1 /* Natural loop functions
2 Copyright (C) 1987-2014 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 3, or (at your option) any later
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
23 #include "double-int.h"
28 /* Structure to hold decision about unrolling/peeling. */
39 struct GTY (()) lpt_decision
{
40 enum lpt_dec decision
;
44 /* The type of extend applied to an IV. */
52 /* The structure describing a bound on number of iterations of a loop. */
54 struct GTY ((chain_next ("%h.next"))) nb_iter_bound
{
55 /* The statement STMT is executed at most ... */
58 /* ... BOUND + 1 times (BOUND must be an unsigned constant).
59 The + 1 is added for the following reasons:
61 a) 0 would otherwise be unused, while we would need to care more about
62 overflows (as MAX + 1 is sometimes produced as the estimate on number
63 of executions of STMT).
64 b) it is consistent with the result of number_of_iterations_exit. */
67 /* True if the statement will cause the loop to be leaved the (at most)
68 BOUND + 1-st time it is executed, that is, all the statements after it
69 are executed at most BOUND times. */
72 /* The next bound in the list. */
73 struct nb_iter_bound
*next
;
76 /* Description of the loop exit. */
78 struct GTY (()) loop_exit
{
82 /* Previous and next exit in the list of the exits of the loop. */
83 struct loop_exit
*prev
;
84 struct loop_exit
*next
;
86 /* Next element in the list of loops from that E exits. */
87 struct loop_exit
*next_e
;
90 typedef struct loop
*loop_p
;
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. */
103 /* Structure to hold information for each natural loop. */
104 struct GTY ((chain_next ("%h.next"))) loop
{
105 /* Index into loops array. */
108 /* Number of loop insns. */
111 /* Basic block of loop header. */
114 /* Basic block of loop 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
, va_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. This can be an
139 INTEGER_CST, or a symbolic expression representing the number of
140 iterations like "N - 1", or a COND_EXPR containing the runtime
141 conditions under which the number of iterations is non zero.
143 Don't access this field directly: number_of_latch_executions
144 computes and caches the computed information in this field. */
147 /* An integer guaranteed to be greater or equal to nb_iterations. Only
148 valid if any_upper_bound is true. */
149 double_int nb_iterations_upper_bound
;
151 /* An integer giving an estimate on nb_iterations. Unlike
152 nb_iterations_upper_bound, there is no guarantee that it is at least
154 double_int nb_iterations_estimate
;
156 bool any_upper_bound
;
159 /* True if the loop can be parallel. */
160 bool can_be_parallel
;
162 /* True if -Waggressive-loop-optimizations warned about this loop
164 bool warned_aggressive_loop_optimizations
;
166 /* An integer estimation of the number of iterations. Estimate_state
167 describes what is the state of the estimation. */
168 enum loop_estimation estimate_state
;
170 /* If > 0, an integer, where the user asserted that for any
171 I in [ 0, nb_iterations ) and for any J in
172 [ I, min ( I + safelen, nb_iterations ) ), the Ith and Jth iterations
173 of the loop can be safely evaluated concurrently. */
176 /* True if we should try harder to vectorize this loop. */
179 /* True if this loop should never be vectorized. */
182 /* For SIMD loops, this is a unique identifier of the loop, referenced
183 by IFN_GOMP_SIMD_VF, IFN_GOMP_SIMD_LANE and IFN_GOMP_SIMD_LAST_LANE
187 /* Upper bound on number of iterations of a loop. */
188 struct nb_iter_bound
*bounds
;
190 /* Head of the cyclic list of the exits of the loop. */
191 struct loop_exit
*exits
;
193 /* Number of iteration analysis data for RTL. */
194 struct niter_desc
*simple_loop_desc
;
196 /* For sanity checking during loop fixup we record here the former
197 loop header for loops marked for removal. Note that this prevents
