1 /* Natural loop functions
2 Copyright (C) 1987-2015 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/>. */
26 #include "hard-reg-set.h"
29 #include "cfgloopmanip.h"
31 /* Structure to hold decision about unrolling/peeling. */
40 struct GTY (()) lpt_decision
{
41 enum lpt_dec decision
;
45 /* The type of extend applied to an IV. */
53 /* The structure describing a bound on number of iterations of a loop. */
55 struct GTY ((chain_next ("%h.next"))) nb_iter_bound
{
56 /* The statement STMT is executed at most ... */
59 /* ... BOUND + 1 times (BOUND must be an unsigned constant).
60 The + 1 is added for the following reasons:
62 a) 0 would otherwise be unused, while we would need to care more about
63 overflows (as MAX + 1 is sometimes produced as the estimate on number
64 of executions of STMT).
65 b) it is consistent with the result of number_of_iterations_exit. */
68 /* True if the statement will cause the loop to be leaved the (at most)
69 BOUND + 1-st time it is executed, that is, all the statements after it
70 are executed at most BOUND times. */
73 /* The next bound in the list. */
74 struct nb_iter_bound
*next
;
77 /* Description of the loop exit. */
79 struct GTY ((for_user
)) loop_exit
{
83 /* Previous and next exit in the list of the exits of the loop. */
84 struct loop_exit
*prev
;
85 struct loop_exit
*next
;
87 /* Next element in the list of loops from that E exits. */
88 struct loop_exit
*next_e
;
91 struct loop_exit_hasher
: ggc_hasher
<loop_exit
*>
93 typedef edge compare_type
;
95 static hashval_t
hash (loop_exit
*);
96 static bool equal (loop_exit
*, edge
);
97 static void remove (loop_exit
*);
100 typedef struct loop
*loop_p
;
102 /* An integer estimation of the number of iterations. Estimate_state
103 describes what is the state of the estimation. */
106 /* Estimate was not computed yet. */
108 /* Estimate is ready. */
113 /* The structure describing non-overflow control induction variable for
115 struct GTY ((chain_next ("%h.next"))) control_iv
{
118 struct control_iv
*next
;
121 /* Structure to hold information for each natural loop. */
122 struct GTY ((chain_next ("%h.next"))) loop
{
123 /* Index into loops array. */
126 /* Number of loop insns. */
129 /* Basic block of loop header. */
132 /* Basic block of loop latch. */
135 /* For loop unrolling/peeling decision. */
136 struct lpt_decision lpt_decision
;
138 /* Average number of executed insns per iteration. */
141 /* Number of blocks contained within the loop. */
144 /* Superloops of the loop, starting with the outermost loop. */
145 vec
<loop_p
, va_gc
> *superloops
;
147 /* The first inner (child) loop or NULL if innermost loop. */
150 /* Link to the next (sibling) loop. */
153 /* Auxiliary info specific to a pass. */
154 PTR
GTY ((skip (""))) aux
;
156 /* The number of times the latch of the loop is executed. This can be an
157 INTEGER_CST, or a symbolic expression representing the number of
158 iterations like "N - 1", or a COND_EXPR containing the runtime
159 conditions under which the number of iterations is non zero.
