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   /* Nonzero if the loop has a NOTE_INSN_LOOP_VTOP.  */
 139   rtx vtop;
 140
 141   /* Nonzero if the loop has a NOTE_INSN_LOOP_CONT.
 142      A continue statement will generate a branch to NEXT_INSN (cont).  */
 143   rtx cont;
 144
 145   /* The dominator of cont.  */
 146   rtx cont_dominator;
 147
 148   /* The NOTE_INSN_LOOP_BEG.  */
 149   rtx start;
 150
 151   /* The NOTE_INSN_LOOP_END.  */
 152   rtx end;
 153
 154   /* For a rotated loop that is entered near the bottom,
 155      this is the label at the top.  Otherwise it is zero.  */
 156   rtx top;
 157
 158   /* Place in the loop where control enters.  */
 159   rtx scan_start;
 160
 161   /* The position where to sink insns out of the loop.  */
 162   rtx sink;
 163
 164   /* List of all LABEL_REFs which refer to code labels outside the
 165      loop.  Used by routines that need to know all loop exits, such as
 166      final_biv_value and final_giv_value.
 167
 168      This does not include loop exits due to return instructions.
 169      This is because all bivs and givs are pseudos, and hence must be
 170      dead after a return, so the presence of a return does not affect
 171      any of the optimizations that use this info.  It is simpler to
 172      just not include return instructions on this list.  */
 173   rtx exit_labels;
 174
 175   /* The number of LABEL_REFs on exit_labels for this loop and all
 176      loops nested inside it.  */
 177   int exit_count;
 178
 179   /* The probable number of times the loop is executed at runtime.
 180      This is an INTEGER_CST or an expression containing symbolic
 181      names.  Don't access this field directly:
 182      number_of_iterations_in_loop computes and caches the computed
 183      information in this field.  */
 184   tree nb_iterations;
 185
 186   /* Upper bound on number of iterations of a loop.  */
 187   struct nb_iter_bound *bounds;
 188 };
 189
 190 /* Flags for state of loop structure.  */
 191 enum
 192 {
 193   LOOPS_HAVE_PREHEADERS = 1,
 194   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 195   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4
 196 };
 197
 198 /* Structure to hold CFG information about natural loops within a function.  */
 199 struct loops
 200 {
 201   /* Number of natural loops in the function.  */
 202   unsigned num;
 203
 204   /* Maximum nested loop level in the function.  */
 205   unsigned levels;
 206
 207   /* Array of natural loop descriptors (scanning this array in reverse order
 208      will find the inner loops before their enclosing outer loops).  */
 209   struct loop *array;
 210
 211   /* The above array is unused in new loop infrastructure and is kept only for
 212      purposes of the old loop optimizer.  Instead we store just pointers to
 213      loops here.  */
 214   struct loop **parray;
 215
 216   /* Pointer to root of loop hierarchy tree.  */
 217   struct loop *tree_root;
 218
 219   /* Information derived from the CFG.  */
 220   struct cfg
 221   {
 222     /* The ordering of the basic blocks in a depth first search.  */
 223     int *dfs_order;
 224
 225     /* The reverse completion ordering of the basic blocks found in a
 226        depth first search.  */
 227     int *rc_order;
 228   } cfg;
 229
 230   /* Headers shared by multiple loops that should be merged.  */
 231   sbitmap shared_headers;
 232
 233   /* State of loops.  */
 234   int state;
 235 };
 236
 237 /* The loop tree currently optimized.  */
 238
 239 extern struct loops *current_loops;
 240
 241 /* Flags for loop discovery.  */
 242
 243 #define LOOP_TREE               1       /* Build loop hierarchy tree.  */
 244 #define LOOP_PRE_HEADER         2       /* Analyze loop preheader.  */
 245 #define LOOP_ENTRY_EDGES        4       /* Find entry edges.  */
 246 #define LOOP_EXIT_EDGES         8       /* Find exit edges.  */
 247 #define LOOP_EDGES              (LOOP_ENTRY_EDGES | LOOP_EXIT_EDGES)
 248 #define LOOP_ALL               15       /* All of the above  */
 249
 250 /* Loop recognition.  */
 251 extern int flow_loops_find (struct loops *, int flags);
 252 extern int flow_loops_update (struct loops *, int flags);
 253 extern void flow_loops_free (struct loops *);
 254 extern void flow_loops_dump (const struct loops *, FILE *,
 255                              void (*)(const struct loop *, FILE *, int), int);
 256 extern void flow_loop_dump (const struct loop *, FILE *,
 257                             void (*)(const struct loop *, FILE *, int), int);
 258 extern int flow_loop_scan (struct loop *, int);
 259 extern void flow_loop_free (struct loop *);
 260 void mark_irreducible_loops (struct loops *);
 261 extern void create_loop_notes (void);
 262
 263 /* Loop data structure manipulation/querying.  */
 264 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 265 extern void flow_loop_tree_node_remove (struct loop *);
 266 extern bool flow_loop_outside_edge_p (const struct loop *, edge);
 267 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 268 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
 269 extern struct loop * find_common_loop (struct loop *, struct loop *);
 270 struct loop *superloop_at_depth (struct loop *, unsigned);
 271 extern int num_loop_insns (struct loop *);
 272 extern int average_num_loop_insns (struct loop *);
 273 extern unsigned get_loop_level (const struct loop *);
 274
 275 /* Loops & cfg manipulation.  */
 276 extern basic_block *get_loop_body (const struct loop *);
 277 extern basic_block *get_loop_body_in_dom_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 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 = NIL, 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 NIL).  */
 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 void find_simple_exit (struct loop *, struct niter_desc *);
 416 extern void iv_number_of_iterations (struct loop *, rtx, rtx,
 417                                      struct niter_desc *);
 418 extern void iv_analysis_done (void);
 419
 420 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 421 extern void free_simple_loop_desc (struct loop *loop);
 422
 423 static inline struct niter_desc *
 424 simple_loop_desc (struct loop *loop)
 425 {
 426   return loop->aux;
 427 }
 428
 429 /* Register pressure estimation for induction variable optimizations & loop
 430    invariant motion.  */
 431 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 432 extern void init_set_costs (void);
 433
 434 /* Loop optimizer initialization.  */
 435 extern struct loops *loop_optimizer_init (FILE *);
 436 extern void loop_optimizer_finalize (struct loops *, FILE *);
 437
 438 /* Optimization passes.  */
 439 extern void unswitch_loops (struct loops *);
 440
 441 enum
 442 {
 443   UAP_PEEL = 1,         /* Enables loop peeling.  */
 444   UAP_UNROLL = 2,       /* Enables peeling of loops if it seems profitable.  */
 445   UAP_UNROLL_ALL = 4    /* Enables peeling of all loops.  */
 446 };
 447
 448 extern void unroll_and_peel_loops (struct loops *, int);
 449 extern void doloop_optimize_loops (struct loops *);
 450 extern void move_loop_invariants (struct loops *);
 451
 452 #endif /* GCC_CFGLOOP_H */