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 GTY (()) lpt_decision {
  42   enum lpt_dec decision;
  43   unsigned times;
  44 };
  45
  46 /* The structure describing a bound on number of iterations of a loop.  */
  47
  48 struct GTY ((chain_next ("%h.next"))) nb_iter_bound {
  49   /* The statement STMT is executed at most ...  */
  50   gimple stmt;
  51
  52   /* ... BOUND + 1 times (BOUND must be an unsigned constant).
  53      The + 1 is added for the following reasons:
  54
  55      a) 0 would otherwise be unused, while we would need to care more about
  56         overflows (as MAX + 1 is sometimes produced as the estimate on number
  57         of executions of STMT).
  58      b) it is consistent with the result of number_of_iterations_exit.  */
  59   double_int bound;
  60
  61   /* True if the statement will cause the loop to be leaved the (at most)
  62      BOUND + 1-st time it is executed, that is, all the statements after it
  63      are executed at most BOUND times.  */
  64   bool is_exit;
  65
  66   /* The next bound in the list.  */
  67   struct nb_iter_bound *next;
  68 };
  69
  70 /* Description of the loop exit.  */
  71
  72 struct GTY (()) loop_exit {
  73   /* The exit edge.  */
  74   struct edge_def *e;
  75
  76   /* Previous and next exit in the list of the exits of the loop.  */
  77   struct loop_exit *prev;
  78   struct loop_exit *next;
  79
  80   /* Next element in the list of loops from that E exits.  */
  81   struct loop_exit *next_e;
  82 };
  83
  84 typedef struct loop *loop_p;
  85 DEF_VEC_P (loop_p);
  86 DEF_VEC_ALLOC_P (loop_p, heap);
  87 DEF_VEC_ALLOC_P (loop_p, gc);
  88
  89 /* An integer estimation of the number of iterations.  Estimate_state
  90    describes what is the state of the estimation.  */
  91 enum loop_estimation
  92 {
  93   /* Estimate was not computed yet.  */
  94   EST_NOT_COMPUTED,
  95   /* Estimate is ready.  */
  96   EST_AVAILABLE
  97 };
  98
  99 /* Structure to hold information for each natural loop.  */
 100 struct GTY ((chain_next ("%h.next"))) loop {
 101   /* Index into loops array.  */
 102   int num;
 103
 104   /* Number of loop insns.  */
 105   unsigned ninsns;
 106
 107   /* Basic block of loop header.  */
 108   struct basic_block_def *header;
 109
 110   /* Basic block of loop latch.  */
 111   struct basic_block_def *latch;
 112
 113   /* For loop unrolling/peeling decision.  */
 114   struct lpt_decision lpt_decision;
 115
 116   /* Average number of executed insns per iteration.  */
 117   unsigned av_ninsns;
 118
 119   /* Number of blocks contained within the loop.  */
 120   unsigned num_nodes;
 121
 122   /* Superloops of the loop, starting with the outermost loop.  */
 123   VEC (loop_p, gc) *superloops;
 124
 125   /* The first inner (child) loop or NULL if innermost loop.  */
 126   struct loop *inner;
 127
 128   /* Link to the next (sibling) loop.  */
 129   struct loop *next;
 130
 131   /* Auxiliary info specific to a pass.  */
 132   PTR GTY ((skip (""))) aux;
 133
 134   /* The number of times the latch of the loop is executed.
