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 #include "double-int.h"
31 /* Structure to hold decision about unrolling/peeling. */
44 enum lpt_dec decision;
48 /* The structure describing a bound on number of iterations of a loop. */
52 /* The statement STMT is executed at most ... */
55 /* ... BOUND + 1 times (BOUND must be an unsigned constant).
56 The + 1 is added for the following reasons:
58 a) 0 would otherwise be unused, while we would need to care more about
59 overflows (as MAX + 1 is sometimes produced as the estimate on number
60 of executions of STMT).
61 b) it is consistent with the result of number_of_iterations_exit. */
64 /* True if the statement will cause the loop to be leaved the (at most)
65 BOUND + 1-st time it is executed, that is, all the statements after it
66 are executed at most BOUND times. */
69 /* The next bound in the list. */
70 struct nb_iter_bound *next;
73 /* Description of the loop exit. */
80 /* Previous and next exit in the list of the exits of the loop. */
81 struct loop_exit *prev;
82 struct loop_exit *next;
84 /* Next element in the list of loops from that E exits. */
85 struct loop_exit *next_e;
88 typedef struct loop *loop_p;
90 DEF_VEC_ALLOC_P (loop_p, heap);
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 /* Superloops of the loop, starting with the outermost loop. */
117 VEC (loop_p, heap) *superloops;
119 /* The first inner (child) loop or NULL if innermost loop. */
122 /* Link to the next (sibling) loop. */
125 /* Loop that is copy of this loop. */
128 /* Auxiliary info specific to a pass. */
131 /* The number of times the latch of the loop is executed.
132 This is an INTEGER_CST or an expression containing symbolic
133 names. Don't access this field directly:
134 number_of_latch_executions computes and caches the computed
135 information in this field. */
138 /* An integer estimation of the number of iterations. Estimate_state
139 describes what is the state of the estimation. */
142 /* Estimate was not computed yet. */
144 /* Estimate is ready. */
148 /* An integer guaranteed to bound the number of iterations of the loop
150 bool any_upper_bound;
151 double_int nb_iterations_upper_bound;
153 /* An integer giving the expected number of iterations of the loop. */
155 double_int nb_iterations_estimate;
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,
171 LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16,
175 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
176 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
177 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
179 /* Structure to hold CFG information about natural loops within a function. */
182 /* State of loops. */
185 /* Array of the loops. */
186 VEC (loop_p, heap) *larray;
188 /* Maps edges to the list of their descriptions as loop exits. Edges
189 whose sources or destinations have loop_father == NULL (which may
190 happen during the cfg manipulations) should not appear in EXITS. */
193 /* Pointer to root of loop hierarchy tree. */
194 struct loop *tree_root;
197 /* Loop recognition. */
198 extern int flow_loops_find (struct loops *);
199 extern void disambiguate_loops_with_multiple_latches (void);
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 void add_loop (struct loop *, struct loop *);
218 extern bool flow_loop_nested_p (const struct loop *, const struct loop *);
219 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
220 extern struct loop * find_common_loop (struct loop *, struct loop *);
221 struct loop *superloop_at_depth (struct loop *, unsigned);
222 struct eni_weights_d;
223 extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *);
224 extern int num_loop_insns (struct loop *);
225 extern int average_num_loop_insns (struct loop *);
226 extern unsigned get_loop_level (const struct loop *);
227 extern bool loop_exit_edge_p (const struct loop *, edge);
228 extern void mark_loop_exit_edges (void);
230 /* Loops & cfg manipulation. */
231 extern basic_block *get_loop_body (const struct loop *);
232 extern unsigned get_loop_body_with_size (const struct loop *, basic_block *,
234 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
235 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
236 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
237 edge single_exit (const struct loop *);
