1 /* Natural loop functions
2 Copyright (C) 1987-2016 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 /* True if the loop is part of an oacc kernels region. */
195 bool in_oacc_kernels_region
;
197 /* For SIMD loops, this is a unique identifier of the loop, referenced
198 by IFN_GOMP_SIMD_VF, IFN_GOMP_SIMD_LANE and IFN_GOMP_SIMD_LAST_LANE
202 /* Upper bound on number of iterations of a loop. */
203 struct nb_iter_bound
*bounds
;
205 /* Non-overflow control ivs of a loop. */
206 struct control_iv
*control_ivs
;
208 /* Head of the cyclic list of the exits of the loop. */
209 struct loop_exit
*exits
;
211 /* Number of iteration analysis data for RTL. */
212 struct niter_desc
*simple_loop_desc
;
214 /* For sanity checking during loop fixup we record here the former
215 loop header for loops marked for removal. Note that this prevents
216 the basic-block from being collected but its index can still be
218 basic_block former_header
;
221 /* Flags for state of loop structure. */
224 LOOPS_HAVE_PREHEADERS
= 1,
225 LOOPS_HAVE_SIMPLE_LATCHES
= 2,
226 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS
= 4,
227 LOOPS_HAVE_RECORDED_EXITS
= 8,
228 LOOPS_MAY_HAVE_MULTIPLE_LATCHES
= 16,
229 LOOP_CLOSED_SSA
= 32,
230 LOOPS_NEED_FIXUP
= 64,
231 LOOPS_HAVE_FALLTHRU_PREHEADERS
= 128
234 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
235 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
236 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
238 /* Structure to hold CFG information about natural loops within a function. */
239 struct GTY (()) loops
{
240 /* State of loops. */
243 /* Array of the loops. */
244 vec
<loop_p
, va_gc
> *larray
;
246 /* Maps edges to the list of their descriptions as loop exits. Edges
247 whose sources or destinations have loop_father == NULL (which may
248 happen during the cfg manipulations) should not appear in EXITS. */
249 hash_table
<loop_exit_hasher
> *GTY(()) exits
;
251 /* Pointer to root of loop hierarchy tree. */
252 struct loop
*tree_root
;
255 /* Loop recognition. */
256 bool bb_loop_header_p (basic_block
);
257 void init_loops_structure (struct function
*, struct loops
*, unsigned);
258 extern struct loops
*flow_loops_find (struct loops
*);
259 extern void disambiguate_loops_with_multiple_latches (void);
260 extern void flow_loops_free (struct loops
*);
261 extern void flow_loops_dump (FILE *,
262 void (*)(const struct loop
*, FILE *, int), int);
263 extern void flow_loop_dump (const struct loop
*, FILE *,
264 void (*)(const struct loop
*, FILE *, int), int);
265 struct loop
*alloc_loop (void);
266 extern void flow_loop_free (struct loop
*);
267 int flow_loop_nodes_find (basic_block
, struct loop
*);
268 unsigned fix_loop_structure (bitmap changed_bbs
);
269 bool mark_irreducible_loops (void);
270 void release_recorded_exits (function
*);
271 void record_loop_exits (void);
272 void rescan_loop_exit (edge
, bool, bool);
274 /* Loop data structure manipulation/querying. */
275 extern void flow_loop_tree_node_add (struct loop
*, struct loop
*);
276 extern void flow_loop_tree_node_remove (struct loop
*);
277 extern bool flow_loop_nested_p (const struct loop
*, const struct loop
*);
278 extern bool flow_bb_inside_loop_p (const struct loop
*, const_basic_block
);
279 extern struct loop
* find_common_loop (struct loop
*, struct loop
*);
280 struct loop
*superloop_at_depth (struct loop
*, unsigned);
282 extern int num_loop_insns (const struct loop
*);
283 extern int average_num_loop_insns (const struct loop
*);
284 extern unsigned get_loop_level (const struct loop
*);
285 extern bool loop_exit_edge_p (const struct loop
*, const_edge
);
286 extern bool loop_exits_to_bb_p (struct loop
*, basic_block
);
287 extern bool loop_exits_from_bb_p (struct loop
*, basic_block
);
288 extern void mark_loop_exit_edges (void);
289 extern location_t
