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
 202 /* Loop data structure manipulation/querying.  */
 203 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 204 extern void flow_loop_tree_node_remove (struct loop *);
 205 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 206 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
 207 extern struct loop * find_common_loop (struct loop *, struct loop *);
 208 struct loop *superloop_at_depth (struct loop *, unsigned);
 209 extern unsigned tree_num_loop_insns (struct loop *);
 210 extern int num_loop_insns (struct loop *);
 211 extern int average_num_loop_insns (struct loop *);
 212 extern unsigned get_loop_level (const struct loop *);
 213 extern bool loop_exit_edge_p (const struct loop *, edge);
 214 extern void mark_loop_exit_edges (struct loops *);
 215
 216 /* Loops & cfg manipulation.  */
 217 extern basic_block *get_loop_body (const struct loop *);
 218 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 219 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 220 extern edge *get_loop_exit_edges (const struct loop *, unsigned *);
 221 extern unsigned num_loop_branches (const struct loop *);
 222
 223 extern edge loop_preheader_edge (const struct loop *);
 224 extern edge loop_latch_edge (const struct loop *);
 225
 226 extern void add_bb_to_loop (basic_block, struct loop *);
 227 extern void remove_bb_from_loops (basic_block);
 228
 229 extern void cancel_loop_tree (struct loops *, struct loop *);
 230
 231 extern basic_block loop_split_edge_with (edge, rtx);
 232 extern int fix_loop_placement (struct loop *);
 233
 234 enum
 235 {
 236   CP_SIMPLE_PREHEADERS = 1
 237 };
 238
 239 extern void create_preheaders (struct loops *, int);
 240 extern void force_single_succ_latches (struct loops *);
 241
 242 extern void verify_loop_structure (struct loops *);
 243
 244 /* Loop analysis.  */
 245 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
 246 extern unsigned expected_loop_iterations (const struct loop *);
 247 extern rtx doloop_condition_get (rtx);
 248
 249 /* Loop manipulation.  */
 250 extern bool can_duplicate_loop_p (struct loop *loop);
 251
 252 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 253                                            duplicate_loop_to_header_edge.  */
 254 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 255                                            field of newly create BB.  */
 256 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 257                                            a complete peeling.  */
 258
 259 extern struct loop * duplicate_loop (struct loops *, struct loop *,
 260                                      struct loop *);
 261 extern bool duplicate_loop_to_header_edge (struct loop *, edge, struct loops *,
 262                                            unsigned, sbitmap, edge, edge *,
 263                                            unsigned *, int);
 264 extern struct loop *loopify (struct loops *, edge, edge,
 265                              basic_block, edge, edge, bool);
 266 struct loop * loop_version (struct loops *, struct loop *, void *,
 267                             basic_block *, bool);
 268 extern bool remove_path (struct loops *, edge);
 269
 270 /* Induction variable analysis.  */
 271
 272 /* The description of induction variable.  The things are a bit complicated
 273    due to need to handle subregs and extends.  The value of the object described
 274    by it can be obtained as follows (all computations are done in extend_mode):
 275
 276    Value in i-th iteration is
 277      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 278
 279    If first_special is true, the value in the first iteration is
 280      delta + mult * base
 281
 282    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 283      subreg_{mode} (base + i * step)
