Mercurial > hg > CbC > CbC_gcc
annotate gcc/tree-ssa-threadedge.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 /* SSA Jump Threading |
| 145 | 2 Copyright (C) 2005-2020 Free Software Foundation, Inc. |
| 0 | 3 Contributed by Jeff Law <law@redhat.com> |
| 4 | |
| 5 This file is part of GCC. | |
| 6 | |
| 7 GCC is free software; you can redistribute it and/or modify | |
| 8 it under the terms of the GNU General Public License as published by | |
| 9 the Free Software Foundation; either version 3, or (at your option) | |
| 10 any later version. | |
| 11 | |
| 12 GCC is distributed in the hope that it will be useful, | |
| 13 but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 15 GNU General Public License 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" | |
| 111 | 24 #include "backend.h" |
| 0 | 25 #include "tree.h" |
| 111 | 26 #include "gimple.h" |
| 27 #include "predict.h" | |
| 28 #include "ssa.h" | |
| 29 #include "fold-const.h" | |
| 0 | 30 #include "cfgloop.h" |
| 111 | 31 #include "gimple-iterator.h" |
| 32 #include "tree-cfg.h" | |
| 33 #include "tree-ssa-threadupdate.h" | |
| 34 #include "tree-ssa-scopedtables.h" | |
| 35 #include "tree-ssa-threadedge.h" | |
| 36 #include "tree-ssa-dom.h" | |
| 37 #include "gimple-fold.h" | |
| 38 #include "cfganal.h" | |
| 131 | 39 #include "alloc-pool.h" |
| 40 #include "vr-values.h" | |
| 41 #include "gimple-ssa-evrp-analyze.h" | |
| 0 | 42 |
| 43 /* To avoid code explosion due to jump threading, we limit the | |
| 44 number of statements we are going to copy. This variable | |
| 45 holds the number of statements currently seen that we'll have | |
| 46 to copy as part of the jump threading process. */ | |
| 47 static int stmt_count; | |
| 48 | |
|
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49 /* Array to record value-handles per SSA_NAME. */ |
| 111 | 50 vec<tree> ssa_name_values; |
| 51 | |
| 52 typedef tree (pfn_simplify) (gimple *, gimple *, | |
| 53 class avail_exprs_stack *, | |
| 54 basic_block); | |
|
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55 |
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56 /* Set the value for the SSA name NAME to VALUE. */ |
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57 |
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58 void |
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59 set_ssa_name_value (tree name, tree value) |
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60 { |
| 111 | 61 if (SSA_NAME_VERSION (name) >= ssa_name_values.length ()) |
| 62 ssa_name_values.safe_grow_cleared (SSA_NAME_VERSION (name) + 1); | |
| 63 if (value && TREE_OVERFLOW_P (value)) | |
| 64 value = drop_tree_overflow (value); | |
| 65 ssa_name_values[SSA_NAME_VERSION (name)] = value; | |
|
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66 } |
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67 |
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68 /* Initialize the per SSA_NAME value-handles array. Returns it. */ |
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69 void |
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70 threadedge_initialize_values (void) |
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71 { |
| 111 | 72 gcc_assert (!ssa_name_values.exists ()); |
| 73 ssa_name_values.create (num_ssa_names); | |
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74 } |
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75 |
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76 /* Free the per SSA_NAME value-handle array. */ |
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77 void |
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78 threadedge_finalize_values (void) |
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79 { |
| 111 | 80 ssa_name_values.release (); |
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81 } |
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82 |
| 0 | 83 /* Return TRUE if we may be able to thread an incoming edge into |
| 84 BB to an outgoing edge from BB. Return FALSE otherwise. */ | |
| 85 | |
| 86 bool | |
| 87 potentially_threadable_block (basic_block bb) | |
| 88 { | |
| 89 gimple_stmt_iterator gsi; | |
| 90 | |
| 111 | 91 /* Special case. We can get blocks that are forwarders, but are |
| 92 not optimized away because they forward from outside a loop | |
| 93 to the loop header. We want to thread through them as we can | |
| 94 sometimes thread to the loop exit, which is obviously profitable. | |
| 95 the interesting case here is when the block has PHIs. */ | |
| 96 if (gsi_end_p (gsi_start_nondebug_bb (bb)) | |
| 97 && !gsi_end_p (gsi_start_phis (bb))) | |
| 98 return true; | |
| 99 | |
| 0 | 100 /* If BB has a single successor or a single predecessor, then |
| 101 there is no threading opportunity. */ | |
| 102 if (single_succ_p (bb) || single_pred_p (bb)) | |
| 103 return false; | |
| 104 | |
| 105 /* If BB does not end with a conditional, switch or computed goto, | |
| 106 then there is no threading opportunity. */ | |
| 107 gsi = gsi_last_bb (bb); | |
| 108 if (gsi_end_p (gsi) | |
| 109 || ! gsi_stmt (gsi) | |
| 110 || (gimple_code (gsi_stmt (gsi)) != GIMPLE_COND | |
| 111 && gimple_code (gsi_stmt (gsi)) != GIMPLE_GOTO | |
| 112 && gimple_code (gsi_stmt (gsi)) != GIMPLE_SWITCH)) | |
| 113 return false; | |
| 114 | |
| 115 return true; | |
| 116 } | |
| 117 | |
| 118 /* Record temporary equivalences created by PHIs at the target of the | |
| 131 | 119 edge E. Record unwind information for the equivalences into |
| 120 CONST_AND_COPIES and EVRP_RANGE_DATA. | |
| 0 | 121 |
| 122 If a PHI which prevents threading is encountered, then return FALSE | |
| 131 | 123 indicating we should not thread this edge, else return TRUE. */ |
| 0 | 124 |
| 125 static bool | |
| 131 | 126 record_temporary_equivalences_from_phis (edge e, |
| 127 const_and_copies *const_and_copies, | |
| 128 evrp_range_analyzer *evrp_range_analyzer) | |
| 0 | 129 { |
| 111 | 130 gphi_iterator gsi; |
| 0 | 131 |
| 132 /* Each PHI creates a temporary equivalence, record them. | |
| 133 These are context sensitive equivalences and will be removed | |
| 134 later. */ | |
| 135 for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi); gsi_next (&gsi)) | |
| 136 { | |
| 111 | 137 gphi *phi = gsi.phi (); |
| 0 | 138 tree src = PHI_ARG_DEF_FROM_EDGE (phi, e); |
| 139 tree dst = gimple_phi_result (phi); | |
| 140 | |
|
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141 /* If the desired argument is not the same as this PHI's result |
| 145 | 142 and it is set by a PHI in E->dest, then we cannot thread |
| 0 | 143 through E->dest. */ |
| 144 if (src != dst | |
| 145 && TREE_CODE (src) == SSA_NAME | |
| 146 && gimple_code (SSA_NAME_DEF_STMT (src)) == GIMPLE_PHI | |
| 147 && gimple_bb (SSA_NAME_DEF_STMT (src)) == e->dest) | |
| 148 return false; | |
| 149 | |
| 150 /* We consider any non-virtual PHI as a statement since it | |
| 151 count result in a constant assignment or copy operation. */ | |
| 111 | 152 if (!virtual_operand_p (dst)) |
| 0 | 153 stmt_count++; |
| 154 | |
| 111 | 155 const_and_copies->record_const_or_copy (dst, src); |
| 131 | 156 |
| 157 /* Also update the value range associated with DST, using | |
| 158 the range from SRC. | |
| 159 | |
| 160 Note that even if SRC is a constant we need to set a suitable | |
| 161 output range so that VR_UNDEFINED ranges do not leak through. */ | |
