1 /* Natural loop functions
2 Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
3 2005, 2006, 2007, 2008, 2009 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 3, 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 COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
24 #include "basic-block.h"
28 #include "double-int.h"
30 /* Structure to hold decision about unrolling/peeling. */
41 struct lpt_decision
GTY (())
43 enum lpt_dec decision
;
47 /* The structure describing a bound on number of iterations of a loop. */
49 struct nb_iter_bound
GTY ((chain_next ("%h.next")))
51 /* The statement STMT is executed at most ... */
54 /* ... BOUND + 1 times (BOUND must be an unsigned constant).
55 The + 1 is added for the following reasons:
57 a) 0 would otherwise be unused, while we would need to care more about
58 overflows (as MAX + 1 is sometimes produced as the estimate on number
59 of executions of STMT).
60 b) it is consistent with the result of number_of_iterations_exit. */
63 /* True if the statement will cause the loop to be leaved the (at most)
64 BOUND + 1-st time it is executed, that is, all the statements after it
65 are executed at most BOUND times. */
68 /* The next bound in the list. */
69 struct nb_iter_bound
*next
;
72 /* Description of the loop exit. */
74 struct loop_exit
GTY (())
79 /* Previous and next exit in the list of the exits of the loop. */
80 struct loop_exit
*prev
;
81 struct loop_exit
*next
;
83 /* Next element in the list of loops from that E exits. */
84 struct loop_exit
*next_e
;
87 typedef struct loop
*loop_p
;
89 DEF_VEC_ALLOC_P (loop_p
, heap
);
90 DEF_VEC_ALLOC_P (loop_p
, gc
);
92 /* An integer estimation of the number of iterations. Estimate_state
93 describes what is the state of the estimation. */
96 /* Estimate was not computed yet. */
98 /* Estimate is ready. */
102 /* Structure to hold information for each natural loop. */
103 struct loop
GTY ((chain_next ("%h.next")))
105 /* Index into loops array. */
108 /* Number of loop insns. */
111 /* Basic block of loop header. */
112 struct basic_block_def
*header
;
114 /* Basic block of loop latch. */
115 struct basic_block_def
*latch
;
117 /* For loop unrolling/peeling decision. */
118 struct lpt_decision lpt_decision
;
120 /* Average number of executed insns per iteration. */
123 /* Number of blocks contained within the loop. */
126 /* Superloops of the loop, starting with the outermost loop. */
127 VEC (loop_p
, gc
) *superloops
;
129 /* The first inner (child) loop or NULL if innermost loop. */
132 /* Link to the next (sibling) loop. */
135 /* Auxiliary info specific to a pass. */
136 PTR
GTY ((skip (""))) aux
;
138 /* The number of times the latch of the loop is executed.
139 This is an INTEGER_CST or an expression containing symbolic
140 names. Don't access this field directly:
141 number_of_latch_executions computes and caches the computed
142 information in this field. */
145 /* An integer guaranteed to bound the number of iterations of the loop
147 double_int nb_iterations_upper_bound
;
149 /* An integer giving the expected number of iterations of the loop. */
150 double_int nb_iterations_estimate
;
152 bool any_upper_bound
;
155 /* An integer estimation of the number of iterations. Estimate_state
156 describes what is the state of the estimation. */
157 enum loop_estimation estimate_state
;
159 /* Upper bound on number of iterations of a loop. */
160 struct nb_iter_bound
*bounds
;
162 /* Head of the cyclic list of the exits of the loop. */
163 struct loop_exit
*exits
;
166 /* Flags for state of loop structure. */
169 LOOPS_HAVE_PREHEADERS
= 1,
170 LOOPS_HAVE_SIMPLE_LATCHES
= 2,
171 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS
= 4,
172 LOOPS_HAVE_RECORDED_EXITS
= 8,
173 LOOPS_MAY_HAVE_MULTIPLE_LATCHES
= 16,
174 LOOP_CLOSED_SSA
= 32,
175 LOOPS_NEED_FIXUP
= 64,
176 LOOPS_HAVE_FALLTHRU_PREHEADERS
= 128
179 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
180 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
181 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
183 /* Structure to hold CFG information about natural loops within a function. */
184 struct loops
GTY (())
186 /* State of loops. */
189 /* Array of the loops. */
190 VEC (loop_p
, gc
) *larray
;
192 /* Maps edges to the list of their descriptions as loop exits. Edges
193 whose sources or destinations have loop_father == NULL (which may
194 happen during the cfg manipulations) should not appear in EXITS. */
195 htab_t
GTY((param_is (struct loop_exit
))) exits
;
197 /* Pointer to root of loop hierarchy tree. */
198 struct loop
*tree_root
;
201 /* Loop recognition. */
202 extern int flow_loops_find (struct loops
*);
203 extern void disambiguate_loops_with_multiple_latches (void);
204 extern void flow_loops_free (struct loops
*);
205 extern void flow_loops_dump (FILE *,
