1/* Natural loop functions
2   Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
3   Free Software Foundation, Inc.
4
5This file is part of GCC.
6
7GCC is free software; you can redistribute it and/or modify it under
8the terms of the GNU General Public License as published by the Free
9Software Foundation; either version 2, or (at your option) any later
10version.
11
12GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13WARRANTY; without even the implied warranty of MERCHANTABILITY or
14FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
15for more details.
16
17You should have received a copy of the GNU General Public License
18along with GCC; see the file COPYING.  If not, write to the Free
19Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
2002110-1301, USA.  */
21
22#ifndef GCC_CFGLOOP_H
23#define GCC_CFGLOOP_H
24
25#include "basic-block.h"
26/* For rtx_code.  */
27#include "rtl.h"
28
29/* Structure to hold decision about unrolling/peeling.  */
30enum lpt_dec
31{
32  LPT_NONE,
33  LPT_PEEL_COMPLETELY,
34  LPT_PEEL_SIMPLE,
35  LPT_UNROLL_CONSTANT,
36  LPT_UNROLL_RUNTIME,
37  LPT_UNROLL_STUPID
38};
39
40struct lpt_decision
41{
42  enum lpt_dec decision;
43  unsigned times;
44};
45
46/* The structure describing a bound on number of iterations of a loop.  */
47
48struct nb_iter_bound
49{
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.  */
58};
59
60/* Structure to hold information for each natural loop.  */
61struct loop
62{
63  /* Index into loops array.  */
64  int num;
65
66  /* Basic block of loop header.  */
67  basic_block header;
68
69  /* Basic block of loop latch.  */
70  basic_block latch;
71
72  /* For loop unrolling/peeling decision.  */
73  struct lpt_decision lpt_decision;
74
75  /* Number of loop insns.  */
76  unsigned ninsns;
77
78  /* Average number of executed insns per iteration.  */
79  unsigned av_ninsns;
80
81  /* The first block in the loop.  This is not necessarily the same as
82     the loop header.  */
83  basic_block first;
84
85  /* The last block in the loop.  This is not necessarily the same as
86     the loop latch.  */
87  basic_block last;
88
89  /* Number of blocks contained within the loop.  */
90  unsigned num_nodes;
91
92  /* The loop nesting depth.  */
93  int depth;
94
95  /* Superloops of the loop.  */
96  struct loop **pred;
97
98  /* The height of the loop (enclosed loop levels) within the loop
99     hierarchy tree.  */
100  int level;
101
102  /* The outer (parent) loop or NULL if outermost loop.  */
103  struct loop *outer;
104
105  /* The first inner (child) loop or NULL if innermost loop.  */
106  struct loop *inner;
107
108  /* Link to the next (sibling) loop.  */
109  struct loop *next;
110
111  /* Loop that is copy of this loop.  */
112  struct loop *copy;
113
114  /* Nonzero if the loop is invalid (e.g., contains setjmp.).  */
115  int invalid;
116
117  /* Auxiliary info specific to a pass.  */
118  void *aux;
119
120  /* The following are currently used by loop.c but they are likely to
121     disappear when loop.c is replaced and removed.  */
122
123  /* The NOTE_INSN_LOOP_BEG.  */
124  rtx start;
125
126  /* The NOTE_INSN_LOOP_END.  */
127  rtx end;
128
129  /* For a rotated loop that is entered near the bottom,
130     this is the label at the top.  Otherwise it is zero.  */
131  rtx top;
132
133  /* Place in the loop where control enters.  */
134  rtx scan_start;
135
136  /* The position where to sink insns out of the loop.  */
137  rtx sink;
138
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.
142
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.  */
148  rtx exit_labels;
149
150  /* The number of LABEL_REFs on exit_labels for this loop and all
151     loops nested inside it.  */
152  int exit_count;
153
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.  */
159  tree nb_iterations;
160
161  /* An INTEGER_CST estimation of the number of iterations.  NULL_TREE
162     if there is no estimation.  */
163  tree estimated_nb_iterations;
164
165  /* Upper bound on number of iterations of a loop.  */
166  struct nb_iter_bound *bounds;
167
168  /* If not NULL, loop has just single exit edge stored here (edges to the
169     EXIT_BLOCK_PTR do not count.  */
170  edge single_exit;
171
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
175     not decidable.  */
176  bool parallel_p;
177};
178
179/* Flags for state of loop structure.  */
180enum
181{
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
186};
187
188/* Structure to hold CFG information about natural loops within a function.  */
189struct loops
190{
191  /* Number of natural loops in the function.  */
192  unsigned num;
193
194  /* Array of natural loop descriptors (scanning this array in reverse order
195     will find the inner loops before their enclosing outer loops).  */
196  struct loop *array;
197
198  /* The above array is unused in new loop infrastructure and is kept only for
199     purposes of the old loop optimizer.  Instead we store just pointers to
200     loops here.
