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/>. */
23 #include "cfgloopmanip.h"
25 /* Structure to hold decision about unrolling/peeling. */
34 struct GTY (()) lpt_decision
{
35 enum lpt_dec decision
;
39 /* The type of extend applied to an IV. */
47 /* The structure describing a bound on number of iterations of a loop. */
49 struct GTY ((chain_next ("%h.next"))) nb_iter_bound
{
50 /* The statement STMT is executed at most ... */
53 /* ... BOUND + 1 times (BOUND must be an unsigned constant).
54 The + 1 is added for the following reasons:
56 a) 0 would otherwise be unused, while we would need to care more about
57 overflows (as MAX + 1 is sometimes produced as the estimate on number
58 of executions of STMT).
59 b) it is consistent with the result of number_of_iterations_exit. */
62 /* True if the statement will cause the loop to be leaved the (at most)
63 BOUND + 1-st time it is executed, that is, all the statements after it
64 are executed at most BOUND times. */
67 /* The next bound in the list. */
68 struct nb_iter_bound
*next
;
71 /* Description of the loop exit. */
73 struct GTY ((for_user
)) loop_exit
{
77 /* Previous and next exit in the list of the exits of the loop. */
78 struct loop_exit
*prev
;
79 struct loop_exit
*next
;
81 /* Next element in the list of loops from that E exits. */
82 struct loop_exit
*next_e
;
85 struct loop_exit_hasher
: ggc_ptr_hash
<loop_exit
>
87 typedef edge compare_type
;
89 static hashval_t
hash (loop_exit
*);
90 static bool equal (loop_exit
*, edge
);
91 static void remove (loop_exit
*);
94 typedef struct loop
*loop_p
;
96 /* An integer estimation of the number of iterations. Estimate_state
97 describes what is the state of the estimation. */
100 /* Estimate was not computed yet. */
102 /* Estimate is ready. */
107 /* The structure describing non-overflow control induction variable for
109 struct GTY ((chain_next ("%h.next"))) control_iv
{
112 struct control_iv
*next
;
115 /* Structure to hold information for each natural loop. */
116 struct GTY ((chain_next ("%h.next"))) loop
{
117 /* Index into loops array. */
120 /* Number of loop insns. */
123 /* Basic block of loop header. */
126 /* Basic block of loop latch. */
129 /* For loop unrolling/peeling decision. */
130 struct lpt_decision lpt_decision
;
132 /* Average number of executed insns per iteration. */
135 /* Number of blocks contained within the loop. */
138 /* Superloops of the loop, starting with the outermost loop. */
139 vec
<loop_p
, va_gc
> *superloops
;
141 /* The first inner (child) loop or NULL if innermost loop. */
144 /* Link to the next (sibling) loop. */
147 /* Auxiliary info specific to a pass. */
148 PTR
GTY ((skip (""))) aux
;
150 /* The number of times the latch of the loop is executed. This can be an
151 INTEGER_CST, or a symbolic expression representing the number of
152 iterations like "N - 1", or a COND_EXPR containing the runtime
153 conditions under which the number of iterations is non zero.