| 162 if (evrp_range_analyzer) | |
| 163 { | |
| 164 /* Get an empty new VR we can pass to update_value_range and save | |
| 165 away in the VR stack. */ | |
| 166 vr_values *vr_values = evrp_range_analyzer->get_vr_values (); | |
| 145 | 167 value_range_equiv *new_vr = vr_values->allocate_value_range_equiv (); |
| 168 new (new_vr) value_range_equiv (); | |
| 131 | 169 |
| 170 /* There are three cases to consider: | |
| 171 | |
| 172 First if SRC is an SSA_NAME, then we can copy the value | |
| 173 range from SRC into NEW_VR. | |
| 174 | |
| 175 Second if SRC is an INTEGER_CST, then we can just wet | |
| 176 NEW_VR to a singleton range. | |
| 177 | |
| 178 Otherwise set NEW_VR to varying. This may be overly | |
| 179 conservative. */ | |
| 180 if (TREE_CODE (src) == SSA_NAME) | |
| 181 new_vr->deep_copy (vr_values->get_value_range (src)); | |
| 182 else if (TREE_CODE (src) == INTEGER_CST) | |
| 145 | 183 new_vr->set (src); |
| 131 | 184 else |
| 145 | 185 new_vr->set_varying (TREE_TYPE (src)); |
| 131 | 186 |
| 187 /* This is a temporary range for DST, so push it. */ | |
| 188 evrp_range_analyzer->push_value_range (dst, new_vr); | |
| 189 } | |
| 0 | 190 } |
| 191 return true; | |
| 192 } | |
| 193 | |
| 111 | 194 /* Valueize hook for gimple_fold_stmt_to_constant_1. */ |
| 0 | 195 |
| 196 static tree | |
| 111 | 197 threadedge_valueize (tree t) |
| 0 | 198 { |
| 111 | 199 if (TREE_CODE (t) == SSA_NAME) |
| 0 | 200 { |
| 111 | 201 tree tem = SSA_NAME_VALUE (t); |
| 202 if (tem) | |
| 203 return tem; | |
| 0 | 204 } |
| 111 | 205 return t; |
| 0 | 206 } |
| 207 | |
| 208 /* Try to simplify each statement in E->dest, ultimately leading to | |
| 209 a simplification of the COND_EXPR at the end of E->dest. | |
| 210 | |
| 211 Record unwind information for temporary equivalences onto STACK. | |
| 212 | |
| 213 Use SIMPLIFY (a pointer to a callback function) to further simplify | |
|
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214 statements using pass specific information. |
| 0 | 215 |
| 216 We might consider marking just those statements which ultimately | |
| 217 feed the COND_EXPR. It's not clear if the overhead of bookkeeping | |
| 218 would be recovered by trying to simplify fewer statements. | |
| 219 | |
| 220 If we are able to simplify a statement into the form | |
| 221 SSA_NAME = (SSA_NAME | gimple invariant), then we can record | |
| 222 a context sensitive equivalence which may help us simplify | |
| 223 later statements in E->dest. */ | |
| 224 | |
| 111 | 225 static gimple * |
| 0 | 226 record_temporary_equivalences_from_stmts_at_dest (edge e, |
| 111 | 227 const_and_copies *const_and_copies, |
| 228 avail_exprs_stack *avail_exprs_stack, | |
| 131 | 229 evrp_range_analyzer *evrp_range_analyzer, |
| 111 | 230 pfn_simplify simplify) |
| 0 | 231 { |
| 111 | 232 gimple *stmt = NULL; |
| 0 | 233 gimple_stmt_iterator gsi; |
| 234 int max_stmt_count; | |
| 235 | |
| 145 | 236 max_stmt_count = param_max_jump_thread_duplication_stmts; |
| 0 | 237 |
| 238 /* Walk through each statement in the block recording equivalences | |
| 239 we discover. Note any equivalences we discover are context | |
| 240 sensitive (ie, are dependent on traversing E) and must be unwound | |
| 241 when we're finished processing E. */ | |
| 242 for (gsi = gsi_start_bb (e->dest); !gsi_end_p (gsi); gsi_next (&gsi)) | |
| 243 { | |
| 244 tree cached_lhs = NULL; | |
| 245 | |
| 246 stmt = gsi_stmt (gsi); | |
| 247 | |
| 248 /* Ignore empty statements and labels. */ | |
|
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249 if (gimple_code (stmt) == GIMPLE_NOP |
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250 || gimple_code (stmt) == GIMPLE_LABEL |
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251 || is_gimple_debug (stmt)) |
| 0 | 252 continue; |
| 253 | |
| 254 /* If the statement has volatile operands, then we assume we | |
| 145 | 255 cannot thread through this block. This is overly |
| 0 | 256 conservative in some ways. */ |
| 111 | 257 if (gimple_code (stmt) == GIMPLE_ASM |
| 258 && gimple_asm_volatile_p (as_a <gasm *> (stmt))) | |
| 259 return NULL; | |
| 260 | |
| 145 | 261 /* If the statement is a unique builtin, we cannot thread |
| 111 | 262 through here. */ |
| 263 if (gimple_code (stmt) == GIMPLE_CALL | |
| 264 && gimple_call_internal_p (stmt) | |
| 265 && gimple_call_internal_unique_p (stmt)) | |
| 0 | 266 return NULL; |
| 267 | |
| 268 /* If duplicating this block is going to cause too much code | |
| 269 expansion, then do not thread through this block. */ | |
| 270 stmt_count++; | |
| 271 if (stmt_count > max_stmt_count) | |
| 131 | 272 { |
| 273 /* If any of the stmts in the PATH's dests are going to be | |
| 274 killed due to threading, grow the max count | |
| 275 accordingly. */ | |
| 276 if (max_stmt_count | |
| 145 | 277 == param_max_jump_thread_duplication_stmts) |
| 131 | 278 { |
| 279 max_stmt_count += estimate_threading_killed_stmts (e->dest); | |
| 280 if (dump_file) | |
| 281 fprintf (dump_file, "threading bb %i up to %i stmts\n", | |
| 282 e->dest->index, max_stmt_count); | |
| 283 } | |
| 284 /* If we're still past the limit, we're done. */ | |
| 285 if (stmt_count > max_stmt_count) | |
| 286 return NULL; | |
| 287 } | |
| 288 | |
| 289 /* These are temporary ranges, do nto reflect them back into | |
| 290 the global range data. */ | |
| 291 if (evrp_range_analyzer) | |
| 292 evrp_range_analyzer->record_ranges_from_stmt (stmt, true); | |
| 0 | 293 |
| 294 /* If this is not a statement that sets an SSA_NAME to a new | |
| 295 value, then do not try to simplify this statement as it will | |
| 296 not simplify in any way that is helpful for jump threading. */ | |
| 297 if ((gimple_code (stmt) != GIMPLE_ASSIGN | |
| 298 || TREE_CODE (gimple_assign_lhs (stmt)) != SSA_NAME) | |
| 299 && (gimple_code (stmt) != GIMPLE_CALL | |
| 300 || gimple_call_lhs (stmt) == NULL_TREE | |
| 301 || TREE_CODE (gimple_call_lhs (stmt)) != SSA_NAME)) | |
| 302 continue; | |
| 303 | |
| 304 /* The result of __builtin_object_size depends on all the arguments | |
| 305 of a phi node. Temporarily using only one edge produces invalid | |
| 306 results. For example | |
| 307 | |
| 308 if (x < 6) | |
| 309 goto l; | |
| 310 else | |
| 311 goto l; | |
| 312 | |
| 313 l: | |
| 314 r = PHI <&w[2].a[1](2), &a.a[6](3)> | |
| 315 __builtin_object_size (r, 0) | |
| 316 | |
| 317 The result of __builtin_object_size is defined to be the maximum of | |
| 318 remaining bytes. If we use only one edge on the phi, the result will | |
| 319 change to be the remaining bytes for the corresponding phi argument. | |
| 320 | |
| 321 Similarly for __builtin_constant_p: | |
| 322 | |
| 323 r = PHI <1(2), 2(3)> | |
| 324 __builtin_constant_p (r) | |
| 325 | |
| 326 Both PHI arguments are constant, but x ? 1 : 2 is still not | |
| 327 constant. */ | |
| 328 | |
| 329 if (is_gimple_call (stmt)) | |
| 330 { | |
| 331 tree fndecl = gimple_call_fndecl (stmt); | |
| 332 if (fndecl | |
| 145 | 333 && fndecl_built_in_p (fndecl, BUILT_IN_NORMAL) |
| 0 | 334 && (DECL_FUNCTION_CODE (fndecl) == BUILT_IN_OBJECT_SIZE |
| 335 || DECL_FUNCTION_CODE (fndecl) == BUILT_IN_CONSTANT_P)) | |
| 336 continue; | |
| 337 } | |
| 338 | |
| 339 /* At this point we have a statement which assigns an RHS to an | |
| 340 SSA_VAR on the LHS. We want to try and simplify this statement | |
