Mercurial > hg > CbC > CbC_gcc
annotate gcc/cfgloopanal.c @ 158:494b0b89df80 default tip
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| author | Shinji KONO <kono@ie.u-ryukyu.ac.jp> |
|---|---|
| date | Mon, 25 May 2020 18:13:55 +0900 |
| parents | 1830386684a0 |
| children |
| rev | line source |
|---|---|
| 0 | 1 /* Natural loop analysis code for GNU compiler. |
| 145 | 2 Copyright (C) 2002-2020 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" | |
| 131 | 33 #include "sreal.h" |
| 145 | 34 #include "regs.h" |
| 35 #include "function-abi.h" | |
| 0 | 36 |
|
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37 struct target_cfgloop default_target_cfgloop; |
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38 #if SWITCHABLE_TARGET |
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39 struct target_cfgloop *this_target_cfgloop = &default_target_cfgloop; |
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40 #endif |
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41 |
| 0 | 42 /* Checks whether BB is executed exactly once in each LOOP iteration. */ |
| 43 | |
| 44 bool | |
| 145 | 45 just_once_each_iteration_p (const class loop *loop, const_basic_block bb) |
| 0 | 46 { |
| 47 /* It must be executed at least once each iteration. */ | |
| 48 if (!dominated_by_p (CDI_DOMINATORS, loop->latch, bb)) | |
| 49 return false; | |
| 50 | |
| 51 /* And just once. */ | |
| 52 if (bb->loop_father != loop) | |
| 53 return false; | |
| 54 | |
| 55 /* But this was not enough. We might have some irreducible loop here. */ | |
| 56 if (bb->flags & BB_IRREDUCIBLE_LOOP) | |
| 57 return false; | |
| 58 | |
| 59 return true; | |
| 60 } | |
| 61 | |
| 62 /* Marks blocks and edges that are part of non-recognized loops; i.e. we | |
| 63 throw away all latch edges and mark blocks inside any remaining cycle. | |
| 64 Everything is a bit complicated due to fact we do not want to do this | |
| 65 for parts of cycles that only "pass" through some loop -- i.e. for | |
| 66 each cycle, we want to mark blocks that belong directly to innermost | |
| 67 loop containing the whole cycle. | |
| 68 | |
| 69 LOOPS is the loop tree. */ | |
| 70 | |
| 111 | 71 #define LOOP_REPR(LOOP) ((LOOP)->num + last_basic_block_for_fn (cfun)) |
| 0 | 72 #define BB_REPR(BB) ((BB)->index + 1) |
| 73 | |
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74 bool |
| 0 | 75 mark_irreducible_loops (void) |
| 76 { | |
| 77 basic_block act; | |
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78 struct graph_edge *ge; |
| 0 | 79 edge e; |
| 80 edge_iterator ei; | |
| 81 int src, dest; | |
| 82 unsigned depth; | |
| 83 struct graph *g; | |
| 111 | 84 int num = number_of_loops (cfun); |
| 145 | 85 class loop *cloop; |
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86 bool irred_loop_found = false; |
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87 int i; |
| 0 | 88 |
| 89 gcc_assert (current_loops != NULL); | |
| 90 | |
| 91 /* Reset the flags. */ | |
| 111 | 92 FOR_BB_BETWEEN (act, ENTRY_BLOCK_PTR_FOR_FN (cfun), |
| 93 EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb) | |
| 0 | 94 { |
| 95 act->flags &= ~BB_IRREDUCIBLE_LOOP; | |
| 96 FOR_EACH_EDGE (e, ei, act->succs) | |
| 97 e->flags &= ~EDGE_IRREDUCIBLE_LOOP; | |
| 98 } | |
| 99 | |
| 100 /* Create the edge lists. */ | |
| 111 | 101 g = new_graph (last_basic_block_for_fn (cfun) + num); |
| 0 | 102 |
| 111 | 103 FOR_BB_BETWEEN (act, ENTRY_BLOCK_PTR_FOR_FN (cfun), |
| 104 EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb) | |
| 0 | 105 FOR_EACH_EDGE (e, ei, act->succs) |
| 106 { | |
| 107 /* Ignore edges to exit. */ | |
| 111 | 108 if (e->dest == EXIT_BLOCK_PTR_FOR_FN (cfun)) |
| 0 | 109 continue; |
| 110 | |
| 111 src = BB_REPR (act); | |
| 112 dest = BB_REPR (e->dest); | |
| 113 | |
| 114 /* Ignore latch edges. */ | |
| 115 if (e->dest->loop_father->header == e->dest | |
| 116 && e->dest->loop_father->latch == act) | |
| 117 continue; | |
| 118 | |
| 119 /* Edges inside a single loop should be left where they are. Edges | |
| 120 to subloop headers should lead to representative of the subloop, | |
| 121 but from the same place. | |