get_loop_location (struct loop
*loop
);
291 /* Loops & cfg manipulation. */
292 extern basic_block
*get_loop_body (const struct loop
*);
293 extern unsigned get_loop_body_with_size (const struct loop
*, basic_block
*,
295 extern basic_block
*get_loop_body_in_dom_order (const struct loop
*);
296 extern basic_block
*get_loop_body_in_bfs_order (const struct loop
*);
297 extern basic_block
*get_loop_body_in_custom_order (const struct loop
*,
298 int (*) (const void *, const void *));
300 extern vec
<edge
> get_loop_exit_edges (const struct loop
*);
301 extern edge
single_exit (const struct loop
*);
302 extern edge
single_likely_exit (struct loop
*loop
);
303 extern unsigned num_loop_branches (const struct loop
*);
305 extern edge
loop_preheader_edge (const struct loop
*);
306 extern edge
loop_latch_edge (const struct loop
*);
308 extern void add_bb_to_loop (basic_block
, struct loop
*);
309 extern void remove_bb_from_loops (basic_block
);
311 extern void cancel_loop_tree (struct loop
*);
312 extern void delete_loop (struct loop
*);
315 extern void verify_loop_structure (void);
317 /* Check loop structure invariants, if internal consistency checks are
321 checking_verify_loop_structure (void)
324 verify_loop_structure ();
328 extern bool just_once_each_iteration_p (const struct loop
*, const_basic_block
);
329 gcov_type
expected_loop_iterations_unbounded (const struct loop
*);
330 extern unsigned expected_loop_iterations (const struct loop
*);
331 extern rtx
doloop_condition_get (rtx
);
333 void mark_loop_for_removal (loop_p
);
335 /* Induction variable analysis. */
337 /* The description of induction variable. The things are a bit complicated
338 due to need to handle subregs and extends. The value of the object described
339 by it can be obtained as follows (all computations are done in extend_mode):
341 Value in i-th iteration is
342 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
344 If first_special is true, the value in the first iteration is
347 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
348 subreg_{mode} (base + i * step)
350 The get_iv_value function can be used to obtain these expressions.
352 ??? Add a third mode field that would specify the mode in that inner
353 computation is done, which would enable it to be different from the
358 /* Its base and step (mode of base and step is supposed to be extend_mode,
359 see the description above). */
362 /* The type of extend applied to it (IV_SIGN_EXTEND, IV_ZERO_EXTEND,
363 or IV_UNKNOWN_EXTEND). */
364 enum iv_extend_code extend
;
366 /* Operations applied in the extended mode. */
369 /* The mode it is extended to. */
370 machine_mode extend_mode
;
372 /* The mode the variable iterates in. */
375 /* Whether the first iteration needs to be handled specially. */
376 unsigned first_special
: 1;
379 /* The description of an exit from the loop and of the number of iterations
380 till we take the exit. */
382 struct GTY(()) niter_desc
384 /* The edge out of the loop. */
387 /* The other edge leading from the condition. */
390 /* True if we are able to say anything about number of iterations of the
394 /* True if the loop iterates the constant number of times. */
397 /* Number of iterations if constant. */
400 /* Assumptions under that the rest of the information is valid. */
403 /* Assumptions under that the loop ends before reaching the latch,
404 even if value of niter_expr says otherwise. */
405 rtx noloop_assumptions
;
407 /* Condition under that the loop is infinite. */
410 /* Whether the comparison is signed. */
413 /* The mode in that niter_expr should be computed. */
416 /* The number of iterations of the loop. */
420 extern void iv_analysis_loop_init (struct loop
*);
421 extern bool iv_analyze (rtx_insn
*, rtx
, struct rtx_iv
*);
422 extern bool iv_analyze_result (rtx_insn
*, rtx
, struct rtx_iv
*);
