Mercurial > hg > CbC > CbC_gcc
annotate gcc/cfgloopanal.c @ 137:d22083d7f10b
merge
author | Shinji KONO <kono@ie.u-ryukyu.ac.jp> |
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date | Thu, 08 Nov 2018 14:16:42 +0900 |
parents | 84e7813d76e9 |
children | 1830386684a0 |
rev | line source |
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0 | 1 /* Natural loop analysis code for GNU compiler. |
131 | 2 Copyright (C) 2002-2018 Free Software Foundation, Inc. |
0 | 3 |
4 This file is part of GCC. | |
5 | |
6 GCC is free software; you can redistribute it and/or modify it under | |
7 the terms of the GNU General Public License as published by the Free | |
8 Software Foundation; either version 3, or (at your option) any later | |
9 version. | |
10 | |
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
14 for more details. | |
15 | |
16 You should have received a copy of the GNU General Public License | |
17 along with GCC; see the file COPYING3. If not see | |
18 <http://www.gnu.org/licenses/>. */ | |
19 | |
20 #include "config.h" | |
21 #include "system.h" | |
22 #include "coretypes.h" | |
111 | 23 #include "backend.h" |
0 | 24 #include "rtl.h" |
111 | 25 #include "tree.h" |
26 #include "predict.h" | |
27 #include "memmodel.h" | |
28 #include "emit-rtl.h" | |
0 | 29 #include "cfgloop.h" |
111 | 30 #include "explow.h" |
0 | 31 #include "expr.h" |
32 #include "graphds.h" | |
33 #include "params.h" | |
131 | 34 #include "sreal.h" |
0 | 35 |
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36 struct target_cfgloop default_target_cfgloop; |
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37 #if SWITCHABLE_TARGET |
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38 struct target_cfgloop *this_target_cfgloop = &default_target_cfgloop; |
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39 #endif |
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40 |
0 | 41 /* Checks whether BB is executed exactly once in each LOOP iteration. */ |
42 | |
43 bool | |
44 just_once_each_iteration_p (const struct loop *loop, const_basic_block bb) | |
45 { | |
46 /* It must be executed at least once each iteration. */ | |
47 if (!dominated_by_p (CDI_DOMINATORS, loop->latch, bb)) | |
48 return false; | |
49 | |
50 /* And just once. */ | |
51 if (bb->loop_father != loop) | |
52 return false; | |
53 | |
54 /* But this was not enough. We might have some irreducible loop here. */ | |
55 if (bb->flags & BB_IRREDUCIBLE_LOOP) | |
56 return false; | |
57 | |
58 return true; | |
59 } | |
60 | |
61 /* Marks blocks and edges that are part of non-recognized loops; i.e. we | |
62 throw away all latch edges and mark blocks inside any remaining cycle. | |
63 Everything is a bit complicated due to fact we do not want to do this | |
64 for parts of cycles that only "pass" through some loop -- i.e. for | |
65 each cycle, we want to mark blocks that belong directly to innermost | |
66 loop containing the whole cycle. | |
67 | |
68 LOOPS is the loop tree. */ | |
69 | |
111 | 70 #define LOOP_REPR(LOOP) ((LOOP)->num + last_basic_block_for_fn (cfun)) |
0 | 71 #define BB_REPR(BB) ((BB)->index + 1) |
72 | |
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73 bool |
0 | 74 mark_irreducible_loops (void) |
75 { | |
76 basic_block act; | |
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77 struct graph_edge *ge; |
0 | 78 edge e; |
79 edge_iterator ei; | |
80 int src, dest; | |
81 unsigned depth; | |
82 struct graph *g; | |
111 | 83 int num = number_of_loops (cfun); |
0 | 84 struct loop *cloop; |
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85 bool irred_loop_found = false; |
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86 int i; |
0 | 87 |
88 gcc_assert (current_loops != NULL); | |
89 | |
90 /* Reset the flags. */ | |
111 | 91 FOR_BB_BETWEEN (act, ENTRY_BLOCK_PTR_FOR_FN (cfun), |
92 EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb) | |
0 | 93 { |
94 act->flags &= ~BB_IRREDUCIBLE_LOOP; | |
95 FOR_EACH_EDGE (e, ei, act->succs) | |
96 e->flags &= ~EDGE_IRREDUCIBLE_LOOP; | |
97 } | |