| 122 | |
| 123 Edges exiting loops should lead from representative | |
| 124 of the son of nearest common ancestor of the loops in that | |
| 125 act lays. */ | |
| 126 | |
| 127 if (e->dest->loop_father->header == e->dest) | |
| 128 dest = LOOP_REPR (e->dest->loop_father); | |
| 129 | |
| 130 if (!flow_bb_inside_loop_p (act->loop_father, e->dest)) | |
| 131 { | |
| 132 depth = 1 + loop_depth (find_common_loop (act->loop_father, | |
| 133 e->dest->loop_father)); | |
| 134 if (depth == loop_depth (act->loop_father)) | |
| 135 cloop = act->loop_father; | |
| 136 else | |
| 111 | 137 cloop = (*act->loop_father->superloops)[depth]; |
| 0 | 138 |
| 139 src = LOOP_REPR (cloop); | |
| 140 } | |
| 141 | |
| 142 add_edge (g, src, dest)->data = e; | |
| 143 } | |
| 144 | |
| 145 /* Find the strongly connected components. */ | |
| 146 graphds_scc (g, NULL); | |
| 147 | |
| 148 /* Mark the irreducible loops. */ | |
|
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149 for (i = 0; i < g->n_vertices; i++) |
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150 for (ge = g->vertices[i].succ; ge; ge = ge->succ_next) |
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151 { |
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152 edge real = (edge) ge->data; |
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153 /* edge E in graph G is irreducible if it connects two vertices in the |
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154 same scc. */ |
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155 |
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156 /* All edges should lead from a component with higher number to the |
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157 one with lower one. */ |
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158 gcc_assert (g->vertices[ge->src].component >= g->vertices[ge->dest].component); |
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159 |
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160 if (g->vertices[ge->src].component != g->vertices[ge->dest].component) |
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161 continue; |
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162 |
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163 real->flags |= EDGE_IRREDUCIBLE_LOOP; |
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164 irred_loop_found = true; |
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165 if (flow_bb_inside_loop_p (real->src->loop_father, real->dest)) |
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166 real->src->flags |= BB_IRREDUCIBLE_LOOP; |
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167 } |
| 0 | 168 |
| 169 free_graph (g); | |
| 170 | |
| 171 loops_state_set (LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS); | |
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172 return irred_loop_found; |
| 0 | 173 } |
| 174 | |
| 175 /* Counts number of insns inside LOOP. */ | |
| 176 int | |
| 145 | 177 num_loop_insns (const class loop *loop) |
| 0 | 178 { |
| 179 basic_block *bbs, bb; | |
| 180 unsigned i, ninsns = 0; | |
| 111 | 181 rtx_insn *insn; |
| 0 | 182 |
| 183 bbs = get_loop_body (loop); | |
| 184 for (i = 0; i < loop->num_nodes; i++) | |
| 185 { | |
| 186 bb = bbs[i]; | |
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187 FOR_BB_INSNS (bb, insn) |
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188 if (NONDEBUG_INSN_P (insn)) |
| 0 | 189 ninsns++; |
| 190 } | |
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191 free (bbs); |
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192 |
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193 if (!ninsns) |
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194 ninsns = 1; /* To avoid division by zero. */ |
| 0 | 195 |
| 196 return ninsns; | |
| 197 } | |
| 198 | |
| 199 /* Counts number of insns executed on average per iteration LOOP. */ | |
| 200 int | |
| 145 | 201 average_num_loop_insns (const class loop *loop) |
| 0 | 202 { |
| 203 basic_block *bbs, bb; | |
| 131 | 204 unsigned i, binsns; |
| 205 sreal ninsns; | |
| 111 | 206 rtx_insn *insn; |
