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, 2010  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 #include "vecprim.h"
  26 #include "double-int.h"
  27
  28 #include "bitmap.h"
  29 #include "sbitmap.h"
  30
  31 /* Structure to hold decision about unrolling/peeling.  */
  32 enum lpt_dec
  33 {
  34   LPT_NONE,
  35   LPT_PEEL_COMPLETELY,
  36   LPT_PEEL_SIMPLE,
  37   LPT_UNROLL_CONSTANT,
  38   LPT_UNROLL_RUNTIME,
  39   LPT_UNROLL_STUPID
  40 };
  41
  42 struct GTY (()) lpt_decision {
  43   enum lpt_dec decision;
  44   unsigned times;
  45 };
  46
  47 /* The type of extend applied to an IV.  */
  48 enum iv_extend_code
  49 {
  50   IV_SIGN_EXTEND,
  51   IV_ZERO_EXTEND,
  52   IV_UNKNOWN_EXTEND
  53 };
  54
  55 /* The structure describing a bound on number of iterations of a loop.  */
  56
  57 struct GTY ((chain_next ("%h.next"))) nb_iter_bound {
  58   /* The statement STMT is executed at most ...  */
  59   gimple stmt;
  60
  61   /* ... BOUND + 1 times (BOUND must be an unsigned constant).
  62      The + 1 is added for the following reasons:
  63
  64      a) 0 would otherwise be unused, while we would need to care more about
  65         overflows (as MAX + 1 is sometimes produced as the estimate on number
  66         of executions of STMT).
  67      b) it is consistent with the result of number_of_iterations_exit.  */
  68   double_int bound;
  69
  70   /* True if the statement will cause the loop to be leaved the (at most)
  71      BOUND + 1-st time it is executed, that is, all the statements after it
  72      are executed at most BOUND times.  */
  73   bool is_exit;
  74
  75   /* The next bound in the list.  */
  76   struct nb_iter_bound *next;
  77 };
  78
  79 /* Description of the loop exit.  */
  80
  81 struct GTY (()) loop_exit {
  82   /* The exit edge.  */
  83   edge e;
  84
  85   /* Previous and next exit in the list of the exits of the loop.  */
  86   struct loop_exit *prev;
  87   struct loop_exit *next;
  88
  89   /* Next element in the list of loops from that E exits.  */
  90   struct loop_exit *next_e;
  91 };
  92
  93 typedef struct loop *loop_p;
  94 DEF_VEC_P (loop_p);
  95 DEF_VEC_ALLOC_P (loop_p, heap);
  96 DEF_VEC_ALLOC_P (loop_p, gc);
  97
  98 /* An integer estimation of the number of iterations.  Estimate_state
  99    describes what is the state of the estimation.  */
 100 enum loop_estimation
 101 {
 102   /* Estimate was not computed yet.  */
 103   EST_NOT_COMPUTED,
 104   /* Estimate is ready.  */
 105   EST_AVAILABLE
 106 };
 107
 108 /* Structure to hold information for each natural loop.  */
 109 struct GTY ((chain_next ("%h.next"))) loop {
 110   /* Index into loops array.  */
 111   int num;
 112
 113   /* Number of loop insns.  */
 114   unsigned ninsns;
 115
 116   /* Basic block of loop header.  */
 117   basic_block header;
 118
 119   /* Basic block of loop latch.  */
 120   basic_block latch;
 121
 122   /* For loop unrolling/peeling decision.  */
 123   struct lpt_decision lpt_decision;
 124
 125   /* Average number of executed insns per iteration.  */
 126   unsigned av_ninsns;
 127
 128   /* Number of blocks contained within the loop.  */
 129   unsigned num_nodes;
 130
 131   /* Superloops of the loop, starting with the outermost loop.  */
 132   VEC (loop_p, gc) *superloops;
 133
 134   /* The first inner (child) loop or NULL if innermost loop.  */
 135   struct loop *inner;
 136
 137   /* Link to the next (sibling) loop.  */
 138   struct loop *next;
 139
 140   /* Auxiliary info specific to a pass.  */
 141   PTR GTY ((skip (""))) aux;
 142
 143   /* The number of times the latch of the loop is executed.  This can be an
 144      INTEGER_CST, or a symbolic expression representing the number of
 145      iterations like "N - 1", or a COND_EXPR containing the runtime
 146      conditions under which the number of iterations is non zero.
