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, 59 Temple Place - Suite 330, Boston, MA
  20 02111-1307, 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   tree bound;           /* The expression whose value is an upper bound on the
  51                            number of executions of anything after ...  */
  52   tree at_stmt;         /* ... this statement during one execution of loop.  */
  53   tree additional;      /* A conjunction of conditions the operands of BOUND
  54                            satisfy.  The additional information about the value
  55                            of the bound may be derived from it.  */
  56   struct nb_iter_bound *next;
  57                         /* The next bound in a list.  */
  58 };
  59
  60 /* Structure to hold information for each natural loop.  */
  61 struct loop
  62 {
  63   /* Index into loops array.  */
  64   int num;
  65
  66   /* Basic block of loop header.  */
  67   basic_block header;
  68
  69   /* Basic block of loop latch.  */
  70   basic_block latch;
  71
  72   /* For loop unrolling/peeling decision.  */
  73   struct lpt_decision lpt_decision;
  74
  75   /* Number of loop insns.  */
  76   unsigned ninsns;
  77
  78   /* Average number of executed insns per iteration.  */
  79   unsigned av_ninsns;
  80
  81   /* The first block in the loop.  This is not necessarily the same as
  82      the loop header.  */
  83   basic_block first;
  84
  85   /* The last block in the loop.  This is not necessarily the same as
  86      the loop latch.  */
  87   basic_block last;
  88
  89   /* Number of blocks contained within the loop.  */
  90   unsigned num_nodes;
  91
  92   /* The loop nesting depth.  */
  93   int depth;
  94
  95   /* Superloops of the loop.  */
  96   struct loop **pred;
  97
  98   /* The height of the loop (enclosed loop levels) within the loop
  99      hierarchy tree.  */
 100   int level;
 101
 102   /* The outer (parent) loop or NULL if outermost loop.  */
 103   struct loop *outer;
 104
 105   /* The first inner (child) loop or NULL if innermost loop.  */
 106   struct loop *inner;
 107
 108   /* Link to the next (sibling) loop.  */
 109   struct loop *next;
 110
 111   /* Loop that is copy of this loop.  */
 112   struct loop *copy;
 113
 114   /* Nonzero if the loop is invalid (e.g., contains setjmp.).  */
 115   int invalid;
 116
 117   /* Auxiliary info specific to a pass.  */
 118   void *aux;
 119
 120   /* The following are currently used by loop.c but they are likely to
 121      disappear when loop.c is replaced and removed.  */
 122
 123   /* The NOTE_INSN_LOOP_BEG.  */
 124   rtx start;
 125
 126   /* The NOTE_INSN_LOOP_END.  */
 127   rtx end;
 128
 129   /* For a rotated loop that is entered near the bottom,
 130      this is the label at the top.  Otherwise it is zero.  */
 131   rtx top;
 132
 133   /* Place in the loop where control enters.  */
 134   rtx scan_start;
 135
 136   /* The position where to sink insns out of the loop.  */
 137   rtx sink;
 138
 139   /* List of all LABEL_REFs which refer to code labels outside the
 140      loop.  Used by routines that need to know all loop exits, such as
 141      final_biv_value and final_giv_value.
 142
 143      This does not include loop exits due to return instructions.
 144      This is because all bivs and givs are pseudos, and hence must be
 145      dead after a return, so the presence of a return does not affect
 146      any of the optimizations that use this info.  It is simpler to
 147      just not include return instructions on this list.  */
 148   rtx exit_labels;
 149
 150   /* The number of LABEL_REFs on exit_labels for this loop and all
 151      loops nested inside it.  */
 152   int exit_count;
 153
 154   /* The probable number of times the loop is executed at runtime.
 155      This is an INTEGER_CST or an expression containing symbolic
 156      names.  Don't access this field directly:
 157      number_of_iterations_in_loop computes and caches the computed
 158      information in this field.  */
 159   tree nb_iterations;
 160
 161   /* An INTEGER_CST estimation of the number of iterations.  NULL_TREE
 162      if there is no estimation.  */
 163   tree estimated_nb_iterations;
 164
 165   /* Upper bound on number of iterations of a loop.  */
 166   struct nb_iter_bound *bounds;
 167
 168   /* If not NULL, loop has just single exit edge stored here (edges to the
 169      EXIT_BLOCK_PTR do not count.  */
 170   edge single_exit;
 171
 172   /* True when the loop does not carry data dependences, and
 173      consequently the iterations can be executed in any order.  False
 174      when the loop carries data dependences, or when the property is
 175      not decidable.  */
 176   bool parallel_p;
 177 };
 178
 179 /* Flags for state of loop structure.  */
 180 enum
 181 {
 182   LOOPS_HAVE_PREHEADERS = 1,
 183   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 184   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
 185   LOOPS_HAVE_MARKED_SINGLE_EXITS = 8
 186 };
 187
 188 /* Structure to hold CFG information about natural loops within a function.  */
 189 struct loops
 190 {
 191   /* Number of natural loops in the function.  */
 192   unsigned num;
 193
 194   /* Array of natural loop descriptors (scanning this array in reverse order
 195      will find the inner loops before their enclosing outer loops).  */
 196   struct loop *array;
 197
 198   /* The above array is unused in new loop infrastructure and is kept only for
 199      purposes of the old loop optimizer.  Instead we store just pointers to
 200      loops here.