 135      This is an INTEGER_CST or an expression containing symbolic
 136      names.  Don't access this field directly:
 137      number_of_latch_executions computes and caches the computed
 138      information in this field.  */
 139   tree nb_iterations;
 140
 141   /* An integer guaranteed to bound the number of iterations of the loop
 142      from above.  */
 143   double_int nb_iterations_upper_bound;
 144
 145   /* An integer giving the expected number of iterations of the loop.  */
 146   double_int nb_iterations_estimate;
 147
 148   bool any_upper_bound;
 149   bool any_estimate;
 150
 151   /* An integer estimation of the number of iterations.  Estimate_state
 152      describes what is the state of the estimation.  */
 153   enum loop_estimation estimate_state;
 154
 155   /* Upper bound on number of iterations of a loop.  */
 156   struct nb_iter_bound *bounds;
 157
 158   /* Head of the cyclic list of the exits of the loop.  */
 159   struct loop_exit *exits;
 160
 161   /* True if the loop can be parallel.  */
 162   bool can_be_parallel;
 163
 164   /* The single induction variable of the loop when the loop is in
 165      normal form.  */
 166   tree single_iv;
 167 };
 168
 169 /* Flags for state of loop structure.  */
 170 enum
 171 {
 172   LOOPS_HAVE_PREHEADERS = 1,
 173   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 174   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
 175   LOOPS_HAVE_RECORDED_EXITS = 8,
 176   LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16,
 177   LOOP_CLOSED_SSA = 32,
 178   LOOPS_NEED_FIXUP = 64,
 179   LOOPS_HAVE_FALLTHRU_PREHEADERS = 128
 180 };
 181
 182 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 183                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 184 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
 185
 186 /* Structure to hold CFG information about natural loops within a function.  */
 187 struct GTY (()) loops {
 188   /* State of loops.  */
 189   int state;
 190
 191   /* Array of the loops.  */
 192   VEC (loop_p, gc) *larray;
 193
 194   /* Maps edges to the list of their descriptions as loop exits.  Edges
 195      whose sources or destinations have loop_father == NULL (which may
 196      happen during the cfg manipulations) should not appear in EXITS.  */
 197   htab_t GTY((param_is (struct loop_exit))) exits;
 198
 199   /* Pointer to root of loop hierarchy tree.  */
 200   struct loop *tree_root;
 201 };
 202
 203 /* Loop recognition.  */
 204 extern int flow_loops_find (struct loops *);
 205 extern void disambiguate_loops_with_multiple_latches (void);
 206 extern void flow_loops_free (struct loops *);
 207 extern void flow_loops_dump (FILE *,
 208                              void (*)(const struct loop *, FILE *, int), int);
 209 extern void flow_loop_dump (const struct loop *, FILE *,
 210                             void (*)(const struct loop *, FILE *, int), int);
 211 struct loop *alloc_loop (void);
 212 extern void flow_loop_free (struct loop *);
 213 int flow_loop_nodes_find (basic_block, struct loop *);
 214 void fix_loop_structure (bitmap changed_bbs);
 215 bool mark_irreducible_loops (void);
 216 void release_recorded_exits (void);
 217 void record_loop_exits (void);
 218 void rescan_loop_exit (edge, bool, bool);
 219
 220 /* Loop data structure manipulation/querying.  */
 221 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 222 extern void flow_loop_tree_node_remove (struct loop *);
 223 extern void add_loop (struct loop *, struct loop *);
 224 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 225 extern bool flow_bb_inside_loop_p (const struct loop *, const_basic_block);
 226 extern struct loop * find_common_loop (struct loop *, struct loop *);
 227 struct loop *superloop_at_depth (struct loop *, unsigned);
 228 struct eni_weights_d;
 229 extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *);
 230 extern int num_loop_insns (const struct loop *);
 231 extern int average_num_loop_insns (const struct loop *);
 232 extern unsigned get_loop_level (const struct loop *);
 233 extern bool loop_exit_edge_p (const struct loop *, const_edge);
 234 extern bool is_loop_exit (struct loop *, basic_block);
 235 extern void mark_loop_exit_edges (void);
 236
 237 /* Loops & cfg manipulation.  */
 238 extern basic_block *get_loop_body (const struct loop *);
 239 extern unsigned get_loop_body_with_size (const struct loop *, basic_block *,
