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   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 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 189                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 190
 191 /* Structure to hold CFG information about natural loops within a function.  */
 192 struct loops
 193 {
 194   /* Number of natural loops in the function.  */
 195   unsigned num;
 196
 197   /* Array of natural loop descriptors (scanning this array in reverse order
 198      will find the inner loops before their enclosing outer loops).  */
 199   struct loop *array;
 200
 201   /* The above array is unused in new loop infrastructure and is kept only for
 202      purposes of the old loop optimizer.  Instead we store just pointers to
 203      loops here.
 204      Note that a loop in this array may actually be NULL, if the loop
 205      has been removed and the entire loops structure has not been
 206      recomputed since that time.  */
 207   struct loop **parray;
 208
 209   /* Pointer to root of loop hierarchy tree.  */
 210   struct loop *tree_root;
 211
 212   /* Information derived from the CFG.  */
 213   struct cfg
 214   {
 215     /* The ordering of the basic blocks in a depth first search.  */
 216     int *dfs_order;
 217
 218     /* The reverse completion ordering of the basic blocks found in a
 219        depth first search.  */
 220     int *rc_order;
 221   } cfg;
 222
 223   /* Headers shared by multiple loops that should be merged.  */
 224   sbitmap shared_headers;
 225
 226   /* State of loops.  */
 227   int state;
 228 };
 229
 230 /* The loop tree currently optimized.  */
 231
 232 extern struct loops *current_loops;
 233
 234 /* Loop recognition.  */
 235 extern int flow_loops_find (struct loops *);
 236 extern void flow_loops_free (struct loops *);
 237 extern void flow_loops_dump (const struct loops *, FILE *,
 238                              void (*)(const struct loop *, FILE *, int), int);
 239 extern void flow_loop_dump (const struct loop *, FILE *,
 240                             void (*)(const struct loop *, FILE *, int), int);
 241 extern void flow_loop_free (struct loop *);
 242 int flow_loop_nodes_find (basic_block, struct loop *);
 243 void fix_loop_structure (struct loops *, bitmap changed_bbs);
 244 void mark_irreducible_loops (struct loops *);
 245 void mark_single_exit_loops (struct loops *);
 246 extern void create_loop_notes (void);
 247
 248 /* Loop data structure manipulation/querying.  */
 249 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 250 extern void flow_loop_tree_node_remove (struct loop *);
 251 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 252 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
 253 extern struct loop * find_common_loop (struct loop *, struct loop *);
 254 struct loop *superloop_at_depth (struct loop *, unsigned);
 255 extern unsigned tree_num_loop_insns (struct loop *);
 256 extern int num_loop_insns (struct loop *);
 257 extern int average_num_loop_insns (struct loop *);
 258 extern unsigned get_loop_level (const struct loop *);
 259 extern bool loop_exit_edge_p (const struct loop *, edge);
 260 extern void mark_loop_exit_edges (struct loops *);
 261
 262 /* Loops & cfg manipulation.  */
 263 extern basic_block *get_loop_body (const struct loop *);
 264 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 265 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 266 extern edge *get_loop_exit_edges (const struct loop *, unsigned *);
 267 extern unsigned num_loop_branches (const struct loop *);
 268
 269 extern edge loop_preheader_edge (const struct loop *);
 270 extern edge loop_latch_edge (const struct loop *);
 271
 272 extern void add_bb_to_loop (basic_block, struct loop *);
 273 extern void remove_bb_from_loops (basic_block);
 274
 275 extern void cancel_loop (struct loops *, struct loop *);
 276 extern void cancel_loop_tree (struct loops *, struct loop *);
 277
 278 extern basic_block loop_split_edge_with (edge, rtx);
 279 extern int fix_loop_placement (struct loop *);
 280
 281 enum
 282 {
 283   CP_SIMPLE_PREHEADERS = 1
 284 };
 285
 286 extern void create_preheaders (struct loops *, int);
 287 extern void force_single_succ_latches (struct loops *);
 288
 289 extern void verify_loop_structure (struct loops *);
 290
 291 /* Loop analysis.  */
 292 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
 293 extern unsigned expected_loop_iterations (const struct loop *);
 294 extern rtx doloop_condition_get (rtx);
 295
 296 /* Loop manipulation.  */
 297 extern bool can_duplicate_loop_p (struct loop *loop);
 298
 299 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 300                                            duplicate_loop_to_header_edge.  */
 301 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 302                                            field of newly create BB.  */
 303 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 304                                            a complete peeling.  */
 305
 306 extern struct loop * duplicate_loop (struct loops *, struct loop *,
 307                                      struct loop *);
 308 extern bool duplicate_loop_to_header_edge (struct loop *, edge, struct loops *,
 309                                            unsigned, sbitmap, edge, edge *,
 310                                            unsigned *, int);
 311 extern struct loop *loopify (struct loops *, edge, edge,
 312                              basic_block, edge, edge, bool);
 313 struct loop * loop_version (struct loops *, struct loop *, void *,
 314                             basic_block *, bool);
 315 extern bool remove_path (struct loops *, edge);
 316
 317 /* Induction variable analysis.  */
 318
 319 /* The description of induction variable.  The things are a bit complicated
 320    due to need to handle subregs and extends.  The value of the object described
 321    by it can be obtained as follows (all computations are done in extend_mode):
 322
 323    Value in i-th iteration is
 324      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 325
 326    If first_special is true, the value in the first iteration is
 327      delta + mult * base
 328
 329    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 330      subreg_{mode} (base + i * step)
