gcc/cfgloop.h

   1 /* Natural loop functions
   2    Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
   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   /* Basic block of loop preheader or NULL if it does not exist.  */
  73   basic_block pre_header;
  74
  75   /* For loop unrolling/peeling decision.  */
  76   struct lpt_decision lpt_decision;
  77
  78   /* Number of loop insns.  */
  79   unsigned ninsns;
  80
  81   /* Average number of executed insns per iteration.  */
  82   unsigned av_ninsns;
  83
  84   /* Array of edges along the preheader extended basic block trace.
  85      The source of the first edge is the root node of preheader
  86      extended basic block, if it exists.  */
  87   edge *pre_header_edges;
  88
  89   /* Number of edges along the pre_header extended basic block trace.  */
  90   int num_pre_header_edges;
  91
  92   /* The first block in the loop.  This is not necessarily the same as
  93      the loop header.  */
  94   basic_block first;
  95
  96   /* The last block in the loop.  This is not necessarily the same as
  97      the loop latch.  */
  98   basic_block last;
  99
 100   /* Bitmap of blocks contained within the loop.  */
 101   sbitmap nodes;
 102
 103   /* Number of blocks contained within the loop.  */
 104   unsigned num_nodes;
 105
 106   /* Array of edges that enter the loop.  */
 107   edge *entry_edges;
 108
 109   /* Number of edges that enter the loop.  */
 110   int num_entries;
 111
 112   /* Array of edges that exit the loop.  */
 113   edge *exit_edges;
 114
 115   /* Number of edges that exit the loop.  */
 116   int num_exits;
 117
 118   /* Bitmap of blocks that dominate all exits of the loop.  */
 119   sbitmap exits_doms;
 120
 121   /* The loop nesting depth.  */
 122   int depth;
 123
 124   /* Superloops of the loop.  */
 125   struct loop **pred;
 126
 127   /* The height of the loop (enclosed loop levels) within the loop
 128      hierarchy tree.  */
 129   int level;
 130
 131   /* The outer (parent) loop or NULL if outermost loop.  */
 132   struct loop *outer;
 133
 134   /* The first inner (child) loop or NULL if innermost loop.  */
 135   struct loop *inner;
 136
 137   /* Link to the next (sibling) loop.  */
 138   struct loop *next;
 139
 140   /* Loop that is copy of this loop.  */
 141   struct loop *copy;
 142
 143   /* Nonzero if the loop is invalid (e.g., contains setjmp.).  */
 144   int invalid;
 145
 146   /* Auxiliary info specific to a pass.  */
 147   void *aux;
 148
 149   /* The following are currently used by loop.c but they are likely to
 150      disappear as loop.c is converted to use the CFG.  */
 151
 152   /* The NOTE_INSN_LOOP_BEG.  */
 153   rtx start;
 154
 155   /* The NOTE_INSN_LOOP_END.  */
 156   rtx end;
 157
 158   /* For a rotated loop that is entered near the bottom,
 159      this is the label at the top.  Otherwise it is zero.  */
 160   rtx top;
 161
 162   /* Place in the loop where control enters.  */
 163   rtx scan_start;
 164
 165   /* The position where to sink insns out of the loop.  */
 166   rtx sink;
 167
 168   /* List of all LABEL_REFs which refer to code labels outside the
 169      loop.  Used by routines that need to know all loop exits, such as
 170      final_biv_value and final_giv_value.
 171
 172      This does not include loop exits due to return instructions.
 173      This is because all bivs and givs are pseudos, and hence must be
 174      dead after a return, so the presence of a return does not affect
 175      any of the optimizations that use this info.  It is simpler to
 176      just not include return instructions on this list.  */
 177   rtx exit_labels;
 178
 179   /* The number of LABEL_REFs on exit_labels for this loop and all
 180      loops nested inside it.  */
 181   int exit_count;
 182
 183   /* The probable number of times the loop is executed at runtime.
