bool biv_p (rtx, rtx);
 386 extern void find_simple_exit (struct loop *, struct niter_desc *);
 387 extern void iv_analysis_done (void);
 388 extern struct df *iv_current_loop_df (void);
 389
 390 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 391 extern void free_simple_loop_desc (struct loop *loop);
 392
 393 static inline struct niter_desc *
 394 simple_loop_desc (struct loop *loop)
 395 {
 396   return (struct niter_desc *) loop->aux;
 397 }
 398
 399 /* Accessors for the loop structures.  */
 400
 401 /* Returns the loop with index NUM from current_loops.  */
 402
 403 static inline struct loop *
 404 get_loop (unsigned num)
 405 {
 406   return VEC_index (loop_p, current_loops->larray, num);
 407 }
 408
 409 /* Returns the list of loops in current_loops.  */
 410
 411 static inline VEC (loop_p, heap) *
 412 get_loops (void)
 413 {
 414   if (!current_loops)
 415     return NULL;
 416
 417   return current_loops->larray;
 418 }
 419
 420 /* Returns the number of loops in current_loops (including the removed
 421    ones and the fake loop that forms the root of the loop tree).  */
 422
 423 static inline unsigned
 424 number_of_loops (void)
 425 {
 426   if (!current_loops)
 427     return 0;
 428
 429   return VEC_length (loop_p, current_loops->larray);
 430 }
 431
 432 /* Loop iterators.  */
 433
 434 /* Flags for loop iteration.  */
 435
 436 enum li_flags
 437 {
 438   LI_INCLUDE_ROOT = 1,          /* Include the fake root of the loop tree.  */
 439   LI_FROM_INNERMOST = 2,        /* Iterate over the loops in the reverse order,
 440                                    starting from innermost ones.  */
 441   LI_ONLY_INNERMOST = 4         /* Iterate only over innermost loops.  */
 442 };
 443
 444 /* The iterator for loops.  */
 445
 446 typedef struct
 447 {
 448   /* The list of loops to visit.  */
 449   VEC(int,heap) *to_visit;
 450
 451   /* The index of the actual loop.  */
 452   unsigned idx;
 453 } loop_iterator;
 454
 455 static inline void
 456 fel_next (loop_iterator *li, loop_p *loop)
 457 {
 458   int anum;
 459
 460   while (VEC_iterate (int, li->to_visit, li->idx, anum))
 461     {
 462       li->idx++;
 463       *loop = get_loop (anum);
 464       if (*loop)
 465         return;
 466     }
 467
 468   VEC_free (int, heap, li->to_visit);
 469   *loop = NULL;
 470 }
 471
 472 static inline void
 473 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
 474 {
 475   struct loop *aloop;
 476   unsigned i;
 477   int mn;
 478
 479   li->idx = 0;
 480   if (!current_loops)
 481     {
 482       li->to_visit = NULL;
 483       *loop = NULL;
 484       return;
 485     }
 486
 487   li->to_visit = VEC_alloc (int, heap, number_of_loops ());
 488   mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
 489
 490   if (flags & LI_ONLY_INNERMOST)
 491     {
 492       for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
 493         if (aloop != NULL
 494             && aloop->inner == NULL
 495             && aloop->num >= mn)
 496           VEC_quick_push (int, li->to_visit, aloop->num);
 497     }
 498   else if (flags & LI_FROM_INNERMOST)
 499     {
 500       /* Push the loops to LI->TO_VISIT in postorder.  */
 501       for (aloop = current_loops->tree_root;
 502            aloop->inner != NULL;
 503            aloop = aloop->inner)
 504         continue;
 505
 506       while (1)
 507         {
 508           if (aloop->num >= mn)
 509             VEC_quick_push (int, li->to_visit, aloop->num);
 510
 511           if (aloop->next)
 512             {
 513               for (aloop = aloop->next;
 514                    aloop->inner != NULL;
 515                    aloop = aloop->inner)
 516                 continue;
 517             }
 518           else if (!aloop->outer)
 519             break;
 520           else
 521             aloop = aloop->outer;
 522         }
 523     }
 524   else
 525     {
 526       /* Push the loops to LI->TO_VISIT in preorder.  */
 527       aloop = current_loops->tree_root;
 528       while (1)
 529         {
 530           if (aloop->num >= mn)
 531             VEC_quick_push (int, li->to_visit, aloop->num);
 532
 533           if (aloop->inner != NULL)
 534             aloop = aloop->inner;
 535           else
 536             {
 537               while (aloop != NULL && aloop->next == NULL)
 538                 aloop = aloop->outer;
 539               if (aloop == NULL)
 540                 break;
 541               aloop = aloop->next;
 542             }
 543         }
 544     }
 545
 546   fel_next (li, loop);
 547 }
 548
 549 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
 550   for (fel_init (&(LI), &(LOOP), FLAGS); \
 551        (LOOP); \
 552        fel_next (&(LI), &(LOOP)))
 553
 554 #define FOR_EACH_LOOP_BREAK(LI) \
 555   { \
 556     VEC_free (int, heap, (LI)->to_visit); \
 557     break; \
 558   }
 559
 560 /* The properties of the target.  */
 561
 562 extern unsigned target_avail_regs;      /* Number of available registers.  */
 563 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 564 extern unsigned target_small_cost;      /* The cost for register when there
 565                                            is a free one.  */
 566 extern unsigned target_pres_cost;       /* The cost for register when there are
 567                                            not too many free ones.  */
 568 extern unsigned target_spill_cost;      /* The cost for register when we need
 569                                            to spill.  */
 570
 571 /* Register pressure estimation for induction variable optimizations & loop
 572    invariant motion.  */
 573 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 574 extern void init_set_costs (void);
 575
 576 /* Loop optimizer initialization.  */
 577 extern void loop_optimizer_init (unsigned);
 578 extern void loop_optimizer_finalize (void);
 579
 580 /* Optimization passes.  */
 581 extern void unswitch_loops (void);
 582
 583 enum
 584 {
 585   UAP_PEEL = 1,         /* Enables loop peeling.  */
 586   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 587   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 588 };
 589
 590 extern void unroll_and_peel_loops (int);
 591 extern void doloop_optimize_loops (void);
 592 extern void move_loop_invariants (void);
 593
 594 #endif /* GCC_CFGLOOP_H */