| 341 to expose more context sensitive equivalences which in turn may | |
|
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342 allow us to simplify the condition at the end of the loop. |
| 0 | 343 |
| 344 Handle simple copy operations as well as implied copies from | |
| 345 ASSERT_EXPRs. */ | |
| 346 if (gimple_assign_single_p (stmt) | |
| 347 && TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME) | |
| 348 cached_lhs = gimple_assign_rhs1 (stmt); | |
| 349 else if (gimple_assign_single_p (stmt) | |
| 350 && TREE_CODE (gimple_assign_rhs1 (stmt)) == ASSERT_EXPR) | |
| 351 cached_lhs = TREE_OPERAND (gimple_assign_rhs1 (stmt), 0); | |
| 352 else | |
| 353 { | |
| 354 /* A statement that is not a trivial copy or ASSERT_EXPR. | |
| 111 | 355 Try to fold the new expression. Inserting the |
| 356 expression into the hash table is unlikely to help. */ | |
| 357 /* ??? The DOM callback below can be changed to setting | |
| 358 the mprts_hook around the call to thread_across_edge, | |
| 359 avoiding the use substitution. The VRP hook should be | |
| 360 changed to properly valueize operands itself using | |
| 361 SSA_NAME_VALUE in addition to its own lattice. */ | |
| 362 cached_lhs = gimple_fold_stmt_to_constant_1 (stmt, | |
| 363 threadedge_valueize); | |
| 364 if (NUM_SSA_OPERANDS (stmt, SSA_OP_ALL_USES) != 0 | |
| 365 && (!cached_lhs | |
| 366 || (TREE_CODE (cached_lhs) != SSA_NAME | |
| 367 && !is_gimple_min_invariant (cached_lhs)))) | |
| 0 | 368 { |
| 111 | 369 /* We're going to temporarily copy propagate the operands |
| 370 and see if that allows us to simplify this statement. */ | |
| 371 tree *copy; | |
| 372 ssa_op_iter iter; | |
| 373 use_operand_p use_p; | |
| 374 unsigned int num, i = 0; | |
| 0 | 375 |
| 111 | 376 num = NUM_SSA_OPERANDS (stmt, SSA_OP_ALL_USES); |
| 377 copy = XALLOCAVEC (tree, num); | |
| 378 | |
| 379 /* Make a copy of the uses & vuses into USES_COPY, then cprop into | |
| 380 the operands. */ | |
| 381 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES) | |
| 382 { | |
| 383 tree tmp = NULL; | |
| 384 tree use = USE_FROM_PTR (use_p); | |
| 0 | 385 |
| 111 | 386 copy[i++] = use; |
| 387 if (TREE_CODE (use) == SSA_NAME) | |
| 388 tmp = SSA_NAME_VALUE (use); | |
| 389 if (tmp) | |
| 390 SET_USE (use_p, tmp); | |
| 391 } | |
| 0 | 392 |
| 111 | 393 cached_lhs = (*simplify) (stmt, stmt, avail_exprs_stack, e->src); |
|
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394 |
| 111 | 395 /* Restore the statement's original uses/defs. */ |
| 396 i = 0; | |
| 397 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES) | |
| 398 SET_USE (use_p, copy[i++]); | |
| 399 } | |
| 0 | 400 } |
| 401 | |
| 402 /* Record the context sensitive equivalence if we were able | |
| 403 to simplify this statement. */ | |
| 404 if (cached_lhs | |
| 405 && (TREE_CODE (cached_lhs) == SSA_NAME | |
| 406 || is_gimple_min_invariant (cached_lhs))) | |
| 111 | 407 const_and_copies->record_const_or_copy (gimple_get_lhs (stmt), |
| 408 cached_lhs); | |
| 0 | 409 } |
| 410 return stmt; | |
| 411 } | |
| 412 | |
| 111 | 413 static tree simplify_control_stmt_condition_1 (edge, gimple *, |
| 414 class avail_exprs_stack *, | |
| 415 tree, enum tree_code, tree, | |
| 416 gcond *, pfn_simplify, | |
| 417 unsigned); | |
| 418 | |
| 0 | 419 /* Simplify the control statement at the end of the block E->dest. |
| 420 | |
| 421 To avoid allocating memory unnecessarily, a scratch GIMPLE_COND | |
| 422 is available to use/clobber in DUMMY_COND. | |
| 423 | |
| 424 Use SIMPLIFY (a pointer to a callback function) to further simplify | |
| 425 a condition using pass specific information. | |
| 426 | |
| 427 Return the simplified condition or NULL if simplification could | |
| 111 | 428 not be performed. When simplifying a GIMPLE_SWITCH, we may return |
| 429 the CASE_LABEL_EXPR that will be taken. | |
| 430 | |
| 431 The available expression table is referenced via AVAIL_EXPRS_STACK. */ | |
| 0 | 432 |
| 433 static tree | |
| 434 simplify_control_stmt_condition (edge e, | |
| 111 | 435 gimple *stmt, |
| 436 class avail_exprs_stack *avail_exprs_stack, | |
| 437 gcond *dummy_cond, | |
| 438 pfn_simplify simplify) | |
| 0 | 439 { |
| 440 tree cond, cached_lhs; | |
| 441 enum gimple_code code = gimple_code (stmt); | |
| 442 | |
| 443 /* For comparisons, we have to update both operands, then try | |
| 444 to simplify the comparison. */ | |
| 445 if (code == GIMPLE_COND) | |
| 446 { | |
| 447 tree op0, op1; | |
| 448 enum tree_code cond_code; | |
| 449 | |
| 450 op0 = gimple_cond_lhs (stmt); | |
| 451 op1 = gimple_cond_rhs (stmt); | |
| 452 cond_code = gimple_cond_code (stmt); | |
| 453 | |
| 454 /* Get the current value of both operands. */ | |
| 455 if (TREE_CODE (op0) == SSA_NAME) | |
| 456 { | |
| 111 | 457 for (int i = 0; i < 2; i++) |
| 458 { | |
| 459 if (TREE_CODE (op0) == SSA_NAME | |
| 460 && SSA_NAME_VALUE (op0)) | |
| 461 op0 = SSA_NAME_VALUE (op0); | |
| 462 else | |
| 463 break; | |
| 464 } | |
| 0 | 465 } |
| 466 | |
| 467 if (TREE_CODE (op1) == SSA_NAME) | |
| 468 { | |
| 111 | 469 for (int i = 0; i < 2; i++) |
| 470 { | |
| 471 if (TREE_CODE (op1) == SSA_NAME | |
| 472 && SSA_NAME_VALUE (op1)) | |
| 473 op1 = SSA_NAME_VALUE (op1); | |
| 474 else | |
| 475 break; | |
| 476 } | |
| 0 | 477 } |
| 478 | |
| 111 | 479 const unsigned recursion_limit = 4; |
| 0 | 480 |
| 111 | 481 cached_lhs |
| 482 = simplify_control_stmt_condition_1 (e, stmt, avail_exprs_stack, | |
| 483 op0, cond_code, op1, | |
| 484 dummy_cond, simplify, | |
| 485 recursion_limit); | |
| 486 | |
| 487 /* If we were testing an integer/pointer against a constant, then | |
| 488 we can use the FSM code to trace the value of the SSA_NAME. If | |
| 489 a value is found, then the condition will collapse to a constant. | |
| 0 | 490 |
| 111 | 491 Return the SSA_NAME we want to trace back rather than the full |
| 492 expression and give the FSM threader a chance to find its value. */ | |
| 493 if (cached_lhs == NULL) | |
| 494 { | |
| 495 /* Recover the original operands. They may have been simplified | |
| 496 using context sensitive equivalences. Those context sensitive | |
| 497 equivalences may not be valid on paths found by the FSM optimizer. */ | |
| 498 tree op0 = gimple_cond_lhs (stmt); | |
| 499 tree op1 = gimple_cond_rhs (stmt); | |
| 0 | 500 |
| 111 | 501 if ((INTEGRAL_TYPE_P (TREE_TYPE (op0)) |
| 502 || POINTER_TYPE_P (TREE_TYPE (op0))) | |
| 503 && TREE_CODE (op0) == SSA_NAME | |
| 504 && TREE_CODE (op1) == INTEGER_CST) | |
| 505 return op0; | |
| 506 } | |
| 0 | 507 |
| 508 return cached_lhs; | |
| 509 } | |
| 510 | |
| 511 if (code == GIMPLE_SWITCH) | |
| 111 | 512 cond = gimple_switch_index (as_a <gswitch *> (stmt)); |
| 0 | 513 else if (code == GIMPLE_GOTO) |
| 514 cond = gimple_goto_dest (stmt); | |
| 515 else | |
| 516 gcc_unreachable (); | |
| 517 | |
| 518 /* We can have conditionals which just test the state of a variable | |
| 519 rather than use a relational operator. These are simpler to handle. */ | |
| 520 if (TREE_CODE (cond) == SSA_NAME) | |
| 521 { | |
| 111 | 522 tree original_lhs = cond; |
| 0 | 523 cached_lhs = cond; |
| 524 | |
| 525 /* Get the variable's current value from the equivalence chains. | |
| 526 | |
| 527 It is possible to get loops in the SSA_NAME_VALUE chains | |
| 528 (consider threading the backedge of a loop where we have | |