98 | |
99 /* Create the edge lists. */ | |
111 | 100 g = new_graph (last_basic_block_for_fn (cfun) + num); |
0 | 101 |
111 | 102 FOR_BB_BETWEEN (act, ENTRY_BLOCK_PTR_FOR_FN (cfun), |
103 EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb) | |
0 | 104 FOR_EACH_EDGE (e, ei, act->succs) |
105 { | |
106 /* Ignore edges to exit. */ | |
111 | 107 if (e->dest == EXIT_BLOCK_PTR_FOR_FN (cfun)) |
0 | 108 continue; |
109 | |
110 src = BB_REPR (act); | |
111 dest = BB_REPR (e->dest); | |
112 | |
113 /* Ignore latch edges. */ | |
114 if (e->dest->loop_father->header == e->dest | |
115 && e->dest->loop_father->latch == act) | |
116 continue; | |
117 | |
118 /* Edges inside a single loop should be left where they are. Edges | |
119 to subloop headers should lead to representative of the subloop, | |
120 but from the same place. | |
121 | |
122 Edges exiting loops should lead from representative | |
123 of the son of nearest common ancestor of the loops in that | |
124 act lays. */ | |
125 | |
126 if (e->dest->loop_father->header == e->dest) | |
127 dest = LOOP_REPR (e->dest->loop_father); | |
128 | |
129 if (!flow_bb_inside_loop_p (act->loop_father, e->dest)) | |
130 { | |
131 depth = 1 + loop_depth (find_common_loop (act->loop_father, | |
132 e->dest->loop_father)); | |
133 if (depth == loop_depth (act->loop_father)) | |
134 cloop = act->loop_father; | |
135 else | |
111 | 136 cloop = (*act->loop_father->superloops)[depth]; |
0 | 137 |
138 src = LOOP_REPR (cloop); | |
139 } | |
140 | |
141 add_edge (g, src, dest)->data = e; | |
142 } | |
143 | |
144 /* Find the strongly connected components. */ | |
145 graphds_scc (g, NULL); | |
146 | |
147 /* Mark the irreducible loops. */ | |
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148 for (i = 0; i < g->n_vertices; i++) |
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149 for (ge = g->vertices[i].succ; ge; ge = ge->succ_next) |
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150 { |
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151 edge real = (edge) ge->data; |
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152 /* edge E in graph G is irreducible if it connects two vertices in the |
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153 same scc. */ |
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154 |
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155 /* All edges should lead from a component with higher number to the |
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156 one with lower one. */ |
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157 gcc_assert (g->vertices[ge->src].component >= g->vertices[ge->dest].component); |
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158 |
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159 if (g->vertices[ge->src].component != g->vertices[ge->dest].component) |
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160 continue; |
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161 |
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162 real->flags |= EDGE_IRREDUCIBLE_LOOP; |
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163 irred_loop_found = true; |
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164 if (flow_bb_inside_loop_p (real->src->loop_father, real->dest)) |
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165 real->src->flags |= BB_IRREDUCIBLE_LOOP; |
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166 } |
0 | 167 |
168 free_graph (g); | |
169 | |
170 loops_state_set (LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS); | |
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171 return irred_loop_found; |
0 | 172 } |
173 | |
174 /* Counts number of insns inside LOOP. */ | |
175 int | |
176 num_loop_insns (const struct loop *loop) | |
177 { | |
178 basic_block *bbs, bb; | |
179 unsigned i, ninsns = 0; | |
111 | 180 rtx_insn *insn; |
0 | 181 |
182 bbs = get_loop_body (loop); | |
183 for (i = 0; i < loop->num_nodes; i++) | |
184 { | |
185 bb = bbs[i]; | |
