Mercurial > hg > CbC > CbC_gcc
annotate gcc/tree-ssa-loop-unswitch.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 /* Loop unswitching. |
| 145 | 2 Copyright (C) 2004-2020 Free Software Foundation, Inc. |
|
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3 |
| 0 | 4 This file is part of GCC. |
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5 |
| 0 | 6 GCC is free software; you can redistribute it and/or modify it |
| 7 under the terms of the GNU General Public License as published by the | |
| 8 Free Software Foundation; either version 3, or (at your option) any | |
| 9 later version. | |
|
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10 |
| 0 | 11 GCC is distributed in the hope that it will be useful, but WITHOUT |
| 12 ANY 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. | |
|
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15 |
| 0 | 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 "tree.h" |
| 111 | 25 #include "gimple.h" |
| 26 #include "tree-pass.h" | |
| 27 #include "ssa.h" | |
| 28 #include "fold-const.h" | |
| 29 #include "gimplify.h" | |
| 30 #include "tree-cfg.h" | |
| 31 #include "tree-ssa.h" | |
| 32 #include "tree-ssa-loop-niter.h" | |
| 33 #include "tree-ssa-loop.h" | |
| 34 #include "tree-into-ssa.h" | |
| 0 | 35 #include "cfgloop.h" |
| 36 #include "tree-inline.h" | |
| 111 | 37 #include "gimple-iterator.h" |
| 38 #include "cfghooks.h" | |
| 39 #include "tree-ssa-loop-manip.h" | |
| 0 | 40 |
| 41 /* This file implements the loop unswitching, i.e. transformation of loops like | |
| 42 | |
| 43 while (A) | |
| 44 { | |
| 45 if (inv) | |
| 46 B; | |
| 47 | |
| 48 X; | |
| 49 | |
| 50 if (!inv) | |
| 51 C; | |
| 52 } | |
| 53 | |
| 54 where inv is the loop invariant, into | |
| 55 | |
| 56 if (inv) | |
| 57 { | |
| 58 while (A) | |
| 59 { | |
| 60 B; | |
| 61 X; | |
| 62 } | |
| 63 } | |
| 64 else | |
| 65 { | |
| 66 while (A) | |
| 67 { | |
| 68 X; | |
| 69 C; | |
| 70 } | |
| 71 } | |
| 72 | |
| 73 Inv is considered invariant iff the values it compares are both invariant; | |
| 74 tree-ssa-loop-im.c ensures that all the suitable conditions are in this | |
| 75 shape. */ | |
| 76 | |
| 145 | 77 static class loop *tree_unswitch_loop (class loop *, basic_block, tree); |
| 78 static bool tree_unswitch_single_loop (class loop *, int); | |
| 79 static tree tree_may_unswitch_on (basic_block, class loop *); | |
| 80 static bool tree_unswitch_outer_loop (class loop *); | |
| 81 static edge find_loop_guard (class loop *); | |
| 82 static bool empty_bb_without_guard_p (class loop *, basic_block); | |
| 83 static bool used_outside_loop_p (class loop *, tree); | |
| 84 static void hoist_guard (class loop *, edge); | |
| 85 static bool check_exit_phi (class loop *); | |
| 86 static tree get_vop_from_header (class loop *); | |
| 0 | 87 |
| 88 /* Main entry point. Perform loop unswitching on all suitable loops. */ | |
| 89 | |
| 90 unsigned int | |
| 91 tree_ssa_unswitch_loops (void) | |
| 92 { | |
| 145 | 93 class loop *loop; |
| 0 | 94 bool changed = false; |
| 95 | |
| 111 | 96 /* Go through all loops starting from innermost. */ |
| 97 FOR_EACH_LOOP (loop, LI_FROM_INNERMOST) | |
| 0 | 98 { |
| 111 | 99 if (!loop->inner) |
| 100 /* Unswitch innermost loop. */ | |
| 101 changed |= tree_unswitch_single_loop (loop, 0); | |
| 102 else | |
| 103 changed |= tree_unswitch_outer_loop (loop); | |
| 0 | 104 } |
| 105 | |
| 106 if (changed) | |
| 107 return TODO_cleanup_cfg; | |
| 108 return 0; | |
| 109 } | |
| 110 | |
| 111 | 111 /* Return TRUE if an SSA_NAME maybe undefined and is therefore |
| 112 unsuitable for unswitching. STMT is the statement we are | |
| 113 considering for unswitching and LOOP is the loop it appears in. */ | |
| 114 | |
| 115 static bool | |
| 145 | 116 is_maybe_undefined (const tree name, gimple *stmt, class loop *loop) |
| 111 | 117 { |
| 118 /* The loop header is the only block we can trivially determine that | |
| 119 will always be executed. If the comparison is in the loop | |
| 120 header, we know it's OK to unswitch on it. */ | |
| 121 if (gimple_bb (stmt) == loop->header) | |
| 122 return false; | |
| 123 | |
| 124 auto_bitmap visited_ssa; | |
| 125 auto_vec<tree> worklist; | |
| 126 worklist.safe_push (name); | |
| 127 bitmap_set_bit (visited_ssa, SSA_NAME_VERSION (name)); | |
| 128 while (!worklist.is_empty ()) | |
| 129 { | |
| 130 tree t = worklist.pop (); | |
| 131 | |
| 132 /* If it's obviously undefined, avoid further computations. */ | |
| 133 if (ssa_undefined_value_p (t, true)) | |
| 134 return true; | |
| 135 | |
| 136 if (ssa_defined_default_def_p (t)) | |
| 137 continue; | |
| 138 | |
| 139 gimple *def = SSA_NAME_DEF_STMT (t); | |
| 140 | |
| 141 /* Check that all the PHI args are fully defined. */ | |
| 142 if (gphi *phi = dyn_cast <gphi *> (def)) | |
| 143 { | |
| 144 for (unsigned i = 0; i < gimple_phi_num_args (phi); ++i) | |
| 145 { | |
| 146 tree t = gimple_phi_arg_def (phi, i); | |
| 147 /* If an SSA has already been seen, it may be a loop, | |
| 148 but we can continue and ignore this use. Otherwise, | |