| 0 | 207 |
| 208 ninsns = 0; | |
| 209 bbs = get_loop_body (loop); | |
| 210 for (i = 0; i < loop->num_nodes; i++) | |
| 211 { | |
| 212 bb = bbs[i]; | |
| 213 | |
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214 binsns = 0; |
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215 FOR_BB_INSNS (bb, insn) |
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216 if (NONDEBUG_INSN_P (insn)) |
| 0 | 217 binsns++; |
| 218 | |
| 131 | 219 ninsns += (sreal)binsns * bb->count.to_sreal_scale (loop->header->count); |
| 220 /* Avoid overflows. */ | |
| 221 if (ninsns > 1000000) | |
| 145 | 222 { |
| 223 free (bbs); | |
| 224 return 1000000; | |
| 225 } | |
| 0 | 226 } |
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227 free (bbs); |
| 0 | 228 |
| 131 | 229 int64_t ret = ninsns.to_int (); |
| 230 if (!ret) | |
| 231 ret = 1; /* To avoid division by zero. */ | |
| 0 | 232 |
| 131 | 233 return ret; |
| 0 | 234 } |
| 235 | |
| 236 /* Returns expected number of iterations of LOOP, according to | |
| 131 | 237 measured or guessed profile. |
| 238 | |
| 239 This functions attempts to return "sane" value even if profile | |
| 240 information is not good enough to derive osmething. | |
| 241 If BY_PROFILE_ONLY is set, this logic is bypassed and function | |
| 242 return -1 in those scenarios. */ | |
| 0 | 243 |
| 244 gcov_type | |
| 145 | 245 expected_loop_iterations_unbounded (const class loop *loop, |
| 131 | 246 bool *read_profile_p, |
| 247 bool by_profile_only) | |
| 0 | 248 { |
| 249 edge e; | |
| 250 edge_iterator ei; | |
| 111 | 251 gcov_type expected = -1; |
| 252 | |
| 253 if (read_profile_p) | |
| 254 *read_profile_p = false; | |
| 0 | 255 |
| 111 | 256 /* If we have no profile at all, use AVG_LOOP_NITER. */ |
| 257 if (profile_status_for_fn (cfun) == PROFILE_ABSENT) | |
| 131 | 258 { |
| 259 if (by_profile_only) | |
| 260 return -1; | |
| 145 | 261 expected = param_avg_loop_niter; |
| 131 | 262 } |
| 263 else if (loop->latch && (loop->latch->count.initialized_p () | |
| 264 || loop->header->count.initialized_p ())) | |
| 0 | 265 { |
| 111 | 266 profile_count count_in = profile_count::zero (), |
| 267 count_latch = profile_count::zero (); | |
| 0 | 268 |
| 269 FOR_EACH_EDGE (e, ei, loop->header->preds) | |
| 270 if (e->src == loop->latch) | |
| 111 | 271 count_latch = e->count (); |
| 0 | 272 else |
| 111 | 273 count_in += e->count (); |
| 0 | 274 |
| 111 | 275 if (!count_latch.initialized_p ()) |
| 131 | 276 { |
| 277 if (by_profile_only) | |
| 278 return -1; | |
| 145 | 279 expected = param_avg_loop_niter; |
| 131 | 280 } |
| 281 else if (!count_in.nonzero_p ()) | |
| 282 { | |
| 283 if (by_profile_only) | |
| 284 return -1; | |
| 285 expected = count_latch.to_gcov_type () * 2; | |
| 286 } | |
| 0 | 287 else |
| 111 | 288 { |
| 289 expected = (count_latch.to_gcov_type () + count_in.to_gcov_type () | |
| 290 - 1) / count_in.to_gcov_type (); | |
| 131 | 291 if (read_profile_p |
| 292 && count_latch.reliable_p () && count_in.reliable_p ()) | |
| 111 | 293 *read_profile_p = true; |
| 294 } | |
| 0 | 295 } |
| 131 | 296 else |
| 0 | 297 { |
| 131 | 298 if (by_profile_only) |
| 299 return -1; | |
| 145 | 300 expected = param_avg_loop_niter; |
| 111 | 301 } |
| 0 | 302 |
| 131 | 303 if (!by_profile_only) |
| 304 { | |
| 305 HOST_WIDE_INT max = get_max_loop_iterations_int (loop); | |
| 306 if (max != -1 && max < expected) | |
| 307 return max; | |
| 308 } | |
| 309 | |
| 111 | 310 return expected; |
| 0 | 311 } |
| 312 | |
| 313 /* Returns expected number of LOOP iterations. The returned value is bounded | |
| 314 by REG_BR_PROB_BASE. */ | |
| 315 | |
| 316 unsigned | |
| 145 | 317 expected_loop_iterations (class loop *loop) |
| 0 | 318 { |
| 319 gcov_type expected = expected_loop_iterations_unbounded (loop); | |
| 320 return (expected > REG_BR_PROB_BASE ? REG_BR_PROB_BASE : expected); | |
| 321 } | |
| 322 | |
| 323 /* Returns the maximum level of nesting of subloops of LOOP. */ | |
| 324 | |
| 325 unsigned | |
| 145 | 326 get_loop_level (const class loop *loop) |
| 0 | 327 { |
| 145 | 328 const class loop *ploop; |
| 0 | 329 unsigned mx = 0, l; |
| 330 | |