161 Don't access this field directly: number_of_latch_executions
162 computes and caches the computed information in this field. */
165 /* An integer guaranteed to be greater or equal to nb_iterations. Only
166 valid if any_upper_bound is true. */
167 widest_int nb_iterations_upper_bound
;
169 /* An integer giving an estimate on nb_iterations. Unlike
170 nb_iterations_upper_bound, there is no guarantee that it is at least
172 widest_int nb_iterations_estimate
;
174 bool any_upper_bound
;
177 /* True if the loop can be parallel. */
178 bool can_be_parallel
;
180 /* True if -Waggressive-loop-optimizations warned about this loop
182 bool warned_aggressive_loop_optimizations
;
184 /* An integer estimation of the number of iterations. Estimate_state
185 describes what is the state of the estimation. */
186 enum loop_estimation estimate_state
;
188 /* If > 0, an integer, where the user asserted that for any
189 I in [ 0, nb_iterations ) and for any J in
190 [ I, min ( I + safelen, nb_iterations ) ), the Ith and Jth iterations
191 of the loop can be safely evaluated concurrently. */
194 /* True if this loop should never be vectorized. */
197 /* True if we should try harder to vectorize this loop. */
198 bool force_vectorize
;
200 /* For SIMD loops, this is a unique identifier of the loop, referenced
201 by IFN_GOMP_SIMD_VF, IFN_GOMP_SIMD_LANE and IFN_GOMP_SIMD_LAST_LANE
205 /* Upper bound on number of iterations of a loop. */
206 struct nb_iter_bound
*bounds
;
208 /* Non-overflow control ivs of a loop. */
209 struct control_iv
*control_ivs
;
211 /* Head of the cyclic list of the exits of the loop. */
212 struct loop_exit
*exits
;
214 /* Number of iteration analysis data for RTL. */
215 struct niter_desc
*simple_loop_desc
;
217 /* For sanity checking during loop fixup we record here the former
218 loop header for loops marked for removal. Note that this prevents
219 the basic-block from being collected but its index can still be
221 basic_block former_header
;
224 /* Flags for state of loop structure. */
227 LOOPS_HAVE_PREHEADERS
= 1,
228 LOOPS_HAVE_SIMPLE_LATCHES
= 2,
229 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS
= 4,
230 LOOPS_HAVE_RECORDED_EXITS
= 8,
231 LOOPS_MAY_HAVE_MULTIPLE_LATCHES
= 16,
232 LOOP_CLOSED_SSA
= 32,
233 LOOPS_NEED_FIXUP
= 64,
234 LOOPS_HAVE_FALLTHRU_PREHEADERS
= 128
237 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
238 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
239 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
241 /* Structure to hold CFG information about natural loops within a function. */
242 struct GTY (()) loops
{
243 /* State of loops. */
246 /* Array of the loops. */
247 vec
<loop_p
, va_gc
> *larray
;
249 /* Maps edges to the list of their descriptions as loop exits. Edges
250 whose sources or destinations have loop_father == NULL (which may
251 happen during the cfg manipulations) should not appear in EXITS. */
252 hash_table
<loop_exit_hasher
> *GTY(()) exits
;
254 /* Pointer to root of loop hierarchy tree. */
255 struct loop
*tree_root
;
258 /* Loop recognition. */
259 bool bb_loop_header_p (basic_block
);
260 void init_loops_structure (struct function
*, struct loops
*, unsigned);
261 extern struct loops
*flow_loops_find (struct loops
*);
262 extern void disambiguate_loops_with_multiple_latches (void);
263 extern void flow_loops_free (struct loops
*);
264 extern void flow_loops_dump (FILE *,
265 void (*)(const struct loop
*, FILE *, int), int);
266 extern void flow_loop_dump (const struct loop
*, FILE *,
267 void (*)(const struct loop
*, FILE *, int), int);
268 struct loop
*alloc_loop (void);
269 extern void flow_loop_free (struct loop
*);
270 int flow_loop_nodes_find (basic_block
, struct loop
*);
271 unsigned fix_loop_structure (bitmap changed_bbs
);
272 bool mark_irreducible_loops (void);
273 void release_recorded_exits (void);
274 void record_loop_exits (void);
275 void rescan_loop_exit (edge
