gcc/cfgloop.h

   1 /* Natural loop functions
   2    Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
   3    2005, 2006, 2007  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   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 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   /* Basic block of loop header.  */
 109   struct basic_block_def *header;
 110
 111   /* Basic block of loop latch.  */
 112   struct basic_block_def *latch;
 113
 114   /* For loop unrolling/peeling decision.  */
 115   struct lpt_decision lpt_decision;
 116
 117   /* Number of loop insns.  */
 118   unsigned ninsns;
 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 estimation of the number of iterations.  Estimate_state
 146      describes what is the state of the estimation.  */
 147   enum loop_estimation 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   LOOPS_NEED_FIXUP = 64
 175 };
 176
 177 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 178                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 179 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
 180
 181 /* Structure to hold CFG information about natural loops within a function.  */
 182 struct loops GTY (())
 183 {
 184   /* State of loops.  */
 185   int state;
 186
 187   /* Array of the loops.  */
 188   VEC (loop_p, gc) *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 GTY((param_is (struct loop_exit))) 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 disambiguate_loops_with_multiple_latches (void);
 202 extern void flow_loops_free (struct loops *);
 203 extern void flow_loops_dump (FILE *,
 204                              void (*)(const struct loop *, FILE *, int), int);
 205 extern void flow_loop_dump (const struct loop *, FILE *,
 206                             void (*)(const struct loop *, FILE *, int), int);
 207 struct loop *alloc_loop (void);
 208 extern void flow_loop_free (struct loop *);
 209 int flow_loop_nodes_find (basic_block, struct loop *);
 210 void fix_loop_structure (bitmap changed_bbs);
 211 void mark_irreducible_loops (void);
 212 void release_recorded_exits (void);
 213 void record_loop_exits (void);
 214 void rescan_loop_exit (edge, bool, bool);
 215
 216 /* Loop data structure manipulation/querying.  */
 217 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 218 extern void flow_loop_tree_node_remove (struct loop *);
 219 extern void add_loop (struct loop *, struct loop *);
 220 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 221 extern bool flow_bb_inside_loop_p (const struct loop *, const_basic_block);
 222 extern struct loop * find_common_loop (struct loop *, struct loop *);
 223 struct loop *superloop_at_depth (struct loop *, unsigned);
 224 struct eni_weights_d;
 225 extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *);
 226 extern int num_loop_insns (const struct loop *);
 227 extern int average_num_loop_insns (const struct loop *);
 228 extern unsigned get_loop_level (const struct loop *);
 229 extern bool loop_exit_edge_p (const struct loop *, const_edge);
 230 extern void mark_loop_exit_edges (void);
 231
 232 /* Loops & cfg manipulation.  */
 233 extern basic_block *get_loop_body (const struct loop *);
 234 extern unsigned get_loop_body_with_size (const struct loop *, basic_block *,
 235                                          unsigned);
 236 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 237 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 238 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
 239 edge single_exit (const struct loop *);
 240 extern unsigned num_loop_branches (const struct loop *);
 241
 242 extern edge loop_preheader_edge (const struct loop *);
 243 extern edge loop_latch_edge (const struct loop *);
 244
 245 extern void add_bb_to_loop (basic_block, struct loop *);
 246 extern void remove_bb_from_loops (basic_block);
 247
 248 extern void cancel_loop_tree (struct loop *);
 249 extern void delete_loop (struct loop *);
 250
 251 enum
 252 {
 253   CP_SIMPLE_PREHEADERS = 1
 254 };
 255
 256 basic_block create_preheader (struct loop *, int);
 257 extern void create_preheaders (int);
 258 extern void force_single_succ_latches (void);
 259
 260 extern void verify_loop_structure (void);
 261
 262 /* Loop analysis.  */
 263 extern bool just_once_each_iteration_p (const struct loop *, const_basic_block);
 264 gcov_type expected_loop_iterations_unbounded (const struct loop *);
 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 bool estimated_loop_iterations (struct loop *, bool, double_int *);
 271
 272 /* Loop manipulation.  */
 273 extern bool can_duplicate_loop_p (const struct loop *loop);
 274
 275 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 276                                            duplicate_loop_to_header_edge.  */
 277 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 278                                            field of newly create BB.  */
 279 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 280                                            a complete peeling.  */
 281
 282 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 283 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 284                                            unsigned, sbitmap, edge,
 285                                            VEC (edge, heap) **, int);
 286 extern struct loop *loopify (edge, edge,
 287                              basic_block, edge, edge, bool,
 288                              unsigned, unsigned);
 289 struct loop * loop_version (struct loop *, void *,
 290                             basic_block *, unsigned, unsigned, unsigned, bool);
 291 extern bool remove_path (edge);
 292 void scale_loop_frequencies (struct loop *, int, int);
 293
 294 /* Induction variable analysis.  */
 295
 296 /* The description of induction variable.  The things are a bit complicated
 297    due to need to handle subregs and extends.  The value of the object described
 298    by it can be obtained as follows (all computations are done in extend_mode):
 299
 300    Value in i-th iteration is
 301      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 302
 303    If first_special is true, the value in the first iteration is
 304      delta + mult * base
 305
 306    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 307      subreg_{mode} (base + i * step)
