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 /* Structure to hold decision about unrolling/peeling. */
42 enum lpt_dec decision
;
46 /* The structure describing a bound on number of iterations of a loop. */
50 tree bound
; /* The expression whose value is an upper bound on the
51 number of executions of anything after ... */
52 tree at_stmt
; /* ... this statement during one execution of loop. */
53 tree additional
; /* A conjunction of conditions the operands of BOUND
54 satisfy. The additional information about the value
55 of the bound may be derived from it. */
56 struct nb_iter_bound
*next
;
57 /* The next bound in a list. */
60 /* Structure to hold information for each natural loop. */
63 /* Index into loops array. */
66 /* Basic block of loop header. */
69 /* Basic block of loop latch. */
72 /* For loop unrolling/peeling decision. */
73 struct lpt_decision lpt_decision
;
75 /* Number of loop insns. */
78 /* Average number of executed insns per iteration. */
81 /* The first block in the loop. This is not necessarily the same as
85 /* The last block in the loop. This is not necessarily the same as
89 /* Number of blocks contained within the loop. */
92 /* The loop nesting depth. */
95 /* Superloops of the loop. */
98 /* The height of the loop (enclosed loop levels) within the loop
102 /* The outer (parent) loop or NULL if outermost loop. */
105 /* The first inner (child) loop or NULL if innermost loop. */
108 /* Link to the next (sibling) loop. */
111 /* Loop that is copy of this loop. */
114 /* Nonzero if the loop is invalid (e.g., contains setjmp.). */
117 /* Auxiliary info specific to a pass. */
120 /* The following are currently used by loop.c but they are likely to
121 disappear when loop.c is replaced and removed. */
123 /* The NOTE_INSN_LOOP_BEG. */
126 /* The NOTE_INSN_LOOP_END. */
129 /* For a rotated loop that is entered near the bottom,
130 this is the label at the top. Otherwise it is zero. */
133 /* Place in the loop where control enters. */
136 /* The position where to sink insns out of the loop. */
139 /* List of all LABEL_REFs which refer to code labels outside the
140 loop. Used by routines that need to know all loop exits, such as
141 final_biv_value and final_giv_value.
143 This does not include loop exits due to return instructions.
144 This is because all bivs and givs are pseudos, and hence must be
145 dead after a return, so the presence of a return does not affect
146 any of the optimizations that use this info. It is simpler to
147 just not include return instructions on this list. */
150 /* The number of LABEL_REFs on exit_labels for this loop and all
151 loops nested inside it. */
154 /* The probable number of times the loop is executed at runtime.
155 This is an INTEGER_CST or an expression containing symbolic
156 names. Don't access this field directly:
157 number_of_iterations_in_loop computes and caches the computed
158 information in this field. */
161 /* An INTEGER_CST estimation of the number of iterations. NULL_TREE
162 if there is no estimation. */
163 tree estimated_nb_iterations
;
165 /* Upper bound on number of iterations of a loop. */
166 struct nb_iter_bound
*bounds
;
168 /* If not NULL, loop has just single exit edge stored here (edges to the
169 EXIT_BLOCK_PTR do not count. */
172 /* True when the loop does not carry data dependences, and
173 consequently the iterations can be executed in any order. False
174 when the loop carries data dependences, or when the property is
179 /* Flags for state of loop structure. */
182 LOOPS_HAVE_PREHEADERS
= 1,
183 LOOPS_HAVE_SIMPLE_LATCHES
= 2,
184 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS
= 4,
185 LOOPS_HAVE_MARKED_SINGLE_EXITS
= 8
188 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
189 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
191 /* Structure to hold CFG information about natural loops within a function. */
194 /* Number of natural loops in the function. */
197 /* Array of natural loop descriptors (scanning this array in reverse order
198 will find the inner loops before their enclosing outer loops). */
201 /* The above array is unused in new loop infrastructure and is kept only for
202 purposes of the old loop optimizer. Instead we store just pointers to
204 Note that a loop in this array may actually be NULL, if the loop
205 has been removed and the entire loops structure has not been
206 recomputed since that time. */
207 struct loop
**parray
;
209 /* Pointer to root of loop hierarchy tree. */
210 struct loop
*tree_root
