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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
9 version.
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
14 for more details.
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/>. */
20 #ifndef GCC_CFGLOOP_H
21 #define GCC_CFGLOOP_H
23 #include "bitmap.h"
24 #include "sbitmap.h"
25 #include "function.h"
26 #include "cfgloopmanip.h"
28 /* Structure to hold decision about unrolling/peeling. */
29 enum lpt_dec
31 LPT_NONE,
32 LPT_UNROLL_CONSTANT,
33 LPT_UNROLL_RUNTIME,
34 LPT_UNROLL_STUPID
37 struct GTY (()) lpt_decision {
38 enum lpt_dec decision;
39 unsigned times;
42 /* The type of extend applied to an IV. */
43 enum iv_extend_code
45 IV_SIGN_EXTEND,
46 IV_ZERO_EXTEND,
47 IV_UNKNOWN_EXTEND
50 /* The structure describing a bound on number of iterations of a loop. */
52 struct GTY ((chain_next ("%h.next"))) nb_iter_bound {
53 /* The statement STMT is executed at most ... */
54 gimple stmt;
56 /* ... BOUND + 1 times (BOUND must be an unsigned constant).
57 The + 1 is added for the following reasons:
59 a) 0 would otherwise be unused, while we would need to care more about
60 overflows (as MAX + 1 is sometimes produced as the estimate on number
61 of executions of STMT).
62 b) it is consistent with the result of number_of_iterations_exit. */
63 widest_int bound;
65 /* True if the statement will cause the loop to be leaved the (at most)
66 BOUND + 1-st time it is executed, that is, all the statements after it
67 are executed at most BOUND times. */
68 bool is_exit;
70 /* The next bound in the list. */
71 struct nb_iter_bound *next;
74 /* Description of the loop exit. */
76 struct GTY ((for_user)) loop_exit {
77 /* The exit edge. */
78 edge e;
80 /* Previous and next exit in the list of the exits of the loop. */
81 struct loop_exit *prev;
82 struct loop_exit *next;
84 /* Next element in the list of loops from that E exits. */
85 struct loop_exit *next_e;
88 struct loop_exit_hasher : ggc_ptr_hash<loop_exit>
90 typedef edge compare_type;
92 static hashval_t hash (loop_exit *);
93 static bool equal (loop_exit *, edge);
94 static void remove (loop_exit *);
97 typedef struct loop *loop_p;
99 /* An integer estimation of the number of iterations. Estimate_state
100 describes what is the state of the estimation. */
101 enum loop_estimation
103 /* Estimate was not computed yet. */
104 EST_NOT_COMPUTED,
105 /* Estimate is ready. */
106 EST_AVAILABLE,
107 EST_LAST
110 /* The structure describing non-overflow control induction variable for
111 loop's exit edge. */
112 struct GTY ((chain_next ("%h.next"))) control_iv {
113 tree base;
114 tree step;
115 struct control_iv *next;
118 /* Structure to hold information for each natural loop. */
119 struct GTY ((chain_next ("%h.next"))) loop {
120 /* Index into loops array. */
121 int num;
123 /* Number of loop insns. */
124 unsigned ninsns;
126 /* Basic block of loop header. */
127 basic_block header;
129 /* Basic block of loop latch. */
130 basic_block latch;
132 /* For loop unrolling/peeling decision. */
133 struct lpt_decision lpt_decision;
135 /* Average number of executed insns per iteration. */
136 unsigned av_ninsns;
138 /* Number of blocks contained within the loop. */
139 unsigned num_nodes;
141 /* Superloops of the loop, starting with the outermost loop. */
142 vec<loop_p, va_gc> *superloops;
144 /* The first inner (child) loop or NULL if innermost loop. */
145 struct loop *inner;
147 /* Link to the next (sibling) loop. */
148 struct loop *next;
150 /* Auxiliary info specific to a pass. */
151 PTR GTY ((skip (""))) aux;
153 /* The number of times the latch of the loop is executed. This can be an
154 INTEGER_CST, or a symbolic expression representing the number of
155 iterations like "N - 1", or a COND_EXPR containing the runtime
156 conditions under which the number of iterations is non zero.