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186 FOR_BB_INSNS (bb, insn) |
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187 if (NONDEBUG_INSN_P (insn)) |
0 | 188 ninsns++; |
189 } | |
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190 free (bbs); |
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191 |
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192 if (!ninsns) |
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193 ninsns = 1; /* To avoid division by zero. */ |
0 | 194 |
195 return ninsns; | |
196 } | |
197 | |
198 /* Counts number of insns executed on average per iteration LOOP. */ | |
199 int | |
200 average_num_loop_insns (const struct loop *loop) | |
201 { | |
202 basic_block *bbs, bb; | |
131 | 203 unsigned i, binsns; |
204 sreal ninsns; | |
111 | 205 rtx_insn *insn; |
0 | 206 |
207 ninsns = 0; | |
208 bbs = get_loop_body (loop); | |
209 for (i = 0; i < loop->num_nodes; i++) | |
210 { | |
211 bb = bbs[i]; | |
212 | |
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213 binsns = 0; |
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214 FOR_BB_INSNS (bb, insn) |
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215 if (NONDEBUG_INSN_P (insn)) |
0 | 216 binsns++; |
217 | |
131 | 218 ninsns += (sreal)binsns * bb->count.to_sreal_scale (loop->header->count); |
219 /* Avoid overflows. */ | |
220 if (ninsns > 1000000) | |
221 return 100000; | |
0 | 222 } |
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223 free (bbs); |
0 | 224 |
131 | 225 int64_t ret = ninsns.to_int (); |
226 if (!ret) | |
227 ret = 1; /* To avoid division by zero. */ | |
0 | 228 |
131 | 229 return ret; |
0 | 230 } |
231 | |
232 /* Returns expected number of iterations of LOOP, according to | |
131 | 233 measured or guessed profile. |
234 | |
235 This functions attempts to return "sane" value even if profile | |
236 information is not good enough to derive osmething. | |
237 If BY_PROFILE_ONLY is set, this logic is bypassed and function | |
238 return -1 in those scenarios. */ | |
0 | 239 |
240 gcov_type | |
111 | 241 expected_loop_iterations_unbounded (const struct loop *loop, |
131 | 242 bool *read_profile_p, |
243 bool by_profile_only) | |
0 | 244 { |
245 edge e; | |
246 edge_iterator ei; | |
111 | 247 gcov_type expected = -1; |
248 | |
249 if (read_profile_p) | |
250 *read_profile_p = false; | |
0 | 251 |
111 | 252 /* If we have no profile at all, use AVG_LOOP_NITER. */ |
253 if (profile_status_for_fn (cfun) == PROFILE_ABSENT) | |
131 | 254 { |
255 if (by_profile_only) | |
256 return -1; | |
257 expected = PARAM_VALUE (PARAM_AVG_LOOP_NITER); | |
258 } | |
259 else if (loop->latch && (loop->latch->count.initialized_p () | |
260 || loop->header->count.initialized_p ())) | |
0 | 261 { |
111 | 262 profile_count count_in = profile_count::zero (), |
263 count_latch = profile_count::zero (); | |
0 | 264 |
265 FOR_EACH_EDGE (e, ei, loop->header->preds) | |
266 if (e->src == loop->latch) | |
111 | 267 count_latch = e->count (); |
0 | 268 else |
111 | 269 count_in += e->count (); |
0 | 270 |
111 | 271 if (!count_latch.initialized_p ()) |
131 | 272 { |
273 if (by_profile_only) | |
274 return -1; | |
275 expected = PARAM_VALUE (PARAM_AVG_LOOP_NITER); | |
276 } | |
277 else if (!count_in.nonzero_p ()) | |
278 { | |
279 if (by_profile_only) | |
280 return -1; | |
281 expected = count_latch.to_gcov_type () * 2; | |
282 } | |
0 | 283 else |
111 | 284 { |
285 expected = (count_latch.to_gcov_type () + count_in.to_gcov_type () | |
286 - 1) / count_in.to_gcov_type (); | |
131 | 287 if (read_profile_p |
288 && count_latch.reliable_p () && count_in.reliable_p ()) | |
111 | 289 *read_profile_p = true; |
290 } | |
0 | 291 } |
131 | 292 else |
0 | 293 { |
131 | 294 if (by_profile_only) |
295 return -1; | |
296 expected = PARAM_VALUE (PARAM_AVG_LOOP_NITER); | |
111 | 297 } |
0 | 298 |
131 | 299 if (!by_profile_only) |
300 { | |
301 HOST_WIDE_INT max = get_max_loop_iterations_int (loop); | |
302 if (max != -1 && max < expected) | |
303 return max; | |
304 } | |
305 | |
111 | 306 return expected; |
0 | 307 } |
308 | |
