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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. |
cbe34bb5 | 4 | Copyright (C) 2001-2017 Free Software Foundation, Inc. |
5c856b23 JH |
5 | |
6 | This file is part of GCC. | |
7 | ||
8 | GCC is free software; you can redistribute it and/or modify it | |
9 | under the terms of the GNU General Public License as published by | |
9dcd6f09 | 10 | the Free Software Foundation; either version 3, or (at your option) |
5c856b23 JH |
11 | any later version. |
12 | ||
13 | GCC is distributed in the hope that it will be useful, but WITHOUT | |
14 | ANY WARRANTY; without even the implied warranty of MERCHANTABILITY | |
15 | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public | |
16 | License for more details. | |
17 | ||
18 | You should have received a copy of the GNU General Public License | |
9dcd6f09 NC |
19 | along with GCC; see the file COPYING3. If not see |
20 | <http://www.gnu.org/licenses/>. */ | |
5c856b23 JH |
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 | 38 | #include "coretypes.h" |
c7131fb2 | 39 | #include "backend.h" |
957060b5 | 40 | #include "rtl.h" |
5c856b23 | 41 | #include "tree.h" |
c7131fb2 | 42 | #include "gimple.h" |
957060b5 AM |
43 | #include "cfghooks.h" |
44 | #include "tree-pass.h" | |
59f2e9d8 | 45 | #include "profile.h" |
60393bbc | 46 | #include "cfganal.h" |
5c856b23 | 47 | #include "params.h" |
5be5c238 | 48 | #include "gimple-iterator.h" |
442b4905 | 49 | #include "tree-cfg.h" |
7a300452 | 50 | #include "tree-ssa.h" |
232abc3f | 51 | #include "tree-inline.h" |
0b9066cf | 52 | #include "cfgloop.h" |
dd7bda5e | 53 | #include "fibonacci_heap.h" |
8fe17e23 | 54 | #include "tracer.h" |
5c856b23 | 55 | |
232abc3f | 56 | static int count_insns (basic_block); |
ed7a4b4b | 57 | static bool better_p (const_edge, const_edge); |
46c5ad27 AJ |
58 | static edge find_best_successor (basic_block); |
59 | static edge find_best_predecessor (basic_block); | |
60 | static int find_trace (basic_block, basic_block *); | |
5c856b23 JH |
61 | |
62 | /* Minimal outgoing edge probability considered for superblock formation. */ | |
63 | static int probability_cutoff; | |
64 | static int branch_ratio_cutoff; | |
65 | ||
232abc3f RK |
66 | /* A bit BB->index is set if BB has already been seen, i.e. it is |
67 | connected to some trace already. */ | |
7ff75c49 | 68 | static sbitmap bb_seen; |
5c856b23 | 69 | |
232abc3f RK |
70 | static inline void |
71 | mark_bb_seen (basic_block bb) | |
72 | { | |
131db6b8 | 73 | unsigned int size = SBITMAP_SIZE (bb_seen); |
232abc3f RK |
74 | |
75 | if ((unsigned int)bb->index >= size) | |
76 | bb_seen = sbitmap_resize (bb_seen, size * 2, 0); | |
77 | ||
d7c028c0 | 78 | bitmap_set_bit (bb_seen, bb->index); |
232abc3f RK |
79 | } |
80 | ||
81 | static inline bool | |
82 | bb_seen_p (basic_block bb) | |
83 | { | |
d7c028c0 | 84 | return bitmap_bit_p (bb_seen, bb->index); |
232abc3f | 85 | } |
5c856b23 | 86 | |
4b7e68e7 | 87 | /* Return true if we should ignore the basic block for purposes of tracing. */ |
8fe17e23 | 88 | bool |
ed7a4b4b | 89 | ignore_bb_p (const_basic_block bb) |
5c856b23 | 90 | { |
24bd1a0b | 91 | if (bb->index < NUM_FIXED_BLOCKS) |
5c856b23 | 92 | return true; |
