Mercurial > hg > CbC > CbC_gcc
annotate gcc/cfgloopanal.c @ 88:f214c1d5b862
merge 89
| author | Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp> |
|---|---|
| date | Tue, 20 Dec 2011 18:53:46 +0900 |
| parents | f6334be47118 |
| children | 04ced10e8804 |
| rev | line source |
|---|---|
| 0 | 1 /* Natural loop analysis code for GNU compiler. |
|
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2 Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 |
| 0 | 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 3, 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 COPYING3. If not see | |
| 19 <http://www.gnu.org/licenses/>. */ | |
| 20 | |
| 21 #include "config.h" | |
| 22 #include "system.h" | |
| 23 #include "coretypes.h" | |
| 24 #include "tm.h" | |
| 25 #include "rtl.h" | |
| 26 #include "hard-reg-set.h" | |
| 27 #include "obstack.h" | |
| 28 #include "basic-block.h" | |
| 29 #include "cfgloop.h" | |
| 30 #include "expr.h" | |
| 31 #include "output.h" | |
| 32 #include "graphds.h" | |
| 33 #include "params.h" | |
| 34 | |
|
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35 struct target_cfgloop default_target_cfgloop; |
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36 #if SWITCHABLE_TARGET |
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37 struct target_cfgloop *this_target_cfgloop = &default_target_cfgloop; |
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38 #endif |
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39 |
| 0 | 40 /* Checks whether BB is executed exactly once in each LOOP iteration. */ |
| 41 | |
| 42 bool | |
| 43 just_once_each_iteration_p (const struct loop *loop, const_basic_block bb) | |
| 44 { | |
| 45 /* It must be executed at least once each iteration. */ | |
| 46 if (!dominated_by_p (CDI_DOMINATORS, loop->latch, bb)) | |
| 47 return false; | |
| 48 | |
| 49 /* And just once. */ | |
| 50 if (bb->loop_father != loop) | |
| 51 return false; | |
| 52 | |
| 53 /* But this was not enough. We might have some irreducible loop here. */ | |
| 54 if (bb->flags & BB_IRREDUCIBLE_LOOP) | |
| 55 return false; | |
| 56 | |
| 57 return true; | |
| 58 } | |
| 59 | |
| 60 /* Marks blocks and edges that are part of non-recognized loops; i.e. we | |
| 61 throw away all latch edges and mark blocks inside any remaining cycle. | |
| 62 Everything is a bit complicated due to fact we do not want to do this | |
| 63 for parts of cycles that only "pass" through some loop -- i.e. for | |
| 64 each cycle, we want to mark blocks that belong directly to innermost | |
| 65 loop containing the whole cycle. | |
| 66 | |
| 67 LOOPS is the loop tree. */ | |
| 68 | |
| 69 #define LOOP_REPR(LOOP) ((LOOP)->num + last_basic_block) | |
| 70 #define BB_REPR(BB) ((BB)->index + 1) | |
| 71 | |
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72 bool |
| 0 | 73 mark_irreducible_loops (void) |
| 74 { | |
| 75 basic_block act; | |
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76 struct graph_edge *ge; |
| 0 | 77 edge e; |
| 78 edge_iterator ei; | |
| 79 int src, dest; | |
| 80 unsigned depth; | |
| 81 struct graph *g; | |
| 82 int num = number_of_loops (); | |
| 83 struct loop *cloop; | |
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84 bool irred_loop_found = false; |
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85 int i; |
| 0 | 86 |
| 87 gcc_assert (current_loops != NULL); | |
| 88 | |
| 89 /* Reset the flags. */ | |
| 90 FOR_BB_BETWEEN (act, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb) | |
| 91 { | |
| 92 act->flags &= ~BB_IRREDUCIBLE_LOOP; | |
| 93 FOR_EACH_EDGE (e, ei, act->succs) | |
| 94 e->flags &= ~EDGE_IRREDUCIBLE_LOOP; | |
| 95 } | |
| 96 | |
| 97 /* Create the edge lists. */ | |
| 98 g = new_graph (last_basic_block + num); | |
| 99 | |
| 100 FOR_BB_BETWEEN (act, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb) | |
| 101 FOR_EACH_EDGE (e, ei, act->succs) | |
| 102 { | |
| 103 /* Ignore edges to exit. */ | |
| 104 if (e->dest == EXIT_BLOCK_PTR) | |
| 105 continue; | |
| 106 | |
| 107 src = BB_REPR (act); | |
| 108 dest = BB_REPR (e->dest); | |
| 109 | |
| 110 /* Ignore latch edges. */ | |
| 111 if (e->dest->loop_father->header == e->dest | |
| 112 && e->dest->loop_father->latch == act) | |
| 113 continue; | |
| 114 | |
| 115 /* Edges inside a single loop should be left where they are. Edges | |
| 116 to subloop headers should lead to representative of the subloop, | |
