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"
33 /* Structure to hold decision about unrolling/peeling. */
44 struct GTY (()) lpt_decision
{
45 enum lpt_dec decision
;
49 /* The structure describing a bound on number of iterations of a loop. */
51 struct GTY ((chain_next ("%h.next"))) nb_iter_bound
{
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. */
75 struct GTY (()) loop_exit
{
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 GTY ((chain_next ("%h.next"))) loop
{
104 /* Index into loops array. */
107 /* Number of loop insns. */
110 /* Basic block of loop header. */
111 struct basic_block_def
*header
;
113 /* Basic block of loop latch. */
114 struct basic_block_def
*latch
;
116 /* For loop unrolling/peeling decision. */
117 struct lpt_decision lpt_decision
;
119 /* Average number of executed insns per iteration. */
122 /* Number of blocks contained within the loop. */
125 /* Superloops of the loop, starting with the outermost loop. */
126 VEC (loop_p
, gc
) *superloops
;
128 /* The first inner (child) loop or NULL if innermost loop. */
131 /* Link to the next (sibling) loop. */
134 /* Auxiliary info specific to a pass. */
135 PTR
GTY ((skip (""))) aux
;
137 /* The number of times the latch of the loop is executed. This can be an
138 INTEGER_CST, or a symbolic expression representing the number of
139 iterations like "N - 1", or a COND_EXPR containing the runtime
140 conditions under which the number of iterations is non zero.
142 Don't access this field directly: number_of_latch_executions
143 computes and caches the computed information in this field. */
146 /* An integer guaranteed to bound the number of iterations of the loop
148 double_int nb_iterations_upper_bound
;
150 /* An integer giving the expected number of iterations of the loop. */
151 double_int nb_iterations_estimate
;
153 bool any_upper_bound
;
156 /* True if the loop can be parallel. */
157 bool can_be_parallel
;
159 /* An integer estimation of the number of iterations. Estimate_state
160 describes what is the state of the estimation. */
161 enum loop_estimation estimate_state
;
163 /* Upper bound on number of iterations of a loop. */
164 struct nb_iter_bound
*bounds
;
166 /* Head of the cyclic list of the exits of the loop. */
167 struct loop_exit
*exits
;
170 /* Flags for state of loop structure. */
173 LOOPS_HAVE_PREHEADERS
= 1,
174 LOOPS_HAVE_SIMPLE_LATCHES
= 2,
175 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS
= 4,
176 LOOPS_HAVE_RECORDED_EXITS
= 8,
177 LOOPS_MAY_HAVE_MULTIPLE_LATCHES
= 16,
178 LOOP_CLOSED_SSA
= 32,
179 LOOPS_NEED_FIXUP
= 64,
180 LOOPS_HAVE_FALLTHRU_PREHEADERS
= 128
183 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
184 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
185 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
187 /* Structure to hold CFG information about natural loops within a function. */
188 struct GTY (()) loops
{
189 /* State of loops. */
192 /* Array of the loops. */
193 VEC (loop_p
, gc
) *larray
;
195 /* Maps edges to the list of their descriptions as loop exits. Edges
196 whose sources or destinations have loop_father == NULL (which may
197 happen during the cfg manipulations) should not appear in EXITS. */
198 htab_t
GTY((param_is (struct loop_exit
))) exits
;
200 /* Pointer to root of loop hierarchy tree. */
201 struct loop
*tree_root
;
204 /* Loop recognition. */
205 extern int flow_loops_find (struct loops
*);
206 extern void disambiguate_loops_with_multiple_latches (void);
207 extern void flow_loops_free (struct loops
*);
208 extern void flow_loops_dump (FILE *,
209 void (*)(const struct loop
*, FILE *, int), int);
210 extern void flow_loop_dump (const struct loop
*, FILE *,
211 void (*)(const struct loop
*, FILE *, int), int);
212 struct loop
*alloc_loop (void);
213 extern void flow_loop_free (struct loop
*);
214 int flow_loop_nodes_find (basic_block
, struct loop
*);
215 void fix_loop_structure (bitmap changed_bbs
);
216 bool mark_irreducible_loops (void);
217 void release_recorded_exits (void);
218 void record_loop_exits (void);
219 void rescan_loop_exit (edge
, bool, bool);
221 /* Loop data structure manipulation/querying. */
222 extern void flow_loop_tree_node_add (struct loop
*, struct loop