, bool, bool);
277 /* Loop data structure manipulation/querying. */
278 extern void flow_loop_tree_node_add (struct loop
*, struct loop
*);
279 extern void flow_loop_tree_node_remove (struct loop
*);
280 extern bool flow_loop_nested_p (const struct loop
*, const struct loop
*);
281 extern bool flow_bb_inside_loop_p (const struct loop
*, const_basic_block
);
282 extern struct loop
* find_common_loop (struct loop
*, struct loop
*);
283 struct loop
*superloop_at_depth (struct loop
*, unsigned);
284 struct eni_weights_d
;
285 extern int num_loop_insns (const struct loop
*);
286 extern int average_num_loop_insns (const struct loop
*);
287 extern unsigned get_loop_level (const struct loop
*);
288 extern bool loop_exit_edge_p (const struct loop
*, const_edge
);
289 extern bool loop_exits_to_bb_p (struct loop
*, basic_block
);
290 extern bool loop_exits_from_bb_p (struct loop
*, basic_block
);
291 extern void mark_loop_exit_edges (void);
292 extern location_t
get_loop_location (struct loop
*loop
);
294 /* Loops & cfg manipulation. */
295 extern basic_block
*get_loop_body (const struct loop
*);
296 extern unsigned get_loop_body_with_size (const struct loop
*, basic_block
*,
298 extern basic_block
*get_loop_body_in_dom_order (const struct loop
*);
299 extern basic_block
*get_loop_body_in_bfs_order (const struct loop
*);
300 extern basic_block
*get_loop_body_in_custom_order (const struct loop
*,
301 int (*) (const void *, const void *));
303 extern vec
<edge
> get_loop_exit_edges (const struct loop
*);
304 extern edge
single_exit (const struct loop
*);
305 extern edge
single_likely_exit (struct loop
*loop
);
306 extern unsigned num_loop_branches (const struct loop
*);
308 extern edge
loop_preheader_edge (const struct loop
*);
309 extern edge
loop_latch_edge (const struct loop
*);
311 extern void add_bb_to_loop (basic_block
, struct loop
*);
312 extern void remove_bb_from_loops (basic_block
);
314 extern void cancel_loop_tree (struct loop
*);
315 extern void delete_loop (struct loop
*);
318 extern void verify_loop_structure (void);
321 extern bool just_once_each_iteration_p (const struct loop
*, const_basic_block
);
322 gcov_type
expected_loop_iterations_unbounded (const struct loop
*);
323 extern unsigned expected_loop_iterations (const struct loop
*);
324 extern rtx
doloop_condition_get (rtx
);
326 void mark_loop_for_removal (loop_p
);
328 /* Induction variable analysis. */
330 /* The description of induction variable. The things are a bit complicated
331 due to need to handle subregs and extends. The value of the object described
332 by it can be obtained as follows (all computations are done in extend_mode):
334 Value in i-th iteration is
335 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
337 If first_special is true, the value in the first iteration is
340 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
341 subreg_{mode} (base + i * step)
343 The get_iv_value function can be used to obtain these expressions.
345 ??? Add a third mode field that would specify the mode in that inner
346 computation is done, which would enable it to be different from the
351 /* Its base and step (mode of base and step is supposed to be extend_mode,
352 see the description above). */
355 /* The type of extend applied to it (IV_SIGN_EXTEND, IV_ZERO_EXTEND,
356 or IV_UNKNOWN_EXTEND). */
357 enum iv_extend_code extend
;
359 /* Operations applied in the extended mode. */
362 /* The mode it is extended to. */
363 machine_mode extend_mode
;
365 /* The mode the variable iterates in. */
368 /* Whether the first iteration needs to be handled specially. */
369 unsigned first_special
: 1;
372 /* The description of an exit from the loop and of the number of iterations
373 till we take the exit. */
375 struct GTY(()) niter_desc
377 /* The edge out of the loop. */
380 /* The other edge leading from the condition. */
383 /* True if we are able to say anything about number of iterations of the
