1 /* Natural loop functions
2 Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
3 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 2, 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 COPYING. If not, write to the Free
19 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
25 #include "basic-block.h"
29 #include "double-int.h"
31 /* Structure to hold decision about unrolling/peeling. */
42 struct lpt_decision GTY (())
44 enum lpt_dec decision;
48 /* The structure describing a bound on number of iterations of a loop. */
50 struct nb_iter_bound GTY ((chain_next ("%h.next")))
52 /* The statement STMT is executed at most ... */
55 /* ... BOUND + 1 times (BOUND must be an unsigned constant).
56 The + 1 is added for the following reasons:
58 a) 0 would otherwise be unused, while we would need to care more about
59 overflows (as MAX + 1 is sometimes produced as the estimate on number
60 of executions of STMT).
61 b) it is consistent with the result of number_of_iterations_exit. */
64 /* True if the statement will cause the loop to be leaved the (at most)
65 BOUND + 1-st time it is executed, that is, all the statements after it
66 are executed at most BOUND times. */
69 /* The next bound in the list. */
70 struct nb_iter_bound *next;
73 /* Description of the loop exit. */
75 struct loop_exit GTY (())
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 typedef struct loop *loop_p;
90 DEF_VEC_ALLOC_P (loop_p, heap);
91 DEF_VEC_ALLOC_P (loop_p, gc);
93 /* An integer estimation of the number of iterations. Estimate_state
94 describes what is the state of the estimation. */
97 /* Estimate was not computed yet. */
99 /* Estimate is ready. */
103 /* Structure to hold information for each natural loop. */
104 struct loop GTY ((chain_next ("%h.next")))
106 /* Index into loops array. */
109 /* Basic block of loop header. */
110 struct basic_block_def *header;
112 /* Basic block of loop latch. */
113 struct basic_block_def *latch;
115 /* For loop unrolling/peeling decision. */
116 struct lpt_decision lpt_decision;
118 /* Number of loop insns. */
121 /* Average number of executed insns per iteration. */
124 /* Number of blocks contained within the loop. */
127 /* Superloops of the loop, starting with the outermost loop. */
128 VEC (loop_p, gc) *superloops;
130 /* The first inner (child) loop or NULL if innermost loop. */
133 /* Link to the next (sibling) loop. */
136 /* Auxiliary info specific to a pass. */
137 PTR GTY ((skip (""))) aux;
139 /* The number of times the latch of the loop is executed.
140 This is an INTEGER_CST or an expression containing symbolic
141 names. Don't access this field directly:
142 number_of_latch_executions computes and caches the computed
143 information in this field. */
146 /* An integer estimation of the number of iterations. Estimate_state
147 describes what is the state of the estimation. */
148 enum loop_estimation estimate_state;
150 /* An integer guaranteed to bound the number of iterations of the loop
152 bool any_upper_bound;
153 double_int nb_iterations_upper_bound;
155 /* An integer giving the expected number of iterations of the loop. */
157 double_int nb_iterations_estimate;
159 /* Upper bound on number of iterations of a loop. */
160 struct nb_iter_bound *bounds;
162 /* Head of the cyclic list of the exits of the loop. */
163 struct loop_exit *exits;
166 /* Flags for state of loop structure. */
169 LOOPS_HAVE_PREHEADERS = 1,
170 LOOPS_HAVE_SIMPLE_LATCHES = 2,
171 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
172 LOOPS_HAVE_RECORDED_EXITS = 8,
173 LOOPS_MAY_HAVE_MULTIPLE_LATCHES = 16,
177 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
178 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
179 #define AVOID_CFG_MODIFICATIONS (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
181 /* Structure to hold CFG information about natural loops within a function. */
182 struct loops GTY (())
184 /* State of loops. */
187 /* Array of the loops. */
188 VEC (loop_p, gc) *larray;
190 /* Maps edges to the list of their descriptions as loop exits. Edges
191 whose sources or destinations have loop_father == NULL (which may
192 happen during the cfg manipulations) should not appear in EXITS. */
193 htab_t GTY((param_is (struct loop_exit))) exits;
195 /* Pointer to root of loop hierarchy tree. */
196 struct loop *tree_root;
199 /* Loop recognition. */
200 extern int flow_loops_find (struct loops *);
201 extern void disambiguate_loops_with_multiple_latches (void);
202 extern void flow_loops_free (struct loops *);
203 extern void flow_loops_dump (FILE *,
204 void (*)(const struct loop *, FILE *, int), int);
205 extern void flow_loop_dump (const struct loop *, FILE *,
206 void (*)(const struct loop *, FILE *, int), int);
207 struct loop *alloc_loop (void);
208 extern void flow_loop_free (struct loop *);
209 int flow_loop_nodes_find (basic_block, struct loop *);
210 void fix_loop_structure (bitmap changed_bbs);
211 void mark_irreducible_loops (void);
212 void release_recorded_exits (void);
213 void record_loop_exits (void);
