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 void update_single_exits_after_duplication (basic_block *, unsigned,
 258                                             struct loop *);
 259 extern void create_loop_notes (void);
 260
 261 /* Loop data structure manipulation/querying.  */
 262 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 263 extern void flow_loop_tree_node_remove (struct loop *);
 264 extern bool flow_loop_outside_edge_p (const struct loop *, edge);
 265 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 266 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
 267 extern struct loop * find_common_loop (struct loop *, struct loop *);
 268 struct loop *superloop_at_depth (struct loop *, unsigned);
 269 extern unsigned tree_num_loop_insns (struct loop *);
 270 extern int num_loop_insns (struct loop *);
 271 extern int average_num_loop_insns (struct loop *);
 272 extern unsigned get_loop_level (const struct loop *);
 273
 274 /* Loops & cfg manipulation.  */
 275 extern basic_block *get_loop_body (const struct loop *);
 276 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 277 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 278 extern edge *get_loop_exit_edges (const struct loop *, unsigned *);
 279 extern unsigned num_loop_branches (const struct loop *);
 280
 281 extern edge loop_preheader_edge (const struct loop *);
 282 extern edge loop_latch_edge (const struct loop *);
 283
 284 extern void add_bb_to_loop (basic_block, struct loop *);
 285 extern void remove_bb_from_loops (basic_block);
 286
 287 extern void cancel_loop (struct loops *, struct loop *);
 288 extern void cancel_loop_tree (struct loops *, struct loop *);
 289
 290 extern basic_block loop_split_edge_with (edge, rtx);
 291 extern int fix_loop_placement (struct loop *);
 292
 293 enum
 294 {
 295   CP_SIMPLE_PREHEADERS = 1
 296 };
 297
 298 extern void create_preheaders (struct loops *, int);
 299 extern void force_single_succ_latches (struct loops *);
 300
 301 extern void verify_loop_structure (struct loops *);
 302
 303 /* Loop analysis.  */
 304 extern bool just_once_each_iteration_p (struct loop *, basic_block);
 305 extern unsigned expected_loop_iterations (const struct loop *);
 306
 307 /* Loop manipulation.  */
 308 extern bool can_duplicate_loop_p (struct loop *loop);
 309
 310 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 311                                            duplicate_loop_to_header_edge.  */
 312
 313 extern struct loop * duplicate_loop (struct loops *, struct loop *,
 314                                      struct loop *);
 315 extern int duplicate_loop_to_header_edge (struct loop *, edge, struct loops *,
 316                                           unsigned, sbitmap, edge, edge *,
 317                                           unsigned *, int);
 318 extern struct loop *loopify (struct loops *, edge, edge, basic_block, bool);
 319 extern void unloop (struct loops *, struct loop *);
 320 extern bool remove_path (struct loops *, edge);
 321 extern edge split_loop_bb (basic_block, void *);
 322
 323 /* Induction variable analysis.  */
 324
 325 /* The description of induction variable.  The things are a bit complicated
 326    due to need to handle subregs and extends.  The value of the object described
 327    by it can be obtained as follows (all computations are done in extend_mode):
 328
 329    Value in i-th iteration is
 330      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 331
 332    If first_special is true, the value in the first iteration is
 333      delta + mult * base
 334
 335    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 336      subreg_{mode} (base + i * step)
