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 direcly, 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 (const struct loops *, 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 (struct loops *, bitmap changed_bbs);
 201 void mark_irreducible_loops (struct loops *);
 202 void mark_single_exit_loops (struct loops *);
 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 (struct loops *);
 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 loops *, 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 (struct loops *, int);
 243 extern void force_single_succ_latches (struct loops *);
 244
 245 extern void verify_loop_structure (struct loops *);
 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 loops *, struct loop *,
 263                                      struct loop *);
 264 extern bool duplicate_loop_to_header_edge (struct loop *, edge, struct loops *,
 265                                            unsigned, sbitmap, edge, edge *,
 266                                            unsigned *, int);
 267 extern struct loop *loopify (struct loops *, edge, edge,
 268                              basic_block, edge, edge, bool);
 269 struct loop * loop_version (struct loops *, struct loop *, void *,
 270                             basic_block *, bool);
 271 extern bool remove_path (struct loops *, edge);
 272
 273 /* Induction variable analysis.  */
 274
 275 /* The description of induction variable.  The things are a bit complicated
 276    due to need to handle subregs and extends.  The value of the object described
 277    by it can be obtained as follows (all computations are done in extend_mode):
 278
 279    Value in i-th iteration is
 280      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 281
 282    If first_special is true, the value in the first iteration is
 283      delta + mult * base
 284
 285    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 286      subreg_{mode} (base + i * step)
 287
 288    The get_iv_value function can be used to obtain these expressions.
 289
 290    ??? Add a third mode field that would specify the mode in that inner
 291    computation is done, which would enable it to be different from the
 292    outer one?  */
 293
 294 struct rtx_iv
 295 {
 296   /* Its base and step (mode of base and step is supposed to be extend_mode,
 297      see the description above).  */
 298   rtx base, step;
 299
 300   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 301   enum rtx_code extend;
 302
 303   /* Operations applied in the extended mode.  */
 304   rtx delta, mult;
 305
 306   /* The mode it is extended to.  */
 307   enum machine_mode extend_mode;
 308
 309   /* The mode the variable iterates in.  */
 310   enum machine_mode mode;
 311
 312   /* Whether the first iteration needs to be handled specially.  */
 313   unsigned first_special : 1;
 314 };
 315
 316 /* The description of an exit from the loop and of the number of iterations
 317    till we take the exit.  */
 318
 319 struct niter_desc
 320 {
 321   /* The edge out of the loop.  */
 322   edge out_edge;
 323
 324   /* The other edge leading from the condition.  */
 325   edge in_edge;
 326
 327   /* True if we are able to say anything about number of iterations of the
 328      loop.  */
 329   bool simple_p;
 330
 331   /* True if the loop iterates the constant number of times.  */
 332   bool const_iter;
 333
 334   /* Number of iterations if constant.  */
 335   unsigned HOST_WIDEST_INT niter;
 336
 337   /* Upper bound on the number of iterations.  */
 338   unsigned HOST_WIDEST_INT niter_max;
 339
 340   /* Assumptions under that the rest of the information is valid.  */
 341   rtx assumptions;
 342
 343   /* Assumptions under that the loop ends before reaching the latch,
 344      even if value of niter_expr says otherwise.  */
 345   rtx noloop_assumptions;
 346
 347   /* Condition under that the loop is infinite.  */
 348   rtx infinite;
 349
 350   /* Whether the comparison is signed.  */
 351   bool signed_p;
 352
 353   /* The mode in that niter_expr should be computed.  */
 354   enum machine_mode mode;
 355
 356   /* The number of iterations of the loop.  */
 357   rtx niter_expr;
 358 };
 359
 360 extern void iv_analysis_loop_init (struct loop *);
 361 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 362 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 363 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 364 extern rtx get_iv_value (struct rtx_iv *, rtx);
 365 extern bool biv_p (rtx, rtx);
 366 extern void find_simple_exit (struct loop *, struct niter_desc *);
 367 extern void iv_analysis_done (void);
 368 extern struct df *iv_current_loop_df (void);
 369
 370 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 371 extern void free_simple_loop_desc (struct loop *loop);
 372
 373 static inline struct niter_desc *
 374 simple_loop_desc (struct loop *loop)
 375 {
 376   return (struct niter_desc *) loop->aux;
 377 }
 378
 379 /* The properties of the target.  */
 380
 381 extern unsigned target_avail_regs;      /* Number of available registers.  */
 382 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 383 extern unsigned target_small_cost;      /* The cost for register when there
 384                                            is a free one.  */
 385 extern unsigned target_pres_cost;       /* The cost for register when there are
 386                                            not too many free ones.  */
 387 extern unsigned target_spill_cost;      /* The cost for register when we need
 388                                            to spill.  */
 389
 390 /* Register pressure estimation for induction variable optimizations & loop
 391    invariant motion.  */
 392 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 393 extern void init_set_costs (void);
 394
 395 /* Loop optimizer initialization.  */
 396 extern void loop_optimizer_init (unsigned);
 397 extern void loop_optimizer_finalize (void);
 398
 399 /* Optimization passes.  */
 400 extern void unswitch_loops (struct loops *);
 401
 402 enum
 403 {
 404   UAP_PEEL = 1,         /* Enables loop peeling.  */
 405   UAP_UNROLL = 2,       /* Enables unrolling of loops if it seems profitable.  */
 406   UAP_UNROLL_ALL = 4    /* Enables unrolling of all loops.  */
 407 };
 408
 409 extern void unroll_and_peel_loops (struct loops *, int);
 410 extern void doloop_optimize_loops (struct loops *);
 411 extern void move_loop_invariants (struct loops *);
 412
 413 #endif /* GCC_CFGLOOP_H */