387 /* True if the loop iterates the constant number of times. */
390 /* Number of iterations if constant. */
393 /* Assumptions under that the rest of the information is valid. */
396 /* Assumptions under that the loop ends before reaching the latch,
397 even if value of niter_expr says otherwise. */
398 rtx noloop_assumptions
;
400 /* Condition under that the loop is infinite. */
403 /* Whether the comparison is signed. */
406 /* The mode in that niter_expr should be computed. */
409 /* The number of iterations of the loop. */
413 extern void iv_analysis_loop_init (struct loop
*);
414 extern bool iv_analyze (rtx_insn
*, rtx
, struct rtx_iv
*);
415 extern bool iv_analyze_result (rtx_insn
*, rtx
, struct rtx_iv
*);
416 extern bool iv_analyze_expr (rtx_insn
*, rtx
, machine_mode
,
418 extern rtx
get_iv_value (struct rtx_iv
*, rtx
);
419 extern bool biv_p (rtx_insn
*, rtx
);
420 extern void find_simple_exit (struct loop
*, struct niter_desc
*);
421 extern void iv_analysis_done (void);
423 extern struct niter_desc
*get_simple_loop_desc (struct loop
*loop
);
424 extern void free_simple_loop_desc (struct loop
*loop
);
426 static inline struct niter_desc
*
427 simple_loop_desc (struct loop
*loop
)
429 return loop
->simple_loop_desc
;
432 /* Accessors for the loop structures. */
434 /* Returns the loop with index NUM from FNs loop tree. */
436 static inline struct loop
*
437 get_loop (struct function
*fn
, unsigned num
)
439 return (*loops_for_fn (fn
)->larray
)[num
];
442 /* Returns the number of superloops of LOOP. */
444 static inline unsigned
445 loop_depth (const struct loop
*loop
)
447 return vec_safe_length (loop
->superloops
);
450 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
453 static inline struct loop
*
454 loop_outer (const struct loop
*loop
)
456 unsigned n
= vec_safe_length (loop
->superloops
);
461 return (*loop
->superloops
)[n
- 1];
464 /* Returns true if LOOP has at least one exit edge. */
467 loop_has_exit_edges (const struct loop
*loop
)
469 return loop
->exits
->next
->e
!= NULL
;
472 /* Returns the list of loops in FN. */
474 inline vec
<loop_p
, va_gc
> *
475 get_loops (struct function
*fn
)
477 struct loops
*loops
= loops_for_fn (fn
);
481 return loops
->larray
;
484 /* Returns the number of loops in FN (including the removed
485 ones and the fake loop that forms the root of the loop tree). */
487 static inline unsigned
488 number_of_loops (struct function
*fn
)
490 struct loops
*loops
= loops_for_fn (fn
);
494 return vec_safe_length (loops
->larray
);
497 /* Returns true if state of the loops satisfies all properties
498 described by FLAGS. */
501 loops_state_satisfies_p (unsigned flags
)
503 return (current_loops
->state
& flags
) == flags
;
506 /* Sets FLAGS to the loops state. */
509 loops_state_set (unsigned flags
)
511 current_loops
->state
|= flags
;
514 /* Clears FLAGS from the loops state. */
517 loops_state_clear (unsigned flags
)
521 current_loops
->state
&= ~flags
;
524 /* Loop iterators. */
526 /* Flags for loop iteration. */
530 LI_INCLUDE_ROOT
= 1, /* Include the fake root of the loop tree. */
531 LI_FROM_INNERMOST
= 2, /* Iterate over the loops in the reverse order,
532 starting from innermost ones. */
533 LI_ONLY_INNERMOST
= 4 /* Iterate only over innermost loops. */
536 /* The iterator for loops. */
540 loop_iterator (loop_p
*loop
, unsigned flags
);
543 inline loop_p
next ();
545 /* The list of loops to visit. */
548 /* The index of the actual loop. */
553 loop_iterator::next ()
557 while (this->to_visit
.iterate (this->idx
, &anum
))
560 loop_p loop
= get_loop (cfun
, anum
);
569 loop_iterator::loop_iterator (loop_p
*loop
, unsigned flags
)
578 this->to_visit
.create (0);
583 this->to_visit
.create (number_of_loops (cfun
));
584 mn
= (flags
& LI_INCLUDE_ROOT
) ? 0 : 1;
586 if (flags
& LI_ONLY_INNERMOST
)
588 for (i
= 0; vec_safe_iterate (current_loops
->larray
, i
, &aloop
); i
++)
590 && aloop
->inner
