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 /* Structure to hold information for each natural loop.  */
  78 struct loop
  79 {
  80   /* Index into loops array.  */
  81   int num;
  82
  83   /* Basic block of loop header.  */
  84   basic_block header;
  85
  86   /* Basic block of loop latch.  */
  87   basic_block latch;
  88
  89   /* For loop unrolling/peeling decision.  */
  90   struct lpt_decision lpt_decision;
  91
  92   /* Number of loop insns.  */
  93   unsigned ninsns;
  94
  95   /* Average number of executed insns per iteration.  */
  96   unsigned av_ninsns;
  97
  98   /* Number of blocks contained within the loop.  */
  99   unsigned num_nodes;
 100
 101   /* The loop nesting depth.  */
 102   int depth;
 103
 104   /* Superloops of the loop.  */
 105   struct loop **pred;
 106
 107   /* The outer (parent) loop or NULL if outermost loop.  */
 108   struct loop *outer;
 109
 110   /* The first inner (child) loop or NULL if innermost loop.  */
 111   struct loop *inner;
 112
 113   /* Link to the next (sibling) loop.  */
 114   struct loop *next;
 115
 116   /* Loop that is copy of this loop.  */
 117   struct loop *copy;
 118
 119   /* Auxiliary info specific to a pass.  */
 120   void *aux;
 121
 122   /* The number of times the latch of the loop is executed.
 123      This is an INTEGER_CST or an expression containing symbolic
 124      names.  Don't access this field directly:
 125      number_of_latch_executions computes and caches the computed
 126      information in this field.  */
 127   tree nb_iterations;
 128
 129   /* An integer estimation of the number of iterations.  Estimate_state
 130      describes what is the state of the estimation.  */
 131   enum
 132     {
 133       /* Estimate was not computed yet.  */
 134       EST_NOT_COMPUTED,
 135       /* Estimate was computed, but we could derive no useful bound.  */
 136       EST_NOT_AVAILABLE,
 137       /* Estimate is ready.  */
 138       EST_AVAILABLE
 139     } estimate_state;
 140   double_int estimated_nb_iterations;
 141
 142   /* Upper bound on number of iterations of a loop.  */
 143   struct nb_iter_bound *bounds;
 144
 145   /* If not NULL, loop has just single exit edge stored here (edges to the
 146      EXIT_BLOCK_PTR do not count.  Do not use directly; this field should
 147      only be accessed via single_exit/set_single_exit functions.  */
 148   edge single_exit_;
 149 };
 150
 151 /* Flags for state of loop structure.  */
 152 enum
 153 {
 154   LOOPS_HAVE_PREHEADERS = 1,
 155   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 156   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
 157   LOOPS_HAVE_MARKED_SINGLE_EXITS = 8
 158 };
 159
 160 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 161                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 162
 163 typedef struct loop *loop_p;
 164 DEF_VEC_P (loop_p);
 165 DEF_VEC_ALLOC_P (loop_p, heap);
 166
 167 /* Structure to hold CFG information about natural loops within a function.  */
 168 struct loops
 169 {
 170   /* State of loops.  */
 171   int state;
 172
 173   /* Array of the loops.  */
 174   VEC (loop_p, heap) *larray;
 175
 176   /* Pointer to root of loop hierarchy tree.  */
 177   struct loop *tree_root;
 178 };
 179
 180 /* Loop recognition.  */
 181 extern int flow_loops_find (struct loops *);
 182 extern void flow_loops_free (struct loops *);
 183 extern void flow_loops_dump (FILE *,
 184                              void (*)(const struct loop *, FILE *, int), int);
 185 extern void flow_loop_dump (const struct loop *, FILE *,
 186                             void (*)(const struct loop *, FILE *, int), int);
 187 extern void flow_loop_free (struct loop *);
 188 int flow_loop_nodes_find (basic_block, struct loop *);
 189 void fix_loop_structure (bitmap changed_bbs);
 190 void mark_irreducible_loops (void);
 191 void mark_single_exit_loops (void);
 192
 193 /* Loop data structure manipulation/querying.  */
 194 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 195 extern void flow_loop_tree_node_remove (struct loop *);
 196 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 197 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
 198 extern struct loop * find_common_loop (struct loop *, struct loop *);
 199 struct loop *superloop_at_depth (struct loop *, unsigned);
 200 extern unsigned tree_num_loop_insns (struct loop *);
 201 extern int num_loop_insns (struct loop *);
 202 extern int average_num_loop_insns (struct loop *);
 203 extern unsigned get_loop_level (const struct loop *);
 204 extern bool loop_exit_edge_p (const struct loop *, edge);
 205 extern void mark_loop_exit_edges (void);
 206
 207 /* Loops & cfg manipulation.  */
 208 extern basic_block *get_loop_body (const struct loop *);
 209 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 210 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 211 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
 212 edge single_exit (const struct loop *);
 213 void set_single_exit (struct loop *, edge);
 214 extern unsigned num_loop_branches (const struct loop *);
 215
 216 extern edge loop_preheader_edge (const struct loop *);
