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 /* Structure to hold information for each natural loop.  */
  47 struct loop
  48 {
  49   /* Index into loops array.  */
  50   int num;
  51
  52   /* Basic block of loop header.  */
  53   basic_block header;
  54
  55   /* Basic block of loop latch.  */
  56   basic_block latch;
  57
  58   /* Basic block of loop preheader or NULL if it does not exist.  */
  59   basic_block pre_header;
  60
  61   /* For loop unrolling/peeling decision.  */
  62   struct lpt_decision lpt_decision;
  63
  64   /* Number of loop insns.  */
  65   unsigned ninsns;
  66
  67   /* Average number of executed insns per iteration.  */
  68   unsigned av_ninsns;
  69
  70   /* Array of edges along the preheader extended basic block trace.
  71      The source of the first edge is the root node of preheader
  72      extended basic block, if it exists.  */
  73   edge *pre_header_edges;
  74
  75   /* Number of edges along the pre_header extended basic block trace.  */
  76   int num_pre_header_edges;
  77
  78   /* The first block in the loop.  This is not necessarily the same as
  79      the loop header.  */
  80   basic_block first;
  81
  82   /* The last block in the loop.  This is not necessarily the same as
  83      the loop latch.  */
  84   basic_block last;
  85
  86   /* Bitmap of blocks contained within the loop.  */
  87   sbitmap nodes;
  88
  89   /* Number of blocks contained within the loop.  */
  90   unsigned num_nodes;
  91
  92   /* Array of edges that enter the loop.  */
  93   edge *entry_edges;
  94
  95   /* Number of edges that enter the loop.  */
  96   int num_entries;
  97
  98   /* Array of edges that exit the loop.  */
  99   edge *exit_edges;
 100
 101   /* Number of edges that exit the loop.  */
 102   int num_exits;
 103
 104   /* Bitmap of blocks that dominate all exits of the loop.  */
 105   sbitmap exits_doms;
 106
 107   /* The loop nesting depth.  */
 108   int depth;
 109
 110   /* Superloops of the loop.  */
 111   struct loop **pred;
 112
 113   /* The height of the loop (enclosed loop levels) within the loop
 114      hierarchy tree.  */
 115   int level;
 116
 117   /* The outer (parent) loop or NULL if outermost loop.  */
 118   struct loop *outer;
 119
 120   /* The first inner (child) loop or NULL if innermost loop.  */
 121   struct loop *inner;
 122
 123   /* Link to the next (sibling) loop.  */
 124   struct loop *next;
 125
 126   /* Loop that is copy of this loop.  */
 127   struct loop *copy;
 128
 129   /* Nonzero if the loop is invalid (e.g., contains setjmp.).  */
 130   int invalid;
 131
 132   /* Auxiliary info specific to a pass.  */
 133   void *aux;
 134
 135   /* The following are currently used by loop.c but they are likely to
 136      disappear as loop.c is converted to use the CFG.  */
 137
 138   /* The NOTE_INSN_LOOP_BEG.  */
 139   rtx start;
 140
 141   /* The NOTE_INSN_LOOP_END.  */
 142   rtx end;
 143
 144   /* For a rotated loop that is entered near the bottom,
 145      this is the label at the top.  Otherwise it is zero.  */
 146   rtx top;
 147
 148   /* Place in the loop where control enters.  */
 149   rtx scan_start;
 150
 151   /* The position where to sink insns out of the loop.  */
 152   rtx sink;
 153
 154   /* List of all LABEL_REFs which refer to code labels outside the
 155      loop.  Used by routines that need to know all loop exits, such as
 156      final_biv_value and final_giv_value.
 157
 158      This does not include loop exits due to return instructions.
 159      This is because all bivs and givs are pseudos, and hence must be
 160      dead after a return, so the presence of a return does not affect
 161      any of the optimizations that use this info.  It is simpler to
 162      just not include return instructions on this list.  */
 163   rtx exit_labels;
 164
 165   /* The number of LABEL_REFs on exit_labels for this loop and all
 166      loops nested inside it.  */
 167   int exit_count;
 168
 169   /* The probable number of times the loop is executed at runtime.
