gcc/cfgloop.h

   1 /* Natural loop functions
   2    Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
   3    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 2, 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 COPYING.  If not, write to the Free
  19 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  20 02110-1301, USA.  */
  21
  22 #ifndef GCC_CFGLOOP_H
  23 #define GCC_CFGLOOP_H
  24
  25 #include "basic-block.h"
  26 /* For rtx_code.  */
  27 #include "rtl.h"
  28
  29 /* Structure to hold decision about unrolling/peeling.  */
  30 enum lpt_dec
  31 {
  32   LPT_NONE,
  33   LPT_PEEL_COMPLETELY,
  34   LPT_PEEL_SIMPLE,
  35   LPT_UNROLL_CONSTANT,
  36   LPT_UNROLL_RUNTIME,
  37   LPT_UNROLL_STUPID
  38 };
  39
  40 struct lpt_decision
  41 {
  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 nb_iter_bound
  49 {
  50   /* The statement STMT is executed at most ...  */
  51   tree stmt;
  52
  53   /* ... BOUND + 1 times (BOUND must be an unsigned constant).
  54      The + 1 is added for the following reasons:
  55
  56      a) 0 would otherwise be unused, while we would need to care more about
  57         overflows (as MAX + 1 is sometimes produced as the estimate on number
  58         of executions of STMT).
  59      b) it is consistent with the result of number_of_iterations_exit.  */
  60   double_int bound;
  61
  62   /* True if the statement will cause the loop to be leaved the (at most)
  63      BOUND + 1-st time it is executed, that is, all the statements after it
  64      are executed at most BOUND times.  */
  65   bool is_exit;
  66
  67   /* True if the bound is "realistic" -- i.e., most likely the loop really has
  68      number of iterations close to the bound.  Exact bounds (if the number of
  69      iterations of a loop is a constant) and bounds derived from the size of
  70      data accessed in the loop are considered realistic.  */
  71   bool realistic;
  72
  73   /* The next bound in the list.  */
  74   struct nb_iter_bound *next;
  75 };
  76
  77 /* Description of the loop exit.  */
  78
  79 struct loop_exit
  80 {
  81   /* The exit edge.  */
  82   edge e;
  83
  84   /* Previous and next exit in the list of the exits of the loop.  */
  85   struct loop_exit *prev;
  86   struct loop_exit *next;
  87
  88   /* Next element in the list of loops from that E exits.  */
  89   struct loop_exit *next_e;
  90 };
  91
  92 /* Structure to hold information for each natural loop.  */
  93 struct loop
  94 {
  95   /* Index into loops array.  */
  96   int num;
  97
  98   /* Basic block of loop header.  */
  99   basic_block header;
 100
 101   /* Basic block of loop latch.  */
 102   basic_block latch;
 103
 104   /* For loop unrolling/peeling decision.  */
 105   struct lpt_decision lpt_decision;
 106
 107   /* Number of loop insns.  */
 108   unsigned ninsns;
 109
 110   /* Average number of executed insns per iteration.  */
 111   unsigned av_ninsns;
 112
 113   /* Number of blocks contained within the loop.  */
 114   unsigned num_nodes;
 115
 116   /* The loop nesting depth.  */
 117   int depth;
 118
 119   /* Superloops of the loop.  */
 120   struct loop **pred;
 121
 122   /* The outer (parent) loop or NULL if outermost loop.  */
 123   struct loop *outer;
 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   /* Loop that is copy of this loop.  */
 132   struct loop *copy;
 133
 134   /* Auxiliary info specific to a pass.  */
 135   void *aux;
 136
 137   /* The number of times the latch of the loop is executed.