*);
223 extern void flow_loop_tree_node_remove (struct loop
*);
224 extern void add_loop (struct loop
*, struct loop
*);
225 extern bool flow_loop_nested_p (const struct loop
*, const struct loop
*);
226 extern bool flow_bb_inside_loop_p (const struct loop
*, const_basic_block
);
227 extern struct loop
* find_common_loop (struct loop
*, struct loop
*);
228 struct loop
*superloop_at_depth (struct loop
*, unsigned);
229 struct eni_weights_d
;
230 extern unsigned tree_num_loop_insns (struct loop
*, struct eni_weights_d
*);
231 extern int num_loop_insns (const struct loop
*);
232 extern int average_num_loop_insns (const struct loop
*);
233 extern unsigned get_loop_level (const struct loop
*);
234 extern bool loop_exit_edge_p (const struct loop
*, const_edge
);
235 extern bool is_loop_exit (struct loop
*, basic_block
);
236 extern void mark_loop_exit_edges (void);
238 /* Loops & cfg manipulation. */
239 extern basic_block
*get_loop_body (const struct loop
*);
240 extern unsigned get_loop_body_with_size (const struct loop
*, basic_block
*,
242 extern basic_block
*get_loop_body_in_dom_order (const struct loop
*);
243 extern basic_block
*get_loop_body_in_bfs_order (const struct loop
*);
244 extern basic_block
*get_loop_body_in_custom_order (const struct loop
*,
245 int (*) (const void *, const void *));
247 extern VEC (edge
, heap
) *get_loop_exit_edges (const struct loop
*);
248 edge
single_exit (const struct loop
*);
249 extern unsigned num_loop_branches (const struct loop
*);
251 extern edge
loop_preheader_edge (const struct loop
*);
252 extern edge
loop_latch_edge (const struct loop
*);
254 extern void add_bb_to_loop (basic_block
, struct loop
*);
255 extern void remove_bb_from_loops (basic_block
);
257 extern void cancel_loop_tree (struct loop
*);
258 extern void delete_loop (struct loop
*);
262 CP_SIMPLE_PREHEADERS
= 1,
263 CP_FALLTHRU_PREHEADERS
= 2
266 basic_block
create_preheader (struct loop
*, int);
267 extern void create_preheaders (int);
268 extern void force_single_succ_latches (void);
270 extern void verify_loop_structure (void);
273 extern bool just_once_each_iteration_p (const struct loop
*, const_basic_block
);
274 gcov_type
expected_loop_iterations_unbounded (const struct loop
*);
275 extern unsigned expected_loop_iterations (const struct loop
*);
276 extern rtx
doloop_condition_get (rtx
);
278 void estimate_numbers_of_iterations_loop (struct loop
*);
279 HOST_WIDE_INT
estimated_loop_iterations_int (struct loop
*, bool);
280 bool estimated_loop_iterations (struct loop
*, bool, double_int
*);
282 /* Loop manipulation. */
283 extern bool can_duplicate_loop_p (const struct loop
*loop
);
285 #define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in
286 duplicate_loop_to_header_edge. */
287 #define DLTHE_RECORD_COPY_NUMBER 2 /* Record copy number in the aux
288 field of newly create BB. */
289 #define DLTHE_FLAG_COMPLETTE_PEEL 4 /* Update frequencies expecting
290 a complete peeling. */
292 extern edge
create_empty_if_region_on_edge (edge
, tree
);
293 extern struct loop
*create_empty_loop_on_edge (edge
, tree
, tree
, tree
, tree
,
294 tree
*, tree
*, struct loop
*);
295 extern struct loop
* duplicate_loop (struct loop
*, struct loop
*);
296 extern void duplicate_subloops (struct loop
*, struct loop
*);
297 extern bool duplicate_loop_to_header_edge (struct loop
*, edge
,
298 unsigned, sbitmap
, edge
,
299 VEC (edge
, heap
) **, int);
300 extern struct loop
*loopify (edge
, edge
,
301 basic_block
, edge
, edge
, bool,
303 struct loop
* loop_version (struct loop
*, void *,
304 basic_block
*, unsigned, unsigned, unsigned, bool);
305 extern bool remove_path (edge
);
306 void scale_loop_frequencies (struct loop
*, int, int);
308 /* Induction variable analysis. */
310 /* The description of induction variable. The things are a bit complicated
311 due to need to handle subregs and extends. The value of the object described
312 by it can be obtained as follows (all computations are done in extend_mode):
314 Value in i-th iteration is
315 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
317 If first_special is true, the value in the first iteration is
320 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
321 subreg_{mode} (base + i * step)
