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   /* Number of blocks contained within the loop.  */
  82   unsigned num_nodes;
  83
  84   /* The loop nesting depth.  */
  85   int depth;
  86
  87   /* Superloops of the loop.  */
  88   struct loop **pred;
  89
  90   /* The height of the loop (enclosed loop levels) within the loop
  91      hierarchy tree.  */
  92   int level;
  93
  94   /* The outer (parent) loop or NULL if outermost loop.  */
  95   struct loop *outer;
  96
  97   /* The first inner (child) loop or NULL if innermost loop.  */
  98   struct loop *inner;
  99
 100   /* Link to the next (sibling) loop.  */
 101   struct loop *next;
 102
 103   /* Loop that is copy of this loop.  */
 104   struct loop *copy;
 105
 106   /* Auxiliary info specific to a pass.  */
 107   void *aux;
 108
 109   /* The probable number of times the loop is executed at runtime.
 110      This is an INTEGER_CST or an expression containing symbolic
 111      names.  Don't access this field directly:
 112      number_of_iterations_in_loop computes and caches the computed
 113      information in this field.  */
 114   tree nb_iterations;
 115
 116   /* An INTEGER_CST estimation of the number of iterations.  NULL_TREE
 117      if there is no estimation.  */
 118   tree estimated_nb_iterations;
 119
 120   /* Upper bound on number of iterations of a loop.  */
 121   struct nb_iter_bound *bounds;
 122
 123   /* If not NULL, loop has just single exit edge stored here (edges to the
 124      EXIT_BLOCK_PTR do not count.  */
 125   edge single_exit;
 126
 127   /* True when the loop does not carry data dependences, and
 128      consequently the iterations can be executed in any order.  False
 129      when the loop carries data dependences, or when the property is
 130      not decidable.  */
 131   bool parallel_p;
 132 };
 133
 134 /* Flags for state of loop structure.  */
 135 enum
 136 {
 137   LOOPS_HAVE_PREHEADERS = 1,
 138   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 139   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
 140   LOOPS_HAVE_MARKED_SINGLE_EXITS = 8
 141 };
 142
 143 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 144                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 145
 146 /* Structure to hold CFG information about natural loops within a function.  */
 147 struct loops
 148 {
 149   /* Number of natural loops in the function.  */
 150   unsigned num;
 151
 152   /* Array of natural loop descriptors (scanning this array in reverse order
 153      will find the inner loops before their enclosing outer loops).  */
 154   struct loop *array;
 155
 156   /* The above array is unused in new loop infrastructure and is kept only for
 157      purposes of the old loop optimizer.  Instead we store just pointers to
 158      loops here.
 159      Note that a loop in this array may actually be NULL, if the loop
 160      has been removed and the entire loops structure has not been
 161      recomputed since that time.  */
 162   struct loop **parray;
 163
 164   /* Pointer to root of loop hierarchy tree.  */
 165   struct loop *tree_root;
 166
 167   /* Information derived from the CFG.  */
 168   struct cfg
 169   {
 170     /* The ordering of the basic blocks in a depth first search.  */
 171     int *dfs_order;
 172
 173     /* The reverse completion ordering of the basic blocks found in a
 174        depth first search.  */
 175     int *rc_order;
 176   } cfg;
 177
 178   /* Headers shared by multiple loops that should be merged.  */
 179   sbitmap shared_headers;
 180
 181   /* State of loops.  */
 182   int state;
 183 };
 184
 185 /* The loop tree currently optimized.  */
 186
 187 extern struct loops *current_loops;
 188
 189 /* Loop recognition.  */
 190 extern int flow_loops_find (struct loops *);
 191 extern void flow_loops_free (struct loops *);
 192 extern void flow_loops_dump (const struct loops *, FILE *,
 193                              void (*)(const struct loop *, FILE *, int), int);
 194 extern void flow_loop_dump (const struct loop *, FILE *,
 195                             void (*)(const struct loop *, FILE *, int), int);