214 void rescan_loop_exit (edge, bool, bool);
216 /* Loop data structure manipulation/querying. */
217 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
218 extern void flow_loop_tree_node_remove (struct loop *);
219 extern void add_loop (struct loop *, struct loop *);
220 extern bool flow_loop_nested_p (const struct loop *, const struct loop *);
221 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
222 extern struct loop * find_common_loop (struct loop *, struct loop *);
223 struct loop *superloop_at_depth (struct loop *, unsigned);
224 struct eni_weights_d;
225 extern unsigned tree_num_loop_insns (struct loop *, struct eni_weights_d *);
226 extern int num_loop_insns (struct loop *);
227 extern int average_num_loop_insns (struct loop *);
228 extern unsigned get_loop_level (const struct loop *);
229 extern bool loop_exit_edge_p (const struct loop *, edge);
230 extern void mark_loop_exit_edges (void);
232 /* Loops & cfg manipulation. */
233 extern basic_block *get_loop_body (const struct loop *);
234 extern unsigned get_loop_body_with_size (const struct loop *, basic_block *,
236 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
237 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
238 extern VEC (edge, heap) *get_loop_exit_edges (const struct loop *);
239 edge single_exit (const struct loop *);
240 extern unsigned num_loop_branches (const struct loop *);
242 extern edge loop_preheader_edge (const struct loop *);
243 extern edge loop_latch_edge (const struct loop *);
245 extern void add_bb_to_loop (basic_block, struct loop *);
246 extern void remove_bb_from_loops (basic_block);
248 extern void cancel_loop_tree (struct loop *);
249 extern void delete_loop (struct loop *);
253 CP_SIMPLE_PREHEADERS = 1
256 basic_block create_preheader (struct loop *, int);
257 extern void create_preheaders (int);
258 extern void force_single_succ_latches (void);
260 extern void verify_loop_structure (void);
263 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
264 gcov_type expected_loop_iterations_unbounded (const struct loop *);
265 extern unsigned expected_loop_iterations (const struct loop *);
266 extern rtx doloop_condition_get (rtx);
268 void estimate_numbers_of_iterations_loop (struct loop *);
269 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool);
270 bool estimated_loop_iterations (struct loop *, bool, double_int *);
272 /* Loop manipulation. */
273 extern bool can_duplicate_loop_p (struct loop *loop);
275 #define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in
276 duplicate_loop_to_header_edge. */
277 #define DLTHE_RECORD_COPY_NUMBER 2 /* Record copy number in the aux
278 field of newly create BB. */
279 #define DLTHE_FLAG_COMPLETTE_PEEL 4 /* Update frequencies expecting
280 a complete peeling. */
282 extern struct loop * duplicate_loop (struct loop *, struct loop *);
283 extern bool duplicate_loop_to_header_edge (struct loop *, edge,
284 unsigned, sbitmap, edge,
285 VEC (edge, heap) **, int);
286 extern struct loop *loopify (edge, edge,
287 basic_block, edge, edge, bool,
289 struct loop * loop_version (struct loop *, void *,
290 basic_block *, unsigned, unsigned, unsigned, bool);
291 extern bool remove_path (edge);
292 void scale_loop_frequencies (struct loop *, int, int);
294 /* Induction variable analysis. */
296 /* The description of induction variable. The things are a bit complicated
297 due to need to handle subregs and extends. The value of the object described
298 by it can be obtained as follows (all computations are done in extend_mode):
300 Value in i-th iteration is
301 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
303 If first_special is true, the value in the first iteration is
306 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
307 subreg_{mode} (base + i * step)
309 The get_iv_value function can be used to obtain these expressions.
311 ??? Add a third mode field that would specify the mode in that inner
312 computation is done, which would enable it to be different from the
317 /* Its base and step (mode of base and step is supposed to be extend_mode,
318 see the description above). */
321 /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN). */
322 enum rtx_code extend;
324 /* Operations applied in the extended mode. */
327 /* The mode it is extended to. */
328 enum machine_mode extend_mode;
330 /* The mode the variable iterates in. */
331 enum machine_mode mode;
333 /* Whether the first iteration needs to be handled specially. */
334 unsigned first_special : 1;
337 /* The description of an exit from the loop and of the number of iterations
338 till we take the exit. */
342 /* The edge out of the loop. */
345 /* The other edge leading from the condition. */
348 /* True if we are able to say anything about number of iterations of the
352 /* True if the loop iterates the constant number of times. */
355 /* Number of iterations if constant. */
356 unsigned HOST_WIDEST_INT niter;
358 /* Upper bound on the number of iterations. */
359 unsigned HOST_WIDEST_INT niter_max;
