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
 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   LOOPS_HAVE_FALLTHRU_PREHEADERS = 128
 176 };
 177
 178 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 179                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 180 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
 181
 182 /* Structure to hold CFG information about natural loops within a function.  */
 183 struct GTY (()) loops {
 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 bool 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 bool is_loop_exit (struct loop *, basic_block);
 231 extern void mark_loop_exit_edges (void);
 232
 233 /* Loops & cfg manipulation.  */
 234 extern basic_block *get_loop_body (const struct loop *);
 235 extern unsigned get_loop_body_with_size (const struct loop *, basic_block *,
 236                                          unsigned);
 237 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 238 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 239 extern basic_block *get_loop_body_in_custom_order (const struct loop *,
 240                                int (*) (const void *, const void *));
 241
 242 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
 243 edge single_exit (const struct loop *);
 244 extern unsigned num_loop_branches (const struct loop *);
 245
 246 extern edge loop_preheader_edge (const struct loop *);
 247 extern edge loop_latch_edge (const struct loop *);
 248
 249 extern void add_bb_to_loop (basic_block, struct loop *);
 250 extern void remove_bb_from_loops (basic_block);
 251
 252 extern void cancel_loop_tree (struct loop *);
 253 extern void delete_loop (struct loop *);
 254
 255 enum
 256 {
 257   CP_SIMPLE_PREHEADERS = 1,
 258   CP_FALLTHRU_PREHEADERS = 2
 259 };
 260
 261 basic_block create_preheader (struct loop *, int);
 262 extern void create_preheaders (int);
 263 extern void force_single_succ_latches (void);
 264
 265 extern void verify_loop_structure (void);
 266
 267 /* Loop analysis.  */
 268 extern bool just_once_each_iteration_p (const struct loop *, const_basic_block);
 269 gcov_type expected_loop_iterations_unbounded (const struct loop *);
 270 extern unsigned expected_loop_iterations (const struct loop *);
 271 extern rtx doloop_condition_get (rtx);
 272
 273 void estimate_numbers_of_iterations_loop (struct loop *);
 274 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool);
 275 bool estimated_loop_iterations (struct loop *, bool, double_int *);
 276
 277 /* Loop manipulation.  */
 278 extern bool can_duplicate_loop_p (const struct loop *loop);
 279
 280 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 281                                            duplicate_loop_to_header_edge.  */
 282 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 283                                            field of newly create BB.  */
 284 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 285                                            a complete peeling.  */
 286
 287 extern edge create_empty_if_region_on_edge (edge, tree);
 288 extern struct loop *create_empty_loop_on_edge (edge, tree, tree, tree, tree,
 289                                                tree *, tree *, struct loop *);
 290 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 291 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 292                                            unsigned, sbitmap, edge,
 293                                            VEC (edge, heap) **, int);
 294 extern struct loop *loopify (edge, edge,
 295                              basic_block, edge, edge, bool,
 296                              unsigned, unsigned);
 297 struct loop * loop_version (struct loop *, void *,
 298                             basic_block *, unsigned, unsigned, unsigned, bool);
 299 extern bool remove_path (edge);
 300 void scale_loop_frequencies (struct loop *, int, int);
 301
 302 /* Induction variable analysis.  */
 303
 304 /* The description of induction variable.  The things are a bit complicated
 305    due to need to handle subregs and extends.  The value of the object described
 306    by it can be obtained as follows (all computations are done in extend_mode):
 307
 308    Value in i-th iteration is
 309      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 310
 311    If first_special is true, the value in the first iteration is
 312      delta + mult * base
 313
 314    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 315      subreg_{mode} (base + i * step)
