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3d436d2a | 1 | /* Natural loop functions |
ca9398d1 | 2 | Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003 |
3d436d2a ZD |
3 | Free Software Foundation, Inc. |
4 | ||
5 | This file is part of GCC. | |
6 | ||
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 | |
10 | version. | |
11 | ||
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 | |
15 | for more details. | |
16 | ||
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 | |
20 | 02111-1307, USA. */ | |
21 | ||
22 | /* Structure to hold decision about unrolling/peeling. */ | |
23 | enum lpt_dec | |
24 | { | |
25 | LPT_NONE, | |
26 | LPT_PEEL_COMPLETELY, | |
27 | LPT_PEEL_SIMPLE, | |
28 | LPT_UNROLL_CONSTANT, | |
29 | LPT_UNROLL_RUNTIME, | |
30 | LPT_UNROLL_STUPID | |
31 | }; | |
32 | ||
33 | struct lpt_decision | |
34 | { | |
35 | enum lpt_dec decision; | |
36 | unsigned times; | |
37 | }; | |
38 | ||
39 | /* Description of loop for simple loop unrolling. */ | |
40 | struct loop_desc | |
41 | { | |
42 | int postincr; /* 1 if increment/decrement is done after loop exit condition. */ | |
43 | rtx stride; /* Value added to VAR in each iteration. */ | |
44 | rtx var; /* Loop control variable. */ | |
142d1f57 ZD |
45 | enum machine_mode inner_mode; |
46 | /* The mode from that it is extended. */ | |
47 | enum rtx_code extend; /* With this extend. */ | |
3d436d2a ZD |
48 | rtx var_alts; /* List of definitions of its initial value. */ |
49 | rtx lim; /* Expression var is compared with. */ | |
50 | rtx lim_alts; /* List of definitions of its initial value. */ | |
51 | bool const_iter; /* True if it iterates constant number of times. */ | |
52 | unsigned HOST_WIDE_INT niter; | |
53 | /* Number of iterations if it is constant. */ | |
54 | bool may_be_zero; /* If we cannot determine that the first iteration will pass. */ | |
55 | enum rtx_code cond; /* Exit condition. */ | |
56 | int neg; /* Set to 1 if loop ends when condition is satisfied. */ | |
57 | edge out_edge; /* The exit edge. */ | |
58 | edge in_edge; /* And the other one. */ | |
59 | int n_branches; /* Number of branches inside the loop. */ | |
60 | }; | |
61 | ||
62 | /* Structure to hold information for each natural loop. */ | |
63 | struct loop | |
64 | { | |
65 | /* Index into loops array. */ | |
66 | int num; | |
67 | ||
68 | /* Basic block of loop header. */ | |
69 | basic_block header; | |
70 | ||
71 | /* Basic block of loop latch. */ | |
72 | basic_block latch; | |
73 | ||
74 | /* Basic block of loop preheader or NULL if it does not exist. */ | |
75 | basic_block pre_header; | |
76 | ||
77 | /* For loop unrolling/peeling decision. */ | |
78 | struct lpt_decision lpt_decision; | |
79 | ||
80 | /* Simple loop description. */ | |
81 | int simple; | |
82 | struct loop_desc desc; | |
83 | int has_desc; | |
84 | ||
85 | /* Number of loop insns. */ | |
86 | unsigned ninsns; | |
87 | ||
88 | /* Average number of executed insns per iteration. */ | |
89 | unsigned av_ninsns; | |
90 | ||
91 | /* Array of edges along the preheader extended basic block trace. | |
92 | The source of the first edge is the root node of preheader | |
93 | extended basic block, if it exists. */ | |
94 | edge *pre_header_edges; | |
95 | ||
96 | /* Number of edges along the pre_header extended basic block trace. */ | |
97 | int num_pre_header_edges; | |