 240                                          unsigned);
 241 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 242 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 243 extern basic_block *get_loop_body_in_custom_order (const struct loop *,
 244                                int (*) (const void *, const void *));
 245
 246 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
 247 edge single_exit (const struct loop *);
 248 extern unsigned num_loop_branches (const struct loop *);
 249
 250 extern edge loop_preheader_edge (const struct loop *);
 251 extern edge loop_latch_edge (const struct loop *);
 252
 253 extern void add_bb_to_loop (basic_block, struct loop *);
 254 extern void remove_bb_from_loops (basic_block);
 255
 256 extern void cancel_loop_tree (struct loop *);
 257 extern void delete_loop (struct loop *);
 258
 259 enum
 260 {
 261   CP_SIMPLE_PREHEADERS = 1,
 262   CP_FALLTHRU_PREHEADERS = 2
 263 };
 264
 265 basic_block create_preheader (struct loop *, int);
 266 extern void create_preheaders (int);
 267 extern void force_single_succ_latches (void);
 268
 269 extern void verify_loop_structure (void);
 270
 271 /* Loop analysis.  */
 272 extern bool just_once_each_iteration_p (const struct loop *, const_basic_block);
 273 gcov_type expected_loop_iterations_unbounded (const struct loop *);
 274 extern unsigned expected_loop_iterations (const struct loop *);
 275 extern rtx doloop_condition_get (rtx);
 276
 277 void estimate_numbers_of_iterations_loop (struct loop *);
 278 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool);
 279 bool estimated_loop_iterations (struct loop *, bool, double_int *);
 280
 281 /* Loop manipulation.  */
 282 extern bool can_duplicate_loop_p (const struct loop *loop);
 283
 284 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 285                                            duplicate_loop_to_header_edge.  */
 286 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 287                                            field of newly create BB.  */
 288 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 289                                            a complete peeling.  */
 290
 291 extern edge create_empty_if_region_on_edge (edge, tree);
 292 extern struct loop *create_empty_loop_on_edge (edge, tree, tree, tree, tree,
 293                                                tree *, tree *, struct loop *);
 294 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 295 extern void duplicate_subloops (struct loop *, struct loop *);
 296 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 297                                            unsigned, sbitmap, edge,
 298                                            VEC (edge, heap) **, int);
 299 extern struct loop *loopify (edge, edge,
 300                              basic_block, edge, edge, bool,
 301                              unsigned, unsigned);
 302 struct loop * loop_version (struct loop *, void *,
 303                             basic_block *, unsigned, unsigned, unsigned, bool);
 304 extern bool remove_path (edge);
 305 void scale_loop_frequencies (struct loop *, int, int);
 306
 307 /* Induction variable analysis.  */
 308
 309 /* The description of induction variable.  The things are a bit complicated
 310    due to need to handle subregs and extends.  The value of the object described
 311    by it can be obtained as follows (all computations are done in extend_mode):
 312
 313    Value in i-th iteration is
 314      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 315
 316    If first_special is true, the value in the first iteration is
 317      delta + mult * base
 318
 319    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 320      subreg_{mode} (base + i * step)
 321
 322    The get_iv_value function can be used to obtain these expressions.
 323
 324    ??? Add a third mode field that would specify the mode in that inner
 325    computation is done, which would enable it to be different from the
 326    outer one?  */
 327
 328 struct rtx_iv
 329 {
 330   /* Its base and step (mode of base and step is supposed to be extend_mode,
 331      see the description above).  */
 332   rtx base, step;
 333
 334   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 335   enum rtx_code extend;
 336
 337   /* Operations applied in the extended mode.  */
 338   rtx delta, mult;
 339
 340   /* The mode it is extended to.  */
 341   enum machine_mode extend_mode;
 342