155 Don't access this field directly: number_of_latch_executions
156 computes and caches the computed information in this field. */
159 /* An integer guaranteed to be greater or equal to nb_iterations. Only
160 valid if any_upper_bound is true. */
161 widest_int nb_iterations_upper_bound
;
163 /* An integer giving an estimate on nb_iterations. Unlike
164 nb_iterations_upper_bound, there is no guarantee that it is at least
166 widest_int nb_iterations_estimate
;
168 bool any_upper_bound
;
171 /* True if the loop can be parallel. */
172 bool can_be_parallel
;
174 /* True if -Waggressive-loop-optimizations warned about this loop
176 bool warned_aggressive_loop_optimizations
;
178 /* An integer estimation of the number of iterations. Estimate_state
179 describes what is the state of the estimation. */
180 enum loop_estimation estimate_state
;
182 /* If > 0, an integer, where the user asserted that for any
183 I in [ 0, nb_iterations ) and for any J in
184 [ I, min ( I + safelen, nb_iterations ) ), the Ith and Jth iterations
185 of the loop can be safely evaluated concurrently. */
188 /* True if this loop should never be vectorized. */
191 /* True if we should try harder to vectorize this loop. */
192 bool force_vectorize
;
194 /* For SIMD loops, this is a unique identifier of the loop, referenced
195 by IFN_GOMP_SIMD_VF, IFN_GOMP_SIMD_LANE and IFN_GOMP_SIMD_LAST_LANE
199 /* Upper bound on number of iterations of a loop. */
200 struct nb_iter_bound
*bounds
;
202 /* Non-overflow control ivs of a loop. */
203 struct control_iv
*control_ivs
;
205 /* Head of the cyclic list of the exits of the loop. */
206 struct loop_exit
*exits
;
208 /* Number of iteration analysis data for RTL. */
209 struct niter_desc
*simple_loop_desc
;
211 /* For sanity checking during loop fixup we record here the former
212 loop header for loops marked for removal. Note that this prevents
213 the basic-block from being collected but its index can still be
215 basic_block former_header
;
218 /* Flags for state of loop structure. */
221 LOOPS_HAVE_PREHEADERS
= 1,
222 LOOPS_HAVE_SIMPLE_LATCHES
= 2,
223 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS
= 4,
224 LOOPS_HAVE_RECORDED_EXITS
= 8,
225 LOOPS_MAY_HAVE_MULTIPLE_LATCHES
= 16,
226 LOOP_CLOSED_SSA
= 32,
227 LOOPS_NEED_FIXUP
= 64,
228 LOOPS_HAVE_FALLTHRU_PREHEADERS
= 128
231 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
232 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
233 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
235 /* Structure to hold CFG information about natural loops within a function. */
236 struct GTY (()) loops
{
237 /* State of loops. */
240 /* Array of the loops. */
241 vec
<loop_p
, va_gc
> *larray
;
243 /* Maps edges to the list of their descriptions as loop exits. Edges
244 whose sources or destinations have loop_father == NULL (which may
245 happen during the cfg manipulations) should not appear in EXITS. */
246 hash_table
<loop_exit_hasher
> *GTY(()) exits
;
248 /* Pointer to root of loop hierarchy tree. */
249 struct loop
*tree_root
;
252 /* Loop recognition. */
253 bool bb_loop_header_p (basic_block
);
254 void init_loops_structure (struct function
*, struct loops
*, unsigned);
255 extern struct loops
*flow_loops_find (struct loops
*);
256 extern void disambiguate_loops_with_multiple_latches (void);
257 extern void flow_loops_free (struct loops
*);
258 extern void flow_loops_dump (FILE *,
259 void (*)(const struct loop
*, FILE *, int), int);
260 extern void flow_loop_dump (const struct loop
*, FILE *,
261 void (*)(const struct loop
*, FILE *, int), int);
262 struct loop
*alloc_loop (void);
263 extern void flow_loop_free (struct loop
*);
264 int flow_loop_nodes_find (basic_block
, struct loop
*);
265 unsigned fix_loop_structure (bitmap changed_bbs
);
266 bool mark_irreducible_loops (void);
267 void release_recorded_exits (function
*);
268 void record_loop_exits (void);
269 void rescan_loop_exit (edge
, bool, bool);
271 /* Loop data structure manipulation/querying. */
272 extern void flow_loop_tree_node_add (struct loop
*, struct loop
*);
273 extern void flow_loop_tree_node_remove (struct loop
