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5c856b23 JH |
1 | /* The tracer pass for the GNU compiler. |
2 | Contributed by Jan Hubicka, SuSE Labs. | |
232abc3f | 3 | Adapted to work on GIMPLE instead of RTL by Robert Kidd, UIUC. |
66647d44 | 4 | Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 |
6fb5fa3c | 5 | Free Software Foundation, Inc. |
5c856b23 JH |
6 | |
7 | This file is part of GCC. | |
8 | ||
9 | GCC is free software; you can redistribute it and/or modify it | |
10 | under the terms of the GNU General Public License as published by | |
9dcd6f09 | 11 | the Free Software Foundation; either version 3, or (at your option) |
5c856b23 JH |
12 | any later version. |
13 | ||
14 | GCC is distributed in the hope that it will be useful, but WITHOUT | |
15 | ANY WARRANTY; without even the implied warranty of MERCHANTABILITY | |
16 | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public | |
17 | License for more details. | |
18 | ||
19 | You should have received a copy of the GNU General Public License | |
9dcd6f09 NC |
20 | along with GCC; see the file COPYING3. If not see |
21 | <http://www.gnu.org/licenses/>. */ | |
5c856b23 JH |
22 | |
23 | /* This pass performs the tail duplication needed for superblock formation. | |
24 | For more information see: | |
25 | ||
26 | Design and Analysis of Profile-Based Optimization in Compaq's | |
27 | Compilation Tools for Alpha; Journal of Instruction-Level | |
28 | Parallelism 3 (2000) 1-25 | |
29 | ||
30 | Unlike Compaq's implementation we don't do the loop peeling as most | |
31 | probably a better job can be done by a special pass and we don't | |
32 | need to worry too much about the code size implications as the tail | |
33 | duplicates are crossjumped again if optimizations are not | |
34 | performed. */ | |
35 | ||
36 | ||
37 | #include "config.h" | |
38 | #include "system.h" | |
4977bab6 ZW |
39 | #include "coretypes.h" |
40 | #include "tm.h" | |
5c856b23 JH |
41 | #include "tree.h" |
42 | #include "rtl.h" | |
43 | #include "hard-reg-set.h" | |
44 | #include "basic-block.h" | |
5c856b23 JH |
45 | #include "fibheap.h" |
46 | #include "flags.h" | |
47 | #include "params.h" | |
ca29da43 | 48 | #include "coverage.h" |
ef330312 | 49 | #include "tree-pass.h" |
232abc3f RK |
50 | #include "tree-flow.h" |
51 | #include "tree-inline.h" | |
0b9066cf | 52 | #include "cfgloop.h" |
5c856b23 | 53 | |
232abc3f | 54 | static int count_insns (basic_block); |
ed7a4b4b KG |
55 | static bool ignore_bb_p (const_basic_block); |
56 | static bool better_p (const_edge, const_edge); | |
46c5ad27 AJ |
57 | static edge find_best_successor (basic_block); |
58 | static edge find_best_predecessor (basic_block); | |
59 | static int find_trace (basic_block, basic_block *); | |
5c856b23 JH |
60 | |
61 | /* Minimal outgoing edge probability considered for superblock formation. */ | |
62 | static int probability_cutoff; | |
63 | static int branch_ratio_cutoff; | |
64 | ||
232abc3f RK |
65 | /* A bit BB->index is set if BB has already been seen, i.e. it is |
66 | connected to some trace already. */ | |
67 | sbitmap bb_seen; | |
5c856b23 | 68 | |
