1 /* Natural loop functions
2 Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
3 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 3, or (at your option) any later
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
24 #include "basic-block.h"
28 #include "double-int.h"
30 /* Structure to hold decision about unrolling/peeling. */
41 struct GTY (()) lpt_decision {
42 enum lpt_dec decision;
46 /* The structure describing a bound on number of iterations of a loop. */
48 struct GTY ((chain_next ("%h.next"))) nb_iter_bound {
49 /* The statement STMT is executed at most ... */
52 /* ... BOUND + 1 times (BOUND must be an unsigned constant).
53 The + 1 is added for the following reasons:
55 a) 0 would otherwise be unused, while we would need to care more about
56 overflows (as MAX + 1 is sometimes produced as the estimate on number
57 of executions of STMT).
58 b) it is consistent with the result of number_of_iterations_exit. */
61 /* True if the statement will cause the loop to be leaved the (at most)
62 BOUND + 1-st time it is executed, that is, all the statements after it
63 are executed at most BOUND times. */
66 /* The next bound in the list. */
67 struct nb_iter_bound *next;
70 /* Description of the loop exit. */
72 struct GTY (()) loop_exit {
76 /* Previous and next exit in the list of the exits of the loop. */
77 struct loop_exit *prev;
78 struct loop_exit *next;
80 /* Next element in the list of loops from that E exits. */
81 struct loop_exit *next_e;
84 typedef struct loop *loop_p;
86 DEF_VEC_ALLOC_P (loop_p, heap);
87 DEF_VEC_ALLOC_P (loop_p, gc);
89 /* An integer estimation of the number of iterations. Estimate_state
90 describes what is the state of the estimation. */
93 /* Estimate was not computed yet. */
95 /* Estimate is ready. */
99 /* Structure to hold information for each natural loop. */
100 struct GTY ((chain_next ("%h.next"))) loop {
101 /* Index into loops array. */
104 /* Number of loop insns. */
107 /* Basic block of loop header. */
108 struct basic_block_def *header;
110 /* Basic block of loop latch. */
111 struct basic_block_def *latch;
113 /* For loop unrolling/peeling decision. */
114 struct lpt_decision lpt_decision;
116 /* Average number of executed insns per iteration. */
119 /* Number of blocks contained within the loop. */
122 /* Superloops of the loop, starting with the outermost loop. */
123 VEC (loop_p, gc) *superloops;
125 /* The first inner (child) loop or NULL if innermost loop. */
128 /* Link to the next (sibling) loop. */
131 /* Auxiliary info specific to a pass. */
132 PTR GTY ((skip (""))) aux;
134 /* The number of times the latch of the loop is executed.
135 This is an INTEGER_CST or an expression containing symbolic
136 names. Don't access this field directly:
137 number_of_latch_executions computes and caches the computed
138 information in this field. */
141 /* An integer guaranteed to bound the number of iterations of the loop
143 double_int nb_iterations_upper_bound;
145 /* An integer giving the expected number of iterations of the loop. */
146 double_int nb_iterations_estimate;
148 bool any_upper_bound;
151 /* An integer estimation of the number of iterations. Estimate_state
152 describes what is the state of the estimation. */
153 enum loop_estimation estimate_state;
155 /* Upper bound on number of iterations of a loop. */
156 struct nb_iter_bound *bounds;
158 /* Head of the cyclic list of the exits of the loop. */
159 struct loop_exit *exits;
162 /* Flags for state of loop structure. */
165 LOOPS_HAVE_PREHEADERS = 1,
166 LOOPS_HAVE_SIMPLE_LATCHES = 2,
167 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
168 LOOPS_HAVE_RECORDED_EXITS = 8,
169 LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16,
170 LOOP_CLOSED_SSA = 32,
171 LOOPS_NEED_FIXUP = 64,
172 LOOPS_HAVE_FALLTHRU_PREHEADERS = 128
175 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
176 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
177 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
