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 };
 173
 174 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 175                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 176
 177 typedef struct loop *loop_p;
 178 DEF_VEC_P (loop_p);
 179 DEF_VEC_ALLOC_P (loop_p, heap);
 180
 181 /* Structure to hold CFG information about natural loops within a function.  */
 182 struct loops
 183 {
 184   /* State of loops.  */
 185   int state;
 186
 187   /* Array of the loops.  */
 188   VEC (loop_p, heap) *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 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 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 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 basic_block *get_loop_body_in_dom_order (const struct loop *);
 233 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 234 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
 235 edge single_exit (const struct loop *);
 236 extern unsigned num_loop_branches (const struct loop *);
 237
 238 extern edge loop_preheader_edge (const struct loop *);
 239 extern edge loop_latch_edge (const struct loop *);
 240
 241 extern void add_bb_to_loop (basic_block, struct loop *);
 242 extern void remove_bb_from_loops (basic_block);
 243
 244 extern void cancel_loop_tree (struct loop *);
 245 extern void delete_loop (struct loop *);
 246
 247 enum
 248 {
 249   CP_SIMPLE_PREHEADERS = 1
 250 };
 251
 252 extern void create_preheaders (int);
 253 extern void force_single_succ_latches (void);
 254
 255 extern void verify_loop_structure (void);
 256
 257 /* Loop analysis.  */
 258 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
 259 extern unsigned expected_loop_iterations (const struct loop *);
 260 extern rtx doloop_condition_get (rtx);
 261
 262 /* Loop manipulation.  */
 263 extern bool can_duplicate_loop_p (struct loop *loop);
 264
 265 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 266                                            duplicate_loop_to_header_edge.  */
 267 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 268                                            field of newly create BB.  */
 269 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 270                                            a complete peeling.  */
 271
 272 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 273 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 274                                            unsigned, sbitmap, edge,
 275                                            VEC (edge, heap) **, int);
 276 extern struct loop *loopify (edge, edge,
 277                              basic_block, edge, edge, bool,
 278                              unsigned, unsigned);
 279 struct loop * loop_version (struct loop *, void *,
 280                             basic_block *, unsigned, unsigned, unsigned, bool);
 281 extern bool remove_path (edge);
 282 void scale_loop_frequencies (struct loop *, int, int);
 283
 284 /* Induction variable analysis.  */
 285
 286 /* The description of induction variable.  The things are a bit complicated
 287    due to need to handle subregs and extends.  The value of the object described
 288    by it can be obtained as follows (all computations are done in extend_mode):
 289
 290    Value in i-th iteration is
 291      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 292
 293    If first_special is true, the value in the first iteration is
 294      delta + mult * base
 295
 296    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 297      subreg_{mode} (base + i * step)
 298
 299    The get_iv_value function can be used to obtain these expressions.
 300
 301    ??? Add a third mode field that would specify the mode in that inner
 302    computation is done, which would enable it to be different from the
 303    outer one?  */
 304
 305 struct rtx_iv
 306 {
 307   /* Its base and step (mode of base and step is supposed to be extend_mode,
 308      see the description above).  */
 309   rtx base, step;
 310
 311   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 312   enum rtx_code extend;
 313
 314   /* Operations applied in the extended mode.  */
 315   rtx delta, mult;
 316
 317   /* The mode it is extended to.  */
 318   enum machine_mode extend_mode;
 319
 320   /* The mode the variable iterates in.  */
 321   enum machine_mode mode;
 322
 323   /* Whether the first iteration needs to be handled specially.  */
 324   unsigned first_special : 1;
 325 };
 326
 327 /* The description of an exit from the loop and of the number of iterations
 328    till we take the exit.  */
 329
 330 struct niter_desc
 331 {
 332   /* The edge out of the loop.  */
 333   edge out_edge;
 334
 335   /* The other edge leading from the condition.  */
 336   edge in_edge;
 337
 338   /* True if we are able to say anything about number of iterations of the
 339      loop.  */
 340   bool simple_p;
 341
 342   /* True if the loop iterates the constant number of times.  */
 343   bool const_iter;
 344
 345   /* Number of iterations if constant.  */
 346   unsigned HOST_WIDEST_INT niter;
 347
 348   /* Upper bound on the number of iterations.  */
 349   unsigned HOST_WIDEST_INT niter_max;
 350
 351   /* Assumptions under that the rest of the information is valid.  */
 352   rtx assumptions;
 353
 354   /* Assumptions under that the loop ends before reaching the latch,
 355      even if value of niter_expr says otherwise.  */
 356   rtx noloop_assumptions;
 357
 358   /* Condition under that the loop is infinite.  */
 359   rtx infinite;
 360
 361   /* Whether the comparison is signed.  */
 362   bool signed_p;
 363
 364   /* The mode in that niter_expr should be computed.  */
 365   enum machine_mode mode;
 366
 367   /* The number of iterations of the loop.  */
 368   rtx niter_expr;
 369 };
 370
 371 extern void iv_analysis_loop_init (struct loop *);
 372 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 373 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 374 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 375 extern rtx get_iv_value (struct rtx_iv *, rtx);
 376 extern bool biv_p (rtx, rtx);
 377 extern void find_simple_exit (struct loop *, struct niter_desc *);
