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 constant expression whose value is an upper
  51                            bound on the number of executions of ...  */
  52   tree at_stmt;         /* ... this statement during one execution of
  53                            a loop.  */
  54   struct nb_iter_bound *next;
  55                         /* The next bound in a list.  */
  56 };
  57
  58 /* Structure to hold information for each natural loop.  */
  59 struct loop
  60 {
  61   /* Index into loops array.  */
  62   int num;
  63
  64   /* Basic block of loop header.  */
  65   basic_block header;
  66
  67   /* Basic block of loop latch.  */
  68   basic_block latch;
  69
  70   /* For loop unrolling/peeling decision.  */
  71   struct lpt_decision lpt_decision;
  72
  73   /* Number of loop insns.  */
  74   unsigned ninsns;
  75
  76   /* Average number of executed insns per iteration.  */
  77   unsigned av_ninsns;
  78
  79   /* Number of blocks contained within the loop.  */
  80   unsigned num_nodes;
  81
  82   /* The loop nesting depth.  */
  83   int depth;
  84
  85   /* Superloops of the loop.  */
  86   struct loop **pred;
  87
  88   /* The height of the loop (enclosed loop levels) within the loop
  89      hierarchy tree.  */
  90   int level;
  91
  92   /* The outer (parent) loop or NULL if outermost loop.  */
  93   struct loop *outer;
  94
  95   /* The first inner (child) loop or NULL if innermost loop.  */
  96   struct loop *inner;
  97
  98   /* Link to the next (sibling) loop.  */
  99   struct loop *next;
 100
 101   /* Loop that is copy of this loop.  */
 102   struct loop *copy;
 103
 104   /* Auxiliary info specific to a pass.  */
 105   void *aux;
 106
 107   /* The probable number of times the loop is executed at runtime.
 108      This is an INTEGER_CST or an expression containing symbolic
 109      names.  Don't access this field directly:
 110      number_of_iterations_in_loop computes and caches the computed
 111      information in this field.  */
 112   tree nb_iterations;
 113
 114   /* An INTEGER_CST estimation of the number of iterations.  NULL_TREE
 115      if there is no estimation.  */
 116   tree estimated_nb_iterations;
 117
 118   /* Upper bound on number of iterations of a loop.  */
 119   struct nb_iter_bound *bounds;
 120
 121   /* If not NULL, loop has just single exit edge stored here (edges to the
 122      EXIT_BLOCK_PTR do not count.  */
 123   edge single_exit;
 124
 125   /* True when the loop does not carry data dependences, and
 126      consequently the iterations can be executed in any order.  False
 127      when the loop carries data dependences, or when the property is
 128      not decidable.  */
 129   bool parallel_p;
 130 };
 131
 132 /* Flags for state of loop structure.  */
 133 enum
 134 {
 135   LOOPS_HAVE_PREHEADERS = 1,
 136   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 137   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
 138   LOOPS_HAVE_MARKED_SINGLE_EXITS = 8
 139 };
 140
 141 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
 142                       | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
 143
 144 /* Structure to hold CFG information about natural loops within a function.  */
 145 struct loops
 146 {
 147   /* Number of natural loops in the function.  */
 148   unsigned num;
 149
 150   /* State of loops.  */
 151   int state;
 152
 153   /* We store just pointers to loops here.
