1 /* Natural loop functions
2 Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
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, 59 Temple Place - Suite 330, 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 /* Basic block of loop preheader or NULL if it does not exist. */
73 basic_block pre_header
;
75 /* For loop unrolling/peeling decision. */
76 struct lpt_decision lpt_decision
;
78 /* Number of loop insns. */
81 /* Average number of executed insns per iteration. */
84 /* Array of edges along the preheader extended basic block trace.
85 The source of the first edge is the root node of preheader
86 extended basic block, if it exists. */
87 edge
*pre_header_edges
;
89 /* Number of edges along the pre_header extended basic block trace. */
90 int num_pre_header_edges
;
92 /* The first block in the loop. This is not necessarily the same as
96 /* The last block in the loop. This is not necessarily the same as
100 /* Number of blocks contained within the loop. */
103 /* Array of edges that enter the loop. */
106 /* Number of edges that enter the loop. */
109 /* Array of edges that exit the loop. */
112 /* Number of edges that exit the loop. */
115 /* Bitmap of blocks that dominate all exits of the loop. */
118 /* The loop nesting depth. */
121 /* Superloops of the loop. */
124 /* The height of the loop (enclosed loop levels) within the loop
128 /* The outer (parent) loop or NULL if outermost loop. */
131 /* The first inner (child) loop or NULL if innermost loop. */
134 /* Link to the next (sibling) loop. */
137 /* Loop that is copy of this loop. */
140 /* Nonzero if the loop is invalid (e.g., contains setjmp.). */
143 /* Auxiliary info specific to a pass. */
146 /* The following are currently used by loop.c but they are likely to
147 disappear when loop.c is replaced and removed. */
149 /* The NOTE_INSN_LOOP_BEG. */
152 /* The NOTE_INSN_LOOP_END. */
155 /* For a rotated loop that is entered near the bottom,
156 this is the label at the top. Otherwise it is zero. */
159 /* Place in the loop where control enters. */
162 /* The position where to sink insns out of the loop. */
165 /* List of all LABEL_REFs which refer to code labels outside the
166 loop. Used by routines that need to know all loop exits, such as
167 final_biv_value and final_giv_value.
169 This does not include loop exits due to return instructions.
170 This is because all bivs and givs are pseudos, and hence must be
171 dead after a return, so the presence of a return does not affect
172 any of the optimizations that use this info. It is simpler to
173 just not include return instructions on this list. */
176 /* The number of LABEL_REFs on exit_labels for this loop and all
177 loops nested inside it. */
180 /* The probable number of times the loop is executed at runtime.
181 This is an INTEGER_CST or an expression containing symbolic
182 names. Don't access this field directly:
183 number_of_iterations_in_loop computes and caches the computed
184 information in this field. */
187 /* An INTEGER_CST estimation of the number of iterations. NULL_TREE
188 if there is no estimation. */
189 tree estimated_nb_iterations
;
191 /* Upper bound on number of iterations of a loop. */
192 struct nb_iter_bound
*bounds
;
194 /* If not NULL, loop has just single exit edge stored here (edges to the
195 EXIT_BLOCK_PTR do not count. */
198 /* True when the loop does not carry data dependences, and
199 consequently the iterations can be executed in any order. False
200 when the loop carries data dependences, or when the property is
205 /* Flags for state of loop structure. */
208 LOOPS_HAVE_PREHEADERS
= 1,
209 LOOPS_HAVE_SIMPLE_LATCHES
= 2,
210 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS
= 4,
211 LOOPS_HAVE_MARKED_SINGLE_EXITS
= 8
214 /* Structure to hold CFG information about natural loops within a function. */
217 /* Number of natural loops in the function. */
220 /* Maximum nested loop level in the function. */
223 /* Array of natural loop descriptors (scanning this array in reverse order
224 will find the inner loops before their enclosing outer loops). */
227 /* The above array is unused in new loop infrastructure and is kept only for
228 purposes of the old loop optimizer. Instead we store just pointers to
230 struct loop
**parray
;
232 /* Pointer to root of loop hierarchy tree. */
233 struct loop
*tree_root
;
235 /* Information derived from the CFG. */
238 /* The ordering of the basic blocks in a depth first search. */