| 149 add the SSA_NAME to the queue and visit it later. */ | |
| 150 if (TREE_CODE (t) == SSA_NAME | |
| 151 && bitmap_set_bit (visited_ssa, SSA_NAME_VERSION (t))) | |
| 152 worklist.safe_push (t); | |
| 153 } | |
| 154 continue; | |
| 155 } | |
| 156 | |
| 157 /* Uses in stmts always executed when the region header executes | |
| 158 are fine. */ | |
| 159 if (dominated_by_p (CDI_DOMINATORS, loop->header, gimple_bb (def))) | |
| 160 continue; | |
| 161 | |
| 162 /* Handle calls and memory loads conservatively. */ | |
| 163 if (!is_gimple_assign (def) | |
| 164 || (gimple_assign_single_p (def) | |
| 165 && gimple_vuse (def))) | |
| 166 return true; | |
| 167 | |
| 168 /* Check that any SSA names used to define NAME are also fully | |
| 169 defined. */ | |
| 170 use_operand_p use_p; | |
| 171 ssa_op_iter iter; | |
| 172 FOR_EACH_SSA_USE_OPERAND (use_p, def, iter, SSA_OP_USE) | |
| 173 { | |
| 174 tree t = USE_FROM_PTR (use_p); | |
| 175 /* If an SSA has already been seen, it may be a loop, | |
| 176 but we can continue and ignore this use. Otherwise, | |
| 177 add the SSA_NAME to the queue and visit it later. */ | |
| 178 if (bitmap_set_bit (visited_ssa, SSA_NAME_VERSION (t))) | |
| 179 worklist.safe_push (t); | |
| 180 } | |
| 181 } | |
| 182 return false; | |
| 183 } | |
| 184 | |
| 0 | 185 /* Checks whether we can unswitch LOOP on condition at end of BB -- one of its |
| 186 basic blocks (for what it means see comments below). */ | |
| 187 | |
| 188 static tree | |
| 145 | 189 tree_may_unswitch_on (basic_block bb, class loop *loop) |
| 0 | 190 { |
| 111 | 191 gimple *last, *def; |
| 192 gcond *stmt; | |
| 0 | 193 tree cond, use; |
| 194 basic_block def_bb; | |
| 195 ssa_op_iter iter; | |
| 196 | |
| 197 /* BB must end in a simple conditional jump. */ | |
| 111 | 198 last = last_stmt (bb); |
| 199 if (!last || gimple_code (last) != GIMPLE_COND) | |
| 0 | 200 return NULL_TREE; |
| 111 | 201 stmt = as_a <gcond *> (last); |
| 0 | 202 |
|
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203 /* To keep the things simple, we do not directly remove the conditions, |
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204 but just replace tests with 0 != 0 resp. 1 != 0. Prevent the infinite |
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205 loop where we would unswitch again on such a condition. */ |
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206 if (gimple_cond_true_p (stmt) || gimple_cond_false_p (stmt)) |
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207 return NULL_TREE; |
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208 |
| 0 | 209 /* Condition must be invariant. */ |
| 210 FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE) | |
| 211 { | |
| 212 def = SSA_NAME_DEF_STMT (use); | |
| 213 def_bb = gimple_bb (def); | |
| 214 if (def_bb | |
| 215 && flow_bb_inside_loop_p (loop, def_bb)) | |
| 216 return NULL_TREE; | |
| 111 | 217 /* Unswitching on undefined values would introduce undefined |
| 218 behavior that the original program might never exercise. */ | |
| 219 if (is_maybe_undefined (use, stmt, loop)) | |
| 220 return NULL_TREE; | |
| 0 | 221 } |
| 222 | |
| 223 cond = build2 (gimple_cond_code (stmt), boolean_type_node, | |
| 224 gimple_cond_lhs (stmt), gimple_cond_rhs (stmt)); | |
| 225 | |
| 226 return cond; | |
| 227 } | |
| 228 | |
| 229 /* Simplifies COND using checks in front of the entry of the LOOP. Just very | |
| 230 simplish (sufficient to prevent us from duplicating loop in unswitching | |
| 231 unnecessarily). */ | |
| 232 | |
| 233 static tree | |
| 145 | 234 simplify_using_entry_checks (class loop *loop, tree cond) |
| 0 | 235 { |
| 236 edge e = loop_preheader_edge (loop); | |
| 111 | 237 gimple *stmt; |
| 0 | 238 |
| 239 while (1) | |
| 240 { | |
| 241 stmt = last_stmt (e->src); | |
| 242 if (stmt | |
| 243 && gimple_code (stmt) == GIMPLE_COND | |
| 244 && gimple_cond_code (stmt) == TREE_CODE (cond) | |
| 245 && operand_equal_p (gimple_cond_lhs (stmt), | |
| 246 TREE_OPERAND (cond, 0), 0) | |
| 247 && operand_equal_p (gimple_cond_rhs (stmt), | |
| 248 TREE_OPERAND (cond, 1), 0)) | |
| 249 return (e->flags & EDGE_TRUE_VALUE | |
| 250 ? boolean_true_node | |
| 251 : boolean_false_node); | |
| 252 | |
| 253 if (!single_pred_p (e->src)) | |
| 254 return cond; | |
| 255 | |
| 256 e = single_pred_edge (e->src); | |
| 111 | 257 if (e->src == ENTRY_BLOCK_PTR_FOR_FN (cfun)) |
| 0 | 258 return cond; |
| 259 } | |
| 260 } | |
| 261 | |
| 262 /* Unswitch single LOOP. NUM is number of unswitchings done; we do not allow | |
| 263 it to grow too much, it is too easy to create example on that the code would | |
| 264 grow exponentially. */ | |
| 265 | |
| 266 static bool | |
| 145 | 267 tree_unswitch_single_loop (class loop *loop, int num) |
| 0 | 268 { |
| 269 basic_block *bbs; | |
| 145 | 270 class loop *nloop; |
|
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271 unsigned i, found; |
| 0 | 272 tree cond = NULL_TREE; |
| 111 | 273 gimple *stmt; |
| 0 | 274 bool changed = false; |