 331
 332    The get_iv_value function can be used to obtain these expressions.
 333
 334    ??? Add a third mode field that would specify the mode in that inner
 335    computation is done, which would enable it to be different from the
 336    outer one?  */
 337
 338 struct rtx_iv
 339 {
 340   /* Its base and step (mode of base and step is supposed to be extend_mode,
 341      see the description above).  */
 342   rtx base, step;
 343
 344   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 345   enum rtx_code extend;
 346
 347   /* Operations applied in the extended mode.  */
 348   rtx delta, mult;
 349
 350   /* The mode it is extended to.  */
 351   enum machine_mode extend_mode;
 352
 353   /* The mode the variable iterates in.  */
 354   enum machine_mode mode;
 355
 356   /* Whether the first iteration needs to be handled specially.  */
 357   unsigned first_special : 1;
 358 };
 359
 360 /* The description of an exit from the loop and of the number of iterations
 361    till we take the exit.  */
 362
 363 struct niter_desc
 364 {
 365   /* The edge out of the loop.  */
 366   edge out_edge;
 367
 368   /* The other edge leading from the condition.  */
 369   edge in_edge;
 370
 371   /* True if we are able to say anything about number of iterations of the
 372      loop.  */
 373   bool simple_p;
 374
 375   /* True if the loop iterates the constant number of times.  */
 376   bool const_iter;
 377
 378   /* Number of iterations if constant.  */
 379   unsigned HOST_WIDEST_INT niter;
 380
 381   /* Upper bound on the number of iterations.  */
 382   unsigned HOST_WIDEST_INT niter_max;
 383
 384   /* Assumptions under that the rest of the information is valid.  */
 385   rtx assumptions;
 386
 387   /* Assumptions under that the loop ends before reaching the latch,
 388      even if value of niter_expr says otherwise.  */
 389   rtx noloop_assumptions;
 390
 391   /* Condition under that the loop is infinite.  */
 392   rtx infinite;
 393
 394   /* Whether the comparison is signed.  */
 395   bool signed_p;
 396
 397   /* The mode in that niter_expr should be computed.  */
 398   enum machine_mode mode;
 399
 400   /* The number of iterations of the loop.  */
 401   rtx niter_expr;
 402 };
 403
 404 extern void iv_analysis_loop_init (struct loop *);
 405 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 406 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 407 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 408 extern rtx get_iv_value (struct rtx_iv *, rtx);
 409 extern bool biv_p (rtx, rtx);
 410 extern void find_simple_exit (struct loop *, struct niter_desc *);
 411 extern void iv_analysis_done (void);
 412 extern struct df *iv_current_loop_df (void);
 413
 414 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 415 extern void free_simple_loop_desc (struct loop *loop);
 416
 417 static inline struct niter_desc *
 418 simple_loop_desc (struct loop *loop)
 419 {
 420   return (struct niter_desc *) loop->aux;
 421 }
 422
 423 /* The properties of the target.  */
 424
 425 extern unsigned target_avail_regs;      /* Number of available registers.  */
 426 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 427 extern unsigned target_small_cost;      /* The cost for register when there
 428                                            is a free one.  */
 429 extern unsigned target_pres_cost;       /* The cost for register when there are
 430                                            not too many free ones.  */
 431 extern unsigned target_spill_cost;      /* The cost for register when we need
 432                                            to spill.  */
 433
 434 /* Register pressure estimation for induction variable optimizations & loop
 435    invariant motion.  */
 436 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 437 extern void init_set_costs (void);
 438
 439 /* Loop optimizer initialization.  */
 440 extern struct loops *loop_optimizer_init (unsigned);
 441 extern void loop_optimizer_finalize (struct loops *);
 442
 443 /* Optimization passes.  */
 444 extern void unswitch_loops (struct loops *);
 445
 446 enum
 447 {
 448   UAP_PEEL = 1,         /* Enables loop peeling.  */
 449   UAP_UNROLL = 2,       /* Enables peeling of loops if it seems profitable.  */
 450   UAP_UNROLL_ALL = 4    /* Enables peeling of all loops.  */
 451 };
 452
 453 extern void unroll_and_peel_loops (struct loops *, int);
 454 extern void doloop_optimize_loops (struct loops *);
 455 extern void move_loop_invariants (struct loops *);
 456 extern void record_estimate (struct loop *, tree, tree, tree);
 457
 458 /* Old loop optimizer interface.  */
 459
 460 /* Flags passed to loop_optimize.  */
 461 #define LOOP_PREFETCH 1
 462
 463 #endif /* GCC_CFGLOOP_H */