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 extern unsigned tree_num_loop_insns (struct loop *);
 222 extern int num_loop_insns (struct loop *);
 223 extern int average_num_loop_insns (struct loop *);
 224 extern unsigned get_loop_level (const struct loop *);
 225 extern bool loop_exit_edge_p (const struct loop *, edge);
 226 extern void mark_loop_exit_edges (void);
 227
 228 /* Loops & cfg manipulation.  */
 229 extern basic_block *get_loop_body (const struct loop *);
 230 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 231 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 232 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
 233 edge single_exit (const struct loop *);
 234 extern unsigned num_loop_branches (const struct loop *);
 235
 236 extern edge loop_preheader_edge (const struct loop *);
 237 extern edge loop_latch_edge (const struct loop *);
 238
 239 extern void add_bb_to_loop (basic_block, struct loop *);
 240 extern void remove_bb_from_loops (basic_block);
 241
 242 extern void cancel_loop_tree (struct loop *);
 243 extern void delete_loop (struct loop *);
 244
 245 extern int fix_loop_placement (struct loop *);
 246
 247 enum
 248 {
 249   CP_SIMPLE_PREHEADERS = 1
 250 };
 251
 252 extern void create_preheaders (int);
 253 extern void force_single_succ_latches (void);
 254
 255 extern void verify_loop_structure (void);
 256
 257 /* Loop analysis.  */
 258 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
 259 extern unsigned expected_loop_iterations (const struct loop *);
 260 extern rtx doloop_condition_get (rtx);
 261
 262 /* Loop manipulation.  */
 263 extern bool can_duplicate_loop_p (struct loop *loop);
 264
 265 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 266                                            duplicate_loop_to_header_edge.  */
 267 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 268                                            field of newly create BB.  */
 269 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 270                                            a complete peeling.  */
 271
 272 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 273 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 274                                            unsigned, sbitmap, edge,
 275                                            VEC (edge, heap) **, int);
 276 extern struct loop *loopify (edge, edge,
 277                              basic_block, edge, edge, bool,
 278                              unsigned, unsigned);
 279 struct loop * loop_version (struct loop *, void *,
 280                             basic_block *, unsigned, unsigned, unsigned, bool);
 281 extern bool remove_path (edge);
 282 void scale_loop_frequencies (struct loop *, int, int);
 283
 284 /* Induction variable analysis.  */
 285
 286 /* The description of induction variable.  The things are a bit complicated
 287    due to need to handle subregs and extends.  The value of the object described
 288    by it can be obtained as follows (all computations are done in extend_mode):
 289
 290    Value in i-th iteration is
 291      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 292
 293    If first_special is true, the value in the first iteration is
 294      delta + mult * base
 295
 296    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 297      subreg_{mode} (base + i * step)
 298
 299    The get_iv_value function can be used to obtain these expressions.
 300
 301    ??? Add a third mode field that would specify the mode in that inner
 302    computation is done, which would enable it to be different from the
 303    outer one?  */
 304
 305 struct rtx_iv
 306 {
 307   /* Its base and step (mode of base and step is supposed to be extend_mode,
 308      see the description above).  */
 309   rtx base, step;
 310
 311   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 312   enum rtx_code extend;
 313
 314   /* Operations applied in the extended mode.  */
 315   rtx delta, mult;
 316
 317   /* The mode it is extended to.  */
 318   enum machine_mode extend_mode;
 319
 320   /* The mode the variable iterates in.  */
 321   enum machine_mode mode;
 322
 323   /* Whether the first iteration needs to be handled specially.  */
 324   unsigned first_special : 1;
 325 };
 326
 327 /* The description of an exit from the loop and of the number of iterations
 328    till we take the exit.  */
 329
 330 struct niter_desc
 331 {
 332   /* The edge out of the loop.  */
 333   edge out_edge;
 334
 335   /* The other edge leading from the condition.  */
 336   edge in_edge;
 337
 338   /* True if we are able to say anything about number of iterations of the
 339      loop.  */
 340   bool simple_p;
 341
 342   /* True if the loop iterates the constant number of times.  */
 343   bool const_iter;
 344
 345   /* Number of iterations if constant.  */
 346   unsigned HOST_WIDEST_INT niter;
 347
 348   /* Upper bound on the number of iterations.  */
 349   unsigned HOST_WIDEST_INT niter_max;
 350
 351   /* Assumptions under that the rest of the information is valid.  */
 352   rtx assumptions;
 353
 354   /* Assumptions under that the loop ends before reaching the latch,
 355      even if value of niter_expr says otherwise.  */
 356   rtx noloop_assumptions;
 357
 358   /* Condition under that the loop is infinite.  */
 359   rtx infinite;
 360
 361   /* Whether the comparison is signed.  */
 362   bool signed_p;
 363
 364   /* The mode in that niter_expr should be computed.  */
 365   enum machine_mode mode;
 366
 367   /* The number of iterations of the loop.  */
 368   rtx niter_expr;
 369 };
 370