309 /* Returns expected number of LOOP iterations. The returned value is bounded | |
310 by REG_BR_PROB_BASE. */ | |
311 | |
312 unsigned | |
111 | 313 expected_loop_iterations (struct loop *loop) |
0 | 314 { |
315 gcov_type expected = expected_loop_iterations_unbounded (loop); | |
316 return (expected > REG_BR_PROB_BASE ? REG_BR_PROB_BASE : expected); | |
317 } | |
318 | |
319 /* Returns the maximum level of nesting of subloops of LOOP. */ | |
320 | |
321 unsigned | |
322 get_loop_level (const struct loop *loop) | |
323 { | |
324 const struct loop *ploop; | |
325 unsigned mx = 0, l; | |
326 | |
327 for (ploop = loop->inner; ploop; ploop = ploop->next) | |
328 { | |
329 l = get_loop_level (ploop); | |
330 if (l >= mx) | |
331 mx = l + 1; | |
332 } | |
333 return mx; | |
334 } | |
335 | |
336 /* Initialize the constants for computing set costs. */ | |
337 | |
338 void | |
339 init_set_costs (void) | |
340 { | |
341 int speed; | |
111 | 342 rtx_insn *seq; |
343 rtx reg1 = gen_raw_REG (SImode, LAST_VIRTUAL_REGISTER + 1); | |
344 rtx reg2 = gen_raw_REG (SImode, LAST_VIRTUAL_REGISTER + 2); | |
345 rtx addr = gen_raw_REG (Pmode, LAST_VIRTUAL_REGISTER + 3); | |
0 | 346 rtx mem = validize_mem (gen_rtx_MEM (SImode, addr)); |
347 unsigned i; | |
348 | |
349 target_avail_regs = 0; | |
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350 target_clobbered_regs = 0; |
0 | 351 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) |
352 if (TEST_HARD_REG_BIT (reg_class_contents[GENERAL_REGS], i) | |
353 && !fixed_regs[i]) | |
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354 { |
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355 target_avail_regs++; |
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356 if (call_used_regs[i]) |
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357 target_clobbered_regs++; |
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358 } |
0 | 359 |
360 target_res_regs = 3; | |
361 | |
362 for (speed = 0; speed < 2; speed++) | |
363 { | |
364 crtl->maybe_hot_insn_p = speed; | |
365 /* Set up the costs for using extra registers: | |
366 | |
367 1) If not many free registers remain, we should prefer having an | |
368 additional move to decreasing the number of available registers. | |
369 (TARGET_REG_COST). | |
370 2) If no registers are available, we need to spill, which may require | |
371 storing the old value to memory and loading it back | |
372 (TARGET_SPILL_COST). */ | |
373 | |
374 start_sequence (); | |
375 emit_move_insn (reg1, reg2); | |
376 seq = get_insns (); | |
377 end_sequence (); | |
378 target_reg_cost [speed] = seq_cost (seq, speed); | |
379 | |
380 start_sequence (); | |
381 emit_move_insn (mem, reg1); | |
382 emit_move_insn (reg2, mem); | |
383 seq = get_insns (); | |
384 end_sequence (); | |
385 target_spill_cost [speed] = seq_cost (seq, speed); | |
386 } | |
387 default_rtl_profile (); | |
388 } | |
389 | |
390 /* Estimates cost of increased register pressure caused by making N_NEW new | |
391 registers live around the loop. N_OLD is the number of registers live | |
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392 around the loop. If CALL_P is true, also take into account that |
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393 call-used registers may be clobbered in the loop body, reducing the |
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394 number of available registers before we spill. */ |
0 | 395 |
396 unsigned | |
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397 estimate_reg_pressure_cost (unsigned n_new, unsigned n_old, bool speed, |
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398 bool call_p) |
0 | 399 { |
400 unsigned cost; | |
401 unsigned regs_needed = n_new + n_old; | |
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402 unsigned available_regs = target_avail_regs; |
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403 |
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404 /* If there is a call in the loop body, the call-clobbered registers |