361 /* Assumptions under that the rest of the information is valid. */
364 /* Assumptions under that the loop ends before reaching the latch,
365 even if value of niter_expr says otherwise. */
366 rtx noloop_assumptions;
368 /* Condition under that the loop is infinite. */
371 /* Whether the comparison is signed. */
374 /* The mode in that niter_expr should be computed. */
375 enum machine_mode mode;
377 /* The number of iterations of the loop. */
381 extern void iv_analysis_loop_init (struct loop *);
382 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
383 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
384 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
385 extern rtx get_iv_value (struct rtx_iv *, rtx);
386 extern bool biv_p (rtx, rtx);
387 extern void find_simple_exit (struct loop *, struct niter_desc *);
388 extern void iv_analysis_done (void);
389 extern struct df *iv_current_loop_df (void);
391 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
392 extern void free_simple_loop_desc (struct loop *loop);
394 static inline struct niter_desc *
395 simple_loop_desc (struct loop *loop)
397 return (struct niter_desc *) loop->aux;
400 /* Accessors for the loop structures. */
402 /* Returns the loop with index NUM from current_loops. */
404 static inline struct loop *
405 get_loop (unsigned num)
407 return VEC_index (loop_p, current_loops->larray, num);
410 /* Returns the number of superloops of LOOP. */
412 static inline unsigned
413 loop_depth (const struct loop *loop)
415 return VEC_length (loop_p, loop->superloops);
418 /* Returns the immediate superloop of LOOP, or NULL if LOOP is the outermost
421 static inline struct loop *
422 loop_outer (const struct loop *loop)
424 unsigned n = VEC_length (loop_p, loop->superloops);
429 return VEC_index (loop_p, loop->superloops, n - 1);
432 /* Returns the list of loops in current_loops. */
434 static inline VEC (loop_p, gc) *
440 return current_loops->larray;
443 /* Returns the number of loops in current_loops (including the removed
444 ones and the fake loop that forms the root of the loop tree). */
446 static inline unsigned
447 number_of_loops (void)
452 return VEC_length (loop_p, current_loops->larray);
455 /* Loop iterators. */
457 /* Flags for loop iteration. */
461 LI_INCLUDE_ROOT = 1, /* Include the fake root of the loop tree. */
462 LI_FROM_INNERMOST = 2, /* Iterate over the loops in the reverse order,
463 starting from innermost ones. */
464 LI_ONLY_INNERMOST = 4 /* Iterate only over innermost loops. */
467 /* The iterator for loops. */
471 /* The list of loops to visit. */
472 VEC(int,heap) *to_visit;
474 /* The index of the actual loop. */
479 fel_next (loop_iterator *li, loop_p *loop)
483 while (VEC_iterate (int, li->to_visit, li->idx, anum))
486 *loop = get_loop (anum);
491 VEC_free (int, heap, li->to_visit);
496 fel_init (loop_iterator *li, loop_p *loop, unsigned flags)
510 li->to_visit = VEC_alloc (int, heap, number_of_loops ());
511 mn = (flags & LI_INCLUDE_ROOT) ? 0 : 1;
513 if (flags & LI_ONLY_INNERMOST)
515 for (i = 0; VEC_iterate (loop_p, current_loops->larray, i, aloop); i++)
517 && aloop->inner == NULL
519 VEC_quick_push (int, li->to_visit, aloop->num);
521 else if (flags & LI_FROM_INNERMOST)
523 /* Push the loops to LI->TO_VISIT in postorder. */
524 for (aloop = current_loops->tree_root;
525 aloop->inner != NULL;
526 aloop = aloop->inner)
531 if (aloop->num >= mn)
532 VEC_quick_push (int, li->to_visit, aloop->num);
536 for (aloop = aloop->next;
537 aloop->inner != NULL;
538 aloop = aloop->inner)
541 else if (!loop_outer (aloop))
544 aloop = loop_outer (aloop);
549 /* Push the loops to LI->TO_VISIT in preorder. */
550 aloop = current_loops->tree_root;
553 if (aloop->num >= mn)
554 VEC_quick_push (int, li->to_visit, aloop->num);
556 if (aloop->inner != NULL)
557 aloop = aloop->inner;
560 while (aloop != NULL && aloop->next == NULL)
561 aloop = loop_outer (aloop);
572 #define FOR_EACH_LOOP(LI, LOOP, FLAGS) \
573 for (fel_init (&(LI), &(LOOP), FLAGS); \
575 fel_next (&(LI), &(LOOP)))
577 #define FOR_EACH_LOOP_BREAK(LI) \
579 VEC_free (int, heap, (LI)->to_visit); \
583 /* The properties of the target. */
585 extern unsigned target_avail_regs;
586 extern unsigned target_res_regs;
587 extern unsigned target_reg_cost;
588 extern unsigned target_spill_cost;
590 /* Register pressure estimation for induction variable optimizations & loop
592 extern unsigned estimate_reg_pressure_cost (unsigned, unsigned);
593 extern void init_set_costs (void);
595 /* Loop optimizer initialization. */
596 extern void loop_optimizer_init (unsigned);
597 extern void loop_optimizer_finalize (void);
599 /* Optimization passes. */
600 extern void unswitch_loops (void);
604 UAP_PEEL = 1, /* Enables loop peeling. */
605 UAP_UNROLL = 2, /* Enables unrolling of loops if it seems profitable. */
606 UAP_UNROLL_ALL = 4 /* Enables unrolling of all loops. */
609 extern void unroll_and_peel_loops (int);
610 extern void doloop_optimize_loops (void);
611 extern void move_loop_invariants (void);
613 #endif /* GCC_CFGLOOP_H */