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 extern edge single_exit (const struct loop *);
 258 extern edge single_likely_exit (struct loop *loop);
 259 extern unsigned num_loop_branches (const struct loop *);
 260
 261 extern edge loop_preheader_edge (const struct loop *);
 262 extern edge loop_latch_edge (const struct loop *);
 263
 264 extern void add_bb_to_loop (basic_block, struct loop *);
 265 extern void remove_bb_from_loops (basic_block);
 266
 267 extern void cancel_loop_tree (struct loop *);
 268 extern void delete_loop (struct loop *);
 269
 270 enum
 271 {
 272   CP_SIMPLE_PREHEADERS = 1,
 273   CP_FALLTHRU_PREHEADERS = 2
 274 };
 275
 276 basic_block create_preheader (struct loop *, int);
 277 extern void create_preheaders (int);
 278 extern void force_single_succ_latches (void);
 279
 280 extern void verify_loop_structure (void);
 281
 282 /* Loop analysis.  */
 283 extern bool just_once_each_iteration_p (const struct loop *, const_basic_block);
 284 gcov_type expected_loop_iterations_unbounded (const struct loop *);
 285 extern unsigned expected_loop_iterations (const struct loop *);
 286 extern rtx doloop_condition_get (rtx);
 287
 288 void estimate_numbers_of_iterations_loop (struct loop *);
 289 void record_niter_bound (struct loop *, double_int, bool, bool);
 290 bool estimated_loop_iterations (struct loop *, double_int *);
 291 bool max_loop_iterations (struct loop *, double_int *);
 292 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *);
 293 HOST_WIDE_INT max_loop_iterations_int (struct loop *);
 294 bool max_stmt_executions (struct loop *, double_int *);
 295 bool estimated_stmt_executions (struct loop *, double_int *);
 296 HOST_WIDE_INT max_stmt_executions_int (struct loop *);
 297 HOST_WIDE_INT estimated_stmt_executions_int (struct loop *);
 298
 299 /* Loop manipulation.  */
 300 extern bool can_duplicate_loop_p (const struct loop *loop);
 301
 302 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 303                                            duplicate_loop_to_header_edge.  */
 304 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 305                                            field of newly create BB.  */
 306 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 307                                            a complete peeling.  */
 308
 309 extern edge create_empty_if_region_on_edge (edge, tree);
 310 extern struct loop *create_empty_loop_on_edge (edge, tree, tree, tree, tree,
 311                                                tree *, tree *, struct loop *);
 312 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 313 extern void duplicate_subloops (struct loop *, struct loop *);
 314 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 315                                            unsigned, sbitmap, edge,
 316                                            VEC (edge, heap) **, int);
 317 extern struct loop *loopify (edge, edge,
 318                              basic_block, edge, edge, bool,
 319                              unsigned, unsigned);
 320 struct loop * loop_version (struct loop *, void *,
 321                             basic_block *, unsigned, unsigned, unsigned, bool);
 322 extern bool remove_path (edge);
 323 extern void unloop (struct loop *, bool *);
 324 extern void scale_loop_frequencies (struct loop *, int, int);
 325
 326 /* Induction variable analysis.  */
 327
 328 /* The description of induction variable.  The things are a bit complicated
 329    due to need to handle subregs and extends.  The value of the object described
 330    by it can be obtained as follows (all computations are done in extend_mode):
 331
 332    Value in i-th iteration is
 333      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 334
 335    If first_special is true, the value in the first iteration is
 336      delta + mult * base
 337
 338    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 339      subreg_{mode} (base + i * step)