232abc3f RK |
69 | static inline void |
70 | mark_bb_seen (basic_block bb) | |
71 | { | |
72 | unsigned int size = SBITMAP_SIZE_BYTES (bb_seen) * 8; | |
73 | ||
74 | if ((unsigned int)bb->index >= size) | |
75 | bb_seen = sbitmap_resize (bb_seen, size * 2, 0); | |
76 | ||
77 | SET_BIT (bb_seen, bb->index); | |
78 | } | |
79 | ||
80 | static inline bool | |
81 | bb_seen_p (basic_block bb) | |
82 | { | |
83 | return TEST_BIT (bb_seen, bb->index); | |
84 | } | |
5c856b23 | 85 | |
4b7e68e7 | 86 | /* Return true if we should ignore the basic block for purposes of tracing. */ |
5c856b23 | 87 | static bool |
ed7a4b4b | 88 | ignore_bb_p (const_basic_block bb) |
5c856b23 | 89 | { |
2e85d5e2 PM |
90 | gimple g; |
91 | ||
24bd1a0b | 92 | if (bb->index < NUM_FIXED_BLOCKS) |
5c856b23 | 93 | return true; |
efd8f750 | 94 | if (optimize_bb_for_size_p (bb)) |
5c856b23 | 95 | return true; |
2e85d5e2 PM |
96 | |
97 | /* A transaction is a single entry multiple exit region. It must be | |
98 | duplicated in its entirety or not at all. */ | |
99 | g = last_stmt (CONST_CAST_BB (bb)); | |
100 | if (g && gimple_code (g) == GIMPLE_TRANSACTION) | |
101 | return true; | |
102 | ||
5c856b23 JH |
103 | return false; |
104 | } | |
105 | ||
106 | /* Return number of instructions in the block. */ | |
107 | ||
108 | static int | |
232abc3f | 109 | count_insns (basic_block bb) |
5c856b23 | 110 | { |
726a989a RB |
111 | gimple_stmt_iterator gsi; |
112 | gimple stmt; | |
5c856b23 JH |
113 | int n = 0; |
114 | ||
726a989a | 115 | for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) |
232abc3f | 116 | { |
726a989a | 117 | stmt = gsi_stmt (gsi); |
232abc3f RK |
118 | n += estimate_num_insns (stmt, &eni_size_weights); |
119 | } | |
5c856b23 JH |
120 | return n; |
121 | } | |
122 | ||
123 | /* Return true if E1 is more frequent than E2. */ | |
124 | static bool | |
ed7a4b4b | 125 | better_p (const_edge e1, const_edge e2) |
5c856b23 JH |
126 | { |
127 | if (e1->count != e2->count) | |
128 | return e1->count > e2->count; | |
129 | if (e1->src->frequency * e1->probability != | |
130 | e2->src->frequency * e2->probability) | |
131 | return (e1->src->frequency * e1->probability | |
132 | > e2->src->frequency * e2->probability); | |
133 | /* This is needed to avoid changes in the decision after | |
134 | CFG is modified. */ | |
135 | if (e1->src != e2->src) | |
136 | return e1->src->index > e2->src->index; | |
137 | return e1->dest->index > e2->dest->index; | |
138 | } | |
139 | ||
140 | /* Return most frequent successor of basic block BB. */ | |
141 | ||
142 | static edge | |
46c5ad27 | 143 | find_best_successor (basic_block bb) |
5c856b23 JH |
144 | { |
145 | edge e; | |
146 | edge best = NULL; | |
628f6a4e | 147 | edge_iterator ei; |
5c856b23 | 148 | |
628f6a4e | 149 | FOR_EACH_EDGE (e, ei, bb->succs) |
5c856b23 JH |
150 | if (!best || better_p (e, best)) |
151 | best = e; | |
152 | if (!best || ignore_bb_p (best->dest)) | |
153 | return NULL; | |
154 | if (best->probability <= probability_cutoff) | |
155 | return NULL; | |
156 | return best; | |
157 | } | |
158 | ||
159 | /* Return most frequent predecessor of basic block BB. */ | |
