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
 180 /* Flags for state of loop structure.  */
 181 enum
 182 {
 183   LOOPS_HAVE_PREHEADERS = 1,
 184   LOOPS_HAVE_SIMPLE_LATCHES = 2,
 185   LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4
 186 };
 187
 188 /* Structure to hold CFG information about natural loops within a function.  */
 189 struct loops
 190 {
 191   /* Number of natural loops in the function.  */
 192   unsigned num;
 193
 194   /* Maximum nested loop level in the function.  */
 195   unsigned levels;
 196
 197   /* Array of natural loop descriptors (scanning this array in reverse order
 198      will find the inner loops before their enclosing outer loops).  */
 199   struct loop *array;
 200
 201   /* The above array is unused in new loop infrastructure and is kept only for
 202      purposes of the old loop optimizer.  Instead we store just pointers to
 203      loops here.  */
 204   struct loop **parray;
 205
 206   /* Pointer to root of loop hierarchy tree.  */
 207   struct loop *tree_root;
 208
 209   /* Information derived from the CFG.  */
 210   struct cfg
 211   {
 212     /* The ordering of the basic blocks in a depth first search.  */
 213     int *dfs_order;
 214
 215     /* The reverse completion ordering of the basic blocks found in a
 216        depth first search.  */
 217     int *rc_order;
 218   } cfg;
 219
 220   /* Headers shared by multiple loops that should be merged.  */
 221   sbitmap shared_headers;
 222
 223   /* State of loops.  */
 224   int state;
 225 };
 226
 227 /* Flags for loop discovery.  */
 228
 229 #define LOOP_TREE               1       /* Build loop hierarchy tree.  */
 230 #define LOOP_PRE_HEADER         2       /* Analyze loop preheader.  */
 231 #define LOOP_ENTRY_EDGES        4       /* Find entry edges.  */
 232 #define LOOP_EXIT_EDGES         8       /* Find exit edges.  */
 233 #define LOOP_EDGES              (LOOP_ENTRY_EDGES | LOOP_EXIT_EDGES)
 234 #define LOOP_ALL               15       /* All of the above  */
 235
 236 /* Loop recognition.  */
 237 extern int flow_loops_find (struct loops *, int flags);
 238 extern int flow_loops_update (struct loops *, int flags);
 239 extern void flow_loops_free (struct loops *);
 240 extern void flow_loops_dump (const struct loops *, FILE *,
 241                              void (*)(const struct loop *, FILE *, int), int);
 242 extern void flow_loop_dump (const struct loop *, FILE *,
 243                             void (*)(const struct loop *, FILE *, int), int);
 244 extern int flow_loop_scan (struct loop *, int);
 245 extern void flow_loop_free (struct loop *);
 246 void mark_irreducible_loops (struct loops *);
 247 extern void create_loop_notes (void);
 248
 249 /* Loop data structure manipulation/querying.  */
 250 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
 251 extern void flow_loop_tree_node_remove (struct loop *);
 252 extern bool flow_loop_outside_edge_p (const struct loop *, edge);
 253 extern bool flow_loop_nested_p  (const struct loop *, const struct loop *);
 254 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
 255 extern struct loop * find_common_loop (struct loop *, struct loop *);
 256 extern int num_loop_insns (struct loop *);
 257 extern int average_num_loop_insns (struct loop *);
 258 extern unsigned get_loop_level (const struct loop *);
 259
 260 /* Loops & cfg manipulation.  */
 261 extern basic_block *get_loop_body (const struct loop *);
 262 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
 263 extern edge *get_loop_exit_edges (const struct loop *, unsigned *);
 264 extern unsigned num_loop_branches (const struct loop *);
 265
 266 extern edge loop_preheader_edge (const struct loop *);
 267 extern edge loop_latch_edge (const struct loop *);
 268
 269 extern void add_bb_to_loop (basic_block, struct loop *);
 270 extern void remove_bb_from_loops (basic_block);
 271
 272 extern void cancel_loop (struct loops *, struct loop *);
 273 extern void cancel_loop_tree (struct loops *, struct loop *);
 274
 275 extern basic_block loop_split_edge_with (edge, rtx);
 276 extern int fix_loop_placement (struct loop *);
 277
 278 enum
 279 {
 280   CP_SIMPLE_PREHEADERS = 1
 281 };
 282
 283 extern void create_preheaders (struct loops *, int);
 284 extern void force_single_succ_latches (struct loops *);
 285
 286 extern void verify_loop_structure (struct loops *);
 287
 288 /* Loop analysis.  */
 289 extern bool just_once_each_iteration_p (struct loop *, basic_block);
 290 extern unsigned expected_loop_iterations (const struct loop *);
 291
 292 /* Loop manipulation.  */
 293 extern bool can_duplicate_loop_p (struct loop *loop);
 294
 295 #define DLTHE_FLAG_UPDATE_FREQ  1       /* Update frequencies in
 296                                            duplicate_loop_to_header_edge.  */
 297
 298 extern int duplicate_loop_to_header_edge (struct loop *, edge, struct loops *,
 299                                           unsigned, sbitmap, edge, edge *,
 300                                           unsigned *, int);
 301 extern struct loop *loopify (struct loops *, edge, edge, basic_block);
 302 extern void unloop (struct loops *, struct loop *);
 303 extern bool remove_path (struct loops *, edge);
 304 extern edge split_loop_bb (basic_block, rtx);
 305
 306 /* Induction variable analysis.  */
 307
 308 /* The description of induction variable.  The things are a bit complicated
 309    due to need to handle subregs and extends.  The value of the object described
 310    by it can be obtained as follows (all computations are done in extend_mode):
 311
 312    Value in i-th iteration is
 313      delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
 314
 315    If first_special is true, the value in the first iteration is
 316      delta + mult * base
 317
 318    If extend = NIL, first_special must be false, delta 0, mult 1 and value is
 319      subreg_{mode} (base + i * step)
