contrib/gcc-4.4/gcc/cfgloop.h

   1 /* Natural loop functions
   2    Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
   3    2005, 2006, 2007, 2008, 2009  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 3, 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 COPYING3.  If not see
  19 <http://www.gnu.org/licenses/>.  */
  20
  21 #ifndef GCC_CFGLOOP_H
  22 #define GCC_CFGLOOP_H
  23
  24 #include "basic-block.h"
  25 /* For rtx_code.  */
  26 #include "rtl.h"
  27 #include "vecprim.h"
  28 #include "double-int.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 GTY (())
  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 GTY ((chain_next ("%h.next")))
  50 {
  51   /* The statement STMT is executed at most ...  */
  52   gimple 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 GTY (())
  75 {
  76   /* The exit edge.  */
  77   struct edge_def *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 typedef struct loop *loop_p;
  88 DEF_VEC_P (loop_p);
  89 DEF_VEC_ALLOC_P (loop_p, heap);
  90 DEF_VEC_ALLOC_P (loop_p, gc);
  91
  92 /* An integer estimation of the number of iterations.  Estimate_state
  93    describes what is the state of the estimation.  */
  94 enum loop_estimation
  95 {
  96   /* Estimate was not computed yet.  */
  97   EST_NOT_COMPUTED,
  98   /* Estimate is ready.  */
  99   EST_AVAILABLE
 100 };
 101
 102 /* Structure to hold information for each natural loop.  */
 103 struct loop GTY ((chain_next ("%h.next")))
 104 {
 105   /* Index into loops array.  */
 106   int num;
 107
 108   /* Number of loop insns.  */
 109   unsigned ninsns;
 110
 111   /* Basic block of loop header.  */
 112   struct basic_block_def *header;
 113
 114   /* Basic block of loop latch.  */
 115   struct basic_block_def *latch;
 116
 117   /* For loop unrolling/peeling decision.  */
 118   struct lpt_decision lpt_decision;
 119
 120   /* Average number of executed insns per iteration.  */
 121   unsigned av_ninsns;
 122
 123   /* Number of blocks contained within the loop.  */
 124   unsigned num_nodes;
 125
 126   /* Superloops of the loop, starting with the outermost loop.  */
 127   VEC (loop_p, gc) *superloops;
 128
 129   /* The first inner (child) loop or NULL if innermost loop.  */
 130   struct loop *inner;
 131
 132   /* Link to the next (sibling) loop.  */
 133   struct loop *next;
 134
 135   /* Auxiliary info specific to a pass.  */
 136   PTR GTY ((skip (""))) 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 guaranteed to bound the number of iterations of the loop
 146      from above.  */
 147   double_int nb_iterations_upper_bound;
 148
 149   /* An integer giving the expected number of iterations of the loop.  */
 150   double_int nb_iterations_estimate;
 151
 152   bool any_upper_bound;
 153   bool any_estimate;
 154
 155   /* An integer estimation of the number of iterations.  Estimate_state
 156      describes what is the state of the estimation.  */
 157   enum loop_estimation estimate_state;
 158
 159   /* Upper bound on number of iterations of a loop.  */
 160   struct nb_iter_bound *bounds;
 161
 162   /* Head of the cyclic list of the exits of the loop.  */
 163   struct loop_exit *exits;
 164 };
 165
 166 /* Flags for state of loop structure.  */
 167 enum
 168 {
 169   LOOPS_HAVE_PREHEADERS = 1,
 170   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 171   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
 172   LOOPS_HAVE_RECORDED_EXITS = 8,
 173   LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16,
 174   LOOP_CLOSED_SSA = 32,
 175   LOOPS_NEED_FIXUP = 64,
 176   LOOPS_HAVE_FALLTHRU_PREHEADERS = 128
 177 };
 178
 179 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 180                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 181 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
 182
 183 /* Structure to hold CFG information about natural loops within a function.  */
 184 struct loops GTY (())
 185 {
 186   /* State of loops.  */
 187   int state;
 188