 196 extern void flow_loop_free (struct loop *);
 197 int flow_loop_nodes_find (basic_block, struct loop *);
 198 void fix_loop_structure (struct loops *, bitmap changed_bbs);
 199 void mark_irreducible_loops (struct loops *);
 200 void mark_single_exit_loops (struct loops *);
 201 extern void create_loop_notes (void);
 202
 203 /* Loop data structure manipulation/querying.  */
 204 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 205 extern void flow_loop_tree_node_remove (struct loop *);
 206 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 207 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
 208 extern struct loop * find_common_loop (struct loop *, struct loop *);
 209 struct loop *superloop_at_depth (struct loop *, unsigned);
 210 extern unsigned tree_num_loop_insns (struct loop *);
 211 extern int num_loop_insns (struct loop *);
 212 extern int average_num_loop_insns (struct loop *);
 213 extern unsigned get_loop_level (const struct loop *);
 214 extern bool loop_exit_edge_p (const struct loop *, edge);
 215 extern void mark_loop_exit_edges (struct loops *);
 216
 217 /* Loops & cfg manipulation.  */
 218 extern basic_block *get_loop_body (const struct loop *);
 219 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 220 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 221 extern edge *get_loop_exit_edges (const struct loop *, unsigned *);
 222 extern unsigned num_loop_branches (const struct loop *);
 223
 224 extern edge loop_preheader_edge (const struct loop *);
 225 extern edge loop_latch_edge (const struct loop *);
 226
 227 extern void add_bb_to_loop (basic_block, struct loop *);
 228 extern void remove_bb_from_loops (basic_block);
 229
 230 extern void cancel_loop_tree (struct loops *, struct loop *);
 231
 232 extern basic_block loop_split_edge_with (edge, rtx);
 233 extern int fix_loop_placement (struct loop *);
 234
 235 enum
 236 {
 237   CP_SIMPLE_PREHEADERS = 1
 238 };
 239
 240 extern void create_preheaders (struct loops *, int);
 241 extern void force_single_succ_latches (struct loops *);
 242
 243 extern void verify_loop_structure (struct loops *);
 244
 245 /* Loop analysis.  */
 246 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
 247 extern unsigned expected_loop_iterations (const struct loop *);
 248 extern rtx doloop_condition_get (rtx);
 249
 250 /* Loop manipulation.  */
 251 extern bool can_duplicate_loop_p (struct loop *loop);
 252
 253 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 254                                            duplicate_loop_to_header_edge.  */
 255 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 256                                            field of newly create BB.  */
 257 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 258                                            a complete peeling.  */
 259
 260 extern struct loop * duplicate_loop (struct loops *, struct loop *,
 261                                      struct loop *);
 262 extern bool duplicate_loop_to_header_edge (struct loop *, edge, struct loops *,
 263                                            unsigned, sbitmap, edge, edge *,
 264                                            unsigned *, int);
 265 extern struct loop *loopify (struct loops *, edge, edge,
 266                              basic_block, edge, edge, bool);
 267 struct loop * loop_version (struct loops *, struct loop *, void *,
 268                             basic_block *, bool);
 269 extern bool remove_path (struct loops *, edge);
 270
 271 /* Induction variable analysis.  */
 272
 273 /* The description of induction variable.  The things are a bit complicated
 274    due to need to handle subregs and extends.  The value of the object described
 275    by it can be obtained as follows (all computations are done in extend_mode):
 276
 277    Value in i-th iteration is
 278      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 279
 280    If first_special is true, the value in the first iteration is
 281      delta + mult * base
 282
 283    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 284      subreg_{mode} (base + i * step)
