1/* Natural loop functions 2 Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 3 Free Software Foundation, Inc. 4 5This file is part of GCC. 6 7GCC is free software; you can redistribute it and/or modify it under 8the terms of the GNU General Public License as published by the Free 9Software Foundation; either version 2, or (at your option) any later 10version. 11 12GCC is distributed in the hope that it will be useful, but WITHOUT ANY 13WARRANTY; without even the implied warranty of MERCHANTABILITY or 14FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15for more details. 16 17You should have received a copy of the GNU General Public License 18along with GCC; see the file COPYING. If not, write to the Free 19Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 2002110-1301, 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. */ 30enum 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 40struct 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 48struct 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. */ 61struct 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 /* The first block in the loop. This is not necessarily the same as 82 the loop header. */ 83 basic_block first; 84 85 /* The last block in the loop. This is not necessarily the same as 86 the loop latch. */ 87 basic_block last; 88 89 /* Number of blocks contained within the loop. */ 90 unsigned num_nodes; 91 92 /* The loop nesting depth. */ 93 int depth; 94 95 /* Superloops of the loop. */ 96 struct loop **pred; 97 98 /* The height of the loop (enclosed loop levels) within the loop 99 hierarchy tree. */ 100 int level; 101 102 /* The outer (parent) loop or NULL if outermost loop. */ 103 struct loop *outer; 104 105 /* The first inner (child) loop or NULL if innermost loop. */ 106 struct loop *inner; 107 108 /* Link to the next (sibling) loop. */ 109 struct loop *next; 110 111 /* Loop that is copy of this loop. */ 112 struct loop *copy; 113 114 /* Nonzero if the loop is invalid (e.g., contains setjmp.). */ 115 int invalid; 116 117 /* Auxiliary info specific to a pass. */ 118 void *aux; 119 120 /* The following are currently used by loop.c but they are likely to 121 disappear when loop.c is replaced and removed. */ 122 123 /* The NOTE_INSN_LOOP_BEG. */ 124 rtx start; 125 126 /* The NOTE_INSN_LOOP_END. */ 127 rtx end; 128 129 /* For a rotated loop that is entered near the bottom, 130 this is the label at the top. Otherwise it is zero. */ 131 rtx top; 132 133 /* Place in the loop where control enters. */ 134 rtx scan_start; 135 136 /* The position where to sink insns out of the loop. */ 137 rtx sink; 138 139 /* List of all LABEL_REFs which refer to code labels outside the 140 loop. Used by routines that need to know all loop exits, such as 141 final_biv_value and final_giv_value. 142 143 This does not include loop exits due to return instructions. 144 This is because all bivs and givs are pseudos, and hence must be 145 dead after a return, so the presence of a return does not affect 146 any of the optimizations that use this info. It is simpler to 147 just not include return instructions on this list. */ 148 rtx exit_labels; 149 150 /* The number of LABEL_REFs on exit_labels for this loop and all 151 loops nested inside it. */ 152 int exit_count; 153 154 /* The probable number of times the loop is executed at runtime. 155 This is an INTEGER_CST or an expression containing symbolic 156 names. Don't access this field directly: 157 number_of_iterations_in_loop computes and caches the computed 158 information in this field. */ 159 tree nb_iterations; 160 161 /* An INTEGER_CST estimation of the number of iterations. NULL_TREE 162 if there is no estimation. */ 163 tree estimated_nb_iterations; 164 165 /* Upper bound on number of iterations of a loop. */ 166 struct nb_iter_bound *bounds; 167 168 /* If not NULL, loop has just single exit edge stored here (edges to the 169 EXIT_BLOCK_PTR do not count. */ 170 edge single_exit; 171 172 /* True when the loop does not carry data dependences, and 173 consequently the iterations can be executed in any order. False 174 when the loop carries data dependences, or when the property is 175 not decidable. */ 176 bool parallel_p; 177}; 178 179/* Flags for state of loop structure. */ 180enum 181{ 182 LOOPS_HAVE_PREHEADERS = 1, 183 LOOPS_HAVE_SIMPLE_LATCHES = 2, 184 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4, 185 LOOPS_HAVE_MARKED_SINGLE_EXITS = 8 186}; 187 188/* Structure to hold CFG information about natural loops within a function. */ 189struct loops 190{ 191 /* Number of natural loops in the function. */ 192 unsigned num; 193 194 /* Array of