 184      This is an INTEGER_CST or an expression containing symbolic
 185      names.  Don't access this field directly:
 186      number_of_iterations_in_loop computes and caches the computed
 187      information in this field.  */
 188   tree nb_iterations;
 189
 190   /* An INTEGER_CST estimation of the number of iterations.  NULL_TREE
 191      if there is no estimation.  */
 192   tree estimated_nb_iterations;
 193
 194   /* Upper bound on number of iterations of a loop.  */
 195   struct nb_iter_bound *bounds;
 196
 197   /* If not NULL, loop has just single exit edge stored here (edges to the
 198      EXIT_BLOCK_PTR do not count.  */
 199   edge single_exit;
 200
 201   /* True when the loop does not carry data dependences, and
 202      consequently the iterations can be executed in any order.  False
 203      when the loop carries data dependences, or when the property is
 204      not decidable.  */
 205   bool parallel_p;
 206 };
 207
 208 /* Flags for state of loop structure.  */
 209 enum
 210 {
 211   LOOPS_HAVE_PREHEADERS = 1,
 212   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 213   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
 214   LOOPS_HAVE_MARKED_SINGLE_EXITS = 8
 215 };
 216
 217 /* Structure to hold CFG information about natural loops within a function.  */
 218 struct loops
 219 {
 220   /* Number of natural loops in the function.  */
 221   unsigned num;
 222
 223   /* Maximum nested loop level in the function.  */
 224   unsigned levels;
 225
 226   /* Array of natural loop descriptors (scanning this array in reverse order
 227      will find the inner loops before their enclosing outer loops).  */
 228   struct loop *array;
 229
 230   /* The above array is unused in new loop infrastructure and is kept only for
 231      purposes of the old loop optimizer.  Instead we store just pointers to
 232      loops here.  */
 233   struct loop **parray;
 234
 235   /* Pointer to root of loop hierarchy tree.  */
 236   struct loop *tree_root;
 237
 238   /* Information derived from the CFG.  */
 239   struct cfg
 240   {
 241     /* The ordering of the basic blocks in a depth first search.  */
 242     int *dfs_order;
 243
 244     /* The reverse completion ordering of the basic blocks found in a
 245        depth first search.  */
 246     int *rc_order;
 247   } cfg;
 248
 249   /* Headers shared by multiple loops that should be merged.  */
 250   sbitmap shared_headers;
 251
 252   /* State of loops.  */
 253   int state;
 254 };
 255
 256 /* The loop tree currently optimized.  */
 257
 258 extern struct loops *current_loops;
 259
 260 /* Flags for loop discovery.  */
 261
 262 #define LOOP_TREE               1       /* Build loop hierarchy tree.  */
 263 #define LOOP_PRE_HEADER         2       /* Analyze loop preheader.  */
 264 #define LOOP_ENTRY_EDGES        4       /* Find entry edges.  */
 265 #define LOOP_EXIT_EDGES         8       /* Find exit edges.  */
 266 #define LOOP_EDGES              (LOOP_ENTRY_EDGES | LOOP_EXIT_EDGES)
 267 #define LOOP_ALL               15       /* All of the above  */
 268
 269 /* Loop recognition.  */
 270 extern int flow_loops_find (struct loops *, int flags);
 271 extern int flow_loops_update (struct loops *, int flags);
 272 extern void flow_loops_free (struct loops *);
 273 extern void flow_loops_dump (const struct loops *, FILE *,
 274                              void (*)(const struct loop *, FILE *, int), int);
 275 extern void flow_loop_dump (const struct loop *, FILE *,
 276                             void (*)(const struct loop *, FILE *, int), int);
 277 extern int flow_loop_scan (struct loop *, int);
 278 extern void flow_loop_free (struct loop *);
 279 void mark_irreducible_loops (struct loops *);
