Mercurial > hg > CbC > CbC_gcc
annotate gcc/tree-ssa-phiprop.c @ 36:855418dad1a3
gcc-4.4-20091020
| author | e075725 |
|---|---|
| date | Tue, 22 Dec 2009 21:19:31 +0900 |
| parents | 58ad6c70ea60 |
| children | 77e2b8dfacca |
| rev | line source |
|---|---|
| 0 | 1 /* Backward propagation of indirect loads through PHIs. |
| 2 Copyright (C) 2007, 2008 Free Software Foundation, Inc. | |
| 3 Contributed by Richard Guenther <rguenther@suse.de> | |
| 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" | |
| 24 #include "tm.h" | |
| 25 #include "ggc.h" | |
| 26 #include "tree.h" | |
| 27 #include "rtl.h" | |
| 28 #include "tm_p.h" | |
| 29 #include "basic-block.h" | |
| 30 #include "timevar.h" | |
| 31 #include "diagnostic.h" | |
| 32 #include "tree-flow.h" | |
| 33 #include "tree-pass.h" | |
| 34 #include "tree-dump.h" | |
| 35 #include "langhooks.h" | |
| 36 #include "flags.h" | |
| 37 | |
| 38 /* This pass propagates indirect loads through the PHI node for its | |
| 39 address to make the load source possibly non-addressable and to | |
| 40 allow for PHI optimization to trigger. | |
| 41 | |
| 42 For example the pass changes | |
| 43 | |
| 44 # addr_1 = PHI <&a, &b> | |
| 45 tmp_1 = *addr_1; | |
| 46 | |
| 47 to | |
| 48 | |
| 49 # tmp_1 = PHI <a, b> | |
| 50 | |
| 51 but also handles more complex scenarios like | |
| 52 | |
| 53 D.2077_2 = &this_1(D)->a1; | |
| 54 ... | |
| 55 | |
| 56 # b_12 = PHI <&c(2), D.2077_2(3)> | |
| 57 D.2114_13 = *b_12; | |
| 58 ... | |
| 59 | |
| 60 # b_15 = PHI <b_12(4), &b(5)> | |
| 61 D.2080_5 = &this_1(D)->a0; | |
| 62 ... | |
| 63 | |
| 64 # b_18 = PHI <D.2080_5(6), &c(7)> | |
| 65 ... | |
| 66 | |
| 67 # b_21 = PHI <b_15(8), b_18(9)> | |
| 68 D.2076_8 = *b_21; | |
| 69 | |
| 70 where the addresses loaded are defined by PHIs itself. | |
| 71 The above happens for | |
| 72 | |
| 73 std::max(std::min(a0, c), std::min(std::max(a1, c), b)) | |
| 74 | |
| 75 where this pass transforms it to a form later PHI optimization | |
| 76 recognizes and transforms it to the simple | |
| 77 | |
| 78 D.2109_10 = this_1(D)->a1; | |
| 79 D.2110_11 = c; | |
| 80 D.2114_31 = MAX_EXPR <D.2109_10, D.2110_11>; | |
| 81 D.2115_14 = b; | |
| 82 D.2125_17 = MIN_EXPR <D.2115_14, D.2114_31>; | |
| 83 D.2119_16 = this_1(D)->a0; | |
| 84 D.2124_32 = MIN_EXPR <D.2110_11, D.2119_16>; | |
| 85 D.2076_33 = MAX_EXPR <D.2125_17, D.2124_32>; | |
| 86 | |
| 87 The pass does a dominator walk processing loads using a basic-block | |
| 88 local analysis and stores the result for use by transformations on | |
| 89 dominated basic-blocks. */ | |
| 90 | |
| 91 | |
| 92 /* Structure to keep track of the value of a dereferenced PHI result | |
| 93 and the set of virtual operands used for that dereference. */ | |
| 94 | |
| 95 struct phiprop_d | |
| 96 { | |
| 97 tree value; | |
| 98 gimple vop_stmt; | |
| 99 }; | |
| 100 | |
| 101 /* Verify if the value recorded for NAME in PHIVN is still valid at | |
| 102 the start of basic block BB. */ | |
| 103 | |
| 104 static bool | |
| 105 phivn_valid_p (struct phiprop_d *phivn, tree name, basic_block bb) | |
| 106 { | |
| 107 gimple vop_stmt = phivn[SSA_NAME_VERSION (name)].vop_stmt; | |
| 108 ssa_op_iter ui; | |
| 109 tree vuse; | |
| 110 | |
| 111 /* The def stmts of all virtual uses need to be post-dominated | |
| 112 by bb. */ | |
| 113 FOR_EACH_SSA_TREE_OPERAND (vuse, vop_stmt, ui, SSA_OP_VUSE) | |
| 114 { | |
| 115 gimple use_stmt; | |
| 116 imm_use_iterator ui2; | |
| 117 bool ok = true; | |
| 118 | |
| 119 FOR_EACH_IMM_USE_STMT (use_stmt, ui2, vuse) | |
| 120 { | |
| 121 /* If BB does not dominate a VDEF, the value is invalid. */ | |
|
19
58ad6c70ea60
update gcc from 4.4.0 to 4.4.1.