 340
 341    The get_iv_value function can be used to obtain these expressions.
 342
 343    ??? Add a third mode field that would specify the mode in that inner
 344    computation is done, which would enable it to be different from the
 345    outer one?  */
 346
 347 struct rtx_iv
 348 {
 349   /* Its base and step (mode of base and step is supposed to be extend_mode,
 350      see the description above).  */
 351   rtx base, step;
 352
 353   /* The type of extend applied to it (IV_SIGN_EXTEND, IV_ZERO_EXTEND,
 354      or IV_UNKNOWN_EXTEND).  */
 355   enum iv_extend_code extend;
 356
 357   /* Operations applied in the extended mode.  */
 358   rtx delta, mult;
 359
 360   /* The mode it is extended to.  */
 361   enum machine_mode extend_mode;
 362
 363   /* The mode the variable iterates in.  */
 364   enum machine_mode mode;
 365
 366   /* Whether the first iteration needs to be handled specially.  */
 367   unsigned first_special : 1;
 368 };
 369
 370 /* The description of an exit from the loop and of the number of iterations
 371    till we take the exit.  */
 372
 373 struct niter_desc
 374 {
 375   /* The edge out of the loop.  */
 376   edge out_edge;
 377
 378   /* The other edge leading from the condition.  */
 379   edge in_edge;
 380
 381   /* True if we are able to say anything about number of iterations of the
 382      loop.  */
 383   bool simple_p;
 384
 385   /* True if the loop iterates the constant number of times.  */
 386   bool const_iter;
 387
 388   /* Number of iterations if constant.  */
 389   unsigned HOST_WIDEST_INT niter;
 390
 391   /* Assumptions under that the rest of the information is valid.  */
 392   rtx assumptions;
 393
 394   /* Assumptions under that the loop ends before reaching the latch,
 395      even if value of niter_expr says otherwise.  */
 396   rtx noloop_assumptions;
 397
 398   /* Condition under that the loop is infinite.  */
 399   rtx infinite;
 400
 401   /* Whether the comparison is signed.  */
 402   bool signed_p;
 403
 404   /* The mode in that niter_expr should be computed.  */
 405   enum machine_mode mode;
 406
 407   /* The number of iterations of the loop.  */
 408   rtx niter_expr;
 409 };
 410
 411 extern void iv_analysis_loop_init (struct loop *);
 412 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 413 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 414 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 415 extern rtx get_iv_value (struct rtx_iv *, rtx);
 416 extern bool biv_p (rtx, rtx);
 417 extern void find_simple_exit (struct loop *, struct niter_desc *);
 418 extern void iv_analysis_done (void);
 419
 420 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 421 extern void free_simple_loop_desc (struct loop *loop);
 422
 423 static inline struct niter_desc *
 424 simple_loop_desc (struct loop *loop)
 425 {
 426   return (struct niter_desc *) loop->aux;
 427 }
 428
 429 /* Accessors for the loop structures.  */
 430
 431 /* Returns the loop with index NUM from current_loops.  */
 432
 433 static inline struct loop *
 434 get_loop (unsigned num)
 435 {
 436   return VEC_index (loop_p, current_loops->larray, num);
 437 }
 438
 439 /* Returns the number of superloops of LOOP.  */
 440
 441 static inline unsigned
 442 loop_depth (const struct loop *loop)
 443 {
 444   return VEC_length (loop_p, loop->superloops);
 445 }
 446
 447 /* Returns the loop depth of the loop BB belongs to.  */
 448
 449 static inline int
 450 bb_loop_depth (const_basic_block bb)
 451 {
 452   return bb->loop_father ? loop_depth (bb->loop_father) : 0;
 453 }
 454
 455 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
 456    loop.  */
 457
 458 static inline struct loop *
 459 loop_outer (const struct loop *loop)
 460 {
 461   unsigned n = VEC_length (loop_p, loop->superloops);
 462
 463   if (n == 0)
 464     return NULL;