201     Note that a loop in this array may actually be NULL, if the loop
202     has been removed and the entire loops structure has not been
203     recomputed since that time.  */
204  struct loop **parray;
205
206  /* Pointer to root of loop hierarchy tree.  */
207  struct loop *tree_root;
208
209  /* Information derived from the CFG.  */
210  struct cfg
211  {
212    /* The ordering of the basic blocks in a depth first search.  */
213    int *dfs_order;
214
215    /* The reverse completion ordering of the basic blocks found in a
216       depth first search.  */
217    int *rc_order;
218  } cfg;
219
220  /* Headers shared by multiple loops that should be merged.  */
221  sbitmap shared_headers;
222
223  /* State of loops.  */
224  int state;
225};
226
227/* The loop tree currently optimized.  */
228
229extern struct loops *current_loops;
230
231/* Loop recognition.  */
232extern int flow_loops_find (struct loops *);
233extern void flow_loops_free (struct loops *);
234extern void flow_loops_dump (const struct loops *, FILE *,
235			     void (*)(const struct loop *, FILE *, int), int);
236extern void flow_loop_dump (const struct loop *, FILE *,
237			    void (*)(const struct loop *, FILE *, int), int);
238extern void flow_loop_free (struct loop *);
239int flow_loop_nodes_find (basic_block, struct loop *);
240void fix_loop_structure (struct loops *, bitmap changed_bbs);
241void mark_irreducible_loops (struct loops *);
242void mark_single_exit_loops (struct loops *);
243extern void create_loop_notes (void);
244
245/* Loop data structure manipulation/querying.  */
246extern void flow_loop_tree_node_add (struct loop *, struct loop *);
247extern void flow_loop_tree_node_remove (struct loop *);
248extern bool flow_loop_outside_edge_p (const struct loop *, edge);
249extern bool flow_loop_nested_p	(const struct loop *, const struct loop *);
250extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block);
251extern struct loop * find_common_loop (struct loop *, struct loop *);
252struct loop *superloop_at_depth (struct loop *, unsigned);
253extern unsigned tree_num_loop_insns (struct loop *);
254extern int num_loop_insns (struct loop *);
255extern int average_num_loop_insns (struct loop *);
256extern unsigned get_loop_level (const struct loop *);
257extern bool loop_exit_edge_p (const struct loop *, edge);
258extern void mark_loop_exit_edges (struct loops *);
259
260/* Loops & cfg manipulation.  */
261extern basic_block *get_loop_body (const struct loop *);
262extern basic_block *get_loop_body_in_dom_order (const struct loop *);
263extern basic_block *get_loop_body_in_bfs_order (const struct loop *);
264extern edge *get_loop_exit_edges (const struct loop *, unsigned *);
265extern unsigned num_loop_branches (const struct loop *);
266
267extern edge loop_preheader_edge (const struct loop *);
268extern edge loop_latch_edge (const struct loop *);
269
270extern void add_bb_to_loop (basic_block, struct loop *);
271extern void remove_bb_from_loops (basic_block);
272
273extern void cancel_loop (struct loops *, struct loop *);
274extern void cancel_loop_tree (struct loops *, struct loop *);
275
276extern basic_block loop_split_edge_with (edge, rtx);
277extern int fix_loop_placement (struct loop *);
278
279enum
280{
281  CP_SIMPLE_PREHEADERS = 1
282};
283
284extern void create_preheaders (struct loops *, int);
285extern void force_single_succ_latches (struct loops *);
286
287extern void verify_loop_structure (struct loops *);
288
289/* Loop analysis.  */
290extern bool just_once_each_iteration_p (const struct loop *, basic_block);
291extern unsigned expected_loop_iterations (const struct loop *);
292extern rtx doloop_condition_get (rtx);
293
294/* Loop manipulation.  */
295extern bool can_duplicate_loop_p (struct loop *loop);
296
297#define DLTHE_FLAG_UPDATE_FREQ	1	/* Update frequencies in
298					   duplicate_loop_to_header_edge.  */
299#define DLTHE_RECORD_COPY_NUMBER 2	/* Record copy number in the aux
300					   field of newly create BB.  */
301#define DLTHE_FLAG_COMPLETTE_PEEL 4	/* Update frequencies expecting
302					   a complete peeling.  */
303
304extern struct loop * duplicate_loop (struct loops *, struct loop *,
305				     struct loop *);
306extern bool duplicate_loop_to_header_edge (struct loop *, edge, struct loops *,
307					   unsigned, sbitmap, edge, edge *,
308					   unsigned *, int);
309extern struct loop *loopify (struct loops *, edge, edge,
310			     basic_block, edge, edge, bool);
311struct loop * loop_version (struct loops *, struct loop *, void *,
312			    basic_block *, bool);
313extern bool remove_path (struct loops *, edge);
314extern edge split_loop_bb (basic_block, void *);
315
316/* Induction variable analysis.  */
317
318/* The description of induction variable.  The things are a bit complicated
319   due to need to handle subregs and extends.  The value of the object described
320   by it can be obtained as follows (all computations are done in extend_mode):
321
322   Value in i-th iteration is
323     delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)).