98 | ||
99 | /* The first block in the loop. This is not necessarily the same as | |
100 | the loop header. */ | |
101 | basic_block first; | |
102 | ||
103 | /* The last block in the loop. This is not necessarily the same as | |
104 | the loop latch. */ | |
105 | basic_block last; | |
106 | ||
107 | /* Bitmap of blocks contained within the loop. */ | |
108 | sbitmap nodes; | |
109 | ||
110 | /* Number of blocks contained within the loop. */ | |
111 | unsigned num_nodes; | |
112 | ||
113 | /* Array of edges that enter the loop. */ | |
114 | edge *entry_edges; | |
115 | ||
116 | /* Number of edges that enter the loop. */ | |
117 | int num_entries; | |
118 | ||
119 | /* Array of edges that exit the loop. */ | |
120 | edge *exit_edges; | |
121 | ||
122 | /* Number of edges that exit the loop. */ | |
123 | int num_exits; | |
124 | ||
125 | /* Bitmap of blocks that dominate all exits of the loop. */ | |
126 | sbitmap exits_doms; | |
127 | ||
128 | /* The loop nesting depth. */ | |
129 | int depth; | |
130 | ||
131 | /* Superloops of the loop. */ | |
132 | struct loop **pred; | |
133 | ||
134 | /* The height of the loop (enclosed loop levels) within the loop | |
135 | hierarchy tree. */ | |
136 | int level; | |
137 | ||
138 | /* The outer (parent) loop or NULL if outermost loop. */ | |
139 | struct loop *outer; | |
140 | ||
141 | /* The first inner (child) loop or NULL if innermost loop. */ | |
142 | struct loop *inner; | |
143 | ||
144 | /* Link to the next (sibling) loop. */ | |
145 | struct loop *next; | |
146 | ||
147 | /* Loop that is copy of this loop. */ | |
148 | struct loop *copy; | |
149 | ||
6356f892 | 150 | /* Nonzero if the loop is invalid (e.g., contains setjmp.). */ |
3d436d2a ZD |
151 | int invalid; |
152 | ||
153 | /* Auxiliary info specific to a pass. */ | |
154 | void *aux; | |
155 | ||
156 | /* The following are currently used by loop.c but they are likely to | |
157 | disappear as loop.c is converted to use the CFG. */ | |
158 | ||
6356f892 | 159 | /* Nonzero if the loop has a NOTE_INSN_LOOP_VTOP. */ |
3d436d2a ZD |
160 | rtx vtop; |
161 | ||
6356f892 | 162 | /* Nonzero if the loop has a NOTE_INSN_LOOP_CONT. |
3d436d2a ZD |
163 | A continue statement will generate a branch to NEXT_INSN (cont). */ |
164 | rtx cont; | |
165 | ||
166 | /* The dominator of cont. */ | |
167 | rtx cont_dominator; | |
168 | ||
169 | /* The NOTE_INSN_LOOP_BEG. */ | |
170 | rtx start; | |
171 | ||
172 | /* The NOTE_INSN_LOOP_END. */ | |
173 | rtx end; | |
174 | ||
175 | /* For a rotated loop that is entered near the bottom, | |
176 | this is the label at the top. Otherwise it is zero. */ | |
177 | rtx top; | |
178 | ||
179 | /* Place in the loop where control enters. */ | |
180 | rtx scan_start; | |
181 | ||
182 | /* The position where to sink insns out of the loop. */ | |
183 | rtx sink; | |
184 | ||
185 | /* List of all LABEL_REFs which refer to code labels outside the | |
186 | loop. Used by routines that need to know all loop exits, such as | |
187 | final_biv_value and final_giv_value. | |
188 | ||
189 | This does not include loop exits due to return instructions. | |
190 | This is because all bivs and givs are pseudos, and hence must be | |
191 | dead after a return, so the presence of a return does not affect | |
192 | any of the optimizations that use this info. It is simpler to | |