206 void (*)(const struct loop
*, FILE *, int), int);
207 extern void flow_loop_dump (const struct loop
*, FILE *,
208 void (*)(const struct loop
*, FILE *, int), int);
209 struct loop
*alloc_loop (void);
210 extern void flow_loop_free (struct loop
*);
211 int flow_loop_nodes_find (basic_block
, struct loop
*);
212 void fix_loop_structure (bitmap changed_bbs
);
213 void mark_irreducible_loops (void);
214 void release_recorded_exits (void);
215 void record_loop_exits (void);
216 void rescan_loop_exit (edge
, bool, bool);
218 /* Loop data structure manipulation/querying. */
219 extern void flow_loop_tree_node_add (struct loop
*, struct loop
*);
220 extern void flow_loop_tree_node_remove (struct loop
*);
221 extern void add_loop (struct loop
*, struct loop
*);
222 extern bool flow_loop_nested_p (const struct loop
*, const struct loop
*);
223 extern bool flow_bb_inside_loop_p (const struct loop
*, const_basic_block
);
224 extern struct loop
* find_common_loop (struct loop
*, struct loop
*);
225 struct loop
*superloop_at_depth (struct loop
*, unsigned);
226 struct eni_weights_d
;
227 extern unsigned tree_num_loop_insns (struct loop
*, struct eni_weights_d
*);
228 extern int num_loop_insns (const struct loop
*);
229 extern int average_num_loop_insns (const struct loop
*);
230 extern unsigned get_loop_level (const struct loop
*);
231 extern bool loop_exit_edge_p (const struct loop
*, const_edge
);
232 extern bool is_loop_exit (struct loop
*, basic_block
);
233 extern void mark_loop_exit_edges (void);
235 /* Loops & cfg manipulation. */
236 extern basic_block
*get_loop_body (const struct loop
*);
237 extern unsigned get_loop_body_with_size (const struct loop
*, basic_block
*,
239 extern basic_block
*get_loop_body_in_dom_order (const struct loop
*);
240 extern basic_block
*get_loop_body_in_bfs_order (const struct loop
*);
241 extern basic_block
*get_loop_body_in_custom_order (const struct loop
*,
242 int (*) (const void *, const void *));
244 extern VEC (edge
, heap
) *get_loop_exit_edges (const struct loop
*);
245 edge
single_exit (const struct loop
*);
246 extern unsigned num_loop_branches (const struct loop
*);
248 extern edge
loop_preheader_edge (const struct loop
*);
249 extern edge
loop_latch_edge (const struct loop
*);
251 extern void add_bb_to_loop (basic_block
, struct loop
*);
252 extern void remove_bb_from_loops (basic_block
);
254 extern void cancel_loop_tree (struct loop
*);
255 extern void delete_loop (struct loop
*);
259 CP_SIMPLE_PREHEADERS
= 1,
260 CP_FALLTHRU_PREHEADERS
= 2
263 basic_block
create_preheader (struct loop
*, int);
264 extern void create_preheaders (int);
265 extern void force_single_succ_latches (void);
267 extern void verify_loop_structure (void);
270 extern bool just_once_each_iteration_p (const struct loop
*, const_basic_block
);
271 gcov_type
expected_loop_iterations_unbounded (const struct loop
*);
272 extern unsigned expected_loop_iterations (const struct loop
*);
273 extern rtx
doloop_condition_get (rtx
);
275 void estimate_numbers_of_iterations_loop (struct loop
*);
276 HOST_WIDE_INT
estimated_loop_iterations_int (struct loop
*, bool);
277 bool estimated_loop_iterations (struct loop
*, bool, double_int
*);
279 /* Loop manipulation. */
280 extern bool can_duplicate_loop_p (const struct loop
*loop
);
282 #define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in
283 duplicate_loop_to_header_edge. */
284 #define DLTHE_RECORD_COPY_NUMBER 2 /* Record copy number in the aux
285 field of newly create BB. */
286 #define DLTHE_FLAG_COMPLETTE_PEEL 4 /* Update frequencies expecting
287 a complete peeling. */
289 extern edge
create_empty_if_region_on_edge (edge
, tree
);
290 extern struct loop
*create_empty_loop_on_edge (edge
, tree
, tree
, tree
, tree
,
291 tree
*, struct loop
*);
292 extern struct loop
* duplicate_loop (struct loop
*, struct loop
*);
293 extern bool duplicate_loop_to_header_edge (struct loop
*, edge
,
294 unsigned, sbitmap
, edge
,
295 VEC (edge
, heap
) **, int);
296 extern struct loop
*loopify (edge
, edge
,
297 basic_block
, edge
, edge
, bool,
299 struct loop
* loop_version (struct loop
*, void *,
300 basic_block
*, unsigned, unsigned, unsigned, bool);
301 extern bool remove_path (edge
);
302 void scale_loop_frequencies (struct loop
*, int, int);
304 /* Induction variable analysis. */
306 /* The description of induction variable. The things are a bit complicated
307 due to need to handle subregs and extends. The value of the object described
308 by it can be obtained as follows (all computations are done in extend_mode):
310 Value in i-th iteration is
311 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
313 If first_special is true, the value in the first iteration is
316 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
317 subreg_{mode} (base + i * step)
