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5c856b23 JH |
1 | /* The tracer pass for the GNU compiler. |
2 | Contributed by Jan Hubicka, SuSE Labs. | |
88462c42 | 3 | Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc. |
5c856b23 JH |
4 | |
5 | This file is part of GCC. | |
6 | ||
7 | GCC is free software; you can redistribute it and/or modify it | |
8 | under the terms of the GNU General Public License as published by | |
9 | the Free Software Foundation; either version 2, or (at your option) | |
10 | any later version. | |
11 | ||
12 | GCC is distributed in the hope that it will be useful, but WITHOUT | |
13 | ANY WARRANTY; without even the implied warranty of MERCHANTABILITY | |
14 | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public | |
15 | License 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 | /* This pass performs the tail duplication needed for superblock formation. | |
23 | For more information see: | |
24 | ||
25 | Design and Analysis of Profile-Based Optimization in Compaq's | |
26 | Compilation Tools for Alpha; Journal of Instruction-Level | |
27 | Parallelism 3 (2000) 1-25 | |
28 | ||
29 | Unlike Compaq's implementation we don't do the loop peeling as most | |
30 | probably a better job can be done by a special pass and we don't | |
31 | need to worry too much about the code size implications as the tail | |
32 | duplicates are crossjumped again if optimizations are not | |
33 | performed. */ | |
34 | ||
35 | ||
36 | #include "config.h" | |
37 | #include "system.h" | |
4977bab6 ZW |
38 | #include "coretypes.h" |
39 | #include "tm.h" | |
5c856b23 JH |
40 | #include "tree.h" |
41 | #include "rtl.h" | |
42 | #include "hard-reg-set.h" | |
43 | #include "basic-block.h" | |
44 | #include "output.h" | |
45 | #include "cfglayout.h" | |
46 | #include "fibheap.h" | |
47 | #include "flags.h" | |
38700cee | 48 | #include "timevar.h" |
5c856b23 | 49 | #include "params.h" |
ca29da43 | 50 | #include "coverage.h" |
5c856b23 | 51 | |
46c5ad27 AJ |
52 | static int count_insns (basic_block); |
53 | static bool ignore_bb_p (basic_block); | |
54 | static bool better_p (edge, edge); | |
55 | static edge find_best_successor (basic_block); | |
56 | static edge find_best_predecessor (basic_block); | |
57 | static int find_trace (basic_block, basic_block *); | |
58 | static void tail_duplicate (void); | |
59 | static void layout_superblocks (void); | |
5c856b23 JH |
60 | |
61 | /* Minimal outgoing edge probability considered for superblock formation. */ | |
62 | static int probability_cutoff; | |
63 | static int branch_ratio_cutoff; | |
64 | ||
65 | /* Return true if BB has been seen - it is connected to some trace | |
66 | already. */ | |
67 | ||
bc35512f | 68 | #define seen(bb) (bb->rbi->visited || bb->rbi->next) |
5c856b23 | 69 | |
4b7e68e7 | 70 | /* Return true if we should ignore the basic block for purposes of tracing. */ |
5c856b23 | 71 | static bool |
46c5ad27 | 72 | ignore_bb_p (basic_block bb) |
5c856b23 JH |
73 | { |
74 | if (bb->index < 0) | |
75 | return true; | |
76 | if (!maybe_hot_bb_p (bb)) | |
77 | return true; | |
78 | return false; | |
79 | } | |
80 | ||
81 | /* Return number of instructions in the block. */ | |
82 | ||
83 | static int | |
46c5ad27 | 84 | count_insns (basic_block bb) |
5c856b23 JH |
85 | { |
86 | rtx insn; | |
87 | int n = 0; | |
88 | ||
a813c111 SB |
89 | for (insn = BB_HEAD (bb); |