193 | just not include return instructions on this list. */ | |
194 | rtx exit_labels; | |
195 | ||
196 | /* The number of LABEL_REFs on exit_labels for this loop and all | |
197 | loops nested inside it. */ | |
198 | int exit_count; | |
199 | }; | |
200 | ||
201 | /* Flags for state of loop structure. */ | |
202 | enum | |
203 | { | |
204 | LOOPS_HAVE_PREHEADERS = 1, | |
205 | LOOPS_HAVE_SIMPLE_LATCHES = 2, | |
206 | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4 | |
207 | }; | |
208 | ||
209 | /* Structure to hold CFG information about natural loops within a function. */ | |
210 | struct loops | |
211 | { | |
212 | /* Number of natural loops in the function. */ | |
213 | unsigned num; | |
214 | ||
215 | /* Maximum nested loop level in the function. */ | |
216 | unsigned levels; | |
217 | ||
218 | /* Array of natural loop descriptors (scanning this array in reverse order | |
219 | will find the inner loops before their enclosing outer loops). */ | |
220 | struct loop *array; | |
221 | ||
222 | /* The above array is unused in new loop infrastructure and is kept only for | |
223 | purposes of the old loop optimizer. Instead we store just pointers to | |
224 | loops here. */ | |
225 | struct loop **parray; | |
226 | ||
227 | /* Pointer to root of loop hierarchy tree. */ | |
228 | struct loop *tree_root; | |
229 | ||
230 | /* Information derived from the CFG. */ | |
231 | struct cfg | |
232 | { | |
3d436d2a ZD |
233 | /* The ordering of the basic blocks in a depth first search. */ |
234 | int *dfs_order; | |
235 | ||
236 | /* The reverse completion ordering of the basic blocks found in a | |
237 | depth first search. */ | |
238 | int *rc_order; | |
239 | } cfg; | |
240 | ||
241 | /* Headers shared by multiple loops that should be merged. */ | |
242 | sbitmap shared_headers; | |
243 | ||
244 | /* State of loops. */ | |
245 | int state; | |
246 | }; | |
247 | ||
248 | /* Flags for loop discovery. */ | |
249 | ||
250 | #define LOOP_TREE 1 /* Build loop hierarchy tree. */ | |
251 | #define LOOP_PRE_HEADER 2 /* Analyze loop preheader. */ | |
252 | #define LOOP_ENTRY_EDGES 4 /* Find entry edges. */ | |
253 | #define LOOP_EXIT_EDGES 8 /* Find exit edges. */ | |
254 | #define LOOP_EDGES (LOOP_ENTRY_EDGES | LOOP_EXIT_EDGES) | |
255 | #define LOOP_ALL 15 /* All of the above */ | |
256 | ||
257 | /* Loop recognition. */ | |
d329e058 AJ |
258 | extern int flow_loops_find (struct loops *, int flags); |
259 | extern int flow_loops_update (struct loops *, int flags); | |
260 | extern void flow_loops_free (struct loops *); | |
261 | extern void flow_loops_dump (const struct loops *, FILE *, | |
262 | void (*)(const struct loop *, FILE *, int), int); | |
263 | extern void flow_loop_dump (const struct loop *, FILE *, | |
264 | void (*)(const struct loop *, FILE *, int), int); | |
d47cc544 | 265 | extern int flow_loop_scan (struct loop *, int); |
d329e058 AJ |
266 | extern void flow_loop_free (struct loop *); |
267 | void mark_irreducible_loops (struct loops *); | |
3d436d2a | 268 | |
4d6922ee | 269 | /* Loop data structure manipulation/querying. */ |
d329e058 AJ |
270 | extern void flow_loop_tree_node_add (struct loop *, struct loop *); |
271 | extern void flow_loop_tree_node_remove (struct loop *); | |
272 | extern bool flow_loop_outside_edge_p (const struct loop *, edge); | |