| 331 for (ploop = loop->inner; ploop; ploop = ploop->next) | |
| 332 { | |
| 333 l = get_loop_level (ploop); | |
| 334 if (l >= mx) | |
| 335 mx = l + 1; | |
| 336 } | |
| 337 return mx; | |
| 338 } | |
| 339 | |
| 340 /* Initialize the constants for computing set costs. */ | |
| 341 | |
| 342 void | |
| 343 init_set_costs (void) | |
| 344 { | |
| 345 int speed; | |
| 111 | 346 rtx_insn *seq; |
| 347 rtx reg1 = gen_raw_REG (SImode, LAST_VIRTUAL_REGISTER + 1); | |
| 348 rtx reg2 = gen_raw_REG (SImode, LAST_VIRTUAL_REGISTER + 2); | |
| 349 rtx addr = gen_raw_REG (Pmode, LAST_VIRTUAL_REGISTER + 3); | |
| 0 | 350 rtx mem = validize_mem (gen_rtx_MEM (SImode, addr)); |
| 351 unsigned i; | |
| 352 | |
| 353 target_avail_regs = 0; | |
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354 target_clobbered_regs = 0; |
| 0 | 355 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) |
| 356 if (TEST_HARD_REG_BIT (reg_class_contents[GENERAL_REGS], i) | |
| 357 && !fixed_regs[i]) | |
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358 { |
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359 target_avail_regs++; |
| 145 | 360 /* ??? This is only a rough heuristic. It doesn't cope well |
| 361 with alternative ABIs, but that's an optimization rather than | |
| 362 correctness issue. */ | |
| 363 if (default_function_abi.clobbers_full_reg_p (i)) | |
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364 target_clobbered_regs++; |
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365 } |
| 0 | 366 |
| 367 target_res_regs = 3; | |
| 368 | |
| 369 for (speed = 0; speed < 2; speed++) | |
| 370 { | |
| 371 crtl->maybe_hot_insn_p = speed; | |
| 372 /* Set up the costs for using extra registers: | |
| 373 | |
| 374 1) If not many free registers remain, we should prefer having an | |
| 375 additional move to decreasing the number of available registers. | |
| 376 (TARGET_REG_COST). | |
| 377 2) If no registers are available, we need to spill, which may require | |
| 378 storing the old value to memory and loading it back | |
| 379 (TARGET_SPILL_COST). */ | |
| 380 | |
| 381 start_sequence (); | |
| 382 emit_move_insn (reg1, reg2); | |
| 383 seq = get_insns (); | |
| 384 end_sequence (); | |
| 385 target_reg_cost [speed] = seq_cost (seq, speed); | |
| 386 | |
| 387 start_sequence (); | |
| 388 emit_move_insn (mem, reg1); | |
| 389 emit_move_insn (reg2, mem); | |
| 390 seq = get_insns (); | |
| 391 end_sequence (); | |
| 392 target_spill_cost [speed] = seq_cost (seq, speed); | |
| 393 } | |
| 394 default_rtl_profile (); | |
| 395 } | |
| 396 | |
| 397 /* Estimates cost of increased register pressure caused by making N_NEW new | |
| 398 registers live around the loop. N_OLD is the number of registers live | |
|
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399 around the loop. If CALL_P is true, also take into account that |
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parents:
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400 call-used registers may be clobbered in the loop body, reducing the |
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parents:
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401 number of available registers before we spill. */ |
| 0 | 402 |
| 403 unsigned | |
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404 estimate_reg_pressure_cost (unsigned n_new, unsigned n_old, bool speed, |
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405 bool call_p) |
| 0 | 406 { |
| 407 unsigned cost; | |
| 408 unsigned regs_needed = n_new + n_old; | |
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409 unsigned available_regs = target_avail_regs; |
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parents:
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410 |
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parents:
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411 /* If there is a call in the loop body, the call-clobbered registers |
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parents:
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412 are not available for loop invariants. */ |