| 111 | 275 HOST_WIDE_INT iterations; |
| 276 | |
| 277 /* Perform initial tests if unswitch is eligible. */ | |
| 278 if (num == 0) | |
| 279 { | |
| 280 /* Do not unswitch in cold regions. */ | |
| 281 if (optimize_loop_for_size_p (loop)) | |
| 282 { | |
| 283 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 284 fprintf (dump_file, ";; Not unswitching cold loops\n"); | |
| 285 return false; | |
| 286 } | |
| 287 | |
| 288 /* The loop should not be too large, to limit code growth. */ | |
| 289 if (tree_num_loop_insns (loop, &eni_size_weights) | |
| 145 | 290 > (unsigned) param_max_unswitch_insns) |
| 111 | 291 { |
| 292 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 293 fprintf (dump_file, ";; Not unswitching, loop too big\n"); | |
| 294 return false; | |
| 295 } | |
| 296 | |
| 297 /* If the loop is not expected to iterate, there is no need | |
| 298 for unswitching. */ | |
| 299 iterations = estimated_loop_iterations_int (loop); | |
| 300 if (iterations < 0) | |
| 301 iterations = likely_max_loop_iterations_int (loop); | |
| 302 if (iterations >= 0 && iterations <= 1) | |
| 303 { | |
| 304 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 305 fprintf (dump_file, ";; Not unswitching, loop is not expected" | |
| 306 " to iterate\n"); | |
| 307 return false; | |
| 308 } | |
| 309 } | |
| 0 | 310 |
| 311 i = 0; | |
| 312 bbs = get_loop_body (loop); | |
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313 found = loop->num_nodes; |
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314 |
| 0 | 315 while (1) |
| 316 { | |
| 317 /* Find a bb to unswitch on. */ | |
| 318 for (; i < loop->num_nodes; i++) | |
| 319 if ((cond = tree_may_unswitch_on (bbs[i], loop))) | |
| 320 break; | |
| 321 | |
| 322 if (i == loop->num_nodes) | |
| 323 { | |
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324 if (dump_file |
| 145 | 325 && num > param_max_unswitch_level |
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326 && (dump_flags & TDF_DETAILS)) |
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327 fprintf (dump_file, ";; Not unswitching anymore, hit max level\n"); |
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328 |
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329 if (found == loop->num_nodes) |
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330 { |
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331 free (bbs); |
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332 return changed; |
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333 } |
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334 break; |
| 0 | 335 } |
| 336 | |
| 337 cond = simplify_using_entry_checks (loop, cond); | |
| 338 stmt = last_stmt (bbs[i]); | |
| 339 if (integer_nonzerop (cond)) | |
| 340 { | |
| 341 /* Remove false path. */ | |
| 111 | 342 gimple_cond_set_condition_from_tree (as_a <gcond *> (stmt), |
| 343 boolean_true_node); | |
| 0 | 344 changed = true; |
| 345 } | |
| 346 else if (integer_zerop (cond)) | |
| 347 { | |
| 348 /* Remove true path. */ | |
| 111 | 349 gimple_cond_set_condition_from_tree (as_a <gcond *> (stmt), |
| 350 boolean_false_node); | |
| 0 | 351 changed = true; |
| 352 } | |
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353 /* Do not unswitch too much. */ |
| 145 | 354 else if (num > param_max_unswitch_level) |
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355 { |
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356 i++; |
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357 continue; |
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358 } |
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359 /* In nested tree_unswitch_single_loop first optimize all conditions |
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360 using entry checks, then discover still reachable blocks in the |
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361 loop and find the condition only among those still reachable bbs. */ |
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362 else if (num != 0) |
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363 { |
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364 if (found == loop->num_nodes) |
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365 found = i; |
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366 i++; |
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367 continue; |
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368 } |
| 0 | 369 else |
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370 { |
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371 found = i; |
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372 break; |
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373 } |
| 0 | 374 |
| 375 update_stmt (stmt); | |
| 376 i++; | |
| 377 } | |
| 378 | |
|
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379 if (num != 0) |
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380 { |
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381 basic_block *tos, *worklist; |