324
325   If first_special is true, the value in the first iteration is
326     delta + mult * base
327
328   If extend = UNKNOWN, first_special must be false, delta 0, mult 1 and value is
329     subreg_{mode} (base + i * step)
330
331   The get_iv_value function can be used to obtain these expressions.
332
333   ??? Add a third mode field that would specify the mode in that inner
334   computation is done, which would enable it to be different from the
335   outer one?  */
336
337struct rtx_iv
338{
339  /* Its base and step (mode of base and step is supposed to be extend_mode,
340     see the description above).  */
341  rtx base, step;
342
343  /* The type of extend applied to it (SIGN_EXTEND, ZERO_EXTEND or UNKNOWN).  */
344  enum rtx_code extend;
345
346  /* Operations applied in the extended mode.  */
347  rtx delta, mult;
348
349  /* The mode it is extended to.  */
350  enum machine_mode extend_mode;
351
352  /* The mode the variable iterates in.  */
353  enum machine_mode mode;
354
355  /* Whether we have already filled the remaining fields.  */
356  unsigned analysed : 1;
357
358  /* Whether the first iteration needs to be handled specially.  */
359  unsigned first_special : 1;
360};
361
362/* The description of an exit from the loop and of the number of iterations
363   till we take the exit.  */
364
365struct niter_desc
366{
367  /* The edge out of the loop.  */
368  edge out_edge;
369
370  /* The other edge leading from the condition.  */
371  edge in_edge;
372
373  /* True if we are able to say anything about number of iterations of the
374     loop.  */
375  bool simple_p;
376
377  /* True if the loop iterates the constant number of times.  */
378  bool const_iter;
379
380  /* Number of iterations if constant.  */
381  unsigned HOST_WIDEST_INT niter;
382
383  /* Upper bound on the number of iterations.  */
384  unsigned HOST_WIDEST_INT niter_max;
385
386  /* Assumptions under that the rest of the information is valid.  */
387  rtx assumptions;
388
389  /* Assumptions under that the loop ends before reaching the latch,
390     even if value of niter_expr says otherwise.  */
391  rtx noloop_assumptions;
392
393  /* Condition under that the loop is infinite.  */
394  rtx infinite;
395
396  /* Whether the comparison is signed.  */
397  bool signed_p;
398
399  /* The mode in that niter_expr should be computed.  */
400  enum machine_mode mode;
401
402  /* The number of iterations of the loop.  */
403  rtx niter_expr;
404};
405
406extern void iv_analysis_loop_init (struct loop *);
407extern rtx iv_get_reaching_def (rtx, rtx);
408extern bool iv_analyze (rtx, rtx, struct rtx_iv *);
409extern rtx get_iv_value (struct rtx_iv *, rtx);
410extern bool biv_p (rtx, rtx);
411extern void find_simple_exit (struct loop *, struct niter_desc *);
412extern void iv_analysis_done (void);
413
414extern struct niter_desc *get_simple_loop_desc (struct loop *loop);
415extern void free_simple_loop_desc (struct loop *loop);
416
417static inline struct niter_desc *
418simple_loop_desc (struct loop *loop)
419{
420  return loop->aux;
421}
422
423/* The properties of the target.  */
424
425extern unsigned target_avail_regs;	/* Number of available registers.  */
426extern unsigned target_res_regs;	/* Number of reserved registers.  */
427extern unsigned target_small_cost;	/* The cost for register when there
428					   is a free one.  */
429extern unsigned target_pres_cost;	/* The cost for register when there are
430					   not too many free ones.  */
431extern unsigned target_spill_cost;	/* The cost for register when we need
432					   to spill.  */
433
434/* Register pressure estimation for induction variable optimizations & loop
435   invariant motion.  */
436extern unsigned global_cost_for_size (unsigned, unsigned, unsigned);
437extern void init_set_costs (void);
438
439/* Loop optimizer initialization.  */
440extern struct loops *loop_optimizer_init (FILE *);
441extern void loop_optimizer_finalize (struct loops *, FILE *);
442
443/* Optimization passes.  */
444extern void unswitch_loops (struct loops *);
445
446enum
447{
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.  */
451};
452
453extern void unroll_and_peel_loops (struct loops *, int);
454extern void doloop_optimize_loops (struct loops *);
455extern void move_loop_invariants (struct loops *);
456extern void record_estimate (struct loop *, tree, tree, tree);
457
458/* Old loop optimizer interface.  */
459
460/* Flags passed to loop_optimize.  */
461#define LOOP_PREFETCH 1
462
463extern void loop_optimize (rtx, FILE *, int);
464
465#endif /* GCC_CFGLOOP_H */
466