 170      This is an INTEGER_CST or an expression containing symbolic
 171      names.  Don't access this field directly:
 172      number_of_iterations_in_loop computes and caches the computed
 173      information in this field.  */
 174   tree nb_iterations;
 175
 176   /* Upper bound on number of iterations of a loop.  */
 177   struct nb_iter_bound *bounds;
 178
 179   /* If not NULL, loop has just single exit edge stored here (edges to the
 180      EXIT_BLOCK_PTR do not count.  */
 181   edge single_exit;
 182 };
 183
 184 /* Flags for state of loop structure.  */
 185 enum
 186 {
 187   LOOPS_HAVE_PREHEADERS = 1,
 188   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 189   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
 190   LOOPS_HAVE_MARKED_SINGLE_EXITS = 8
 191 };
 192
 193 /* Structure to hold CFG information about natural loops within a function.  */
 194 struct loops
 195 {
 196   /* Number of natural loops in the function.  */
 197   unsigned num;
 198
 199   /* Maximum nested loop level in the function.  */
 200   unsigned levels;
 201
 202   /* Array of natural loop descriptors (scanning this array in reverse order
 203      will find the inner loops before their enclosing outer loops).  */
 204   struct loop *array;
 205
 206   /* The above array is unused in new loop infrastructure and is kept only for
 207      purposes of the old loop optimizer.  Instead we store just pointers to
 208      loops here.  */
 209   struct loop **parray;
 210
 211   /* Pointer to root of loop hierarchy tree.  */
 212   struct loop *tree_root;
 213
 214   /* Information derived from the CFG.  */
 215   struct cfg
 216   {
 217     /* The ordering of the basic blocks in a depth first search.  */
 218     int *dfs_order;
 219
 220     /* The reverse completion ordering of the basic blocks found in a
 221        depth first search.  */
 222     int *rc_order;
 223   } cfg;
 224
 225   /* Headers shared by multiple loops that should be merged.  */
 226   sbitmap shared_headers;
 227
 228   /* State of loops.  */
 229   int state;
 230 };
 231
 232 /* The loop tree currently optimized.  */
 233
 234 extern struct loops *current_loops;
 235
 236 /* Flags for loop discovery.  */
 237
 238 #define LOOP_TREE               1       /* Build loop hierarchy tree.  */
 239 #define LOOP_PRE_HEADER         2       /* Analyze loop preheader.  */
 240 #define LOOP_ENTRY_EDGES        4       /* Find entry edges.  */
 241 #define LOOP_EXIT_EDGES         8       /* Find exit edges.  */
 242 #define LOOP_EDGES              (LOOP_ENTRY_EDGES | LOOP_EXIT_EDGES)
 243 #define LOOP_ALL               15       /* All of the above  */
 244
 245 /* Loop recognition.  */
 246 extern int flow_loops_find (struct loops *, int flags);
 247 extern int flow_loops_update (struct loops *, int flags);
 248 extern void flow_loops_free (struct loops *);
 249 extern void flow_loops_dump (const struct loops *, FILE *,
 250                              void (*)(const struct loop *, FILE *, int), int);
 251 extern void flow_loop_dump (const struct loop *, FILE *,
 252                             void (*)(const struct loop *, FILE *, int), int);
 253 extern int flow_loop_scan (struct loop *, int);
 254 extern void flow_loop_free (struct loop *);
 255 void mark_irreducible_loops (struct loops *);
 256 void mark_single_exit_loops (struct loops *);
 257 extern void create_loop_notes (void);
 258