| 111 | 529 a loop invariant SSA_NAME used in the condition). */ |
| 530 if (cached_lhs) | |
| 531 { | |
| 532 for (int i = 0; i < 2; i++) | |
| 533 { | |
| 534 if (TREE_CODE (cached_lhs) == SSA_NAME | |
| 535 && SSA_NAME_VALUE (cached_lhs)) | |
| 536 cached_lhs = SSA_NAME_VALUE (cached_lhs); | |
| 537 else | |
| 538 break; | |
| 539 } | |
| 540 } | |
| 0 | 541 |
| 542 /* If we haven't simplified to an invariant yet, then use the | |
| 543 pass specific callback to try and simplify it further. */ | |
| 544 if (cached_lhs && ! is_gimple_min_invariant (cached_lhs)) | |
| 111 | 545 { |
| 546 if (code == GIMPLE_SWITCH) | |
| 547 { | |
| 548 /* Replace the index operand of the GIMPLE_SWITCH with any LHS | |
| 549 we found before handing off to VRP. If simplification is | |
| 550 possible, the simplified value will be a CASE_LABEL_EXPR of | |
| 551 the label that is proven to be taken. */ | |
| 552 gswitch *dummy_switch = as_a<gswitch *> (gimple_copy (stmt)); | |
| 553 gimple_switch_set_index (dummy_switch, cached_lhs); | |
| 554 cached_lhs = (*simplify) (dummy_switch, stmt, | |
| 555 avail_exprs_stack, e->src); | |
| 556 ggc_free (dummy_switch); | |
| 557 } | |
| 558 else | |
| 559 cached_lhs = (*simplify) (stmt, stmt, avail_exprs_stack, e->src); | |
| 560 } | |
| 561 | |
| 562 /* We couldn't find an invariant. But, callers of this | |
| 563 function may be able to do something useful with the | |
| 564 unmodified destination. */ | |
| 565 if (!cached_lhs) | |
| 566 cached_lhs = original_lhs; | |
| 0 | 567 } |
| 568 else | |
| 569 cached_lhs = NULL; | |
| 570 | |
| 571 return cached_lhs; | |
| 572 } | |
| 573 | |
| 111 | 574 /* Recursive helper for simplify_control_stmt_condition. */ |
| 575 | |
| 576 static tree | |
| 577 simplify_control_stmt_condition_1 (edge e, | |
| 578 gimple *stmt, | |
| 579 class avail_exprs_stack *avail_exprs_stack, | |
| 580 tree op0, | |
| 581 enum tree_code cond_code, | |
| 582 tree op1, | |
| 583 gcond *dummy_cond, | |
| 584 pfn_simplify simplify, | |
| 585 unsigned limit) | |
| 586 { | |
| 587 if (limit == 0) | |
| 588 return NULL_TREE; | |
| 589 | |
| 590 /* We may need to canonicalize the comparison. For | |
| 591 example, op0 might be a constant while op1 is an | |
| 592 SSA_NAME. Failure to canonicalize will cause us to | |
| 593 miss threading opportunities. */ | |
| 594 if (tree_swap_operands_p (op0, op1)) | |
| 595 { | |
| 596 cond_code = swap_tree_comparison (cond_code); | |
| 597 std::swap (op0, op1); | |
| 598 } | |
| 599 | |
| 600 /* If the condition has the form (A & B) CMP 0 or (A | B) CMP 0 then | |
| 601 recurse into the LHS to see if there is a dominating ASSERT_EXPR | |
| 602 of A or of B that makes this condition always true or always false | |
| 603 along the edge E. */ | |
| 604 if ((cond_code == EQ_EXPR || cond_code == NE_EXPR) | |
| 605 && TREE_CODE (op0) == SSA_NAME | |
| 606 && integer_zerop (op1)) | |
| 607 { | |
| 608 gimple *def_stmt = SSA_NAME_DEF_STMT (op0); | |
| 609 if (gimple_code (def_stmt) != GIMPLE_ASSIGN) | |
| 610 ; | |
| 611 else if (gimple_assign_rhs_code (def_stmt) == BIT_AND_EXPR | |
| 612 || gimple_assign_rhs_code (def_stmt) == BIT_IOR_EXPR) | |
| 613 { | |
| 614 enum tree_code rhs_code = gimple_assign_rhs_code (def_stmt); | |
| 615 const tree rhs1 = gimple_assign_rhs1 (def_stmt); | |
| 616 const tree rhs2 = gimple_assign_rhs2 (def_stmt); | |
| 617 | |
| 618 /* Is A != 0 ? */ | |
| 619 const tree res1 | |
| 620 = simplify_control_stmt_condition_1 (e, def_stmt, avail_exprs_stack, | |
| 621 rhs1, NE_EXPR, op1, | |
| 622 dummy_cond, simplify, | |
| 623 limit - 1); | |
| 624 if (res1 == NULL_TREE) | |
| 625 ; | |
| 626 else if (rhs_code == BIT_AND_EXPR && integer_zerop (res1)) | |
| 627 { | |
| 628 /* If A == 0 then (A & B) != 0 is always false. */ | |
| 629 if (cond_code == NE_EXPR) | |
| 630 return boolean_false_node; | |
| 631 /* If A == 0 then (A & B) == 0 is always true. */ | |
| 632 if (cond_code == EQ_EXPR) | |
| 633 return boolean_true_node; | |
| 634 } | |
| 635 else if (rhs_code == BIT_IOR_EXPR && integer_nonzerop (res1)) | |
| 636 { | |
| 637 /* If A != 0 then (A | B) != 0 is always true. */ | |
| 638 if (cond_code == NE_EXPR) | |
| 639 return boolean_true_node; | |
| 640 /* If A != 0 then (A | B) == 0 is always false. */ | |
| 641 if (cond_code == EQ_EXPR) | |
| 642 return boolean_false_node; | |
| 643 } | |
| 644 | |
| 645 /* Is B != 0 ? */ | |
| 646 const tree res2 | |
| 647 = simplify_control_stmt_condition_1 (e, def_stmt, avail_exprs_stack, | |
| 648 rhs2, NE_EXPR, op1, | |
| 649 dummy_cond, simplify, | |
| 650 limit - 1); | |
| 651 if (res2 == NULL_TREE) | |
| 652 ; | |
| 653 else if (rhs_code == BIT_AND_EXPR && integer_zerop (res2)) | |
| 654 { | |
| 655 /* If B == 0 then (A & B) != 0 is always false. */ | |
| 656 if (cond_code == NE_EXPR) | |
| 657 return boolean_false_node; | |
| 658 /* If B == 0 then (A & B) == 0 is always true. */ | |
| 659 if (cond_code == EQ_EXPR) | |
| 660 return boolean_true_node; | |
| 661 } | |
| 662 else if (rhs_code == BIT_IOR_EXPR && integer_nonzerop (res2)) | |
| 663 { | |
| 664 /* If B != 0 then (A | B) != 0 is always true. */ | |
| 665 if (cond_code == NE_EXPR) | |
| 666 return boolean_true_node; | |
| 667 /* If B != 0 then (A | B) == 0 is always false. */ | |
| 668 if (cond_code == EQ_EXPR) | |
| 669 return boolean_false_node; | |
| 670 } | |
| 671 | |
| 672 if (res1 != NULL_TREE && res2 != NULL_TREE) | |
| 673 { | |
| 674 if (rhs_code == BIT_AND_EXPR | |
| 675 && TYPE_PRECISION (TREE_TYPE (op0)) == 1 | |
| 676 && integer_nonzerop (res1) | |
| 677 && integer_nonzerop (res2)) | |
| 678 { | |
| 679 /* If A != 0 and B != 0 then (bool)(A & B) != 0 is true. */ | |
| 680 if (cond_code == NE_EXPR) | |
| 681 return boolean_true_node; | |
| 682 /* If A != 0 and B != 0 then (bool)(A & B) == 0 is false. */ | |
| 683 if (cond_code == EQ_EXPR) | |
| 684 return boolean_false_node; | |
| 685 } | |
| 686 | |
| 687 if (rhs_code == BIT_IOR_EXPR | |
| 688 && integer_zerop (res1) | |
| 689 && integer_zerop (res2)) | |
| 690 { | |
| 691 /* If A == 0 and B == 0 then (A | B) != 0 is false. */ | |
| 692 if (cond_code == NE_EXPR) | |
| 693 return boolean_false_node; | |
| 694 /* If A == 0 and B == 0 then (A | B) == 0 is true. */ | |
| 695 if (cond_code == EQ_EXPR) | |
| 696 return boolean_true_node; | |
| 697 } | |
| 698 } | |
| 699 } | |
| 700 /* Handle (A CMP B) CMP 0. */ | |
| 701 else if (TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt)) | |
| 702 == tcc_comparison) | |
| 703 { | |
| 704 tree rhs1 = gimple_assign_rhs1 (def_stmt); | |
| 705 tree rhs2 = gimple_assign_rhs2 (def_stmt); | |
| 706 | |
| 707 tree_code new_cond = gimple_assign_rhs_code (def_stmt); | |
| 708 if (cond_code == EQ_EXPR) | |
| 709 new_cond = invert_tree_comparison (new_cond, false); | |
| 710 | |
| 711 tree res | |
| 712 = simplify_control_stmt_condition_1 (e, def_stmt, avail_exprs_stack, | |
| 713 rhs1, new_cond, rhs2, | |
| 714 dummy_cond, simplify, | |
| 715 limit - 1); | |
| 716 if (res != NULL_TREE && is_gimple_min_invariant (res)) | |
| 717 return res; | |
| 718 } | |
| 719 } | |
| 720 | |
| 721 gimple_cond_set_code (dummy_cond, cond_code); | |
| 722 gimple_cond_set_lhs (dummy_cond, op0); | |
| 723 gimple_cond_set_rhs (dummy_cond, op1); | |
| 724 | |
| 725 /* We absolutely do not care about any type conversions | |
| 726 we only care about a zero/nonzero value. */ | |
