1 /* Natural loop functions
2 Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
3 Free Software Foundation, Inc.
5 This file is part of GCC.
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
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
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
25 #include "basic-block.h"
29 /* Structure to hold decision about unrolling/peeling. */
42 enum lpt_dec decision;
46 /* The structure describing a bound on number of iterations of a loop. */
50 /* The statement STMT is executed at most ... */
53 /* ... BOUND + 1 times (BOUND must be an unsigned constant).
54 The + 1 is added for the following reasons:
56 a) 0 would otherwise be unused, while we would need to care more about
57 overflows (as MAX + 1 is sometimes produced as the estimate on number
58 of executions of STMT).
59 b) it is consistent with the result of number_of_iterations_exit. */
62 /* True if the statement will cause the loop to be leaved the (at most)
63 BOUND + 1-st time it is executed, that is, all the statements after it
64 are executed at most BOUND times. */
67 /* True if the bound is "realistic" -- i.e., most likely the loop really has
68 number of iterations close to the bound. Exact bounds (if the number of
69 iterations of a loop is a constant) and bounds derived from the size of
70 data accessed in the loop are considered realistic. */
73 /* The next bound in the list. */
74 struct nb_iter_bound *next;
77 /* Description of the loop exit. */
84 /* Previous and next exit in the list of the exits of the loop. */
85 struct loop_exit *prev;
86 struct loop_exit *next;
88 /* Next element in the list of loops from that E exits. */
89 struct loop_exit *next_e;
92 /* Structure to hold information for each natural loop. */
95 /* Index into loops array. */
98 /* Basic block of loop header. */
101 /* Basic block of loop latch. */
104 /* For loop unrolling/peeling decision. */
105 struct lpt_decision lpt_decision;
107 /* Number of loop insns. */
110 /* Average number of executed insns per iteration. */
113 /* Number of blocks contained within the loop. */
116 /* The loop nesting depth. */
119 /* Superloops of the loop. */
122 /* The outer (parent) loop or NULL if outermost loop. */
125 /* The first inner (child) loop or NULL if innermost loop. */
128 /* Link to the next (sibling) loop. */
131 /* Loop that is copy of this loop. */
134 /* Auxiliary info specific to a pass. */
137 /* The number of times the latch of the loop is executed.
138 This is an INTEGER_CST or an expression containing symbolic
139 names. Don't access this field directly:
140 number_of_latch_executions computes and caches the computed
141 information in this field. */
144 /* An integer estimation of the number of iterations. Estimate_state
145 describes what is the state of the estimation. */
148 /* Estimate was not computed yet. */
150 /* Estimate was computed, but we could derive no useful bound. */
152 /* Estimate is ready. */
155 double_int estimated_nb_iterations;
157 /* Upper bound on number of iterations of a loop. */
158 struct nb_iter_bound *bounds;
160 /* Head of the cyclic list of the exits of the loop. */
161 struct loop_exit exits;
164 /* Flags for state of loop structure. */
167 LOOPS_HAVE_PREHEADERS = 1,
168 LOOPS_HAVE_SIMPLE_LATCHES = 2,
169 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
170 LOOPS_HAVE_RECORDED_EXITS = 8
173 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
174 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
176 typedef struct loop *loop_p;
178 DEF_VEC_ALLOC_P (loop_p, heap);
180 /* Structure to hold CFG information about natural loops within a function. */
183 /* State of loops. */
186 /* Array of the loops. */
187 VEC (loop_p, heap) *larray;
189 /* Maps edges to the list of their descriptions as loop exits. Edges
190 whose sources or destinations have loop_father == NULL (which may
191 happen during the cfg manipulations) should not appear in EXITS. */