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405 are not available for loop invariants. */ |
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406 if (call_p) |
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407 available_regs = available_regs - target_clobbered_regs; |
0 | 408 |
409 /* If we have enough registers, we should use them and not restrict | |
410 the transformations unnecessarily. */ | |
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411 if (regs_needed + target_res_regs <= available_regs) |
0 | 412 return 0; |
413 | |
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414 if (regs_needed <= available_regs) |
0 | 415 /* If we are close to running out of registers, try to preserve |
416 them. */ | |
417 cost = target_reg_cost [speed] * n_new; | |
418 else | |
419 /* If we run out of registers, it is very expensive to add another | |
420 one. */ | |
421 cost = target_spill_cost [speed] * n_new; | |
422 | |
423 if (optimize && (flag_ira_region == IRA_REGION_ALL | |
424 || flag_ira_region == IRA_REGION_MIXED) | |
111 | 425 && number_of_loops (cfun) <= (unsigned) IRA_MAX_LOOPS_NUM) |
0 | 426 /* IRA regional allocation deals with high register pressure |
427 better. So decrease the cost (to do more accurate the cost | |
428 calculation for IRA, we need to know how many registers lives | |
429 through the loop transparently). */ | |
430 cost /= 2; | |
431 | |
432 return cost; | |
433 } | |
434 | |
435 /* Sets EDGE_LOOP_EXIT flag for all loop exits. */ | |
436 | |
437 void | |
438 mark_loop_exit_edges (void) | |
439 { | |
440 basic_block bb; | |
441 edge e; | |
442 | |
111 | 443 if (number_of_loops (cfun) <= 1) |
0 | 444 return; |
445 | |
111 | 446 FOR_EACH_BB_FN (bb, cfun) |
0 | 447 { |
448 edge_iterator ei; | |
449 | |
450 FOR_EACH_EDGE (e, ei, bb->succs) | |
451 { | |
452 if (loop_outer (bb->loop_father) | |
453 && loop_exit_edge_p (bb->loop_father, e)) | |
454 e->flags |= EDGE_LOOP_EXIT; | |
455 else | |
456 e->flags &= ~EDGE_LOOP_EXIT; | |
457 } | |
458 } | |
459 } | |
460 | |
111 | 461 /* Return exit edge if loop has only one exit that is likely |
462 to be executed on runtime (i.e. it is not EH or leading | |
463 to noreturn call. */ | |
464 | |
465 edge | |
466 single_likely_exit (struct loop *loop) | |
467 { | |
468 edge found = single_exit (loop); | |
469 vec<edge> exits; | |
470 unsigned i; | |
471 edge ex; | |
472 | |
473 if (found) | |
474 return found; | |
475 exits = get_loop_exit_edges (loop); | |
476 FOR_EACH_VEC_ELT (exits, i, ex) | |
477 { | |
478 if (probably_never_executed_edge_p (cfun, ex) | |
479 /* We want to rule out paths to noreturns but not low probabilities | |
480 resulting from adjustments or combining. | |
481 FIXME: once we have better quality tracking, make this more | |
482 robust. */ | |
483 || ex->probability <= profile_probability::very_unlikely ()) | |
484 continue; | |
485 if (!found) | |
486 found = ex; | |
487 else | |
488 { | |
489 exits.release (); | |
490 return NULL; | |
491 } | |
492 } | |
493 exits.release (); | |
494 return found; | |
495 } | |
496 | |
497 | |
498 /* Gets basic blocks of a LOOP. Header is the 0-th block, rest is in dfs | |
499 order against direction of edges from latch. Specially, if | |
500 header != latch, latch is the 1-st block. */ | |
501 | |
502 vec<basic_block> | |
503 get_loop_hot_path (const struct loop *loop) | |
504 { | |
505 basic_block bb = loop->header; | |
506 vec<basic_block> path = vNULL; | |
507 bitmap visited = BITMAP_ALLOC (NULL); | |
508 | |
509 while (true) | |
510 { | |
511 edge_iterator ei; | |
512 edge e; | |
513 edge best = NULL; | |
514 | |
515 path.safe_push (bb); | |
516 bitmap_set_bit (visited, bb->index); | |
517 FOR_EACH_EDGE (e, ei, bb->succs) | |
518 if ((!best || e->probability > best->probability) | |
519 && !loop_exit_edge_p (loop, e) | |
520 && !bitmap_bit_p (visited, e->dest->index)) | |
521 best = e; | |
522 if (!best || best->dest == loop->header) | |
523 break; | |
524 bb = best->dest; | |
525 } | |
526 BITMAP_FREE (visited); | |
527 return path; | |
528 } |