| 727 fold_defer_overflow_warnings (); | |
| 728 | |
| 729 tree res = fold_binary (cond_code, boolean_type_node, op0, op1); | |
| 730 if (res) | |
| 731 while (CONVERT_EXPR_P (res)) | |
| 732 res = TREE_OPERAND (res, 0); | |
| 733 | |
| 734 fold_undefer_overflow_warnings ((res && is_gimple_min_invariant (res)), | |
| 735 stmt, WARN_STRICT_OVERFLOW_CONDITIONAL); | |
| 736 | |
| 737 /* If we have not simplified the condition down to an invariant, | |
| 738 then use the pass specific callback to simplify the condition. */ | |
| 739 if (!res | |
| 740 || !is_gimple_min_invariant (res)) | |
| 741 res = (*simplify) (dummy_cond, stmt, avail_exprs_stack, e->src); | |
| 742 | |
| 743 return res; | |
| 744 } | |
| 745 | |
| 746 /* Copy debug stmts from DEST's chain of single predecessors up to | |
| 747 SRC, so that we don't lose the bindings as PHI nodes are introduced | |
| 748 when DEST gains new predecessors. */ | |
| 749 void | |
| 750 propagate_threaded_block_debug_into (basic_block dest, basic_block src) | |
| 751 { | |
| 131 | 752 if (!MAY_HAVE_DEBUG_BIND_STMTS) |
| 111 | 753 return; |
| 754 | |
| 755 if (!single_pred_p (dest)) | |
| 756 return; | |
| 757 | |
| 758 gcc_checking_assert (dest != src); | |
| 759 | |
| 760 gimple_stmt_iterator gsi = gsi_after_labels (dest); | |
| 761 int i = 0; | |
| 762 const int alloc_count = 16; // ?? Should this be a PARAM? | |
| 763 | |
| 764 /* Estimate the number of debug vars overridden in the beginning of | |
| 765 DEST, to tell how many we're going to need to begin with. */ | |
| 766 for (gimple_stmt_iterator si = gsi; | |
| 767 i * 4 <= alloc_count * 3 && !gsi_end_p (si); gsi_next (&si)) | |
| 768 { | |
| 769 gimple *stmt = gsi_stmt (si); | |
| 770 if (!is_gimple_debug (stmt)) | |
| 771 break; | |
| 131 | 772 if (gimple_debug_nonbind_marker_p (stmt)) |
| 773 continue; | |
| 111 | 774 i++; |
| 775 } | |
| 776 | |
| 777 auto_vec<tree, alloc_count> fewvars; | |
| 778 hash_set<tree> *vars = NULL; | |
| 779 | |
| 780 /* If we're already starting with 3/4 of alloc_count, go for a | |
| 781 hash_set, otherwise start with an unordered stack-allocated | |
| 782 VEC. */ | |
| 783 if (i * 4 > alloc_count * 3) | |
| 784 vars = new hash_set<tree>; | |
| 785 | |
| 786 /* Now go through the initial debug stmts in DEST again, this time | |
| 787 actually inserting in VARS or FEWVARS. Don't bother checking for | |
| 788 duplicates in FEWVARS. */ | |
| 789 for (gimple_stmt_iterator si = gsi; !gsi_end_p (si); gsi_next (&si)) | |
| 790 { | |
| 791 gimple *stmt = gsi_stmt (si); | |
| 792 if (!is_gimple_debug (stmt)) | |
| 793 break; | |
| 794 | |
| 795 tree var; | |
| 796 | |
| 797 if (gimple_debug_bind_p (stmt)) | |
| 798 var = gimple_debug_bind_get_var (stmt); | |
| 799 else if (gimple_debug_source_bind_p (stmt)) | |
| 800 var = gimple_debug_source_bind_get_var (stmt); | |
| 131 | 801 else if (gimple_debug_nonbind_marker_p (stmt)) |
| 802 continue; | |
| 111 | 803 else |
| 804 gcc_unreachable (); | |
| 805 | |
| 806 if (vars) | |
| 807 vars->add (var); | |
| 808 else | |
| 809 fewvars.quick_push (var); | |
| 810 } | |
| 811 | |
| 812 basic_block bb = dest; | |
| 813 | |
| 814 do | |
| 815 { | |
| 816 bb = single_pred (bb); | |
| 817 for (gimple_stmt_iterator si = gsi_last_bb (bb); | |
| 818 !gsi_end_p (si); gsi_prev (&si)) | |
| 819 { | |
| 820 gimple *stmt = gsi_stmt (si); | |
| 821 if (!is_gimple_debug (stmt)) | |
| 822 continue; | |
| 823 | |
| 824 tree var; | |
| 825 | |
| 826 if (gimple_debug_bind_p (stmt)) | |
| 827 var = gimple_debug_bind_get_var (stmt); | |
| 828 else if (gimple_debug_source_bind_p (stmt)) | |
| 829 var = gimple_debug_source_bind_get_var (stmt); | |
| 131 | 830 else if (gimple_debug_nonbind_marker_p (stmt)) |
| 831 continue; | |
| 111 | 832 else |
| 833 gcc_unreachable (); | |
| 834 | |
| 131 | 835 /* Discard debug bind overlaps. Unlike stmts from src, |
| 111 | 836 copied into a new block that will precede BB, debug bind |
| 837 stmts in bypassed BBs may actually be discarded if | |
| 131 | 838 they're overwritten by subsequent debug bind stmts. We |
| 839 want to copy binds for all modified variables, so that we | |
| 840 retain a bind to the shared def if there is one, or to a | |
| 841 newly introduced PHI node if there is one. Our bind will | |
| 842 end up reset if the value is dead, but that implies the | |
| 843 variable couldn't have survived, so it's fine. We are | |
| 844 not actually running the code that performed the binds at | |
| 845 this point, we're just adding binds so that they survive | |
| 846 the new confluence, so markers should not be copied. */ | |
| 111 | 847 if (vars && vars->add (var)) |
| 848 continue; | |
| 849 else if (!vars) | |
| 850 { | |
| 851 int i = fewvars.length (); | |
| 852 while (i--) | |
| 853 if (fewvars[i] == var) | |
| 854 break; | |
| 855 if (i >= 0) | |
| 856 continue; | |
| 131 | 857 else if (fewvars.length () < (unsigned) alloc_count) |
| 111 | 858 fewvars.quick_push (var); |
| 859 else | |
| 860 { | |
| 861 vars = new hash_set<tree>; | |
| 862 for (i = 0; i < alloc_count; i++) | |
| 863 vars->add (fewvars[i]); | |
| 864 fewvars.release (); | |
| 865 vars->add (var); | |
| 866 } | |
| 867 } | |
| 868 | |
| 869 stmt = gimple_copy (stmt); | |
| 870 /* ??? Should we drop the location of the copy to denote | |
| 871 they're artificial bindings? */ | |
| 872 gsi_insert_before (&gsi, stmt, GSI_NEW_STMT); | |
| 873 } | |
| 874 } | |
| 875 while (bb != src && single_pred_p (bb)); | |
| 876 | |
| 877 if (vars) | |
| 878 delete vars; | |
| 879 else if (fewvars.exists ()) | |
| 880 fewvars.release (); | |
| 881 } | |
| 882 | |
| 883 /* See if TAKEN_EDGE->dest is a threadable block with no side effecs (ie, it | |
| 884 need not be duplicated as part of the CFG/SSA updating process). | |
| 885 | |
| 886 If it is threadable, add it to PATH and VISITED and recurse, ultimately | |
| 887 returning TRUE from the toplevel call. Otherwise do nothing and | |
| 888 return false. | |
| 889 | |
| 890 DUMMY_COND, SIMPLIFY are used to try and simplify the condition at the | |
| 891 end of TAKEN_EDGE->dest. | |
| 892 | |
| 893 The available expression table is referenced via AVAIL_EXPRS_STACK. */ | |
| 894 | |
| 895 static bool | |
| 896 thread_around_empty_blocks (edge taken_edge, | |
| 897 gcond *dummy_cond, | |
| 898 class avail_exprs_stack *avail_exprs_stack, | |
| 899 pfn_simplify simplify, | |
| 900 bitmap visited, | |
| 901 vec<jump_thread_edge *> *path) | |
| 902 { | |
| 903 basic_block bb = taken_edge->dest; | |
| 904 gimple_stmt_iterator gsi; | |
| 905 gimple *stmt; | |
| 906 tree cond; | |
| 907 | |
| 908 /* The key property of these blocks is that they need not be duplicated | |
| 145 | 909 when threading. Thus they cannot have visible side effects such |
| 111 | 910 as PHI nodes. */ |
| 911 if (!gsi_end_p (gsi_start_phis (bb))) | |
| 912 return false; | |
| 913 | |
| 914 /* Skip over DEBUG statements at the start of the block. */ | |
| 915 gsi = gsi_start_nondebug_bb (bb); | |
| 916 | |
| 917 /* If the block has no statements, but does have a single successor, then | |
| 918 it's just a forwarding block and we can thread through it trivially. | |
| 919 | |
| 920 However, note that just threading through empty blocks with single | |
| 921 successors is not inherently profitable. For the jump thread to | |
| 922 be profitable, we must avoid a runtime conditional. | |
| 923 | |