 343   /* The mode the variable iterates in.  */
 344   enum machine_mode mode;
 345
 346   /* Whether the first iteration needs to be handled specially.  */
 347   unsigned first_special : 1;
 348 };
 349
 350 /* The description of an exit from the loop and of the number of iterations
 351    till we take the exit.  */
 352
 353 struct niter_desc
 354 {
 355   /* The edge out of the loop.  */
 356   edge out_edge;
 357
 358   /* The other edge leading from the condition.  */
 359   edge in_edge;
 360
 361   /* True if we are able to say anything about number of iterations of the
 362      loop.  */
 363   bool simple_p;
 364
 365   /* True if the loop iterates the constant number of times.  */
 366   bool const_iter;
 367
 368   /* Number of iterations if constant.  */
 369   unsigned HOST_WIDEST_INT niter;
 370
 371   /* Upper bound on the number of iterations.  */
 372   unsigned HOST_WIDEST_INT niter_max;
 373
 374   /* Assumptions under that the rest of the information is valid.  */
 375   rtx assumptions;
 376
 377   /* Assumptions under that the loop ends before reaching the latch,
 378      even if value of niter_expr says otherwise.  */
 379   rtx noloop_assumptions;
 380
 381   /* Condition under that the loop is infinite.  */
 382   rtx infinite;
 383
 384   /* Whether the comparison is signed.  */
 385   bool signed_p;
 386
 387   /* The mode in that niter_expr should be computed.  */
 388   enum machine_mode mode;
 389
 390   /* The number of iterations of the loop.  */
 391   rtx niter_expr;
 392 };
 393
 394 extern void iv_analysis_loop_init (struct loop *);
 395 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 396 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 397 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 398 extern rtx get_iv_value (struct rtx_iv *, rtx);
 399 extern bool biv_p (rtx, rtx);
 400 extern void find_simple_exit (struct loop *, struct niter_desc *);
 401 extern void iv_analysis_done (void);
 402
 403 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 404 extern void free_simple_loop_desc (struct loop *loop);
 405
 406 static inline struct niter_desc *
 407 simple_loop_desc (struct loop *loop)
 408 {
 409   return (struct niter_desc *) loop->aux;
 410 }
 411
 412 /* Accessors for the loop structures.  */
 413
 414 /* Returns the loop with index NUM from current_loops.  */
 415
 416 static inline struct loop *
 417 get_loop (unsigned num)
 418 {
 419   return VEC_index (loop_p, current_loops->larray, num);
 420 }
 421
 422 /* Returns the number of superloops of LOOP.  */
 423
 424 static inline unsigned
 425 loop_depth (const struct loop *loop)
 426 {
 427   return VEC_length (loop_p, loop->superloops);
 428 }
 429
 430 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
 431    loop.  */
 432
 433 static inline struct loop *
 434 loop_outer (const struct loop *loop)
 435 {
 436   unsigned n = VEC_length (loop_p, loop->superloops);
 437
 438   if (n == 0)
 439     return NULL;
 440
 441   return VEC_index (loop_p, loop->superloops, n - 1);
 442 }
 443
 444 /* Returns the list of loops in current_loops.  */
 445
 446 static inline VEC (loop_p, gc) *
 447 get_loops (void)
 448 {
 449   if (!current_loops)
 450     return NULL;
 451
 452   return current_loops->larray;
 453 }
 454
 455 /* Returns the number of loops in current_loops (including the removed
 456    ones and the fake loop that forms the root of the loop tree).  */
 457
 458 static inline unsigned
 459 number_of_loops (void)
 460 {
 461   if (!current_loops)
 462     return 0;
 463
 464   return VEC_length (loop_p, current_loops->larray);
 465 }
 466
 467 /* Returns true if state of the loops satisfies all properties
 468    described by FLAGS.  */
 469
 470 static inline bool
 471 loops_state_satisfies_p (unsigned flags)
 472 {
 473   return (current_loops->state & flags) == flags;
 474 }
 475
 476 /* Sets FLAGS to the loops state.  */
 477
 478 static inline void
 479 loops_state_set (unsigned flags)
 480 {
 481   current_loops->state |= flags;
 482 }
 483
 484 /* Clears FLAGS from the loops state.  */
 485
 486 static inline void
 487 loops_state_clear (unsigned flags)
 488 {
 489   if (!current_loops)
 490     return;
 491   current_loops->state &= ~flags;
 492 }
 493
 494 /* Loop iterators.  */
 495
 496 /* Flags for loop iteration.  */
 497
 498 enum li_flags
 499 {
 500   LI_INCLUDE_ROOT = 1,          /* Include the fake root of the loop tree.  */