*);
274 extern bool flow_loop_nested_p (const struct loop
*, const struct loop
*);
275 extern bool flow_bb_inside_loop_p (const struct loop
*, const_basic_block
);
276 extern struct loop
* find_common_loop (struct loop
*, struct loop
*);
277 struct loop
*superloop_at_depth (struct loop
*, unsigned);
279 extern int num_loop_insns (const struct loop
*);
280 extern int average_num_loop_insns (const struct loop
*);
281 extern unsigned get_loop_level (const struct loop
*);
282 extern bool loop_exit_edge_p (const struct loop
*, const_edge
);
283 extern bool loop_exits_to_bb_p (struct loop
*, basic_block
);
284 extern bool loop_exits_from_bb_p (struct loop
*, basic_block
);
285 extern void mark_loop_exit_edges (void);
286 extern location_t
get_loop_location (struct loop
*loop
);
288 /* Loops & cfg manipulation. */
289 extern basic_block
*get_loop_body (const struct loop
*);
290 extern unsigned get_loop_body_with_size (const struct loop
*, basic_block
*,
292 extern basic_block
*get_loop_body_in_dom_order (const struct loop
*);
293 extern basic_block
*get_loop_body_in_bfs_order (const struct loop
*);
294 extern basic_block
*get_loop_body_in_custom_order (const struct loop
*,
295 int (*) (const void *, const void *));
297 extern vec
<edge
> get_loop_exit_edges (const struct loop
*);
298 extern edge
single_exit (const struct loop
*);
299 extern edge
single_likely_exit (struct loop
*loop
);
300 extern unsigned num_loop_branches (const struct loop
*);
302 extern edge
loop_preheader_edge (const struct loop
*);
303 extern edge
loop_latch_edge (const struct loop
*);
305 extern void add_bb_to_loop (basic_block
, struct loop
*);
306 extern void remove_bb_from_loops (basic_block
);
308 extern void cancel_loop_tree (struct loop
*);
309 extern void delete_loop (struct loop
*);
312 extern void verify_loop_structure (void);
314 /* Check loop structure invariants, if internal consistency checks are
318 checking_verify_loop_structure (void)
321 verify_loop_structure ();
325 extern bool just_once_each_iteration_p (const struct loop
*, const_basic_block
);
326 gcov_type
expected_loop_iterations_unbounded (const struct loop
*);
327 extern unsigned expected_loop_iterations (const struct loop
*);
328 extern rtx
doloop_condition_get (rtx
);
330 void mark_loop_for_removal (loop_p
);
332 /* Induction variable analysis. */
334 /* The description of induction variable. The things are a bit complicated
335 due to need to handle subregs and extends. The value of the object described
336 by it can be obtained as follows (all computations are done in extend_mode):
338 Value in i-th iteration is
339 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
341 If first_special is true, the value in the first iteration is
344 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
345 subreg_{mode} (base + i * step)
347 The get_iv_value function can be used to obtain these expressions.
349 ??? Add a third mode field that would specify the mode in that inner
350 computation is done, which would enable it to be different from the
355 /* Its base and step (mode of base and step is supposed to be extend_mode,
356 see the description above). */
359 /* The type of extend applied to it (IV_SIGN_EXTEND, IV_ZERO_EXTEND,
360 or IV_UNKNOWN_EXTEND). */
361 enum iv_extend_code extend
;
363 /* Operations applied in the extended mode. */
366 /* The mode it is extended to. */
367 machine_mode extend_mode
;
369 /* The mode the variable iterates in. */
372 /* Whether the first iteration needs to be handled specially. */
373 unsigned first_special
: 1;
376 /* The description of an exit from the loop and of the number of iterations
377 till we take the exit. */
379 struct GTY(()) niter_desc
381 /* The edge out of the loop. */
384 /* The other edge leading from the condition. */
387 /* True if we are able to say anything about number of iterations of the
391 /* True if the loop iterates the constant number of times. */
394 /* Number of iterations if constant. */
397 /* Assumptions under that the rest of the information is valid. */
400 /* Assumptions under that the loop ends before reaching the latch,