 308
 309    The get_iv_value function can be used to obtain these expressions.
 310
 311    ??? Add a third mode field that would specify the mode in that inner
 312    computation is done, which would enable it to be different from the
 313    outer one?  */
 314
 315 struct rtx_iv
 316 {
 317   /* Its base and step (mode of base and step is supposed to be extend_mode,
 318      see the description above).  */
 319   rtx base, step;
 320
 321   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 322   enum rtx_code extend;
 323
 324   /* Operations applied in the extended mode.  */
 325   rtx delta, mult;
 326
 327   /* The mode it is extended to.  */
 328   enum machine_mode extend_mode;
 329
 330   /* The mode the variable iterates in.  */
 331   enum machine_mode mode;
 332
 333   /* Whether the first iteration needs to be handled specially.  */
 334   unsigned first_special : 1;
 335 };
 336
 337 /* The description of an exit from the loop and of the number of iterations
 338    till we take the exit.  */
 339
 340 struct niter_desc
 341 {
 342   /* The edge out of the loop.  */
 343   edge out_edge;
 344
 345   /* The other edge leading from the condition.  */
 346   edge in_edge;
 347
 348   /* True if we are able to say anything about number of iterations of the
 349      loop.  */
 350   bool simple_p;
 351
 352   /* True if the loop iterates the constant number of times.  */
 353   bool const_iter;
 354
 355   /* Number of iterations if constant.  */
 356   unsigned HOST_WIDEST_INT niter;
 357
 358   /* Upper bound on the number of iterations.  */
 359   unsigned HOST_WIDEST_INT niter_max;
 360
 361   /* Assumptions under that the rest of the information is valid.  */
 362   rtx assumptions;
 363
 364   /* Assumptions under that the loop ends before reaching the latch,
 365      even if value of niter_expr says otherwise.  */
 366   rtx noloop_assumptions;
 367
 368   /* Condition under that the loop is infinite.  */
 369   rtx infinite;
 370
 371   /* Whether the comparison is signed.  */
 372   bool signed_p;
 373
 374   /* The mode in that niter_expr should be computed.  */
 375   enum machine_mode mode;
 376
 377   /* The number of iterations of the loop.  */
 378   rtx niter_expr;
 379 };
 380
 381 extern void iv_analysis_loop_init (struct loop *);
 382 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 383 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 384 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 385 extern rtx get_iv_value (struct rtx_iv *, rtx);
 386 extern bool biv_p (rtx, rtx);
 387 extern void find_simple_exit (struct loop *, struct niter_desc *);
 388 extern void iv_analysis_done (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 number of superloops of LOOP.  */
 410
 411 static inline unsigned
 412 loop_depth (const struct loop *loop)
 413 {
 414   return VEC_length (loop_p, loop->superloops);
 415 }
 416
 417 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
 418    loop.  */
 419
 420 static inline struct loop *
 421 loop_outer (const struct loop *loop)
 422 {
 423   unsigned n = VEC_length (loop_p, loop->superloops);
 424
 425   if (n == 0)
 426     return NULL;
 427
 428   return VEC_index (loop_p, loop->superloops, n - 1);
 429 }
 430
 431 /* Returns the list of loops in current_loops.  */
 432
 433 static inline VEC (loop_p, gc) *
 434 get_loops (void)
 435 {
 436   if (!current_loops)
 437     return NULL;
 438
 439   return current_loops->larray;
 440 }
 441
 442 /* Returns the number of loops in current_loops (including the removed
 443    ones and the fake loop that forms the root of the loop tree).  */
 444
 445 static inline unsigned
 446 number_of_loops (void)
 447 {
 448   if (!current_loops)
 449     return 0;
 450
 451   return VEC_length (loop_p, current_loops->larray);
 452 }
 453
 454 /* Returns true if state of the loops satisfies all properties
 455    described by FLAGS.  */
 456
 457 static inline bool
 458 loops_state_satisfies_p (unsigned flags)
 459 {
 460   return (current_loops->state & flags) == flags;
 461 }
 462
 463 /* Sets FLAGS to the loops state.  */
 464
 465 static inline void
 466 loops_state_set (unsigned flags)
 467 {
 468   current_loops->state |= flags;
 469 }
 470
 471 /* Clears FLAGS from the loops state.  */
 472
 473 static inline void
 474 loops_state_clear (unsigned flags)
 475 {
 476   if (!current_loops)
 477     return;
 478   current_loops->state &= ~flags;
 479 }
 480
 481 /* Loop iterators.  */
 482
 483 /* Flags for loop iteration.  */
 484
 485 enum li_flags