 189   /* Array of the loops.  */
 190   VEC (loop_p, gc) *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 GTY((param_is (struct loop_exit))) 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 (const struct loop *);
 229 extern int average_num_loop_insns (const struct loop *);
 230 extern unsigned get_loop_level (const struct loop *);
 231 extern bool loop_exit_edge_p (const struct loop *, const_edge);
 232 extern bool is_loop_exit (struct loop *, basic_block);
 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 basic_block *get_loop_body_in_custom_order (const struct loop *,
 242                                int (*) (const void *, const void *));
 243
 244 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
 245 edge single_exit (const struct loop *);
 246 extern unsigned num_loop_branches (const struct loop *);
 247
 248 extern edge loop_preheader_edge (const struct loop *);
 249 extern edge loop_latch_edge (const struct loop *);
 250
 251 extern void add_bb_to_loop (basic_block, struct loop *);
 252 extern void remove_bb_from_loops (basic_block);
 253
 254 extern void cancel_loop_tree (struct loop *);
 255 extern void delete_loop (struct loop *);
 256
 257 enum
 258 {
 259   CP_SIMPLE_PREHEADERS = 1,
 260   CP_FALLTHRU_PREHEADERS = 2
 261 };
 262
 263 basic_block create_preheader (struct loop *, int);
 264 extern void create_preheaders (int);
 265 extern void force_single_succ_latches (void);
 266
 267 extern void verify_loop_structure (void);
 268
 269 /* Loop analysis.  */
 270 extern bool just_once_each_iteration_p (const struct loop *, const_basic_block);
 271 gcov_type expected_loop_iterations_unbounded (const struct loop *);
 272 extern unsigned expected_loop_iterations (const struct loop *);
 273 extern rtx doloop_condition_get (rtx);
 274
 275 void estimate_numbers_of_iterations_loop (struct loop *);
 276 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool);
 277 bool estimated_loop_iterations (struct loop *, bool, double_int *);
 278
 279 /* Loop manipulation.  */
 280 extern bool can_duplicate_loop_p (const struct loop *loop);
 281
 282 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 283                                            duplicate_loop_to_header_edge.  */
 284 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 285                                            field of newly create BB.  */
 286 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 287                                            a complete peeling.  */
 288
 289 extern edge create_empty_if_region_on_edge (edge, tree);
 290 extern struct loop *create_empty_loop_on_edge (edge, tree, tree, tree, tree,
 291                                                tree *, struct loop *);
 292 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 293 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 294                                            unsigned, sbitmap, edge,
 295                                            VEC (edge, heap) **, int);
 296 extern struct loop *loopify (edge, edge,
 297                              basic_block, edge, edge, bool,
 298                              unsigned, unsigned);
 299 struct loop * loop_version (struct loop *, void *,
 300                             basic_block *, unsigned, unsigned, unsigned, bool);
 301 extern bool remove_path (edge);
 302 void scale_loop_frequencies (struct loop *, int, int);
 303
 304 /* Induction variable analysis.  */
 305
 306 /* The description of induction variable.  The things are a bit complicated
 307    due to need to handle subregs and extends.  The value of the object described
 308    by it can be obtained as follows (all computations are done in extend_mode):
 309
 310    Value in i-th iteration is
 311      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 312
 313    If first_special is true, the value in the first iteration is
 314      delta + mult * base
 315
 316    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 317      subreg_{mode} (base + i * step)