;
212 /* Information derived from the CFG. */
215 /* The ordering of the basic blocks in a depth first search. */
218 /* The reverse completion ordering of the basic blocks found in a
219 depth first search. */
223 /* Headers shared by multiple loops that should be merged. */
224 sbitmap shared_headers
;
226 /* State of loops. */
230 /* The loop tree currently optimized. */
232 extern struct loops
*current_loops
;
234 /* Loop recognition. */
235 extern int flow_loops_find (struct loops
*);
236 extern void flow_loops_free (struct loops
*);
237 extern void flow_loops_dump (const struct loops
*, FILE *,
238 void (*)(const struct loop
*, FILE *, int), int);
239 extern void flow_loop_dump (const struct loop
*, FILE *,
240 void (*)(const struct loop
*, FILE *, int), int);
241 extern void flow_loop_free (struct loop
*);
242 int flow_loop_nodes_find (basic_block
, struct loop
*);
243 void fix_loop_structure (struct loops
*, bitmap changed_bbs
);
244 void mark_irreducible_loops (struct loops
*);
245 void mark_single_exit_loops (struct loops
*);
246 extern void create_loop_notes (void);
248 /* Loop data structure manipulation/querying. */
249 extern void flow_loop_tree_node_add (struct loop
*, struct loop
*);
250 extern void flow_loop_tree_node_remove (struct loop
*);
251 extern bool flow_loop_nested_p (const struct loop
*, const struct loop
*);
252 extern bool flow_bb_inside_loop_p (const struct loop
*, const basic_block
);
253 extern struct loop
* find_common_loop (struct loop
*, struct loop
*);
254 struct loop
*superloop_at_depth (struct loop
*, unsigned);
255 extern unsigned tree_num_loop_insns (struct loop
*);
256 extern int num_loop_insns (struct loop
*);
257 extern int average_num_loop_insns (struct loop
*);
258 extern unsigned get_loop_level (const struct loop
*);
259 extern bool loop_exit_edge_p (const struct loop
*, edge
);
260 extern void mark_loop_exit_edges (struct loops
*);
262 /* Loops & cfg manipulation. */
263 extern basic_block
*get_loop_body (const struct loop
*);
264 extern basic_block
*get_loop_body_in_dom_order (const struct loop
*);
265 extern basic_block
*get_loop_body_in_bfs_order (const struct loop
*);
266 extern edge
*get_loop_exit_edges (const struct loop
*, unsigned *);
267 extern unsigned num_loop_branches (const struct loop
*);
269 extern edge
loop_preheader_edge (const struct loop
*);
270 extern edge
loop_latch_edge (const struct loop
*);
272 extern void add_bb_to_loop (basic_block
, struct loop
*);
273 extern void remove_bb_from_loops (basic_block
);
275 extern void cancel_loop (struct loops
*, struct loop
*);
276 extern void cancel_loop_tree (struct loops
*, struct loop
*);
278 extern basic_block
loop_split_edge_with (edge
, rtx
);
279 extern int fix_loop_placement (struct loop
*);
283 CP_SIMPLE_PREHEADERS
= 1
286 extern void create_preheaders (struct loops
*, int);
287 extern void force_single_succ_latches (struct loops
*);
289 extern void verify_loop_structure (struct loops
*);
292 extern bool just_once_each_iteration_p (const struct loop
*, basic_block
);
293 extern unsigned expected_loop_iterations (const struct loop
*);
294 extern rtx
doloop_condition_get (rtx
);
296 /* Loop manipulation. */
297 extern bool can_duplicate_loop_p (struct loop
*loop
);
299 #define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in
300 duplicate_loop_to_header_edge. */
301 #define DLTHE_RECORD_COPY_NUMBER 2 /* Record copy number in the aux
302 field of newly create BB. */
303 #define DLTHE_FLAG_COMPLETTE_PEEL 4 /* Update frequencies expecting
304 a complete peeling. */
306 extern struct loop
* duplicate_loop (struct loops
*, struct loop
*,
308 extern bool duplicate_loop_to_header_edge (struct loop
*, edge
, struct loops
*,
309 unsigned, sbitmap
, edge
, edge
*,
311 extern struct loop
*loopify (struct loops
*, edge
, edge
,
312 basic_block
, edge
, edge
, bool);
313 struct loop
* loop_version (struct loops
*, struct loop
*, void *,
314 basic_block
*, bool);
315 extern bool remove_path (struct loops
*, edge
);
317 /* Induction variable analysis. */
319 /* The description of induction variable. The things are a bit complicated
320 due to need to handle subregs and extends. The value of the object described
321 by it can be obtained as follows (all computations are done in extend_mode):
323 Value in i-th iteration is
324 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
326 If first_special is true, the value in the first iteration is
329 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
330 subreg_{mode} (base + i * step)