| 117 but from the same place. | |
| 118 | |
| 119 Edges exiting loops should lead from representative | |
| 120 of the son of nearest common ancestor of the loops in that | |
| 121 act lays. */ | |
| 122 | |
| 123 if (e->dest->loop_father->header == e->dest) | |
| 124 dest = LOOP_REPR (e->dest->loop_father); | |
| 125 | |
| 126 if (!flow_bb_inside_loop_p (act->loop_father, e->dest)) | |
| 127 { | |
| 128 depth = 1 + loop_depth (find_common_loop (act->loop_father, | |
| 129 e->dest->loop_father)); | |
| 130 if (depth == loop_depth (act->loop_father)) | |
| 131 cloop = act->loop_father; | |
| 132 else | |
| 133 cloop = VEC_index (loop_p, act->loop_father->superloops, depth); | |
| 134 | |
| 135 src = LOOP_REPR (cloop); | |
| 136 } | |
| 137 | |
| 138 add_edge (g, src, dest)->data = e; | |
| 139 } | |
| 140 | |
| 141 /* Find the strongly connected components. */ | |
| 142 graphds_scc (g, NULL); | |
| 143 | |
| 144 /* Mark the irreducible loops. */ | |
|
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145 for (i = 0; i < g->n_vertices; i++) |
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146 for (ge = g->vertices[i].succ; ge; ge = ge->succ_next) |
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147 { |
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148 edge real = (edge) ge->data; |
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149 /* edge E in graph G is irreducible if it connects two vertices in the |
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150 same scc. */ |
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151 |
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152 /* All edges should lead from a component with higher number to the |
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153 one with lower one. */ |
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154 gcc_assert (g->vertices[ge->src].component >= g->vertices[ge->dest].component); |
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155 |
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156 if (g->vertices[ge->src].component != g->vertices[ge->dest].component) |
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157 continue; |
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158 |
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159 real->flags |= EDGE_IRREDUCIBLE_LOOP; |
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160 irred_loop_found = true; |
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161 if (flow_bb_inside_loop_p (real->src->loop_father, real->dest)) |
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162 real->src->flags |= BB_IRREDUCIBLE_LOOP; |
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163 } |
| 0 | 164 |
| 165 free_graph (g); | |
| 166 | |
| 167 loops_state_set (LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS); | |
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168 return irred_loop_found; |
| 0 | 169 } |
| 170 | |
| 171 /* Counts number of insns inside LOOP. */ | |
| 172 int | |
| 173 num_loop_insns (const struct loop *loop) | |
| 174 { | |
| 175 basic_block *bbs, bb; | |
| 176 unsigned i, ninsns = 0; | |
| 177 rtx insn; | |
| 178 | |
| 179 bbs = get_loop_body (loop); | |
| 180 for (i = 0; i < loop->num_nodes; i++) | |
| 181 { | |
| 182 bb = bbs[i]; | |
|
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183 FOR_BB_INSNS (bb, insn) |
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184 if (NONDEBUG_INSN_P (insn)) |
| 0 | 185 ninsns++; |
| 186 } | |
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187 free (bbs); |
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188 |
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189 if (!ninsns) |
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190 ninsns = 1; /* To avoid division by zero. */ |
| 0 | 191 |
| 192 return ninsns; | |
| 193 } | |
| 194 | |
| 195 /* Counts number of insns executed on average per iteration LOOP. */ | |
| 196 int | |
| 197 average_num_loop_insns (const struct loop *loop) | |
| 198 { | |
| 199 basic_block *bbs, bb; | |
| 200 unsigned i, binsns, ninsns, ratio; | |
| 201 rtx insn; | |
| 202 | |
| 203 ninsns = 0; | |
| 204 bbs = get_loop_body (loop); | |
| 205 for (i = 0; i < loop->num_nodes; i++) | |
| 206 { | |
| 207 bb = bbs[i]; | |
| 208 | |
|
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209 binsns = 0; |
