1/* Natural loop functions
2   Copyright (C) 1987-2015 Free Software Foundation, Inc.
3
4This file is part of GCC.
5
6GCC is free software; you can redistribute it and/or modify it under
7the terms of the GNU General Public License as published by the Free
8Software Foundation; either version 3, or (at your option) any later
9version.
10
11GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12WARRANTY; without even the implied warranty of MERCHANTABILITY or
13FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14for more details.
15
16You should have received a copy of the GNU General Public License
17along with GCC; see the file COPYING3.  If not see
18<http://www.gnu.org/licenses/>.  */
19
20#ifndef GCC_CFGLOOP_H
21#define GCC_CFGLOOP_H
22
23#include "double-int.h"
24#include "wide-int.h"
25#include "bitmap.h"
26#include "sbitmap.h"
27#include "hashtab.h"
28#include "hash-set.h"
29#include "vec.h"
30#include "machmode.h"
31#include "tm.h"
32#include "hard-reg-set.h"
33#include "input.h"
34#include "function.h"
35#include "cfgloopmanip.h"
36
37/* Structure to hold decision about unrolling/peeling.  */
38enum lpt_dec
39{
40  LPT_NONE,
41  LPT_UNROLL_CONSTANT,
42  LPT_UNROLL_RUNTIME,
43  LPT_UNROLL_STUPID
44};
45
46struct GTY (()) lpt_decision {
47  enum lpt_dec decision;
48  unsigned times;
49};
50
51/* The type of extend applied to an IV.  */
52enum iv_extend_code
53{
54  IV_SIGN_EXTEND,
55  IV_ZERO_EXTEND,
56  IV_UNKNOWN_EXTEND
57};
58
59/* The structure describing a bound on number of iterations of a loop.  */
60
61struct GTY ((chain_next ("%h.next"))) nb_iter_bound {
62  /* The statement STMT is executed at most ...  */
63  gimple stmt;
64
65  /* ... BOUND + 1 times (BOUND must be an unsigned constant).
66     The + 1 is added for the following reasons:
67
68     a) 0 would otherwise be unused, while we would need to care more about
69        overflows (as MAX + 1 is sometimes produced as the estimate on number
70	of executions of STMT).
71     b) it is consistent with the result of number_of_iterations_exit.  */
72  widest_int bound;
73
74  /* True if the statement will cause the loop to be leaved the (at most)
75     BOUND + 1-st time it is executed, that is, all the statements after it
76     are executed at most BOUND times.  */
77  bool is_exit;
78
79  /* The next bound in the list.  */
80  struct nb_iter_bound *next;
81};
82
83/* Description of the loop exit.  */
84
85struct GTY ((for_user)) loop_exit {
86  /* The exit edge.  */
87  edge e;
88
89  /* Previous and next exit in the list of the exits of the loop.  */
90  struct loop_exit *prev;
91  struct loop_exit *next;
92
93  /* Next element in the list of loops from that E exits.  */
94  struct loop_exit *next_e;
95};
96
97struct loop_exit_hasher : ggc_hasher<loop_exit *>
98{
99  typedef edge compare_type;
100
101  static hashval_t hash (loop_exit *);
102  static bool equal (loop_exit *, edge);
103  static void remove (loop_exit *);
104};
105
106typedef struct loop *loop_p;
107
108/* An integer estimation of the number of iterations.  Estimate_state
109   describes what is the state of the estimation.  */
110enum loop_estimation
111{
112  /* Estimate was not computed yet.  */
113  EST_NOT_COMPUTED,
114  /* Estimate is ready.  */
115  EST_AVAILABLE,
116  EST_LAST
117};
118
119/* Structure to hold information for each natural loop.  */
120struct GTY ((chain_next ("%h.next"))) loop {
121  /* Index into loops array.  */
122  int num;
123
124  /* Number of loop insns.  */
125  unsigned ninsns;
126
127  /* Basic block of loop header.  */
128  basic_block header;
129
130  /* Basic block of loop latch.  */
131  basic_block latch;
132
133  /* For loop unrolling/peeling decision.  */
134  struct lpt_decision lpt_decision;
135
136  /* Average number of executed insns per iteration.  */
137  unsigned av_ninsns;
138
139  /* Number of blocks contained within the loop.  */
140  unsigned num_nodes;
141
142  /* Superloops of the loop, starting with the outermost loop.  */
143  vec<loop_p, va_gc> *superloops;
144
145  /* The first inner (child) loop or NULL if innermost loop.  */
146  struct loop *inner;
147
148  /* Link to the next (sibling) loop.  */
149  struct loop *next;
150
151  /* Auxiliary info specific to a pass.  */
152  PTR GTY ((skip (""))) aux;
153
154  /* The number of times the latch of the loop is executed.  This can be an
155     INTEGER_CST, or a symbolic expression representing the number of
156     iterations like "N - 1", or a COND_EXPR containing the runtime
157     conditions under which the number of iterations is non zero.