 154      Note that a loop in this array may actually be NULL, if the loop
 155      has been removed and the entire loops structure has not been
 156      recomputed since that time.  */
 157   struct loop **parray;
 158
 159   /* Pointer to root of loop hierarchy tree.  */
 160   struct loop *tree_root;
 161
 162   /* Information derived from the CFG.  */
 163   struct cfg
 164   {
 165     /* The ordering of the basic blocks in a depth first search.  */
 166     int *dfs_order;
 167
 168     /* The reverse completion ordering of the basic blocks found in a
 169        depth first search.  */
 170     int *rc_order;
 171   } cfg;
 172
 173   /* Headers shared by multiple loops that should be merged.  */
 174   sbitmap shared_headers;
 175 };
 176
 177 /* The loop tree currently optimized.  */
 178
 179 extern struct loops *current_loops;
 180
 181 /* Loop recognition.  */
 182 extern int flow_loops_find (struct loops *);
 183 extern void flow_loops_free (struct loops *);
 184 extern void flow_loops_dump (const struct loops *, FILE *,
 185                              void (*)(const struct loop *, FILE *, int), int);
 186 extern void flow_loop_dump (const struct loop *, FILE *,
 187                             void (*)(const struct loop *, FILE *, int), int);
 188 extern void flow_loop_free (struct loop *);
 189 int flow_loop_nodes_find (basic_block, struct loop *);
 190 void fix_loop_structure (struct loops *, bitmap changed_bbs);
 191 void mark_irreducible_loops (struct loops *);
 192 void mark_single_exit_loops (struct loops *);
 193
 194 /* Loop data structure manipulation/querying.  */
 195 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 196 extern void flow_loop_tree_node_remove (struct loop *);
 197 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 198 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
 199 extern struct loop * find_common_loop (struct loop *, struct loop *);
 200 struct loop *superloop_at_depth (struct loop *, unsigned);
 201 extern unsigned tree_num_loop_insns (struct loop *);
 202 extern int num_loop_insns (struct loop *);
 203 extern int average_num_loop_insns (struct loop *);
 204 extern unsigned get_loop_level (const struct loop *);
 205 extern bool loop_exit_edge_p (const struct loop *, edge);
 206 extern void mark_loop_exit_edges (struct loops *);
 207
 208 /* Loops & cfg manipulation.  */
 209 extern basic_block *get_loop_body (const struct loop *);
 210 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 211 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 212 extern edge *get_loop_exit_edges (const struct loop *, unsigned *);
 213 extern unsigned num_loop_branches (const struct loop *);
 214
 215 extern edge loop_preheader_edge (const struct loop *);
 216 extern edge loop_latch_edge (const struct loop *);
 217
 218 extern void add_bb_to_loop (basic_block, struct loop *);
 219 extern void remove_bb_from_loops (basic_block);
 220
 221 extern void cancel_loop_tree (struct loops *, struct loop *);
 222
 223 extern basic_block loop_split_edge_with (edge, rtx);
 224 extern int fix_loop_placement (struct loop *);
 225
 226 enum
 227 {
 228   CP_SIMPLE_PREHEADERS = 1
 229 };
 230
 231 extern void create_preheaders (struct loops *, int);
 232 extern void force_single_succ_latches (struct loops *);
 233
 234 extern void verify_loop_structure (struct loops *);
 235
 236 /* Loop analysis.  */
 237 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
 238 extern unsigned expected_loop_iterations (const struct loop *);
 239 extern rtx doloop_condition_get (rtx);
 240
 241 /* Loop manipulation.  */
 242 extern bool can_duplicate_loop_p (struct loop *loop);
 243
 244 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 245                                            duplicate_loop_to_header_edge.  */
 246 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 247                                            field of newly create BB.  */
 248 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 249                                            a complete peeling.  */
 250
 251 extern struct loop * duplicate_loop (struct loops *, struct loop *,
 252                                      struct loop *);
 253 extern bool duplicate_loop_to_header_edge (struct loop *, edge, struct loops *,
 254                                            unsigned, sbitmap, edge, edge *,
 255                                            unsigned *, int);
 256 extern struct loop *loopify (struct loops *, edge, edge,
 257                              basic_block, edge, edge, bool);
 258 struct loop * loop_version (struct loops *, struct loop *, void *,
 259                             basic_block *, bool);
 260 extern bool remove_path (struct loops *, edge);
 261
 262 /* Induction variable analysis.  */
 263
 264 /* The description of induction variable.  The things are a bit complicated
 265    due to need to handle subregs and extends.  The value of the object described
 266    by it can be obtained as follows (all computations are done in extend_mode):
 267
 268    Value in i-th iteration is
 269      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 270
 271    If first_special is true, the value in the first iteration is
 272      delta + mult * base
 273
 274    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 275      subreg_{mode} (base + i * step)