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210 FOR_BB_INSNS (bb, insn) |
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211 if (NONDEBUG_INSN_P (insn)) |
| 0 | 212 binsns++; |
| 213 | |
| 214 ratio = loop->header->frequency == 0 | |
| 215 ? BB_FREQ_MAX | |
| 216 : (bb->frequency * BB_FREQ_MAX) / loop->header->frequency; | |
| 217 ninsns += binsns * ratio; | |
| 218 } | |
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219 free (bbs); |
| 0 | 220 |
| 221 ninsns /= BB_FREQ_MAX; | |
| 222 if (!ninsns) | |
| 223 ninsns = 1; /* To avoid division by zero. */ | |
| 224 | |
| 225 return ninsns; | |
| 226 } | |
| 227 | |
| 228 /* Returns expected number of iterations of LOOP, according to | |
| 229 measured or guessed profile. No bounding is done on the | |
| 230 value. */ | |
| 231 | |
| 232 gcov_type | |
| 233 expected_loop_iterations_unbounded (const struct loop *loop) | |
| 234 { | |
| 235 edge e; | |
| 236 edge_iterator ei; | |
| 237 | |
| 238 if (loop->latch->count || loop->header->count) | |
| 239 { | |
| 240 gcov_type count_in, count_latch, expected; | |
| 241 | |
| 242 count_in = 0; | |
| 243 count_latch = 0; | |
| 244 | |
| 245 FOR_EACH_EDGE (e, ei, loop->header->preds) | |
| 246 if (e->src == loop->latch) | |
| 247 count_latch = e->count; | |
| 248 else | |
| 249 count_in += e->count; | |
| 250 | |
| 251 if (count_in == 0) | |
| 252 expected = count_latch * 2; | |
| 253 else | |
| 254 expected = (count_latch + count_in - 1) / count_in; | |
| 255 | |
| 256 return expected; | |
| 257 } | |
| 258 else | |
| 259 { | |
| 260 int freq_in, freq_latch; | |
| 261 | |
| 262 freq_in = 0; | |
| 263 freq_latch = 0; | |
| 264 | |
| 265 FOR_EACH_EDGE (e, ei, loop->header->preds) | |
| 266 if (e->src == loop->latch) | |
| 267 freq_latch = EDGE_FREQUENCY (e); | |
| 268 else | |
| 269 freq_in += EDGE_FREQUENCY (e); | |
| 270 | |
| 271 if (freq_in == 0) | |
| 272 return freq_latch * 2; | |
| 273 | |
| 274 return (freq_latch + freq_in - 1) / freq_in; | |
| 275 } | |
| 276 } | |
| 277 | |
| 278 /* Returns expected number of LOOP iterations. The returned value is bounded | |
| 279 by REG_BR_PROB_BASE. */ | |
| 280 | |
| 281 unsigned | |
| 282 expected_loop_iterations (const struct loop *loop) | |
| 283 { | |
| 284 gcov_type expected = expected_loop_iterations_unbounded (loop); | |
| 285 return (expected > REG_BR_PROB_BASE ? REG_BR_PROB_BASE : expected); | |
| 286 } | |
| 287 | |
| 288 /* Returns the maximum level of nesting of subloops of LOOP. */ | |
| 289 | |
| 290 unsigned | |
| 291 get_loop_level (const struct loop *loop) | |
| 292 { | |
| 293 const struct loop *ploop; | |
| 294 unsigned mx = 0, l; | |
| 295 | |
| 296 for (ploop = loop->inner; ploop; ploop = ploop->next) | |
| 297 { | |
| 298 l = get_loop_level (ploop); | |
| 299 if (l >= mx) | |
| 300 mx = l + 1; | |
| 301 } | |
| 302 return mx; | |
| 303 } | |
| 304 | |
| 305 /* Returns estimate on cost of computing SEQ. */ | |
| 306 | |
| 307 static unsigned | |
| 308 seq_cost (const_rtx seq, bool speed) | |
| 309 { | |
| 310 unsigned cost = 0; | |
| 311 rtx set; | |
| 312 | |
| 313 for (; seq; seq = NEXT_INSN (seq)) | |
| 314 { | |
| 315 set = single_set (seq); | |
| 316 if (set) | |
| 317 cost += rtx_cost (set, SET, speed); | |
| 318 else | |
| 319 cost++; | |
| 320 } | |
| 321 | |
| 322 return cost; | |
| 323 } | |
| 324 | |
| 325 /* Initialize the constants for computing set costs. */ | |
| 326 | |
| 327 void | |
| 328 init_set_costs (void) | |
| 329 { | |
| 330 int speed; | |
| 331 rtx seq; | |
| 332 rtx reg1 = gen_raw_REG (SImode, FIRST_PSEUDO_REGISTER); | |
| 333 rtx reg2 = gen_raw_REG (SImode, FIRST_PSEUDO_REGISTER + 1); | |
| 334 rtx addr = gen_raw_REG (Pmode, FIRST_PSEUDO_REGISTER + 2); | |
| 335 rtx mem = validize_mem (gen_rtx_MEM (SImode, addr)); | |
| 336 unsigned i; | |
| 337 | |
| 338 target_avail_regs = 0; | |
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339 target_clobbered_regs = 0; |
| 0 | 340 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) |
| 341 if (TEST_HARD_REG_BIT (reg_class_contents[GENERAL_REGS], i) | |
| 342 && !fixed_regs[i]) | |
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343 { |
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344 target_avail_regs++; |
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345 if (call_used_regs[i]) |
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346 target_clobbered_regs++; |