179 /* Structure to hold CFG information about natural loops within a function. */
180 struct GTY (()) loops {
181 /* State of loops. */
184 /* Array of the loops. */
185 VEC (loop_p, gc) *larray;
187 /* Maps edges to the list of their descriptions as loop exits. Edges
188 whose sources or destinations have loop_father == NULL (which may
189 happen during the cfg manipulations) should not appear in EXITS. */
190 htab_t GTY((param_is (struct loop_exit))) exits;
192 /* Pointer to root of loop hierarchy tree. */
193 struct loop *tree_root;
196 /* Loop recognition. */
197 extern int flow_loops_find (struct loops *);
198 extern void disambiguate_loops_with_multiple_latches (void);
199 extern void flow_loops_free (struct loops *);
200 extern void flow_loops_dump (FILE *,
201 void (*)(const struct loop *, FILE *, int), int);
202 extern void flow_loop_dump (const struct loop *, FILE *,
203 void (*)(const struct loop *, FILE *, int), int);
204 struct loop *alloc_loop (void);
205 extern void flow_loop_free (struct loop *);
206 int flow_loop_nodes_find (basic_block, struct loop *);
207 void fix_loop_structure (bitmap changed_bbs);
208 void mark_irreducible_loops (void);
209 void release_recorded_exits (void);
210 void record_loop_exits (void);
211 void rescan_loop_exit (edge, bool, bool);
213 /* Loop data structure manipulation/querying. */
214 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
215 extern void flow_loop_tree_node_remove (struct loop *);
216 extern void add_loop (struct loop *, struct loop *);
217 extern bool flow_loop_nested_p (const struct loop *, const struct loop *);
218 extern bool flow_bb_inside_loop_p (const struct loop *, const_basic_block);
219 extern struct loop * find_common_loop (struct loop *, struct loop *);
220 struct loop *superloop_at_depth (struct loop *, unsigned);
221 struct eni_weights_d;
222 extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *);
223 extern int num_loop_insns (const struct loop *);
224 extern int average_num_loop_insns (const struct loop *);
225 extern unsigned get_loop_level (const struct loop *);
226 extern bool loop_exit_edge_p (const struct loop *, const_edge);
227 extern bool is_loop_exit (struct loop *, basic_block);
228 extern void mark_loop_exit_edges (void);
230 /* Loops & cfg manipulation. */
231 extern basic_block *get_loop_body (const struct loop *);
232 extern unsigned get_loop_body_with_size (const struct loop *, basic_block *,
234 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
235 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
236 extern basic_block *get_loop_body_in_custom_order (const struct loop *,
237 int (*) (const void *, const void *));
239 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
240 edge single_exit (const struct loop *);
241 extern unsigned num_loop_branches (const struct loop *);
243 extern edge loop_preheader_edge (const struct loop *);
244 extern edge loop_latch_edge (const struct loop *);
246 extern void add_bb_to_loop (basic_block, struct loop *);
247 extern void remove_bb_from_loops (basic_block);
249 extern void cancel_loop_tree (struct loop *);
250 extern void delete_loop (struct loop *);
254 CP_SIMPLE_PREHEADERS = 1,
255 CP_FALLTHRU_PREHEADERS = 2
258 basic_block create_preheader (struct loop *, int);
259 extern void create_preheaders (int);
260 extern void force_single_succ_latches (void);
262 extern void verify_loop_structure (void);
265 extern bool just_once_each_iteration_p (const struct loop *, const_basic_block);
266 gcov_type expected_loop_iterations_unbounded (const struct loop *);
267 extern unsigned expected_loop_iterations (const struct loop *);
268 extern rtx doloop_condition_get (rtx);
270 void estimate_numbers_of_iterations_loop (struct loop *);
271 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool);
272 bool estimated_loop_iterations (struct loop *, bool, double_int *);
274 /* Loop manipulation. */
275 extern bool can_duplicate_loop_p (const struct loop *loop);
277 #define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in
278 duplicate_loop_to_header_edge. */