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382 |
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383 /* When called recursively, first do a quick discovery |
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384 of reachable bbs after the above changes and only |
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385 consider conditions in still reachable bbs. */ |
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386 tos = worklist = XNEWVEC (basic_block, loop->num_nodes); |
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387 |
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388 for (i = 0; i < loop->num_nodes; i++) |
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389 bbs[i]->flags &= ~BB_REACHABLE; |
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390 |
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391 /* Start with marking header. */ |
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392 *tos++ = bbs[0]; |
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393 bbs[0]->flags |= BB_REACHABLE; |
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394 |
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395 /* Iterate: find everything reachable from what we've already seen |
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396 within the same innermost loop. Don't look through false edges |
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397 if condition is always true or true edges if condition is |
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398 always false. */ |
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399 while (tos != worklist) |
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400 { |
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401 basic_block b = *--tos; |
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402 edge e; |
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403 edge_iterator ei; |
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404 int flags = 0; |
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405 |
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406 if (EDGE_COUNT (b->succs) == 2) |
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407 { |
| 111 | 408 gimple *stmt = last_stmt (b); |
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409 if (stmt |
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410 && gimple_code (stmt) == GIMPLE_COND) |
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411 { |
| 111 | 412 gcond *cond_stmt = as_a <gcond *> (stmt); |
| 413 if (gimple_cond_true_p (cond_stmt)) | |
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414 flags = EDGE_FALSE_VALUE; |
| 111 | 415 else if (gimple_cond_false_p (cond_stmt)) |
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416 flags = EDGE_TRUE_VALUE; |
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417 } |
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418 } |
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419 |
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420 FOR_EACH_EDGE (e, ei, b->succs) |
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421 { |
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422 basic_block dest = e->dest; |
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423 |
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424 if (dest->loop_father == loop |
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425 && !(dest->flags & BB_REACHABLE) |
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426 && !(e->flags & flags)) |
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427 { |
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428 *tos++ = dest; |
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429 dest->flags |= BB_REACHABLE; |
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430 } |
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431 } |
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432 } |
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433 |
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434 free (worklist); |
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435 |
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436 /* Find a bb to unswitch on. */ |
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437 for (; found < loop->num_nodes; found++) |
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438 if ((bbs[found]->flags & BB_REACHABLE) |
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439 && (cond = tree_may_unswitch_on (bbs[found], loop))) |
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440 break; |
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441 |
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442 if (found == loop->num_nodes) |
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443 { |
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444 free (bbs); |
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445 return changed; |
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446 } |
