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