279 #define DLTHE_RECORD_COPY_NUMBER 2 /* Record copy number in the aux
280 field of newly create BB. */
281 #define DLTHE_FLAG_COMPLETTE_PEEL 4 /* Update frequencies expecting
282 a complete peeling. */
284 extern edge create_empty_if_region_on_edge (edge, tree);
285 extern struct loop *create_empty_loop_on_edge (edge, tree, tree, tree, tree,
286 tree *, struct loop *);
287 extern struct loop * duplicate_loop (struct loop *, struct loop *);
288 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
289 unsigned, sbitmap, edge,
290 VEC (edge, heap) **, int);
291 extern struct loop *loopify (edge, edge,
292 basic_block, edge, edge, bool,
294 struct loop * loop_version (struct loop *, void *,
295 basic_block *, unsigned, unsigned, unsigned, bool);
296 extern bool remove_path (edge);
297 void scale_loop_frequencies (struct loop *, int, int);
299 /* Induction variable analysis. */
301 /* The description of induction variable. The things are a bit complicated
302 due to need to handle subregs and extends. The value of the object described
303 by it can be obtained as follows (all computations are done in extend_mode):
305 Value in i-th iteration is
306 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
308 If first_special is true, the value in the first iteration is
311 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
312 subreg_{mode} (base + i * step)
314 The get_iv_value function can be used to obtain these expressions.
316 ??? Add a third mode field that would specify the mode in that inner
317 computation is done, which would enable it to be different from the
322 /* Its base and step (mode of base and step is supposed to be extend_mode,
323 see the description above). */
326 /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN). */
327 enum rtx_code extend;
329 /* Operations applied in the extended mode. */
332 /* The mode it is extended to. */
333 enum machine_mode extend_mode;
335 /* The mode the variable iterates in. */
336 enum machine_mode mode;
338 /* Whether the first iteration needs to be handled specially. */
339 unsigned first_special : 1;
342 /* The description of an exit from the loop and of the number of iterations
343 till we take the exit. */
347 /* The edge out of the loop. */
350 /* The other edge leading from the condition. */
353 /* True if we are able to say anything about number of iterations of the
357 /* True if the loop iterates the constant number of times. */
360 /* Number of iterations if constant. */
361 unsigned HOST_WIDEST_INT niter;
363 /* Upper bound on the number of iterations. */
364 unsigned HOST_WIDEST_INT niter_max;
366 /* Assumptions under that the rest of the information is valid. */
369 /* Assumptions under that the loop ends before reaching the latch,
370 even if value of niter_expr says otherwise. */
371 rtx noloop_assumptions;
373 /* Condition under that the loop is infinite. */
376 /* Whether the comparison is signed. */
379 /* The mode in that niter_expr should be computed. */
380 enum machine_mode mode;
382 /* The number of iterations of the loop. */
386 extern void iv_analysis_loop_init (struct loop *);
387 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
388 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
389 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
390 extern rtx get_iv_value (struct rtx_iv *, rtx);
391 extern bool biv_p (rtx, rtx);
392 extern void find_simple_exit (struct loop *, struct niter_desc *);
393 extern void iv_analysis_done (void);
395 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
396 extern void free_simple_loop_desc (struct loop *loop);
398 static inline struct niter_desc *
399 simple_loop_desc (struct loop *loop)
401 return (struct niter_desc *) loop->aux;
404 /* Accessors for the loop structures. */
406 /* Returns the loop with index NUM from current_loops. */
408 static inline struct loop *
409 get_loop (unsigned num)
411 return VEC_index (loop_p, current_loops->larray, num);
414 /* Returns the number of superloops of LOOP. */