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447 } |
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448 |
| 0 | 449 if (dump_file && (dump_flags & TDF_DETAILS)) |
| 450 fprintf (dump_file, ";; Unswitching loop\n"); | |
| 451 | |
| 452 initialize_original_copy_tables (); | |
| 453 /* Unswitch the loop on this condition. */ | |
|
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454 nloop = tree_unswitch_loop (loop, bbs[found], cond); |
| 0 | 455 if (!nloop) |
| 456 { | |
| 457 free_original_copy_tables (); | |
| 458 free (bbs); | |
| 459 return changed; | |
| 460 } | |
| 461 | |
| 462 /* Update the SSA form after unswitching. */ | |
| 463 update_ssa (TODO_update_ssa); | |
| 464 free_original_copy_tables (); | |
| 465 | |
| 466 /* Invoke itself on modified loops. */ | |
| 467 tree_unswitch_single_loop (nloop, num + 1); | |
| 468 tree_unswitch_single_loop (loop, num + 1); | |
| 469 free (bbs); | |
| 470 return true; | |
| 471 } | |
| 472 | |
| 473 /* Unswitch a LOOP w.r. to given basic block UNSWITCH_ON. We only support | |
| 474 unswitching of innermost loops. COND is the condition determining which | |
| 475 loop is entered -- the new loop is entered if COND is true. Returns NULL | |
| 476 if impossible, new loop otherwise. */ | |
| 477 | |
| 145 | 478 static class loop * |
| 479 tree_unswitch_loop (class loop *loop, | |
| 0 | 480 basic_block unswitch_on, tree cond) |
| 481 { | |
| 111 | 482 profile_probability prob_true; |
| 0 | 483 edge edge_true, edge_false; |
| 484 | |
| 485 /* Some sanity checking. */ | |
| 486 gcc_assert (flow_bb_inside_loop_p (loop, unswitch_on)); | |
| 487 gcc_assert (EDGE_COUNT (unswitch_on->succs) == 2); | |
| 488 gcc_assert (loop->inner == NULL); | |
| 489 | |
| 490 extract_true_false_edges_from_block (unswitch_on, &edge_true, &edge_false); | |
| 491 prob_true = edge_true->probability; | |
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492 return loop_version (loop, unshare_expr (cond), |
| 111 | 493 NULL, prob_true, |
| 494 prob_true.invert (), | |
| 495 prob_true, prob_true.invert (), | |
| 496 false); | |
| 497 } | |
| 498 | |
| 499 /* Unswitch outer loops by hoisting invariant guard on | |
| 500 inner loop without code duplication. */ | |
| 501 static bool | |
| 145 | 502 tree_unswitch_outer_loop (class loop *loop) |
| 111 | 503 { |
| 504 edge exit, guard; | |
| 505 HOST_WIDE_INT iterations; | |
| 506 | |
| 507 gcc_assert (loop->inner); | |
| 508 if (loop->inner->next) | |
| 509 return false; | |
| 510 /* Accept loops with single exit only which is not from inner loop. */ | |
| 511 exit = single_exit (loop); | |
| 512 if (!exit || exit->src->loop_father != loop) | |
| 513 return false; | |
| 514 /* Check that phi argument of exit edge is not defined inside loop. */ | |
| 515 if (!check_exit_phi (loop)) | |
| 516 return false; | |
| 517 /* If the loop is not expected to iterate, there is no need | |
| 518 for unswitching. */ | |
| 519 iterations = estimated_loop_iterations_int (loop); | |
| 520 if (iterations < 0) | |
| 521 iterations = likely_max_loop_iterations_int (loop); | |
| 522 if (iterations >= 0 && iterations <= 1) | |
| 523 { | |
| 524 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 525 fprintf (dump_file, ";; Not unswitching, loop is not expected" | |
| 526 " to iterate\n"); | |
| 527 return false; | |
| 528 } | |
| 529 | |
| 530 bool changed = false; | |
| 531 while ((guard = find_loop_guard (loop))) | |
| 532 { | |
| 533 if (! changed) | |
| 534 rewrite_virtuals_into_loop_closed_ssa (loop); | |
| 535 hoist_guard (loop, guard); | |
| 536 changed = true; | |
| 537 } | |
| 538 return changed; | |
| 539 } | |
| 540 | |
| 541 /* Checks if the body of the LOOP is within an invariant guard. If this | |
| 542 is the case, returns the edge that jumps over the real body of the loop, | |
| 543 otherwise returns NULL. */ | |
| 544 | |
| 545 static edge | |
| 145 | 546 find_loop_guard (class loop *loop) |
| 111 | 547 { |
| 548 basic_block header = loop->header; | |
| 549 edge guard_edge, te, fe; | |
| 550 basic_block *body = NULL; | |
| 551 unsigned i; | |
| 552 tree use; | |
| 553 ssa_op_iter iter; | |
| 554 | |
| 555 /* We check for the following situation: | |
| 556 | |
| 557 while (1) | |
| 558 { | |
| 559 [header]] | |
| 560 loop_phi_nodes; | |
| 561 something1; | |
| 562 if (cond1) | |
| 563 body; | |
| 564 nvar = phi(orig, bvar) ... for all variables changed in body; | |
| 565 [guard_end] | |
| 566 something2; | |
| 567 if (cond2) | |
| 568 break; | |
| 569 something3; | |
| 570 } | |
| 571 | |
| 572 where: | |
| 573 | |
| 574 1) cond1 is loop invariant | |
| 575 2) If cond1 is false, then the loop is essentially empty; i.e., | |
| 576 a) nothing in something1, something2 and something3 has side | |
| 577 effects | |
| 578 b) anything defined in something1, something2 and something3 | |
| 579 is not used outside of the loop. */ | |
| 580 | |
| 581 gcond *cond; | |
| 582 do | |
| 583 { | |
| 584 basic_block next = NULL; | |
| 585 if (single_succ_p (header)) | |
| 586 next = single_succ (header); | |
| 587 else | |
| 588 { | |