401 even if value of niter_expr says otherwise. */
402 rtx noloop_assumptions
;
404 /* Condition under that the loop is infinite. */
407 /* Whether the comparison is signed. */
410 /* The mode in that niter_expr should be computed. */
413 /* The number of iterations of the loop. */
417 extern void iv_analysis_loop_init (struct loop
*);
418 extern bool iv_analyze (rtx_insn
*, rtx
, struct rtx_iv
*);
419 extern bool iv_analyze_result (rtx_insn
*, rtx
, struct rtx_iv
*);
420 extern bool iv_analyze_expr (rtx_insn
*, rtx
, machine_mode
,
422 extern rtx
get_iv_value (struct rtx_iv
*, rtx
);
423 extern bool biv_p (rtx_insn
*, rtx
);
424 extern void find_simple_exit (struct loop
*, struct niter_desc
*);
425 extern void iv_analysis_done (void);
427 extern struct niter_desc
*get_simple_loop_desc (struct loop
*loop
);
428 extern void free_simple_loop_desc (struct loop
*loop
);
430 static inline struct niter_desc
*
431 simple_loop_desc (struct loop
*loop
)
433 return loop
->simple_loop_desc
;
436 /* Accessors for the loop structures. */
438 /* Returns the loop with index NUM from FNs loop tree. */
440 static inline struct loop
*
441 get_loop (struct function
*fn
, unsigned num
)
443 return (*loops_for_fn (fn
)->larray
)[num
];
446 /* Returns the number of superloops of LOOP. */
448 static inline unsigned
449 loop_depth (const struct loop
*loop
)
451 return vec_safe_length (loop
->superloops
);
454 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
457 static inline struct loop
*
458 loop_outer (const struct loop
*loop
)
460 unsigned n
= vec_safe_length (loop
->superloops
);
465 return (*loop
->superloops
)[n
- 1];
468 /* Returns true if LOOP has at least one exit edge. */
471 loop_has_exit_edges (const struct loop
*loop
)
473 return loop
->exits
->next
->e
!= NULL
;
476 /* Returns the list of loops in FN. */
478 inline vec
<loop_p
, va_gc
> *
479 get_loops (struct function
*fn
)
481 struct loops
*loops
= loops_for_fn (fn
);
485 return loops
->larray
;
488 /* Returns the number of loops in FN (including the removed
489 ones and the fake loop that forms the root of the loop tree). */
491 static inline unsigned
492 number_of_loops (struct function
*fn
)
494 struct loops
*loops
= loops_for_fn (fn
);
498 return vec_safe_length (loops
->larray
);
501 /* Returns true if state of the loops satisfies all properties
502 described by FLAGS. */
505 loops_state_satisfies_p (function
*fn
, unsigned flags
)
507 return (loops_for_fn (fn
)->state
& flags
) == flags
;
511 loops_state_satisfies_p (unsigned flags
)
513 return loops_state_satisfies_p (cfun
, flags
);
516 /* Sets FLAGS to the loops state. */
519 loops_state_set (function
*fn
, unsigned flags
)
521 loops_for_fn (fn
)->state
|= flags
;
525 loops_state_set (unsigned flags
)
527 loops_state_set (cfun
, flags
);
530 /* Clears FLAGS from the loops state. */
533 loops_state_clear (function
*fn
, unsigned flags
)
535 loops_for_fn (fn
)->state
&= ~flags
;
539 loops_state_clear (unsigned flags
)
543 loops_state_clear (cfun
, flags
);
546 /* Loop iterators. */
548 /* Flags for loop iteration. */
552 LI_INCLUDE_ROOT
= 1, /* Include the fake root of the loop tree. */
553 LI_FROM_INNERMOST
= 2, /* Iterate over the loops in the reverse order,
554 starting from innermost ones. */
555 LI_ONLY_INNERMOST
= 4 /* Iterate only over innermost loops. */
558 /* The iterator for loops. */
562 loop_iterator (function
*fn
, loop_p
*loop
, unsigned flags
);
565 inline loop_p
next ();
567 /* The function we are visiting. */
570 /* The list of loops to visit. */
573 /* The index of the actual loop. */
578 loop_iterator::next ()
582 while (this->to_visit
.iterate (this->idx
, &anum
))
585 loop_p loop
= get_loop (fn
, anum
);
594 loop_iterator::loop_iterator (function
*fn
, loop_p
*loop
, unsigned flags
)
602 if (!loops_for_fn (fn
))
604 this->to_visit
.create (0);
609 this->to_visit
.create (number_of_loops (fn
));
610 mn
= (flags
& LI_INCLUDE_ROOT
) ? 0 : 1;
612 if (flags
& LI_ONLY_INNERMOST
)
614 for (i
= 0; vec_safe_iterate (loops_for_fn (fn
)->larray
, i
, &aloop
); i
++)
616 && aloop
->inner