158 Don't access this field directly: number_of_latch_executions
159 computes and caches the computed information in this field. */
160 tree nb_iterations;
162 /* An integer guaranteed to be greater or equal to nb_iterations. Only
163 valid if any_upper_bound is true. */
164 widest_int nb_iterations_upper_bound;
166 /* An integer giving an estimate on nb_iterations. Unlike
167 nb_iterations_upper_bound, there is no guarantee that it is at least
168 nb_iterations. */
169 widest_int nb_iterations_estimate;
171 bool any_upper_bound;
172 bool any_estimate;
174 /* True if the loop can be parallel. */
175 bool can_be_parallel;
177 /* True if -Waggressive-loop-optimizations warned about this loop
178 already. */
179 bool warned_aggressive_loop_optimizations;
181 /* An integer estimation of the number of iterations. Estimate_state
182 describes what is the state of the estimation. */
183 enum loop_estimation estimate_state;
185 /* If > 0, an integer, where the user asserted that for any
186 I in [ 0, nb_iterations ) and for any J in
187 [ I, min ( I + safelen, nb_iterations ) ), the Ith and Jth iterations
188 of the loop can be safely evaluated concurrently. */
189 int safelen;
191 /* True if this loop should never be vectorized. */
192 bool dont_vectorize;
194 /* True if we should try harder to vectorize this loop. */
195 bool force_vectorize;
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
199 builtins. */
200 tree simduid;
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
217 reused. */
218 basic_block former_header;
221 /* Flags for state of loop structure. */
222 enum
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. */
241 int state;
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 (void);
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);
281 struct eni_weights_d;
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 *,
294 unsigned);
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 /* Loop analysis. */
318 extern bool just_once_each_iteration_p (const struct loop *, const_basic_block);
319 gcov_type expected_loop_iterations_unbounded (const struct loop *);
320 extern unsigned expected_loop_iterations (const struct loop *);
321 extern rtx doloop_condition_get (rtx);
323 void mark_loop_for_removal (loop_p);
325 /* Induction variable analysis. */
327 /* The description of induction variable. The things are a bit complicated
328 due to need to handle subregs and extends. The value of the object described
329 by it can be obtained as follows (all computations are done in extend_mode):
331 Value in i-th iteration is
332 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
334 If first_special is true, the value in the first iteration is
335 delta + mult * base
337 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
338 subreg_{mode} (base + i * step)
340 The get_iv_value function can be used to obtain these expressions.
342 ??? Add a third mode field that would specify the mode in that inner
343 computation is done, which would enable it to be different from the
344 outer one? */
346 struct rtx_iv
348 /* Its base and step (mode of base and step is supposed to be extend_mode,
349 see the description above). */
350 rtx base, step;
352 /* The type of extend applied to it (IV_SIGN_EXTEND, IV_ZERO_EXTEND,
353 or IV_UNKNOWN_EXTEND). */
354 enum iv_extend_code extend;
356 /* Operations applied in the extended mode. */
357 rtx delta, mult;
359 /* The mode it is extended to. */
360 machine_mode extend_mode;
362 /* The mode the variable iterates in. */
363 machine_mode mode;
365 /* Whether the first iteration needs to be handled specially. */
366 unsigned first_special : 1;
369 /* The description of an exit from the loop and of the number of iterations
370 till we take the exit. */
372 struct GTY(()) niter_desc
374 /* The edge out of the loop. */
375 edge out_edge;
377 /* The other edge leading from the condition. */
378 edge in_edge;
380 /* True if we are able to say anything about number of iterations of the
381 loop. */
382 bool simple_p;
384 /* True if the loop iterates the constant number of times. */
385 bool const_iter;
387 /* Number of iterations if constant. */
388 uint64_t niter;
390 /* Assumptions under that the rest of the information is valid. */
391 rtx assumptions;