| 145 | 589 cond = safe_dyn_cast <gcond *> (last_stmt (header)); |
| 111 | 590 if (! cond) |
| 591 return NULL; | |
| 592 extract_true_false_edges_from_block (header, &te, &fe); | |
| 593 /* Make sure to skip earlier hoisted guards that are left | |
| 594 in place as if (true). */ | |
| 595 if (gimple_cond_true_p (cond)) | |
| 596 next = te->dest; | |
| 597 else if (gimple_cond_false_p (cond)) | |
| 598 next = fe->dest; | |
| 599 else | |
| 600 break; | |
| 601 } | |
| 602 /* Never traverse a backedge. */ | |
| 603 if (header->loop_father->header == next) | |
| 604 return NULL; | |
| 605 header = next; | |
| 606 } | |
| 607 while (1); | |
| 608 if (!flow_bb_inside_loop_p (loop, te->dest) | |
| 609 || !flow_bb_inside_loop_p (loop, fe->dest)) | |
| 610 return NULL; | |
| 611 | |
| 612 if (just_once_each_iteration_p (loop, te->dest) | |
| 613 || (single_succ_p (te->dest) | |
| 614 && just_once_each_iteration_p (loop, single_succ (te->dest)))) | |
| 615 { | |
| 616 if (just_once_each_iteration_p (loop, fe->dest)) | |
| 617 return NULL; | |
| 618 guard_edge = te; | |
| 619 } | |
| 620 else if (just_once_each_iteration_p (loop, fe->dest) | |
| 621 || (single_succ_p (fe->dest) | |
| 622 && just_once_each_iteration_p (loop, single_succ (fe->dest)))) | |
| 623 guard_edge = fe; | |
| 624 else | |
| 625 return NULL; | |
| 626 | |
| 627 /* Guard edge must skip inner loop. */ | |
| 628 if (!dominated_by_p (CDI_DOMINATORS, loop->inner->header, | |
| 629 guard_edge == fe ? te->dest : fe->dest)) | |
| 630 { | |
| 631 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 632 fprintf (dump_file, "Guard edge %d --> %d is not around the loop!\n", | |
| 633 guard_edge->src->index, guard_edge->dest->index); | |
| 634 return NULL; | |
| 635 } | |
| 636 if (guard_edge->dest == loop->latch) | |
| 637 { | |
| 638 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 639 fprintf (dump_file, "Guard edge destination is loop latch.\n"); | |
| 640 return NULL; | |
| 641 } | |
| 642 | |
| 643 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 644 fprintf (dump_file, | |
| 645 "Considering guard %d -> %d in loop %d\n", | |
| 646 guard_edge->src->index, guard_edge->dest->index, loop->num); | |
| 647 /* Check if condition operands do not have definitions inside loop since | |
| 648 any bb copying is not performed. */ | |
| 649 FOR_EACH_SSA_TREE_OPERAND (use, cond, iter, SSA_OP_USE) | |
| 650 { | |
| 651 gimple *def = SSA_NAME_DEF_STMT (use); | |
| 652 basic_block def_bb = gimple_bb (def); | |
| 653 if (def_bb | |
| 654 && flow_bb_inside_loop_p (loop, def_bb)) | |
| 655 { | |
| 656 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 657 fprintf (dump_file, " guard operands have definitions" | |
| 658 " inside loop\n"); | |
| 659 return NULL; | |
| 660 } | |
| 661 } | |
| 662 | |
| 663 body = get_loop_body (loop); | |
| 664 for (i = 0; i < loop->num_nodes; i++) | |
| 665 { | |
| 666 basic_block bb = body[i]; | |
| 667 if (bb->loop_father != loop) | |
| 668 continue; | |
| 669 if (bb->flags & BB_IRREDUCIBLE_LOOP) | |
| 670 { | |
| 671 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 672 fprintf (dump_file, "Block %d is marked as irreducible in loop\n", | |
| 673 bb->index); | |
| 674 guard_edge = NULL; | |
| 675 goto end; | |
| 676 } | |
| 677 if (!empty_bb_without_guard_p (loop, bb)) | |
| 678 { | |
| 679 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 680 fprintf (dump_file, " block %d has side effects\n", bb->index); | |
| 681 guard_edge = NULL; | |
| 682 goto end; | |
| 683 } | |
| 684 } | |
| 685 | |
| 686 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 687 fprintf (dump_file, " suitable to hoist\n"); | |
| 688 end: | |
| 689 if (body) | |
| 690 free (body); | |
| 691 return guard_edge; | |
| 692 } | |
| 693 | |
| 694 /* Returns true if | |
| 695 1) no statement in BB has side effects | |
| 696 2) assuming that edge GUARD is always taken, all definitions in BB | |
| 697 are noy used outside of the loop. | |
| 698 KNOWN_INVARIANTS is a set of ssa names we know to be invariant, and | |
| 699 PROCESSED is a set of ssa names for that we already tested whether they | |
| 700 are invariant or not. */ | |
| 701 | |
| 702 static bool | |
| 145 | 703 empty_bb_without_guard_p (class loop *loop, basic_block bb) |
| 111 | 704 { |
| 705 basic_block exit_bb = single_exit (loop)->src; | |
| 706 bool may_be_used_outside = (bb == exit_bb | |
| 707 || !dominated_by_p (CDI_DOMINATORS, bb, exit_bb)); | |
| 708 tree name; | |
| 709 ssa_op_iter op_iter; | |
| 710 | |
| 711 /* Phi nodes do not have side effects, but their results might be used | |
| 712 outside of the loop. */ | |
| 713 if (may_be_used_outside) | |
| 714 { | |
| 715 for (gphi_iterator gsi = gsi_start_phis (bb); | |
| 716 !gsi_end_p (gsi); gsi_next (&gsi)) | |
| 717 { | |
| 718 gphi *phi = gsi.phi (); | |
| 719 name = PHI_RESULT (phi); | |
| 720 if (virtual_operand_p (name)) | |
| 721 continue; | |
| 722 | |
| 723 if (used_outside_loop_p (loop, name)) | |
| 724 return false; | |
| 725 } | |
| 726 } | |
| 727 | |