| 924 By taking the return value from the recursive call, we get the | |
| 925 desired effect of returning TRUE when we found a profitable jump | |
| 926 threading opportunity and FALSE otherwise. | |
| 927 | |
| 928 This is particularly important when this routine is called after | |
| 929 processing a joiner block. Returning TRUE too aggressively in | |
| 930 that case results in pointless duplication of the joiner block. */ | |
| 931 if (gsi_end_p (gsi)) | |
| 932 { | |
| 933 if (single_succ_p (bb)) | |
| 934 { | |
| 935 taken_edge = single_succ_edge (bb); | |
| 936 | |
| 937 if ((taken_edge->flags & EDGE_DFS_BACK) != 0) | |
| 938 return false; | |
| 939 | |
| 940 if (!bitmap_bit_p (visited, taken_edge->dest->index)) | |
| 941 { | |
| 942 jump_thread_edge *x | |
| 943 = new jump_thread_edge (taken_edge, EDGE_NO_COPY_SRC_BLOCK); | |
| 944 path->safe_push (x); | |
| 945 bitmap_set_bit (visited, taken_edge->dest->index); | |
| 946 return thread_around_empty_blocks (taken_edge, | |
| 947 dummy_cond, | |
| 948 avail_exprs_stack, | |
| 949 simplify, | |
| 950 visited, | |
| 951 path); | |
| 952 } | |
| 953 } | |
| 954 | |
| 955 /* We have a block with no statements, but multiple successors? */ | |
| 956 return false; | |
| 957 } | |
| 958 | |
| 959 /* The only real statements this block can have are a control | |
| 960 flow altering statement. Anything else stops the thread. */ | |
| 961 stmt = gsi_stmt (gsi); | |
| 962 if (gimple_code (stmt) != GIMPLE_COND | |
| 963 && gimple_code (stmt) != GIMPLE_GOTO | |
| 964 && gimple_code (stmt) != GIMPLE_SWITCH) | |
| 965 return false; | |
| 966 | |
| 967 /* Extract and simplify the condition. */ | |
| 968 cond = simplify_control_stmt_condition (taken_edge, stmt, | |
| 969 avail_exprs_stack, dummy_cond, | |
| 970 simplify); | |
| 971 | |
| 972 /* If the condition can be statically computed and we have not already | |
| 973 visited the destination edge, then add the taken edge to our thread | |
| 974 path. */ | |
| 975 if (cond != NULL_TREE | |
| 976 && (is_gimple_min_invariant (cond) | |
| 977 || TREE_CODE (cond) == CASE_LABEL_EXPR)) | |
| 978 { | |
| 979 if (TREE_CODE (cond) == CASE_LABEL_EXPR) | |
| 131 | 980 taken_edge = find_edge (bb, label_to_block (cfun, CASE_LABEL (cond))); |
| 111 | 981 else |
| 982 taken_edge = find_taken_edge (bb, cond); | |
| 983 | |
| 131 | 984 if (!taken_edge |
| 985 || (taken_edge->flags & EDGE_DFS_BACK) != 0) | |
| 111 | 986 return false; |
| 987 | |
| 988 if (bitmap_bit_p (visited, taken_edge->dest->index)) | |
| 989 return false; | |
| 990 bitmap_set_bit (visited, taken_edge->dest->index); | |
| 991 | |
| 992 jump_thread_edge *x | |
| 993 = new jump_thread_edge (taken_edge, EDGE_NO_COPY_SRC_BLOCK); | |
| 994 path->safe_push (x); | |
| 995 | |
| 996 thread_around_empty_blocks (taken_edge, | |
| 997 dummy_cond, | |
| 998 avail_exprs_stack, | |
| 999 simplify, | |
| 1000 visited, | |
| 1001 path); | |
| 1002 return true; | |
| 1003 } | |
| 1004 | |
| 1005 return false; | |
| 1006 } | |
| 1007 | |
| 0 | 1008 /* We are exiting E->src, see if E->dest ends with a conditional |
|
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0
diff
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|
1009 jump which has a known value when reached via E. |
| 0 | 1010 |
| 111 | 1011 E->dest can have arbitrary side effects which, if threading is |
| 1012 successful, will be maintained. | |
| 1013 | |
| 0 | 1014 Special care is necessary if E is a back edge in the CFG as we |
| 1015 may have already recorded equivalences for E->dest into our | |
| 1016 various tables, including the result of the conditional at | |
| 1017 the end of E->dest. Threading opportunities are severely | |
| 1018 limited in that case to avoid short-circuiting the loop | |
| 1019 incorrectly. | |
| 1020 | |
| 1021 DUMMY_COND is a shared cond_expr used by condition simplification as scratch, | |
| 1022 to avoid allocating memory. | |
|
55
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update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
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diff
changeset
|
1023 |
| 0 | 1024 STACK is used to undo temporary equivalences created during the walk of |
| 1025 E->dest. | |
| 1026 | |
| 111 | 1027 SIMPLIFY is a pass-specific function used to simplify statements. |
| 1028 | |
| 1029 Our caller is responsible for restoring the state of the expression | |
| 1030 and const_and_copies stacks. | |
| 0 | 1031 |
| 111 | 1032 Positive return value is success. Zero return value is failure, but |
| 1033 the block can still be duplicated as a joiner in a jump thread path, | |
| 1034 negative indicates the block should not be duplicated and thus is not | |
| 1035 suitable for a joiner in a jump threading path. */ | |
| 0 | 1036 |
| 111 | 1037 static int |
| 1038 thread_through_normal_block (edge e, | |
| 1039 gcond *dummy_cond, | |
| 1040 const_and_copies *const_and_copies, | |
| 1041 avail_exprs_stack *avail_exprs_stack, | |
| 131 | 1042 evrp_range_analyzer *evrp_range_analyzer, |
| 111 | 1043 pfn_simplify simplify, |
| 1044 vec<jump_thread_edge *> *path, | |
| 1045 bitmap visited) | |
| 1046 { | |
| 1047 /* We want to record any equivalences created by traversing E. */ | |
| 1048 record_temporary_equivalences (e, const_and_copies, avail_exprs_stack); | |
| 0 | 1049 |
| 111 | 1050 /* PHIs create temporary equivalences. |
| 1051 Note that if we found a PHI that made the block non-threadable, then | |
| 1052 we need to bubble that up to our caller in the same manner we do | |
| 1053 when we prematurely stop processing statements below. */ | |
| 131 | 1054 if (!record_temporary_equivalences_from_phis (e, const_and_copies, |
| 1055 evrp_range_analyzer)) | |
| 111 | 1056 return -1; |
| 0 | 1057 |
| 1058 /* Now walk each statement recording any context sensitive | |
| 1059 temporary equivalences we can detect. */ | |
| 111 | 1060 gimple *stmt |
| 1061 = record_temporary_equivalences_from_stmts_at_dest (e, const_and_copies, | |
| 1062 avail_exprs_stack, | |
| 131 | 1063 evrp_range_analyzer, |
| 111 | 1064 simplify); |
| 1065 | |
| 1066 /* There's two reasons STMT might be null, and distinguishing | |
| 1067 between them is important. | |
| 1068 | |
| 1069 First the block may not have had any statements. For example, it | |
| 1070 might have some PHIs and unconditionally transfer control elsewhere. | |
| 1071 Such blocks are suitable for jump threading, particularly as a | |
| 1072 joiner block. | |
| 1073 | |
| 1074 The second reason would be if we did not process all the statements | |
| 1075 in the block (because there were too many to make duplicating the | |
| 1076 block profitable. If we did not look at all the statements, then | |
| 1077 we may not have invalidated everything needing invalidation. Thus | |
| 1078 we must signal to our caller that this block is not suitable for | |
| 1079 use as a joiner in a threading path. */ | |
| 0 | 1080 if (!stmt) |
| 111 | 1081 { |
| 1082 /* First case. The statement simply doesn't have any instructions, but | |
| 1083 does have PHIs. */ | |
| 1084 if (gsi_end_p (gsi_start_nondebug_bb (e->dest)) | |
| 1085 && !gsi_end_p (gsi_start_phis (e->dest))) | |
| 1086 return 0; | |
| 1087 | |
| 1088 /* Second case. */ | |
| 1089 return -1; | |
| 1090 } | |
| 0 | 1091 |
| 1092 /* If we stopped at a COND_EXPR or SWITCH_EXPR, see if we know which arm | |
