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   /* State of loops.  */
 153   int state;
 154
 155   /* We store just pointers to loops here.
 156      Note that a loop in this array may actually be NULL, if the loop
 157      has been removed and the entire loops structure has not been
 158      recomputed since that time.  */
 159   struct loop **parray;
 160
 161   /* Pointer to root of loop hierarchy tree.  */
 162   struct loop *tree_root;
 163
 164   /* Information derived from the CFG.  */
 165   struct cfg
 166   {
 167     /* The ordering of the basic blocks in a depth first search.  */
 168     int *dfs_order;
 169
 170     /* The reverse completion ordering of the basic blocks found in a
 171        depth first search.  */
 172     int *rc_order;
 173   } cfg;
 174
 175   /* Headers shared by multiple loops that should be merged.  */
 176   sbitmap shared_headers;
 177 };
 178
 179 /* The loop tree currently optimized.  */
 180
 181 extern struct loops *current_loops;
 182
 183 /* Loop recognition.  */
 184 extern int flow_loops_find (struct loops *);
 185 extern void flow_loops_free (struct loops *);
 186 extern void flow_loops_dump (const struct loops *, FILE *,
 187                              void (*)(const struct loop *, FILE *, int), int);
 188 extern void flow_loop_dump (const struct loop *, FILE *,
 189                             void (*)(const struct loop *, FILE *, int), int);
 190 extern void flow_loop_free (struct loop *);
 191 int flow_loop_nodes_find (basic_block, struct loop *);
 192 void fix_loop_structure (struct loops *, bitmap changed_bbs);
 193 void mark_irreducible_loops (struct loops *);
 194 void mark_single_exit_loops (struct loops *);
 195
 196 /* Loop data structure manipulation/querying.  */
 197 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 198 extern void flow_loop_tree_node_remove (struct loop *);
 199 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 200 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
 201 extern struct loop * find_common_loop (struct loop *, struct loop *);
 202 struct loop *superloop_at_depth (struct loop *, unsigned);
 203 extern unsigned tree_num_loop_insns (struct loop *);
 204 extern int num_loop_insns (struct loop *);
 205 extern int average_num_loop_insns (struct loop *);
 206 extern unsigned get_loop_level (const struct loop *);
 207 extern bool loop_exit_edge_p (const struct loop *, edge);
 208 extern void mark_loop_exit_edges (struct loops *);
 209
 210 /* Loops & cfg manipulation.  */
 211 extern basic_block *get_loop_body (const struct loop *);
 212 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 213 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
 214 extern edge *get_loop_exit_edges (const struct loop *, unsigned *);
 215 extern unsigned num_loop_branches (const struct loop *);
 216
 217 extern edge loop_preheader_edge (const struct loop *);
 218 extern edge loop_latch_edge (const struct loop *);
 219
 220 extern void add_bb_to_loop (basic_block, struct loop *);
 221 extern void remove_bb_from_loops (basic_block);
 222
 223 extern void cancel_loop_tree (struct loops *, struct loop *);
 224
 225 extern basic_block loop_split_edge_with (edge, rtx);
 226 extern int fix_loop_placement (struct loop *);
 227
 228 enum
 229 {
 230   CP_SIMPLE_PREHEADERS = 1
 231 };
 232
 233 extern void create_preheaders (struct loops *, int);
 234 extern void force_single_succ_latches (struct loops *);
 235
 236 extern void verify_loop_structure (struct loops *);
 237
 238 /* Loop analysis.  */
 239 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
 240 extern unsigned expected_loop_iterations (const struct loop *);
 241 extern rtx doloop_condition_get (rtx);
 242
 243 /* Loop manipulation.  */
 244 extern bool can_duplicate_loop_p (struct loop *loop);
 245
 246 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 247                                            duplicate_loop_to_header_edge.  */
 248 #define DLTHE_RECORD_COPY_NUMBER 2      /* Record copy number in the aux
 249                                            field of newly create BB.  */
 250 #define DLTHE_FLAG_COMPLETTE_PEEL 4     /* Update frequencies expecting
 251                                            a complete peeling.  */
 252
 253 extern struct loop * duplicate_loop (struct loops *, struct loop *,
 254                                      struct loop *);
 255 extern bool duplicate_loop_to_header_edge (struct loop *, edge, struct loops *,
 256                                            unsigned, sbitmap, edge, edge *,
 257                                            unsigned *, int);
 258 extern struct loop *loopify (struct loops *, edge, edge,
 259                              basic_block, edge, edge, bool);
 260 struct loop * loop_version (struct loops *, struct loop *, void *,
 261                             basic_block *, bool);
 262 extern bool remove_path (struct loops *, edge);
 263
 264 /* Induction variable analysis.  */
 265
 266 /* The description of induction variable.  The things are a bit complicated
 267    due to need to handle subregs and extends.  The value of the object described
 268    by it can be obtained as follows (all computations are done in extend_mode):
 269
 270    Value in i-th iteration is
 271      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 272
 273    If first_special is true, the value in the first iteration is
 274      delta + mult * base
 275
 276    If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
 277      subreg_{mode} (base + i * step)