 259 /* Loop data structure manipulation/querying.  */
 260 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 261 extern void flow_loop_tree_node_remove (struct loop *);
 262 extern bool flow_loop_outside_edge_p (const struct loop *, edge);
 263 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 264 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
 265 extern struct loop * find_common_loop (struct loop *, struct loop *);
 266 struct loop *superloop_at_depth (struct loop *, unsigned);
 267 extern unsigned tree_num_loop_insns (struct loop *);
 268 extern int num_loop_insns (struct loop *);
 269 extern int average_num_loop_insns (struct loop *);
 270 extern unsigned get_loop_level (const struct loop *);
 271
 272 /* Loops & cfg manipulation.  */
 273 extern basic_block *get_loop_body (const struct loop *);
 274 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 275 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 276 extern edge *get_loop_exit_edges (const struct loop *, unsigned *);
 277 extern unsigned num_loop_branches (const struct loop *);
 278
 279 extern edge loop_preheader_edge (const struct loop *);
 280 extern edge loop_latch_edge (const struct loop *);
 281
 282 extern void add_bb_to_loop (basic_block, struct loop *);
 283 extern void remove_bb_from_loops (basic_block);
 284
 285 extern void cancel_loop (struct loops *, struct loop *);
 286 extern void cancel_loop_tree (struct loops *, struct loop *);
 287
 288 extern basic_block loop_split_edge_with (edge, rtx);
 289 extern int fix_loop_placement (struct loop *);
 290
 291 enum
 292 {
 293   CP_SIMPLE_PREHEADERS = 1
 294 };
 295
 296 extern void create_preheaders (struct loops *, int);
 297 extern void force_single_succ_latches (struct loops *);
 298
 299 extern void verify_loop_structure (struct loops *);
 300
 301 /* Loop analysis.  */
 302 extern bool just_once_each_iteration_p (struct loop *, basic_block);
 303 extern unsigned expected_loop_iterations (const struct loop *);
 304
 305 /* Loop manipulation.  */
 306 extern bool can_duplicate_loop_p (struct loop *loop);
 307
 308 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 309                                            duplicate_loop_to_header_edge.  */
 310
 311 extern struct loop * duplicate_loop (struct loops *, struct loop *,
 312                                      struct loop *);
 313 extern int duplicate_loop_to_header_edge (struct loop *, edge, struct loops *,
 314                                           unsigned, sbitmap, edge, edge *,
 315                                           unsigned *, int);
 316 extern struct loop *loopify (struct loops *, edge, edge, basic_block);
 317 extern void unloop (struct loops *, struct loop *);
 318 extern bool remove_path (struct loops *, edge);
 319 extern edge split_loop_bb (basic_block, rtx);
 320
 321 /* Induction variable analysis.  */
 322
 323 /* The description of induction variable.  The things are a bit complicated
 324    due to need to handle subregs and extends.  The value of the object described
 325    by it can be obtained as follows (all computations are done in extend_mode):
 326
 327    Value in i-th iteration is
 328      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 329
 330    If first_special is true, the value in the first iteration is
 331      delta + mult * base
 332
 333    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 334      subreg_{mode} (base + i * step)