 280 void mark_single_exit_loops (struct loops *);
 281 void update_single_exits_after_duplication (basic_block *, unsigned,
 282                                             struct loop *);
 283 extern void create_loop_notes (void);
 284
 285 /* Loop data structure manipulation/querying.  */
 286 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 287 extern void flow_loop_tree_node_remove (struct loop *);
 288 extern bool flow_loop_outside_edge_p (const struct loop *, edge);
 289 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 290 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
 291 extern struct loop * find_common_loop (struct loop *, struct loop *);
 292 struct loop *superloop_at_depth (struct loop *, unsigned);
 293 extern unsigned tree_num_loop_insns (struct loop *);
 294 extern int num_loop_insns (struct loop *);
 295 extern int average_num_loop_insns (struct loop *);
 296 extern unsigned get_loop_level (const struct loop *);
 297
 298 /* Loops & cfg manipulation.  */
 299 extern basic_block *get_loop_body (const struct loop *);
 300 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 301 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 302 extern edge *get_loop_exit_edges (const struct loop *, unsigned *);
 303 extern unsigned num_loop_branches (const struct loop *);
 304
 305 extern edge loop_preheader_edge (const struct loop *);
 306 extern edge loop_latch_edge (const struct loop *);
 307
 308 extern void add_bb_to_loop (basic_block, struct loop *);
 309 extern void remove_bb_from_loops (basic_block);
 310
 311 extern void cancel_loop (struct loops *, struct loop *);
 312 extern void cancel_loop_tree (struct loops *, struct loop *);
 313
 314 extern basic_block loop_split_edge_with (edge, rtx);
 315 extern int fix_loop_placement (struct loop *);
 316
 317 enum
 318 {
 319   CP_SIMPLE_PREHEADERS = 1
 320 };
 321
 322 extern void create_preheaders (struct loops *, int);
 323 extern void force_single_succ_latches (struct loops *);
 324
 325 extern void verify_loop_structure (struct loops *);
 326
 327 /* Loop analysis.  */
 328 extern bool just_once_each_iteration_p (struct loop *, basic_block);
 329 extern unsigned expected_loop_iterations (const struct loop *);
 330
 331 /* Loop manipulation.  */
 332 extern bool can_duplicate_loop_p (struct loop *loop);
 333
 334 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 335                                            duplicate_loop_to_header_edge.  */
 336
 337 extern struct loop * duplicate_loop (struct loops *, struct loop *,
 338                                      struct loop *);
 339 extern int duplicate_loop_to_header_edge (struct loop *, edge, struct loops *,
 340                                           unsigned, sbitmap, edge, edge *,
 341                                           unsigned *, int);
 342 extern struct loop *loopify (struct loops *, edge, edge,
 343                              basic_block, edge, edge, bool);
 344 extern void unloop (struct loops *, struct loop *);
 345 extern bool remove_path (struct loops *, edge);
 346 extern edge split_loop_bb (basic_block, void *);
 347
 348 /* Induction variable analysis.  */
 349
 350 /* The description of induction variable.  The things are a bit complicated
 351    due to need to handle subregs and extends.  The value of the object described
 352    by it can be obtained as follows (all computations are done in extend_mode):
 353
 354    Value in i-th iteration is
 355      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 356
 357    If first_special is true, the value in the first iteration is
 358      delta + mult * base
 359
 360    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 361      subreg_{mode} (base + i * step)