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347 } |
| 0 | 348 |
| 349 target_res_regs = 3; | |
| 350 | |
| 351 for (speed = 0; speed < 2; speed++) | |
| 352 { | |
| 353 crtl->maybe_hot_insn_p = speed; | |
| 354 /* Set up the costs for using extra registers: | |
| 355 | |
| 356 1) If not many free registers remain, we should prefer having an | |
| 357 additional move to decreasing the number of available registers. | |
| 358 (TARGET_REG_COST). | |
| 359 2) If no registers are available, we need to spill, which may require | |
| 360 storing the old value to memory and loading it back | |
| 361 (TARGET_SPILL_COST). */ | |
| 362 | |
| 363 start_sequence (); | |
| 364 emit_move_insn (reg1, reg2); | |
| 365 seq = get_insns (); | |
| 366 end_sequence (); | |
| 367 target_reg_cost [speed] = seq_cost (seq, speed); | |
| 368 | |
| 369 start_sequence (); | |
| 370 emit_move_insn (mem, reg1); | |
| 371 emit_move_insn (reg2, mem); | |
| 372 seq = get_insns (); | |
| 373 end_sequence (); | |
| 374 target_spill_cost [speed] = seq_cost (seq, speed); | |
| 375 } | |
| 376 default_rtl_profile (); | |
| 377 } | |
| 378 | |
| 379 /* Estimates cost of increased register pressure caused by making N_NEW new | |
| 380 registers live around the loop. N_OLD is the number of registers live | |
|
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381 around the loop. If CALL_P is true, also take into account that |
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382 call-used registers may be clobbered in the loop body, reducing the |
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383 number of available registers before we spill. */ |
| 0 | 384 |
| 385 unsigned | |
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386 estimate_reg_pressure_cost (unsigned n_new, unsigned n_old, bool speed, |
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387 bool call_p) |
| 0 | 388 { |
| 389 unsigned cost; | |
| 390 unsigned regs_needed = n_new + n_old; | |
|
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391 unsigned available_regs = target_avail_regs; |
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392 |
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393 /* If there is a call in the loop body, the call-clobbered registers |
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394 are not available for loop invariants. */ |
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395 if (call_p) |
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396 available_regs = available_regs - target_clobbered_regs; |
| 0 | 397 |
| 398 /* If we have enough registers, we should use them and not restrict | |
| 399 the transformations unnecessarily. */ | |
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400 if (regs_needed + target_res_regs <= available_regs) |
| 0 | 401 return 0; |
| 402 | |
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403 if (regs_needed <= available_regs) |
| 0 | 404 /* If we are close to running out of registers, try to preserve |
| 405 them. */ | |
| 406 cost = target_reg_cost [speed] * n_new; | |
| 407 else | |
| 408 /* If we run out of registers, it is very expensive to add another | |
| 409 one. */ | |
| 410 cost = target_spill_cost [speed] * n_new; | |
| 411 | |
| 412 if (optimize && (flag_ira_region == IRA_REGION_ALL | |
| 413 || flag_ira_region == IRA_REGION_MIXED) | |
| 414 && number_of_loops () <= (unsigned) IRA_MAX_LOOPS_NUM) | |
| 415 /* IRA regional allocation deals with high register pressure | |
| 416 better. So decrease the cost (to do more accurate the cost | |
| 417 calculation for IRA, we need to know how many registers lives | |
| 418 through the loop transparently). */ | |
| 419 cost /= 2; | |
| 420 | |
| 421 return cost; | |
| 422 } | |
| 423 | |
| 424 /* Sets EDGE_LOOP_EXIT flag for all loop exits. */ | |
| 425 | |
| 426 void | |
| 427 mark_loop_exit_edges (void) | |
| 428 { | |
| 429 basic_block bb; | |
| 430 edge e; | |
| 431 | |
| 432 if (number_of_loops () <= 1) | |
| 433 return; | |
| 434 | |
| 435 FOR_EACH_BB (bb) | |
| 436 { | |
| 437 edge_iterator ei; | |
| 438 | |
| 439 FOR_EACH_EDGE (e, ei, bb->succs) | |
| 440 { | |
| 441 if (loop_outer (bb->loop_father) | |
| 442 && loop_exit_edge_p (bb->loop_father, e)) | |
| 443 e->flags |= EDGE_LOOP_EXIT; | |
| 444 else | |
| 445 e->flags &= ~EDGE_LOOP_EXIT; | |
| 446 } | |
| 447 } | |
| 448 } | |
| 449 |