 486 {
 487   LI_INCLUDE_ROOT = 1,          /* Include the fake root of the loop tree.  */
 488   LI_FROM_INNERMOST = 2,        /* Iterate over the loops in the reverse order,
 489                                    starting from innermost ones.  */
 490   LI_ONLY_INNERMOST = 4         /* Iterate only over innermost loops.  */
 491 };
 492
 493 /* The iterator for loops.  */
 494
 495 typedef struct
 496 {
 497   /* The list of loops to visit.  */
 498   VEC(int,heap) *to_visit;
 499
 500   /* The index of the actual loop.  */
 501   unsigned idx;
 502 } loop_iterator;
 503
 504 static inline void
 505 fel_next (loop_iterator *li, loop_p *loop)
 506 {
 507   int anum;
 508
 509   while (VEC_iterate (int, li->to_visit, li->idx, anum))
 510     {
 511       li->idx++;
 512       *loop = get_loop (anum);
 513       if (*loop)
 514         return;
 515     }
 516
 517   VEC_free (int, heap, li->to_visit);
 518   *loop = NULL;
 519 }
 520
 521 static inline void
 522 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
 523 {
 524   struct loop *aloop;
 525   unsigned i;
 526   int mn;
 527
 528   li->idx = 0;
 529   if (!current_loops)
 530     {
 531       li->to_visit = NULL;
 532       *loop = NULL;
 533       return;
 534     }
 535
 536   li->to_visit = VEC_alloc (int, heap, number_of_loops ());
 537   mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
 538
 539   if (flags & LI_ONLY_INNERMOST)
 540     {
 541       for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
 542         if (aloop != NULL
 543             && aloop->inner == NULL
 544             && aloop->num >= mn)
 545           VEC_quick_push (int, li->to_visit, aloop->num);
 546     }
 547   else if (flags & LI_FROM_INNERMOST)
 548     {
 549       /* Push the loops to LI->TO_VISIT in postorder.  */
 550       for (aloop = current_loops->tree_root;
 551            aloop->inner != NULL;
 552            aloop = aloop->inner)
 553         continue;
 554
 555       while (1)
 556         {
 557           if (aloop->num >= mn)
 558             VEC_quick_push (int, li->to_visit, aloop->num);
 559
 560           if (aloop->next)
 561             {
 562               for (aloop = aloop->next;
 563                    aloop->inner != NULL;
 564                    aloop = aloop->inner)
 565                 continue;
 566             }
 567           else if (!loop_outer (aloop))
 568             break;
 569           else
 570             aloop = loop_outer (aloop);
 571         }
 572     }
 573   else
 574     {
 575       /* Push the loops to LI->TO_VISIT in preorder.  */
 576       aloop = current_loops->tree_root;
 577       while (1)
 578         {
 579           if (aloop->num >= mn)
 580             VEC_quick_push (int, li->to_visit, aloop->num);
 581
 582           if (aloop->inner != NULL)
 583             aloop = aloop->inner;
 584           else
 585             {
 586               while (aloop != NULL && aloop->next == NULL)
 587                 aloop = loop_outer (aloop);
 588               if (aloop == NULL)
 589                 break;
 590               aloop = aloop->next;
 591             }
 592         }
 593     }
 594
 595   fel_next (li, loop);
 596 }
 597
 598 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
 599   for (fel_init (&(LI), &(LOOP), FLAGS); \
 600        (LOOP); \
 601        fel_next (&(LI), &(LOOP)))
 602
 603 #define FOR_EACH_LOOP_BREAK(LI) \
 604   { \
 605     VEC_free (int, heap, (LI)->to_visit); \
 606     break; \
 607   }
 608
 609 /* The properties of the target.  */
 610
 611 extern unsigned target_avail_regs;
 612 extern unsigned target_res_regs;
 613 extern unsigned target_reg_cost;
 614 extern unsigned target_spill_cost;
 615
 616 /* Register pressure estimation for induction variable optimizations & loop
 617    invariant motion.  */
 618 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned);
 619 extern void init_set_costs (void);
 620
 621 /* Loop optimizer initialization.  */
 622 extern void loop_optimizer_init (unsigned);
 623 extern void loop_optimizer_finalize (void);
 624
 625 /* Optimization passes.  */
 626 extern void unswitch_loops (void);
 627
 628 enum
 629 {
 630   UAP_PEEL = 1,         /* Enables loop peeling.  */
 631   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 632   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 633 };
 634
 635 extern void unroll_and_peel_loops (int);
 636 extern void doloop_optimize_loops (void);
 637 extern void move_loop_invariants (void);
 638
 639 #endif /* GCC_CFGLOOP_H */