90 | insn != NEXT_INSN (BB_END (bb)); | |
91 | insn = NEXT_INSN (insn)) | |
5c856b23 JH |
92 | if (active_insn_p (insn)) |
93 | n++; | |
94 | return n; | |
95 | } | |
96 | ||
97 | /* Return true if E1 is more frequent than E2. */ | |
98 | static bool | |
46c5ad27 | 99 | better_p (edge e1, edge e2) |
5c856b23 JH |
100 | { |
101 | if (e1->count != e2->count) | |
102 | return e1->count > e2->count; | |
103 | if (e1->src->frequency * e1->probability != | |
104 | e2->src->frequency * e2->probability) | |
105 | return (e1->src->frequency * e1->probability | |
106 | > e2->src->frequency * e2->probability); | |
107 | /* This is needed to avoid changes in the decision after | |
108 | CFG is modified. */ | |
109 | if (e1->src != e2->src) | |
110 | return e1->src->index > e2->src->index; | |
111 | return e1->dest->index > e2->dest->index; | |
112 | } | |
113 | ||
114 | /* Return most frequent successor of basic block BB. */ | |
115 | ||
116 | static edge | |
46c5ad27 | 117 | find_best_successor (basic_block bb) |
5c856b23 JH |
118 | { |
119 | edge e; | |
120 | edge best = NULL; | |
121 | ||
122 | for (e = bb->succ; e; e = e->succ_next) | |
123 | if (!best || better_p (e, best)) | |
124 | best = e; | |
125 | if (!best || ignore_bb_p (best->dest)) | |
126 | return NULL; | |
127 | if (best->probability <= probability_cutoff) | |
128 | return NULL; | |
129 | return best; | |
130 | } | |
131 | ||
132 | /* Return most frequent predecessor of basic block BB. */ | |
133 | ||
134 | static edge | |
46c5ad27 | 135 | find_best_predecessor (basic_block bb) |
5c856b23 JH |
136 | { |
137 | edge e; | |
138 | edge best = NULL; | |
139 | ||
140 | for (e = bb->pred; e; e = e->pred_next) | |
141 | if (!best || better_p (e, best)) | |
142 | best = e; | |
143 | if (!best || ignore_bb_p (best->src)) | |
144 | return NULL; | |
145 | if (EDGE_FREQUENCY (best) * REG_BR_PROB_BASE | |
146 | < bb->frequency * branch_ratio_cutoff) | |
147 | return NULL; | |
148 | return best; | |
149 | } | |
150 | ||
151 | /* Find the trace using bb and record it in the TRACE array. | |
152 | Return number of basic blocks recorded. */ | |
153 | ||
154 | static int | |
46c5ad27 | 155 | find_trace (basic_block bb, basic_block *trace) |
5c856b23 JH |
156 | { |
157 | int i = 0; | |
158 | edge e; | |
159 | ||
c263766c RH |
160 | if (dump_file) |
161 | fprintf (dump_file, "Trace seed %i [%i]", bb->index, bb->frequency); | |
5c856b23 JH |
162 | |
163 | while ((e = find_best_predecessor (bb)) != NULL) | |
164 | { | |
165 | basic_block bb2 = e->src; | |
166 | if (seen (bb2) || (e->flags & (EDGE_DFS_BACK | EDGE_COMPLEX)) | |
167 | || find_best_successor (bb2) != e) | |
168 | break; | |
c263766c RH |
169 | if (dump_file) |
170 | fprintf (dump_file, ",%i [%i]", bb->index, bb->frequency); | |
5c856b23 JH |
171 | bb = bb2; |
172 | } | |
c263766c RH |
173 | if (dump_file) |
174 | fprintf (dump_file, " forward %i [%i]", bb->index, bb->frequency); | |
5c856b23 JH |
175 | trace[i++] = bb; |
176 | ||
177 | /* Follow the trace in forward direction. */ | |
178 | while ((e = find_best_successor (bb)) != NULL) | |
179 | { | |
180 | bb = e->dest; | |
181 | if (seen (bb) || (e->flags & (EDGE_DFS_BACK | EDGE_COMPLEX)) | |
182 | || find_best_predecessor (bb) != e) | |
183 | break; | |
c263766c RH |
184 | if (dump_file) |
185 | fprintf (dump_file, ",%i [%i]", bb->index, bb->frequency); | |
5c856b23 JH |
186 | trace[i++] = bb; |
187 | } | |