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parents:
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413 if (call_p) |
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414 available_regs = available_regs - target_clobbered_regs; |
| 0 | 415 |
| 416 /* If we have enough registers, we should use them and not restrict | |
| 417 the transformations unnecessarily. */ | |
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418 if (regs_needed + target_res_regs <= available_regs) |
| 0 | 419 return 0; |
| 420 | |
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421 if (regs_needed <= available_regs) |
| 0 | 422 /* If we are close to running out of registers, try to preserve |
| 423 them. */ | |
| 424 cost = target_reg_cost [speed] * n_new; | |
| 425 else | |
| 426 /* If we run out of registers, it is very expensive to add another | |
| 427 one. */ | |
| 428 cost = target_spill_cost [speed] * n_new; | |
| 429 | |
| 430 if (optimize && (flag_ira_region == IRA_REGION_ALL | |
| 431 || flag_ira_region == IRA_REGION_MIXED) | |
| 145 | 432 && number_of_loops (cfun) <= (unsigned) param_ira_max_loops_num) |
| 0 | 433 /* IRA regional allocation deals with high register pressure |
| 434 better. So decrease the cost (to do more accurate the cost | |
| 435 calculation for IRA, we need to know how many registers lives | |
| 436 through the loop transparently). */ | |
| 437 cost /= 2; | |
| 438 | |
| 439 return cost; | |
| 440 } | |
| 441 | |
| 442 /* Sets EDGE_LOOP_EXIT flag for all loop exits. */ | |
| 443 | |
| 444 void | |
| 445 mark_loop_exit_edges (void) | |
| 446 { | |
| 447 basic_block bb; | |
| 448 edge e; | |
| 449 | |
| 111 | 450 if (number_of_loops (cfun) <= 1) |
| 0 | 451 return; |
| 452 | |
| 111 | 453 FOR_EACH_BB_FN (bb, cfun) |
| 0 | 454 { |
| 455 edge_iterator ei; | |
| 456 | |
| 457 FOR_EACH_EDGE (e, ei, bb->succs) | |
| 458 { | |
| 459 if (loop_outer (bb->loop_father) | |
| 460 && loop_exit_edge_p (bb->loop_father, e)) | |
| 461 e->flags |= EDGE_LOOP_EXIT; | |
| 462 else | |
| 463 e->flags &= ~EDGE_LOOP_EXIT; | |
| 464 } | |
| 465 } | |
| 466 } | |
| 467 | |
| 111 | 468 /* Return exit edge if loop has only one exit that is likely |
| 469 to be executed on runtime (i.e. it is not EH or leading | |
| 470 to noreturn call. */ | |
| 471 | |
| 472 edge | |
| 145 | 473 single_likely_exit (class loop *loop, vec<edge> exits) |
| 111 | 474 { |
| 475 edge found = single_exit (loop); | |
| 476 unsigned i; | |
| 477 edge ex; | |
| 478 | |
| 479 if (found) | |
| 480 return found; | |
| 481 FOR_EACH_VEC_ELT (exits, i, ex) | |
| 482 { | |
| 483 if (probably_never_executed_edge_p (cfun, ex) | |
| 484 /* We want to rule out paths to noreturns but not low probabilities | |
| 485 resulting from adjustments or combining. | |
| 486 FIXME: once we have better quality tracking, make this more | |
| 487 robust. */ | |
| 488 || ex->probability <= profile_probability::very_unlikely ()) | |
| 489 continue; | |
| 490 if (!found) | |
| 491 found = ex; | |
| 492 else | |
| 145 | 493 return NULL; |
| 111 | 494 } |
| 495 return found; | |
| 496 } | |
| 497 | |
| 498 | |
| 499 /* Gets basic blocks of a LOOP. Header is the 0-th block, rest is in dfs | |
| 500 order against direction of edges from latch. Specially, if | |
| 501 header != latch, latch is the 1-st block. */ | |
| 502 | |
| 503 vec<basic_block> | |
| 145 | 504 get_loop_hot_path (const class loop *loop) |
| 111 | 505 { |
| 506 basic_block bb = loop->header; | |
| 507 vec<basic_block> path = vNULL; | |
| 508 bitmap visited = BITMAP_ALLOC (NULL); | |
| 509 | |
| 510 while (true) | |
| 511 { | |
| 512 edge_iterator ei; | |
| 513 edge e; | |
| 514 edge best = NULL; | |
| 515 | |
| 516 path.safe_push (bb); | |
| 517 bitmap_set_bit (visited, bb->index); | |
| 518 FOR_EACH_EDGE (e, ei, bb->succs) | |
| 519 if ((!best || e->probability > best->probability) | |
| 520 && !loop_exit_edge_p (loop, e) | |
| 521 && !bitmap_bit_p (visited, e->dest->index)) | |
| 522 best = e; | |
| 523 if (!best || best->dest == loop->header) | |
| 524 break; | |
| 525 bb = best->dest; | |
| 526 } | |
| 527 BITMAP_FREE (visited); | |
| 528 return path; | |
| 529 } |