198 the basic-block from being collected but its index can still be
200 basic_block former_header
;
203 /* Flags for state of loop structure. */
206 LOOPS_HAVE_PREHEADERS
= 1,
207 LOOPS_HAVE_SIMPLE_LATCHES
= 2,
208 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS
= 4,
209 LOOPS_HAVE_RECORDED_EXITS
= 8,
210 LOOPS_MAY_HAVE_MULTIPLE_LATCHES
= 16,
211 LOOP_CLOSED_SSA
= 32,
212 LOOPS_NEED_FIXUP
= 64,
213 LOOPS_HAVE_FALLTHRU_PREHEADERS
= 128
216 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
217 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
218 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
220 /* Structure to hold CFG information about natural loops within a function. */
221 struct GTY (()) loops
{
222 /* State of loops. */
225 /* Array of the loops. */
226 vec
<loop_p
, va_gc
> *larray
;
228 /* Maps edges to the list of their descriptions as loop exits. Edges
229 whose sources or destinations have loop_father == NULL (which may
230 happen during the cfg manipulations) should not appear in EXITS. */
231 htab_t
GTY((param_is (struct loop_exit
))) exits
;
233 /* Pointer to root of loop hierarchy tree. */
234 struct loop
*tree_root
;
237 /* Loop recognition. */
238 bool bb_loop_header_p (basic_block
);
239 void init_loops_structure (struct function
*, struct loops
*, unsigned);
240 extern struct loops
*flow_loops_find (struct loops
*);
241 extern void disambiguate_loops_with_multiple_latches (void);
242 extern void flow_loops_free (struct loops
*);
243 extern void flow_loops_dump (FILE *,
244 void (*)(const struct loop
*, FILE *, int), int);
245 extern void flow_loop_dump (const struct loop
*, FILE *,
246 void (*)(const struct loop
*, FILE *, int), int);
247 struct loop
*alloc_loop (void);
248 extern void flow_loop_free (struct loop
*);
249 int flow_loop_nodes_find (basic_block
, struct loop
*);
250 unsigned fix_loop_structure (bitmap changed_bbs
);
251 bool mark_irreducible_loops (void);
252 void release_recorded_exits (void);
253 void record_loop_exits (void);
254 void rescan_loop_exit (edge
, bool, bool);
256 /* Loop data structure manipulation/querying. */
257 extern void flow_loop_tree_node_add (struct loop
*, struct loop
*);
258 extern void flow_loop_tree_node_remove (struct loop
*);
259 extern void place_new_loop (struct function
*, struct loop
*);
260 extern void add_loop (struct loop
*, struct loop
*);
261 extern bool flow_loop_nested_p (const struct loop
*, const struct loop
*);
262 extern bool flow_bb_inside_loop_p (const struct loop
*, const_basic_block
);
263 extern struct loop
* find_common_loop (struct loop
*, struct loop
*);
264 struct loop
*superloop_at_depth (struct loop
*, unsigned);
265 struct eni_weights_d
;
266 extern int num_loop_insns (const struct loop
*);
267 extern int average_num_loop_insns (const struct loop
*);
268 extern unsigned get_loop_level (const struct loop
*);
269 extern bool loop_exit_edge_p (const struct loop
*, const_edge
);
270 extern bool loop_exits_to_bb_p (struct loop
*, basic_block
);
271 extern bool loop_exits_from_bb_p (struct loop
*, basic_block
);
272 extern void mark_loop_exit_edges (void);
273 extern location_t
get_loop_location (struct loop
*loop
);
275 /* Loops & cfg manipulation. */
276 extern basic_block
*get_loop_body (const struct loop
*);
277 extern unsigned get_loop_body_with_size (const struct loop
*, basic_block
*,
279 extern basic_block
*get_loop_body_in_dom_order (const struct loop
*);
280 extern basic_block
*get_loop_body_in_bfs_order (const struct loop
*);
281 extern basic_block
*get_loop_body_in_custom_order (const struct loop
*,
282 int (*) (const void *, const void *));
284 extern vec
<edge
> get_loop_exit_edges (const struct loop
*);
285 extern edge
single_exit (const struct loop
*);
286 extern edge
single_likely_exit (struct loop
*loop
);
287 extern unsigned num_loop_branches (const struct loop
*);
289 extern edge
loop_preheader_edge (const struct loop
*);
290 extern edge
