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 /* The statement STMT is executed at most ... */
53 /* ... BOUND + 1 times (BOUND must be an unsigned constant).
54 The + 1 is added for the following reasons:
56 a) 0 would otherwise be unused, while we would need to care more about
57 overflows (as MAX + 1 is sometimes produced as the estimate on number
58 of executions of STMT).
59 b) it is consistent with the result of number_of_iterations_exit. */
62 /* True if the statement will cause the loop to be leaved the (at most)
63 BOUND + 1-st time it is executed, that is, all the statements after it
64 are executed at most BOUND times. */
67 /* True if the bound is "realistic" -- i.e., most likely the loop really has
68 number of iterations close to the bound. Exact bounds (if the number of
69 iterations of a loop is a constant) and bounds derived from the size of
70 data accessed in the loop are considered realistic. */
73 /* The next bound in the list. */
74 struct nb_iter_bound *next;
77 /* Structure to hold information for each natural loop. */
80 /* Index into loops array. */
83 /* Basic block of loop header. */
86 /* Basic block of loop latch. */
89 /* For loop unrolling/peeling decision. */
90 struct lpt_decision lpt_decision;
92 /* Number of loop insns. */
95 /* Average number of executed insns per iteration. */
98 /* Number of blocks contained within the loop. */
101 /* The loop nesting depth. */
104 /* Superloops of the loop. */
107 /* The height of the loop (enclosed loop levels) within the loop
111 /* The outer (parent) loop or NULL if outermost loop. */
114 /* The first inner (child) loop or NULL if innermost loop. */
117 /* Link to the next (sibling) loop. */
120 /* Loop that is copy of this loop. */
123 /* Auxiliary info specific to a pass. */
126 /* The probable number of times the loop is executed at runtime.
127 This is an INTEGER_CST or an expression containing symbolic
128 names. Don't access this field directly:
129 number_of_iterations_in_loop computes and caches the computed
130 information in this field. */
133 /* An integer estimation of the number of iterations. Estimate_state
134 describes what is the state of the estimation. */
137 /* Estimate was not computed yet. */
139 /* Estimate was computed, but we could derive no useful bound. */
141 /* Estimate is ready. */
144 double_int estimated_nb_iterations;
146 /* Upper bound on number of iterations of a loop. */
147 struct nb_iter_bound *bounds;
149 /* If not NULL, loop has just single exit edge stored here (edges to the
150 EXIT_BLOCK_PTR do not count. */
153 /* True when the loop does not carry data dependences, and
154 consequently the iterations can be executed in any order. False
155 when the loop carries data dependences, or when the property is
160 /* Flags for state of loop structure. */
163 LOOPS_HAVE_PREHEADERS = 1,
164 LOOPS_HAVE_SIMPLE_LATCHES = 2,
165 LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4,
166 LOOPS_HAVE_MARKED_SINGLE_EXITS = 8
169 #define LOOPS_NORMAL (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES \
170 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
172 /* Structure to hold CFG information about natural loops within a function. */
175 /* Number of natural loops in the function. */
178 /* State of loops. */
181 /* We store just pointers to loops here.
182 Note that a loop in this array may actually be NULL, if the loop
183 has been removed and the entire loops structure has not been
184 recomputed since that time. */
185 struct loop **parray;
187 /* Pointer to root of loop hierarchy tree. */
188 struct loop *tree_root;
190 /* Information derived from the CFG. */
193 /* The ordering of the basic blocks in a depth first search. */
196 /* The reverse completion ordering of the basic blocks found in a
197 depth first search. */
201 /* Headers shared by multiple loops that should be merged. */
202 sbitmap shared_headers;
205 /* The loop tree currently optimized. */
207 extern struct loops *current_loops;
209 /* Loop recognition. */
210 extern int flow_loops_find (struct loops *);
211 extern void flow_loops_free (struct loops *);
212 extern void flow_loops_dump (const struct loops *, FILE *,
213 void (*)(const struct loop *, FILE *, int), int);
214 extern void flow_loop_dump (const struct loop *, FILE *,
215 void (*)(const struct loop *, FILE *, int), int);
216 extern void flow_loop_free (struct loop *);
217 int flow_loop_nodes_find (basic_block, struct loop *);
218 void fix_loop_structure (struct loops *, bitmap changed_bbs);
219 void mark_irreducible_loops (struct loops *);
220 void mark_single_exit_loops (struct loops *);
222 /* Loop data structure manipulation/querying. */
223 extern void flow_loop_tree_node_add (struct loop *, struct loop *);
224 extern void flow_loop_tree_node_remove (struct loop *);
225 extern bool flow_loop_nested_p (const struct loop *, const struct loop *);
226 extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
227 extern struct loop * find_common_loop (struct loop *, struct loop *);
228 struct loop *superloop_at_depth (struct loop *, unsigned);
229 extern unsigned tree_num_loop_insns (struct loop *);
230 extern int num_loop_insns (struct loop *);
231 extern int average_num_loop_insns (struct loop *);
232 extern unsigned get_loop_level (const struct loop *);
233 extern bool loop_exit_edge_p (const struct loop *, edge);
234 extern void mark_loop_exit_edges (struct loops *);
236 /* Loops & cfg manipulation. */
237 extern basic_block *get_loop_body (const struct loop *);
238 extern basic_block *get_loop_body_in_dom_order (const struct loop *);
239 extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