 276
 277    The get_iv_value function can be used to obtain these expressions.
 278
 279    ??? Add a third mode field that would specify the mode in that inner
 280    computation is done, which would enable it to be different from the
 281    outer one?  */
 282
 283 struct rtx_iv
 284 {
 285   /* Its base and step (mode of base and step is supposed to be extend_mode,
 286      see the description above).  */
 287   rtx base, step;
 288
 289   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 290   enum rtx_code extend;
 291
 292   /* Operations applied in the extended mode.  */
 293   rtx delta, mult;
 294
 295   /* The mode it is extended to.  */
 296   enum machine_mode extend_mode;
 297
 298   /* The mode the variable iterates in.  */
 299   enum machine_mode mode;
 300
 301   /* Whether the first iteration needs to be handled specially.  */
 302   unsigned first_special : 1;
 303 };
 304
 305 /* The description of an exit from the loop and of the number of iterations
 306    till we take the exit.  */
 307
 308 struct niter_desc
 309 {
 310   /* The edge out of the loop.  */
 311   edge out_edge;
 312
 313   /* The other edge leading from the condition.  */
 314   edge in_edge;
 315
 316   /* True if we are able to say anything about number of iterations of the
 317      loop.  */
 318   bool simple_p;
 319
 320   /* True if the loop iterates the constant number of times.  */
 321   bool const_iter;
 322
 323   /* Number of iterations if constant.  */
 324   unsigned HOST_WIDEST_INT niter;
 325
 326   /* Upper bound on the number of iterations.  */
 327   unsigned HOST_WIDEST_INT niter_max;
 328
 329   /* Assumptions under that the rest of the information is valid.  */
 330   rtx assumptions;
 331
 332   /* Assumptions under that the loop ends before reaching the latch,
 333      even if value of niter_expr says otherwise.  */
 334   rtx noloop_assumptions;
 335
 336   /* Condition under that the loop is infinite.  */
 337   rtx infinite;
 338
 339   /* Whether the comparison is signed.  */
 340   bool signed_p;
 341
 342   /* The mode in that niter_expr should be computed.  */
 343   enum machine_mode mode;
 344
 345   /* The number of iterations of the loop.  */
 346   rtx niter_expr;
 347 };
 348
 349 extern void iv_analysis_loop_init (struct loop *);
 350 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 351 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 352 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 353 extern rtx get_iv_value (struct rtx_iv *, rtx);
 354 extern bool biv_p (rtx, rtx);
 355 extern void find_simple_exit (struct loop *, struct niter_desc *);
 356 extern void iv_analysis_done (void);
 357 extern struct df *iv_current_loop_df (void);
 358
 359 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 360 extern void free_simple_loop_desc (struct loop *loop);
 361
 362 static inline struct niter_desc *
 363 simple_loop_desc (struct loop *loop)
 364 {
 365   return (struct niter_desc *) loop->aux;
 366 }
 367
 368 /* The properties of the target.  */
 369
 370 extern unsigned target_avail_regs;      /* Number of available registers.  */
 371 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 372 extern unsigned target_small_cost;      /* The cost for register when there
 373                                            is a free one.  */
 374 extern unsigned target_pres_cost;       /* The cost for register when there are
 375                                            not too many free ones.  */
 376 extern unsigned target_spill_cost;      /* The cost for register when we need
 377                                            to spill.  */
 378
 379 /* Register pressure estimation for induction variable optimizations & loop
 380    invariant motion.  */
 381 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 382 extern void init_set_costs (void);
 383
 384 /* Loop optimizer initialization.  */
 385 extern struct loops *loop_optimizer_init (unsigned);
 386 extern void loop_optimizer_finalize (struct loops *);
 387
 388 /* Optimization passes.  */
 389 extern void unswitch_loops (struct loops *);
 390
 391 enum
 392 {
 393   UAP_PEEL = 1,         /* Enables loop peeling.  */
 394   UAP_UNROLL = 2,       /* Enables peeling of loops if it seems profitable.  */
 395   UAP_UNROLL_ALL = 4    /* Enables peeling of all loops.  */
 396 };
 397
 398 extern void unroll_and_peel_loops (struct loops *, int);
 399 extern void doloop_optimize_loops (struct loops *);
 400 extern void move_loop_invariants (struct loops *);
 401 extern void record_estimate (struct loop *, tree, tree, tree);
 402
 403 #endif /* GCC_CFGLOOP_H */