319 The get_iv_value function can be used to obtain these expressions.
321 ??? Add a third mode field that would specify the mode in that inner
322 computation is done, which would enable it to be different from the
327 /* Its base and step (mode of base and step is supposed to be extend_mode,
328 see the description above). */
331 /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN). */
332 enum rtx_code extend
;
334 /* Operations applied in the extended mode. */
337 /* The mode it is extended to. */
338 enum machine_mode extend_mode
;
340 /* The mode the variable iterates in. */
341 enum machine_mode mode
;
343 /* Whether the first iteration needs to be handled specially. */
344 unsigned first_special
: 1;
347 /* The description of an exit from the loop and of the number of iterations
348 till we take the exit. */
352 /* The edge out of the loop. */
355 /* The other edge leading from the condition. */
358 /* True if we are able to say anything about number of iterations of the
362 /* True if the loop iterates the constant number of times. */
365 /* Number of iterations if constant. */
366 unsigned HOST_WIDEST_INT niter
;
368 /* Upper bound on the number of iterations. */
369 unsigned HOST_WIDEST_INT niter_max
;
371 /* Assumptions under that the rest of the information is valid. */
374 /* Assumptions under that the loop ends before reaching the latch,
375 even if value of niter_expr says otherwise. */
376 rtx noloop_assumptions
;
378 /* Condition under that the loop is infinite. */
381 /* Whether the comparison is signed. */
384 /* The mode in that niter_expr should be computed. */
385 enum machine_mode mode
;
387 /* The number of iterations of the loop. */
391 extern void iv_analysis_loop_init (struct loop
*);
392 extern bool iv_analyze (rtx
, rtx
, struct rtx_iv
*);
393 extern bool iv_analyze_result (rtx
, rtx
, struct rtx_iv
*);
394 extern bool iv_analyze_expr (rtx
, rtx
, enum machine_mode
, struct rtx_iv
*);
395 extern rtx
get_iv_value (struct rtx_iv
*, rtx
);
396 extern bool biv_p (rtx
, rtx
);
397 extern void find_simple_exit (struct loop
*, struct niter_desc
*);
398 extern void iv_analysis_done (void);
400 extern struct niter_desc
*get_simple_loop_desc (struct loop
*loop
);
401 extern void free_simple_loop_desc (struct loop
*loop
);
403 static inline struct niter_desc
*
404 simple_loop_desc (struct loop
*loop
)
406 return (struct niter_desc
*) loop
->aux
;
409 /* Accessors for the loop structures. */
411 /* Returns the loop with index NUM from current_loops. */
413 static inline struct loop
*
414 get_loop (unsigned num
)
416 return VEC_index (loop_p
, current_loops
->larray
, num
);
419 /* Returns the number of superloops of LOOP. */
421 static inline unsigned
422 loop_depth (const struct loop
*loop
)
424 return VEC_length (loop_p
, loop
->superloops
);
427 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
430 static inline struct loop
*
431 loop_outer (const struct loop
*loop
)
433 unsigned n
= VEC_length (loop_p
, loop
->superloops
);
438 return VEC_index (loop_p
, loop
->superloops
, n
- 1);
441 /* Returns the list of loops in current_loops. */
443 static inline VEC (loop_p
, gc
) *
449 return current_loops
->larray
;
452 /* Returns the number of loops in current_loops (including the removed
453 ones and the fake loop that forms the root of the loop tree). */
455 static inline unsigned
456 number_of_loops (void)
461 return VEC_length (loop_p
