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   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   /* 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   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 loops GTY (())
 184 {
 185   /* State of loops.  */
 186   int state;
 187
 188   /* Array of the loops.  */
 189   VEC (loop_p, gc) *larray;
 190
 191   /* Maps edges to the list of their descriptions as loop exits.  Edges
 192      whose sources or destinations have loop_father == NULL (which may
 193      happen during the cfg manipulations) should not appear in EXITS.  */
 194   htab_t GTY((param_is (struct loop_exit))) exits;
 195
 196   /* Pointer to root of loop hierarchy tree.  */
 197   struct loop *tree_root;
 198 };
 199
 200 /* Loop recognition.  */
 201 extern int flow_loops_find (struct loops *);
 202 extern void disambiguate_loops_with_multiple_latches (void);
 203 extern void flow_loops_free (struct loops *);
 204 extern void flow_loops_dump (FILE *,
 205                              void (*)(const struct loop *, FILE *, int), int);
 206 extern void flow_loop_dump (const struct loop *, FILE *,
 207                             void (*)(const struct loop *, FILE *, int), int);
 208 struct loop *alloc_loop (void);
 209 extern void flow_loop_free (struct loop *);
 210 int flow_loop_nodes_find (basic_block, struct loop *);
 211 void fix_loop_structure (bitmap changed_bbs);
 212 void mark_irreducible_loops (void);
 213 void release_recorded_exits (void);
 214 void record_loop_exits (void);
 215 void rescan_loop_exit (edge, bool, bool);
 216
 217 /* Loop data structure manipulation/querying.  */
 218 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 219 extern void flow_loop_tree_node_remove (struct loop *);
 220 extern void add_loop (struct loop *, struct loop *);
 221 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 222 extern bool flow_bb_inside_loop_p (const struct loop *, const_basic_block);
 223 extern struct loop * find_common_loop (struct loop *, struct loop *);
 224 struct loop *superloop_at_depth (struct loop *, unsigned);
 225 struct eni_weights_d;
 226 extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *);
 227 extern int num_loop_insns (const struct loop *);
 228 extern int average_num_loop_insns (const struct loop *);
 229 extern unsigned get_loop_level (const struct loop *);
 230 extern bool loop_exit_edge_p (const struct loop *, const_edge);
 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 struct loop * duplicate_loop (struct loop *, struct loop *);
 288 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 289                                            unsigned, sbitmap, edge,
 290                                            VEC (edge, heap) **, int);
 291 extern struct loop *loopify (edge, edge,
 292                              basic_block, edge, edge, bool,
 293                              unsigned, unsigned);
 294 struct loop * loop_version (struct loop *, void *,
 295                             basic_block *, unsigned, unsigned, unsigned, bool);
 296 extern bool remove_path (edge);
 297 void scale_loop_frequencies (struct loop *, int, int);
 298
 299 /* Induction variable analysis.  */
 300
 301 /* The description of induction variable.  The things are a bit complicated
 302    due to need to handle subregs and extends.  The value of the object described
 303    by it can be obtained as follows (all computations are done in extend_mode):
 304
 305    Value in i-th iteration is
 306      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 307
 308    If first_special is true, the value in the first iteration is
 309      delta + mult * base
 310
 311    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 312      subreg_{mode} (base + i * step)