 316
 317    The get_iv_value function can be used to obtain these expressions.
 318
 319    ??? Add a third mode field that would specify the mode in that inner
 320    computation is done, which would enable it to be different from the
 321    outer one?  */
 322
 323 struct rtx_iv
 324 {
 325   /* Its base and step (mode of base and step is supposed to be extend_mode,
 326      see the description above).  */
 327   rtx base, step;
 328
 329   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 330   enum rtx_code extend;
 331
 332   /* Operations applied in the extended mode.  */
 333   rtx delta, mult;
 334
 335   /* The mode it is extended to.  */
 336   enum machine_mode extend_mode;
 337
 338   /* The mode the variable iterates in.  */
 339   enum machine_mode mode;
 340
 341   /* Whether the first iteration needs to be handled specially.  */
 342   unsigned first_special : 1;
 343 };
 344
 345 /* The description of an exit from the loop and of the number of iterations
 346    till we take the exit.  */
 347
 348 struct niter_desc
 349 {
 350   /* The edge out of the loop.  */
 351   edge out_edge;
 352
 353   /* The other edge leading from the condition.  */
 354   edge in_edge;
 355
 356   /* True if we are able to say anything about number of iterations of the
 357      loop.  */
 358   bool simple_p;
 359
 360   /* True if the loop iterates the constant number of times.  */
 361   bool const_iter;
 362
 363   /* Number of iterations if constant.  */
 364   unsigned HOST_WIDEST_INT niter;
 365
 366   /* Upper bound on the number of iterations.  */
 367   unsigned HOST_WIDEST_INT niter_max;
 368
 369   /* Assumptions under that the rest of the information is valid.  */
 370   rtx assumptions;
 371
 372   /* Assumptions under that the loop ends before reaching the latch,
 373      even if value of niter_expr says otherwise.  */
 374   rtx noloop_assumptions;
 375
 376   /* Condition under that the loop is infinite.  */
 377   rtx infinite;
 378
 379   /* Whether the comparison is signed.  */
 380   bool signed_p;
 381
 382   /* The mode in that niter_expr should be computed.  */
 383   enum machine_mode mode;
 384
 385   /* The number of iterations of the loop.  */
 386   rtx niter_expr;
 387 };
 388
 389 extern void iv_analysis_loop_init (struct loop *);
 390 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 391 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 392 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 393 extern rtx get_iv_value (struct rtx_iv *, rtx);
 394 extern bool biv_p (rtx, rtx);
 395 extern void find_simple_exit (struct loop *, struct niter_desc *);
 396 extern void iv_analysis_done (void);
 397
 398 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 399 extern void free_simple_loop_desc (struct loop *loop);
 400
 401 static inline struct niter_desc *
 402 simple_loop_desc (struct loop *loop)
 403 {
 404   return (struct niter_desc *) loop->aux;
 405 }
 406
 407 /* Accessors for the loop structures.  */
 408
 409 /* Returns the loop with index NUM from current_loops.  */
 410
 411 static inline struct loop *
 412 get_loop (unsigned num)
 413 {
 414   return VEC_index (loop_p, current_loops->larray, num);
 415 }
 416
 417 /* Returns the number of superloops of LOOP.  */
 418
 419 static inline unsigned
 420 loop_depth (const struct loop *loop)
 421 {
 422   return VEC_length (loop_p, loop->superloops);
 423 }
 424
 425 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
 426    loop.  */
 427
 428 static inline struct loop *
 429 loop_outer (const struct loop *loop)
 430 {
 431   unsigned n = VEC_length (loop_p, loop->superloops);
 432
 433   if (n == 0)
 434     return NULL;
 435
 436   return VEC_index (loop_p, loop->superloops, n - 1);
 437 }
 438
 439 /* Returns the list of loops in current_loops.  */
 440
 441 static inline VEC (loop_p, gc) *
 442 get_loops (void)
 443 {
 444   if (!current_loops)
 445     return NULL;
 446
 447   return current_loops->larray;
 448 }
 449
 450 /* Returns the number of loops in current_loops (including the removed
 451    ones and the fake loop that forms the root of the loop tree).  */
 452
 453 static inline unsigned
 454 number_of_loops (void)
 455 {
 456   if (!current_loops)
 457     return 0;
 458
 459   return VEC_length (loop_p, current_loops->larray);
 460 }
 461
 462 /* Returns true if state of the loops satisfies all properties
 463    described by FLAGS.  */
 464
 465 static inline bool
 466 loops_state_satisfies_p (unsigned flags)
 467 {
 468   return (current_loops->state & flags) == flags;
 469 }
 470
 471 /* Sets FLAGS to the loops state.  */
 472
 473 static inline void
 474 loops_state_set (unsigned flags)
 475 {
 476   current_loops->state |= flags;
 477 }
 478
 479 /* Clears FLAGS from the loops state.  */
 480
 481 static inline void