, current_loops
->larray
);
464 /* Returns true if state of the loops satisfies all properties
465 described by FLAGS. */
468 loops_state_satisfies_p (unsigned flags
)
470 return (current_loops
->state
& flags
) == flags
;
473 /* Sets FLAGS to the loops state. */
476 loops_state_set (unsigned flags
)
478 current_loops
->state
|= flags
;
481 /* Clears FLAGS from the loops state. */
484 loops_state_clear (unsigned flags
)
488 current_loops
->state
&= ~flags
;
491 /* Loop iterators. */
493 /* Flags for loop iteration. */
497 LI_INCLUDE_ROOT
= 1, /* Include the fake root of the loop tree. */
498 LI_FROM_INNERMOST
= 2, /* Iterate over the loops in the reverse order,
499 starting from innermost ones. */
500 LI_ONLY_INNERMOST
= 4 /* Iterate only over innermost loops. */
503 /* The iterator for loops. */
507 /* The list of loops to visit. */
508 VEC(int,heap
) *to_visit
;
510 /* The index of the actual loop. */
515 fel_next (loop_iterator
*li
, loop_p
*loop
)
519 while (VEC_iterate (int, li
->to_visit
, li
->idx
, anum
))
522 *loop
= get_loop (anum
);
527 VEC_free (int, heap
, li
->to_visit
);
532 fel_init (loop_iterator
*li
, loop_p
*loop
, unsigned flags
)
546 li
->to_visit
= VEC_alloc (int, heap
, number_of_loops ());
547 mn
= (flags
& LI_INCLUDE_ROOT
) ? 0 : 1;
549 if (flags
& LI_ONLY_INNERMOST
)
551 for (i
= 0; VEC_iterate (loop_p
, current_loops
->larray
, i
, aloop
); i
++)
553 && aloop
->inner
== NULL
555 VEC_quick_push (int, li
->to_visit
, aloop
->num
);
557 else if (flags
& LI_FROM_INNERMOST
)
559 /* Push the loops to LI->TO_VISIT in postorder. */
560 for (aloop
= current_loops
->tree_root
;
561 aloop
->inner
!= NULL
;
562 aloop
= aloop
->inner
)
567 if (aloop
->num
>= mn
)
568 VEC_quick_push (int, li
->to_visit
, aloop
->num
);
572 for (aloop
= aloop
->next
;
573 aloop
->inner
!= NULL
;
574 aloop
= aloop
->inner
)
577 else if (!loop_outer (aloop
))
580 aloop
= loop_outer (aloop
);
585 /* Push the loops to LI->TO_VISIT in preorder. */
586 aloop
= current_loops
->tree_root
;
589 if (aloop
->num
>= mn
)
590 VEC_quick_push (int, li
->to_visit
, aloop
->num
);
592 if (aloop
->inner
!= NULL
)
593 aloop
= aloop
->inner
;
596 while (aloop
!= NULL
&& aloop
->next
== NULL
)
597 aloop
= loop_outer (aloop
);
608 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
609 for (fel_init (&(LI), &(LOOP), FLAGS); \
611 fel_next (&(LI), &(LOOP)))
613 #define FOR_EACH_LOOP_BREAK(LI) \
615 VEC_free (int, heap, (LI)->to_visit); \
619 /* The properties of the target. */
621 extern unsigned target_avail_regs
;
622 extern unsigned target_res_regs
;
623 extern unsigned target_reg_cost
[2];
624 extern unsigned target_spill_cost
[2];
626 /* Register pressure estimation for induction variable optimizations & loop
628 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool);
629 extern void init_set_costs (void);
631 /* Loop optimizer initialization. */
632 extern void loop_optimizer_init (unsigned);
633 extern void loop_optimizer_finalize (void);
635 /* Optimization passes. */
636 extern void unswitch_loops (void);
640 UAP_PEEL
= 1, /* Enables loop peeling. */
641 UAP_UNROLL
= 2, /* Enables unrolling of loops if it seems profitable. */
642 UAP_UNROLL_ALL
= 4 /* Enables unrolling of all loops. */
645 extern void unroll_and_peel_loops (int);
646 extern void doloop_optimize_loops (void);
647 extern void move_loop_invariants (void);
649 #endif /* GCC_CFGLOOP_H */