 278
 279    The get_iv_value function can be used to obtain these expressions.
 280
 281    ??? Add a third mode field that would specify the mode in that inner
 282    computation is done, which would enable it to be different from the
 283    outer one?  */
 284
 285 struct rtx_iv
 286 {
 287   /* Its base and step (mode of base and step is supposed to be extend_mode,
 288      see the description above).  */
 289   rtx base, step;
 290
 291   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
 292   enum rtx_code extend;
 293
 294   /* Operations applied in the extended mode.  */
 295   rtx delta, mult;
 296
 297   /* The mode it is extended to.  */
 298   enum machine_mode extend_mode;
 299
 300   /* The mode the variable iterates in.  */
 301   enum machine_mode mode;
 302
 303   /* Whether the first iteration needs to be handled specially.  */
 304   unsigned first_special : 1;
 305 };
 306
 307 /* The description of an exit from the loop and of the number of iterations
 308    till we take the exit.  */
 309
 310 struct niter_desc
 311 {
 312   /* The edge out of the loop.  */
 313   edge out_edge;
 314
 315   /* The other edge leading from the condition.  */
 316   edge in_edge;
 317
 318   /* True if we are able to say anything about number of iterations of the
 319      loop.  */
 320   bool simple_p;
 321
 322   /* True if the loop iterates the constant number of times.  */
 323   bool const_iter;
 324
 325   /* Number of iterations if constant.  */
 326   unsigned HOST_WIDEST_INT niter;
 327
 328   /* Upper bound on the number of iterations.  */
 329   unsigned HOST_WIDEST_INT niter_max;
 330
 331   /* Assumptions under that the rest of the information is valid.  */
 332   rtx assumptions;
 333
 334   /* Assumptions under that the loop ends before reaching the latch,
 335      even if value of niter_expr says otherwise.  */
 336   rtx noloop_assumptions;
 337
 338   /* Condition under that the loop is infinite.  */
 339   rtx infinite;
 340
 341   /* Whether the comparison is signed.  */
 342   bool signed_p;
 343
 344   /* The mode in that niter_expr should be computed.  */
 345   enum machine_mode mode;
 346
 347   /* The number of iterations of the loop.  */
 348   rtx niter_expr;
 349 };
 350
 351 extern void iv_analysis_loop_init (struct loop *);
 352 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 353 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
 354 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
 355 extern rtx get_iv_value (struct rtx_iv *, rtx);
 356 extern bool biv_p (rtx, rtx);
 357 extern void find_simple_exit (struct loop *, struct niter_desc *);
 358 extern void iv_analysis_done (void);
 359 extern struct df *iv_current_loop_df (void);
 360
 361 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 362 extern void free_simple_loop_desc (struct loop *loop);
 363
 364 static inline struct niter_desc *
 365 simple_loop_desc (struct loop *loop)
 366 {
 367   return (struct niter_desc *) loop->aux;
 368 }
 369
 370 /* The properties of the target.  */
 371
 372 extern unsigned target_avail_regs;      /* Number of available registers.  */
 373 extern unsigned target_res_regs;        /* Number of reserved registers.  */
 374 extern unsigned target_small_cost;      /* The cost for register when there
 375                                            is a free one.  */
 376 extern unsigned target_pres_cost;       /* The cost for register when there are
 377                                            not too many free ones.  */
 378 extern unsigned target_spill_cost;      /* The cost for register when we need
 379                                            to spill.  */
 380
 381 /* Register pressure estimation for induction variable optimizations & loop
 382    invariant motion.  */
 383 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
 384 extern void init_set_costs (void);
 385
 386 /* Loop optimizer initialization.  */
 387 extern struct loops *loop_optimizer_init (unsigned);
 388 extern void loop_optimizer_finalize (struct loops *);
 389
 390 /* Optimization passes.  */
 391 extern void unswitch_loops (struct loops *);
 392
 393 enum
 394 {
 395   UAP_PEEL = 1,         /* Enables loop peeling.  */
 396   UAP_UNROLL = 2,       /* Enables peeling of loops if it seems profitable.  */
 397   UAP_UNROLL_ALL = 4    /* Enables peeling of all loops.  */
 398 };
 399
 400 extern void unroll_and_peel_loops (struct loops *, int);
 401 extern void doloop_optimize_loops (struct loops *);
 402 extern void move_loop_invariants (struct loops *);
 403 extern void record_estimate (struct loop *, tree, tree, tree);
 404
 405 #endif /* GCC_CFGLOOP_H */