 138      This is an INTEGER_CST or an expression containing symbolic
 139      names.  Don't access this field directly:
 140      number_of_latch_executions computes and caches the computed
 141      information in this field.  */
 142   tree nb_iterations;
 143
 144   /* An integer estimation of the number of iterations.  Estimate_state
 145      describes what is the state of the estimation.  */
 146   enum
 147     {
 148       /* Estimate was not computed yet.  */
 149       EST_NOT_COMPUTED,
 150       /* Estimate was computed, but we could derive no useful bound.  */
 151       EST_NOT_AVAILABLE,
 152       /* Estimate is ready.  */
 153       EST_AVAILABLE
 154     } estimate_state;
 155   double_int estimated_nb_iterations;
 156
 157   /* Upper bound on number of iterations of a loop.  */
 158   struct nb_iter_bound *bounds;
 159
 160   /* Head of the cyclic list of the exits of the loop.  */
 161   struct loop_exit exits;
 162 };
 163
 164 /* Flags for state of loop structure.  */
 165 enum
 166 {
 167   LOOPS_HAVE_PREHEADERS = 1,
 168   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 169   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
 170   LOOPS_HAVE_RECORDED_EXITS = 8
 171 };
 172
 173 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 174                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 175
 176 typedef struct loop *loop_p;
 177 DEF_VEC_P (loop_p);
 178 DEF_VEC_ALLOC_P (loop_p, heap);
 179
 180 /* Structure to hold CFG information about natural loops within a function.  */
 181 struct loops
 182 {
 183   /* State of loops.  */
 184   int state;
 185
 186   /* Array of the loops.  */
 187   VEC (loop_p, heap) *larray;
 188
 189   /* Maps edges to the list of their descriptions as loop exits.  Edges
 190      whose sources or destinations have loop_father == NULL (which may
 191      happen during the cfg manipulations) should not appear in EXITS.  */
 192   htab_t exits;
 193
 194   /* Pointer to root of loop hierarchy tree.  */
 195   struct loop *tree_root;
 196 };
 197
 198 /* Loop recognition.  */
 199 extern int flow_loops_find (struct loops *);
 200 extern void flow_loops_free (struct loops *);
 201 extern void flow_loops_dump (FILE *,
 202                              void (*)(const struct loop *, FILE *, int), int);
 203 extern void flow_loop_dump (const struct loop *, FILE *,
 204                             void (*)(const struct loop *, FILE *, int), int);
 205 struct loop *alloc_loop (void);
 206 extern void flow_loop_free (struct loop *);
 207 int flow_loop_nodes_find (basic_block, struct loop *);
 208 void fix_loop_structure (bitmap changed_bbs);
 209 void mark_irreducible_loops (void);
 210 void release_recorded_exits (void);
 211 void record_loop_exits (void);
 212 void rescan_loop_exit (edge, bool, bool);
 213
 214 /* Loop data structure manipulation/querying.  */
 215 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 216 extern void flow_loop_tree_node_remove (struct loop *);
 217 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 218 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
 219 extern struct loop * find_common_loop (struct loop *, struct loop *);
 220 struct loop *superloop_at_depth (struct loop *, unsigned);
 221 struct eni_weights_d;
 222 extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *);
 223 extern int num_loop_insns (struct loop *);
 224 extern int average_num_loop_insns (struct loop *);
 225 extern unsigned get_loop_level (const struct loop *);
 226 extern bool loop_exit_edge_p (const struct loop *, edge);
 227 extern void mark_loop_exit_edges (void);
 228
 229 /* Loops & cfg manipulation.  */
 230 extern basic_block *get_loop_body (const struct loop *);
 231 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 232 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 233 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
 234 edge single_exit (const struct loop *);
 235 extern unsigned num_loop_branches (const struct loop *);
 236
 237 extern edge loop_preheader_edge (const struct loop *);
 238 extern edge loop_latch_edge (const struct loop *);
 239
 240 extern void add_bb_to_loop (basic_block, struct loop *);
 241 extern void remove_bb_from_loops (basic_block);
 242
 243 extern void cancel_loop_tree (struct loop *);
 244 extern void delete_loop (struct loop *);
 245
 246 enum
 247 {
 248   CP_SIMPLE_PREHEADERS = 1
 249 };
 250
 251 extern void create_preheaders (int);
 252 extern void force_single_succ_latches (void);
 253
 254 extern void verify_loop_structure (void);
 255
 256 /* Loop analysis.  */
 257 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
 258 extern unsigned expected_loop_iterations (const struct loop *);
 259 extern rtx doloop_condition_get (rtx);
 260
 261 /* Loop manipulation.  */
 262 extern bool can_duplicate_loop_p (struct loop *loop);
 263
 264 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 265                                            duplicate_loop_to_header_edge.  */
 266 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 267                                            field of newly create BB.  */
 268 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 269                                            a complete peeling.  */
 270
 271 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 272 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 273                                            unsigned, sbitmap, edge,
 274                                            VEC (edge, heap) **, int);
 275 extern struct loop *loopify (edge, edge,
 276                              basic_block, edge, edge, bool,
 277                              unsigned, unsigned);
 278 struct loop * loop_version (struct loop *, void *,
 279                             basic_block *, unsigned, unsigned, unsigned, bool);
 280 extern bool remove_path (edge);
 281 void scale_loop_frequencies (struct loop *, int, int);
 282
 283 /* Induction variable analysis.  */
 284
 285 /* The description of induction variable.  The things are a bit complicated
 286    due to need to handle subregs and extends.  The value of the object described
 287    by it can be obtained as follows (all computations are done in extend_mode):
 288
 289    Value in i-th iteration is
 290      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 291
 292    If first_special is true, the value in the first iteration is
 293      delta + mult * base
 294
 295    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 296      subreg_{mode} (base + i * step)