160 | ||
161 | static edge | |
46c5ad27 | 162 | find_best_predecessor (basic_block bb) |
5c856b23 JH |
163 | { |
164 | edge e; | |
165 | edge best = NULL; | |
628f6a4e | 166 | edge_iterator ei; |
5c856b23 | 167 | |
628f6a4e | 168 | FOR_EACH_EDGE (e, ei, bb->preds) |
5c856b23 JH |
169 | if (!best || better_p (e, best)) |
170 | best = e; | |
171 | if (!best || ignore_bb_p (best->src)) | |
172 | return NULL; | |
173 | if (EDGE_FREQUENCY (best) * REG_BR_PROB_BASE | |
174 | < bb->frequency * branch_ratio_cutoff) | |
175 | return NULL; | |
176 | return best; | |
177 | } | |
178 | ||
179 | /* Find the trace using bb and record it in the TRACE array. | |
180 | Return number of basic blocks recorded. */ | |
181 | ||
182 | static int | |
46c5ad27 | 183 | find_trace (basic_block bb, basic_block *trace) |
5c856b23 JH |
184 | { |
185 | int i = 0; | |
186 | edge e; | |
187 | ||
c263766c RH |
188 | if (dump_file) |
189 | fprintf (dump_file, "Trace seed %i [%i]", bb->index, bb->frequency); | |
5c856b23 JH |
190 | |
191 | while ((e = find_best_predecessor (bb)) != NULL) | |
192 | { | |
193 | basic_block bb2 = e->src; | |
232abc3f | 194 | if (bb_seen_p (bb2) || (e->flags & (EDGE_DFS_BACK | EDGE_COMPLEX)) |
5c856b23 JH |
195 | || find_best_successor (bb2) != e) |
196 | break; | |
c263766c RH |
197 | if (dump_file) |
198 | fprintf (dump_file, ",%i [%i]", bb->index, bb->frequency); | |
5c856b23 JH |
199 | bb = bb2; |
200 | } | |
c263766c RH |
201 | if (dump_file) |
202 | fprintf (dump_file, " forward %i [%i]", bb->index, bb->frequency); | |
5c856b23 JH |
203 | trace[i++] = bb; |
204 | ||
205 | /* Follow the trace in forward direction. */ | |
206 | while ((e = find_best_successor (bb)) != NULL) | |
207 | { | |
208 | bb = e->dest; | |
232abc3f | 209 | if (bb_seen_p (bb) || (e->flags & (EDGE_DFS_BACK | EDGE_COMPLEX)) |
5c856b23 JH |
210 | || find_best_predecessor (bb) != e) |
211 | break; | |
c263766c RH |
212 | if (dump_file) |
213 | fprintf (dump_file, ",%i [%i]", bb->index, bb->frequency); | |
5c856b23 JH |
214 | trace[i++] = bb; |
215 | } | |
c263766c RH |
216 | if (dump_file) |
217 | fprintf (dump_file, "\n"); | |
5c856b23 JH |
218 | return i; |
219 | } | |
220 | ||
221 | /* Look for basic blocks in frequency order, construct traces and tail duplicate | |
222 | if profitable. */ | |
223 | ||
07b1bf20 | 224 | static bool |
46c5ad27 | 225 | tail_duplicate (void) |
5c856b23 | 226 | { |
5ed6ace5 MD |
227 | fibnode_t *blocks = XCNEWVEC (fibnode_t, last_basic_block); |
228 | basic_block *trace = XNEWVEC (basic_block, n_basic_blocks); | |
229 | int *counts = XNEWVEC (int, last_basic_block); | |
5c856b23 JH |
230 | int ninsns = 0, nduplicated = 0; |
231 | gcov_type weighted_insns = 0, traced_insns = 0; | |
232 | fibheap_t heap = fibheap_new (); | |
233 | gcov_type cover_insns; | |
234 | int max_dup_insns; | |
235 | basic_block bb; | |
07b1bf20 | 236 | bool changed = false; |
5c856b23 | 237 | |
232abc3f RK |
238 | /* Create an oversized sbitmap to reduce the chance that we need to |
239 | resize it. */ | |
240 | bb_seen = sbitmap_alloc (last_basic_block * 2); | |
241 | sbitmap_zero (bb_seen); | |