 147
 148      Don't access this field directly: number_of_latch_executions
 149      computes and caches the computed information in this field.  */
 150   tree nb_iterations;
 151
 152   /* An integer guaranteed to be greater or equal to nb_iterations.  Only
 153      valid if any_upper_bound is true.  */
 154   double_int nb_iterations_upper_bound;
 155
 156   /* An integer giving an estimate on nb_iterations.  Unlike
 157      nb_iterations_upper_bound, there is no guarantee that it is at least
 158      nb_iterations.  */
 159   double_int nb_iterations_estimate;
 160
 161   bool any_upper_bound;
 162   bool any_estimate;
 163
 164   /* True if the loop can be parallel.  */
 165   bool can_be_parallel;
 166
 167   /* An integer estimation of the number of iterations.  Estimate_state
 168      describes what is the state of the estimation.  */
 169   enum loop_estimation estimate_state;
 170
 171   /* Upper bound on number of iterations of a loop.  */
 172   struct nb_iter_bound *bounds;
 173
 174   /* Head of the cyclic list of the exits of the loop.  */
 175   struct loop_exit *exits;
 176 };
 177
 178 /* Flags for state of loop structure.  */
 179 enum
 180 {
 181   LOOPS_HAVE_PREHEADERS = 1,
 182   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 183   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
 184   LOOPS_HAVE_RECORDED_EXITS = 8,
 185   LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16,
 186   LOOP_CLOSED_SSA = 32,
 187   LOOPS_NEED_FIXUP = 64,
 188   LOOPS_HAVE_FALLTHRU_PREHEADERS = 128
 189 };
 190
 191 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 192                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 193 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
 194
 195 /* Structure to hold CFG information about natural loops within a function.  */
 196 struct GTY (()) loops {
 197   /* State of loops.  */
 198   int state;
 199
 200   /* Array of the loops.  */
 201   VEC (loop_p, gc) *larray;
 202
 203   /* Maps edges to the list of their descriptions as loop exits.  Edges
 204      whose sources or destinations have loop_father == NULL (which may
 205      happen during the cfg manipulations) should not appear in EXITS.  */
 206   htab_t GTY((param_is (struct loop_exit))) exits;
 207
 208   /* Pointer to root of loop hierarchy tree.  */
 209   struct loop *tree_root;
 210 };
 211
 212 /* Loop recognition.  */
 213 extern int flow_loops_find (struct loops *);
 214 extern void disambiguate_loops_with_multiple_latches (void);
 215 extern void flow_loops_free (struct loops *);
 216 extern void flow_loops_dump (FILE *,
 217                              void (*)(const struct loop *, FILE *, int), int);
 218 extern void flow_loop_dump (const struct loop *, FILE *,
 219                             void (*)(const struct loop *, FILE *, int), int);
 220 struct loop *alloc_loop (void);
 221 extern void flow_loop_free (struct loop *);
 222 int flow_loop_nodes_find (basic_block, struct loop *);
 223 void fix_loop_structure (bitmap changed_bbs);
 224 bool mark_irreducible_loops (void);
 225 void release_recorded_exits (void);
 226 void record_loop_exits (void);
 227 void rescan_loop_exit (edge, bool, bool);
 228
 229 /* Loop data structure manipulation/querying.  */
 230 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 231 extern void flow_loop_tree_node_remove (struct loop *);
 232 extern void add_loop (struct loop *, struct loop *);
 233 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 234 extern bool flow_bb_inside_loop_p (const struct loop *, const_basic_block);
 235 extern struct loop * find_common_loop (struct loop *, struct loop *);
 236 struct loop *superloop_at_depth (struct loop *, unsigned);
 237 struct eni_weights_d;
 238 extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *);
 239 extern int num_loop_insns (const struct loop *);
 240 extern int average_num_loop_insns (const struct loop *);
 241 extern unsigned get_loop_level (const struct loop *);
 242 extern bool loop_exit_edge_p (const struct loop *, const_edge);
 243 extern bool loop_exits_to_bb_p (struct loop *, basic_block);
 244 extern bool loop_exits_from_bb_p (struct loop *, basic_block);
 245 extern void mark_loop_exit_edges (void);
 246
 247 /* Loops & cfg manipulation.  */