 217 extern edge loop_latch_edge (const struct loop *);
 218
 219 extern void add_bb_to_loop (basic_block, struct loop *);
 220 extern void remove_bb_from_loops (basic_block);
 221
 222 extern void cancel_loop_tree (struct loop *);
 223 extern void delete_loop (struct loop *);
 224
 225 extern int fix_loop_placement (struct loop *);
 226
 227 enum
 228 {
 229   CP_SIMPLE_PREHEADERS = 1
 230 };
 231
 232 extern void create_preheaders (int);
 233 extern void force_single_succ_latches (void);
 234
 235 extern void verify_loop_structure (void);
 236
 237 /* Loop analysis.  */
 238 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
 239 extern unsigned expected_loop_iterations (const struct loop *);
 240 extern rtx doloop_condition_get (rtx);
 241
 242 /* Loop manipulation.  */
 243 extern bool can_duplicate_loop_p (struct loop *loop);
 244
 245 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 246                                            duplicate_loop_to_header_edge.  */
 247 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 248                                            field of newly create BB.  */
 249 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 250                                            a complete peeling.  */
 251
 252 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 253 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 254                                            unsigned, sbitmap, edge,
 255                                            VEC (edge, heap) **, int);
 256 extern struct loop *loopify (edge, edge,
 257                              basic_block, edge, edge, bool,
 258                              unsigned, unsigned);
 259 struct loop * loop_version (struct loop *, void *,
 260                             basic_block *, unsigned, unsigned, unsigned, bool);
 261 extern bool remove_path (edge);
 262 void scale_loop_frequencies (struct loop *, int, int);
 263
 264 /* Induction variable analysis.  */
 265
 266 /* The description of induction variable.  The things are a bit complicated
 267    due to need to handle subregs and extends.  The value of the object described
 268    by it can be obtained as follows (all computations are done in extend_mode):
 269
 270    Value in i-th iteration is
 271      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 272
 273    If first_special is true, the value in the first iteration is
 274      delta + mult * base
 275
 276    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 277      subreg_{mode} (base + i * step)
 278
 279    The get_iv_value function can be used to obtain these expressions.
 280
 281    ??? Add a third mode field that would specify the mode in that inner
 282    computation is done, which would enable it to be different from the
 283    outer one?  */
 284
 285 struct rtx_iv
 286 {
 287   /* Its base and step (mode of base and step is supposed to be extend_mode,
 288      see the description above).  */
 289   rtx base, step;
 290
 291   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 292   enum rtx_code extend;
 293
 294   /* Operations applied in the extended mode.  */
 295   rtx delta, mult;
 296
 297   /* The mode it is extended to.  */
 298   enum machine_mode extend_mode;
 299
 300   /* The mode the variable iterates in.  */
 301   enum machine_mode mode;
 302
 303   /* Whether the first iteration needs to be handled specially.  */
 304   unsigned first_special : 1;
 305 };
 306
 307 /* The description of an exit from the loop and of the number of iterations
 308    till we take the exit.  */
 309
 310 struct niter_desc
 311 {
 312   /* The edge out of the loop.  */
 313   edge out_edge;
 314
 315   /* The other edge leading from the condition.  */
 316   edge in_edge;
 317
 318   /* True if we are able to say anything about number of iterations of the
 319      loop.  */
 320   bool simple_p;
 321
 322   /* True if the loop iterates the constant number of times.  */
 323   bool const_iter;
 324
 325   /* Number of iterations if constant.  */
 326   unsigned HOST_WIDEST_INT niter;
 327
 328   /* Upper bound on the number of iterations.  */
 329   unsigned HOST_WIDEST_INT niter_max;
 330
 331   /* Assumptions under that the rest of the information is valid.  */
 332   rtx assumptions;
 333
 334   /* Assumptions under that the loop ends before reaching the latch,
 335      even if value of niter_expr says otherwise.  */
 336   rtx noloop_assumptions;
 337
 338   /* Condition under that the loop is infinite.  */
 339   rtx infinite;
 340
 341   /* Whether the comparison is signed.  */
 342   bool signed_p;
 343
 344   /* The mode in that niter_expr should be computed.  */
 345   enum machine_mode mode;
 346
 347   /* The number of iterations of the loop.  */
 348   rtx niter_expr;
 349 };
 350
 351 extern void iv_analysis_loop_init (struct loop *);
 352 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 353 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 354 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 355 extern rtx get_iv_value (struct rtx_iv *, rtx);
 356 extern bool biv_p (rtx, rtx);
 357 extern void find_simple_exit (struct loop *, struct niter_desc *);
 358 extern void iv_analysis_done (void);