| 728 for (gimple_stmt_iterator gsi = gsi_start_bb (bb); | |
| 729 !gsi_end_p (gsi); gsi_next (&gsi)) | |
| 730 { | |
| 731 gimple *stmt = gsi_stmt (gsi); | |
| 732 if (gimple_has_side_effects (stmt)) | |
| 733 return false; | |
| 734 | |
| 735 if (gimple_vdef(stmt)) | |
| 736 return false; | |
| 737 | |
| 738 FOR_EACH_SSA_TREE_OPERAND (name, stmt, op_iter, SSA_OP_DEF) | |
| 739 { | |
| 740 if (may_be_used_outside | |
| 741 && used_outside_loop_p (loop, name)) | |
| 742 return false; | |
| 743 } | |
| 744 } | |
| 745 return true; | |
| 0 | 746 } |
| 111 | 747 |
| 748 /* Return true if NAME is used outside of LOOP. */ | |
| 749 | |
| 750 static bool | |
| 145 | 751 used_outside_loop_p (class loop *loop, tree name) |
| 111 | 752 { |
| 753 imm_use_iterator it; | |
| 754 use_operand_p use; | |
| 755 | |
| 756 FOR_EACH_IMM_USE_FAST (use, it, name) | |
| 757 { | |
| 758 gimple *stmt = USE_STMT (use); | |
| 759 if (!flow_bb_inside_loop_p (loop, gimple_bb (stmt))) | |
| 760 return true; | |
| 761 } | |
| 762 | |
| 763 return false; | |
| 764 } | |
| 765 | |
| 766 /* Return argument for loop preheader edge in header virtual phi if any. */ | |
| 767 | |
| 768 static tree | |
| 145 | 769 get_vop_from_header (class loop *loop) |
| 111 | 770 { |
| 771 for (gphi_iterator gsi = gsi_start_phis (loop->header); | |
| 772 !gsi_end_p (gsi); gsi_next (&gsi)) | |
| 773 { | |
| 774 gphi *phi = gsi.phi (); | |
| 775 if (!virtual_operand_p (gimple_phi_result (phi))) | |
| 776 continue; | |
| 777 return PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (loop)); | |
| 778 } | |
| 779 return NULL_TREE; | |
| 780 } | |
| 781 | |
| 782 /* Move the check of GUARD outside of LOOP. */ | |
| 783 | |
| 784 static void | |
| 145 | 785 hoist_guard (class loop *loop, edge guard) |
| 111 | 786 { |
| 787 edge exit = single_exit (loop); | |
| 788 edge preh = loop_preheader_edge (loop); | |
| 789 basic_block pre_header = preh->src; | |
| 790 basic_block bb; | |
| 791 edge te, fe, e, new_edge; | |
| 792 gimple *stmt; | |
| 793 basic_block guard_bb = guard->src; | |
| 794 edge not_guard; | |
| 795 gimple_stmt_iterator gsi; | |
| 796 int flags = 0; | |
| 797 bool fix_dom_of_exit; | |
| 798 gcond *cond_stmt, *new_cond_stmt; | |
| 799 | |
| 800 bb = get_immediate_dominator (CDI_DOMINATORS, exit->dest); | |
| 801 fix_dom_of_exit = flow_bb_inside_loop_p (loop, bb); | |
| 802 gsi = gsi_last_bb (guard_bb); | |
| 803 stmt = gsi_stmt (gsi); | |
| 804 gcc_assert (gimple_code (stmt) == GIMPLE_COND); | |
| 805 cond_stmt = as_a <gcond *> (stmt); | |
| 806 extract_true_false_edges_from_block (guard_bb, &te, &fe); | |
| 807 /* Insert guard to PRE_HEADER. */ | |
| 808 if (!empty_block_p (pre_header)) | |
| 809 gsi = gsi_last_bb (pre_header); | |
| 810 else | |
| 811 gsi = gsi_start_bb (pre_header); | |
| 812 /* Create copy of COND_STMT. */ | |
| 813 new_cond_stmt = gimple_build_cond (gimple_cond_code (cond_stmt), | |
| 814 gimple_cond_lhs (cond_stmt), | |
| 815 gimple_cond_rhs (cond_stmt), | |
| 816 NULL_TREE, NULL_TREE); | |
| 817 gsi_insert_after (&gsi, new_cond_stmt, GSI_NEW_STMT); | |
| 818 /* Convert COND_STMT to true/false conditional. */ | |
| 819 if (guard == te) | |
| 820 gimple_cond_make_false (cond_stmt); | |
| 821 else | |
| 822 gimple_cond_make_true (cond_stmt); | |
| 823 update_stmt (cond_stmt); | |
| 824 /* Create new loop pre-header. */ | |
| 825 e = split_block (pre_header, last_stmt (pre_header)); | |
| 826 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 827 { | |
| 828 fprintf (dump_file, " Moving guard %i->%i (prob ", | |
| 829 guard->src->index, guard->dest->index); | |
| 830 guard->probability.dump (dump_file); | |
| 831 fprintf (dump_file, ") to bb %i, new preheader is %i\n", | |
| 832 e->src->index, e->dest->index); | |
| 833 } | |
| 834 | |
| 835 gcc_assert (loop_preheader_edge (loop)->src == e->dest); | |
| 836 | |
| 837 if (guard == fe) | |
| 838 { | |
| 839 e->flags = EDGE_TRUE_VALUE; | |
| 840 flags |= EDGE_FALSE_VALUE; | |
| 841 not_guard = te; | |
| 842 } | |
| 843 else | |
| 844 { | |
| 845 e->flags = EDGE_FALSE_VALUE; | |
| 846 flags |= EDGE_TRUE_VALUE; | |
| 847 not_guard = fe; | |
| 848 } | |
| 849 new_edge = make_edge (pre_header, exit->dest, flags); | |
| 850 | |
| 851 /* Determine the probability that we skip the loop. Assume that loop has | |
| 852 same average number of iterations regardless outcome of guard. */ | |
| 853 new_edge->probability = guard->probability; | |
| 131 | 854 profile_count skip_count = guard->src->count.nonzero_p () |
| 111 | 855 ? guard->count ().apply_scale (pre_header->count, |
| 856 guard->src->count) | |
| 857 : guard->count ().apply_probability (new_edge->probability); | |
| 858 | |
| 859 if (skip_count > e->count ()) | |
| 860 { | |
| 861 fprintf (dump_file, " Capping count; expect profile inconsistency\n"); | |
| 862 skip_count = e->count (); | |
| 863 } | |
| 864 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 865 { | |
| 866 fprintf (dump_file, " Estimated probability of skipping loop is "); | |
| 867 new_edge->probability.dump (dump_file); | |