 248 extern basic_block *get_loop_body (const struct loop *);
 249 extern unsigned get_loop_body_with_size (const struct loop *, basic_block *,
 250                                          unsigned);
 251 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 252 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 253 extern basic_block *get_loop_body_in_custom_order (const struct loop *,
 254                                int (*) (const void *, const void *));
 255
 256 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
 257 edge single_exit (const struct loop *);
 258 extern unsigned num_loop_branches (const struct loop *);
 259
 260 extern edge loop_preheader_edge (const struct loop *);
 261 extern edge loop_latch_edge (const struct loop *);
 262
 263 extern void add_bb_to_loop (basic_block, struct loop *);
 264 extern void remove_bb_from_loops (basic_block);
 265
 266 extern void cancel_loop_tree (struct loop *);
 267 extern void delete_loop (struct loop *);
 268
 269 enum
 270 {
 271   CP_SIMPLE_PREHEADERS = 1,
 272   CP_FALLTHRU_PREHEADERS = 2
 273 };
 274
 275 basic_block create_preheader (struct loop *, int);
 276 extern void create_preheaders (int);
 277 extern void force_single_succ_latches (void);
 278
 279 extern void verify_loop_structure (void);
 280
 281 /* Loop analysis.  */
 282 extern bool just_once_each_iteration_p (const struct loop *, const_basic_block);
 283 gcov_type expected_loop_iterations_unbounded (const struct loop *);
 284 extern unsigned expected_loop_iterations (const struct loop *);
 285 extern rtx doloop_condition_get (rtx);
 286
 287 void estimate_numbers_of_iterations_loop (struct loop *);
 288 void record_niter_bound (struct loop *, double_int, bool, bool);
 289 bool estimated_loop_iterations (struct loop *, double_int *);
 290 bool max_loop_iterations (struct loop *, double_int *);
 291 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *);
 292 HOST_WIDE_INT max_loop_iterations_int (struct loop *);
 293 bool max_stmt_executions (struct loop *, double_int *);
 294 bool estimated_stmt_executions (struct loop *, double_int *);
 295 HOST_WIDE_INT max_stmt_executions_int (struct loop *);
 296 HOST_WIDE_INT estimated_stmt_executions_int (struct loop *);
 297
 298 /* Loop manipulation.  */
 299 extern bool can_duplicate_loop_p (const struct loop *loop);
 300
 301 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 302                                            duplicate_loop_to_header_edge.  */
 303 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 304                                            field of newly create BB.  */
 305 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 306                                            a complete peeling.  */
 307
 308 extern edge create_empty_if_region_on_edge (edge, tree);
 309 extern struct loop *create_empty_loop_on_edge (edge, tree, tree, tree, tree,
 310                                                tree *, tree *, struct loop *);
 311 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 312 extern void duplicate_subloops (struct loop *, struct loop *);
 313 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 314                                            unsigned, sbitmap, edge,
 315                                            VEC (edge, heap) **, int);
 316 extern struct loop *loopify (edge, edge,
 317                              basic_block, edge, edge, bool,
 318                              unsigned, unsigned);
 319 struct loop * loop_version (struct loop *, void *,
 320                             basic_block *, unsigned, unsigned, unsigned, bool);
 321 extern bool remove_path (edge);
 322 void scale_loop_frequencies (struct loop *, int, int);
 323
 324 /* Induction variable analysis.  */
 325
 326 /* The description of induction variable.  The things are a bit complicated
 327    due to need to handle subregs and extends.  The value of the object described
 328    by it can be obtained as follows (all computations are done in extend_mode):
 329
 330    Value in i-th iteration is
 331      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 332
 333    If first_special is true, the value in the first iteration is
 334      delta + mult * base
 335
 336    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 337      subreg_{mode} (base + i * step)