273 | extern bool flow_loop_nested_p (const struct loop *, const struct loop *); | |
274 | extern bool flow_bb_inside_loop_p (const struct loop *, const basic_block); | |
275 | extern struct loop * find_common_loop (struct loop *, struct loop *); | |
276 | extern int num_loop_insns (struct loop *); | |
277 | extern int average_num_loop_insns (struct loop *); | |
3d436d2a ZD |
278 | |
279 | /* Loops & cfg manipulation. */ | |
d329e058 AJ |
280 | extern basic_block *get_loop_body (const struct loop *); |
281 | extern edge *get_loop_exit_edges (const struct loop *, unsigned *); | |
3d436d2a | 282 | |
d329e058 AJ |
283 | extern edge loop_preheader_edge (const struct loop *); |
284 | extern edge loop_latch_edge (const struct loop *); | |
3d436d2a | 285 | |
d329e058 AJ |
286 | extern void add_bb_to_loop (basic_block, struct loop *); |
287 | extern void remove_bb_from_loops (basic_block); | |
3d436d2a | 288 | |
d329e058 AJ |
289 | extern void cancel_loop (struct loops *, struct loop *); |
290 | extern void cancel_loop_tree (struct loops *, struct loop *); | |
3d436d2a | 291 | |
d47cc544 | 292 | extern basic_block loop_split_edge_with (edge, rtx); |
d329e058 | 293 | extern int fix_loop_placement (struct loop *); |
3d436d2a ZD |
294 | |
295 | enum | |
296 | { | |
bc35512f | 297 | CP_SIMPLE_PREHEADERS = 1 |
3d436d2a ZD |
298 | }; |
299 | ||
d329e058 AJ |
300 | extern void create_preheaders (struct loops *, int); |
301 | extern void force_single_succ_latches (struct loops *); | |
3d436d2a | 302 | |
d329e058 | 303 | extern void verify_loop_structure (struct loops *); |
3d436d2a ZD |
304 | |
305 | /* Loop analysis. */ | |
d47cc544 | 306 | extern bool simple_loop_p (struct loop *, struct loop_desc *); |
d329e058 | 307 | extern rtx count_loop_iterations (struct loop_desc *, rtx, rtx); |
d47cc544 | 308 | extern bool just_once_each_iteration_p (struct loop *, basic_block); |
d329e058 | 309 | extern unsigned expected_loop_iterations (const struct loop *); |
617b465c ZD |
310 | |
311 | /* Loop manipulation. */ | |
d329e058 | 312 | extern bool can_duplicate_loop_p (struct loop *loop); |
617b465c ZD |
313 | |
314 | #define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in | |
315 | duplicate_loop_to_header_edge. */ | |
316 | ||
d329e058 AJ |
317 | extern int duplicate_loop_to_header_edge (struct loop *, edge, struct loops *, |
318 | unsigned, sbitmap, edge, edge *, | |
319 | unsigned *, int); | |
320 | extern struct loop *loopify (struct loops *, edge, edge, basic_block); | |
321 | extern void unloop (struct loops *, struct loop *); | |
322 | extern bool remove_path (struct loops *, edge); | |
d47cc544 | 323 | extern edge split_loop_bb (basic_block, rtx); |
617b465c ZD |
324 | |
325 | /* Loop optimizer initialization. */ | |
d329e058 AJ |
326 | extern struct loops *loop_optimizer_init (FILE *); |
327 | extern void loop_optimizer_finalize (struct loops *, FILE *); | |
617b465c ZD |
328 | |
329 | /* Optimization passes. */ | |
d329e058 | 330 | extern void unswitch_loops (struct loops *); |
617b465c | 331 | |
b17d5d7c ZD |
332 | enum |
333 | { | |
334 | UAP_PEEL = 1, /* Enables loop peeling. */ | |
335 | UAP_UNROLL = 2, /* Enables peeling of loops if it seems profitable. */ | |
336 | UAP_UNROLL_ALL = 4 /* Enables peeling of all loops. */ | |
337 | }; | |
338 | ||
d329e058 | 339 | extern void unroll_and_peel_loops (struct loops *, int); |