 337
 338    The get_iv_value function can be used to obtain these expressions.
 339
 340    ??? Add a third mode field that would specify the mode in that inner
 341    computation is done, which would enable it to be different from the
 342    outer one?  */
 343
 344 struct rtx_iv
 345 {
 346   /* Its base and step (mode of base and step is supposed to be extend_mode,
 347      see the description above).  */
 348   rtx base, step;
 349
 350   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 351   enum rtx_code extend;
 352
 353   /* Operations applied in the extended mode.  */
 354   rtx delta, mult;
 355
 356   /* The mode it is extended to.  */
 357   enum machine_mode extend_mode;
 358
 359   /* The mode the variable iterates in.  */
 360   enum machine_mode mode;
 361
 362   /* Whether we have already filled the remaining fields.  */
 363   unsigned analysed : 1;
 364
 365   /* Whether the first iteration needs to be handled specially.  */
 366   unsigned first_special : 1;
 367 };
 368
 369 /* The description of an exit from the loop and of the number of iterations
 370    till we take the exit.  */
 371
 372 struct niter_desc
 373 {
 374   /* The edge out of the loop.  */
 375   edge out_edge;
 376
 377   /* The other edge leading from the condition.  */
 378   edge in_edge;
 379
 380   /* True if we are able to say anything about number of iterations of the
 381      loop.  */
 382   bool simple_p;
 383
 384   /* True if the loop iterates the constant number of times.  */
 385   bool const_iter;
 386
 387   /* Number of iterations if constant.  */
 388   unsigned HOST_WIDEST_INT niter;
 389
 390   /* Upper bound on the number of iterations.  */
 391   unsigned HOST_WIDEST_INT niter_max;
 392
 393   /* Assumptions under that the rest of the information is valid.  */
 394   rtx assumptions;
 395
 396   /* Assumptions under that the loop ends before reaching the latch,
 397      even if value of niter_expr says otherwise.  */
 398   rtx noloop_assumptions;
 399
 400   /* Condition under that the loop is infinite.  */
 401   rtx infinite;
 402
 403   /* Whether the comparison is signed.  */
 404   bool signed_p;
 405
 406   /* The mode in that niter_expr should be computed.  */
 407   enum machine_mode mode;
 408
 409   /* The number of iterations of the loop.  */
 410   rtx niter_expr;
 411 };
 412
 413 extern void iv_analysis_loop_init (struct loop *);
 414 extern rtx iv_get_reaching_def (rtx, rtx);
 415 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 416 extern rtx get_iv_value (struct rtx_iv *, rtx);
 417 extern bool biv_p (rtx, rtx);
 418 extern void find_simple_exit (struct loop *, struct niter_desc *);
 419 extern void iv_number_of_iterations (struct loop *, rtx, rtx,
 420                                      struct niter_desc *);
 421 extern void iv_analysis_done (void);
 422
 423 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 424 extern void free_simple_loop_desc (struct loop *loop);
 425
 426 static inline struct niter_desc *
 427 simple_loop_desc (struct loop *loop)
 428 {
 429   return loop->aux;
 430 }
 431
 432 /* The properties of the target.  */
 433
 434 extern unsigned target_avail_regs;      /* Number of available registers.  */
 435 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 436 extern unsigned target_small_cost;      /* The cost for register when there
 437                                            is a free one.  */
 438 extern unsigned target_pres_cost;       /* The cost for register when there are
 439                                            not too many free ones.  */
 440 extern unsigned target_spill_cost;      /* The cost for register when we need
 441                                            to spill.  */
 442
 443 /* Register pressure estimation for induction variable optimizations & loop
 444    invariant motion.  */
 445 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 446 extern void init_set_costs (void);
 447
 448 /* Loop optimizer initialization.  */
 449 extern struct loops *loop_optimizer_init (FILE *);
 450 extern void loop_optimizer_finalize (struct loops *, FILE *);
 451
 452 /* Optimization passes.  */
 453 extern void unswitch_loops (struct loops *);
 454
 455 enum
 456 {
 457   UAP_PEEL = 1,         /* Enables loop peeling.  */
 458   UAP_UNROLL = 2,       /* Enables peeling of loops if it seems profitable.  */
 459   UAP_UNROLL_ALL = 4    /* Enables peeling of all loops.  */
 460 };
 461
 462 extern void unroll_and_peel_loops (struct loops *, int);
 463 extern void doloop_optimize_loops (struct loops *);
 464 extern void move_loop_invariants (struct loops *);
 465
 466 /* Old loop optimizer interface.  */
 467
 468 /* Flags passed to loop_optimize.  */
 469 #define LOOP_PREFETCH 1
 470
 471 extern void loop_optimize (rtx, FILE *, int);
 472
 473 #endif /* GCC_CFGLOOP_H */