 338
 339    The get_iv_value function can be used to obtain these expressions.
 340
 341    ??? Add a third mode field that would specify the mode in that inner
 342    computation is done, which would enable it to be different from the
 343    outer one?  */
 344
 345 struct rtx_iv
 346 {
 347   /* Its base and step (mode of base and step is supposed to be extend_mode,
 348      see the description above).  */
 349   rtx base, step;
 350
 351   /* The type of extend applied to it (IV_SIGN_EXTEND, IV_ZERO_EXTEND,
 352      or IV_UNKNOWN_EXTEND).  */
 353   enum iv_extend_code extend;
 354
 355   /* Operations applied in the extended mode.  */
 356   rtx delta, mult;
 357
 358   /* The mode it is extended to.  */
 359   enum machine_mode extend_mode;
 360
 361   /* The mode the variable iterates in.  */
 362   enum machine_mode mode;
 363
 364   /* Whether the first iteration needs to be handled specially.  */
 365   unsigned first_special : 1;
 366 };
 367
 368 /* The description of an exit from the loop and of the number of iterations
 369    till we take the exit.  */
 370
 371 struct niter_desc
 372 {
 373   /* The edge out of the loop.  */
 374   edge out_edge;
 375
 376   /* The other edge leading from the condition.  */
 377   edge in_edge;
 378
 379   /* True if we are able to say anything about number of iterations of the
 380      loop.  */
 381   bool simple_p;
 382
 383   /* True if the loop iterates the constant number of times.  */
 384   bool const_iter;
 385
 386   /* Number of iterations if constant.  */
 387   unsigned HOST_WIDEST_INT niter;
 388
 389   /* Upper bound on the number of iterations.  */
 390   unsigned HOST_WIDEST_INT niter_max;
 391
 392   /* Assumptions under that the rest of the information is valid.  */
 393   rtx assumptions;
 394
 395   /* Assumptions under that the loop ends before reaching the latch,
 396      even if value of niter_expr says otherwise.  */
 397   rtx noloop_assumptions;
 398
 399   /* Condition under that the loop is infinite.  */
 400   rtx infinite;
 401
 402   /* Whether the comparison is signed.  */
 403   bool signed_p;
 404
 405   /* The mode in that niter_expr should be computed.  */
 406   enum machine_mode mode;
 407
 408   /* The number of iterations of the loop.  */
 409   rtx niter_expr;
 410 };
 411
 412 extern void iv_analysis_loop_init (struct loop *);
 413 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 414 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 415 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 416 extern rtx get_iv_value (struct rtx_iv *, rtx);
 417 extern bool biv_p (rtx, rtx);
 418 extern void find_simple_exit (struct loop *, struct niter_desc *);
 419 extern void iv_analysis_done (void);
 420
 421 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 422 extern void free_simple_loop_desc (struct loop *loop);
 423
 424 static inline struct niter_desc *
 425 simple_loop_desc (struct loop *loop)
 426 {
 427   return (struct niter_desc *) loop->aux;
 428 }
 429
 430 /* Accessors for the loop structures.  */
 431
 432 /* Returns the loop with index NUM from current_loops.  */
 433
 434 static inline struct loop *
 435 get_loop (unsigned num)
 436 {
 437   return VEC_index (loop_p, current_loops->larray, num);
 438 }
 439
 440 /* Returns the number of superloops of LOOP.  */
 441
 442 static inline unsigned
 443 loop_depth (const struct loop *loop)
 444 {
 445   return VEC_length (loop_p, loop->superloops);
 446 }
 447
 448 /* Returns the loop depth of the loop BB belongs to.  */
 449
 450 static inline int
 451 bb_loop_depth (const_basic_block bb)
 452 {
 453   return bb->loop_father ? loop_depth (bb->loop_father) : 0;
 454 }
 455
 456 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