 378 extern void iv_analysis_done (void);
 379 extern struct df *iv_current_loop_df (void);
 380
 381 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 382 extern void free_simple_loop_desc (struct loop *loop);
 383
 384 static inline struct niter_desc *
 385 simple_loop_desc (struct loop *loop)
 386 {
 387   return (struct niter_desc *) loop->aux;
 388 }
 389
 390 /* Accessors for the loop structures.  */
 391
 392 /* Returns the loop with index NUM from current_loops.  */
 393
 394 static inline struct loop *
 395 get_loop (unsigned num)
 396 {
 397   return VEC_index (loop_p, current_loops->larray, num);
 398 }
 399
 400 /* Returns the list of loops in current_loops.  */
 401
 402 static inline VEC (loop_p, heap) *
 403 get_loops (void)
 404 {
 405   if (!current_loops)
 406     return NULL;
 407
 408   return current_loops->larray;
 409 }
 410
 411 /* Returns the number of loops in current_loops (including the removed
 412    ones and the fake loop that forms the root of the loop tree).  */
 413
 414 static inline unsigned
 415 number_of_loops (void)
 416 {
 417   if (!current_loops)
 418     return 0;
 419
 420   return VEC_length (loop_p, current_loops->larray);
 421 }
 422
 423 /* Loop iterators.  */
 424
 425 /* Flags for loop iteration.  */
 426
 427 enum li_flags
 428 {
 429   LI_INCLUDE_ROOT = 1,          /* Include the fake root of the loop tree.  */
 430   LI_FROM_INNERMOST = 2,        /* Iterate over the loops in the reverse order,
 431                                    starting from innermost ones.  */
 432   LI_ONLY_INNERMOST = 4         /* Iterate only over innermost loops.  */
 433 };
 434
 435 /* The iterator for loops.  */
 436
 437 typedef struct
 438 {
 439   /* The list of loops to visit.  */
 440   VEC(int,heap) *to_visit;
 441
 442   /* The index of the actual loop.  */
 443   unsigned idx;
 444 } loop_iterator;
 445
 446 static inline void
 447 fel_next (loop_iterator *li, loop_p *loop)
 448 {
 449   int anum;
 450
 451   while (VEC_iterate (int, li->to_visit, li->idx, anum))
 452     {
 453       li->idx++;
 454       *loop = get_loop (anum);
 455       if (*loop)
 456         return;
 457     }
 458
 459   VEC_free (int, heap, li->to_visit);
 460   *loop = NULL;
 461 }
 462
 463 static inline void
 464 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
 465 {
 466   struct loop *aloop;
 467   unsigned i;
 468   int mn;
 469
 470   li->idx = 0;
 471   if (!current_loops)
 472     {
 473       li->to_visit = NULL;
 474       *loop = NULL;
 475       return;
 476     }
 477
 478   li->to_visit = VEC_alloc (int, heap, number_of_loops ());
 479   mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
 480
 481   if (flags & LI_ONLY_INNERMOST)
 482     {
 483       for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
 484         if (aloop != NULL
 485             && aloop->inner == NULL
 486             && aloop->num >= mn)
 487           VEC_quick_push (int, li->to_visit, aloop->num);
 488     }
 489   else if (flags & LI_FROM_INNERMOST)
 490     {
 491       /* Push the loops to LI->TO_VISIT in postorder.  */
 492       for (aloop = current_loops->tree_root;
 493            aloop->inner != NULL;
 494            aloop = aloop->inner)
 495         continue;
 496
 497       while (1)
 498         {
 499           if (aloop->num >= mn)
 500             VEC_quick_push (int, li->to_visit, aloop->num);
 501
 502           if (aloop->next)
 503             {
 504               for (aloop = aloop->next;
 505                    aloop->inner != NULL;
 506                    aloop = aloop->inner)
 507                 continue;
 508             }
 509           else if (!aloop->outer)
 510             break;
 511           else
 512             aloop = aloop->outer;
 513         }
 514     }
 515   else
 516     {
 517       /* Push the loops to LI->TO_VISIT in preorder.  */
 518       aloop = current_loops->tree_root;
 519       while (1)
 520         {
 521           if (aloop->num >= mn)
 522             VEC_quick_push (int, li->to_visit, aloop->num);
 523
 524           if (aloop->inner != NULL)
 525             aloop = aloop->inner;
 526           else
 527             {
 528               while (aloop != NULL && aloop->next == NULL)
 529                 aloop = aloop->outer;
 530               if (aloop == NULL)
 531                 break;
 532               aloop = aloop->next;
 533             }
 534         }
 535     }
 536
 537   fel_next (li, loop);
 538 }
 539
 540 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
 541   for (fel_init (&(LI), &(LOOP), FLAGS); \
 542        (LOOP); \
 543        fel_next (&(LI), &(LOOP)))
 544
 545 #define FOR_EACH_LOOP_BREAK(LI) \
 546   { \
 547     VEC_free (int, heap, (LI)->to_visit); \
 548     break; \
 549   }
 550
 551 /* The properties of the target.  */
 552
 553 extern unsigned target_avail_regs;      /* Number of available registers.  */
 554 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 555 extern unsigned target_small_cost;      /* The cost for register when there
 556                                            is a free one.  */
 557 extern unsigned target_pres_cost;       /* The cost for register when there are
 558                                            not too many free ones.  */
 559 extern unsigned target_spill_cost;      /* The cost for register when we need
 560                                            to spill.  */
 561
 562 /* Register pressure estimation for induction variable optimizations & loop
 563    invariant motion.  */
 564 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 565 extern void init_set_costs (void);
 566
 567 /* Loop optimizer initialization.  */
 568 extern void loop_optimizer_init (unsigned);
 569 extern void loop_optimizer_finalize (void);
 570
 571 /* Optimization passes.  */
 572 extern void unswitch_loops (void);
 573
 574 enum
 575 {
 576   UAP_PEEL = 1,         /* Enables loop peeling.  */
 577   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 578   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 579 };
 580
 581 extern void unroll_and_peel_loops (int);
 582 extern void doloop_optimize_loops (void);
 583 extern void move_loop_invariants (void);
 584
 585 #endif /* GCC_CFGLOOP_H */