423 extern bool iv_analyze_expr (rtx_insn
*, rtx
, machine_mode
,
425 extern rtx
get_iv_value (struct rtx_iv
*, rtx
);
426 extern bool biv_p (rtx_insn
*, rtx
);
427 extern void find_simple_exit (struct loop
*, struct niter_desc
*);
428 extern void iv_analysis_done (void);
430 extern struct niter_desc
*get_simple_loop_desc (struct loop
*loop
);
431 extern void free_simple_loop_desc (struct loop
*loop
);
433 static inline struct niter_desc
*
434 simple_loop_desc (struct loop
*loop
)
436 return loop
->simple_loop_desc
;
439 /* Accessors for the loop structures. */
441 /* Returns the loop with index NUM from FNs loop tree. */
443 static inline struct loop
*
444 get_loop (struct function
*fn
, unsigned num
)
446 return (*loops_for_fn (fn
)->larray
)[num
];
449 /* Returns the number of superloops of LOOP. */
451 static inline unsigned
452 loop_depth (const struct loop
*loop
)
454 return vec_safe_length (loop
->superloops
);
457 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
460 static inline struct loop
*
461 loop_outer (const struct loop
*loop
)
463 unsigned n
= vec_safe_length (loop
->superloops
);
468 return (*loop
->superloops
)[n
- 1];
471 /* Returns true if LOOP has at least one exit edge. */
474 loop_has_exit_edges (const struct loop
*loop
)
476 return loop
->exits
->next
->e
!= NULL
;
479 /* Returns the list of loops in FN. */
481 inline vec
<loop_p
, va_gc
> *
482 get_loops (struct function
*fn
)
484 struct loops
*loops
= loops_for_fn (fn
);
488 return loops
->larray
;
491 /* Returns the number of loops in FN (including the removed
492 ones and the fake loop that forms the root of the loop tree). */
494 static inline unsigned
495 number_of_loops (struct function
*fn
)
497 struct loops
*loops
= loops_for_fn (fn
);
501 return vec_safe_length (loops
->larray
);
504 /* Returns true if state of the loops satisfies all properties
505 described by FLAGS. */
508 loops_state_satisfies_p (function
*fn
, unsigned flags
)
510 return (loops_for_fn (fn
)->state
& flags
) == flags
;
514 loops_state_satisfies_p (unsigned flags
)
516 return loops_state_satisfies_p (cfun
, flags
);
519 /* Sets FLAGS to the loops state. */
522 loops_state_set (function
*fn
, unsigned flags
)
524 loops_for_fn (fn
)->state
|= flags
;
528 loops_state_set (unsigned flags
)
530 loops_state_set (cfun
, flags
);
533 /* Clears FLAGS from the loops state. */
536 loops_state_clear (function
*fn
, unsigned flags
)
538 loops_for_fn (fn
)->state
&= ~flags
;
542 loops_state_clear (unsigned flags
)
546 loops_state_clear (cfun
, flags
);
549 /* Loop iterators. */
551 /* Flags for loop iteration. */
555 LI_INCLUDE_ROOT
= 1, /* Include the fake root of the loop tree. */
556 LI_FROM_INNERMOST
= 2, /* Iterate over the loops in the reverse order,
557 starting from innermost ones. */
558 LI_ONLY_INNERMOST
= 4 /* Iterate only over innermost loops. */
561 /* The iterator for loops. */
565 loop_iterator (function
*fn
, loop_p
*loop
, unsigned flags
);
568 inline loop_p
next ();
570 /* The function we are visiting. */
573 /* The list of loops to visit. */
576 /* The index of the actual loop. */
581 loop_iterator::next ()
585 while (this->to_visit
.iterate (this->idx
, &anum
))
588 loop_p loop
= get_loop (fn
, anum
);
597 loop_iterator::loop_iterator (function
*fn
, loop_p
*loop
, unsigned flags
)
605 if (!loops_for_fn (fn
))
607 this->to_visit
.create (0);
612 this->to_visit
.create (number_of_loops (fn
));
613 mn
= (flags
& LI_INCLUDE_ROOT
) ? 0 : 1;
615 if (flags
& LI_ONLY_INNERMOST
)
617 for (i
= 0; vec_safe_iterate (loops_for_fn (fn
)->larray
, i
, &aloop
); i
++)
619 && aloop
->inner
== NULL
621 this->to_visit
.quick_push (aloop
->num
);
623 else if (flags
& LI_FROM_INNERMOST
)
625 /* Push the loops to LI->TO_VISIT in postorder. */
626 for (aloop
= loops_for_fn (fn
)->tree_root
;
627 aloop
->inner
!= NULL
;
628 aloop
= aloop
->inner
)