 297
 298    The get_iv_value function can be used to obtain these expressions.
 299
 300    ??? Add a third mode field that would specify the mode in that inner
 301    computation is done, which would enable it to be different from the
 302    outer one?  */
 303
 304 struct rtx_iv
 305 {
 306   /* Its base and step (mode of base and step is supposed to be extend_mode,
 307      see the description above).  */
 308   rtx base, step;
 309
 310   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 311   enum rtx_code extend;
 312
 313   /* Operations applied in the extended mode.  */
 314   rtx delta, mult;
 315
 316   /* The mode it is extended to.  */
 317   enum machine_mode extend_mode;
 318
 319   /* The mode the variable iterates in.  */
 320   enum machine_mode mode;
 321
 322   /* Whether the first iteration needs to be handled specially.  */
 323   unsigned first_special : 1;
 324 };
 325
 326 /* The description of an exit from the loop and of the number of iterations
 327    till we take the exit.  */
 328
 329 struct niter_desc
 330 {
 331   /* The edge out of the loop.  */
 332   edge out_edge;
 333
 334   /* The other edge leading from the condition.  */
 335   edge in_edge;
 336
 337   /* True if we are able to say anything about number of iterations of the
 338      loop.  */
 339   bool simple_p;
 340
 341   /* True if the loop iterates the constant number of times.  */
 342   bool const_iter;
 343
 344   /* Number of iterations if constant.  */
 345   unsigned HOST_WIDEST_INT niter;
 346
 347   /* Upper bound on the number of iterations.  */
 348   unsigned HOST_WIDEST_INT niter_max;
 349
 350   /* Assumptions under that the rest of the information is valid.  */
 351   rtx assumptions;
 352
 353   /* Assumptions under that the loop ends before reaching the latch,
 354      even if value of niter_expr says otherwise.  */
 355   rtx noloop_assumptions;
 356
 357   /* Condition under that the loop is infinite.  */
 358   rtx infinite;
 359
 360   /* Whether the comparison is signed.  */
 361   bool signed_p;
 362
 363   /* The mode in that niter_expr should be computed.  */
 364   enum machine_mode mode;
 365
 366   /* The number of iterations of the loop.  */
 367   rtx niter_expr;
 368 };
 369
 370 extern void iv_analysis_loop_init (struct loop *);
 371 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 372 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 373 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 374 extern rtx get_iv_value (struct rtx_iv *, rtx);
 375 extern bool biv_p (rtx, rtx);
 376 extern void find_simple_exit (struct loop *, struct niter_desc *);
 377 extern void iv_analysis_done (void);
 378 extern struct df *iv_current_loop_df (void);
 379
 380 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 381 extern void free_simple_loop_desc (struct loop *loop);
 382
 383 static inline struct niter_desc *
 384 simple_loop_desc (struct loop *loop)
 385 {
 386   return (struct niter_desc *) loop->aux;
 387 }
 388
 389 /* Accessors for the loop structures.  */
 390
 391 /* Returns the loop with index NUM from current_loops.  */
 392
 393 static inline struct loop *
 394 get_loop (unsigned num)
 395 {
 396   return VEC_index (loop_p, current_loops->larray, num);
 397 }
 398
 399 /* Returns the list of loops in current_loops.  */
 400
 401 static inline VEC (loop_p, heap) *
 402 get_loops (void)
 403 {
 404   if (!current_loops)
 405     return NULL;
 406
 407   return current_loops->larray;
 408 }
 409
 410 /* Returns the number of loops in current_loops (including the removed
 411    ones and the fake loop that forms the root of the loop tree).  */
 412
 413 static inline unsigned
 414 number_of_loops (void)
 415 {
 416   if (!current_loops)
 417     return 0;
 418
 419   return VEC_length (loop_p, current_loops->larray);
 420 }
 421
 422 /* Loop iterators.  */
 423
 424 /* Flags for loop iteration.  */
 425
 426 enum li_flags
