1 /* Natural loop functions
2 Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
3 2005, 2006, 2007 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 lpt_decision GTY (())
43 enum lpt_dec decision;
47 /* The structure describing a bound on number of iterations of a loop. */
49 struct nb_iter_bound GTY ((chain_next ("%h.next")))
51 /* The statement STMT is executed at most ... */
54 /* ... BOUND + 1 times (BOUND must be an unsigned constant).
55 The + 1 is added for the following reasons:
57 a) 0 would otherwise be unused, while we would need to care more about
58 overflows (as MAX + 1 is sometimes produced as the estimate on number
59 of executions of STMT).
60 b) it is consistent with the result of number_of_iterations_exit. */
63 /* True if the statement will cause the loop to be leaved the (at most)
64 BOUND + 1-st time it is executed, that is, all the statements after it
65 are executed at most BOUND times. */
68 /* The next bound in the list. */
69 struct nb_iter_bound *next;
72 /* Description of the loop exit. */
74 struct loop_exit GTY (())
79 /* Previous and next exit in the list of the exits of the loop. */
80 struct loop_exit *prev;
81 struct loop_exit *next;
83 /* Next element in the list of loops from that E exits. */
84 struct loop_exit *next_e;
87 typedef struct loop *loop_p;
89 DEF_VEC_ALLOC_P (loop_p, heap);
90 DEF_VEC_ALLOC_P (loop_p, gc);
92 /* An integer estimation of the number of iterations. Estimate_state
93 describes what is the state of the estimation. */
96 /* Estimate was not computed yet. */
98 /* Estimate is ready. */
102 /* Structure to hold information for each natural loop. */
103 struct loop GTY ((chain_next ("%h.next")))
105 /* Index into loops array. */
108 /* Basic block of loop header. */
109 struct basic_block_def *header;
111 /* Basic block of loop latch. */
112 struct basic_block_def *latch;
114 /* For loop unrolling/peeling decision. */
115 struct lpt_decision lpt_decision;
117 /* Number of loop insns. */
120 /* Average number of executed insns per iteration. */
123 /* Number of blocks contained within the loop. */
126 /* Superloops of the loop, starting with the outermost loop. */
127 VEC (loop_p, gc) *superloops;
129 /* The first inner (child) loop or NULL if innermost loop. */
132 /* Link to the next (sibling) loop. */
135 /* Auxiliary info specific to a pass. */
136 PTR GTY ((skip (""))) aux;
138 /* The number of times the latch of the loop is executed.
139 This is an INTEGER_CST or an expression containing symbolic
140 names. Don't access this field directly:
141 number_of_latch_executions computes and caches the computed
142 information in this field. */
145 /* An integer estimation of the number of iterations. Estimate_state
146 describes what is the state of the estimation. */
147 enum loop_estimation estimate_state;
149 /* An integer guaranteed to bound the number of iterations of the loop
151 bool any_upper_bound;
152 double_int nb_iterations_upper_bound;
154 /* An integer giving the expected number of iterations of the loop. */
156 double_int nb_iterations_estimate;
158 /* Upper bound on number of iterations of a loop. */
159 struct nb_iter_bound *bounds;
161 /* Head of the cyclic list of the exits of the loop. */
162 struct loop_exit *exits;
165 /* Flags for state of loop structure. */
168 LOOPS_HAVE_PREHEADERS = 1,
169 LOOPS_HAVE_SIMPLE_LATCHES = 2,
170 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
171 LOOPS_HAVE_RECORDED_EXITS = 8,
172 LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16,
176 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
177 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
178 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
180 /* Structure to hold CFG information about natural loops within a function. */
181 struct loops GTY (())
183 /* State of loops. */
186 /* Array of the loops. */
187 VEC (loop_p, gc) *larray;
189 /* Maps edges to the list of their descriptions as loop exits. Edges
190 whose sources or destinations have loop_father == NULL (which may
191 happen during the cfg manipulations) should not appear in EXITS. */
192 htab_t GTY((param_is (struct loop_exit))) exits;
194 /* Pointer to root of loop hierarchy tree. */
195 struct loop *tree_root;
198 /* Loop recognition. */
199 extern int flow_loops_find (struct loops *);