633 if (aloop
->num
>= mn
)
634 this->to_visit
.quick_push (aloop
->num
);
638 for (aloop
= aloop
->next
;
639 aloop
->inner
!= NULL
;
640 aloop
= aloop
->inner
)
643 else if (!loop_outer (aloop
))
646 aloop
= loop_outer (aloop
);
651 /* Push the loops to LI->TO_VISIT in preorder. */
652 aloop
= loops_for_fn (fn
)->tree_root
;
655 if (aloop
->num
>= mn
)
656 this->to_visit
.quick_push (aloop
->num
);
658 if (aloop
->inner
!= NULL
)
659 aloop
= aloop
->inner
;
662 while (aloop
!= NULL
&& aloop
->next
== NULL
)
663 aloop
= loop_outer (aloop
);
671 *loop
= this->next ();
675 loop_iterator::~loop_iterator ()
677 this->to_visit
.release ();
680 #define FOR_EACH_LOOP(LOOP, FLAGS) \
681 for (loop_iterator li(cfun, &(LOOP), FLAGS); \
685 #define FOR_EACH_LOOP_FN(FN, LOOP, FLAGS) \
686 for (loop_iterator li(fn, &(LOOP), FLAGS); \
690 /* The properties of the target. */
691 struct target_cfgloop
{
692 /* Number of available registers. */
693 unsigned x_target_avail_regs
;
695 /* Number of available registers that are call-clobbered. */
696 unsigned x_target_clobbered_regs
;
698 /* Number of registers reserved for temporary expressions. */
699 unsigned x_target_res_regs
;
701 /* The cost for register when there still is some reserve, but we are
702 approaching the number of available registers. */
703 unsigned x_target_reg_cost
[2];
705 /* The cost for register when we need to spill. */
706 unsigned x_target_spill_cost
[2];
709 extern struct target_cfgloop default_target_cfgloop
;
710 #if SWITCHABLE_TARGET
711 extern struct target_cfgloop
*this_target_cfgloop
;
713 #define this_target_cfgloop (&default_target_cfgloop)
716 #define target_avail_regs \
717 (this_target_cfgloop->x_target_avail_regs)
718 #define target_clobbered_regs \
719 (this_target_cfgloop->x_target_clobbered_regs)
720 #define target_res_regs \
721 (this_target_cfgloop->x_target_res_regs)
722 #define target_reg_cost \
723 (this_target_cfgloop->x_target_reg_cost)
724 #define target_spill_cost \
725 (this_target_cfgloop->x_target_spill_cost)
727 /* Register pressure estimation for induction variable optimizations & loop
729 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool, bool);
730 extern void init_set_costs (void);
732 /* Loop optimizer initialization. */
733 extern void loop_optimizer_init (unsigned);
734 extern void loop_optimizer_finalize (function
*);
736 loop_optimizer_finalize ()
738 loop_optimizer_finalize (cfun
);
741 /* Optimization passes. */
744 UAP_UNROLL
= 1, /* Enables unrolling of loops if it seems profitable. */
745 UAP_UNROLL_ALL
= 2 /* Enables unrolling of all loops. */
748 extern void doloop_optimize_loops (void);
749 extern void move_loop_invariants (void);
750 extern vec
<basic_block
> get_loop_hot_path (const struct loop
*loop
);
752 /* Returns the outermost loop of the loop nest that contains LOOP.*/
753 static inline struct loop
*
754 loop_outermost (struct loop
*loop
)
756 unsigned n
= vec_safe_length (loop
->superloops
);
761 return (*loop
->superloops
)[1];
764 extern void record_niter_bound (struct loop
*, const widest_int
&, bool, bool);
765 extern HOST_WIDE_INT
get_estimated_loop_iterations_int (struct loop
*);
766 extern HOST_WIDE_INT
get_max_loop_iterations_int (struct loop
*);
767 extern bool get_estimated_loop_iterations (struct loop
*loop
, widest_int
*nit
);
768 extern bool get_max_loop_iterations (struct loop
*loop
, widest_int
*nit
);
769 extern int bb_loop_depth (const_basic_block
);
771 /* Converts VAL to widest_int. */
773 static inline widest_int
774 gcov_type_to_wide_int (gcov_type val
)
778 a
[0] = (unsigned HOST_WIDE_INT
) val
;
779 /* If HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_WIDEST_INT, avoid shifting by
781 val
>>= HOST_BITS_PER_WIDE_INT
- 1;
783 a
[1] = (unsigned HOST_WIDE_INT
) val
;
785 return widest_int::from_array (a
, 2);
787 #endif /* GCC_CFGLOOP_H */