194 /* Pointer to root of loop hierarchy tree. */
195 struct loop *tree_root;
198 /* Loop recognition. */
199 extern int flow_loops_find (struct loops *);
200 extern void flow_loops_free (struct loops *);
201 extern void flow_loops_dump (FILE *,
202 void (*)(const struct loop *, FILE *, int), int);
203 extern void flow_loop_dump (const struct loop *, FILE *,
204 void (*)(const struct loop *, FILE *, int), int);
205 struct loop *alloc_loop (void);
206 extern void flow_loop_free (struct loop *);
207 int flow_loop_nodes_find (basic_block, struct loop *);
208 void fix_loop_structure (bitmap changed_bbs);
209 void mark_irreducible_loops (void);
210 void release_recorded_exits (void);
211 void record_loop_exits (void);
212 void rescan_loop_exit (edge, bool, bool);
214 /* Loop data structure manipulation/querying. */
215 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
216 extern void flow_loop_tree_node_remove (struct loop *);
217 extern bool flow_loop_nested_p (const struct loop *, const struct loop *);
218 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
219 extern struct loop * find_common_loop (struct loop *, struct loop *);
220 struct loop *superloop_at_depth (struct loop *, unsigned);
221 extern unsigned tree_num_loop_insns (struct loop *);
222 extern int num_loop_insns (struct loop *);
223 extern int average_num_loop_insns (struct loop *);
224 extern unsigned get_loop_level (const struct loop *);
225 extern bool loop_exit_edge_p (const struct loop *, edge);
226 extern void mark_loop_exit_edges (void);
228 /* Loops & cfg manipulation. */
229 extern basic_block *get_loop_body (const struct loop *);
230 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
231 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
232 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
233 edge single_exit (const struct loop *);
234 extern unsigned num_loop_branches (const struct loop *);
236 extern edge loop_preheader_edge (const struct loop *);
237 extern edge loop_latch_edge (const struct loop *);
239 extern void add_bb_to_loop (basic_block, struct loop *);
240 extern void remove_bb_from_loops (basic_block);
242 extern void cancel_loop_tree (struct loop *);
243 extern void delete_loop (struct loop *);
247 CP_SIMPLE_PREHEADERS = 1
250 extern void create_preheaders (int);
251 extern void force_single_succ_latches (void);
253 extern void verify_loop_structure (void);
256 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
257 extern unsigned expected_loop_iterations (const struct loop *);
258 extern rtx doloop_condition_get (rtx);
260 /* Loop manipulation. */
261 extern bool can_duplicate_loop_p (struct loop *loop);
263 #define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in
264 duplicate_loop_to_header_edge. */
265 #define DLTHE_RECORD_COPY_NUMBER 2 /* Record copy number in the aux
266 field of newly create BB. */
267 #define DLTHE_FLAG_COMPLETTE_PEEL 4 /* Update frequencies expecting
268 a complete peeling. */
270 extern struct loop * duplicate_loop (struct loop *, struct loop *);
271 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
272 unsigned, sbitmap, edge,
273 VEC (edge, heap) **, int);
274 extern struct loop *loopify (edge, edge,
275 basic_block, edge, edge, bool,
277 struct loop * loop_version (struct loop *, void *,
278 basic_block *, unsigned, unsigned, unsigned, bool);
279 extern bool remove_path (edge);
280 void scale_loop_frequencies (struct loop *, int, int);
282 /* Induction variable analysis. */
284 /* The description of induction variable. The things are a bit complicated
285 due to need to handle subregs and extends. The value of the object described
286 by it can be obtained as follows (all computations are done in extend_mode):
288 Value in i-th iteration is
289 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
291 If first_special is true, the value in the first iteration is
294 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
295 subreg_{mode} (base + i * step)