kent@firefly.cr.ie.u-ryukyu.ac.jp
parents:
0
diff
changeset
|
122 if ((!ZERO_SSA_OPERANDS (use_stmt, SSA_OP_VDEF) |
| 0 | 123 || gimple_code (use_stmt) == GIMPLE_PHI) |
| 124 && !dominated_by_p (CDI_DOMINATORS, gimple_bb (use_stmt), bb)) | |
| 125 { | |
| 126 ok = false; | |
| 127 BREAK_FROM_IMM_USE_STMT (ui2); | |
| 128 } | |
| 129 } | |
| 130 if (!ok) | |
| 131 return false; | |
| 132 } | |
| 133 | |
| 134 return true; | |
| 135 } | |
| 136 | |
| 137 /* Insert a new phi node for the dereference of PHI at basic_block | |
| 138 BB with the virtual operands from USE_STMT. */ | |
| 139 | |
| 140 static tree | |
| 141 phiprop_insert_phi (basic_block bb, gimple phi, gimple use_stmt, | |
| 142 struct phiprop_d *phivn, size_t n) | |
| 143 { | |
| 144 tree res; | |
| 145 gimple new_phi; | |
| 146 edge_iterator ei; | |
| 147 edge e; | |
| 148 | |
| 149 gcc_assert (is_gimple_assign (use_stmt) | |
| 150 && gimple_assign_rhs_code (use_stmt) == INDIRECT_REF); | |
| 151 | |
| 152 /* Build a new PHI node to replace the definition of | |
| 153 the indirect reference lhs. */ | |
| 154 res = gimple_assign_lhs (use_stmt); | |
| 155 SSA_NAME_DEF_STMT (res) = new_phi = create_phi_node (res, bb); | |
| 156 | |
| 157 /* Add PHI arguments for each edge inserting loads of the | |
| 158 addressable operands. */ | |
| 159 FOR_EACH_EDGE (e, ei, bb->preds) | |
| 160 { | |
| 161 tree old_arg, new_var; | |
| 162 gimple tmp; | |
| 163 | |
| 164 old_arg = PHI_ARG_DEF_FROM_EDGE (phi, e); | |
| 165 while (TREE_CODE (old_arg) == SSA_NAME | |
| 166 && (SSA_NAME_VERSION (old_arg) >= n | |
| 167 || phivn[SSA_NAME_VERSION (old_arg)].value == NULL_TREE)) | |
| 168 { | |
| 169 gimple def_stmt = SSA_NAME_DEF_STMT (old_arg); | |
| 170 old_arg = gimple_assign_rhs1 (def_stmt); | |
| 171 } | |
| 172 | |
| 173 if (TREE_CODE (old_arg) == SSA_NAME) | |
| 174 /* Reuse a formerly created dereference. */ | |
| 175 new_var = phivn[SSA_NAME_VERSION (old_arg)].value; | |
| 176 else | |
| 177 { | |
| 178 gcc_assert (TREE_CODE (old_arg) == ADDR_EXPR); | |
| 179 old_arg = TREE_OPERAND (old_arg, 0); | |
| 180 new_var = create_tmp_var (TREE_TYPE (old_arg), NULL); | |
| 181 tmp = gimple_build_assign (new_var, unshare_expr (old_arg)); | |
| 182 if (TREE_CODE (TREE_TYPE (old_arg)) == COMPLEX_TYPE | |
| 183 || TREE_CODE (TREE_TYPE (old_arg)) == VECTOR_TYPE) | |
| 184 DECL_GIMPLE_REG_P (new_var) = 1; | |
| 185 gcc_assert (is_gimple_reg (new_var)); | |
| 186 add_referenced_var (new_var); | |
| 187 new_var = make_ssa_name (new_var, tmp); | |
| 188 gimple_assign_set_lhs (tmp, new_var); | |
| 189 | |
| 190 gsi_insert_on_edge (e, tmp); | |
| 191 | |
| 192 update_stmt (tmp); | |
| 193 mark_symbols_for_renaming (tmp); | |
| 194 } | |
| 195 | |
| 196 add_phi_arg (new_phi, new_var, e); | |
| 197 } | |
| 198 | |
| 199 update_stmt (new_phi); | |
| 200 | |
| 201 return res; | |
| 202 } | |
| 203 | |
| 204 /* Propagate between the phi node arguments of PHI in BB and phi result | |
| 205 users. For now this matches | |
| 206 # p_2 = PHI <&x, &y> | |
| 207 <Lx>:; | |
| 208 p_3 = p_2; | |
| 209 z_2 = *p_3; | |
| 210 and converts it to | |
| 211 # z_2 = PHI <x, y> | |
| 212 <Lx>:; | |
| 213 Returns true if a transformation was done and edge insertions | |