 318
 319    The get_iv_value function can be used to obtain these expressions.
 320
 321    ??? Add a third mode field that would specify the mode in that inner
 322    computation is done, which would enable it to be different from the
 323    outer one?  */
 324
 325 struct rtx_iv
 326 {
 327   /* Its base and step (mode of base and step is supposed to be extend_mode,
 328      see the description above).  */
 329   rtx base, step;
 330
 331   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 332   enum rtx_code extend;
 333
 334   /* Operations applied in the extended mode.  */
 335   rtx delta, mult;
 336
 337   /* The mode it is extended to.  */
 338   enum machine_mode extend_mode;
 339
 340   /* The mode the variable iterates in.  */
 341   enum machine_mode mode;
 342
 343   /* Whether the first iteration needs to be handled specially.  */
 344   unsigned first_special : 1;
 345 };
 346
 347 /* The description of an exit from the loop and of the number of iterations
 348    till we take the exit.  */
 349
 350 struct niter_desc
 351 {
 352   /* The edge out of the loop.  */
 353   edge out_edge;
 354
 355   /* The other edge leading from the condition.  */
 356   edge in_edge;
 357
 358   /* True if we are able to say anything about number of iterations of the
 359      loop.  */
 360   bool simple_p;
 361
 362   /* True if the loop iterates the constant number of times.  */
 363   bool const_iter;
 364
 365   /* Number of iterations if constant.  */
 366   unsigned HOST_WIDEST_INT niter;
 367
 368   /* Upper bound on the number of iterations.  */
 369   unsigned HOST_WIDEST_INT niter_max;
 370
 371   /* Assumptions under that the rest of the information is valid.  */
 372   rtx assumptions;
 373
 374   /* Assumptions under that the loop ends before reaching the latch,
 375      even if value of niter_expr says otherwise.  */
 376   rtx noloop_assumptions;
 377
 378   /* Condition under that the loop is infinite.  */
 379   rtx infinite;
 380
 381   /* Whether the comparison is signed.  */
 382   bool signed_p;
 383
 384   /* The mode in that niter_expr should be computed.  */
 385   enum machine_mode mode;
 386
 387   /* The number of iterations of the loop.  */
 388   rtx niter_expr;
 389 };
 390
 391 extern void iv_analysis_loop_init (struct loop *);
 392 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 393 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 394 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 395 extern rtx get_iv_value (struct rtx_iv *, rtx);
 396 extern bool biv_p (rtx, rtx);
 397 extern void find_simple_exit (struct loop *, struct niter_desc *);
 398 extern void iv_analysis_done (void);
 399
 400 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 401 extern void free_simple_loop_desc (struct loop *loop);
 402
 403 static inline struct niter_desc *
 404 simple_loop_desc (struct loop *loop)
 405 {
 406   return (struct niter_desc *) loop->aux;
 407 }
 408
 409 /* Accessors for the loop structures.  */
 410
 411 /* Returns the loop with index NUM from current_loops.  */
 412
 413 static inline struct loop *
 414 get_loop (unsigned num)
 415 {
 416   return VEC_index (loop_p, current_loops->larray, num);
 417 }
 418
 419 /* Returns the number of superloops of LOOP.  */
 420
 421 static inline unsigned
 422 loop_depth (const struct loop *loop)
 423 {
 424   return VEC_length (loop_p, loop->superloops);
 425 }
 426
 427 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
 428    loop.  */
 429
 430 static inline struct loop *
 431 loop_outer (const struct loop *loop)
 432 {
 433   unsigned n = VEC_length (loop_p, loop->superloops);
 434
 435   if (n == 0)
 436     return NULL;
 437
 438   return VEC_index (loop_p, loop->superloops, n - 1);
 439 }
 440
 441 /* Returns the list of loops in current_loops.  */
 442
 443 static inline VEC (loop_p, gc) *
 444 get_loops (void)
 445 {
 446   if (!current_loops)
 447     return NULL;
 448
 449   return current_loops->larray;
 450 }
 451
 452 /* Returns the number of loops in current_loops (including the removed
 453    ones and the fake loop that forms the root of the loop tree).  */
 454
 455 static inline unsigned
 456 number_of_loops (void)
 457 {
 458   if (!current_loops)
 459     return 0;
 460
 461   return VEC_length (loop_p, current_loops->larray);
 462 }
 463
 464 /* Returns true if state of the loops satisfies all properties
 465    described by FLAGS.  */
 466
 467 static inline bool
 468 loops_state_satisfies_p (unsigned flags)
 469 {
 470   return (current_loops->state & flags) == flags;
 471 }
 472
 473 /* Sets FLAGS to the loops state.  */
 474
 475 static inline void
 476 loops_state_set (unsigned flags)
 477 {
 478   current_loops->state |= flags;
 479 }
 480
 481 /* Clears FLAGS from the loops state.  */
 482