242 | initialize_original_copy_tables (); | |
243 | ||
cdb23767 | 244 | if (profile_info && flag_branch_probabilities) |
5c856b23 JH |
245 | probability_cutoff = PARAM_VALUE (TRACER_MIN_BRANCH_PROBABILITY_FEEDBACK); |
246 | else | |
247 | probability_cutoff = PARAM_VALUE (TRACER_MIN_BRANCH_PROBABILITY); | |
248 | probability_cutoff = REG_BR_PROB_BASE / 100 * probability_cutoff; | |
249 | ||
250 | branch_ratio_cutoff = | |
251 | (REG_BR_PROB_BASE / 100 * PARAM_VALUE (TRACER_MIN_BRANCH_RATIO)); | |
252 | ||
253 | FOR_EACH_BB (bb) | |
254 | { | |
255 | int n = count_insns (bb); | |
256 | if (!ignore_bb_p (bb)) | |
257 | blocks[bb->index] = fibheap_insert (heap, -bb->frequency, | |
258 | bb); | |
259 | ||
260 | counts [bb->index] = n; | |
261 | ninsns += n; | |
262 | weighted_insns += n * bb->frequency; | |
263 | } | |
264 | ||
cdb23767 | 265 | if (profile_info && flag_branch_probabilities) |
5c856b23 JH |
266 | cover_insns = PARAM_VALUE (TRACER_DYNAMIC_COVERAGE_FEEDBACK); |
267 | else | |
268 | cover_insns = PARAM_VALUE (TRACER_DYNAMIC_COVERAGE); | |
269 | cover_insns = (weighted_insns * cover_insns + 50) / 100; | |
270 | max_dup_insns = (ninsns * PARAM_VALUE (TRACER_MAX_CODE_GROWTH) + 50) / 100; | |
271 | ||
272 | while (traced_insns < cover_insns && nduplicated < max_dup_insns | |
273 | && !fibheap_empty (heap)) | |
274 | { | |
3d9a9f94 | 275 | basic_block bb = (basic_block) fibheap_extract_min (heap); |
5c856b23 JH |
276 | int n, pos; |
277 | ||
278 | if (!bb) | |
279 | break; | |
280 | ||
281 | blocks[bb->index] = NULL; | |
282 | ||
283 | if (ignore_bb_p (bb)) | |
284 | continue; | |
232abc3f | 285 | gcc_assert (!bb_seen_p (bb)); |
5c856b23 JH |
286 | |
287 | n = find_trace (bb, trace); | |
288 | ||
289 | bb = trace[0]; | |
290 | traced_insns += bb->frequency * counts [bb->index]; | |
291 | if (blocks[bb->index]) | |
292 | { | |
293 | fibheap_delete_node (heap, blocks[bb->index]); | |
294 | blocks[bb->index] = NULL; | |
295 | } | |
296 | ||
297 | for (pos = 1; pos < n; pos++) | |
298 | { | |
299 | basic_block bb2 = trace[pos]; | |
300 | ||
301 | if (blocks[bb2->index]) | |
302 | { | |
303 | fibheap_delete_node (heap, blocks[bb2->index]); | |
304 | blocks[bb2->index] = NULL; | |
305 | } | |
306 | traced_insns += bb2->frequency * counts [bb2->index]; | |
628f6a4e | 307 | if (EDGE_COUNT (bb2->preds) > 1 |
0b9066cf RG |
308 | && can_duplicate_block_p (bb2) |
309 | /* We have the tendency to duplicate the loop header | |
310 | of all do { } while loops. Do not do that - it is | |
311 | not profitable and it might create a loop with multiple | |
312 | entries or at least rotate the loop. */ | |
313 | && (!current_loops | |
314 | || bb2->loop_father->header != bb2)) | |
5c856b23 | 315 | { |
628f6a4e | 316 | edge e; |
232abc3f RK |
317 | basic_block copy; |
318 | ||
319 | nduplicated += counts [bb2->index]; | |
5c856b23 | 320 | |
9ff3d2de | 321 | e = find_edge (bb, bb2); |
b8698a0f | 322 | |
232abc3f RK |
323 | copy = duplicate_block (bb2, e, bb); |
324 | flush_pending_stmts (e); | |
628f6a4e | 325 | |
5f40b3cb | 326 | add_phi_args_after_copy (©, 1, NULL); |
5c856b23 JH |
327 | |