332 The get_iv_value function can be used to obtain these expressions.
334 ??? Add a third mode field that would specify the mode in that inner
335 computation is done, which would enable it to be different from the
340 /* Its base and step (mode of base and step is supposed to be extend_mode,
341 see the description above). */
344 /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN). */
345 enum rtx_code extend
;
347 /* Operations applied in the extended mode. */
350 /* The mode it is extended to. */
351 enum machine_mode extend_mode
;
353 /* The mode the variable iterates in. */
354 enum machine_mode mode
;
356 /* Whether the first iteration needs to be handled specially. */
357 unsigned first_special
: 1;
360 /* The description of an exit from the loop and of the number of iterations
361 till we take the exit. */
365 /* The edge out of the loop. */
368 /* The other edge leading from the condition. */
371 /* True if we are able to say anything about number of iterations of the
375 /* True if the loop iterates the constant number of times. */
378 /* Number of iterations if constant. */
379 unsigned HOST_WIDEST_INT niter
;
381 /* Upper bound on the number of iterations. */
382 unsigned HOST_WIDEST_INT niter_max
;
384 /* Assumptions under that the rest of the information is valid. */
387 /* Assumptions under that the loop ends before reaching the latch,
388 even if value of niter_expr says otherwise. */
389 rtx noloop_assumptions
;
391 /* Condition under that the loop is infinite. */
394 /* Whether the comparison is signed. */
397 /* The mode in that niter_expr should be computed. */
398 enum machine_mode mode
;
400 /* The number of iterations of the loop. */
404 extern void iv_analysis_loop_init (struct loop
*);
405 extern bool iv_analyze (rtx
, rtx
, struct rtx_iv
*);
406 extern bool iv_analyze_result (rtx
, rtx
, struct rtx_iv
*);
407 extern bool iv_analyze_expr (rtx
, rtx
, enum machine_mode
, struct rtx_iv
*);
408 extern rtx
get_iv_value (struct rtx_iv
*, rtx
);
409 extern bool biv_p (rtx
, rtx
);
410 extern void find_simple_exit (struct loop
*, struct niter_desc
*);
411 extern void iv_analysis_done (void);
412 extern struct df
*iv_current_loop_df (void);
414 extern struct niter_desc
*get_simple_loop_desc (struct loop
*loop
);
415 extern void free_simple_loop_desc (struct loop
*loop
);
417 static inline struct niter_desc
*
418 simple_loop_desc (struct loop
*loop
)
420 return (struct niter_desc
*) loop
->aux
;
423 /* The properties of the target. */
425 extern unsigned target_avail_regs
; /* Number of available registers. */
426 extern unsigned target_res_regs
; /* Number of reserved registers. */
427 extern unsigned target_small_cost
; /* The cost for register when there
429 extern unsigned target_pres_cost
; /* The cost for register when there are
430 not too many free ones. */
431 extern unsigned target_spill_cost
; /* The cost for register when we need
434 /* Register pressure estimation for induction variable optimizations & loop
436 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
437 extern void init_set_costs (void);
439 /* Loop optimizer initialization. */
440 extern struct loops
*loop_optimizer_init (FILE *, unsigned);
441 extern void loop_optimizer_finalize (struct loops
*, FILE *);
443 /* Optimization passes. */
444 extern void unswitch_loops (struct loops
*);
448 UAP_PEEL
= 1, /* Enables loop peeling. */
449 UAP_UNROLL
= 2, /* Enables peeling of loops if it seems profitable. */
450 UAP_UNROLL_ALL
= 4 /* Enables peeling of all loops. */
453 extern void unroll_and_peel_loops (struct loops
*, int);
454 extern void doloop_optimize_loops (struct loops
*);
455 extern void move_loop_invariants (struct loops
*);
456 extern void record_estimate (struct loop
*, tree
, tree
, tree
);
458 /* Old loop optimizer interface. */
460 /* Flags passed to loop_optimize. */
461 #define LOOP_PREFETCH 1
463 #endif /* GCC_CFGLOOP_H */