 483 static inline void
 484 loops_state_clear (unsigned flags)
 485 {
 486   if (!current_loops)
 487     return;
 488   current_loops->state &= ~flags;
 489 }
 490
 491 /* Loop iterators.  */
 492
 493 /* Flags for loop iteration.  */
 494
 495 enum li_flags
 496 {
 497   LI_INCLUDE_ROOT = 1,          /* Include the fake root of the loop tree.  */
 498   LI_FROM_INNERMOST = 2,        /* Iterate over the loops in the reverse order,
 499                                    starting from innermost ones.  */
 500   LI_ONLY_INNERMOST = 4         /* Iterate only over innermost loops.  */
 501 };
 502
 503 /* The iterator for loops.  */
 504
 505 typedef struct
 506 {
 507   /* The list of loops to visit.  */
 508   VEC(int,heap) *to_visit;
 509
 510   /* The index of the actual loop.  */
 511   unsigned idx;
 512 } loop_iterator;
 513
 514 static inline void
 515 fel_next (loop_iterator *li, loop_p *loop)
 516 {
 517   int anum;
 518
 519   while (VEC_iterate (int, li->to_visit, li->idx, anum))
 520     {
 521       li->idx++;
 522       *loop = get_loop (anum);
 523       if (*loop)
 524         return;
 525     }
 526
 527   VEC_free (int, heap, li->to_visit);
 528   *loop = NULL;
 529 }
 530
 531 static inline void
 532 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
 533 {
 534   struct loop *aloop;
 535   unsigned i;
 536   int mn;
 537
 538   li->idx = 0;
 539   if (!current_loops)
 540     {
 541       li->to_visit = NULL;
 542       *loop = NULL;
 543       return;
 544     }
 545
 546   li->to_visit = VEC_alloc (int, heap, number_of_loops ());
 547   mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
 548
 549   if (flags & LI_ONLY_INNERMOST)
 550     {
 551       for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
 552         if (aloop != NULL
 553             && aloop->inner == NULL
 554             && aloop->num >= mn)
 555           VEC_quick_push (int, li->to_visit, aloop->num);
 556     }
 557   else if (flags & LI_FROM_INNERMOST)
 558     {
 559       /* Push the loops to LI->TO_VISIT in postorder.  */
 560       for (aloop = current_loops->tree_root;
 561            aloop->inner != NULL;
 562            aloop = aloop->inner)
 563         continue;
 564
 565       while (1)
 566         {
 567           if (aloop->num >= mn)
 568             VEC_quick_push (int, li->to_visit, aloop->num);
 569
 570           if (aloop->next)
 571             {
 572               for (aloop = aloop->next;
 573                    aloop->inner != NULL;
 574                    aloop = aloop->inner)
 575                 continue;
 576             }
 577           else if (!loop_outer (aloop))
 578             break;
 579           else
 580             aloop = loop_outer (aloop);
 581         }
 582     }
 583   else
 584     {
 585       /* Push the loops to LI->TO_VISIT in preorder.  */
 586       aloop = current_loops->tree_root;
 587       while (1)
 588         {
 589           if (aloop->num >= mn)
 590             VEC_quick_push (int, li->to_visit, aloop->num);
 591
 592           if (aloop->inner != NULL)
 593             aloop = aloop->inner;
 594           else
 595             {
 596               while (aloop != NULL && aloop->next == NULL)
 597                 aloop = loop_outer (aloop);
 598               if (aloop == NULL)
 599                 break;
 600               aloop = aloop->next;
 601             }
 602         }
 603     }
 604
 605   fel_next (li, loop);
 606 }
 607
 608 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
 609   for (fel_init (&(LI), &(LOOP), FLAGS); \
 610        (LOOP); \
 611        fel_next (&(LI), &(LOOP)))
 612
 613 #define FOR_EACH_LOOP_BREAK(LI) \
 614   { \
 615     VEC_free (int, heap, (LI)->to_visit); \
 616     break; \
 617   }
 618
 619 /* The properties of the target.  */
 620
 621 extern unsigned target_avail_regs;
 622 extern unsigned target_res_regs;
 623 extern unsigned target_reg_cost [2];
 624 extern unsigned target_spill_cost [2];
 625
 626 /* Register pressure estimation for induction variable optimizations & loop
 627    invariant motion.  */
 628 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool);
 629 extern void init_set_costs (void);
 630
 631 /* Loop optimizer initialization.  */
 632 extern void loop_optimizer_init (unsigned);
 633 extern void loop_optimizer_finalize (void);
 634
 635 /* Optimization passes.  */
 636 extern void unswitch_loops (void);
 637
 638 enum
 639 {
 640   UAP_PEEL = 1,         /* Enables loop peeling.  */
 641   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 642   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 643 };
 644
 645 extern void unroll_and_peel_loops (int);
 646 extern void doloop_optimize_loops (void);
 647 extern void move_loop_invariants (void);
 648
 649 #endif /* GCC_CFGLOOP_H */