200 extern void disambiguate_loops_with_multiple_latches (void);
201 extern void flow_loops_free (struct loops *);
202 extern void flow_loops_dump (FILE *,
203 void (*)(const struct loop *, FILE *, int), int);
204 extern void flow_loop_dump (const struct loop *, FILE *,
205 void (*)(const struct loop *, FILE *, int), int);
206 struct loop *alloc_loop (void);
207 extern void flow_loop_free (struct loop *);
208 int flow_loop_nodes_find (basic_block, struct loop *);
209 void fix_loop_structure (bitmap changed_bbs);
210 void mark_irreducible_loops (void);
211 void release_recorded_exits (void);
212 void record_loop_exits (void);
213 void rescan_loop_exit (edge, bool, bool);
215 /* Loop data structure manipulation/querying. */
216 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
217 extern void flow_loop_tree_node_remove (struct loop *);
218 extern void add_loop (struct loop *, struct loop *);
219 extern bool flow_loop_nested_p (const struct loop *, const struct loop *);
220 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
221 extern struct loop * find_common_loop (struct loop *, struct loop *);
222 struct loop *superloop_at_depth (struct loop *, unsigned);
223 struct eni_weights_d;
224 extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *);
225 extern int num_loop_insns (struct loop *);
226 extern int average_num_loop_insns (struct loop *);
227 extern unsigned get_loop_level (const struct loop *);
228 extern bool loop_exit_edge_p (const struct loop *, edge);
229 extern void mark_loop_exit_edges (void);
231 /* Loops & cfg manipulation. */
232 extern basic_block *get_loop_body (const struct loop *);
233 extern unsigned get_loop_body_with_size (const struct loop *, basic_block *,
235 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
236 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
237 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
238 edge single_exit (const struct loop *);
239 extern unsigned num_loop_branches (const struct loop *);
241 extern edge loop_preheader_edge (const struct loop *);
242 extern edge loop_latch_edge (const struct loop *);
244 extern void add_bb_to_loop (basic_block, struct loop *);
245 extern void remove_bb_from_loops (basic_block);
247 extern void cancel_loop_tree (struct loop *);
248 extern void delete_loop (struct loop *);
252 CP_SIMPLE_PREHEADERS = 1
255 basic_block create_preheader (struct loop *, int);
256 extern void create_preheaders (int);
257 extern void force_single_succ_latches (void);
259 extern void verify_loop_structure (void);
262 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
263 gcov_type expected_loop_iterations_unbounded (const struct loop *);
264 extern unsigned expected_loop_iterations (const struct loop *);
265 extern rtx doloop_condition_get (rtx);
267 void estimate_numbers_of_iterations_loop (struct loop *);
268 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool);
269 bool estimated_loop_iterations (struct loop *, bool, double_int *);
271 /* Loop manipulation. */
272 extern bool can_duplicate_loop_p (struct loop *loop);
274 #define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in
275 duplicate_loop_to_header_edge. */
276 #define DLTHE_RECORD_COPY_NUMBER 2 /* Record copy number in the aux
277 field of newly create BB. */
278 #define DLTHE_FLAG_COMPLETTE_PEEL 4 /* Update frequencies expecting
279 a complete peeling. */
281 extern struct loop * duplicate_loop (struct loop *, struct loop *);
282 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
283 unsigned, sbitmap, edge,
284 VEC (edge, heap) **, int);
285 extern struct loop *loopify (edge, edge,
286 basic_block, edge, edge, bool,
288 struct loop * loop_version (struct loop *, void *,
289 basic_block *, unsigned, unsigned, unsigned, bool);
290 extern bool remove_path (edge);
291 void scale_loop_frequencies (struct loop *, int, int);
293 /* Induction variable analysis. */
295 /* The description of induction variable. The things are a bit complicated
296 due to need to handle subregs and extends. The value of the object described
297 by it can be obtained as follows (all computations are done in extend_mode):
299 Value in i-th iteration is
300 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
302 If first_special is true, the value in the first iteration is
305 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
306 subreg_{mode} (base + i * step)