| 214 need to be committed. Global data PHIVN and N is used to track | |
| 215 past transformation results. We need to be especially careful here | |
| 216 with aliasing issues as we are moving memory reads. */ | |
| 217 | |
| 218 static bool | |
| 219 propagate_with_phi (basic_block bb, gimple phi, struct phiprop_d *phivn, | |
| 220 size_t n) | |
| 221 { | |
| 222 tree ptr = PHI_RESULT (phi); | |
| 223 gimple use_stmt; | |
| 224 tree res = NULL_TREE; | |
| 225 gimple_stmt_iterator gsi; | |
| 226 imm_use_iterator ui; | |
| 227 use_operand_p arg_p, use; | |
| 228 ssa_op_iter i; | |
| 229 bool phi_inserted; | |
| 230 | |
| 231 if (MTAG_P (SSA_NAME_VAR (ptr)) | |
| 232 || !POINTER_TYPE_P (TREE_TYPE (ptr)) | |
| 233 || !is_gimple_reg_type (TREE_TYPE (TREE_TYPE (ptr)))) | |
| 234 return false; | |
| 235 | |
| 236 /* Check if we can "cheaply" dereference all phi arguments. */ | |
| 237 FOR_EACH_PHI_ARG (arg_p, phi, i, SSA_OP_USE) | |
| 238 { | |
| 239 tree arg = USE_FROM_PTR (arg_p); | |
| 240 /* Walk the ssa chain until we reach a ssa name we already | |
| 241 created a value for or we reach a definition of the form | |
| 242 ssa_name_n = &var; */ | |
| 243 while (TREE_CODE (arg) == SSA_NAME | |
| 244 && !SSA_NAME_IS_DEFAULT_DEF (arg) | |
| 245 && (SSA_NAME_VERSION (arg) >= n | |
| 246 || phivn[SSA_NAME_VERSION (arg)].value == NULL_TREE)) | |
| 247 { | |
| 248 gimple def_stmt = SSA_NAME_DEF_STMT (arg); | |
| 249 if (!gimple_assign_single_p (def_stmt)) | |
| 250 return false; | |
| 251 arg = gimple_assign_rhs1 (def_stmt); | |
| 252 } | |
| 253 if ((TREE_CODE (arg) != ADDR_EXPR | |
| 254 /* Avoid to have to decay *&a to a[0] later. */ | |
| 255 || !is_gimple_reg_type (TREE_TYPE (TREE_OPERAND (arg, 0)))) | |
| 256 && !(TREE_CODE (arg) == SSA_NAME | |
| 257 && phivn[SSA_NAME_VERSION (arg)].value != NULL_TREE | |
| 258 && phivn_valid_p (phivn, arg, bb))) | |
| 259 return false; | |
| 260 } | |
| 261 | |
| 262 /* Find a dereferencing use. First follow (single use) ssa | |
| 263 copy chains for ptr. */ | |
| 264 while (single_imm_use (ptr, &use, &use_stmt) | |
| 265 && gimple_assign_ssa_name_copy_p (use_stmt)) | |
| 266 ptr = gimple_assign_lhs (use_stmt); | |
| 267 | |
| 268 /* Replace the first dereference of *ptr if there is one and if we | |
| 269 can move the loads to the place of the ptr phi node. */ | |
| 270 phi_inserted = false; | |
| 271 FOR_EACH_IMM_USE_STMT (use_stmt, ui, ptr) | |
| 272 { | |
| 273 ssa_op_iter ui2; | |
| 274 tree vuse; | |
| 275 | |
| 276 /* Check whether this is a load of *ptr. */ | |
| 277 if (!(is_gimple_assign (use_stmt) | |
| 278 && TREE_CODE (gimple_assign_lhs (use_stmt)) == SSA_NAME | |
| 279 && gimple_assign_rhs_code (use_stmt) == INDIRECT_REF | |
| 280 && TREE_OPERAND (gimple_assign_rhs1 (use_stmt), 0) == ptr | |
| 281 /* We cannot replace a load that may throw or is volatile. */ | |
| 282 && !stmt_can_throw_internal (use_stmt))) | |
| 283 continue; | |
| 284 | |
| 285 /* Check if we can move the loads. The def stmts of all virtual uses | |
| 286 need to be post-dominated by bb. */ | |
| 287 FOR_EACH_SSA_TREE_OPERAND (vuse, use_stmt, ui2, SSA_OP_VUSE) | |
| 288 { | |
| 289 gimple def_stmt = SSA_NAME_DEF_STMT (vuse); | |
| 290 if (!SSA_NAME_IS_DEFAULT_DEF (vuse) | |
| 291 && (gimple_bb (def_stmt) == bb | |