 201      Note that a loop in this array may actually be NULL, if the loop
 202      has been removed and the entire loops structure has not been
 203      recomputed since that time.  */
 204   struct loop **parray;
 205
 206   /* Pointer to root of loop hierarchy tree.  */
 207   struct loop *tree_root;
 208
 209   /* Information derived from the CFG.  */
 210   struct cfg
 211   {
 212     /* The ordering of the basic blocks in a depth first search.  */
 213     int *dfs_order;
 214
 215     /* The reverse completion ordering of the basic blocks found in a
 216        depth first search.  */
 217     int *rc_order;
 218   } cfg;
 219
 220   /* Headers shared by multiple loops that should be merged.  */
 221   sbitmap shared_headers;
 222
 223   /* State of loops.  */
 224   int state;
 225 };
 226
 227 /* The loop tree currently optimized.  */
 228
 229 extern struct loops *current_loops;
 230
 231 /* Loop recognition.  */
 232 extern int flow_loops_find (struct loops *);
 233 extern void flow_loops_free (struct loops *);
 234 extern void flow_loops_dump (const struct loops *, FILE *,
 235                              void (*)(const struct loop *, FILE *, int), int);
 236 extern void flow_loop_dump (const struct loop *, FILE *,
 237                             void (*)(const struct loop *, FILE *, int), int);
 238 extern void flow_loop_free (struct loop *);
 239 int flow_loop_nodes_find (basic_block, struct loop *);
 240 void fix_loop_structure (struct loops *, bitmap changed_bbs);
 241 void mark_irreducible_loops (struct loops *);
 242 void mark_single_exit_loops (struct loops *);
 243 extern void create_loop_notes (void);
 244
 245 /* Loop data structure manipulation/querying.  */
 246 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 247 extern void flow_loop_tree_node_remove (struct loop *);
 248 extern bool flow_loop_outside_edge_p (const struct loop *, edge);
 249 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 250 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
 251 extern struct loop * find_common_loop (struct loop *, struct loop *);
 252 struct loop *superloop_at_depth (struct loop *, unsigned);
 253 extern unsigned tree_num_loop_insns (struct loop *);
 254 extern int num_loop_insns (struct loop *);
 255 extern int average_num_loop_insns (struct loop *);
 256 extern unsigned get_loop_level (const struct loop *);
 257 extern bool loop_exit_edge_p (const struct loop *, edge);
 258 extern void mark_loop_exit_edges (struct loops *);
 259
 260 /* Loops & cfg manipulation.  */
 261 extern basic_block *get_loop_body (const struct loop *);
 262 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 263 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 264 extern edge *get_loop_exit_edges (const struct loop *, unsigned *);
 265 extern unsigned num_loop_branches (const struct loop *);
 266
 267 extern edge loop_preheader_edge (const struct loop *);
 268 extern edge loop_latch_edge (const struct loop *);
 269
 270 extern void add_bb_to_loop (basic_block, struct loop *);
 271 extern void remove_bb_from_loops (basic_block);
 272
 273 extern void cancel_loop (struct loops *, struct loop *);
 274 extern void cancel_loop_tree (struct loops *, struct loop *);
 275
 276 extern basic_block loop_split_edge_with (edge, rtx);
 277 extern int fix_loop_placement (struct loop *);
 278
 279 enum
 280 {
 281   CP_SIMPLE_PREHEADERS = 1
 282 };
 283
 284 extern void create_preheaders (struct loops *, int);
 285 extern void force_single_succ_latches (struct loops *);
 286
 287 extern void verify_loop_structure (struct loops *);
 288
 289 /* Loop analysis.  */
 290 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
 291 extern unsigned expected_loop_iterations (const struct loop *);
 292
 293 /* Loop manipulation.  */
 294 extern bool can_duplicate_loop_p (struct loop *loop);
 295
 296 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 297                                            duplicate_loop_to_header_edge.  */
 298
 299 extern struct loop * duplicate_loop (struct loops *, struct loop *,
 300                                      struct loop *);
 301 extern bool duplicate_loop_to_header_edge (struct loop *, edge, struct loops *,
 302                                            unsigned, sbitmap, edge, edge *,
 303                                            unsigned *, int);
 304 extern struct loop *loopify (struct loops *, edge, edge,
 305                              basic_block, edge, edge, bool);
 306 struct loop * loop_version (struct loops *, struct loop *, void *,
 307                             basic_block *);
 308 extern bool remove_path (struct loops *, edge);
 309 extern edge split_loop_bb (basic_block, void *);
 310
 311 /* Induction variable analysis.  */
 312
 313 /* The description of induction variable.  The things are a bit complicated
 314    due to need to handle subregs and extends.  The value of the object described
 315    by it can be obtained as follows (all computations are done in extend_mode):
 316
 317    Value in i-th iteration is
 318      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 319
 320    If first_special is true, the value in the first iteration is
 321      delta + mult * base
 322
 323    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 324      subreg_{mode} (base + i * step)