natural loop descriptors (scanning this array in reverse order 195 will find the inner loops before their enclosing outer loops). */ 196 struct loop *array; 197 198 /* The above array is unused in new loop infrastructure and is kept only for 199 purposes of the old loop optimizer. Instead we store just pointers to 200 loops here. 201 Note that a loop in this array may actually be NULL, if the loop 202 has been removed and the entire loops structure has not been 203 recomputed since that time. */ 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/* The loop tree currently optimized. */ 228 229extern struct loops *current_loops; 230 231/* Loop recognition. */ 232extern int flow_loops_find (struct loops *); 233extern void flow_loops_free (struct loops *); 234extern void flow_loops_dump (const struct loops *, FILE *, 235 void (*)(const struct loop *, FILE *, int), int); 236extern void flow_loop_dump (const struct loop *, FILE *, 237 void (*)(const struct loop *, FILE *, int), int); 238extern void flow_loop_free (struct loop *); 239int flow_loop_nodes_find (basic_block, struct loop *); 240void fix_loop_structure (struct loops *, bitmap changed_bbs); 241void mark_irreducible_loops (struct loops *); 242void mark_single_exit_loops (struct loops *); 243extern void create_loop_notes (void); 244 245/* Loop data structure manipulation/querying. */ 246extern void flow_loop_tree_node_add (struct loop *, struct loop *); 247extern void flow_loop_tree_node_remove (struct loop *); 248extern bool flow_loop_outside_edge_p (const struct loop *, edge); 249extern bool flow_loop_nested_p (const struct loop *, const struct loop *); 250extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block); 251extern struct loop * find_common_loop (struct loop *, struct loop *); 252struct loop *superloop_at_depth (struct loop *, unsigned); 253extern unsigned tree_num_loop_insns (struct loop *); 254extern int num_loop_insns (struct loop *); 255extern int average_num_loop_insns (struct loop *); 256extern unsigned get_loop_level (const struct loop *); 257extern bool loop_exit_edge_p (const struct loop *, edge); 258extern void mark_loop_exit_edges (struct loops *); 259 260/* Loops & cfg manipulation. */ 261extern basic_block *get_loop_body (const struct loop *); 262extern basic_block *get_loop_body_in_dom_order (const struct loop *); 263extern basic_block *get_loop_body_in_bfs_order (const struct loop *); 264extern edge *get_loop_exit_edges (const struct loop *, unsigned *); 265extern unsigned num_loop_branches (const struct loop *); 266 267extern edge loop_preheader_edge (const struct loop *); 268extern edge loop_latch_edge (const struct loop *); 269 270extern void add_bb_to_loop (basic_block, struct loop *); 271extern void remove_bb_from_loops (basic_block); 272 273extern void cancel_loop (struct loops *, struct loop *); 274extern void cancel_loop_tree (struct loops *, struct loop *); 275 276extern basic_block loop_split_edge_with (edge, rtx); 277extern int fix_loop_placement (struct loop *); 278 279enum 280{ 281 CP_SIMPLE_PREHEADERS = 1 282}; 283 284extern void create_preheaders (struct loops *, int); 285extern void force_single_succ_latches (struct loops *); 286 287extern void verify_loop_structure (struct loops *); 288 289/* Loop analysis. */ 290extern bool just_once_each_iteration_p (const struct loop *, basic_block); 291extern unsigned expected_loop_iterations (const struct loop *); 292extern rtx doloop_condition_get (rtx); 293 294/* Loop manipulation. */ 295extern bool can_duplicate_loop_p (struct loop *loop); 296 297#define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in 298 duplicate_loop_to_header_edge. */ 299#define DLTHE_RECORD_COPY_NUMBER 2 /* Record copy number in the aux 300 field of newly create BB. */ 301#define DLTHE_FLAG_COMPLETTE_PEEL 4 /* Update frequencies expecting 302 a complete peeling. */ 303 304extern struct loop * duplicate_loop (struct loops *, struct loop *, 305 struct loop *); 306extern bool duplicate_loop_to_header_edge (struct loop *, edge, struct loops *, 307 unsigned, sbitmap, edge, edge *, 308 unsigned *, int); 309extern struct loop *loopify (struct loops *, edge, edge, 310 basic_block, edge, edge, bool); 311struct loop * loop_version (struct loops *, struct loop *, void *, 312 basic_block *, bool); 313extern bool remove_path (struct loops *, edge); 314extern edge split_loop_bb (basic_block, void *); 315 316/* Induction variable analysis. */ 317 318/* The description of induction variable. The things are a bit complicated 319 due to need to handle subregs and extends. The value of the object described 320 by it can be obtained as follows (all computations are done in extend_mode): 321 322 Value in i-th iteration is 323 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)). 