 284
 285    The get_iv_value function can be used to obtain these expressions.
 286
 287    ??? Add a third mode field that would specify the mode in that inner
 288    computation is done, which would enable it to be different from the
 289    outer one?  */
 290
 291 struct rtx_iv
 292 {
 293   /* Its base and step (mode of base and step is supposed to be extend_mode,
 294      see the description above).  */
 295   rtx base, step;
 296
 297   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 298   enum rtx_code extend;
 299
 300   /* Operations applied in the extended mode.  */
 301   rtx delta, mult;
 302
 303   /* The mode it is extended to.  */
 304   enum machine_mode extend_mode;
 305
 306   /* The mode the variable iterates in.  */
 307   enum machine_mode mode;
 308
 309   /* Whether the first iteration needs to be handled specially.  */
 310   unsigned first_special : 1;
 311 };
 312
 313 /* The description of an exit from the loop and of the number of iterations
 314    till we take the exit.  */
 315
 316 struct niter_desc
 317 {
 318   /* The edge out of the loop.  */
 319   edge out_edge;
 320
 321   /* The other edge leading from the condition.  */
 322   edge in_edge;
 323
 324   /* True if we are able to say anything about number of iterations of the
 325      loop.  */
 326   bool simple_p;
 327
 328   /* True if the loop iterates the constant number of times.  */
 329   bool const_iter;
 330
 331   /* Number of iterations if constant.  */
 332   unsigned HOST_WIDEST_INT niter;
 333
 334   /* Upper bound on the number of iterations.  */
 335   unsigned HOST_WIDEST_INT niter_max;
 336
 337   /* Assumptions under that the rest of the information is valid.  */
 338   rtx assumptions;
 339
 340   /* Assumptions under that the loop ends before reaching the latch,
 341      even if value of niter_expr says otherwise.  */
 342   rtx noloop_assumptions;
 343
 344   /* Condition under that the loop is infinite.  */
 345   rtx infinite;
 346
 347   /* Whether the comparison is signed.  */
 348   bool signed_p;
 349
 350   /* The mode in that niter_expr should be computed.  */
 351   enum machine_mode mode;
 352
 353   /* The number of iterations of the loop.  */
 354   rtx niter_expr;
 355 };
 356
 357 extern void iv_analysis_loop_init (struct loop *);
 358 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 359 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 360 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 361 extern rtx get_iv_value (struct rtx_iv *, rtx);
 362 extern bool biv_p (rtx, rtx);
 363 extern void find_simple_exit (struct loop *, struct niter_desc *);
 364 extern void iv_analysis_done (void);
 365 extern struct df *iv_current_loop_df (void);
 366
 367 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 368 extern void free_simple_loop_desc (struct loop *loop);
 369
 370 static inline struct niter_desc *
 371 simple_loop_desc (struct loop *loop)
 372 {
 373   return (struct niter_desc *) loop->aux;
 374 }
 375
 376 /* The properties of the target.  */
 377
 378 extern unsigned target_avail_regs;      /* Number of available registers.  */
 379 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 380 extern unsigned target_small_cost;      /* The cost for register when there
 381                                            is a free one.  */
 382 extern unsigned target_pres_cost;       /* The cost for register when there are
 383                                            not too many free ones.  */
 384 extern unsigned target_spill_cost;      /* The cost for register when we need
 385                                            to spill.  */
 386
 387 /* Register pressure estimation for induction variable optimizations & loop
 388    invariant motion.  */
 389 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 390 extern void init_set_costs (void);
 391
 392 /* Loop optimizer initialization.  */
 393 extern struct loops *loop_optimizer_init (unsigned);
 394 extern void loop_optimizer_finalize (struct loops *);
 395
 396 /* Optimization passes.  */
 397 extern void unswitch_loops (struct loops *);
 398
 399 enum
 400 {
 401   UAP_PEEL = 1,         /* Enables loop peeling.  */
 402   UAP_UNROLL = 2,       /* Enables peeling of loops if it seems profitable.  */
 403   UAP_UNROLL_ALL = 4    /* Enables peeling of all loops.  */
 404 };
 405
 406 extern void unroll_and_peel_loops (struct loops *, int);
 407 extern void doloop_optimize_loops (struct loops *);
 408 extern void move_loop_invariants (struct loops *);
 409 extern void record_estimate (struct loop *, tree, tree, tree);
 410
 411 /* Old loop optimizer interface.  */
 412
 413 /* Flags passed to loop_optimize.  */
 414 #define LOOP_PREFETCH 1
 415
 416 #endif /* GCC_CFGLOOP_H */