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