loop_latch_edge (const struct loop
*);
292 extern void add_bb_to_loop (basic_block
, struct loop
*);
293 extern void remove_bb_from_loops (basic_block
);
295 extern void cancel_loop_tree (struct loop
*);
296 extern void delete_loop (struct loop
*);
300 CP_SIMPLE_PREHEADERS
= 1,
301 CP_FALLTHRU_PREHEADERS
= 2
304 basic_block
create_preheader (struct loop
*, int);
305 extern void create_preheaders (int);
306 extern void force_single_succ_latches (void);
308 extern void verify_loop_structure (void);
311 extern bool just_once_each_iteration_p (const struct loop
*, const_basic_block
);
312 gcov_type
expected_loop_iterations_unbounded (const struct loop
*);
313 extern unsigned expected_loop_iterations (const struct loop
*);
314 extern rtx
doloop_condition_get (rtx
);
317 /* Loop manipulation. */
318 extern bool can_duplicate_loop_p (const struct loop
*loop
);
320 #define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in
321 duplicate_loop_to_header_edge. */
322 #define DLTHE_RECORD_COPY_NUMBER 2 /* Record copy number in the aux
323 field of newly create BB. */
324 #define DLTHE_FLAG_COMPLETTE_PEEL 4 /* Update frequencies expecting
325 a complete peeling. */
327 extern edge
create_empty_if_region_on_edge (edge
, tree
);
328 extern struct loop
*create_empty_loop_on_edge (edge
, tree
, tree
, tree
, tree
,
329 tree
*, tree
*, struct loop
*);
330 extern struct loop
* duplicate_loop (struct loop
*, struct loop
*);
331 extern void copy_loop_info (struct loop
*loop
, struct loop
*target
);
332 extern void duplicate_subloops (struct loop
*, struct loop
*);
333 extern bool duplicate_loop_to_header_edge (struct loop
*, edge
,
334 unsigned, sbitmap
, edge
,
336 extern struct loop
*loopify (edge
, edge
,
337 basic_block
, edge
, edge
, bool,
339 struct loop
* loop_version (struct loop
*, void *,
340 basic_block
*, unsigned, unsigned, unsigned, bool);
341 extern bool remove_path (edge
);
342 extern void unloop (struct loop
*, bool *, bitmap
);
343 extern void scale_loop_frequencies (struct loop
*, int, int);
344 void mark_loop_for_removal (loop_p
);
347 /* Induction variable analysis. */
349 /* The description of induction variable. The things are a bit complicated
350 due to need to handle subregs and extends. The value of the object described
351 by it can be obtained as follows (all computations are done in extend_mode):
353 Value in i-th iteration is
354 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
356 If first_special is true, the value in the first iteration is
359 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
360 subreg_{mode} (base + i * step)
362 The get_iv_value function can be used to obtain these expressions.
364 ??? Add a third mode field that would specify the mode in that inner
365 computation is done, which would enable it to be different from the
370 /* Its base and step (mode of base and step is supposed to be extend_mode,
371 see the description above). */
374 /* The type of extend applied to it (IV_SIGN_EXTEND, IV_ZERO_EXTEND,
375 or IV_UNKNOWN_EXTEND). */
376 enum iv_extend_code extend
;
378 /* Operations applied in the extended mode. */
381 /* The mode it is extended to. */
382 enum machine_mode extend_mode
;
384 /* The mode the variable iterates in. */
385 enum machine_mode mode
;
387 /* Whether the first iteration needs to be handled specially. */
388 unsigned first_special
: 1;
391 /* The description of an exit from the loop and of the number of iterations
392 till we take the exit. */
394 struct GTY(()) niter_desc
396 /* The edge out of the loop. */
399 /* The other edge leading from the condition. */
402 /* True if we are able to say anything about number of iterations of the
406 /* True if the loop iterates the constant number of times. */
409 /* Number of iterations if constant. */
410 unsigned HOST_WIDEST_INT niter
;
412 /* Assumptions under that the rest of the information is valid. */