efd8f750 | 93 | if (optimize_bb_for_size_p (bb)) |
5c856b23 | 94 | return true; |
2e85d5e2 | 95 | |
8ab78162 NS |
96 | if (gimple *g = last_stmt (CONST_CAST_BB (bb))) |
97 | { | |
98 | /* A transaction is a single entry multiple exit region. It | |
99 | must be duplicated in its entirety or not at all. */ | |
100 | if (gimple_code (g) == GIMPLE_TRANSACTION) | |
101 | return true; | |
102 | ||
103 | /* An IFN_UNIQUE call must be duplicated as part of its group, | |
104 | or not at all. */ | |
105 | if (is_gimple_call (g) | |
106 | && gimple_call_internal_p (g) | |
107 | && gimple_call_internal_unique_p (g)) | |
108 | return true; | |
109 | } | |
2e85d5e2 | 110 | |
5c856b23 JH |
111 | return false; |
112 | } | |
113 | ||
114 | /* Return number of instructions in the block. */ | |
115 | ||
116 | static int | |
232abc3f | 117 | count_insns (basic_block bb) |
5c856b23 | 118 | { |
726a989a | 119 | gimple_stmt_iterator gsi; |
355fe088 | 120 | gimple *stmt; |
5c856b23 JH |
121 | int n = 0; |
122 | ||
726a989a | 123 | for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) |
232abc3f | 124 | { |
726a989a | 125 | stmt = gsi_stmt (gsi); |
232abc3f RK |
126 | n += estimate_num_insns (stmt, &eni_size_weights); |
127 | } | |
5c856b23 JH |
128 | return n; |
129 | } | |
130 | ||
131 | /* Return true if E1 is more frequent than E2. */ | |
132 | static bool | |
ed7a4b4b | 133 | better_p (const_edge e1, const_edge e2) |
5c856b23 | 134 | { |
3995f3a2 JH |
135 | if (e1->count.initialized_p () && e2->count.initialized_p () |
136 | && !(e1->count == e2->count)) | |
5c856b23 JH |
137 | return e1->count > e2->count; |
138 | if (e1->src->frequency * e1->probability != | |
139 | e2->src->frequency * e2->probability) | |
140 | return (e1->src->frequency * e1->probability | |
141 | > e2->src->frequency * e2->probability); | |
142 | /* This is needed to avoid changes in the decision after | |
143 | CFG is modified. */ | |
144 | if (e1->src != e2->src) | |
145 | return e1->src->index > e2->src->index; | |
146 | return e1->dest->index > e2->dest->index; | |
147 | } | |
148 | ||
149 | /* Return most frequent successor of basic block BB. */ | |
150 | ||
151 | static edge | |
46c5ad27 | 152 | find_best_successor (basic_block bb) |
5c856b23 JH |
153 | { |
154 | edge e; | |
155 | edge best = NULL; | |
628f6a4e | 156 | edge_iterator ei; |
5c856b23 | 157 | |
628f6a4e | 158 | FOR_EACH_EDGE (e, ei, bb->succs) |
5c856b23 JH |
159 | if (!best || better_p (e, best)) |
160 | best = e; | |
161 | if (!best || ignore_bb_p (best->dest)) | |
162 | return NULL; | |
163 | if (best->probability <= probability_cutoff) | |
164 | return NULL; | |
165 | return best; | |
166 | } | |
167 | ||
168 | /* Return most frequent predecessor of basic block BB. */ | |
169 | ||
170 | static edge | |
46c5ad27 | 171 | find_best_predecessor (basic_block bb) |
5c856b23 JH |
172 | { |
173 | edge e; | |
174 | edge best = NULL; | |
628f6a4e | 175 | edge_iterator ei; |
5c856b23 | 176 | |
628f6a4e | 177 | FOR_EACH_EDGE (e, ei, bb->preds) |
5c856b23 JH |
178 | if (!best || better_p (e, best)) |
179 | best = e; | |
180 | if (!best || ignore_bb_p (best->src)) | |
181 | return NULL; | |
182 | if (EDGE_FREQUENCY (best) * REG_BR_PROB_BASE | |