 501   LI_FROM_INNERMOST = 2,        /* Iterate over the loops in the reverse order,
 502                                    starting from innermost ones.  */
 503   LI_ONLY_INNERMOST = 4         /* Iterate only over innermost loops.  */
 504 };
 505
 506 /* The iterator for loops.  */
 507
 508 typedef struct
 509 {
 510   /* The list of loops to visit.  */
 511   VEC(int,heap) *to_visit;
 512
 513   /* The index of the actual loop.  */
 514   unsigned idx;
 515 } loop_iterator;
 516
 517 static inline void
 518 fel_next (loop_iterator *li, loop_p *loop)
 519 {
 520   int anum;
 521
 522   while (VEC_iterate (int, li->to_visit, li->idx, anum))
 523     {
 524       li->idx++;
 525       *loop = get_loop (anum);
 526       if (*loop)
 527         return;
 528     }
 529
 530   VEC_free (int, heap, li->to_visit);
 531   *loop = NULL;
 532 }
 533
 534 static inline void
 535 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
 536 {
 537   struct loop *aloop;
 538   unsigned i;
 539   int mn;
 540
 541   li->idx = 0;
 542   if (!current_loops)
 543     {
 544       li->to_visit = NULL;
 545       *loop = NULL;
 546       return;
 547     }
 548
 549   li->to_visit = VEC_alloc (int, heap, number_of_loops ());
 550   mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
 551
 552   if (flags & LI_ONLY_INNERMOST)
 553     {
 554       for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
 555         if (aloop != NULL
 556             && aloop->inner == NULL
 557             && aloop->num >= mn)
 558           VEC_quick_push (int, li->to_visit, aloop->num);
 559     }
 560   else if (flags & LI_FROM_INNERMOST)
 561     {
 562       /* Push the loops to LI->TO_VISIT in postorder.  */
 563       for (aloop = current_loops->tree_root;
 564            aloop->inner != NULL;
 565            aloop = aloop->inner)
 566         continue;
 567
 568       while (1)
 569         {
 570           if (aloop->num >= mn)
 571             VEC_quick_push (int, li->to_visit, aloop->num);
 572
 573           if (aloop->next)
 574             {
 575               for (aloop = aloop->next;
 576                    aloop->inner != NULL;
 577                    aloop = aloop->inner)
 578                 continue;
 579             }
 580           else if (!loop_outer (aloop))
 581             break;
 582           else
 583             aloop = loop_outer (aloop);
 584         }
 585     }
 586   else
 587     {
 588       /* Push the loops to LI->TO_VISIT in preorder.  */
 589       aloop = current_loops->tree_root;
 590       while (1)
 591         {
 592           if (aloop->num >= mn)
 593             VEC_quick_push (int, li->to_visit, aloop->num);
 594
 595           if (aloop->inner != NULL)
 596             aloop = aloop->inner;
 597           else
 598             {
 599               while (aloop != NULL && aloop->next == NULL)
 600                 aloop = loop_outer (aloop);
 601               if (aloop == NULL)
 602                 break;
 603               aloop = aloop->next;
 604             }
 605         }
 606     }
 607
 608   fel_next (li, loop);
 609 }
 610
 611 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
 612   for (fel_init (&(LI), &(LOOP), FLAGS); \
 613        (LOOP); \
 614        fel_next (&(LI), &(LOOP)))
 615
 616 #define FOR_EACH_LOOP_BREAK(LI) \
 617   { \
 618     VEC_free (int, heap, (LI)->to_visit); \
 619     break; \
 620   }
 621
 622 /* The properties of the target.  */
 623
 624 extern unsigned target_avail_regs;
 625 extern unsigned target_res_regs;
 626 extern unsigned target_reg_cost [2];
 627 extern unsigned target_spill_cost [2];
 628
 629 /* Register pressure estimation for induction variable optimizations & loop
 630    invariant motion.  */
 631 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool);
 632 extern void init_set_costs (void);
 633
 634 /* Loop optimizer initialization.  */
 635 extern void loop_optimizer_init (unsigned);
 636 extern void loop_optimizer_finalize (void);
 637
 638 /* Optimization passes.  */
 639 extern void unswitch_loops (void);
 640
 641 enum
 642 {
 643   UAP_PEEL = 1,         /* Enables loop peeling.  */
 644   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 645   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 646 };
 647
 648 extern void unroll_and_peel_loops (int);
 649 extern void doloop_optimize_loops (void);
 650 extern void move_loop_invariants (void);
 651 extern bool finite_loop_p (struct loop *);
 652
 653 #endif /* GCC_CFGLOOP_H */