308 The get_iv_value function can be used to obtain these expressions.
310 ??? Add a third mode field that would specify the mode in that inner
311 computation is done, which would enable it to be different from the
316 /* Its base and step (mode of base and step is supposed to be extend_mode,
317 see the description above). */
320 /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN). */
321 enum rtx_code extend;
323 /* Operations applied in the extended mode. */
326 /* The mode it is extended to. */
327 enum machine_mode extend_mode;
329 /* The mode the variable iterates in. */
330 enum machine_mode mode;
332 /* Whether the first iteration needs to be handled specially. */
333 unsigned first_special : 1;
336 /* The description of an exit from the loop and of the number of iterations
337 till we take the exit. */
341 /* The edge out of the loop. */
344 /* The other edge leading from the condition. */
347 /* True if we are able to say anything about number of iterations of the
351 /* True if the loop iterates the constant number of times. */
354 /* Number of iterations if constant. */
355 unsigned HOST_WIDEST_INT niter;
357 /* Upper bound on the number of iterations. */
358 unsigned HOST_WIDEST_INT niter_max;
360 /* Assumptions under that the rest of the information is valid. */
363 /* Assumptions under that the loop ends before reaching the latch,
364 even if value of niter_expr says otherwise. */
365 rtx noloop_assumptions;
367 /* Condition under that the loop is infinite. */
370 /* Whether the comparison is signed. */
373 /* The mode in that niter_expr should be computed. */
374 enum machine_mode mode;
376 /* The number of iterations of the loop. */
380 extern void iv_analysis_loop_init (struct loop *);
381 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
382 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
383 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
384 extern rtx get_iv_value (struct rtx_iv *, rtx);
385 extern bool biv_p (rtx, rtx);
386 extern void find_simple_exit (struct loop *, struct niter_desc *);
387 extern void iv_analysis_done (void);
389 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
390 extern void free_simple_loop_desc (struct loop *loop);
392 static inline struct niter_desc *
393 simple_loop_desc (struct loop *loop)
395 return (struct niter_desc *) loop->aux;
398 /* Accessors for the loop structures. */
400 /* Returns the loop with index NUM from current_loops. */
402 static inline struct loop *
403 get_loop (unsigned num)
405 return VEC_index (loop_p, current_loops->larray, num);
408 /* Returns the number of superloops of LOOP. */
410 static inline unsigned
411 loop_depth (const struct loop *loop)
413 return VEC_length (loop_p, loop->superloops);
416 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
419 static inline struct loop *
420 loop_outer (const struct loop *loop)
422 unsigned n = VEC_length (loop_p, loop->superloops);
427 return VEC_index (loop_p, loop->superloops, n - 1);
430 /* Returns the list of loops in current_loops. */
432 static inline VEC (loop_p, gc) *
438 return current_loops->larray;
441 /* Returns the number of loops in current_loops (including the removed
442 ones and the fake loop that forms the root of the loop tree). */
444 static inline unsigned
445 number_of_loops (void)
450 return VEC_length (loop_p, current_loops->larray);
453 /* Loop iterators. */
455 /* Flags for loop iteration. */
459 LI_INCLUDE_ROOT = 1, /* Include the fake root of the loop tree. */
460 LI_FROM_INNERMOST = 2, /* Iterate over the loops in the reverse order,
461 starting from innermost ones. */
462 LI_ONLY_INNERMOST = 4 /* Iterate only over innermost loops. */
465 /* The iterator for loops. */
469 /* The list of loops to visit. */
470 VEC(int,heap) *to_visit;
472 /* The index of the actual loop. */
477 fel_next (loop_iterator *li, loop_p *loop)
481 while (VEC_iterate (int, li->to_visit, li->idx, anum))
484 *loop = get_loop (anum);
489 VEC_free (int, heap, li->to_visit);
494 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
508 li->to_visit = VEC_alloc (int, heap, number_of_loops ());
509 mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
511 if (flags & LI_ONLY_INNERMOST)
513 for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
515 && aloop->inner == NULL
517 VEC_quick_push (int, li->to_visit, aloop->num);
519 else if (flags & LI_FROM_INNERMOST)
521 /* Push the loops to LI->TO_VISIT in postorder. */
522 for (aloop = current_loops->tree_root;
523 aloop->inner != NULL;
524 aloop = aloop->inner)
529 if (aloop->num >= mn)
530 VEC_quick_push (int, li->to_visit, aloop->num);
534 for (aloop = aloop->next;
535 aloop->inner != NULL;
536 aloop = aloop->inner)
539 else if (!loop_outer (aloop))
542 aloop = loop_outer (aloop);
547 /* Push the loops to LI->TO_VISIT in preorder. */
548 aloop = current_loops->tree_root;
551 if (aloop->num >= mn)
552 VEC_quick_push (int, li->to_visit, aloop->num);
554 if (aloop->inner != NULL)
555 aloop = aloop->inner;
558 while (aloop != NULL && aloop->next == NULL)
559 aloop = loop_outer (aloop);
570 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
571 for (fel_init (&(LI), &(LOOP), FLAGS); \
573 fel_next (&(LI), &(LOOP)))
575 #define FOR_EACH_LOOP_BREAK(LI) \
577 VEC_free (int, heap, (LI)->to_visit); \
581 /* The properties of the target. */
583 extern unsigned target_avail_regs;
584 extern unsigned target_res_regs;
585 extern unsigned target_reg_cost;
586 extern unsigned target_spill_cost;
588 /* Register pressure estimation for induction variable optimizations & loop
590 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned);
591 extern void init_set_costs (void);
593 /* Loop optimizer initialization. */
594 extern void loop_optimizer_init (unsigned);
595 extern void loop_optimizer_finalize (void);
597 /* Optimization passes. */
598 extern void unswitch_loops (void);
602 UAP_PEEL = 1, /* Enables loop peeling. */
603 UAP_UNROLL = 2, /* Enables unrolling of loops if it seems profitable. */
604 UAP_UNROLL_ALL = 4 /* Enables unrolling of all loops. */
607 extern void unroll_and_peel_loops (int);
608 extern void doloop_optimize_loops (void);
609 extern void move_loop_invariants (void);
611 #endif /* GCC_CFGLOOP_H */