 285
 286    The get_iv_value function can be used to obtain these expressions.
 287
 288    ??? Add a third mode field that would specify the mode in that inner
 289    computation is done, which would enable it to be different from the
 290    outer one?  */
 291
 292 struct rtx_iv
 293 {
 294   /* Its base and step (mode of base and step is supposed to be extend_mode,
 295      see the description above).  */
 296   rtx base, step;
 297
 298   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 299   enum rtx_code extend;
 300
 301   /* Operations applied in the extended mode.  */
 302   rtx delta, mult;
 303
 304   /* The mode it is extended to.  */
 305   enum machine_mode extend_mode;
 306
 307   /* The mode the variable iterates in.  */
 308   enum machine_mode mode;
 309
 310   /* Whether the first iteration needs to be handled specially.  */
 311   unsigned first_special : 1;
 312 };
 313
 314 /* The description of an exit from the loop and of the number of iterations
 315    till we take the exit.  */
 316
 317 struct niter_desc
 318 {
 319   /* The edge out of the loop.  */
 320   edge out_edge;
 321
 322   /* The other edge leading from the condition.  */
 323   edge in_edge;
 324
 325   /* True if we are able to say anything about number of iterations of the
 326      loop.  */
 327   bool simple_p;
 328
 329   /* True if the loop iterates the constant number of times.  */
 330   bool const_iter;
 331
 332   /* Number of iterations if constant.  */
 333   unsigned HOST_WIDEST_INT niter;
 334
 335   /* Upper bound on the number of iterations.  */
 336   unsigned HOST_WIDEST_INT niter_max;
 337
 338   /* Assumptions under that the rest of the information is valid.  */
 339   rtx assumptions;
 340
 341   /* Assumptions under that the loop ends before reaching the latch,
 342      even if value of niter_expr says otherwise.  */
 343   rtx noloop_assumptions;
 344
 345   /* Condition under that the loop is infinite.  */
 346   rtx infinite;
 347
 348   /* Whether the comparison is signed.  */
 349   bool signed_p;
 350
 351   /* The mode in that niter_expr should be computed.  */
 352   enum machine_mode mode;
 353
 354   /* The number of iterations of the loop.  */
 355   rtx niter_expr;
 356 };
 357
 358 extern void iv_analysis_loop_init (struct loop *);
 359 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 360 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 361 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 362 extern rtx get_iv_value (struct rtx_iv *, rtx);
 363 extern bool biv_p (rtx, rtx);
 364 extern void find_simple_exit (struct loop *, struct niter_desc *);
 365 extern void iv_analysis_done (void);
 366 extern struct df *iv_current_loop_df (void);
 367
 368 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 369 extern void free_simple_loop_desc (struct loop *loop);
 370
 371 static inline struct niter_desc *
 372 simple_loop_desc (struct loop *loop)
 373 {
 374   return (struct niter_desc *) loop->aux;
 375 }
 376
 377 /* The properties of the target.  */
 378
 379 extern unsigned target_avail_regs;      /* Number of available registers.  */
 380 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 381 extern unsigned target_small_cost;      /* The cost for register when there
 382                                            is a free one.  */
 383 extern unsigned target_pres_cost;       /* The cost for register when there are
 384                                            not too many free ones.  */
 385 extern unsigned target_spill_cost;      /* The cost for register when we need
 386                                            to spill.  */
 387
 388 /* Register pressure estimation for induction variable optimizations & loop
 389    invariant motion.  */
 390 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 391 extern void init_set_costs (void);
 392
 393 /* Loop optimizer initialization.  */
 394 extern struct loops *loop_optimizer_init (unsigned);
 395 extern void loop_optimizer_finalize (struct loops *);
 396
 397 /* Optimization passes.  */
 398 extern void unswitch_loops (struct loops *);
 399
 400 enum
 401 {
 402   UAP_PEEL = 1,         /* Enables loop peeling.  */
 403   UAP_UNROLL = 2,       /* Enables peeling of loops if it seems profitable.  */
 404   UAP_UNROLL_ALL = 4    /* Enables peeling of all loops.  */
 405 };
 406
 407 extern void unroll_and_peel_loops (struct loops *, int);
 408 extern void doloop_optimize_loops (struct loops *);
 409 extern void move_loop_invariants (struct loops *);
 410 extern void record_estimate (struct loop *, tree, tree, tree);
 411
 412 /* Old loop optimizer interface.  */
 413
 414 /* Flags passed to loop_optimize.  */
 415 #define LOOP_PREFETCH 1
 416
 417 #endif /* GCC_CFGLOOP_H */