328 | /* Reconsider the original copy of block we've duplicated. | |
14b493d6 | 329 | Removing the most common predecessor may make it to be |
5c856b23 | 330 | head. */ |
232abc3f RK |
331 | blocks[bb2->index] = |
332 | fibheap_insert (heap, -bb2->frequency, bb2); | |
5c856b23 | 333 | |
c263766c RH |
334 | if (dump_file) |
335 | fprintf (dump_file, "Duplicated %i as %i [%i]\n", | |
232abc3f RK |
336 | bb2->index, copy->index, copy->frequency); |
337 | ||
338 | bb2 = copy; | |
07b1bf20 | 339 | changed = true; |
5c856b23 | 340 | } |
232abc3f | 341 | mark_bb_seen (bb2); |
5c856b23 JH |
342 | bb = bb2; |
343 | /* In case the trace became infrequent, stop duplicating. */ | |
344 | if (ignore_bb_p (bb)) | |
345 | break; | |
346 | } | |
c263766c RH |
347 | if (dump_file) |
348 | fprintf (dump_file, " covered now %.1f\n\n", | |
5c856b23 JH |
349 | traced_insns * 100.0 / weighted_insns); |
350 | } | |
c263766c RH |
351 | if (dump_file) |
352 | fprintf (dump_file, "Duplicated %i insns (%i%%)\n", nduplicated, | |
5c856b23 JH |
353 | nduplicated * 100 / ninsns); |
354 | ||
232abc3f RK |
355 | free_original_copy_tables (); |
356 | sbitmap_free (bb_seen); | |
5c856b23 JH |
357 | free (blocks); |
358 | free (trace); | |
359 | free (counts); | |
360 | fibheap_delete (heap); | |
07b1bf20 RG |
361 | |
362 | return changed; | |
5c856b23 JH |
363 | } |
364 | ||
ad21dab7 | 365 | /* Main entry point to this file. */ |
5c856b23 | 366 | |
232abc3f | 367 | static unsigned int |
ad21dab7 | 368 | tracer (void) |
5c856b23 | 369 | { |
07b1bf20 RG |
370 | bool changed; |
371 | ||
24bd1a0b | 372 | if (n_basic_blocks <= NUM_FIXED_BLOCKS + 1) |
232abc3f | 373 | return 0; |
38700cee | 374 | |
5c856b23 | 375 | mark_dfs_back_edges (); |
c263766c | 376 | if (dump_file) |
c4669594 | 377 | brief_dump_cfg (dump_file, dump_flags); |
232abc3f RK |
378 | |
379 | /* Trace formation is done on the fly inside tail_duplicate */ | |
07b1bf20 RG |
380 | changed = tail_duplicate (); |
381 | if (changed) | |
382 | free_dominance_info (CDI_DOMINATORS); | |
232abc3f | 383 | |
c263766c | 384 | if (dump_file) |
c4669594 | 385 | brief_dump_cfg (dump_file, dump_flags); |
38700cee | 386 | |
07b1bf20 | 387 | return changed ? TODO_cleanup_cfg : 0; |
ef330312 PB |
388 | } |
389 | \f | |
390 | static bool | |
232abc3f | 391 | gate_tracer (void) |
ef330312 | 392 | { |
232abc3f | 393 | return (optimize > 0 && flag_tracer && flag_reorder_blocks); |
5c856b23 | 394 | } |
ef330312 | 395 | |
8ddbbcae | 396 | struct gimple_opt_pass pass_tracer = |
ef330312 | 397 | { |
8ddbbcae JH |
398 | { |
399 | GIMPLE_PASS, | |
ef330312 | 400 | "tracer", /* name */ |
232abc3f RK |
401 | gate_tracer, /* gate */ |
402 | tracer, /* execute */ | |
ef330312 PB |
403 | NULL, /* sub */ |
404 | NULL, /* next */ | |
405 | 0, /* static_pass_number */ | |
406 | TV_TRACER, /* tv_id */ | |
407 | 0, /* properties_required */ | |
408 | 0, /* properties_provided */ | |
409 | 0, /* properties_destroyed */ | |
410 | 0, /* todo_flags_start */ | |
22c5fa5f | 411 | TODO_update_ssa |
8ddbbcae JH |
412 | | TODO_verify_ssa /* todo_flags_finish */ |
413 | } | |
ef330312 | 414 | }; |