241 /* The reverse completion ordering of the basic blocks found in a
242 depth first search. */
246 /* Headers shared by multiple loops that should be merged. */
247 sbitmap shared_headers
;
249 /* State of loops. */
253 /* The loop tree currently optimized. */
255 extern struct loops
*current_loops
;
257 /* Flags for loop discovery. */
259 #define LOOP_TREE 1 /* Build loop hierarchy tree. */
260 #define LOOP_PRE_HEADER 2 /* Analyze loop preheader. */
261 #define LOOP_ENTRY_EDGES 4 /* Find entry edges. */
262 #define LOOP_EXIT_EDGES 8 /* Find exit edges. */
263 #define LOOP_EDGES (LOOP_ENTRY_EDGES | LOOP_EXIT_EDGES)
264 #define LOOP_ALL 15 /* All of the above */
266 /* Loop recognition. */
267 extern int flow_loops_find (struct loops
*, int flags
);
268 extern void flow_loops_free (struct loops
*);
269 extern void flow_loops_dump (const struct loops
*, FILE *,
270 void (*)(const struct loop
*, FILE *, int), int);
271 extern void flow_loop_dump (const struct loop
*, FILE *,
272 void (*)(const struct loop
*, FILE *, int), int);
273 extern int flow_loop_scan (struct loop
*, int);
274 extern void flow_loop_free (struct loop
*);
275 void mark_irreducible_loops (struct loops
*);
276 void mark_single_exit_loops (struct loops
*);
277 void update_single_exits_after_duplication (basic_block
*, unsigned,
279 extern void create_loop_notes (void);
281 /* Loop data structure manipulation/querying. */
282 extern void flow_loop_tree_node_add (struct loop
*, struct loop
*);
283 extern void flow_loop_tree_node_remove (struct loop
*);
284 extern bool flow_loop_outside_edge_p (const struct loop
*, edge
);
285 extern bool flow_loop_nested_p (const struct loop
*, const struct loop
*);
286 extern bool flow_bb_inside_loop_p (const struct loop
*, const basic_block
);
287 extern struct loop
* find_common_loop (struct loop
*, struct loop
*);
288 struct loop
*superloop_at_depth (struct loop
*, unsigned);
289 extern unsigned tree_num_loop_insns (struct loop
*);
290 extern int num_loop_insns (struct loop
*);
291 extern int average_num_loop_insns (struct loop
*);
292 extern unsigned get_loop_level (const struct loop
*);
294 /* Loops & cfg manipulation. */
295 extern basic_block
*get_loop_body (const struct loop
*);
296 extern basic_block
*get_loop_body_in_dom_order (const struct loop
*);
297 extern basic_block
*get_loop_body_in_bfs_order (const struct loop
*);
298 extern edge
*get_loop_exit_edges (const struct loop
*, unsigned *);
299 extern unsigned num_loop_branches (const struct loop
*);
301 extern edge
loop_preheader_edge (const struct loop
*);
302 extern edge
loop_latch_edge (const struct loop
*);
304 extern void add_bb_to_loop (basic_block
, struct loop
*);
305 extern void remove_bb_from_loops (basic_block
);
307 extern void cancel_loop (struct loops
*, struct loop
*);
308 extern void cancel_loop_tree (struct loops
*, struct loop
*);
310 extern basic_block
loop_split_edge_with (edge
, rtx
);
311 extern int fix_loop_placement (struct loop
*);
315 CP_SIMPLE_PREHEADERS
= 1
318 extern void create_preheaders (struct loops
*, int);
319 extern void force_single_succ_latches (struct loops
*);
321 extern void verify_loop_structure (struct loops
*);
324 extern bool just_once_each_iteration_p (struct loop
*, basic_block
);
325 extern unsigned expected_loop_iterations (const struct loop
*);
327 /* Loop manipulation. */
328 extern bool can_duplicate_loop_p (struct loop
*loop
);
330 #define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in
331 duplicate_loop_to_header_edge. */
333 extern struct loop
* duplicate_loop (struct loops
*, struct loop
*,
335 extern int duplicate_loop_to_header_edge (struct loop
*, edge
, struct loops
*,
336 unsigned, sbitmap
, edge
, edge
*,
338 extern struct loop
*loopify (struct loops
*, edge
, edge
,
339 basic_block
, edge
, edge
, bool);
340 extern void unloop (struct loops
*, struct loop
*);
341 extern bool remove_path (struct loops
*, edge
);
342 extern edge
split_loop_bb (basic_block
, void *);
344 /* Induction variable analysis. */
346 /* The description of induction variable. The things are a bit complicated
347 due to need to handle subregs and extends. The value of the object described
348 by it can be obtained as follows (all computations are done in extend_mode):
350 Value in i-th iteration is
351 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
353 If first_special is true, the value in the first iteration is
356 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
357 subreg_{mode} (base + i * step)