c263766c RH |
188 | if (dump_file) |
189 | fprintf (dump_file, "\n"); | |
5c856b23 JH |
190 | return i; |
191 | } | |
192 | ||
193 | /* Look for basic blocks in frequency order, construct traces and tail duplicate | |
194 | if profitable. */ | |
195 | ||
196 | static void | |
46c5ad27 | 197 | tail_duplicate (void) |
5c856b23 JH |
198 | { |
199 | fibnode_t *blocks = xcalloc (last_basic_block, sizeof (fibnode_t)); | |
200 | basic_block *trace = xmalloc (sizeof (basic_block) * n_basic_blocks); | |
201 | int *counts = xmalloc (sizeof (int) * last_basic_block); | |
202 | int ninsns = 0, nduplicated = 0; | |
203 | gcov_type weighted_insns = 0, traced_insns = 0; | |
204 | fibheap_t heap = fibheap_new (); | |
205 | gcov_type cover_insns; | |
206 | int max_dup_insns; | |
207 | basic_block bb; | |
208 | ||
cdb23767 | 209 | if (profile_info && flag_branch_probabilities) |
5c856b23 JH |
210 | probability_cutoff = PARAM_VALUE (TRACER_MIN_BRANCH_PROBABILITY_FEEDBACK); |
211 | else | |
212 | probability_cutoff = PARAM_VALUE (TRACER_MIN_BRANCH_PROBABILITY); | |
213 | probability_cutoff = REG_BR_PROB_BASE / 100 * probability_cutoff; | |
214 | ||
215 | branch_ratio_cutoff = | |
216 | (REG_BR_PROB_BASE / 100 * PARAM_VALUE (TRACER_MIN_BRANCH_RATIO)); | |
217 | ||
218 | FOR_EACH_BB (bb) | |
219 | { | |
220 | int n = count_insns (bb); | |
221 | if (!ignore_bb_p (bb)) | |
222 | blocks[bb->index] = fibheap_insert (heap, -bb->frequency, | |
223 | bb); | |
224 | ||
225 | counts [bb->index] = n; | |
226 | ninsns += n; | |
227 | weighted_insns += n * bb->frequency; | |
228 | } | |
229 | ||
cdb23767 | 230 | if (profile_info && flag_branch_probabilities) |
5c856b23 JH |
231 | cover_insns = PARAM_VALUE (TRACER_DYNAMIC_COVERAGE_FEEDBACK); |
232 | else | |
233 | cover_insns = PARAM_VALUE (TRACER_DYNAMIC_COVERAGE); | |
234 | cover_insns = (weighted_insns * cover_insns + 50) / 100; | |
235 | max_dup_insns = (ninsns * PARAM_VALUE (TRACER_MAX_CODE_GROWTH) + 50) / 100; | |
236 | ||
237 | while (traced_insns < cover_insns && nduplicated < max_dup_insns | |
238 | && !fibheap_empty (heap)) | |
239 | { | |
240 | basic_block bb = fibheap_extract_min (heap); | |
241 | int n, pos; | |
242 | ||
243 | if (!bb) | |
244 | break; | |
245 | ||
246 | blocks[bb->index] = NULL; | |
247 | ||
248 | if (ignore_bb_p (bb)) | |
249 | continue; | |
250 | if (seen (bb)) | |
251 | abort (); | |
252 | ||
253 | n = find_trace (bb, trace); | |
254 | ||
255 | bb = trace[0]; | |
256 | traced_insns += bb->frequency * counts [bb->index]; | |
257 | if (blocks[bb->index]) | |
258 | { | |
259 | fibheap_delete_node (heap, blocks[bb->index]); | |
260 | blocks[bb->index] = NULL; | |
261 | } | |
262 | ||
263 | for (pos = 1; pos < n; pos++) | |
264 | { | |
265 | basic_block bb2 = trace[pos]; | |
266 | ||
267 | if (blocks[bb2->index]) | |
268 | { | |
269 | fibheap_delete_node (heap, blocks[bb2->index]); | |
270 | blocks[bb2->index] = NULL; | |
271 | } | |
272 | traced_insns += bb2->frequency * counts [bb2->index]; | |
273 | if (bb2->pred && bb2->pred->pred_next | |
6de9cd9a | 274 | && can_duplicate_block_p (bb2)) |
5c856b23 JH |
275 | { |
276 | edge e = bb2->pred; | |
277 | basic_block old = bb2; | |
278 | ||
279 | while (e->src != bb) | |
280 | e = e->pred_next; | |
281 | nduplicated += counts [bb2->index]; | |
6de9cd9a | 282 | bb2 = duplicate_block (bb2, e); |
5c856b23 JH |
283 | |
284 | /* Reconsider the original copy of block we've duplicated. | |