 457    loop.  */
 458
 459 static inline struct loop *
 460 loop_outer (const struct loop *loop)
 461 {
 462   unsigned n = VEC_length (loop_p, loop->superloops);
 463
 464   if (n == 0)
 465     return NULL;
 466
 467   return VEC_index (loop_p, loop->superloops, n - 1);
 468 }
 469
 470 /* Returns true if LOOP has at least one exit edge.  */
 471
 472 static inline bool
 473 loop_has_exit_edges (const struct loop *loop)
 474 {
 475   return loop->exits->next->e != NULL;
 476 }
 477
 478 /* Returns the list of loops in current_loops.  */
 479
 480 static inline VEC (loop_p, gc) *
 481 get_loops (void)
 482 {
 483   if (!current_loops)
 484     return NULL;
 485
 486   return current_loops->larray;
 487 }
 488
 489 /* Returns the number of loops in current_loops (including the removed
 490    ones and the fake loop that forms the root of the loop tree).  */
 491
 492 static inline unsigned
 493 number_of_loops (void)
 494 {
 495   if (!current_loops)
 496     return 0;
 497
 498   return VEC_length (loop_p, current_loops->larray);
 499 }
 500
 501 /* Returns true if state of the loops satisfies all properties
 502    described by FLAGS.  */
 503
 504 static inline bool
 505 loops_state_satisfies_p (unsigned flags)
 506 {
 507   return (current_loops->state & flags) == flags;
 508 }
 509
 510 /* Sets FLAGS to the loops state.  */
 511
 512 static inline void
 513 loops_state_set (unsigned flags)
 514 {
 515   current_loops->state |= flags;
 516 }
 517
 518 /* Clears FLAGS from the loops state.  */
 519
 520 static inline void
 521 loops_state_clear (unsigned flags)
 522 {
 523   if (!current_loops)
 524     return;
 525   current_loops->state &= ~flags;
 526 }
 527
 528 /* Loop iterators.  */
 529
 530 /* Flags for loop iteration.  */
 531
 532 enum li_flags
 533 {
 534   LI_INCLUDE_ROOT = 1,          /* Include the fake root of the loop tree.  */
 535   LI_FROM_INNERMOST = 2,        /* Iterate over the loops in the reverse order,
 536                                    starting from innermost ones.  */
 537   LI_ONLY_INNERMOST = 4         /* Iterate only over innermost loops.  */
 538 };
 539
 540 /* The iterator for loops.  */
 541
 542 typedef struct
 543 {
 544   /* The list of loops to visit.  */
 545   VEC(int,heap) *to_visit;
 546
 547   /* The index of the actual loop.  */
 548   unsigned idx;
 549 } loop_iterator;
 550
 551 static inline void
 552 fel_next (loop_iterator *li, loop_p *loop)
 553 {
 554   int anum;
 555
 556   while (VEC_iterate (int, li->to_visit, li->idx, anum))
 557     {
 558       li->idx++;
 559       *loop = get_loop (anum);
 560       if (*loop)
 561         return;
 562     }
 563
 564   VEC_free (int, heap, li->to_visit);
 565   *loop = NULL;
 566 }
 567
 568 static inline void
 569 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
 570 {
 571   struct loop *aloop;
 572   unsigned i;
 573   int mn;
 574
 575   li->idx = 0;
 576   if (!current_loops)
 577     {
 578       li->to_visit = NULL;
 579       *loop = NULL;
 580       return;
 581     }
 582
 583   li->to_visit = VEC_alloc (int, heap, number_of_loops ());
 584   mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
 585
 586   if (flags & LI_ONLY_INNERMOST)
 587     {
 588       for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
 589         if (aloop != NULL
 590             && aloop->inner == NULL
 591             && aloop->num >= mn)
 592           VEC_quick_push (int, li->to_visit, aloop->num);
 593     }
 594   else if (flags & LI_FROM_INNERMOST)
 595     {
 596       /* Push the loops to LI->TO_VISIT in postorder.  */
 597       for (aloop = current_loops->tree_root;
 598            aloop->inner != NULL;
 599            aloop = aloop->inner)
 600         continue;
 601