158
159     Don't access this field directly: number_of_latch_executions
160     computes and caches the computed information in this field.  */
161  tree nb_iterations;
162
163  /* An integer guaranteed to be greater or equal to nb_iterations.  Only
164     valid if any_upper_bound is true.  */
165  widest_int nb_iterations_upper_bound;
166
167  /* An integer giving an estimate on nb_iterations.  Unlike
168     nb_iterations_upper_bound, there is no guarantee that it is at least
169     nb_iterations.  */
170  widest_int nb_iterations_estimate;
171
172  bool any_upper_bound;
173  bool any_estimate;
174
175  /* True if the loop can be parallel.  */
176  bool can_be_parallel;
177
178  /* True if -Waggressive-loop-optimizations warned about this loop
179     already.  */
180  bool warned_aggressive_loop_optimizations;
181
182  /* An integer estimation of the number of iterations.  Estimate_state
183     describes what is the state of the estimation.  */
184  enum loop_estimation estimate_state;
185
186  /* If > 0, an integer, where the user asserted that for any
187     I in [ 0, nb_iterations ) and for any J in
188     [ I, min ( I + safelen, nb_iterations ) ), the Ith and Jth iterations
189     of the loop can be safely evaluated concurrently.  */
190  int safelen;
191
192  /* True if this loop should never be vectorized.  */
193  bool dont_vectorize;
194
195  /* True if we should try harder to vectorize this loop.  */
196  bool force_vectorize;
197
198  /* For SIMD loops, this is a unique identifier of the loop, referenced
199     by IFN_GOMP_SIMD_VF, IFN_GOMP_SIMD_LANE and IFN_GOMP_SIMD_LAST_LANE
200     builtins.  */
201  tree simduid;
202
203  /* Upper bound on number of iterations of a loop.  */
204  struct nb_iter_bound *bounds;
205
206  /* Head of the cyclic list of the exits of the loop.  */
207  struct loop_exit *exits;
208
209  /* Number of iteration analysis data for RTL.  */
210  struct niter_desc *simple_loop_desc;
211
212  /* For sanity checking during loop fixup we record here the former
213     loop header for loops marked for removal.  Note that this prevents
214     the basic-block from being collected but its index can still be
215     reused.  */
216  basic_block former_header;
217};
218
219/* Flags for state of loop structure.  */
220enum
221{
222  LOOPS_HAVE_PREHEADERS = 1,
223  LOOPS_HAVE_SIMPLE_LATCHES = 2,
224  LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
225  LOOPS_HAVE_RECORDED_EXITS = 8,
226  LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16,
227  LOOP_CLOSED_SSA = 32,
228  LOOPS_NEED_FIXUP = 64,
229  LOOPS_HAVE_FALLTHRU_PREHEADERS = 128
230};
231
232#define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
233		      | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
234#define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
235
236/* Structure to hold CFG information about natural loops within a function.  */
237struct GTY (()) loops {
238  /* State of loops.  */
239  int state;
240
241  /* Array of the loops.  */
242  vec<loop_p, va_gc> *larray;
243
244  /* Maps edges to the list of their descriptions as loop exits.  Edges
245     whose sources or destinations have loop_father == NULL (which may
246     happen during the cfg manipulations) should not appear in EXITS.  */
247  hash_table<loop_exit_hasher> *GTY(()) exits;
248
249  /* Pointer to root of loop hierarchy tree.  */
250  struct loop *tree_root;
251};
252
253/* Loop recognition.  */
254bool bb_loop_header_p (basic_block);
255void init_loops_structure (struct function *, struct loops *, unsigned);
256extern struct loops *flow_loops_find (struct loops *);