 465
 466   return VEC_index (loop_p, loop->superloops, n - 1);
 467 }
 468
 469 /* Returns true if LOOP has at least one exit edge.  */
 470
 471 static inline bool
 472 loop_has_exit_edges (const struct loop *loop)
 473 {
 474   return loop->exits->next->e != NULL;
 475 }
 476
 477 /* Returns the list of loops in current_loops.  */
 478
 479 static inline VEC (loop_p, gc) *
 480 get_loops (void)
 481 {
 482   if (!current_loops)
 483     return NULL;
 484
 485   return current_loops->larray;
 486 }
 487
 488 /* Returns the number of loops in current_loops (including the removed
 489    ones and the fake loop that forms the root of the loop tree).  */
 490
 491 static inline unsigned
 492 number_of_loops (void)
 493 {
 494   if (!current_loops)
 495     return 0;
 496
 497   return VEC_length (loop_p, current_loops->larray);
 498 }
 499
 500 /* Returns true if state of the loops satisfies all properties
 501    described by FLAGS.  */
 502
 503 static inline bool
 504 loops_state_satisfies_p (unsigned flags)
 505 {
 506   return (current_loops->state & flags) == flags;
 507 }
 508
 509 /* Sets FLAGS to the loops state.  */
 510
 511 static inline void
 512 loops_state_set (unsigned flags)
 513 {
 514   current_loops->state |= flags;
 515 }
 516
 517 /* Clears FLAGS from the loops state.  */
 518
 519 static inline void
 520 loops_state_clear (unsigned flags)
 521 {
 522   if (!current_loops)
 523     return;
 524   current_loops->state &= ~flags;
 525 }
 526
 527 /* Loop iterators.  */
 528
 529 /* Flags for loop iteration.  */
 530
 531 enum li_flags
 532 {
 533   LI_INCLUDE_ROOT = 1,          /* Include the fake root of the loop tree.  */
 534   LI_FROM_INNERMOST = 2,        /* Iterate over the loops in the reverse order,
 535                                    starting from innermost ones.  */
 536   LI_ONLY_INNERMOST = 4         /* Iterate only over innermost loops.  */
 537 };
 538
 539 /* The iterator for loops.  */
 540
 541 typedef struct
 542 {
 543   /* The list of loops to visit.  */
 544   VEC(int,heap) *to_visit;
 545
 546   /* The index of the actual loop.  */
 547   unsigned idx;
 548 } loop_iterator;
 549
 550 static inline void
 551 fel_next (loop_iterator *li, loop_p *loop)
 552 {
 553   int anum;
 554
 555   while (VEC_iterate (int, li->to_visit, li->idx, anum))
 556     {
 557       li->idx++;
 558       *loop = get_loop (anum);
 559       if (*loop)
 560         return;
 561     }
 562
 563   VEC_free (int, heap, li->to_visit);
 564   *loop = NULL;
 565 }
 566
 567 static inline void
 568 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
 569 {
 570   struct loop *aloop;
 571   unsigned i;
 572   int mn;
 573
 574   li->idx = 0;
 575   if (!current_loops)
 576     {
 577       li->to_visit = NULL;
 578       *loop = NULL;
 579       return;
 580     }
 581
 582   li->to_visit = VEC_alloc (int, heap, number_of_loops ());
 583   mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
 584
 585   if (flags & LI_ONLY_INNERMOST)
 586     {
 587       for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
 588         if (aloop != NULL
 589             && aloop->inner == NULL
 590             && aloop->num >= mn)
 591           VEC_quick_push (int, li->to_visit, aloop->num);
 592     }
 593   else if (flags & LI_FROM_INNERMOST)
 594     {
 595       /* Push the loops to LI->TO_VISIT in postorder.  */
 596       for (aloop = current_loops->tree_root;
 597            aloop->inner != NULL;
 598            aloop = aloop->inner)
 599         continue;
 600
 601       while (1)
 602         {
 603           if (aloop->num >= mn)
 604             VEC_quick_push (int, li->to_visit, aloop->num);
 605
 606           if (aloop->next)
 607             {
 608               for (aloop = aloop->next;
 609                    aloop->inner != NULL;
 610                    aloop = aloop->inner)