 335
 336    The get_iv_value function can be used to obtain these expressions.
 337
 338    ??? Add a third mode field that would specify the mode in that inner
 339    computation is done, which would enable it to be different from the
 340    outer one?  */
 341
 342 struct rtx_iv
 343 {
 344   /* Its base and step (mode of base and step is supposed to be extend_mode,
 345      see the description above).  */
 346   rtx base, step;
 347
 348   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 349   enum rtx_code extend;
 350
 351   /* Operations applied in the extended mode.  */
 352   rtx delta, mult;
 353
 354   /* The mode it is extended to.  */
 355   enum machine_mode extend_mode;
 356
 357   /* The mode the variable iterates in.  */
 358   enum machine_mode mode;
 359
 360   /* Whether we have already filled the remaining fields.  */
 361   unsigned analysed : 1;
 362
 363   /* Whether the first iteration needs to be handled specially.  */
 364   unsigned first_special : 1;
 365 };
 366
 367 /* The description of an exit from the loop and of the number of iterations
 368    till we take the exit.  */
 369
 370 struct niter_desc
 371 {
 372   /* The edge out of the loop.  */
 373   edge out_edge;
 374
 375   /* The other edge leading from the condition.  */
 376   edge in_edge;
 377
 378   /* True if we are able to say anything about number of iterations of the
 379      loop.  */
 380   bool simple_p;
 381
 382   /* True if the loop iterates the constant number of times.  */
 383   bool const_iter;
 384
 385   /* Number of iterations if constant.  */
 386   unsigned HOST_WIDEST_INT niter;
 387
 388   /* Upper bound on the number of iterations.  */
 389   unsigned HOST_WIDEST_INT niter_max;
 390
 391   /* Assumptions under that the rest of the information is valid.  */
 392   rtx assumptions;
 393
 394   /* Assumptions under that the loop ends before reaching the latch,
 395      even if value of niter_expr says otherwise.  */
 396   rtx noloop_assumptions;
 397
 398   /* Condition under that the loop is infinite.  */
 399   rtx infinite;
 400
 401   /* Whether the comparison is signed.  */
 402   bool signed_p;
 403
 404   /* The mode in that niter_expr should be computed.  */
 405   enum machine_mode mode;
 406
 407   /* The number of iterations of the loop.  */
 408   rtx niter_expr;
 409 };
 410
 411 extern void iv_analysis_loop_init (struct loop *);
 412 extern rtx iv_get_reaching_def (rtx, rtx);
 413 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 414 extern rtx get_iv_value (struct rtx_iv *, rtx);
 415 extern bool biv_p (rtx, rtx);
 416 extern void find_simple_exit (struct loop *, struct niter_desc *);
 417 extern void iv_number_of_iterations (struct loop *, rtx, rtx,
 418                                      struct niter_desc *);
 419 extern void iv_analysis_done (void);
 420
 421 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 422 extern void free_simple_loop_desc (struct loop *loop);
 423
 424 static inline struct niter_desc *
 425 simple_loop_desc (struct loop *loop)
 426 {
 427   return loop->aux;
 428 }
 429
 430 /* The properties of the target.  */
 431
 432 extern unsigned target_avail_regs;      /* Number of available registers.  */
 433 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 434 extern unsigned target_small_cost;      /* The cost for register when there
 435                                            is a free one.  */
 436 extern unsigned target_pres_cost;       /* The cost for register when there are
 437                                            not too many free ones.  */
 438 extern unsigned target_spill_cost;      /* The cost for register when we need
 439                                            to spill.  */
 440
 441 /* Register pressure estimation for induction variable optimizations & loop
 442    invariant motion.  */
 443 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 444 extern void init_set_costs (void);
 445
 446 /* Loop optimizer initialization.  */
 447 extern struct loops *loop_optimizer_init (FILE *);
 448 extern void loop_optimizer_finalize (struct loops *, FILE *);
 449
 450 /* Optimization passes.  */
 451 extern void unswitch_loops (struct loops *);
 452
 453 enum
 454 {
 455   UAP_PEEL = 1,         /* Enables loop peeling.  */
 456   UAP_UNROLL = 2,       /* Enables peeling of loops if it seems profitable.  */
 457   UAP_UNROLL_ALL = 4    /* Enables peeling of all loops.  */
 458 };
 459
 460 extern void unroll_and_peel_loops (struct loops *, int);
 461 extern void doloop_optimize_loops (struct loops *);
 462 extern void move_loop_invariants (struct loops *);
 463
 464 /* Old loop optimizer interface.  */
 465
 466 /* Flags passed to loop_optimize.  */
 467 #define LOOP_PREFETCH 1
 468
 469 extern void loop_optimize (rtx, FILE *, int);
 470
 471 #endif /* GCC_CFGLOOP_H */