257extern void disambiguate_loops_with_multiple_latches (void);
258extern void flow_loops_free (struct loops *);
259extern void flow_loops_dump (FILE *,
260			     void (*)(const struct loop *, FILE *, int), int);
261extern void flow_loop_dump (const struct loop *, FILE *,
262			    void (*)(const struct loop *, FILE *, int), int);
263struct loop *alloc_loop (void);
264extern void flow_loop_free (struct loop *);
265int flow_loop_nodes_find (basic_block, struct loop *);
266unsigned fix_loop_structure (bitmap changed_bbs);
267bool mark_irreducible_loops (void);
268void release_recorded_exits (void);
269void record_loop_exits (void);
270void rescan_loop_exit (edge, bool, bool);
271
272/* Loop data structure manipulation/querying.  */
273extern void flow_loop_tree_node_add (struct loop *, struct loop *);
274extern void flow_loop_tree_node_remove (struct loop *);
275extern bool flow_loop_nested_p	(const struct loop *, const struct loop *);
276extern bool flow_bb_inside_loop_p (const struct loop *, const_basic_block);
277extern struct loop * find_common_loop (struct loop *, struct loop *);
278struct loop *superloop_at_depth (struct loop *, unsigned);
279struct eni_weights_d;
280extern int num_loop_insns (const struct loop *);
281extern int average_num_loop_insns (const struct loop *);
282extern unsigned get_loop_level (const struct loop *);
283extern bool loop_exit_edge_p (const struct loop *, const_edge);
284extern bool loop_exits_to_bb_p (struct loop *, basic_block);
285extern bool loop_exits_from_bb_p (struct loop *, basic_block);
286extern void mark_loop_exit_edges (void);
287extern location_t get_loop_location (struct loop *loop);
288
289/* Loops & cfg manipulation.  */
290extern basic_block *get_loop_body (const struct loop *);
291extern unsigned get_loop_body_with_size (const struct loop *, basic_block *,
292					 unsigned);
293extern basic_block *get_loop_body_in_dom_order (const struct loop *);
294extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
295extern basic_block *get_loop_body_in_custom_order (const struct loop *,
296			       int (*) (const void *, const void *));
297
298extern vec<edge> get_loop_exit_edges (const struct loop *);
299extern edge single_exit (const struct loop *);
300extern edge single_likely_exit (struct loop *loop);
301extern unsigned num_loop_branches (const struct loop *);
302
303extern edge loop_preheader_edge (const struct loop *);
304extern edge loop_latch_edge (const struct loop *);
305
306extern void add_bb_to_loop (basic_block, struct loop *);
307extern void remove_bb_from_loops (basic_block);
308
309extern void cancel_loop_tree (struct loop *);
310extern void delete_loop (struct loop *);
311
312
313extern void verify_loop_structure (void);
314
315/* Loop analysis.  */
316extern bool just_once_each_iteration_p (const struct loop *, const_basic_block);
317gcov_type expected_loop_iterations_unbounded (const struct loop *);
318extern unsigned expected_loop_iterations (const struct loop *);
319extern rtx doloop_condition_get (rtx);
320
321void mark_loop_for_removal (loop_p);
322
323/* Induction variable analysis.  */
324
325/* The description of induction variable.  The things are a bit complicated
326   due to need to handle subregs and extends.  The value of the object described
327   by it can be obtained as follows (all computations are done in extend_mode):
328
329   Value in i-th iteration is
330     delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
331
332   If first_special is true, the value in the first iteration is
333     delta + mult * base
334
335   If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
336     subreg_{mode} (base + i * step)