== NULL
618 this->to_visit
.quick_push (aloop
->num
);
620 else if (flags
& LI_FROM_INNERMOST
)
622 /* Push the loops to LI->TO_VISIT in postorder. */
623 for (aloop
= loops_for_fn (fn
)->tree_root
;
624 aloop
->inner
!= NULL
;
625 aloop
= aloop
->inner
)
630 if (aloop
->num
>= mn
)
631 this->to_visit
.quick_push (aloop
->num
);
635 for (aloop
= aloop
->next
;
636 aloop
->inner
!= NULL
;
637 aloop
= aloop
->inner
)
640 else if (!loop_outer (aloop
))
643 aloop
= loop_outer (aloop
);
648 /* Push the loops to LI->TO_VISIT in preorder. */
649 aloop
= loops_for_fn (fn
)->tree_root
;
652 if (aloop
->num
>= mn
)
653 this->to_visit
.quick_push (aloop
->num
);
655 if (aloop
->inner
!= NULL
)
656 aloop
= aloop
->inner
;
659 while (aloop
!= NULL
&& aloop
->next
== NULL
)
660 aloop
= loop_outer (aloop
);
668 *loop
= this->next ();
672 loop_iterator::~loop_iterator ()
674 this->to_visit
.release ();
677 #define FOR_EACH_LOOP(LOOP, FLAGS) \
678 for (loop_iterator li(cfun, &(LOOP), FLAGS); \
682 #define FOR_EACH_LOOP_FN(FN, LOOP, FLAGS) \
683 for (loop_iterator li(fn, &(LOOP), FLAGS); \
687 /* The properties of the target. */
688 struct target_cfgloop
{
689 /* Number of available registers. */
690 unsigned x_target_avail_regs
;
692 /* Number of available registers that are call-clobbered. */
693 unsigned x_target_clobbered_regs
;
695 /* Number of registers reserved for temporary expressions. */
696 unsigned x_target_res_regs
;
698 /* The cost for register when there still is some reserve, but we are
699 approaching the number of available registers. */
700 unsigned x_target_reg_cost
[2];
702 /* The cost for register when we need to spill. */
703 unsigned x_target_spill_cost
[2];
706 extern struct target_cfgloop default_target_cfgloop
;
707 #if SWITCHABLE_TARGET
708 extern struct target_cfgloop
*this_target_cfgloop
;
710 #define this_target_cfgloop (&default_target_cfgloop)
713 #define target_avail_regs \
714 (this_target_cfgloop->x_target_avail_regs)
715 #define target_clobbered_regs \
716 (this_target_cfgloop->x_target_clobbered_regs)
717 #define target_res_regs \
718 (this_target_cfgloop->x_target_res_regs)
719 #define target_reg_cost \
720 (this_target_cfgloop->x_target_reg_cost)
721 #define target_spill_cost \
722 (this_target_cfgloop->x_target_spill_cost)
724 /* Register pressure estimation for induction variable optimizations & loop
726 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool, bool);
727 extern void init_set_costs (void);
729 /* Loop optimizer initialization. */
730 extern void loop_optimizer_init (unsigned);
731 extern void loop_optimizer_finalize (function
*);
733 loop_optimizer_finalize ()
735 loop_optimizer_finalize (cfun
);
738 /* Optimization passes. */
741 UAP_UNROLL
= 1, /* Enables unrolling of loops if it seems profitable. */
742 UAP_UNROLL_ALL
= 2 /* Enables unrolling of all loops. */
745 extern void doloop_optimize_loops (void);
746 extern void move_loop_invariants (void);
747 extern vec
<basic_block
> get_loop_hot_path (const struct loop
*loop
);
749 /* Returns the outermost loop of the loop nest that contains LOOP.*/
750 static inline struct loop
*
751 loop_outermost (struct loop
*loop
)
753 unsigned n
= vec_safe_length (loop
->superloops
);
758 return (*loop
->superloops
)[1];
761 extern void record_niter_bound (struct loop
*, const widest_int
&, bool, bool);
762 extern HOST_WIDE_INT
get_estimated_loop_iterations_int (struct loop
*);
763 extern HOST_WIDE_INT
get_max_loop_iterations_int (struct loop
*);
764 extern bool get_estimated_loop_iterations (struct loop
*loop
, widest_int
*nit
);
765 extern bool get_max_loop_iterations (struct loop
*loop
, widest_int
*nit
);
766 extern int bb_loop_depth (const_basic_block
);
768 /* Converts VAL to widest_int. */
770 static inline widest_int
771 gcov_type_to_wide_int (gcov_type val
)
775 a
[0] = (unsigned HOST_WIDE_INT
) val
;
776 /* If HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_WIDEST_INT, avoid shifting by
778 val
>>= HOST_BITS_PER_WIDE_INT
- 1;
780 a
[1] = (unsigned HOST_WIDE_INT
) val
;
782 return widest_int::from_array (a
, 2);
784 #endif /* GCC_CFGLOOP_H */