393 /* Assumptions under that the loop ends before reaching the latch,
394 even if value of niter_expr says otherwise. */
395 rtx noloop_assumptions;
397 /* Condition under that the loop is infinite. */
398 rtx infinite;
400 /* Whether the comparison is signed. */
401 bool signed_p;
403 /* The mode in that niter_expr should be computed. */
404 machine_mode mode;
406 /* The number of iterations of the loop. */
407 rtx niter_expr;
410 extern void iv_analysis_loop_init (struct loop *);
411 extern bool iv_analyze (rtx_insn *, rtx, struct rtx_iv *);
412 extern bool iv_analyze_result (rtx_insn *, rtx, struct rtx_iv *);
413 extern bool iv_analyze_expr (rtx_insn *, rtx, machine_mode,
414 struct rtx_iv *);
415 extern rtx get_iv_value (struct rtx_iv *, rtx);
416 extern bool biv_p (rtx_insn *, rtx);
417 extern void find_simple_exit (struct loop *, struct niter_desc *);
418 extern void iv_analysis_done (void);
420 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
421 extern void free_simple_loop_desc (struct loop *loop);
423 static inline struct niter_desc *
424 simple_loop_desc (struct loop *loop)
426 return loop->simple_loop_desc;
429 /* Accessors for the loop structures. */
431 /* Returns the loop with index NUM from FNs loop tree. */
433 static inline struct loop *
434 get_loop (struct function *fn, unsigned num)
436 return (*loops_for_fn (fn)->larray)[num];
439 /* Returns the number of superloops of LOOP. */
441 static inline unsigned
442 loop_depth (const struct loop *loop)
444 return vec_safe_length (loop->superloops);
447 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
448 loop. */
450 static inline struct loop *
451 loop_outer (const struct loop *loop)
453 unsigned n = vec_safe_length (loop->superloops);
455 if (n == 0)
456 return NULL;
458 return (*loop->superloops)[n - 1];
461 /* Returns true if LOOP has at least one exit edge. */
463 static inline bool
464 loop_has_exit_edges (const struct loop *loop)
466 return loop->exits->next->e != NULL;
469 /* Returns the list of loops in FN. */
471 inline vec<loop_p, va_gc> *
472 get_loops (struct function *fn)
474 struct loops *loops = loops_for_fn (fn);
475 if (!loops)
476 return NULL;
478 return loops->larray;
481 /* Returns the number of loops in FN (including the removed
482 ones and the fake loop that forms the root of the loop tree). */
484 static inline unsigned
485 number_of_loops (struct function *fn)
487 struct loops *loops = loops_for_fn (fn);
488 if (!loops)
489 return 0;
491 return vec_safe_length (loops->larray);
494 /* Returns true if state of the loops satisfies all properties
495 described by FLAGS. */
497 static inline bool
498 loops_state_satisfies_p (unsigned flags)
500 return (current_loops->state & flags) == flags;
503 /* Sets FLAGS to the loops state. */
505 static inline void
506 loops_state_set (unsigned flags)
508 current_loops->state |= flags;
511 /* Clears FLAGS from the loops state. */
513 static inline void
514 loops_state_clear (unsigned flags)
516 if (!current_loops)
517 return;
518 current_loops->state &= ~flags;
521 /* Loop iterators. */
523 /* Flags for loop iteration. */
525 enum li_flags
527 LI_INCLUDE_ROOT = 1, /* Include the fake root of the loop tree. */
528 LI_FROM_INNERMOST = 2, /* Iterate over the loops in the reverse order,
529 starting from innermost ones. */
530 LI_ONLY_INNERMOST = 4 /* Iterate only over innermost loops. */
533 /* The iterator for loops. */
535 struct loop_iterator
537 loop_iterator (loop_p *loop, unsigned flags);
538 ~loop_iterator ();
540 inline loop_p next ();
542 /* The list of loops to visit. */
543 vec<int> to_visit;
545 /* The index of the actual loop. */
546 unsigned idx;
549 inline loop_p
550 loop_iterator::next ()
552 int anum;
554 while (this->to_visit.iterate (this->idx, &anum))
556 this->idx++;
557 loop_p loop = get_loop (cfun, anum);
558 if (loop)
559 return loop;
562 return NULL;
565 inline
566 loop_iterator::loop_iterator (loop_p *loop, unsigned flags)
568 struct loop *aloop;
569 unsigned i;
570 int mn;
572 this->idx = 0;
573 if (!current_loops)
575 this->to_visit.create (0);
576 *loop = NULL;
577 return;
580 this->to_visit.create (number_of_loops (cfun));
581 mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
583 if (flags & LI_ONLY_INNERMOST)
585 for (i = 0; vec_safe_iterate (current_loops->larray, i, &aloop); i++)