 359 extern struct df *iv_current_loop_df (void);
 360
 361 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 362 extern void free_simple_loop_desc (struct loop *loop);
 363
 364 static inline struct niter_desc *
 365 simple_loop_desc (struct loop *loop)
 366 {
 367   return (struct niter_desc *) loop->aux;
 368 }
 369
 370 /* Accessors for the loop structures.  */
 371
 372 /* Returns the loop with index NUM from current_loops.  */
 373
 374 static inline struct loop *
 375 get_loop (unsigned num)
 376 {
 377   return VEC_index (loop_p, current_loops->larray, num);
 378 }
 379
 380 /* Returns the list of loops in current_loops.  */
 381
 382 static inline VEC (loop_p, heap) *
 383 get_loops (void)
 384 {
 385   if (!current_loops)
 386     return NULL;
 387
 388   return current_loops->larray;
 389 }
 390
 391 /* Returns the number of loops in current_loops (including the removed
 392    ones and the fake loop that forms the root of the loop tree).  */
 393
 394 static inline unsigned
 395 number_of_loops (void)
 396 {
 397   if (!current_loops)
 398     return 0;
 399
 400   return VEC_length (loop_p, current_loops->larray);
 401 }
 402
 403 /* Loop iterators.  */
 404
 405 /* Flags for loop iteration.  */
 406
 407 enum li_flags
 408 {
 409   LI_INCLUDE_ROOT,      /* Include the fake root of the loop tree.  */
 410   LI_FROM_INNERMOST,    /* Iterate over the loops in the reverse order,
 411                            starting from innermost ones.  */
 412   LI_ONLY_INNERMOST,    /* Iterate only over innermost loops.  */
 413   LI_ONLY_OLD           /* Do not traverse the loops created during the
 414                            traversal (this is the default behavior with
 415                            LI_FROM_INNERMOST).  */
 416 };
 417
 418 /* The iterator for loops.  */
 419
 420 typedef struct
 421 {
 422   int idx;              /* Index of the actual loop.  */
 423   int end;              /* Only loops before end should be traversed.  */
 424 } loop_iterator;
 425
 426 static inline void
 427 fel_next (loop_iterator *li, loop_p *loop, unsigned flags)
 428 {
 429   if (flags & LI_FROM_INNERMOST)
 430     {
 431       li->idx--;
 432       for (; li->idx > li->end; li->idx--)
 433         {
 434           *loop = VEC_index (loop_p, current_loops->larray, li->idx);
 435           if (*loop
 436               && (!(flags & LI_ONLY_INNERMOST)
 437                   || (*loop)->inner == NULL))
 438             return;
 439         }
 440     }
 441   else
 442     {
 443       if (!(flags & LI_ONLY_OLD))
 444         li->end = number_of_loops ();
 445       li->idx++;
 446       for (; li->idx < li->end; li->idx++)
 447         {
 448           *loop = VEC_index (loop_p, current_loops->larray, li->idx);
 449           if (*loop
 450               && (!(flags & LI_ONLY_INNERMOST)
 451                   || (*loop)->inner == NULL))
 452             return;
 453         }
 454     }
 455
 456   *loop = NULL;
 457 }
 458
 459 static inline void
 460 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
 461 {
 462   if (!current_loops)
 463     {
 464       li->idx = 0;
 465       li->end = 0;
 466       *loop = NULL;
 467       return;
 468     }
 469
 470   if (flags & LI_FROM_INNERMOST)
 471     {
 472       li->idx = number_of_loops ();
 473       li->end = (flags & LI_INCLUDE_ROOT) ? -1 : 0;
 474     }
 475   else
 476     {
 477       li->idx = (flags & LI_INCLUDE_ROOT) ? -1 : 0;
 478       li->end = number_of_loops ();
 479     }
 480   fel_next (li, loop, flags);
 481 }
 482
 483 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
 484   for (fel_init (&(LI), &(LOOP), FLAGS); \
 485        (LOOP); \
 486        fel_next (&(LI), &(LOOP), FLAGS))
 487
 488 /* The properties of the target.  */
 489
 490 extern unsigned target_avail_regs;      /* Number of available registers.  */
 491 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 492 extern unsigned target_small_cost;      /* The cost for register when there
 493                                            is a free one.  */
 494 extern unsigned target_pres_cost;       /* The cost for register when there are
 495                                            not too many free ones.  */
 496 extern unsigned target_spill_cost;      /* The cost for register when we need
 497                                            to spill.  */
 498
 499 /* Register pressure estimation for induction variable optimizations & loop
 500    invariant motion.  */
 501 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 502 extern void init_set_costs (void);
 503
 504 /* Loop optimizer initialization.  */
 505 extern void loop_optimizer_init (unsigned);
 506 extern void loop_optimizer_finalize (void);
 507
 508 /* Optimization passes.  */
 509 extern void unswitch_loops (void);
 510
 511 enum
 512 {
 513   UAP_PEEL = 1,         /* Enables loop peeling.  */
 514   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 515   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 516 };
 517
 518 extern void unroll_and_peel_loops (int);
 519 extern void doloop_optimize_loops (void);
 520 extern void move_loop_invariants (void);
 521
 522 #endif /* GCC_CFGLOOP_H */