 362
 363    The get_iv_value function can be used to obtain these expressions.
 364
 365    ??? Add a third mode field that would specify the mode in that inner
 366    computation is done, which would enable it to be different from the
 367    outer one?  */
 368
 369 struct rtx_iv
 370 {
 371   /* Its base and step (mode of base and step is supposed to be extend_mode,
 372      see the description above).  */
 373   rtx base, step;
 374
 375   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 376   enum rtx_code extend;
 377
 378   /* Operations applied in the extended mode.  */
 379   rtx delta, mult;
 380
 381   /* The mode it is extended to.  */
 382   enum machine_mode extend_mode;
 383
 384   /* The mode the variable iterates in.  */
 385   enum machine_mode mode;
 386
 387   /* Whether we have already filled the remaining fields.  */
 388   unsigned analysed : 1;
 389
 390   /* Whether the first iteration needs to be handled specially.  */
 391   unsigned first_special : 1;
 392 };
 393
 394 /* The description of an exit from the loop and of the number of iterations
 395    till we take the exit.  */
 396
 397 struct niter_desc
 398 {
 399   /* The edge out of the loop.  */
 400   edge out_edge;
 401
 402   /* The other edge leading from the condition.  */
 403   edge in_edge;
 404
 405   /* True if we are able to say anything about number of iterations of the
 406      loop.  */
 407   bool simple_p;
 408
 409   /* True if the loop iterates the constant number of times.  */
 410   bool const_iter;
 411
 412   /* Number of iterations if constant.  */
 413   unsigned HOST_WIDEST_INT niter;
 414
 415   /* Upper bound on the number of iterations.  */
 416   unsigned HOST_WIDEST_INT niter_max;
 417
 418   /* Assumptions under that the rest of the information is valid.  */
 419   rtx assumptions;
 420
 421   /* Assumptions under that the loop ends before reaching the latch,
 422      even if value of niter_expr says otherwise.  */
 423   rtx noloop_assumptions;
 424
 425   /* Condition under that the loop is infinite.  */
 426   rtx infinite;
 427
 428   /* Whether the comparison is signed.  */
 429   bool signed_p;
 430
 431   /* The mode in that niter_expr should be computed.  */
 432   enum machine_mode mode;
 433
 434   /* The number of iterations of the loop.  */
 435   rtx niter_expr;
 436 };
 437
 438 extern void iv_analysis_loop_init (struct loop *);
 439 extern rtx iv_get_reaching_def (rtx, rtx);
 440 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 441 extern rtx get_iv_value (struct rtx_iv *, rtx);
 442 extern bool biv_p (rtx, rtx);
 443 extern void find_simple_exit (struct loop *, struct niter_desc *);
 444 extern void iv_number_of_iterations (struct loop *, rtx, rtx,
 445                                      struct niter_desc *);
 446 extern void iv_analysis_done (void);
 447
 448 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 449 extern void free_simple_loop_desc (struct loop *loop);
 450
 451 static inline struct niter_desc *
 452 simple_loop_desc (struct loop *loop)
 453 {
 454   return loop->aux;
 455 }
 456
 457 /* The properties of the target.  */
 458
 459 extern unsigned target_avail_regs;      /* Number of available registers.  */
 460 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 461 extern unsigned target_small_cost;      /* The cost for register when there
 462                                            is a free one.  */
 463 extern unsigned target_pres_cost;       /* The cost for register when there are
 464                                            not too many free ones.  */
 465 extern unsigned target_spill_cost;      /* The cost for register when we need
 466                                            to spill.  */
 467
 468 /* Register pressure estimation for induction variable optimizations & loop
 469    invariant motion.  */
 470 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 471 extern void init_set_costs (void);
 472
 473 /* Loop optimizer initialization.  */
 474 extern struct loops *loop_optimizer_init (FILE *);
 475 extern void loop_optimizer_finalize (struct loops *, FILE *);
 476
 477 /* Optimization passes.  */
 478 extern void unswitch_loops (struct loops *);
 479
 480 enum
 481 {
 482   UAP_PEEL = 1,         /* Enables loop peeling.  */
 483   UAP_UNROLL = 2,       /* Enables peeling of loops if it seems profitable.  */
 484   UAP_UNROLL_ALL = 4    /* Enables peeling of all loops.  */
 485 };
 486
 487 extern void unroll_and_peel_loops (struct loops *, int);
 488 extern void doloop_optimize_loops (struct loops *);
 489 extern void move_loop_invariants (struct loops *);
 490 extern void record_estimate (struct loop *, tree, tree, tree);
 491
 492 /* Old loop optimizer interface.  */
 493
 494 /* Flags passed to loop_optimize.  */
 495 #define LOOP_PREFETCH 1
 496
 497 extern void loop_optimize (rtx, FILE *, int);
 498
 499 #endif /* GCC_CFGLOOP_H */