 482 loops_state_clear (unsigned flags)
 483 {
 484   if (!current_loops)
 485     return;
 486   current_loops->state &= ~flags;
 487 }
 488
 489 /* Loop iterators.  */
 490
 491 /* Flags for loop iteration.  */
 492
 493 enum li_flags
 494 {
 495   LI_INCLUDE_ROOT = 1,          /* Include the fake root of the loop tree.  */
 496   LI_FROM_INNERMOST = 2,        /* Iterate over the loops in the reverse order,
 497                                    starting from innermost ones.  */
 498   LI_ONLY_INNERMOST = 4         /* Iterate only over innermost loops.  */
 499 };
 500
 501 /* The iterator for loops.  */
 502
 503 typedef struct
 504 {
 505   /* The list of loops to visit.  */
 506   VEC(int,heap) *to_visit;
 507
 508   /* The index of the actual loop.  */
 509   unsigned idx;
 510 } loop_iterator;
 511
 512 static inline void
 513 fel_next (loop_iterator *li, loop_p *loop)
 514 {
 515   int anum;
 516
 517   while (VEC_iterate (int, li->to_visit, li->idx, anum))
 518     {
 519       li->idx++;
 520       *loop = get_loop (anum);
 521       if (*loop)
 522         return;
 523     }
 524
 525   VEC_free (int, heap, li->to_visit);
 526   *loop = NULL;
 527 }
 528
 529 static inline void
 530 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
 531 {
 532   struct loop *aloop;
 533   unsigned i;
 534   int mn;
 535
 536   li->idx = 0;
 537   if (!current_loops)
 538     {
 539       li->to_visit = NULL;
 540       *loop = NULL;
 541       return;
 542     }
 543
 544   li->to_visit = VEC_alloc (int, heap, number_of_loops ());
 545   mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
 546
 547   if (flags & LI_ONLY_INNERMOST)
 548     {
 549       for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
 550         if (aloop != NULL
 551             && aloop->inner == NULL
 552             && aloop->num >= mn)
 553           VEC_quick_push (int, li->to_visit, aloop->num);
 554     }
 555   else if (flags & LI_FROM_INNERMOST)
 556     {
 557       /* Push the loops to LI->TO_VISIT in postorder.  */
 558       for (aloop = current_loops->tree_root;
 559            aloop->inner != NULL;
 560            aloop = aloop->inner)
 561         continue;
 562
 563       while (1)
 564         {
 565           if (aloop->num >= mn)
 566             VEC_quick_push (int, li->to_visit, aloop->num);
 567
 568           if (aloop->next)
 569             {
 570               for (aloop = aloop->next;
 571                    aloop->inner != NULL;
 572                    aloop = aloop->inner)
 573                 continue;
 574             }
 575           else if (!loop_outer (aloop))
 576             break;
 577           else
 578             aloop = loop_outer (aloop);
 579         }
 580     }
 581   else
 582     {
 583       /* Push the loops to LI->TO_VISIT in preorder.  */
 584       aloop = current_loops->tree_root;
 585       while (1)
 586         {
 587           if (aloop->num >= mn)
 588             VEC_quick_push (int, li->to_visit, aloop->num);
 589
 590           if (aloop->inner != NULL)
 591             aloop = aloop->inner;
 592           else
 593             {
 594               while (aloop != NULL && aloop->next == NULL)
 595                 aloop = loop_outer (aloop);
 596               if (aloop == NULL)
 597                 break;
 598               aloop = aloop->next;
 599             }
 600         }
 601     }
 602
 603   fel_next (li, loop);
 604 }
 605
 606 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
 607   for (fel_init (&(LI), &(LOOP), FLAGS); \
 608        (LOOP); \
 609        fel_next (&(LI), &(LOOP)))
 610
 611 #define FOR_EACH_LOOP_BREAK(LI) \
 612   { \
 613     VEC_free (int, heap, (LI)->to_visit); \
 614     break; \
 615   }
 616
 617 /* The properties of the target.  */
 618
 619 extern unsigned target_avail_regs;
 620 extern unsigned target_res_regs;
 621 extern unsigned target_reg_cost [2];
 622 extern unsigned target_spill_cost [2];
 623
 624 /* Register pressure estimation for induction variable optimizations & loop
 625    invariant motion.  */
 626 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool);
 627 extern void init_set_costs (void);
 628
 629 /* Loop optimizer initialization.  */
 630 extern void loop_optimizer_init (unsigned);
 631 extern void loop_optimizer_finalize (void);
 632
 633 /* Optimization passes.  */
 634 extern void unswitch_loops (void);
 635
 636 enum
 637 {
 638   UAP_PEEL = 1,         /* Enables loop peeling.  */
 639   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 640   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 641 };
 642
 643 extern void unroll_and_peel_loops (int);
 644 extern void doloop_optimize_loops (void);
 645 extern void move_loop_invariants (void);
 646 extern bool finite_loop_p (struct loop *);
 647
 648 #endif /* GCC_CFGLOOP_H */