183 | < bb->frequency * branch_ratio_cutoff) | |
184 | return NULL; | |
185 | return best; | |
186 | } | |
187 | ||
188 | /* Find the trace using bb and record it in the TRACE array. | |
189 | Return number of basic blocks recorded. */ | |
190 | ||
191 | static int | |
46c5ad27 | 192 | find_trace (basic_block bb, basic_block *trace) |
5c856b23 JH |
193 | { |
194 | int i = 0; | |
195 | edge e; | |
196 | ||
c263766c RH |
197 | if (dump_file) |
198 | fprintf (dump_file, "Trace seed %i [%i]", bb->index, bb->frequency); | |
5c856b23 JH |
199 | |
200 | while ((e = find_best_predecessor (bb)) != NULL) | |
201 | { | |
202 | basic_block bb2 = e->src; | |
232abc3f | 203 | if (bb_seen_p (bb2) || (e->flags & (EDGE_DFS_BACK | EDGE_COMPLEX)) |
5c856b23 JH |
204 | || find_best_successor (bb2) != e) |
205 | break; | |
c263766c RH |
206 | if (dump_file) |
207 | fprintf (dump_file, ",%i [%i]", bb->index, bb->frequency); | |
5c856b23 JH |
208 | bb = bb2; |
209 | } | |
c263766c RH |
210 | if (dump_file) |
211 | fprintf (dump_file, " forward %i [%i]", bb->index, bb->frequency); | |
5c856b23 JH |
212 | trace[i++] = bb; |
213 | ||
214 | /* Follow the trace in forward direction. */ | |
215 | while ((e = find_best_successor (bb)) != NULL) | |
216 | { | |
217 | bb = e->dest; | |
232abc3f | 218 | if (bb_seen_p (bb) || (e->flags & (EDGE_DFS_BACK | EDGE_COMPLEX)) |
5c856b23 JH |
219 | || find_best_predecessor (bb) != e) |
220 | break; | |
c263766c RH |
221 | if (dump_file) |
222 | fprintf (dump_file, ",%i [%i]", bb->index, bb->frequency); | |
5c856b23 JH |
223 | trace[i++] = bb; |
224 | } | |
c263766c RH |
225 | if (dump_file) |
226 | fprintf (dump_file, "\n"); | |
5c856b23 JH |
227 | return i; |
228 | } | |
229 | ||
8fe17e23 AA |
230 | /* Duplicate block BB2, placing it after BB in the CFG. Return the |
231 | newly created block. */ | |
232 | basic_block | |
233 | transform_duplicate (basic_block bb, basic_block bb2) | |
234 | { | |
235 | edge e; | |
236 | basic_block copy; | |
237 | ||
238 | e = find_edge (bb, bb2); | |
239 | ||
240 | copy = duplicate_block (bb2, e, bb); | |
241 | flush_pending_stmts (e); | |
242 | ||
243 | add_phi_args_after_copy (©, 1, NULL); | |
244 | ||
245 | return (copy); | |
246 | } | |
247 | ||
5c856b23 JH |
248 | /* Look for basic blocks in frequency order, construct traces and tail duplicate |
249 | if profitable. */ | |
250 | ||
07b1bf20 | 251 | static bool |
46c5ad27 | 252 | tail_duplicate (void) |
5c856b23 | 253 | { |
dd7bda5e ML |
254 | auto_vec<fibonacci_node<long, basic_block_def>*> blocks; |
255 | blocks.safe_grow_cleared (last_basic_block_for_fn (cfun)); | |
256 | ||
0cae8d31 | 257 | basic_block *trace = XNEWVEC (basic_block, n_basic_blocks_for_fn (cfun)); |
8b1c6fd7 | 258 | int *counts = XNEWVEC (int, last_basic_block_for_fn (cfun)); |
5c856b23 JH |
259 | int ninsns = 0, nduplicated = 0; |
260 | gcov_type weighted_insns = 0, traced_insns = 0; | |
dd7bda5e | 261 | fibonacci_heap<long, basic_block_def> heap (LONG_MIN); |
5c856b23 JH |
262 | gcov_type cover_insns; |
263 | int max_dup_insns; | |
264 | basic_block bb; | |
07b1bf20 | 265 | bool changed = false; |
5c856b23 | 266 | |
232abc3f RK |
267 | /* Create an oversized sbitmap to reduce the chance that we need to |