 313
 314    The get_iv_value function can be used to obtain these expressions.
 315
 316    ??? Add a third mode field that would specify the mode in that inner
 317    computation is done, which would enable it to be different from the
 318    outer one?  */
 319
 320 struct rtx_iv
 321 {
 322   /* Its base and step (mode of base and step is supposed to be extend_mode,
 323      see the description above).  */
 324   rtx base, step;
 325
 326   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 327   enum rtx_code extend;
 328
 329   /* Operations applied in the extended mode.  */
 330   rtx delta, mult;
 331
 332   /* The mode it is extended to.  */
 333   enum machine_mode extend_mode;
 334
 335   /* The mode the variable iterates in.  */
 336   enum machine_mode mode;
 337
 338   /* Whether the first iteration needs to be handled specially.  */
 339   unsigned first_special : 1;
 340 };
 341
 342 /* The description of an exit from the loop and of the number of iterations
 343    till we take the exit.  */
 344
 345 struct niter_desc
 346 {
 347   /* The edge out of the loop.  */
 348   edge out_edge;
 349
 350   /* The other edge leading from the condition.  */
 351   edge in_edge;
 352
 353   /* True if we are able to say anything about number of iterations of the
 354      loop.  */
 355   bool simple_p;
 356
 357   /* True if the loop iterates the constant number of times.  */
 358   bool const_iter;
 359
 360   /* Number of iterations if constant.  */
 361   unsigned HOST_WIDEST_INT niter;
 362
 363   /* Upper bound on the number of iterations.  */
 364   unsigned HOST_WIDEST_INT niter_max;
 365
 366   /* Assumptions under that the rest of the information is valid.  */
 367   rtx assumptions;
 368
 369   /* Assumptions under that the loop ends before reaching the latch,
 370      even if value of niter_expr says otherwise.  */
 371   rtx noloop_assumptions;
 372
 373   /* Condition under that the loop is infinite.  */
 374   rtx infinite;
 375
 376   /* Whether the comparison is signed.  */
 377   bool signed_p;
 378
 379   /* The mode in that niter_expr should be computed.  */
 380   enum machine_mode mode;
 381
 382   /* The number of iterations of the loop.  */
 383   rtx niter_expr;
 384 };
 385
 386 extern void iv_analysis_loop_init (struct loop *);
 387 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 388 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 389 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 390 extern rtx get_iv_value (struct rtx_iv *, rtx);
 391 extern bool biv_p (rtx, rtx);
 392 extern void find_simple_exit (struct loop *, struct niter_desc *);
 393 extern void iv_analysis_done (void);
 394
 395 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 396 extern void free_simple_loop_desc (struct loop *loop);
 397
 398 static inline struct niter_desc *
 399 simple_loop_desc (struct loop *loop)
 400 {
 401   return (struct niter_desc *) loop->aux;
 402 }
 403
 404 /* Accessors for the loop structures.  */
 405
 406 /* Returns the loop with index NUM from current_loops.  */
 407
 408 static inline struct loop *
 409 get_loop (unsigned num)
 410 {
 411   return VEC_index (loop_p, current_loops->larray, num);
 412 }
 413
 414 /* Returns the number of superloops of LOOP.  */
 415
 416 static inline unsigned
 417 loop_depth (const struct loop *loop)
 418 {
 419   return VEC_length (loop_p, loop->superloops);
 420 }
 421
 422 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
 423    loop.  */
 424
 425 static inline struct loop *
 426 loop_outer (const struct loop *loop)
 427 {
 428   unsigned n = VEC_length (loop_p, loop->superloops);
 429
 430   if (n == 0)
 431     return NULL;
 432
 433   return VEC_index (loop_p, loop->superloops, n - 1);
 434 }
 435
 436 /* Returns the list of loops in current_loops.  */
 437
 438 static inline VEC (loop_p, gc) *
 439 get_loops (void)
 440 {
 441   if (!current_loops)
 442     return NULL;
 443
 444   return current_loops->larray;
 445 }
 446
 447 /* Returns the number of loops in current_loops (including the removed
 448    ones and the fake loop that forms the root of the loop tree).  */
 449
 450 static inline unsigned
 451 number_of_loops (void)
 452 {
 453   if (!current_loops)
 454     return 0;
 455
 456   return VEC_length (loop_p, current_loops->larray);
 457 }
 458
 459 /* Returns true if state of the loops satisfies all properties
 460    described by FLAGS.  */
 461
 462 static inline bool
 463 loops_state_satisfies_p (unsigned flags)
 464 {
 465   return (current_loops->state & flags) == flags;
 466 }
 467
 468 /* Sets FLAGS to the loops state.  */
 469
 470 static inline void
 471 loops_state_set (unsigned flags)
 472 {
 473   current_loops->state |= flags;
 474 }
 475
 476 /* Clears FLAGS from the loops state.  */
 477