324 325 If first_special is true, the value in the first iteration is 326 delta + mult * base 327 328 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is 329 subreg_{mode} (base + i * step) 330 331 The get_iv_value function can be used to obtain these expressions. 332 333 ??? Add a third mode field that would specify the mode in that inner 334 computation is done, which would enable it to be different from the 335 outer one? */ 336 337struct rtx_iv 338{ 339 /* Its base and step (mode of base and step is supposed to be extend_mode, 340 see the description above). */ 341 rtx base, step; 342 343 /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN). */ 344 enum rtx_code extend; 345 346 /* Operations applied in the extended mode. */ 347 rtx delta, mult; 348 349 /* The mode it is extended to. */ 350 enum machine_mode extend_mode; 351 352 /* The mode the variable iterates in. */ 353 enum machine_mode mode; 354 355 /* Whether we have already filled the remaining fields. */ 356 unsigned analysed : 1; 357 358 /* Whether the first iteration needs to be handled specially. */ 359 unsigned first_special : 1; 360}; 361 362/* The description of an exit from the loop and of the number of iterations 363 till we take the exit. */ 364 365struct niter_desc 366{ 367 /* The edge out of the loop. */ 368 edge out_edge; 369 370 /* The other edge leading from the condition. */ 371 edge in_edge; 372 373 /* True if we are able to say anything about number of iterations of the 374 loop. */ 375 bool simple_p; 376 377 /* True if the loop iterates the constant number of times. */ 378 bool const_iter; 379 380 /* Number of iterations if constant. */ 381 unsigned HOST_WIDEST_INT niter; 382 383 /* Upper bound on the number of iterations. */ 384 unsigned HOST_WIDEST_INT niter_max; 385 386 /* Assumptions under that the rest of the information is valid. */ 387 rtx assumptions; 388 389 /* Assumptions under that the loop ends before reaching the latch, 390 even if value of niter_expr says otherwise. */ 391 rtx noloop_assumptions; 392 393 /* Condition under that the loop is infinite. */ 394 rtx infinite; 395 396 /* Whether the comparison is signed. */ 397 bool signed_p; 398 399 /* The mode in that niter_expr should be computed. */ 400 enum machine_mode mode; 401 402 /* The number of iterations of the loop. */ 403 rtx niter_expr; 404}; 405 406extern void iv_analysis_loop_init (struct loop *); 407extern rtx iv_get_reaching_def (rtx, rtx); 408extern bool iv_analyze (rtx, rtx, struct rtx_iv *); 409extern rtx get_iv_value (struct rtx_iv *, rtx); 410extern bool biv_p (rtx, rtx); 411extern void find_simple_exit (struct loop *, struct niter_desc *); 412extern void iv_analysis_done (void); 413 414extern struct niter_desc *get_simple_loop_desc (struct loop *loop); 415extern void free_simple_loop_desc (struct loop *loop); 416 417static inline struct niter_desc * 418simple_loop_desc (struct loop *loop) 419{ 420 return loop->aux; 421} 422 423/* The properties of the target. */ 424 425extern unsigned target_avail_regs; /* Number of available registers. */ 426extern unsigned target_res_regs; /* Number of reserved registers. */ 427extern unsigned target_small_cost; /* The cost for register when there 428 is a free one. */ 429extern unsigned target_pres_cost; /* The cost for register when there are 430 not too many free ones. */ 431extern unsigned target_spill_cost; /* The cost for register when we need 432 to spill. */ 433 434/* Register pressure estimation for induction variable optimizations & loop 435 invariant motion. */ 436extern unsigned global_cost_for_size (unsigned, unsigned, unsigned); 437extern void init_set_costs (void); 438 439/* Loop optimizer initialization. */ 440extern struct loops *loop_optimizer_init (FILE *); 441extern void loop_optimizer_finalize (struct loops *, FILE *); 442 443/* Optimization passes. */ 444extern void unswitch_loops (struct loops *); 445 446enum 447{ 448 UAP_PEEL = 1, /* Enables loop peeling. */ 449 UAP_UNROLL = 2, /* Enables peeling of loops if it seems profitable. */ 450 UAP_UNROLL_ALL = 4 /* Enables peeling of all loops. */ 451}; 452 453extern void unroll_and_peel_loops (struct loops *, int); 454extern void doloop_optimize_loops (struct loops *); 455extern void move_loop_invariants (struct loops *); 456extern void record_estimate (struct loop *, tree, tree, tree); 457 458/* Old loop optimizer interface. */ 459 460/* Flags passed to loop_optimize. */ 461#define LOOP_PREFETCH 1 462 463extern void loop_optimize (rtx, FILE *, int); 464 465#endif /* GCC_CFGLOOP_H */ 466