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 probable number of times the loop is executed at runtime.
 123      This is an INTEGER_CST or an expression containing symbolic
 124      names.  Don't access this field directly:
 125      number_of_iterations_in_loop 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   /* True when the loop does not carry data dependences, and
 151      consequently the iterations can be executed in any order.  False
 152      when the loop carries data dependences, or when the property is
 153      not decidable.  */
 154   bool parallel_p;
 155 };
 156
 157 /* Flags for state of loop structure.  */
 158 enum
 159 {
 160   LOOPS_HAVE_PREHEADERS = 1,
 161   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 162   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
 163   LOOPS_HAVE_MARKED_SINGLE_EXITS = 8
 164 };
 165
 166 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 167                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 168
 169 /* Structure to hold CFG information about natural loops within a function.  */
 170 struct loops
 171 {
 172   /* Number of natural loops in the function.  */
 173   unsigned num;
 174
 175   /* State of loops.  */
 176   int state;
 177
 178   /* We store just pointers to loops here.
 179      Note that a loop in this array may actually be NULL, if the loop
 180      has been removed and the entire loops structure has not been
 181      recomputed since that time.  */
 182   struct loop **parray;
 183
 184   /* Pointer to root of loop hierarchy tree.  */
 185   struct loop *tree_root;
 186
 187   /* Headers shared by multiple loops that should be merged.  */
 188   sbitmap shared_headers;
 189 };
 190
 191 /* Loop recognition.  */
 192 extern int flow_loops_find (struct loops *);
 193 extern void flow_loops_free (struct loops *);
 194 extern void flow_loops_dump (FILE *,
 195                              void (*)(const struct loop *, FILE *, int), int);
 196 extern void flow_loop_dump (const struct loop *, FILE *,
 197                             void (*)(const struct loop *, FILE *, int), int);
 198 extern void flow_loop_free (struct loop *);
 199 int flow_loop_nodes_find (basic_block, struct loop *);
 200 void fix_loop_structure (bitmap changed_bbs);
 201 void mark_irreducible_loops (void);
 202 void mark_single_exit_loops (void);
 203
 204 /* Loop data structure manipulation/querying.  */
 205 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 206 extern void flow_loop_tree_node_remove (struct loop *);
 207 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 208 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
 209 extern struct loop * find_common_loop (struct loop *, struct loop *);
 210 struct loop *superloop_at_depth (struct loop *, unsigned);
 211 extern unsigned tree_num_loop_insns (struct loop *);
 212 extern int num_loop_insns (struct loop *);
 213 extern int average_num_loop_insns (struct loop *);
 214 extern unsigned get_loop_level (const struct loop *);
 215 extern bool loop_exit_edge_p (const struct loop *, edge);
 216 extern void mark_loop_exit_edges (void);
 217
 218 /* Loops & cfg manipulation.  */
 219 extern basic_block *get_loop_body (const struct loop *);
 220 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 221 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 222 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
 223 edge single_exit (const struct loop *);
 224 void set_single_exit (struct loop *, edge);
 225 extern unsigned num_loop_branches (const struct loop *);
 226
 227 extern edge loop_preheader_edge (const struct loop *);
 228 extern edge loop_latch_edge (const struct loop *);
 229
 230 extern void add_bb_to_loop (basic_block, struct loop *);
 231 extern void remove_bb_from_loops (basic_block);
 232
 233 extern void cancel_loop_tree (struct loop *);
 234
 235 extern int fix_loop_placement (struct loop *);
 236
 237 enum
 238 {
 239   CP_SIMPLE_PREHEADERS = 1
 240 };
 241
 242 extern void create_preheaders (int);
 243 extern void force_single_succ_latches (void);
 244
 245 extern void verify_loop_structure (void);
 246
 247 /* Loop analysis.  */
 248 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
 249 extern unsigned expected_loop_iterations (const struct loop *);
 250 extern rtx doloop_condition_get (rtx);
 251
 252 /* Loop manipulation.  */
 253 extern bool can_duplicate_loop_p (struct loop *loop);
 254
 255 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 256                                            duplicate_loop_to_header_edge.  */
 257 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 258                                            field of newly create BB.  */
 259 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 260                                            a complete peeling.  */
 261
 262 extern struct loop * duplicate_loop (struct loop *, struct loop *);
 263 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
 264                                            unsigned, sbitmap, edge, edge *,
 265                                            unsigned *, int);
 266 extern struct loop *loopify (edge, edge,
 267                              basic_block, edge, edge, bool);
 268 struct loop * loop_version (struct loop *, void *,
 269                             basic_block *, bool);
 270 extern bool remove_path (edge);
 271
 272 /* Induction variable analysis.  */
 273
 274 /* The description of induction variable.  The things are a bit complicated
 275    due to need to handle subregs and extends.  The value of the object described
 276    by it can be obtained as follows (all computations are done in extend_mode):
 277
 278    Value in i-th iteration is
 279      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 280
 281    If first_special is true, the value in the first iteration is
 282      delta + mult * base
 283
 284    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 285      subreg_{mode} (base + i * step)