| 868 fprintf (dump_file, "\n"); | |
| 869 } | |
| 870 | |
| 871 /* Update profile after the transform: | |
| 872 | |
| 873 First decrease count of path from newly hoisted loop guard | |
| 874 to loop header... */ | |
| 875 e->probability = new_edge->probability.invert (); | |
| 876 e->dest->count = e->count (); | |
| 877 | |
| 878 /* ... now update profile to represent that original guard will be optimized | |
| 879 away ... */ | |
| 880 guard->probability = profile_probability::never (); | |
| 881 not_guard->probability = profile_probability::always (); | |
| 882 | |
| 883 /* ... finally scale everything in the loop except for guarded basic blocks | |
| 884 where profile does not change. */ | |
| 885 basic_block *body = get_loop_body (loop); | |
| 886 | |
| 887 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 888 fprintf (dump_file, " Scaling nonguarded BBs in loop:"); | |
| 889 for (unsigned int i = 0; i < loop->num_nodes; i++) | |
| 890 { | |
| 891 basic_block bb = body[i]; | |
| 892 if (!dominated_by_p (CDI_DOMINATORS, bb, not_guard->dest)) | |
| 893 { | |
| 894 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 895 fprintf (dump_file, " %i", bb->index); | |
| 896 if (e->probability.initialized_p ()) | |
| 897 scale_bbs_frequencies (&bb, 1, e->probability); | |
| 898 } | |
| 899 } | |
| 900 | |
| 901 if (fix_dom_of_exit) | |
| 902 set_immediate_dominator (CDI_DOMINATORS, exit->dest, pre_header); | |
| 903 /* Add NEW_ADGE argument for all phi in post-header block. */ | |
| 904 bb = exit->dest; | |
| 905 for (gphi_iterator gsi = gsi_start_phis (bb); | |
| 906 !gsi_end_p (gsi); gsi_next (&gsi)) | |
| 907 { | |
| 908 gphi *phi = gsi.phi (); | |
| 909 tree arg; | |
| 910 if (virtual_operand_p (gimple_phi_result (phi))) | |
| 911 { | |
| 912 arg = get_vop_from_header (loop); | |
| 913 if (arg == NULL_TREE) | |
| 914 /* Use exit edge argument. */ | |
| 915 arg = PHI_ARG_DEF_FROM_EDGE (phi, exit); | |
| 916 add_phi_arg (phi, arg, new_edge, UNKNOWN_LOCATION); | |
| 917 } | |
| 918 else | |
| 919 { | |
| 920 /* Use exit edge argument. */ | |
| 921 arg = PHI_ARG_DEF_FROM_EDGE (phi, exit); | |
| 922 add_phi_arg (phi, arg, new_edge, UNKNOWN_LOCATION); | |
| 923 } | |
| 924 } | |
| 925 | |
| 926 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 927 fprintf (dump_file, "\n guard hoisted.\n"); | |
| 928 | |
| 929 free (body); | |
| 930 } | |
| 931 | |
| 932 /* Return true if phi argument for exit edge can be used | |
| 933 for edge around loop. */ | |
| 934 | |
| 935 static bool | |
| 145 | 936 check_exit_phi (class loop *loop) |
| 111 | 937 { |
| 938 edge exit = single_exit (loop); | |
| 939 basic_block pre_header = loop_preheader_edge (loop)->src; | |
| 940 | |
| 941 for (gphi_iterator gsi = gsi_start_phis (exit->dest); | |
| 942 !gsi_end_p (gsi); gsi_next (&gsi)) | |
| 943 { | |
| 944 gphi *phi = gsi.phi (); | |
| 945 tree arg; | |
| 946 gimple *def; | |
| 947 basic_block def_bb; | |
| 948 if (virtual_operand_p (gimple_phi_result (phi))) | |
| 949 continue; | |
| 950 arg = PHI_ARG_DEF_FROM_EDGE (phi, exit); | |
| 951 if (TREE_CODE (arg) != SSA_NAME) | |
| 952 continue; | |
| 953 def = SSA_NAME_DEF_STMT (arg); | |
| 954 if (!def) | |
| 955 continue; | |
| 956 def_bb = gimple_bb (def); | |
| 957 if (!def_bb) | |
| 958 continue; | |
| 959 if (!dominated_by_p (CDI_DOMINATORS, pre_header, def_bb)) | |
| 960 /* Definition inside loop! */ | |
| 961 return false; | |
| 962 /* Check loop closed phi invariant. */ | |
| 963 if (!flow_bb_inside_loop_p (def_bb->loop_father, pre_header)) | |
| 964 return false; | |
| 965 } | |
| 966 return true; | |
| 967 } | |
| 968 | |
| 969 /* Loop unswitching pass. */ | |
| 970 | |
| 971 namespace { | |
| 972 | |
| 973 const pass_data pass_data_tree_unswitch = | |
| 974 { | |
| 975 GIMPLE_PASS, /* type */ | |
| 976 "unswitch", /* name */ | |
| 977 OPTGROUP_LOOP, /* optinfo_flags */ | |
| 978 TV_TREE_LOOP_UNSWITCH, /* tv_id */ | |
| 979 PROP_cfg, /* properties_required */ | |
| 980 0, /* properties_provided */ | |
| 981 0, /* properties_destroyed */ | |
| 982 0, /* todo_flags_start */ | |
| 983 0, /* todo_flags_finish */ | |
| 984 }; | |
| 985 | |
| 986 class pass_tree_unswitch : public gimple_opt_pass | |
| 987 { | |
| 988 public: | |
| 989 pass_tree_unswitch (gcc::context *ctxt) | |
| 990 : gimple_opt_pass (pass_data_tree_unswitch, ctxt) | |
| 991 {} | |
| 992 | |
| 993 /* opt_pass methods: */ | |
| 994 virtual bool gate (function *) { return flag_unswitch_loops != 0; } | |
| 995 virtual unsigned int execute (function *); | |
| 996 | |
| 997 }; // class pass_tree_unswitch | |
| 998 | |
| 999 unsigned int | |
| 1000 pass_tree_unswitch::execute (function *fun) | |
| 1001 { | |
| 1002 if (number_of_loops (fun) <= 1) | |
| 1003 return 0; | |
| 1004 | |
| 1005 return tree_ssa_unswitch_loops (); | |
| 1006 } | |
| 1007 | |
| 1008 } // anon namespace | |
| 1009 | |
| 1010 gimple_opt_pass * | |
| 1011 make_pass_tree_unswitch (gcc::context *ctxt) | |
| 1012 { | |
| 1013 return new pass_tree_unswitch (ctxt); | |
| 1014 } | |
| 1015 | |
| 1016 |