268 | resize it. */ | |
8b1c6fd7 | 269 | bb_seen = sbitmap_alloc (last_basic_block_for_fn (cfun) * 2); |
f61e445a | 270 | bitmap_clear (bb_seen); |
232abc3f RK |
271 | initialize_original_copy_tables (); |
272 | ||
cdb23767 | 273 | if (profile_info && flag_branch_probabilities) |
5c856b23 JH |
274 | probability_cutoff = PARAM_VALUE (TRACER_MIN_BRANCH_PROBABILITY_FEEDBACK); |
275 | else | |
276 | probability_cutoff = PARAM_VALUE (TRACER_MIN_BRANCH_PROBABILITY); | |
277 | probability_cutoff = REG_BR_PROB_BASE / 100 * probability_cutoff; | |
278 | ||
279 | branch_ratio_cutoff = | |
280 | (REG_BR_PROB_BASE / 100 * PARAM_VALUE (TRACER_MIN_BRANCH_RATIO)); | |
281 | ||
11cd3bed | 282 | FOR_EACH_BB_FN (bb, cfun) |
5c856b23 JH |
283 | { |
284 | int n = count_insns (bb); | |
285 | if (!ignore_bb_p (bb)) | |
dd7bda5e | 286 | blocks[bb->index] = heap.insert (-bb->frequency, bb); |
5c856b23 JH |
287 | |
288 | counts [bb->index] = n; | |
289 | ninsns += n; | |
290 | weighted_insns += n * bb->frequency; | |
291 | } | |
292 | ||
cdb23767 | 293 | if (profile_info && flag_branch_probabilities) |
5c856b23 JH |
294 | cover_insns = PARAM_VALUE (TRACER_DYNAMIC_COVERAGE_FEEDBACK); |
295 | else | |
296 | cover_insns = PARAM_VALUE (TRACER_DYNAMIC_COVERAGE); | |
297 | cover_insns = (weighted_insns * cover_insns + 50) / 100; | |
298 | max_dup_insns = (ninsns * PARAM_VALUE (TRACER_MAX_CODE_GROWTH) + 50) / 100; | |
299 | ||
300 | while (traced_insns < cover_insns && nduplicated < max_dup_insns | |
dd7bda5e | 301 | && !heap.empty ()) |
5c856b23 | 302 | { |
dd7bda5e | 303 | basic_block bb = heap.extract_min (); |
5c856b23 JH |
304 | int n, pos; |
305 | ||
306 | if (!bb) | |
307 | break; | |
308 | ||
309 | blocks[bb->index] = NULL; | |
310 | ||
311 | if (ignore_bb_p (bb)) | |
312 | continue; | |
232abc3f | 313 | gcc_assert (!bb_seen_p (bb)); |
5c856b23 JH |
314 | |
315 | n = find_trace (bb, trace); | |
316 | ||
317 | bb = trace[0]; | |
318 | traced_insns += bb->frequency * counts [bb->index]; | |
319 | if (blocks[bb->index]) | |
320 | { | |
dd7bda5e | 321 | heap.delete_node (blocks[bb->index]); |
5c856b23 JH |
322 | blocks[bb->index] = NULL; |
323 | } | |
324 | ||
325 | for (pos = 1; pos < n; pos++) | |
326 | { | |
327 | basic_block bb2 = trace[pos]; | |
328 | ||
329 | if (blocks[bb2->index]) | |
330 | { | |
dd7bda5e | 331 | heap.delete_node (blocks[bb2->index]); |
5c856b23 JH |
332 | blocks[bb2->index] = NULL; |
333 | } | |
334 | traced_insns += bb2->frequency * counts [bb2->index]; | |
628f6a4e | 335 | if (EDGE_COUNT (bb2->preds) > 1 |
0b9066cf RG |
336 | && can_duplicate_block_p (bb2) |
337 | /* We have the tendency to duplicate the loop header | |
338 | of all do { } while loops. Do not do that - it is | |
339 | not profitable and it might create a loop with multiple | |
340 | entries or at least rotate the loop. */ | |
726338f4 | 341 | && bb2->loop_father->header != bb2) |
5c856b23 | 342 | { |
232abc3f | 343 | nduplicated += counts [bb2->index]; |
8fe17e23 | 344 | basic_block copy = transform_duplicate (bb, bb2); |
5c856b23 JH |
345 | |
346 | /* Reconsider the original copy of block we've duplicated. | |
14b493d6 | 347 | Removing the most common predecessor may make it to be |
5c856b23 | 348 | head. */ |