238 extern unsigned num_loop_branches (const struct loop *);
240 extern edge loop_preheader_edge (const struct loop *);
241 extern edge loop_latch_edge (const struct loop *);
243 extern void add_bb_to_loop (basic_block, struct loop *);
244 extern void remove_bb_from_loops (basic_block);
246 extern void cancel_loop_tree (struct loop *);
247 extern void delete_loop (struct loop *);
251 CP_SIMPLE_PREHEADERS = 1
254 extern void create_preheaders (int);
255 extern void force_single_succ_latches (void);
257 extern void verify_loop_structure (void);
260 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
261 gcov_type expected_loop_iterations_unbounded (const struct loop *);
262 extern unsigned expected_loop_iterations (const struct loop *);
263 extern rtx doloop_condition_get (rtx);
265 void estimate_numbers_of_iterations_loop (struct loop *);
266 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool);
267 bool estimated_loop_iterations (struct loop *, bool, double_int *);
269 /* Loop manipulation. */
270 extern bool can_duplicate_loop_p (struct loop *loop);
272 #define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in
273 duplicate_loop_to_header_edge. */
274 #define DLTHE_RECORD_COPY_NUMBER 2 /* Record copy number in the aux
275 field of newly create BB. */
276 #define DLTHE_FLAG_COMPLETTE_PEEL 4 /* Update frequencies expecting
277 a complete peeling. */
279 extern struct loop * duplicate_loop (struct loop *, struct loop *);
280 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
281 unsigned, sbitmap, edge,
282 VEC (edge, heap) **, int);
283 extern struct loop *loopify (edge, edge,
284 basic_block, edge, edge, bool,
286 struct loop * loop_version (struct loop *, void *,
287 basic_block *, unsigned, unsigned, unsigned, bool);
288 extern bool remove_path (edge);
289 void scale_loop_frequencies (struct loop *, int, int);
291 /* Induction variable analysis. */
293 /* The description of induction variable. The things are a bit complicated
294 due to need to handle subregs and extends. The value of the object described
295 by it can be obtained as follows (all computations are done in extend_mode):
297 Value in i-th iteration is
298 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
300 If first_special is true, the value in the first iteration is
303 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
304 subreg_{mode} (base + i * step)
306 The get_iv_value function can be used to obtain these expressions.
308 ??? Add a third mode field that would specify the mode in that inner
309 computation is done, which would enable it to be different from the
314 /* Its base and step (mode of base and step is supposed to be extend_mode,
315 see the description above). */
318 /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN). */
319 enum rtx_code extend;
321 /* Operations applied in the extended mode. */
324 /* The mode it is extended to. */
325 enum machine_mode extend_mode;
327 /* The mode the variable iterates in. */
328 enum machine_mode mode;
330 /* Whether the first iteration needs to be handled specially. */
331 unsigned first_special : 1;
334 /* The description of an exit from the loop and of the number of iterations
335 till we take the exit. */
339 /* The edge out of the loop. */
342 /* The other edge leading from the condition. */
345 /* True if we are able to say anything about number of iterations of the
349 /* True if the loop iterates the constant number of times. */
352 /* Number of iterations if constant. */
353 unsigned HOST_WIDEST_INT niter;
355 /* Upper bound on the number of iterations. */
356 unsigned HOST_WIDEST_INT niter_max;
358 /* Assumptions under that the rest of the information is valid. */
361 /* Assumptions under that the loop ends before reaching the latch,
362 even if value of niter_expr says otherwise. */
363 rtx noloop_assumptions;
365 /* Condition under that the loop is infinite. */
368 /* Whether the comparison is signed. */
371 /* The mode in that niter_expr should be computed. */
372 enum machine_mode mode;
374 /* The number of iterations of the loop. */
378 extern void iv_analysis_loop_init (struct loop *);
379 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
380 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
381 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
382 extern rtx get_iv_value (struct rtx_iv *, rtx);