359 The get_iv_value function can be used to obtain these expressions.
361 ??? Add a third mode field that would specify the mode in that inner
362 computation is done, which would enable it to be different from the
367 /* Its base and step (mode of base and step is supposed to be extend_mode,
368 see the description above). */
371 /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN). */
372 enum rtx_code extend
;
374 /* Operations applied in the extended mode. */
377 /* The mode it is extended to. */
378 enum machine_mode extend_mode
;
380 /* The mode the variable iterates in. */
381 enum machine_mode mode
;
383 /* Whether we have already filled the remaining fields. */
384 unsigned analysed
: 1;
386 /* Whether the first iteration needs to be handled specially. */
387 unsigned first_special
: 1;
390 /* The description of an exit from the loop and of the number of iterations
391 till we take the exit. */
395 /* The edge out of the loop. */
398 /* The other edge leading from the condition. */
401 /* True if we are able to say anything about number of iterations of the
405 /* True if the loop iterates the constant number of times. */
408 /* Number of iterations if constant. */
409 unsigned HOST_WIDEST_INT niter
;
411 /* Upper bound on the number of iterations. */
412 unsigned HOST_WIDEST_INT niter_max
;
414 /* Assumptions under that the rest of the information is valid. */
417 /* Assumptions under that the loop ends before reaching the latch,
418 even if value of niter_expr says otherwise. */
419 rtx noloop_assumptions
;
421 /* Condition under that the loop is infinite. */
424 /* Whether the comparison is signed. */
427 /* The mode in that niter_expr should be computed. */
428 enum machine_mode mode
;
430 /* The number of iterations of the loop. */
434 extern void iv_analysis_loop_init (struct loop
*);
435 extern rtx
iv_get_reaching_def (rtx
, rtx
);
436 extern bool iv_analyze (rtx
, rtx
, struct rtx_iv
*);
437 extern rtx
get_iv_value (struct rtx_iv
*, rtx
);
438 extern bool biv_p (rtx
, rtx
);
439 extern void find_simple_exit (struct loop
*, struct niter_desc
*);
440 extern void iv_number_of_iterations (struct loop
*, rtx
, rtx
,
441 struct niter_desc
*);
442 extern void iv_analysis_done (void);
444 extern struct niter_desc
*get_simple_loop_desc (struct loop
*loop
);
445 extern void free_simple_loop_desc (struct loop
*loop
);
447 static inline struct niter_desc
*
448 simple_loop_desc (struct loop
*loop
)
453 /* The properties of the target. */
455 extern unsigned target_avail_regs
; /* Number of available registers. */
456 extern unsigned target_res_regs
; /* Number of reserved registers. */
457 extern unsigned target_small_cost
; /* The cost for register when there
459 extern unsigned target_pres_cost
; /* The cost for register when there are
460 not too many free ones. */
461 extern unsigned target_spill_cost
; /* The cost for register when we need
464 /* Register pressure estimation for induction variable optimizations & loop
466 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
467 extern void init_set_costs (void);
469 /* Loop optimizer initialization. */
470 extern struct loops
*loop_optimizer_init (FILE *);
471 extern void loop_optimizer_finalize (struct loops
*, FILE *);
473 /* Optimization passes. */
474 extern void unswitch_loops (struct loops
*);
478 UAP_PEEL
= 1, /* Enables loop peeling. */
479 UAP_UNROLL
= 2, /* Enables peeling of loops if it seems profitable. */
480 UAP_UNROLL_ALL
= 4 /* Enables peeling of all loops. */
483 extern void unroll_and_peel_loops (struct loops
*, int);
484 extern void doloop_optimize_loops (struct loops
*);
485 extern void move_loop_invariants (struct loops
*);
486 extern void record_estimate (struct loop
*, tree
, tree
, tree
);
488 /* Old loop optimizer interface. */
490 /* Flags passed to loop_optimize. */
491 #define LOOP_PREFETCH 1
493 extern void loop_optimize (rtx
, FILE *, int);
495 #endif /* GCC_CFGLOOP_H */