337
338   The get_iv_value function can be used to obtain these expressions.
339
340   ??? Add a third mode field that would specify the mode in that inner
341   computation is done, which would enable it to be different from the
342   outer one?  */
343
344struct rtx_iv
345{
346  /* Its base and step (mode of base and step is supposed to be extend_mode,
347     see the description above).  */
348  rtx base, step;
349
350  /* The type of extend applied to it (IV_SIGN_EXTEND, IV_ZERO_EXTEND,
351     or IV_UNKNOWN_EXTEND).  */
352  enum iv_extend_code extend;
353
354  /* Operations applied in the extended mode.  */
355  rtx delta, mult;
356
357  /* The mode it is extended to.  */
358  machine_mode extend_mode;
359
360  /* The mode the variable iterates in.  */
361  machine_mode mode;
362
363  /* Whether the first iteration needs to be handled specially.  */
364  unsigned first_special : 1;
365};
366
367/* The description of an exit from the loop and of the number of iterations
368   till we take the exit.  */
369
370struct GTY(()) niter_desc
371{
372  /* The edge out of the loop.  */
373  edge out_edge;
374
375  /* The other edge leading from the condition.  */
376  edge in_edge;
377
378  /* True if we are able to say anything about number of iterations of the
379     loop.  */
380  bool simple_p;
381
382  /* True if the loop iterates the constant number of times.  */
383  bool const_iter;
384
385  /* Number of iterations if constant.  */
386  uint64_t niter;
387
388  /* Assumptions under that the rest of the information is valid.  */
389  rtx assumptions;
390
391  /* Assumptions under that the loop ends before reaching the latch,
392     even if value of niter_expr says otherwise.  */
393  rtx noloop_assumptions;
394
395  /* Condition under that the loop is infinite.  */
396  rtx infinite;
397
398  /* Whether the comparison is signed.  */
399  bool signed_p;
400
401  /* The mode in that niter_expr should be computed.  */
402  machine_mode mode;
403
404  /* The number of iterations of the loop.  */
405  rtx niter_expr;
406};
407
408extern void iv_analysis_loop_init (struct loop *);
409extern bool iv_analyze (rtx_insn *, rtx, struct rtx_iv *);
410extern bool iv_analyze_result (rtx_insn *, rtx, struct rtx_iv *);
411extern bool iv_analyze_expr (rtx_insn *, rtx, machine_mode,
412			     struct rtx_iv *);
413extern rtx get_iv_value (struct rtx_iv *, rtx);
414extern bool biv_p (rtx_insn *, rtx);
415extern void find_simple_exit (struct loop *, struct niter_desc *);
416extern void iv_analysis_done (void);
417
418extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
419extern void free_simple_loop_desc (struct loop *loop);
420
421static inline struct niter_desc *
422simple_loop_desc (struct loop *loop)
423{
424  return loop->simple_loop_desc;
425}
426
427/* Accessors for the loop structures.  */
428
429/* Returns the loop with index NUM from FNs loop tree.  */
430
431static inline struct loop *
432get_loop (struct function *fn, unsigned num)
433{
434  return (*loops_for_fn (fn)->larray)[num];
435}
436
437/* Returns the number of superloops of LOOP.  */
438
439static inline unsigned
440loop_depth (const struct loop *loop)
441{
442  return vec_safe_length (loop->superloops);
443}
444
445/* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
446   loop.  */
447
448static inline struct loop *
449loop_outer (const struct loop *loop)
450{
451  unsigned n = vec_safe_length (loop->superloops);
452
453  if (n == 0)
454    return NULL;
455
456  return (*loop->superloops)[n - 1];
457}
458
459/* Returns true if LOOP has at least one exit edge.  */
460
461static inline bool
462loop_has_exit_edges (const struct loop *loop)
463{
464  return loop->exits->next->e != NULL;