586 if (aloop != NULL
587 && aloop->inner == NULL
588 && aloop->num >= mn)
589 this->to_visit.quick_push (aloop->num);
591 else if (flags & LI_FROM_INNERMOST)
593 /* Push the loops to LI->TO_VISIT in postorder. */
594 for (aloop = current_loops->tree_root;
595 aloop->inner != NULL;
596 aloop = aloop->inner)
597 continue;
599 while (1)
601 if (aloop->num >= mn)
602 this->to_visit.quick_push (aloop->num);
604 if (aloop->next)
606 for (aloop = aloop->next;
607 aloop->inner != NULL;
608 aloop = aloop->inner)
609 continue;
611 else if (!loop_outer (aloop))
612 break;
613 else
614 aloop = loop_outer (aloop);
617 else
619 /* Push the loops to LI->TO_VISIT in preorder. */
620 aloop = current_loops->tree_root;
621 while (1)
623 if (aloop->num >= mn)
624 this->to_visit.quick_push (aloop->num);
626 if (aloop->inner != NULL)
627 aloop = aloop->inner;
628 else
630 while (aloop != NULL && aloop->next == NULL)
631 aloop = loop_outer (aloop);
632 if (aloop == NULL)
633 break;
634 aloop = aloop->next;
639 *loop = this->next ();
642 inline
643 loop_iterator::~loop_iterator ()
645 this->to_visit.release ();
648 #define FOR_EACH_LOOP(LOOP, FLAGS) \
649 for (loop_iterator li(&(LOOP), FLAGS); \
650 (LOOP); \
651 (LOOP) = li.next ())
653 /* The properties of the target. */
654 struct target_cfgloop {
655 /* Number of available registers. */
656 unsigned x_target_avail_regs;
658 /* Number of available registers that are call-clobbered. */
659 unsigned x_target_clobbered_regs;
661 /* Number of registers reserved for temporary expressions. */
662 unsigned x_target_res_regs;
664 /* The cost for register when there still is some reserve, but we are
665 approaching the number of available registers. */
666 unsigned x_target_reg_cost[2];
668 /* The cost for register when we need to spill. */
669 unsigned x_target_spill_cost[2];
672 extern struct target_cfgloop default_target_cfgloop;
673 #if SWITCHABLE_TARGET
674 extern struct target_cfgloop *this_target_cfgloop;
675 #else
676 #define this_target_cfgloop (&default_target_cfgloop)
677 #endif
679 #define target_avail_regs \
680 (this_target_cfgloop->x_target_avail_regs)
681 #define target_clobbered_regs \
682 (this_target_cfgloop->x_target_clobbered_regs)
683 #define target_res_regs \
684 (this_target_cfgloop->x_target_res_regs)
685 #define target_reg_cost \
686 (this_target_cfgloop->x_target_reg_cost)
687 #define target_spill_cost \
688 (this_target_cfgloop->x_target_spill_cost)
690 /* Register pressure estimation for induction variable optimizations & loop
691 invariant motion. */
692 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool, bool);
693 extern void init_set_costs (void);
695 /* Loop optimizer initialization. */
696 extern void loop_optimizer_init (unsigned);
697 extern void loop_optimizer_finalize (void);
699 /* Optimization passes. */
700 enum
702 UAP_UNROLL = 1, /* Enables unrolling of loops if it seems profitable. */
703 UAP_UNROLL_ALL = 2 /* Enables unrolling of all loops. */
706 extern void doloop_optimize_loops (void);
707 extern void move_loop_invariants (void);
708 extern vec<basic_block> get_loop_hot_path (const struct loop *loop);
710 /* Returns the outermost loop of the loop nest that contains LOOP.*/
711 static inline struct loop *
712 loop_outermost (struct loop *loop)
714 unsigned n = vec_safe_length (loop->superloops);
716 if (n <= 1)
717 return loop;
719 return (*loop->superloops)[1];
722 extern void record_niter_bound (struct loop *, const widest_int &, bool, bool);
723 extern HOST_WIDE_INT get_estimated_loop_iterations_int (struct loop *);
724 extern HOST_WIDE_INT get_max_loop_iterations_int (struct loop *);
725 extern bool get_estimated_loop_iterations (struct loop *loop, widest_int *nit);
726 extern bool get_max_loop_iterations (struct loop *loop, widest_int *nit);
727 extern int bb_loop_depth (const_basic_block);
729 /* Converts VAL to widest_int. */
731 static inline widest_int
732 gcov_type_to_wide_int (gcov_type val)
734 HOST_WIDE_INT a[2];
736 a[0] = (unsigned HOST_WIDE_INT) val;
737 /* If HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_WIDEST_INT, avoid shifting by
738 the size of type. */
739 val >>= HOST_BITS_PER_WIDE_INT - 1;
740 val >>= 1;
741 a[1] = (unsigned HOST_WIDE_INT) val;
743 return widest_int::from_array (a, 2);
745 #endif /* GCC_CFGLOOP_H */