 371 extern void iv_analysis_loop_init (struct loop *);
 372 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 373 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 374 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 375 extern rtx get_iv_value (struct rtx_iv *, rtx);
 376 extern bool biv_p (rtx, rtx);
 377 extern void find_simple_exit (struct loop *, struct niter_desc *);
 378 extern void iv_analysis_done (void);
 379 extern struct df *iv_current_loop_df (void);
 380
 381 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 382 extern void free_simple_loop_desc (struct loop *loop);
 383
 384 static inline struct niter_desc *
 385 simple_loop_desc (struct loop *loop)
 386 {
 387   return (struct niter_desc *) loop->aux;
 388 }
 389
 390 /* Accessors for the loop structures.  */
 391
 392 /* Returns the loop with index NUM from current_loops.  */
 393
 394 static inline struct loop *
 395 get_loop (unsigned num)
 396 {
 397   return VEC_index (loop_p, current_loops->larray, num);
 398 }
 399
 400 /* Returns the list of loops in current_loops.  */
 401
 402 static inline VEC (loop_p, heap) *
 403 get_loops (void)
 404 {
 405   if (!current_loops)
 406     return NULL;
 407
 408   return current_loops->larray;
 409 }
 410
 411 /* Returns the number of loops in current_loops (including the removed
 412    ones and the fake loop that forms the root of the loop tree).  */
 413
 414 static inline unsigned
 415 number_of_loops (void)
 416 {
 417   if (!current_loops)
 418     return 0;
 419
 420   return VEC_length (loop_p, current_loops->larray);
 421 }
 422
 423 /* Loop iterators.  */
 424
 425 /* Flags for loop iteration.  */
 426
 427 enum li_flags
 428 {
 429   LI_INCLUDE_ROOT = 1,  /* Include the fake root of the loop tree.  */
 430   LI_FROM_INNERMOST = 2,/* Iterate over the loops in the reverse order,
 431                            starting from innermost ones.  */
 432   LI_ONLY_INNERMOST = 4,/* Iterate only over innermost loops.  */
 433   LI_ONLY_OLD = 8       /* Do not traverse the loops created during the
 434                            traversal (this is the default behavior with
 435                            LI_FROM_INNERMOST).  */
 436 };
 437
 438 /* The iterator for loops.  */
 439
 440 typedef struct
 441 {
 442   int idx;              /* Index of the actual loop.  */
 443   int end;              /* Only loops before end should be traversed.  */
 444 } loop_iterator;
 445
 446 static inline void
 447 fel_next (loop_iterator *li, loop_p *loop, unsigned flags)
 448 {
 449   if (flags & LI_FROM_INNERMOST)
 450     {
 451       li->idx--;
 452       for (; li->idx > li->end; li->idx--)
 453         {
 454           *loop = VEC_index (loop_p, current_loops->larray, li->idx);
 455           if (*loop
 456               && (!(flags & LI_ONLY_INNERMOST)
 457                   || (*loop)->inner == NULL))
 458             return;
 459         }
 460     }
 461   else
 462     {
 463       if (!(flags & LI_ONLY_OLD))
 464         li->end = number_of_loops ();
 465       li->idx++;
 466       for (; li->idx < li->end; li->idx++)
 467         {
 468           *loop = VEC_index (loop_p, current_loops->larray, li->idx);
 469           if (*loop
 470               && (!(flags & LI_ONLY_INNERMOST)
 471                   || (*loop)->inner == NULL))
 472             return;
 473         }
 474     }
 475
 476   *loop = NULL;
 477 }
 478
 479 static inline void
 480 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
 481 {
 482   if (!current_loops)
 483     {
 484       li->idx = 0;
 485       li->end = 0;
 486       *loop = NULL;
 487       return;
 488     }
 489
 490   if (flags & LI_FROM_INNERMOST)
 491     {
 492       li->idx = number_of_loops ();
 493       li->end = (flags & LI_INCLUDE_ROOT) ? -1 : 0;
 494     }
 495   else
 496     {
 497       li->idx = (flags & LI_INCLUDE_ROOT) ? -1 : 0;
 498       li->end = number_of_loops ();
 499     }
 500   fel_next (li, loop, flags);
 501 }
 502
 503 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
 504   for (fel_init (&(LI), &(LOOP), FLAGS); \
 505        (LOOP); \
 506        fel_next (&(LI), &(LOOP), FLAGS))
 507
 508 /* The properties of the target.  */
 509
 510 extern unsigned target_avail_regs;      /* Number of available registers.  */
 511 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 512 extern unsigned target_small_cost;      /* The cost for register when there
 513                                            is a free one.  */
 514 extern unsigned target_pres_cost;       /* The cost for register when there are
 515                                            not too many free ones.  */
 516 extern unsigned target_spill_cost;      /* The cost for register when we need
 517                                            to spill.  */
 518
 519 /* Register pressure estimation for induction variable optimizations & loop
 520    invariant motion.  */
 521 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 522 extern void init_set_costs (void);
 523
 524 /* Loop optimizer initialization.  */
 525 extern void loop_optimizer_init (unsigned);
 526 extern void loop_optimizer_finalize (void);
 527
 528 /* Optimization passes.  */
 529 extern void unswitch_loops (void);
 530
 531 enum
 532 {
 533   UAP_PEEL = 1,         /* Enables loop peeling.  */
 534   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 535   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 536 };
 537
 538 extern void unroll_and_peel_loops (int);
 539 extern void doloop_optimize_loops (void);
 540 extern void move_loop_invariants (void);
 541
 542 #endif /* GCC_CFGLOOP_H */