== NULL
592 this->to_visit
.quick_push (aloop
->num
);
594 else if (flags
& LI_FROM_INNERMOST
)
596 /* Push the loops to LI->TO_VISIT in postorder. */
597 for (aloop
= current_loops
->tree_root
;
598 aloop
->inner
!= NULL
;
599 aloop
= aloop
->inner
)
604 if (aloop
->num
>= mn
)
605 this->to_visit
.quick_push (aloop
->num
);
609 for (aloop
= aloop
->next
;
610 aloop
->inner
!= NULL
;
611 aloop
= aloop
->inner
)
614 else if (!loop_outer (aloop
))
617 aloop
= loop_outer (aloop
);
622 /* Push the loops to LI->TO_VISIT in preorder. */
623 aloop
= current_loops
->tree_root
;
626 if (aloop
->num
>= mn
)
627 this->to_visit
.quick_push (aloop
->num
);
629 if (aloop
->inner
!= NULL
)
630 aloop
= aloop
->inner
;
633 while (aloop
!= NULL
&& aloop
->next
== NULL
)
634 aloop
= loop_outer (aloop
);
642 *loop
= this->next ();
646 loop_iterator::~loop_iterator ()
648 this->to_visit
.release ();
651 #define FOR_EACH_LOOP(LOOP, FLAGS) \
652 for (loop_iterator li(&(LOOP), FLAGS); \
656 /* The properties of the target. */
657 struct target_cfgloop
{
658 /* Number of available registers. */
659 unsigned x_target_avail_regs
;
661 /* Number of available registers that are call-clobbered. */
662 unsigned x_target_clobbered_regs
;
664 /* Number of registers reserved for temporary expressions. */
665 unsigned x_target_res_regs
;
667 /* The cost for register when there still is some reserve, but we are
668 approaching the number of available registers. */
669 unsigned x_target_reg_cost
[2];
671 /* The cost for register when we need to spill. */
672 unsigned x_target_spill_cost
[2];
675 extern struct target_cfgloop default_target_cfgloop
;
676 #if SWITCHABLE_TARGET
677 extern struct target_cfgloop
*this_target_cfgloop
;
679 #define this_target_cfgloop (&default_target_cfgloop)
682 #define target_avail_regs \
683 (this_target_cfgloop->x_target_avail_regs)
684 #define target_clobbered_regs \
685 (this_target_cfgloop->x_target_clobbered_regs)
686 #define target_res_regs \
687 (this_target_cfgloop->x_target_res_regs)
688 #define target_reg_cost \
689 (this_target_cfgloop->x_target_reg_cost)
690 #define target_spill_cost \
691 (this_target_cfgloop->x_target_spill_cost)
693 /* Register pressure estimation for induction variable optimizations & loop
695 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool, bool);
696 extern void init_set_costs (void);
698 /* Loop optimizer initialization. */
699 extern void loop_optimizer_init (unsigned);
700 extern void loop_optimizer_finalize (void);
702 /* Optimization passes. */
705 UAP_UNROLL
= 1, /* Enables unrolling of loops if it seems profitable. */
706 UAP_UNROLL_ALL
= 2 /* Enables unrolling of all loops. */
709 extern void doloop_optimize_loops (void);
710 extern void move_loop_invariants (void);
711 extern vec
<basic_block
> get_loop_hot_path (const struct loop
*loop
);
713 /* Returns the outermost loop of the loop nest that contains LOOP.*/
714 static inline struct loop
*
715 loop_outermost (struct loop
*loop
)
717 unsigned n
= vec_safe_length (loop
->superloops
);
722 return (*loop
->superloops
)[1];
725 extern void record_niter_bound (struct loop
*, const widest_int
&, bool, bool);
726 extern HOST_WIDE_INT
get_estimated_loop_iterations_int (struct loop
*);
727 extern HOST_WIDE_INT
get_max_loop_iterations_int (struct loop
*);
728 extern bool get_estimated_loop_iterations (struct loop
*loop
, widest_int
*nit
);
729 extern bool get_max_loop_iterations (struct loop
*loop
, widest_int
*nit
);
730 extern int bb_loop_depth (const_basic_block
);
732 /* Converts VAL to widest_int. */
734 static inline widest_int
735 gcov_type_to_wide_int (gcov_type val
)
739 a
[0] = (unsigned HOST_WIDE_INT
) val
;
740 /* If HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_WIDEST_INT, avoid shifting by
742 val
>>= HOST_BITS_PER_WIDE_INT
- 1;
744 a
[1] = (unsigned HOST_WIDE_INT
) val
;
746 return widest_int::from_array (a
, 2);
748 #endif /* GCC_CFGLOOP_H */