 478 static inline void
 479 loops_state_clear (unsigned flags)
 480 {
 481   if (!current_loops)
 482     return;
 483   current_loops->state &= ~flags;
 484 }
 485
 486 /* Loop iterators.  */
 487
 488 /* Flags for loop iteration.  */
 489
 490 enum li_flags
 491 {
 492   LI_INCLUDE_ROOT = 1,          /* Include the fake root of the loop tree.  */
 493   LI_FROM_INNERMOST = 2,        /* Iterate over the loops in the reverse order,
 494                                    starting from innermost ones.  */
 495   LI_ONLY_INNERMOST = 4         /* Iterate only over innermost loops.  */
 496 };
 497
 498 /* The iterator for loops.  */
 499
 500 typedef struct
 501 {
 502   /* The list of loops to visit.  */
 503   VEC(int,heap) *to_visit;
 504
 505   /* The index of the actual loop.  */
 506   unsigned idx;
 507 } loop_iterator;
 508
 509 static inline void
 510 fel_next (loop_iterator *li, loop_p *loop)
 511 {
 512   int anum;
 513
 514   while (VEC_iterate (int, li->to_visit, li->idx, anum))
 515     {
 516       li->idx++;
 517       *loop = get_loop (anum);
 518       if (*loop)
 519         return;
 520     }
 521
 522   VEC_free (int, heap, li->to_visit);
 523   *loop = NULL;
 524 }
 525
 526 static inline void
 527 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
 528 {
 529   struct loop *aloop;
 530   unsigned i;
 531   int mn;
 532
 533   li->idx = 0;
 534   if (!current_loops)
 535     {
 536       li->to_visit = NULL;
 537       *loop = NULL;
 538       return;
 539     }
 540
 541   li->to_visit = VEC_alloc (int, heap, number_of_loops ());
 542   mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
 543
 544   if (flags & LI_ONLY_INNERMOST)
 545     {
 546       for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
 547         if (aloop != NULL
 548             && aloop->inner == NULL
 549             && aloop->num >= mn)
 550           VEC_quick_push (int, li->to_visit, aloop->num);
 551     }
 552   else if (flags & LI_FROM_INNERMOST)
 553     {
 554       /* Push the loops to LI->TO_VISIT in postorder.  */
 555       for (aloop = current_loops->tree_root;
 556            aloop->inner != NULL;
 557            aloop = aloop->inner)
 558         continue;
 559
 560       while (1)
 561         {
 562           if (aloop->num >= mn)
 563             VEC_quick_push (int, li->to_visit, aloop->num);
 564
 565           if (aloop->next)
 566             {
 567               for (aloop = aloop->next;
 568                    aloop->inner != NULL;
 569                    aloop = aloop->inner)
 570                 continue;
 571             }
 572           else if (!loop_outer (aloop))
 573             break;
 574           else
 575             aloop = loop_outer (aloop);
 576         }
 577     }
 578   else
 579     {
 580       /* Push the loops to LI->TO_VISIT in preorder.  */
 581       aloop = current_loops->tree_root;
 582       while (1)
 583         {
 584           if (aloop->num >= mn)
 585             VEC_quick_push (int, li->to_visit, aloop->num);
 586
 587           if (aloop->inner != NULL)
 588             aloop = aloop->inner;
 589           else
 590             {
 591               while (aloop != NULL && aloop->next == NULL)
 592                 aloop = loop_outer (aloop);
 593               if (aloop == NULL)
 594                 break;
 595               aloop = aloop->next;
 596             }
 597         }
 598     }
 599
 600   fel_next (li, loop);
 601 }
 602
 603 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
 604   for (fel_init (&(LI), &(LOOP), FLAGS); \
 605        (LOOP); \
 606        fel_next (&(LI), &(LOOP)))
 607
 608 #define FOR_EACH_LOOP_BREAK(LI) \
 609   { \
 610     VEC_free (int, heap, (LI)->to_visit); \
 611     break; \
 612   }
 613
 614 /* The properties of the target.  */
 615
 616 extern unsigned target_avail_regs;
 617 extern unsigned target_res_regs;
 618 extern unsigned target_reg_cost [2];
 619 extern unsigned target_spill_cost [2];
 620
 621 /* Register pressure estimation for induction variable optimizations & loop
 622    invariant motion.  */
 623 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool);
 624 extern void init_set_costs (void);
 625
 626 /* Loop optimizer initialization.  */
 627 extern void loop_optimizer_init (unsigned);
 628 extern void loop_optimizer_finalize (void);
 629
 630 /* Optimization passes.  */
 631 extern void unswitch_loops (void);
 632
 633 enum
 634 {
 635   UAP_PEEL = 1,         /* Enables loop peeling.  */
 636   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 637   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 638 };
 639
 640 extern void unroll_and_peel_loops (int);
 641 extern void doloop_optimize_loops (void);
 642 extern void move_loop_invariants (void);
 643
 644 #endif /* GCC_CFGLOOP_H */