 320
 321    The get_iv_value function can be used to obtain these expressions.
 322
 323    ??? Add a third mode field that would specify the mode in that inner
 324    computation is done, which would enable it to be different from the
 325    outer one?  */
 326
 327 struct rtx_iv
 328 {
 329   /* Its base and step (mode of base and step is supposed to be extend_mode,
 330      see the description above).  */
 331   rtx base, step;
 332
 333   /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or NIL).  */
 334   enum rtx_code extend;
 335
 336   /* Operations applied in the extended mode.  */
 337   rtx delta, mult;
 338
 339   /* The mode it is extended to.  */
 340   enum machine_mode extend_mode;
 341
 342   /* The mode the variable iterates in.  */
 343   enum machine_mode mode;
 344
 345   /* Whether we have already filled the remaining fields.  */
 346   unsigned analysed : 1;
 347
 348   /* Whether the first iteration needs to be handled specially.  */
 349   unsigned first_special : 1;
 350 };
 351
 352 /* The description of an exit from the loop and of the number of iterations
 353    till we take the exit.  */
 354
 355 struct niter_desc
 356 {
 357   /* The edge out of the loop.  */
 358   edge out_edge;
 359
 360   /* The other edge leading from the condition.  */
 361   edge in_edge;
 362
 363   /* True if we are able to say anything about number of iterations of the
 364      loop.  */
 365   bool simple_p;
 366
 367   /* True if the loop iterates the constant number of times.  */
 368   bool const_iter;
 369
 370   /* Number of iterations if constant.  */
 371   unsigned HOST_WIDEST_INT niter;
 372
 373   /* Upper bound on the number of iterations.  */
 374   unsigned HOST_WIDEST_INT niter_max;
 375
 376   /* Assumptions under that the rest of the information is valid.  */
 377   rtx assumptions;
 378
 379   /* Assumptions under that the loop ends before reaching the latch,
 380      even if value of niter_expr says otherwise.  */
 381   rtx noloop_assumptions;
 382
 383   /* Condition under that the loop is infinite.  */
 384   rtx infinite;
 385
 386   /* Whether the comparison is signed.  */
 387   bool signed_p;
 388
 389   /* The mode in that niter_expr should be computed.  */
 390   enum machine_mode mode;
 391
 392   /* The number of iterations of the loop.  */
 393   rtx niter_expr;
 394 };
 395
 396 extern void iv_analysis_loop_init (struct loop *);
 397 extern rtx iv_get_reaching_def (rtx, rtx);
 398 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
 399 extern rtx get_iv_value (struct rtx_iv *, rtx);
 400 extern void find_simple_exit (struct loop *, struct niter_desc *);
 401 extern void iv_number_of_iterations (struct loop *, rtx, rtx,
 402                                      struct niter_desc *);
 403 extern void iv_analysis_done (void);
 404
 405 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
 406 extern void free_simple_loop_desc (struct loop *loop);
 407
 408 static inline struct niter_desc *
 409 simple_loop_desc (struct loop *loop)
 410 {
 411   return loop->aux;
 412 }
 413
 414 /* Loop optimizer initialization.  */
 415 extern struct loops *loop_optimizer_init (FILE *);
 416 extern void loop_optimizer_finalize (struct loops *, FILE *);
 417
 418 /* Optimization passes.  */
 419 extern void unswitch_loops (struct loops *);
 420
 421 enum
 422 {
 423   UAP_PEEL = 1,         /* Enables loop peeling.  */
 424   UAP_UNROLL = 2,       /* Enables peeling of loops if it seems profitable.  */
 425   UAP_UNROLL_ALL = 4    /* Enables peeling of all loops.  */
 426 };
 427
 428 extern void unroll_and_peel_loops (struct loops *, int);
 429 extern void doloop_optimize_loops (struct loops *);
 430
 431 #endif /* GCC_CFGLOOP_H */