383 extern bool biv_p (rtx, rtx);
384 extern void find_simple_exit (struct loop *, struct niter_desc *);
385 extern void iv_analysis_done (void);
386 extern struct df *iv_current_loop_df (void);
388 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
389 extern void free_simple_loop_desc (struct loop *loop);
391 static inline struct niter_desc *
392 simple_loop_desc (struct loop *loop)
394 return (struct niter_desc *) loop->aux;
397 /* Accessors for the loop structures. */
399 /* Returns the loop with index NUM from current_loops. */
401 static inline struct loop *
402 get_loop (unsigned num)
404 return VEC_index (loop_p, current_loops->larray, num);
407 /* Returns the number of superloops of LOOP. */
409 static inline unsigned
410 loop_depth (const struct loop *loop)
412 return VEC_length (loop_p, loop->superloops);
415 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
418 static inline struct loop *
419 loop_outer (const struct loop *loop)
421 unsigned n = VEC_length (loop_p, loop->superloops);
426 return VEC_index (loop_p, loop->superloops, n - 1);
429 /* Returns the list of loops in current_loops. */
431 static inline VEC (loop_p, heap) *
437 return current_loops->larray;
440 /* Returns the number of loops in current_loops (including the removed
441 ones and the fake loop that forms the root of the loop tree). */
443 static inline unsigned
444 number_of_loops (void)
449 return VEC_length (loop_p, current_loops->larray);
452 /* Loop iterators. */
454 /* Flags for loop iteration. */
458 LI_INCLUDE_ROOT = 1, /* Include the fake root of the loop tree. */
459 LI_FROM_INNERMOST = 2, /* Iterate over the loops in the reverse order,
460 starting from innermost ones. */
461 LI_ONLY_INNERMOST = 4 /* Iterate only over innermost loops. */
464 /* The iterator for loops. */
468 /* The list of loops to visit. */
469 VEC(int,heap) *to_visit;
471 /* The index of the actual loop. */
476 fel_next (loop_iterator *li, loop_p *loop)
480 while (VEC_iterate (int, li->to_visit, li->idx, anum))
483 *loop = get_loop (anum);
488 VEC_free (int, heap, li->to_visit);
493 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
507 li->to_visit = VEC_alloc (int, heap, number_of_loops ());
508 mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
510 if (flags & LI_ONLY_INNERMOST)
512 for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
514 && aloop->inner == NULL
516 VEC_quick_push (int, li->to_visit, aloop->num);
518 else if (flags & LI_FROM_INNERMOST)
520 /* Push the loops to LI->TO_VISIT in postorder. */
521 for (aloop = current_loops->tree_root;
522 aloop->inner != NULL;
523 aloop = aloop->inner)
528 if (aloop->num >= mn)
529 VEC_quick_push (int, li->to_visit, aloop->num);
533 for (aloop = aloop->next;
534 aloop->inner != NULL;
535 aloop = aloop->inner)
538 else if (!loop_outer (aloop))
541 aloop = loop_outer (aloop);
546 /* Push the loops to LI->TO_VISIT in preorder. */
547 aloop = current_loops->tree_root;
550 if (aloop->num >= mn)
551 VEC_quick_push (int, li->to_visit, aloop->num);
553 if (aloop->inner != NULL)
554 aloop = aloop->inner;
557 while (aloop != NULL && aloop->next == NULL)
558 aloop = loop_outer (aloop);
569 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
570 for (fel_init (&(LI), &(LOOP), FLAGS); \
572 fel_next (&(LI), &(LOOP)))
574 #define FOR_EACH_LOOP_BREAK(LI) \
576 VEC_free (int, heap, (LI)->to_visit); \
580 /* The properties of the target. */
582 extern unsigned target_avail_regs;
583 extern unsigned target_res_regs;
584 extern unsigned target_reg_cost;
585 extern unsigned target_spill_cost;
587 /* Register pressure estimation for induction variable optimizations & loop
589 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned);
590 extern void init_set_costs (void);
592 /* Loop optimizer initialization. */
593 extern void loop_optimizer_init (unsigned);
594 extern void loop_optimizer_finalize (void);
596 /* Optimization passes. */
597 extern void unswitch_loops (void);
601 UAP_PEEL = 1, /* Enables loop peeling. */
602 UAP_UNROLL = 2, /* Enables unrolling of loops if it seems profitable. */
603 UAP_UNROLL_ALL = 4 /* Enables unrolling of all loops. */
606 extern void unroll_and_peel_loops (int);
607 extern void doloop_optimize_loops (void);
608 extern void move_loop_invariants (void);
610 #endif /* GCC_CFGLOOP_H */