| 1093 will be taken. */ | |
| 1094 if (gimple_code (stmt) == GIMPLE_COND | |
| 1095 || gimple_code (stmt) == GIMPLE_GOTO | |
| 1096 || gimple_code (stmt) == GIMPLE_SWITCH) | |
| 1097 { | |
| 1098 tree cond; | |
| 1099 | |
| 1100 /* Extract and simplify the condition. */ | |
| 111 | 1101 cond = simplify_control_stmt_condition (e, stmt, avail_exprs_stack, |
| 1102 dummy_cond, simplify); | |
| 1103 | |
| 1104 if (!cond) | |
| 1105 return 0; | |
| 0 | 1106 |
| 111 | 1107 if (is_gimple_min_invariant (cond) |
| 1108 || TREE_CODE (cond) == CASE_LABEL_EXPR) | |
| 0 | 1109 { |
| 111 | 1110 edge taken_edge; |
| 1111 if (TREE_CODE (cond) == CASE_LABEL_EXPR) | |
| 1112 taken_edge = find_edge (e->dest, | |
| 131 | 1113 label_to_block (cfun, CASE_LABEL (cond))); |
| 111 | 1114 else |
| 1115 taken_edge = find_taken_edge (e->dest, cond); | |
| 1116 | |
| 0 | 1117 basic_block dest = (taken_edge ? taken_edge->dest : NULL); |
| 1118 | |
| 111 | 1119 /* DEST could be NULL for a computed jump to an absolute |
| 1120 address. */ | |
| 1121 if (dest == NULL | |
| 1122 || dest == e->dest | |
| 1123 || (taken_edge->flags & EDGE_DFS_BACK) != 0 | |
| 1124 || bitmap_bit_p (visited, dest->index)) | |
| 1125 return 0; | |
| 1126 | |
| 1127 /* Only push the EDGE_START_JUMP_THREAD marker if this is | |
| 1128 first edge on the path. */ | |
| 1129 if (path->length () == 0) | |
| 1130 { | |
| 1131 jump_thread_edge *x | |
| 1132 = new jump_thread_edge (e, EDGE_START_JUMP_THREAD); | |
| 1133 path->safe_push (x); | |
| 1134 } | |
| 1135 | |
| 1136 jump_thread_edge *x | |
| 1137 = new jump_thread_edge (taken_edge, EDGE_COPY_SRC_BLOCK); | |
| 1138 path->safe_push (x); | |
| 1139 | |
| 1140 /* See if we can thread through DEST as well, this helps capture | |
| 1141 secondary effects of threading without having to re-run DOM or | |
| 1142 VRP. | |
| 1143 | |
| 1144 We don't want to thread back to a block we have already | |
| 1145 visited. This may be overly conservative. */ | |
| 1146 bitmap_set_bit (visited, dest->index); | |
| 1147 bitmap_set_bit (visited, e->dest->index); | |
| 1148 thread_around_empty_blocks (taken_edge, | |
| 1149 dummy_cond, | |
| 1150 avail_exprs_stack, | |
| 1151 simplify, | |
| 1152 visited, | |
| 1153 path); | |
| 1154 return 1; | |
| 1155 } | |
| 1156 } | |
| 1157 return 0; | |
| 1158 } | |
| 1159 | |
| 145 | 1160 /* There are basic blocks look like: |
| 1161 <P0> | |
| 1162 p0 = a CMP b ; or p0 = (INT) (a CMP b) | |
| 1163 goto <X>; | |
| 1164 | |
| 1165 <P1> | |
| 1166 p1 = c CMP d | |
| 1167 goto <X>; | |
| 1168 | |
| 1169 <X> | |
| 1170 # phi = PHI <p0 (P0), p1 (P1)> | |
| 1171 if (phi != 0) goto <Y>; else goto <Z>; | |
| 1172 | |
| 1173 Then, edge (P0,X) or (P1,X) could be marked as EDGE_START_JUMP_THREAD | |
| 1174 And edge (X,Y), (X,Z) is EDGE_COPY_SRC_JOINER_BLOCK | |
| 1175 | |
| 1176 Return true if E is (P0,X) or (P1,X) */ | |
| 1177 | |
| 1178 bool | |
| 1179 edge_forwards_cmp_to_conditional_jump_through_empty_bb_p (edge e) | |
| 1180 { | |
| 1181 /* See if there is only one stmt which is gcond. */ | |
| 1182 gcond *gs; | |
| 1183 if (!(gs = safe_dyn_cast<gcond *> (last_and_only_stmt (e->dest)))) | |
| 1184 return false; | |
| 1185 | |
| 1186 /* See if gcond's cond is "(phi !=/== 0/1)" in the basic block. */ | |
| 1187 tree cond = gimple_cond_lhs (gs); | |
| 1188 enum tree_code code = gimple_cond_code (gs); | |
| 1189 tree rhs = gimple_cond_rhs (gs); | |
| 1190 if (TREE_CODE (cond) != SSA_NAME | |
| 1191 || (code != NE_EXPR && code != EQ_EXPR) | |
| 1192 || (!integer_onep (rhs) && !integer_zerop (rhs))) | |
| 1193 return false; | |
| 1194 gphi *phi = dyn_cast <gphi *> (SSA_NAME_DEF_STMT (cond)); | |
| 1195 if (phi == NULL || gimple_bb (phi) != e->dest) | |
| 1196 return false; | |
| 1197 | |
| 1198 /* Check if phi's incoming value is CMP. */ | |
| 1199 gassign *def; | |
| 1200 tree value = PHI_ARG_DEF_FROM_EDGE (phi, e); | |
| 1201 if (TREE_CODE (value) != SSA_NAME | |
| 1202 || !has_single_use (value) | |
| 1203 || !(def = dyn_cast <gassign *> (SSA_NAME_DEF_STMT (value)))) | |
| 1204 return false; | |
| 1205 | |
| 1206 /* Or if it is (INT) (a CMP b). */ | |
| 1207 if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def))) | |
| 1208 { | |
| 1209 value = gimple_assign_rhs1 (def); | |
| 1210 if (TREE_CODE (value) != SSA_NAME | |
| 1211 || !has_single_use (value) | |
| 1212 || !(def = dyn_cast<gassign *> (SSA_NAME_DEF_STMT (value)))) | |
| 1213 return false; | |
| 1214 } | |
| 1215 | |
| 1216 if (TREE_CODE_CLASS (gimple_assign_rhs_code (def)) != tcc_comparison) | |
| 1217 return false; | |
| 1218 | |
| 1219 return true; | |
| 1220 } | |
| 1221 | |
| 111 | 1222 /* We are exiting E->src, see if E->dest ends with a conditional |
| 1223 jump which has a known value when reached via E. | |
| 1224 | |
| 1225 DUMMY_COND is a shared cond_expr used by condition simplification as scratch, | |
| 1226 to avoid allocating memory. | |
| 1227 | |
| 1228 CONST_AND_COPIES is used to undo temporary equivalences created during the | |
| 1229 walk of E->dest. | |
| 1230 | |
| 1231 The available expression table is referenced vai AVAIL_EXPRS_STACK. | |
| 1232 | |
| 1233 SIMPLIFY is a pass-specific function used to simplify statements. */ | |
| 0 | 1234 |
| 111 | 1235 static void |
| 1236 thread_across_edge (gcond *dummy_cond, | |
| 1237 edge e, | |
| 1238 class const_and_copies *const_and_copies, | |
| 1239 class avail_exprs_stack *avail_exprs_stack, | |
| 131 | 1240 class evrp_range_analyzer *evrp_range_analyzer, |
| 111 | 1241 pfn_simplify simplify) |
| 1242 { | |
| 1243 bitmap visited = BITMAP_ALLOC (NULL); | |
| 1244 | |
| 1245 const_and_copies->push_marker (); | |
| 1246 avail_exprs_stack->push_marker (); | |
| 131 | 1247 if (evrp_range_analyzer) |
| 1248 evrp_range_analyzer->push_marker (); | |
| 111 | 1249 |
| 1250 stmt_count = 0; | |
| 1251 | |
| 1252 vec<jump_thread_edge *> *path = new vec<jump_thread_edge *> (); | |
| 1253 bitmap_clear (visited); | |
| 1254 bitmap_set_bit (visited, e->src->index); | |
| 1255 bitmap_set_bit (visited, e->dest->index); | |
| 1256 | |
| 1257 int threaded; | |
| 1258 if ((e->flags & EDGE_DFS_BACK) == 0) | |
| 1259 threaded = thread_through_normal_block (e, dummy_cond, | |
| 1260 const_and_copies, | |
| 1261 avail_exprs_stack, | |
| 131 | 1262 evrp_range_analyzer, |
| 111 | 1263 simplify, path, |
| 1264 visited); | |
| 1265 else | |
| 1266 threaded = 0; | |
| 1267 | |
| 1268 if (threaded > 0) | |
| 1269 { | |
| 1270 propagate_threaded_block_debug_into (path->last ()->e->dest, | |
| 1271 e->dest); | |
| 1272 const_and_copies->pop_to_marker (); | |
| 1273 avail_exprs_stack->pop_to_marker (); | |
| 131 | 1274 if (evrp_range_analyzer) |
| 1275 evrp_range_analyzer->pop_to_marker (); | |
| 111 | 1276 BITMAP_FREE (visited); |
| 1277 register_jump_thread (path); | |
| 1278 return; | |
| 1279 } | |
| 1280 else | |
| 1281 { | |
| 1282 /* Negative and zero return values indicate no threading was possible, | |
| 1283 thus there should be no edges on the thread path and no need to walk | |
| 1284 through the vector entries. */ | |
| 1285 gcc_assert (path->length () == 0); | |
| 1286 path->release (); | |
| 1287 delete path; | |
| 1288 | |
| 1289 /* A negative status indicates the target block was deemed too big to | |
| 1290 duplicate. Just quit now rather than trying to use the block as | |
| 1291 a joiner in a jump threading path. | |
| 1292 | |