323 The get_iv_value function can be used to obtain these expressions.
325 ??? Add a third mode field that would specify the mode in that inner
326 computation is done, which would enable it to be different from the
331 /* Its base and step (mode of base and step is supposed to be extend_mode,
332 see the description above). */
335 /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN). */
336 enum rtx_code extend
;
338 /* Operations applied in the extended mode. */
341 /* The mode it is extended to. */
342 enum machine_mode extend_mode
;
344 /* The mode the variable iterates in. */
345 enum machine_mode mode
;
347 /* Whether the first iteration needs to be handled specially. */
348 unsigned first_special
: 1;
351 /* The description of an exit from the loop and of the number of iterations
352 till we take the exit. */
356 /* The edge out of the loop. */
359 /* The other edge leading from the condition. */
362 /* True if we are able to say anything about number of iterations of the
366 /* True if the loop iterates the constant number of times. */
369 /* Number of iterations if constant. */
370 unsigned HOST_WIDEST_INT niter
;
372 /* Upper bound on the number of iterations. */
373 unsigned HOST_WIDEST_INT niter_max
;
375 /* Assumptions under that the rest of the information is valid. */
378 /* Assumptions under that the loop ends before reaching the latch,
379 even if value of niter_expr says otherwise. */
380 rtx noloop_assumptions
;
382 /* Condition under that the loop is infinite. */
385 /* Whether the comparison is signed. */
388 /* The mode in that niter_expr should be computed. */
389 enum machine_mode mode
;
391 /* The number of iterations of the loop. */
395 extern void iv_analysis_loop_init (struct loop
*);
396 extern bool iv_analyze (rtx
, rtx
, struct rtx_iv
*);
397 extern bool iv_analyze_result (rtx
, rtx
, struct rtx_iv
*);
398 extern bool iv_analyze_expr (rtx
, rtx
, enum machine_mode
, struct rtx_iv
*);
399 extern rtx
get_iv_value (struct rtx_iv
*, rtx
);
400 extern bool biv_p (rtx
, rtx
);
401 extern void find_simple_exit (struct loop
*, struct niter_desc
*);
402 extern void iv_analysis_done (void);
404 extern struct niter_desc
*get_simple_loop_desc (struct loop
*loop
);
405 extern void free_simple_loop_desc (struct loop
*loop
);
407 static inline struct niter_desc
*
408 simple_loop_desc (struct loop
*loop
)
410 return (struct niter_desc
*) loop
->aux
;
413 /* Accessors for the loop structures. */
415 /* Returns the loop with index NUM from current_loops. */
417 static inline struct loop
*
418 get_loop (unsigned num
)
420 return VEC_index (loop_p
, current_loops
->larray
, num
);
423 /* Returns the number of superloops of LOOP. */
425 static inline unsigned
426 loop_depth (const struct loop
*loop
)
428 return VEC_length (loop_p
, loop
->superloops
);
431 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
434 static inline struct loop
*
435 loop_outer (const struct loop
*loop
)
437 unsigned n
= VEC_length (loop_p
, loop
->superloops
);
442 return VEC_index (loop_p
, loop
->superloops
, n
- 1);
445 /* Returns the list of loops in current_loops. */
447 static inline VEC (loop_p
, gc
) *
453 return current_loops
->larray
;
456 /* Returns the number of loops in current_loops (including the removed
457 ones and the fake loop that forms the root of the loop tree). */
459 static inline unsigned
460 number_of_loops (void)
465 return VEC_length (loop_p
, current_loops