 611                 continue;
 612             }
 613           else if (!loop_outer (aloop))
 614             break;
 615           else
 616             aloop = loop_outer (aloop);
 617         }
 618     }
 619   else
 620     {
 621       /* Push the loops to LI->TO_VISIT in preorder.  */
 622       aloop = current_loops->tree_root;
 623       while (1)
 624         {
 625           if (aloop->num >= mn)
 626             VEC_quick_push (int, li->to_visit, aloop->num);
 627
 628           if (aloop->inner != NULL)
 629             aloop = aloop->inner;
 630           else
 631             {
 632               while (aloop != NULL && aloop->next == NULL)
 633                 aloop = loop_outer (aloop);
 634               if (aloop == NULL)
 635                 break;
 636               aloop = aloop->next;
 637             }
 638         }
 639     }
 640
 641   fel_next (li, loop);
 642 }
 643
 644 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
 645   for (fel_init (&(LI), &(LOOP), FLAGS); \
 646        (LOOP); \
 647        fel_next (&(LI), &(LOOP)))
 648
 649 #define FOR_EACH_LOOP_BREAK(LI) \
 650   { \
 651     VEC_free (int, heap, (LI).to_visit); \
 652     break; \
 653   }
 654
 655 /* The properties of the target.  */
 656 struct target_cfgloop {
 657   /* Number of available registers.  */
 658   unsigned x_target_avail_regs;
 659
 660   /* Number of available registers that are call-clobbered.  */
 661   unsigned x_target_clobbered_regs;
 662
 663   /* Number of registers reserved for temporary expressions.  */
 664   unsigned x_target_res_regs;
 665
 666   /* The cost for register when there still is some reserve, but we are
 667      approaching the number of available registers.  */
 668   unsigned x_target_reg_cost[2];
 669
 670   /* The cost for register when we need to spill.  */
 671   unsigned x_target_spill_cost[2];
 672 };
 673
 674 extern struct target_cfgloop default_target_cfgloop;
 675 #if SWITCHABLE_TARGET
 676 extern struct target_cfgloop *this_target_cfgloop;
 677 #else
 678 #define this_target_cfgloop (&default_target_cfgloop)
 679 #endif
 680
 681 #define target_avail_regs \
 682   (this_target_cfgloop->x_target_avail_regs)
 683 #define target_clobbered_regs \
 684   (this_target_cfgloop->x_target_clobbered_regs)
 685 #define target_res_regs \
 686   (this_target_cfgloop->x_target_res_regs)
 687 #define target_reg_cost \
 688   (this_target_cfgloop->x_target_reg_cost)
 689 #define target_spill_cost \
 690   (this_target_cfgloop->x_target_spill_cost)
 691
 692 /* Register pressure estimation for induction variable optimizations & loop
 693    invariant motion.  */
 694 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool, bool);
 695 extern void init_set_costs (void);
 696
 697 /* Loop optimizer initialization.  */
 698 extern void loop_optimizer_init (unsigned);
 699 extern void loop_optimizer_finalize (void);
 700
 701 /* Optimization passes.  */
 702 extern void unswitch_loops (void);
 703
 704 enum
 705 {
 706   UAP_PEEL = 1,         /* Enables loop peeling.  */
 707   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 708   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 709 };
 710
 711 extern void unroll_and_peel_loops (int);
 712 extern void doloop_optimize_loops (void);
 713 extern void move_loop_invariants (void);
 714 extern bool finite_loop_p (struct loop *);
 715 extern void scale_loop_profile (struct loop *loop, int scale, int iteration_bound);
 716
 717 /* Returns the outermost loop of the loop nest that contains LOOP.*/
 718 static inline struct loop *
 719 loop_outermost (struct loop *loop)
 720 {
 721
 722   unsigned n = VEC_length (loop_p, loop->superloops);
 723
 724   if (n <= 1)
 725     return loop;
 726
 727   return VEC_index (loop_p, loop->superloops, 1);
 728 }
 729
 730
 731 #endif /* GCC_CFGLOOP_H */