 325
 326    The get_iv_value function can be used to obtain these expressions.
 327
 328    ??? Add a third mode field that would specify the mode in that inner
 329    computation is done, which would enable it to be different from the
 330    outer one?  */
 331
 332 struct rtx_iv
 333 {
 334   /* Its base and step (mode of base and step is supposed to be extend_mode,
 335      see the description above).  */
 336   rtx base, step;
 337
 338   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 339   enum rtx_code extend;
 340
 341   /* Operations applied in the extended mode.  */
 342   rtx delta, mult;
 343
 344   /* The mode it is extended to.  */
 345   enum machine_mode extend_mode;
 346
 347   /* The mode the variable iterates in.  */
 348   enum machine_mode mode;
 349
 350   /* Whether we have already filled the remaining fields.  */
 351   unsigned analysed : 1;
 352
 353   /* Whether the first iteration needs to be handled specially.  */
 354   unsigned first_special : 1;
 355 };
 356
 357 /* The description of an exit from the loop and of the number of iterations
 358    till we take the exit.  */
 359
 360 struct niter_desc
 361 {
 362   /* The edge out of the loop.  */
 363   edge out_edge;
 364
 365   /* The other edge leading from the condition.  */
 366   edge in_edge;
 367
 368   /* True if we are able to say anything about number of iterations of the
 369      loop.  */
 370   bool simple_p;
 371
 372   /* True if the loop iterates the constant number of times.  */
 373   bool const_iter;
 374
 375   /* Number of iterations if constant.  */
 376   unsigned HOST_WIDEST_INT niter;
 377
 378   /* Upper bound on the number of iterations.  */
 379   unsigned HOST_WIDEST_INT niter_max;
 380
 381   /* Assumptions under that the rest of the information is valid.  */
 382   rtx assumptions;
 383
 384   /* Assumptions under that the loop ends before reaching the latch,
 385      even if value of niter_expr says otherwise.  */
 386   rtx noloop_assumptions;
 387
 388   /* Condition under that the loop is infinite.  */
 389   rtx infinite;
 390
 391   /* Whether the comparison is signed.  */
 392   bool signed_p;
 393
 394   /* The mode in that niter_expr should be computed.  */
 395   enum machine_mode mode;
 396
 397   /* The number of iterations of the loop.  */
 398   rtx niter_expr;
 399 };
 400
 401 extern void iv_analysis_loop_init (struct loop *);
 402 extern rtx iv_get_reaching_def (rtx, rtx);
 403 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 404 extern rtx get_iv_value (struct rtx_iv *, rtx);
 405 extern bool biv_p (rtx, rtx);
 406 extern void find_simple_exit (struct loop *, struct niter_desc *);
 407 extern void iv_analysis_done (void);
 408
 409 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 410 extern void free_simple_loop_desc (struct loop *loop);
 411
 412 static inline struct niter_desc *
 413 simple_loop_desc (struct loop *loop)
 414 {
 415   return loop->aux;
 416 }
 417
 418 /* The properties of the target.  */
 419
 420 extern unsigned target_avail_regs;      /* Number of available registers.  */
 421 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 422 extern unsigned target_small_cost;      /* The cost for register when there
 423                                            is a free one.  */
 424 extern unsigned target_pres_cost;       /* The cost for register when there are
 425                                            not too many free ones.  */
 426 extern unsigned target_spill_cost;      /* The cost for register when we need
 427                                            to spill.  */
 428
 429 /* Register pressure estimation for induction variable optimizations & loop
 430    invariant motion.  */
 431 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 432 extern void init_set_costs (void);
 433
 434 /* Loop optimizer initialization.  */
 435 extern struct loops *loop_optimizer_init (FILE *);
 436 extern void loop_optimizer_finalize (struct loops *, FILE *);
 437
 438 /* Optimization passes.  */
 439 extern void unswitch_loops (struct loops *);
 440
 441 enum
 442 {
 443   UAP_PEEL = 1,         /* Enables loop peeling.  */
 444   UAP_UNROLL = 2,       /* Enables peeling of loops if it seems profitable.  */
 445   UAP_UNROLL_ALL = 4    /* Enables peeling of all loops.  */
 446 };
 447
 448 extern void unroll_and_peel_loops (struct loops *, int);
 449 extern void doloop_optimize_loops (struct loops *);
 450 extern void move_loop_invariants (struct loops *);
 451 extern void record_estimate (struct loop *, tree, tree, tree);
 452
 453 /* Old loop optimizer interface.  */
 454
 455 /* Flags passed to loop_optimize.  */
 456 #define LOOP_PREFETCH 1
 457
 458 extern void loop_optimize (rtx, FILE *, int);
 459
 460 #endif /* GCC_CFGLOOP_H */