 427 {
 428   LI_INCLUDE_ROOT = 1,  /* Include the fake root of the loop tree.  */
 429   LI_FROM_INNERMOST = 2,/* Iterate over the loops in the reverse order,
 430                            starting from innermost ones.  */
 431   LI_ONLY_INNERMOST = 4,/* Iterate only over innermost loops.  */
 432   LI_ONLY_OLD = 8       /* Do not traverse the loops created during the
 433                            traversal (this is the default behavior with
 434                            LI_FROM_INNERMOST).  */
 435 };
 436
 437 /* The iterator for loops.  */
 438
 439 typedef struct
 440 {
 441   int idx;              /* Index of the actual loop.  */
 442   int end;              /* Only loops before end should be traversed.  */
 443 } loop_iterator;
 444
 445 static inline void
 446 fel_next (loop_iterator *li, loop_p *loop, unsigned flags)
 447 {
 448   if (flags & LI_FROM_INNERMOST)
 449     {
 450       li->idx--;
 451       for (; li->idx > li->end; li->idx--)
 452         {
 453           *loop = VEC_index (loop_p, current_loops->larray, li->idx);
 454           if (*loop
 455               && (!(flags & LI_ONLY_INNERMOST)
 456                   || (*loop)->inner == NULL))
 457             return;
 458         }
 459     }
 460   else
 461     {
 462       if (!(flags & LI_ONLY_OLD))
 463         li->end = number_of_loops ();
 464       li->idx++;
 465       for (; li->idx < li->end; li->idx++)
 466         {
 467           *loop = VEC_index (loop_p, current_loops->larray, li->idx);
 468           if (*loop
 469               && (!(flags & LI_ONLY_INNERMOST)
 470                   || (*loop)->inner == NULL))
 471             return;
 472         }
 473     }
 474
 475   *loop = NULL;
 476 }
 477
 478 static inline void
 479 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
 480 {
 481   if (!current_loops)
 482     {
 483       li->idx = 0;
 484       li->end = 0;
 485       *loop = NULL;
 486       return;
 487     }
 488
 489   if (flags & LI_FROM_INNERMOST)
 490     {
 491       li->idx = number_of_loops ();
 492       li->end = (flags & LI_INCLUDE_ROOT) ? -1 : 0;
 493     }
 494   else
 495     {
 496       li->idx = (flags & LI_INCLUDE_ROOT) ? -1 : 0;
 497       li->end = number_of_loops ();
 498     }
 499   fel_next (li, loop, flags);
 500 }
 501
 502 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
 503   for (fel_init (&(LI), &(LOOP), FLAGS); \
 504        (LOOP); \
 505        fel_next (&(LI), &(LOOP), FLAGS))
 506
 507 /* The properties of the target.  */
 508
 509 extern unsigned target_avail_regs;      /* Number of available registers.  */
 510 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 511 extern unsigned target_small_cost;      /* The cost for register when there
 512                                            is a free one.  */
 513 extern unsigned target_pres_cost;       /* The cost for register when there are
 514                                            not too many free ones.  */
 515 extern unsigned target_spill_cost;      /* The cost for register when we need
 516                                            to spill.  */
 517
 518 /* Register pressure estimation for induction variable optimizations & loop
 519    invariant motion.  */
 520 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 521 extern void init_set_costs (void);
 522
 523 /* Loop optimizer initialization.  */
 524 extern void loop_optimizer_init (unsigned);
 525 extern void loop_optimizer_finalize (void);
 526
 527 /* Optimization passes.  */
 528 extern void unswitch_loops (void);
 529
 530 enum
 531 {
 532   UAP_PEEL = 1,         /* Enables loop peeling.  */
 533   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 534   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 535 };
 536
 537 extern void unroll_and_peel_loops (int);
 538 extern void doloop_optimize_loops (void);
 539 extern void move_loop_invariants (void);
 540
 541 #endif /* GCC_CFGLOOP_H */