297 The get_iv_value function can be used to obtain these expressions.
299 ??? Add a third mode field that would specify the mode in that inner
300 computation is done, which would enable it to be different from the
305 /* Its base and step (mode of base and step is supposed to be extend_mode,
306 see the description above). */
309 /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN). */
310 enum rtx_code extend;
312 /* Operations applied in the extended mode. */
315 /* The mode it is extended to. */
316 enum machine_mode extend_mode;
318 /* The mode the variable iterates in. */
319 enum machine_mode mode;
321 /* Whether the first iteration needs to be handled specially. */
322 unsigned first_special : 1;
325 /* The description of an exit from the loop and of the number of iterations
326 till we take the exit. */
330 /* The edge out of the loop. */
333 /* The other edge leading from the condition. */
336 /* True if we are able to say anything about number of iterations of the
340 /* True if the loop iterates the constant number of times. */
343 /* Number of iterations if constant. */
344 unsigned HOST_WIDEST_INT niter;
346 /* Upper bound on the number of iterations. */
347 unsigned HOST_WIDEST_INT niter_max;
349 /* Assumptions under that the rest of the information is valid. */
352 /* Assumptions under that the loop ends before reaching the latch,
353 even if value of niter_expr says otherwise. */
354 rtx noloop_assumptions;
356 /* Condition under that the loop is infinite. */
359 /* Whether the comparison is signed. */
362 /* The mode in that niter_expr should be computed. */
363 enum machine_mode mode;
365 /* The number of iterations of the loop. */
369 extern void iv_analysis_loop_init (struct loop *);
370 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
371 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
372 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
373 extern rtx get_iv_value (struct rtx_iv *, rtx);
374 extern bool biv_p (rtx, rtx);
375 extern void find_simple_exit (struct loop *, struct niter_desc *);
376 extern void iv_analysis_done (void);
377 extern struct df *iv_current_loop_df (void);
379 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
380 extern void free_simple_loop_desc (struct loop *loop);
382 static inline struct niter_desc *
383 simple_loop_desc (struct loop *loop)
385 return (struct niter_desc *) loop->aux;
388 /* Accessors for the loop structures. */
390 /* Returns the loop with index NUM from current_loops. */
392 static inline struct loop *
393 get_loop (unsigned num)
395 return VEC_index (loop_p, current_loops->larray, num);
398 /* Returns the list of loops in current_loops. */
400 static inline VEC (loop_p, heap) *
406 return current_loops->larray;
409 /* Returns the number of loops in current_loops (including the removed
410 ones and the fake loop that forms the root of the loop tree). */
412 static inline unsigned
413 number_of_loops (void)
418 return VEC_length (loop_p, current_loops->larray);
421 /* Loop iterators. */
423 /* Flags for loop iteration. */
427 LI_INCLUDE_ROOT = 1, /* Include the fake root of the loop tree. */
428 LI_FROM_INNERMOST = 2,/* Iterate over the loops in the reverse order,
429 starting from innermost ones. */
430 LI_ONLY_INNERMOST = 4,/* Iterate only over innermost loops. */
431 LI_ONLY_OLD = 8 /* Do not traverse the loops created during the
432 traversal (this is the default behavior with
433 LI_FROM_INNERMOST). */
436 /* The iterator for loops. */
440 int idx; /* Index of the actual loop. */
441 int end; /* Only loops before end should be traversed. */
445 fel_next (loop_iterator *li, loop_p *loop, unsigned flags)
447 if (flags & LI_FROM_INNERMOST)
450 for (; li->idx > li->end; li->idx--)
452 *loop = VEC_index (loop_p, current_loops->larray, li->idx);
454 && (!(flags & LI_ONLY_INNERMOST)
455 || (*loop)->inner == NULL))
461 if (!(flags & LI_ONLY_OLD))
462 li->end = number_of_loops ();
464 for (; li->idx < li->end; li->idx++)
466 *loop = VEC_index (loop_p, current_loops->larray, li->idx);
468 && (!(flags & LI_ONLY_INNERMOST)
469 || (*loop)->inner == NULL))
478 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
488 if (flags & LI_FROM_INNERMOST)
490 li->idx = number_of_loops ();
491 li->end = (flags & LI_INCLUDE_ROOT) ? -1 : 0;
495 li->idx = (flags & LI_INCLUDE_ROOT) ? -1 : 0;
496 li->end = number_of_loops ();
498 fel_next (li, loop, flags);
501 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
502 for (fel_init (&(LI), &(LOOP), FLAGS); \
504 fel_next (&(LI), &(LOOP), FLAGS))
506 /* The properties of the target. */
508 extern unsigned target_avail_regs; /* Number of available registers. */
509 extern unsigned target_res_regs; /* Number of reserved registers. */
510 extern unsigned target_small_cost; /* The cost for register when there
512 extern unsigned target_pres_cost; /* The cost for register when there are
513 not too many free ones. */
514 extern unsigned target_spill_cost; /* The cost for register when we need
517 /* Register pressure estimation for induction variable optimizations & loop
519 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
520 extern void init_set_costs (void);
522 /* Loop optimizer initialization. */
523 extern void loop_optimizer_init (unsigned);
524 extern void loop_optimizer_finalize (void);
526 /* Optimization passes. */
527 extern void unswitch_loops (void);
531 UAP_PEEL = 1, /* Enables loop peeling. */
532 UAP_UNROLL = 2, /* Enables unrolling of loops if it seems profitable. */
533 UAP_UNROLL_ALL = 4 /* Enables unrolling of all loops. */
536 extern void unroll_and_peel_loops (int);
537 extern void doloop_optimize_loops (void);
538 extern void move_loop_invariants (void);
540 #endif /* GCC_CFGLOOP_H */