415 /* Assumptions under that the loop ends before reaching the latch,
416 even if value of niter_expr says otherwise. */
417 rtx noloop_assumptions
;
419 /* Condition under that the loop is infinite. */
422 /* Whether the comparison is signed. */
425 /* The mode in that niter_expr should be computed. */
426 enum machine_mode mode
;
428 /* The number of iterations of the loop. */
432 extern void iv_analysis_loop_init (struct loop
*);
433 extern bool iv_analyze (rtx
, rtx
, struct rtx_iv
*);
434 extern bool iv_analyze_result (rtx
, rtx
, struct rtx_iv
*);
435 extern bool iv_analyze_expr (rtx
, rtx
, enum machine_mode
, struct rtx_iv
*);
436 extern rtx
get_iv_value (struct rtx_iv
*, rtx
);
437 extern bool biv_p (rtx
, rtx
);
438 extern void find_simple_exit (struct loop
*, struct niter_desc
*);
439 extern void iv_analysis_done (void);
441 extern struct niter_desc
*get_simple_loop_desc (struct loop
*loop
);
442 extern void free_simple_loop_desc (struct loop
*loop
);
444 static inline struct niter_desc
*
445 simple_loop_desc (struct loop
*loop
)
447 return loop
->simple_loop_desc
;
450 /* Accessors for the loop structures. */
452 /* Returns the loop with index NUM from FNs loop tree. */
454 static inline struct loop
*
455 get_loop (struct function
*fn
, unsigned num
)
457 return (*loops_for_fn (fn
)->larray
)[num
];
460 /* Returns the number of superloops of LOOP. */
462 static inline unsigned
463 loop_depth (const struct loop
*loop
)
465 return vec_safe_length (loop
->superloops
);
468 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
471 static inline struct loop
*
472 loop_outer (const struct loop
*loop
)
474 unsigned n
= vec_safe_length (loop
->superloops
);
479 return (*loop
->superloops
)[n
- 1];
482 /* Returns true if LOOP has at least one exit edge. */
485 loop_has_exit_edges (const struct loop
*loop
)
487 return loop
->exits
->next
->e
!= NULL
;
490 /* Returns the list of loops in FN. */
492 inline vec
<loop_p
, va_gc
> *
493 get_loops (struct function
*fn
)
495 struct loops
*loops
= loops_for_fn (fn
);
499 return loops
->larray
;
502 /* Returns the number of loops in FN (including the removed
503 ones and the fake loop that forms the root of the loop tree). */
505 static inline unsigned
506 number_of_loops (struct function
*fn
)
508 struct loops
*loops
= loops_for_fn (fn
);
512 return vec_safe_length (loops
->larray
);
515 /* Returns true if state of the loops satisfies all properties
516 described by FLAGS. */
519 loops_state_satisfies_p (unsigned flags
)
521 return (current_loops
->state
& flags
) == flags
;
524 /* Sets FLAGS to the loops state. */
527 loops_state_set (unsigned flags
)
529 current_loops
->state
|= flags
;
532 /* Clears FLAGS from the loops state. */
535 loops_state_clear (unsigned flags
)
539 current_loops
->state
&= ~flags
;
542 /* Loop iterators. */
544 /* Flags for loop iteration. */
548 LI_INCLUDE_ROOT
= 1, /* Include the fake root of the loop tree. */
549 LI_FROM_INNERMOST
= 2, /* Iterate over the loops in the reverse order,
550 starting from innermost ones. */
551 LI_ONLY_INNERMOST
= 4 /* Iterate only over innermost loops. */
554 /* The iterator for loops. */
558 loop_iterator (loop_p
*loop
, unsigned flags
);
561 inline loop_p
next ();
563 /* The list of loops to visit. */
566 /* The index of the actual loop. */
571 loop_iterator::next ()
575 while (this->to_visit
.iterate (this->idx
, &anum
))
578 loop_p loop
= get_loop (cfun
, anum
);
587 loop_iterator::loop_iterator (loop_p
*loop
, unsigned flags
)
596 this->to_visit
.create (0);
601 this->to_visit
.create (number_of_loops (cfun
));
602 mn
= (flags
& LI_INCLUDE_ROOT
) ? 0 : 1;
604 if (flags
& LI_ONLY_INNERMOST
)
606 for (i
= 0; vec_safe_iterate (current_loops
->larray
, i
, &aloop
); i
++)
608 && aloop
->inner
== NULL
610 this->to_visit
.quick_push (aloop
->num
);
612 else if (flags
& LI_FROM_INNERMOST
)
614 /* Push the loops to LI->TO_VISIT in postorder. */
615 for (aloop
= current_loops