dd7bda5e | 349 | blocks[bb2->index] = heap.insert (-bb2->frequency, bb2); |
5c856b23 | 350 | |
c263766c RH |
351 | if (dump_file) |
352 | fprintf (dump_file, "Duplicated %i as %i [%i]\n", | |
232abc3f RK |
353 | bb2->index, copy->index, copy->frequency); |
354 | ||
355 | bb2 = copy; | |
07b1bf20 | 356 | changed = true; |
5c856b23 | 357 | } |
232abc3f | 358 | mark_bb_seen (bb2); |
5c856b23 JH |
359 | bb = bb2; |
360 | /* In case the trace became infrequent, stop duplicating. */ | |
361 | if (ignore_bb_p (bb)) | |
362 | break; | |
363 | } | |
c263766c RH |
364 | if (dump_file) |
365 | fprintf (dump_file, " covered now %.1f\n\n", | |
5c856b23 JH |
366 | traced_insns * 100.0 / weighted_insns); |
367 | } | |
c263766c RH |
368 | if (dump_file) |
369 | fprintf (dump_file, "Duplicated %i insns (%i%%)\n", nduplicated, | |
5c856b23 JH |
370 | nduplicated * 100 / ninsns); |
371 | ||
232abc3f RK |
372 | free_original_copy_tables (); |
373 | sbitmap_free (bb_seen); | |
5c856b23 JH |
374 | free (trace); |
375 | free (counts); | |
07b1bf20 RG |
376 | |
377 | return changed; | |
5c856b23 | 378 | } |
ef330312 | 379 | \f |
27a4cd48 DM |
380 | namespace { |
381 | ||
382 | const pass_data pass_data_tracer = | |
ef330312 | 383 | { |
27a4cd48 DM |
384 | GIMPLE_PASS, /* type */ |
385 | "tracer", /* name */ | |
386 | OPTGROUP_NONE, /* optinfo_flags */ | |
27a4cd48 DM |
387 | TV_TRACER, /* tv_id */ |
388 | 0, /* properties_required */ | |
389 | 0, /* properties_provided */ | |
390 | 0, /* properties_destroyed */ | |
391 | 0, /* todo_flags_start */ | |
3bea341f | 392 | TODO_update_ssa, /* todo_flags_finish */ |
ef330312 | 393 | }; |
27a4cd48 DM |
394 | |
395 | class pass_tracer : public gimple_opt_pass | |
396 | { | |
397 | public: | |
c3284718 RS |
398 | pass_tracer (gcc::context *ctxt) |
399 | : gimple_opt_pass (pass_data_tracer, ctxt) | |
27a4cd48 DM |
400 | {} |
401 | ||
402 | /* opt_pass methods: */ | |
1a3d085c TS |
403 | virtual bool gate (function *) |
404 | { | |
405 | return (optimize > 0 && flag_tracer && flag_reorder_blocks); | |
406 | } | |
407 | ||
be55bfe6 | 408 | virtual unsigned int execute (function *); |
27a4cd48 DM |
409 | |
410 | }; // class pass_tracer | |
411 | ||
be55bfe6 TS |
412 | unsigned int |
413 | pass_tracer::execute (function *fun) | |
414 | { | |
415 | bool changed; | |
416 | ||
417 | if (n_basic_blocks_for_fn (fun) <= NUM_FIXED_BLOCKS + 1) | |
418 | return 0; | |
419 | ||
420 | mark_dfs_back_edges (); | |
421 | if (dump_file) | |
422 | brief_dump_cfg (dump_file, dump_flags); | |
423 | ||
424 | /* Trace formation is done on the fly inside tail_duplicate */ | |
425 | changed = tail_duplicate (); | |
426 | if (changed) | |
427 | { | |
428 | free_dominance_info (CDI_DOMINATORS); | |
429 | /* If we changed the CFG schedule loops for fixup by cleanup_cfg. */ | |
726338f4 | 430 | loops_state_set (LOOPS_NEED_FIXUP); |
be55bfe6 TS |
431 | } |
432 | ||
433 | if (dump_file) | |
434 | brief_dump_cfg (dump_file, dump_flags); | |
435 | ||
436 | return changed ? TODO_cleanup_cfg : 0; | |
437 | } | |
27a4cd48 DM |
438 | } // anon namespace |
439 | ||
440 | gimple_opt_pass * | |
441 | make_pass_tracer (gcc::context *ctxt) | |
442 | { | |
443 | return new pass_tracer (ctxt); | |
444 | } |