| 1293 This prevents unnecessary code growth, but more importantly if we | |
| 1294 do not look at all the statements in the block, then we may have | |
| 1295 missed some invalidations if we had traversed a backedge! */ | |
| 1296 if (threaded < 0) | |
| 1297 { | |
| 1298 BITMAP_FREE (visited); | |
| 1299 const_and_copies->pop_to_marker (); | |
| 1300 avail_exprs_stack->pop_to_marker (); | |
| 131 | 1301 if (evrp_range_analyzer) |
| 1302 evrp_range_analyzer->pop_to_marker (); | |
| 111 | 1303 return; |
| 0 | 1304 } |
| 1305 } | |
| 1306 | |
| 111 | 1307 /* We were unable to determine what out edge from E->dest is taken. However, |
| 1308 we might still be able to thread through successors of E->dest. This | |
| 1309 often occurs when E->dest is a joiner block which then fans back out | |
| 1310 based on redundant tests. | |
| 1311 | |
| 1312 If so, we'll copy E->dest and redirect the appropriate predecessor to | |
| 1313 the copy. Within the copy of E->dest, we'll thread one or more edges | |
| 1314 to points deeper in the CFG. | |
| 1315 | |
| 1316 This is a stopgap until we have a more structured approach to path | |
| 1317 isolation. */ | |
| 1318 { | |
| 1319 edge taken_edge; | |
| 1320 edge_iterator ei; | |
| 1321 bool found; | |
| 1322 | |
| 1323 /* If E->dest has abnormal outgoing edges, then there's no guarantee | |
| 1324 we can safely redirect any of the edges. Just punt those cases. */ | |
| 1325 FOR_EACH_EDGE (taken_edge, ei, e->dest->succs) | |
| 145 | 1326 if (taken_edge->flags & EDGE_COMPLEX) |
| 111 | 1327 { |
| 1328 const_and_copies->pop_to_marker (); | |
| 1329 avail_exprs_stack->pop_to_marker (); | |
| 131 | 1330 if (evrp_range_analyzer) |
| 1331 evrp_range_analyzer->pop_to_marker (); | |
| 111 | 1332 BITMAP_FREE (visited); |
| 1333 return; | |
| 1334 } | |
| 1335 | |
| 1336 /* Look at each successor of E->dest to see if we can thread through it. */ | |
| 1337 FOR_EACH_EDGE (taken_edge, ei, e->dest->succs) | |
| 1338 { | |
| 1339 if ((e->flags & EDGE_DFS_BACK) != 0 | |
| 1340 || (taken_edge->flags & EDGE_DFS_BACK) != 0) | |
| 1341 continue; | |
| 1342 | |
| 1343 /* Push a fresh marker so we can unwind the equivalences created | |
| 1344 for each of E->dest's successors. */ | |
| 1345 const_and_copies->push_marker (); | |
| 1346 avail_exprs_stack->push_marker (); | |
| 131 | 1347 if (evrp_range_analyzer) |
| 1348 evrp_range_analyzer->push_marker (); | |
| 111 | 1349 |
| 1350 /* Avoid threading to any block we have already visited. */ | |
| 1351 bitmap_clear (visited); | |
| 1352 bitmap_set_bit (visited, e->src->index); | |
| 1353 bitmap_set_bit (visited, e->dest->index); | |
| 1354 bitmap_set_bit (visited, taken_edge->dest->index); | |
| 1355 vec<jump_thread_edge *> *path = new vec<jump_thread_edge *> (); | |
| 1356 | |
| 1357 /* Record whether or not we were able to thread through a successor | |
| 1358 of E->dest. */ | |
| 1359 jump_thread_edge *x = new jump_thread_edge (e, EDGE_START_JUMP_THREAD); | |
| 1360 path->safe_push (x); | |
| 1361 | |
| 1362 x = new jump_thread_edge (taken_edge, EDGE_COPY_SRC_JOINER_BLOCK); | |
| 1363 path->safe_push (x); | |
| 1364 found = thread_around_empty_blocks (taken_edge, | |
| 1365 dummy_cond, | |
| 1366 avail_exprs_stack, | |
| 1367 simplify, | |
| 1368 visited, | |
| 1369 path); | |
| 1370 | |
| 1371 if (!found) | |
| 1372 found = thread_through_normal_block (path->last ()->e, dummy_cond, | |
| 1373 const_and_copies, | |
| 1374 avail_exprs_stack, | |
| 131 | 1375 evrp_range_analyzer, |
| 111 | 1376 simplify, path, |
| 1377 visited) > 0; | |
| 1378 | |
| 1379 /* If we were able to thread through a successor of E->dest, then | |
| 1380 record the jump threading opportunity. */ | |
| 145 | 1381 if (found |
| 1382 || edge_forwards_cmp_to_conditional_jump_through_empty_bb_p (e)) | |
| 111 | 1383 { |
| 145 | 1384 if (taken_edge->dest != path->last ()->e->dest) |
| 1385 propagate_threaded_block_debug_into (path->last ()->e->dest, | |
| 1386 taken_edge->dest); | |
| 111 | 1387 register_jump_thread (path); |
| 1388 } | |
| 1389 else | |
| 1390 delete_jump_thread_path (path); | |
| 1391 | |
| 1392 /* And unwind the equivalence table. */ | |
| 131 | 1393 if (evrp_range_analyzer) |
| 1394 evrp_range_analyzer->pop_to_marker (); | |
| 111 | 1395 avail_exprs_stack->pop_to_marker (); |
| 1396 const_and_copies->pop_to_marker (); | |
| 1397 } | |
| 1398 BITMAP_FREE (visited); | |
| 1399 } | |
| 1400 | |
| 131 | 1401 if (evrp_range_analyzer) |
| 1402 evrp_range_analyzer->pop_to_marker (); | |
| 111 | 1403 const_and_copies->pop_to_marker (); |
| 1404 avail_exprs_stack->pop_to_marker (); | |
| 0 | 1405 } |
| 111 | 1406 |
| 1407 /* Examine the outgoing edges from BB and conditionally | |
| 1408 try to thread them. | |
| 1409 | |
| 1410 DUMMY_COND is a shared cond_expr used by condition simplification as scratch, | |
| 1411 to avoid allocating memory. | |
| 1412 | |
| 1413 CONST_AND_COPIES is used to undo temporary equivalences created during the | |
| 1414 walk of E->dest. | |
| 1415 | |
| 1416 The available expression table is referenced vai AVAIL_EXPRS_STACK. | |
| 1417 | |
| 1418 SIMPLIFY is a pass-specific function used to simplify statements. */ | |
| 1419 | |
| 1420 void | |
| 1421 thread_outgoing_edges (basic_block bb, gcond *dummy_cond, | |
| 1422 class const_and_copies *const_and_copies, | |
| 1423 class avail_exprs_stack *avail_exprs_stack, | |
| 131 | 1424 class evrp_range_analyzer *evrp_range_analyzer, |
| 111 | 1425 tree (*simplify) (gimple *, gimple *, |
| 1426 class avail_exprs_stack *, | |
| 1427 basic_block)) | |
| 1428 { | |
| 1429 int flags = (EDGE_IGNORE | EDGE_COMPLEX | EDGE_ABNORMAL); | |
| 1430 gimple *last; | |
| 1431 | |
| 1432 /* If we have an outgoing edge to a block with multiple incoming and | |
| 1433 outgoing edges, then we may be able to thread the edge, i.e., we | |
| 1434 may be able to statically determine which of the outgoing edges | |
| 1435 will be traversed when the incoming edge from BB is traversed. */ | |
| 1436 if (single_succ_p (bb) | |
| 1437 && (single_succ_edge (bb)->flags & flags) == 0 | |
| 1438 && potentially_threadable_block (single_succ (bb))) | |
| 1439 { | |
| 1440 thread_across_edge (dummy_cond, single_succ_edge (bb), | |
| 1441 const_and_copies, avail_exprs_stack, | |
| 131 | 1442 evrp_range_analyzer, simplify); |
| 111 | 1443 } |
| 1444 else if ((last = last_stmt (bb)) | |
| 1445 && gimple_code (last) == GIMPLE_COND | |
| 1446 && EDGE_COUNT (bb->succs) == 2 | |
| 1447 && (EDGE_SUCC (bb, 0)->flags & flags) == 0 | |
| 1448 && (EDGE_SUCC (bb, 1)->flags & flags) == 0) | |
| 1449 { | |
| 1450 edge true_edge, false_edge; | |
| 1451 | |
| 1452 extract_true_false_edges_from_block (bb, &true_edge, &false_edge); | |
| 1453 | |
| 1454 /* Only try to thread the edge if it reaches a target block with | |
| 1455 more than one predecessor and more than one successor. */ | |
| 1456 if (potentially_threadable_block (true_edge->dest)) | |
| 1457 thread_across_edge (dummy_cond, true_edge, | |
| 131 | 1458 const_and_copies, avail_exprs_stack, |
| 1459 evrp_range_analyzer, simplify); | |
| 111 | 1460 |
| 1461 /* Similarly for the ELSE arm. */ | |
| 1462 if (potentially_threadable_block (false_edge->dest)) | |
| 1463 thread_across_edge (dummy_cond, false_edge, | |
| 131 | 1464 const_and_copies, avail_exprs_stack, |
| 1465 evrp_range_analyzer, simplify); | |
| 111 | 1466 } |
| 1467 } |