->tree_root
;
616 aloop
->inner
!= NULL
;
617 aloop
= aloop
->inner
)
622 if (aloop
->num
>= mn
)
623 this->to_visit
.quick_push (aloop
->num
);
627 for (aloop
= aloop
->next
;
628 aloop
->inner
!= NULL
;
629 aloop
= aloop
->inner
)
632 else if (!loop_outer (aloop
))
635 aloop
= loop_outer (aloop
);
640 /* Push the loops to LI->TO_VISIT in preorder. */
641 aloop
= current_loops
->tree_root
;
644 if (aloop
->num
>= mn
)
645 this->to_visit
.quick_push (aloop
->num
);
647 if (aloop
->inner
!= NULL
)
648 aloop
= aloop
->inner
;
651 while (aloop
!= NULL
&& aloop
->next
== NULL
)
652 aloop
= loop_outer (aloop
);
660 *loop
= this->next ();
664 loop_iterator::~loop_iterator ()
666 this->to_visit
.release ();
669 #define FOR_EACH_LOOP(LOOP, FLAGS) \
670 for (loop_iterator li(&(LOOP), FLAGS); \
674 /* The properties of the target. */
675 struct target_cfgloop
{
676 /* Number of available registers. */
677 unsigned x_target_avail_regs
;
679 /* Number of available registers that are call-clobbered. */
680 unsigned x_target_clobbered_regs
;
682 /* Number of registers reserved for temporary expressions. */
683 unsigned x_target_res_regs
;
685 /* The cost for register when there still is some reserve, but we are
686 approaching the number of available registers. */
687 unsigned x_target_reg_cost
[2];
689 /* The cost for register when we need to spill. */
690 unsigned x_target_spill_cost
[2];
693 extern struct target_cfgloop default_target_cfgloop
;
694 #if SWITCHABLE_TARGET
695 extern struct target_cfgloop
*this_target_cfgloop
;
697 #define this_target_cfgloop (&default_target_cfgloop)
700 #define target_avail_regs \
701 (this_target_cfgloop->x_target_avail_regs)
702 #define target_clobbered_regs \
703 (this_target_cfgloop->x_target_clobbered_regs)
704 #define target_res_regs \
705 (this_target_cfgloop->x_target_res_regs)
706 #define target_reg_cost \
707 (this_target_cfgloop->x_target_reg_cost)
708 #define target_spill_cost \
709 (this_target_cfgloop->x_target_spill_cost)
711 /* Register pressure estimation for induction variable optimizations & loop
713 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool, bool);
714 extern void init_set_costs (void);
716 /* Loop optimizer initialization. */
717 extern void loop_optimizer_init (unsigned);
718 extern void loop_optimizer_finalize (void);
720 /* Optimization passes. */
721 extern void unswitch_loops (void);
725 UAP_PEEL
= 1, /* Enables loop peeling. */
726 UAP_UNROLL
= 2, /* Enables unrolling of loops if it seems profitable. */
727 UAP_UNROLL_ALL
= 4 /* Enables unrolling of all loops. */
730 extern void unroll_and_peel_loops (int);
731 extern void doloop_optimize_loops (void);
732 extern void move_loop_invariants (void);
733 extern void scale_loop_profile (struct loop
*loop
, int scale
, gcov_type iteration_bound
);
734 extern vec
<basic_block
> get_loop_hot_path (const struct loop
*loop
);
736 /* Returns the outermost loop of the loop nest that contains LOOP.*/
737 static inline struct loop
*
738 loop_outermost (struct loop
*loop
)
740 unsigned n
= vec_safe_length (loop
->superloops
);
745 return (*loop
->superloops
)[1];
748 extern void record_niter_bound (struct loop
*, double_int
, bool, bool);
749 extern HOST_WIDE_INT
get_estimated_loop_iterations_int (struct loop
*);
750 extern HOST_WIDE_INT
get_max_loop_iterations_int (struct loop
*);
751 extern bool get_estimated_loop_iterations (struct loop
*loop
, double_int
*nit
);
752 extern bool get_max_loop_iterations (struct loop
*loop
, double_int
*nit
);
753 extern int bb_loop_depth (const_basic_block
);
755 /* Converts VAL to double_int. */
757 static inline double_int
758 gcov_type_to_double_int (gcov_type val
)
762 ret
.low
= (unsigned HOST_WIDE_INT
) val
;
763 /* If HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_WIDEST_INT, avoid shifting by
765 val
>>= HOST_BITS_PER_WIDE_INT
- 1;
767 ret
.high
= (unsigned HOST_WIDE_INT
) val
;
771 #endif /* GCC_CFGLOOP_H */