 286
 287    The get_iv_value function can be used to obtain these expressions.
 288
 289    ??? Add a third mode field that would specify the mode in that inner
 290    computation is done, which would enable it to be different from the
 291    outer one?  */
 292
 293 struct rtx_iv
 294 {
 295   /* Its base and step (mode of base and step is supposed to be extend_mode,
 296      see the description above).  */
 297   rtx base, step;
 298
 299   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 300   enum rtx_code extend;
 301
 302   /* Operations applied in the extended mode.  */
 303   rtx delta, mult;
 304
 305   /* The mode it is extended to.  */
 306   enum machine_mode extend_mode;
 307
 308   /* The mode the variable iterates in.  */
 309   enum machine_mode mode;
 310
 311   /* Whether the first iteration needs to be handled specially.  */
 312   unsigned first_special : 1;
 313 };
 314
 315 /* The description of an exit from the loop and of the number of iterations
 316    till we take the exit.  */
 317
 318 struct niter_desc
 319 {
 320   /* The edge out of the loop.  */
 321   edge out_edge;
 322
 323   /* The other edge leading from the condition.  */
 324   edge in_edge;
 325
 326   /* True if we are able to say anything about number of iterations of the
 327      loop.  */
 328   bool simple_p;
 329
 330   /* True if the loop iterates the constant number of times.  */
 331   bool const_iter;
 332
 333   /* Number of iterations if constant.  */
 334   unsigned HOST_WIDEST_INT niter;
 335
 336   /* Upper bound on the number of iterations.  */
 337   unsigned HOST_WIDEST_INT niter_max;
 338
 339   /* Assumptions under that the rest of the information is valid.  */
 340   rtx assumptions;
 341
 342   /* Assumptions under that the loop ends before reaching the latch,
 343      even if value of niter_expr says otherwise.  */
 344   rtx noloop_assumptions;
 345
 346   /* Condition under that the loop is infinite.  */
 347   rtx infinite;
 348
 349   /* Whether the comparison is signed.  */
 350   bool signed_p;
 351
 352   /* The mode in that niter_expr should be computed.  */
 353   enum machine_mode mode;
 354
 355   /* The number of iterations of the loop.  */
 356   rtx niter_expr;
 357 };
 358
 359 extern void iv_analysis_loop_init (struct loop *);
 360 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 361 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 362 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 363 extern rtx get_iv_value (struct rtx_iv *, rtx);
 364 extern bool biv_p (rtx, rtx);
 365 extern void find_simple_exit (struct loop *, struct niter_desc *);
 366 extern void iv_analysis_done (void);
 367 extern struct df *iv_current_loop_df (void);
 368
 369 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 370 extern void free_simple_loop_desc (struct loop *loop);
 371
 372 static inline struct niter_desc *
 373 simple_loop_desc (struct loop *loop)
 374 {
 375   return (struct niter_desc *) loop->aux;
 376 }
 377
 378 /* The properties of the target.  */
 379
 380 extern unsigned target_avail_regs;      /* Number of available registers.  */
 381 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 382 extern unsigned target_small_cost;      /* The cost for register when there
 383                                            is a free one.  */
 384 extern unsigned target_pres_cost;       /* The cost for register when there are
 385                                            not too many free ones.  */
 386 extern unsigned target_spill_cost;      /* The cost for register when we need
 387                                            to spill.  */
 388
 389 /* Register pressure estimation for induction variable optimizations & loop
 390    invariant motion.  */
 391 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 392 extern void init_set_costs (void);
 393
 394 /* Loop optimizer initialization.  */
 395 extern void loop_optimizer_init (unsigned);
 396 extern void loop_optimizer_finalize (void);
 397
 398 /* Optimization passes.  */
 399 extern void unswitch_loops (void);
 400
 401 enum
 402 {
 403   UAP_PEEL = 1,         /* Enables loop peeling.  */
 404   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 405   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 406 };
 407
 408 extern void unroll_and_peel_loops (int);
 409 extern void doloop_optimize_loops (void);
 410 extern void move_loop_invariants (void);
 411
 412 #endif /* GCC_CFGLOOP_H */