416 static inline unsigned
417 loop_depth (const struct loop *loop)
419 return VEC_length (loop_p, loop->superloops);
422 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
425 static inline struct loop *
426 loop_outer (const struct loop *loop)
428 unsigned n = VEC_length (loop_p, loop->superloops);
433 return VEC_index (loop_p, loop->superloops, n - 1);
436 /* Returns the list of loops in current_loops. */
438 static inline VEC (loop_p, gc) *
444 return current_loops->larray;
447 /* Returns the number of loops in current_loops (including the removed
448 ones and the fake loop that forms the root of the loop tree). */
450 static inline unsigned
451 number_of_loops (void)
456 return VEC_length (loop_p, current_loops->larray);
459 /* Returns true if state of the loops satisfies all properties
460 described by FLAGS. */
463 loops_state_satisfies_p (unsigned flags)
465 return (current_loops->state & flags) == flags;
468 /* Sets FLAGS to the loops state. */
471 loops_state_set (unsigned flags)
473 current_loops->state |= flags;
476 /* Clears FLAGS from the loops state. */
479 loops_state_clear (unsigned flags)
483 current_loops->state &= ~flags;
486 /* Loop iterators. */
488 /* Flags for loop iteration. */
492 LI_INCLUDE_ROOT = 1, /* Include the fake root of the loop tree. */
493 LI_FROM_INNERMOST = 2, /* Iterate over the loops in the reverse order,
494 starting from innermost ones. */
495 LI_ONLY_INNERMOST = 4 /* Iterate only over innermost loops. */
498 /* The iterator for loops. */
502 /* The list of loops to visit. */
503 VEC(int,heap) *to_visit;
505 /* The index of the actual loop. */
510 fel_next (loop_iterator *li, loop_p *loop)
514 while (VEC_iterate (int, li->to_visit, li->idx, anum))
517 *loop = get_loop (anum);
522 VEC_free (int, heap, li->to_visit);
527 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
541 li->to_visit = VEC_alloc (int, heap, number_of_loops ());
542 mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
544 if (flags & LI_ONLY_INNERMOST)
546 for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
548 && aloop->inner == NULL
550 VEC_quick_push (int, li->to_visit, aloop->num);
552 else if (flags & LI_FROM_INNERMOST)
554 /* Push the loops to LI->TO_VISIT in postorder. */
555 for (aloop = current_loops->tree_root;
556 aloop->inner != NULL;
557 aloop = aloop->inner)
562 if (aloop->num >= mn)
563 VEC_quick_push (int, li->to_visit, aloop->num);
567 for (aloop = aloop->next;
568 aloop->inner != NULL;
569 aloop = aloop->inner)
572 else if (!loop_outer (aloop))
575 aloop = loop_outer (aloop);
580 /* Push the loops to LI->TO_VISIT in preorder. */
581 aloop = current_loops->tree_root;
584 if (aloop->num >= mn)
585 VEC_quick_push (int, li->to_visit, aloop->num);
587 if (aloop->inner != NULL)
588 aloop = aloop->inner;
591 while (aloop != NULL && aloop->next == NULL)
592 aloop = loop_outer (aloop);
603 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
604 for (fel_init (&(LI), &(LOOP), FLAGS); \
606 fel_next (&(LI), &(LOOP)))
608 #define FOR_EACH_LOOP_BREAK(LI) \
610 VEC_free (int, heap, (LI)->to_visit); \
614 /* The properties of the target. */
616 extern unsigned target_avail_regs;
617 extern unsigned target_res_regs;
618 extern unsigned target_reg_cost [2];
619 extern unsigned target_spill_cost [2];
621 /* Register pressure estimation for induction variable optimizations & loop
623 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned, bool);
624 extern void init_set_costs (void);
626 /* Loop optimizer initialization. */
627 extern void loop_optimizer_init (unsigned);
628 extern void loop_optimizer_finalize (void);
630 /* Optimization passes. */
631 extern void unswitch_loops (void);
635 UAP_PEEL = 1, /* Enables loop peeling. */
636 UAP_UNROLL = 2, /* Enables unrolling of loops if it seems profitable. */
637 UAP_UNROLL_ALL = 4 /* Enables unrolling of all loops. */
640 extern void unroll_and_peel_loops (int);
641 extern void doloop_optimize_loops (void);
642 extern void move_loop_invariants (void);
644 #endif /* GCC_CFGLOOP_H */