465}
466
467/* Returns the list of loops in FN.  */
468
469inline vec<loop_p, va_gc> *
470get_loops (struct function *fn)
471{
472  struct loops *loops = loops_for_fn (fn);
473  if (!loops)
474    return NULL;
475
476  return loops->larray;
477}
478
479/* Returns the number of loops in FN (including the removed
480   ones and the fake loop that forms the root of the loop tree).  */
481
482static inline unsigned
483number_of_loops (struct function *fn)
484{
485  struct loops *loops = loops_for_fn (fn);
486  if (!loops)
487    return 0;
488
489  return vec_safe_length (loops->larray);
490}
491
492/* Returns true if state of the loops satisfies all properties
493   described by FLAGS.  */
494
495static inline bool
496loops_state_satisfies_p (unsigned flags)
497{
498  return (current_loops->state & flags) == flags;
499}
500
501/* Sets FLAGS to the loops state.  */
502
503static inline void
504loops_state_set (unsigned flags)
505{
506  current_loops->state |= flags;
507}
508
509/* Clears FLAGS from the loops state.  */
510
511static inline void
512loops_state_clear (unsigned flags)
513{
514  if (!current_loops)
515    return;
516  current_loops->state &= ~flags;
517}
518
519/* Loop iterators.  */
520
521/* Flags for loop iteration.  */
522
523enum li_flags
524{
525  LI_INCLUDE_ROOT = 1,		/* Include the fake root of the loop tree.  */
526  LI_FROM_INNERMOST = 2,	/* Iterate over the loops in the reverse order,
527				   starting from innermost ones.  */
528  LI_ONLY_INNERMOST = 4		/* Iterate only over innermost loops.  */
529};
530
531/* The iterator for loops.  */
532
533struct loop_iterator
534{
535  loop_iterator (loop_p *loop, unsigned flags);
536  ~loop_iterator ();
537
538  inline loop_p next ();
539
540  /* The list of loops to visit.  */
541  vec<int> to_visit;
542
543  /* The index of the actual loop.  */
544  unsigned idx;
545};
546
547inline loop_p
548loop_iterator::next ()
549{
550  int anum;
551
552  while (this->to_visit.iterate (this->idx, &anum))
553    {
554      this->idx++;
555      loop_p loop = get_loop (cfun, anum);
556      if (loop)
557	return loop;
558    }
559
560  return NULL;
561}
562
563inline
564loop_iterator::loop_iterator (loop_p *loop, unsigned flags)
565{
566  struct loop *aloop;
567  unsigned i;
568  int mn;
569
570  this->idx = 0;
571  if (!current_loops)
572    {
573      this->to_visit.create (0);
574      *loop = NULL;
575      return;
576    }
577
578  this->to_visit.create (number_of_loops (cfun));
579  mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
580
581  if (flags & LI_ONLY_INNERMOST)
582    {
583      for (i = 0; vec_safe_iterate (current_loops->larray, i, &aloop); i++)
584	if (aloop != NULL
585	    && aloop->inner == NULL
586	    && aloop->num >= mn)
587	  this->to_visit.quick_push (aloop->num);
588    }
589  else if (flags & LI_FROM_INNERMOST)
590    {
591      /* Push the loops to LI->TO_VISIT in postorder.  */
592      for (aloop = current_loops->tree_root;
593	   aloop->inner != NULL;
594	   aloop = aloop->inner)
595	continue;
596
597      while (1)
598	{
599	  if (aloop->num >= mn)
600	    this->to_visit.quick_push (aloop->num);
601
602	  if (aloop->next)
603	    {
604	      for (aloop = aloop->next;
605		   aloop->inner != NULL;
606		   aloop = aloop->inner)
607		continue;
608	    }
609	  else if (!loop_outer (aloop))
610	    break;
611	  else
612	    aloop = loop_outer (aloop);
613	}
614    }
615  else
616    {
617      /* Push the loops to LI->TO_VISIT in preorder.  */
618      aloop = current_loops->tree_root;
619      while (1)
620	{
621	  if (aloop->num >= mn)
622	    this->to_visit.quick_push (aloop->num);
623
624	  if (aloop->inner != NULL)