240 extern edge *get_loop_exit_edges (const struct loop *, unsigned *);
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 loops *, struct loop *);
251 extern basic_block loop_split_edge_with (edge, rtx);
252 extern int fix_loop_placement (struct loop *);
256 CP_SIMPLE_PREHEADERS = 1
259 extern void create_preheaders (struct loops *, int);
260 extern void force_single_succ_latches (struct loops *);
262 extern void verify_loop_structure (struct loops *);
265 extern bool just_once_each_iteration_p (const struct loop *, basic_block);
266 extern unsigned expected_loop_iterations (const struct loop *);
267 extern rtx doloop_condition_get (rtx);
269 /* Loop manipulation. */
270 extern bool can_duplicate_loop_p (struct loop *loop);
272 #define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in
273 duplicate_loop_to_header_edge. */
274 #define DLTHE_RECORD_COPY_NUMBER 2 /* Record copy number in the aux
275 field of newly create BB. */
276 #define DLTHE_FLAG_COMPLETTE_PEEL 4 /* Update frequencies expecting
277 a complete peeling. */
279 extern struct loop * duplicate_loop (struct loops *, struct loop *,
281 extern bool duplicate_loop_to_header_edge (struct loop *, edge, struct loops *,
282 unsigned, sbitmap, edge, edge *,
284 extern struct loop *loopify (struct loops *, edge, edge,
285 basic_block, edge, edge, bool);
286 struct loop * loop_version (struct loops *, struct loop *, void *,
287 basic_block *, bool);
288 extern bool remove_path (struct loops *, edge);
290 /* Induction variable analysis. */
292 /* The description of induction variable. The things are a bit complicated
293 due to need to handle subregs and extends. The value of the object described
294 by it can be obtained as follows (all computations are done in extend_mode):
296 Value in i-th iteration is
297 delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
299 If first_special is true, the value in the first iteration is
302 If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
303 subreg_{mode} (base + i * step)
305 The get_iv_value function can be used to obtain these expressions.
307 ??? Add a third mode field that would specify the mode in that inner
308 computation is done, which would enable it to be different from the
313 /* Its base and step (mode of base and step is supposed to be extend_mode,
314 see the description above). */
317 /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN). */
318 enum rtx_code extend;
320 /* Operations applied in the extended mode. */
323 /* The mode it is extended to. */
324 enum machine_mode extend_mode;
326 /* The mode the variable iterates in. */
327 enum machine_mode mode;
329 /* Whether the first iteration needs to be handled specially. */
330 unsigned first_special : 1;
333 /* The description of an exit from the loop and of the number of iterations
334 till we take the exit. */
338 /* The edge out of the loop. */
341 /* The other edge leading from the condition. */
344 /* True if we are able to say anything about number of iterations of the
348 /* True if the loop iterates the constant number of times. */
351 /* Number of iterations if constant. */
352 unsigned HOST_WIDEST_INT niter;
354 /* Upper bound on the number of iterations. */
355 unsigned HOST_WIDEST_INT niter_max;
357 /* Assumptions under that the rest of the information is valid. */
360 /* Assumptions under that the loop ends before reaching the latch,
361 even if value of niter_expr says otherwise. */
362 rtx noloop_assumptions;
364 /* Condition under that the loop is infinite. */
367 /* Whether the comparison is signed. */
370 /* The mode in that niter_expr should be computed. */
371 enum machine_mode mode;
373 /* The number of iterations of the loop. */
377 extern void iv_analysis_loop_init (struct loop *);
378 extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
379 extern bool iv_analyze_result (rtx, rtx, struct rtx_iv *);
380 extern bool iv_analyze_expr (rtx, rtx, enum machine_mode, struct rtx_iv *);
381 extern rtx get_iv_value (struct rtx_iv *, rtx);
382 extern bool biv_p (rtx, rtx);
383 extern void find_simple_exit (struct loop *, struct niter_desc *);
384 extern void iv_analysis_done (void);
385 extern struct df *iv_current_loop_df (void);
387 extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
388 extern void free_simple_loop_desc (struct loop *loop);
390 static inline struct niter_desc *
391 simple_loop_desc (struct loop *loop)
393 return (struct niter_desc *) loop->aux;
396 /* The properties of the target. */
398 extern unsigned target_avail_regs; /* Number of available registers. */
399 extern unsigned target_res_regs; /* Number of reserved registers. */
400 extern unsigned target_small_cost; /* The cost for register when there
402 extern unsigned target_pres_cost; /* The cost for register when there are
403 not too many free ones. */
404 extern unsigned target_spill_cost; /* The cost for register when we need
407 /* Register pressure estimation for induction variable optimizations & loop
409 extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
410 extern void init_set_costs (void);
412 /* Loop optimizer initialization. */
413 extern struct loops *loop_optimizer_init (unsigned);
414 extern void loop_optimizer_finalize (struct loops *);
416 /* Optimization passes. */
417 extern void unswitch_loops (struct loops *);
421 UAP_PEEL = 1, /* Enables loop peeling. */
422 UAP_UNROLL = 2, /* Enables peeling of loops if it seems profitable. */
423 UAP_UNROLL_ALL = 4 /* Enables peeling of all loops. */
426 extern void unroll_and_peel_loops (struct loops *, int);
427 extern void doloop_optimize_loops (struct loops *);
428 extern void move_loop_invariants (struct loops *);
430 #endif /* GCC_CFGLOOP_H */