 602       while (1)
 603         {
 604           if (aloop->num >= mn)
 605             VEC_quick_push (int, li->to_visit, aloop->num);
 606
 607           if (aloop->next)
 608             {
 609               for (aloop = aloop->next;
 610                    aloop->inner != NULL;
 611                    aloop = aloop->inner)
 612                 continue;
 613             }
 614           else if (!loop_outer (aloop))
 615             break;
 616           else
 617             aloop = loop_outer (aloop);
 618         }
 619     }
 620   else
 621     {
 622       /* Push the loops to LI->TO_VISIT in preorder.  */
 623       aloop = current_loops->tree_root;
 624       while (1)
 625         {
 626           if (aloop->num >= mn)
 627             VEC_quick_push (int, li->to_visit, aloop->num);
 628
 629           if (aloop->inner != NULL)
 630             aloop = aloop->inner;
 631           else
 632             {
 633               while (aloop != NULL && aloop->next == NULL)
 634                 aloop = loop_outer (aloop);
 635               if (aloop == NULL)
 636                 break;
 637               aloop = aloop->next;
 638             }
 639         }
 640     }
 641
 642   fel_next (li, loop);
 643 }
 644
 645 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
 646   for (fel_init (&(LI), &(LOOP), FLAGS); \
 647        (LOOP); \
 648        fel_next (&(LI), &(LOOP)))
 649
 650 #define FOR_EACH_LOOP_BREAK(LI) \
 651   { \
 652     VEC_free (int, heap, (LI).to_visit); \
 653     break; \
 654   }
 655
 656 /* The properties of the target.  */
 657 struct target_cfgloop {
 658   /* Number of available registers.  */
 659   unsigned x_target_avail_regs;
 660
 661   /* Number of available registers that are call-clobbered.  */
 662   unsigned x_target_clobbered_regs;
 663
 664   /* Number of registers reserved for temporary expressions.  */
 665   unsigned x_target_res_regs;
 666
 667   /* The cost for register when there still is some reserve, but we are
 668      approaching the number of available registers.  */
 669   unsigned x_target_reg_cost[2];
 670
 671   /* The cost for register when we need to spill.  */
 672   unsigned x_target_spill_cost[2];
 673 };
 674
 675 extern struct target_cfgloop default_target_cfgloop;
 676 #if SWITCHABLE_TARGET
 677 extern struct target_cfgloop *this_target_cfgloop;
 678 #else
 679 #define this_target_cfgloop (&default_target_cfgloop)
 680 #endif
 681
 682 #define target_avail_regs \
 683   (this_target_cfgloop->x_target_avail_regs)
 684 #define target_clobbered_regs \
 685   (this_target_cfgloop->x_target_clobbered_regs)
 686 #define target_res_regs \
 687   (this_target_cfgloop->x_target_res_regs)
 688 #define target_reg_cost \
 689   (this_target_cfgloop->x_target_reg_cost)
 690 #define target_spill_cost \
 691   (this_target_cfgloop->x_target_spill_cost)
 692
 693 /* Register pressure estimation for induction variable optimizations & loop
 694    invariant motion.  */
 695 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool, bool);
 696 extern void init_set_costs (void);
 697
 698 /* Loop optimizer initialization.  */
 699 extern void loop_optimizer_init (unsigned);
 700 extern void loop_optimizer_finalize (void);
 701
 702 /* Optimization passes.  */
 703 extern void unswitch_loops (void);
 704
 705 enum
 706 {
 707   UAP_PEEL = 1,         /* Enables loop peeling.  */
 708   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 709   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 710 };
 711
 712 extern void unroll_and_peel_loops (int);
 713 extern void doloop_optimize_loops (void);
 714 extern void move_loop_invariants (void);
 715 extern bool finite_loop_p (struct loop *);
 716
 717 #endif /* GCC_CFGLOOP_H */