->larray
);
468 /* Returns true if state of the loops satisfies all properties
469 described by FLAGS. */
472 loops_state_satisfies_p (unsigned flags
)
474 return (current_loops
->state
& flags
) == flags
;
477 /* Sets FLAGS to the loops state. */
480 loops_state_set (unsigned flags
)
482 current_loops
->state
|= flags
;
485 /* Clears FLAGS from the loops state. */
488 loops_state_clear (unsigned flags
)
492 current_loops
->state
&= ~flags
;
495 /* Loop iterators. */
497 /* Flags for loop iteration. */
501 LI_INCLUDE_ROOT
= 1, /* Include the fake root of the loop tree. */
502 LI_FROM_INNERMOST
= 2, /* Iterate over the loops in the reverse order,
503 starting from innermost ones. */
504 LI_ONLY_INNERMOST
= 4 /* Iterate only over innermost loops. */
507 /* The iterator for loops. */
511 /* The list of loops to visit. */
512 VEC(int,heap
) *to_visit
;
514 /* The index of the actual loop. */
519 fel_next (loop_iterator
*li
, loop_p
*loop
)
523 while (VEC_iterate (int, li
->to_visit
, li
->idx
, anum
))
526 *loop
= get_loop (anum
);
531 VEC_free (int, heap
, li
->to_visit
);
536 fel_init (loop_iterator
*li
, loop_p
*loop
, unsigned flags
)
550 li
->to_visit
= VEC_alloc (int, heap
, number_of_loops ());
551 mn
= (flags
& LI_INCLUDE_ROOT
) ? 0 : 1;
553 if (flags
& LI_ONLY_INNERMOST
)
555 for (i
= 0; VEC_iterate (loop_p
, current_loops
->larray
, i
, aloop
); i
++)
557 && aloop
->inner
== NULL
559 VEC_quick_push (int, li
->to_visit
, aloop
->num
);
561 else if (flags
& LI_FROM_INNERMOST
)
563 /* Push the loops to LI->TO_VISIT in postorder. */
564 for (aloop
= current_loops
->tree_root
;
565 aloop
->inner
!= NULL
;
566 aloop
= aloop
->inner
)
571 if (aloop
->num
>= mn
)
572 VEC_quick_push (int, li
->to_visit
, aloop
->num
);
576 for (aloop
= aloop
->next
;
577 aloop
->inner
!= NULL
;
578 aloop
= aloop
->inner
)
581 else if (!loop_outer (aloop
))
584 aloop
= loop_outer (aloop
);
589 /* Push the loops to LI->TO_VISIT in preorder. */
590 aloop
= current_loops
->tree_root
;
593 if (aloop
->num
>= mn
)
594 VEC_quick_push (int, li
->to_visit
, aloop
->num
);
596 if (aloop
->inner
!= NULL
)
597 aloop
= aloop
->inner
;
600 while (aloop
!= NULL
&& aloop
->next
== NULL
)
601 aloop
= loop_outer (aloop
);
612 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
613 for (fel_init (&(LI), &(LOOP), FLAGS); \
615 fel_next (&(LI), &(LOOP)))
617 #define FOR_EACH_LOOP_BREAK(LI) \
619 VEC_free (int, heap, (LI)->to_visit); \
623 /* The properties of the target. */
625 extern unsigned target_avail_regs
;
626 extern unsigned target_res_regs
;
627 extern unsigned target_reg_cost
[2];
628 extern unsigned target_spill_cost
[2];
630 /* Register pressure estimation for induction variable optimizations & loop
632 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool);
633 extern void init_set_costs (void);
635 /* Loop optimizer initialization. */
636 extern void loop_optimizer_init (unsigned);
637 extern void loop_optimizer_finalize (void);
639 /* Optimization passes. */
640 extern void unswitch_loops (void);
644 UAP_PEEL
= 1, /* Enables loop peeling. */
645 UAP_UNROLL
= 2, /* Enables unrolling of loops if it seems profitable. */
646 UAP_UNROLL_ALL
= 4 /* Enables unrolling of all loops. */
649 extern void unroll_and_peel_loops (int);
650 extern void doloop_optimize_loops (void);
651 extern void move_loop_invariants (void);
652 extern bool finite_loop_p (struct loop
*);
654 #endif /* GCC_CFGLOOP_H */