| 292 || !dominated_by_p (CDI_DOMINATORS, | |
| 293 bb, gimple_bb (def_stmt)))) | |
| 294 goto next; | |
| 295 } | |
| 296 | |
| 297 /* Found a proper dereference. Insert a phi node if this | |
| 298 is the first load transformation. */ | |
| 299 if (!phi_inserted) | |
| 300 { | |
| 301 res = phiprop_insert_phi (bb, phi, use_stmt, phivn, n); | |
| 302 | |
| 303 /* Remember the value we created for *ptr. */ | |
| 304 phivn[SSA_NAME_VERSION (ptr)].value = res; | |
| 305 phivn[SSA_NAME_VERSION (ptr)].vop_stmt = use_stmt; | |
| 306 | |
| 307 /* Remove old stmt. The phi is taken care of by DCE, if we | |
| 308 want to delete it here we also have to delete all intermediate | |
| 309 copies. */ | |
| 310 gsi = gsi_for_stmt (use_stmt); | |
| 311 gsi_remove (&gsi, false); | |
| 312 | |
| 313 phi_inserted = true; | |
| 314 } | |
| 315 else | |
| 316 { | |
| 317 /* Further replacements are easy, just make a copy out of the | |
| 318 load. */ | |
| 319 gimple_assign_set_rhs1 (use_stmt, res); | |
| 320 update_stmt (use_stmt); | |
| 321 } | |
| 322 | |
| 323 next:; | |
| 324 /* Continue searching for a proper dereference. */ | |
| 325 } | |
| 326 | |
| 327 return phi_inserted; | |
| 328 } | |
| 329 | |
| 330 /* Helper walking the dominator tree starting from BB and processing | |
| 331 phi nodes with global data PHIVN and N. */ | |
| 332 | |
| 333 static bool | |
| 334 tree_ssa_phiprop_1 (basic_block bb, struct phiprop_d *phivn, size_t n) | |
| 335 { | |
| 336 bool did_something = false; | |
| 337 basic_block son; | |
| 338 gimple_stmt_iterator gsi; | |
| 339 | |
| 340 for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) | |
| 341 did_something |= propagate_with_phi (bb, gsi_stmt (gsi), phivn, n); | |
| 342 | |
| 343 for (son = first_dom_son (CDI_DOMINATORS, bb); | |
| 344 son; | |
| 345 son = next_dom_son (CDI_DOMINATORS, son)) | |
| 346 did_something |= tree_ssa_phiprop_1 (son, phivn, n); | |
| 347 | |
| 348 return did_something; | |
| 349 } | |
| 350 | |
| 351 /* Main entry for phiprop pass. */ | |
| 352 | |
| 353 static unsigned int | |
| 354 tree_ssa_phiprop (void) | |
| 355 { | |
| 356 struct phiprop_d *phivn; | |
| 357 | |
| 358 calculate_dominance_info (CDI_DOMINATORS); | |
| 359 | |
| 360 phivn = XCNEWVEC (struct phiprop_d, num_ssa_names); | |
| 361 | |
| 362 if (tree_ssa_phiprop_1 (ENTRY_BLOCK_PTR, phivn, num_ssa_names)) | |
| 363 gsi_commit_edge_inserts (); | |
| 364 | |
| 365 free (phivn); | |
| 366 | |
| 367 return 0; | |
| 368 } | |
| 369 | |
| 370 static bool | |
| 371 gate_phiprop (void) | |
| 372 { | |
| 373 return 1; | |
| 374 } | |
| 375 | |
| 376 struct gimple_opt_pass pass_phiprop = | |
| 377 { | |
| 378 { | |
| 379 GIMPLE_PASS, | |
| 380 "phiprop", /* name */ | |
| 381 gate_phiprop, /* gate */ | |
| 382 tree_ssa_phiprop, /* execute */ | |
| 383 NULL, /* sub */ | |
| 384 NULL, /* next */ | |
| 385 0, /* static_pass_number */ | |
| 386 TV_TREE_PHIPROP, /* tv_id */ | |
| 387 PROP_cfg | PROP_ssa, /* properties_required */ | |
| 388 0, /* properties_provided */ | |
| 389 0, /* properties_destroyed */ | |
| 390 0, /* todo_flags_start */ | |
| 391 TODO_dump_func | |
| 392 | TODO_ggc_collect | |
| 393 | TODO_update_ssa | |
| 394 | TODO_verify_ssa /* todo_flags_finish */ | |
| 395 } | |
| 396 }; |