14b493d6 | 285 | Removing the most common predecessor may make it to be |
5c856b23 JH |
286 | head. */ |
287 | blocks[old->index] = | |
288 | fibheap_insert (heap, -old->frequency, old); | |
289 | ||
c263766c RH |
290 | if (dump_file) |
291 | fprintf (dump_file, "Duplicated %i as %i [%i]\n", | |
5c856b23 JH |
292 | old->index, bb2->index, bb2->frequency); |
293 | } | |
bc35512f JH |
294 | bb->rbi->next = bb2; |
295 | bb2->rbi->visited = 1; | |
5c856b23 JH |
296 | bb = bb2; |
297 | /* In case the trace became infrequent, stop duplicating. */ | |
298 | if (ignore_bb_p (bb)) | |
299 | break; | |
300 | } | |
c263766c RH |
301 | if (dump_file) |
302 | fprintf (dump_file, " covered now %.1f\n\n", | |
5c856b23 JH |
303 | traced_insns * 100.0 / weighted_insns); |
304 | } | |
c263766c RH |
305 | if (dump_file) |
306 | fprintf (dump_file, "Duplicated %i insns (%i%%)\n", nduplicated, | |
5c856b23 JH |
307 | nduplicated * 100 / ninsns); |
308 | ||
309 | free (blocks); | |
310 | free (trace); | |
311 | free (counts); | |
312 | fibheap_delete (heap); | |
313 | } | |
314 | ||
4d6922ee | 315 | /* Connect the superblocks into linear sequence. At the moment we attempt to keep |
5c856b23 JH |
316 | the original order as much as possible, but the algorithm may be made smarter |
317 | later if needed. BB reordering pass should void most of the benefits of such | |
318 | change though. */ | |
319 | ||
320 | static void | |
46c5ad27 | 321 | layout_superblocks (void) |
5c856b23 JH |
322 | { |
323 | basic_block end = ENTRY_BLOCK_PTR->succ->dest; | |
324 | basic_block bb = ENTRY_BLOCK_PTR->succ->dest->next_bb; | |
325 | ||
326 | while (bb != EXIT_BLOCK_PTR) | |
327 | { | |
328 | edge e, best = NULL; | |
bc35512f JH |
329 | while (end->rbi->next) |
330 | end = end->rbi->next; | |
5c856b23 JH |
331 | |
332 | for (e = end->succ; e; e = e->succ_next) | |
333 | if (e->dest != EXIT_BLOCK_PTR | |
334 | && e->dest != ENTRY_BLOCK_PTR->succ->dest | |
bc35512f | 335 | && !e->dest->rbi->visited |
5c856b23 JH |
336 | && (!best || EDGE_FREQUENCY (e) > EDGE_FREQUENCY (best))) |
337 | best = e; | |
338 | ||
339 | if (best) | |
340 | { | |
bc35512f JH |
341 | end->rbi->next = best->dest; |
342 | best->dest->rbi->visited = 1; | |
5c856b23 JH |
343 | } |
344 | else | |
6a87d634 | 345 | for (; bb != EXIT_BLOCK_PTR; bb = bb->next_bb) |
5c856b23 | 346 | { |
bc35512f | 347 | if (!bb->rbi->visited) |
5c856b23 | 348 | { |
bc35512f JH |
349 | end->rbi->next = bb; |
350 | bb->rbi->visited = 1; | |
5c856b23 JH |
351 | break; |
352 | } | |
353 | } | |
354 | } | |
355 | } | |
356 | ||
357 | /* Main entry point to this file. */ | |
358 | ||
359 | void | |
46c5ad27 | 360 | tracer (void) |
5c856b23 JH |
361 | { |
362 | if (n_basic_blocks <= 1) | |
363 | return; | |
38700cee SB |
364 | |
365 | timevar_push (TV_TRACER); | |
366 | ||
bc35512f | 367 | cfg_layout_initialize (); |
5c856b23 | 368 | mark_dfs_back_edges (); |
c263766c RH |
369 | if (dump_file) |
370 | dump_flow_info (dump_file); | |
5c856b23 JH |
371 | tail_duplicate (); |
372 | layout_superblocks (); | |
c263766c RH |
373 | if (dump_file) |
374 | dump_flow_info (dump_file); | |
5c856b23 | 375 | cfg_layout_finalize (); |
38700cee | 376 | |
5c856b23 JH |
377 | /* Merge basic blocks in duplicated traces. */ |
378 | cleanup_cfg (CLEANUP_EXPENSIVE); | |
38700cee SB |
379 | |
380 | timevar_pop (TV_TRACER); | |
5c856b23 | 381 | } |