625	    aloop = aloop->inner;
626	  else
627	    {
628	      while (aloop != NULL && aloop->next == NULL)
629		aloop = loop_outer (aloop);
630	      if (aloop == NULL)
631		break;
632	      aloop = aloop->next;
633	    }
634	}
635    }
636
637  *loop = this->next ();
638}
639
640inline
641loop_iterator::~loop_iterator ()
642{
643  this->to_visit.release ();
644}
645
646#define FOR_EACH_LOOP(LOOP, FLAGS) \
647  for (loop_iterator li(&(LOOP), FLAGS); \
648       (LOOP); \
649       (LOOP) = li.next ())
650
651/* The properties of the target.  */
652struct target_cfgloop {
653  /* Number of available registers.  */
654  unsigned x_target_avail_regs;
655
656  /* Number of available registers that are call-clobbered.  */
657  unsigned x_target_clobbered_regs;
658
659  /* Number of registers reserved for temporary expressions.  */
660  unsigned x_target_res_regs;
661
662  /* The cost for register when there still is some reserve, but we are
663     approaching the number of available registers.  */
664  unsigned x_target_reg_cost[2];
665
666  /* The cost for register when we need to spill.  */
667  unsigned x_target_spill_cost[2];
668};
669
670extern struct target_cfgloop default_target_cfgloop;
671#if SWITCHABLE_TARGET
672extern struct target_cfgloop *this_target_cfgloop;
673#else
674#define this_target_cfgloop (&default_target_cfgloop)
675#endif
676
677#define target_avail_regs \
678  (this_target_cfgloop->x_target_avail_regs)
679#define target_clobbered_regs \
680  (this_target_cfgloop->x_target_clobbered_regs)
681#define target_res_regs \
682  (this_target_cfgloop->x_target_res_regs)
683#define target_reg_cost \
684  (this_target_cfgloop->x_target_reg_cost)
685#define target_spill_cost \
686  (this_target_cfgloop->x_target_spill_cost)
687
688/* Register pressure estimation for induction variable optimizations & loop
689   invariant motion.  */
690extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool, bool);
691extern void init_set_costs (void);
692
693/* Loop optimizer initialization.  */
694extern void loop_optimizer_init (unsigned);
695extern void loop_optimizer_finalize (void);
696
697/* Optimization passes.  */
698enum
699{
700  UAP_UNROLL = 1,	/* Enables unrolling of loops if it seems profitable.  */
701  UAP_UNROLL_ALL = 2	/* Enables unrolling of all loops.  */
702};
703
704extern void doloop_optimize_loops (void);
705extern void move_loop_invariants (void);
706extern vec<basic_block> get_loop_hot_path (const struct loop *loop);
707
708/* Returns the outermost loop of the loop nest that contains LOOP.*/
709static inline struct loop *
710loop_outermost (struct loop *loop)
711{
712  unsigned n = vec_safe_length (loop->superloops);
713
714  if (n <= 1)
715    return loop;
716
717  return (*loop->superloops)[1];
718}
719
720extern void record_niter_bound (struct loop *, const widest_int &, bool, bool);
721extern HOST_WIDE_INT get_estimated_loop_iterations_int (struct loop *);
722extern HOST_WIDE_INT get_max_loop_iterations_int (struct loop *);
723extern bool get_estimated_loop_iterations (struct loop *loop, widest_int *nit);
724extern bool get_max_loop_iterations (struct loop *loop, widest_int *nit);
725extern int bb_loop_depth (const_basic_block);
726
727/* Converts VAL to widest_int.  */
728
729static inline widest_int
730gcov_type_to_wide_int (gcov_type val)
731{
732  HOST_WIDE_INT a[2];
733
734  a[0] = (unsigned HOST_WIDE_INT) val;
735  /* If HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_WIDEST_INT, avoid shifting by
736     the size of type.  */
737  val >>= HOST_BITS_PER_WIDE_INT - 1;
738  val >>= 1;
739  a[1] = (unsigned HOST_WIDE_INT) val;
740
741  return widest_int::from_array (a, 2);
742}
743#endif /* GCC_CFGLOOP_H */
744